Weather and Climate GCMs A MEMOIR

Weather and Climate GCMs: A MEMOIR K MIYAKODA George Mason University / COLA 4041 Powder Mill Rd., Suite 302 Calverton MD 20705 USA Introduction If one were to ask meteorologists whether long-range forecasts are possible, the answer would be sometimes “yes”, for example, in the case of El Niño 1997/98, but often “no” If the same question were asked in the 1970’s, the answer would have been mostly “no” Nevertheless, offices of “long-range forecasts” have managed to conduct business in many countries This indicates that people have sensed the possibility and utility of these forecasts Long-range weather forecasts have now been recognized as a reasonable enterprise It is indeed a useful effort to explore the knowledge and techniques for making long-range forecasts, in particular, using general circulation models (GCM) The United States is an ideal place to observe the historical events of research activities, including GCM weather forecasts I came to the U.S in 1961, and settled down as an imigrant in 1965 In particular, my laboratory was the Geophysical Fluid Dynamics Laboratory (GFDL), located at Princeton Smagorinsky was a unique and innovative director, who studied numerical weather prediction in its early stage at the Institute of Advanced Study (IAS) at Princeton under Charney Therefore, my office was a superb observation deck to watch progress in GCM activities From the beginning, there have been two types of GCMs: Weather model ( e.g., Charney et al 1950) and Climate model (e.g Phillips 1956) By definition, the Weather GCM is used to produce operational forecasts, while the Climate GCM serves as a tool with which scientists investigate fundamental processes I always felt that the former tends to have a narrow objective, while the latter tends to embrace wide targets Bengtsson often mentioned that GCMs tend to become more precise and accurate if they are used for practical forecasts On the other hand, if GCMs were not exposed to an academic environment, they would not expand their utility and would lose flexibility This essay is my recollection The papers related to Weather GCMs quoted here are basically restricted to the ones prior to 1982, except other memoirs or historical descriptions The year 1982 is the starting point of the World Meteorological Organization (WMO) project on long-range forecasts (see WMO 1982) The outstanding 1982/83 El Niño occurred just after this meeting Climate GCMs have not been my research subject, but I worked at GFDL for 30 years, observing the climate research of my colleagues Phillips’ GCM experiment The starting point of GCM long-range forecasts is the research of Phillips (1956), which took place before I emigrated, but I read his paper as a student in Tokyo Smagorinsky (1983) characterized this study as “a monumental experiment”, and he wrote that a new era had been opened by this experiment Phillips (1956) built a two layer quasigeostrophic atmospheric model and carried out a 31 day run of this model This is the first GCM run in history, and it was done at IAS using the first automatic computer The model’s domain was hemispheric between a pole and the equator, and the eastwest extension was chosen sufficiently large to accommodate one large baroclinic wave with periodic lateral boundary conditions at both ends The grid sizes were: x=375 km and y=625 km, and the west to east domain corresponded to 16 x Net radiation and latent heat processes were empirically specified by a heating function Phillips started his integration with an isothermal atmosphere at rest and ran the model with a time step t=1day The net heating gradually built up a latitudinal temperature gradient At this stage, the meridional circulation consisted of a single weak direct cell In the second stage, a random number was introduced to give rise to a perturbation in the geopotential field The time step was then hour Consequently disturbances of wavelength of ~ 6000 km were produced, and the flow patterns tilted westward with height, the wave moving eastward Meanwhile, horizontal transport of zonal momentum was directed toward the mid-latitudes, creating a jet of 80 m s -1 at the 250 mb level The three-cell structure emerged between the equator and the pole Phillips analyzed the result and recognized that the solutions appear to reflect the observational evidence about the atmospheric general circulation The baroclinic instability theory, which had been established before 1956, is in a linear framework, and therefore, it is difficult to prove its validity with observations Now Phillips’ experiment mimiced nature so well that the non-linearity was included ,and therefore, it was possible to investigate the connection between nature’s complexity and the linear theories The experiment indicated that unstable baroclinic waves are generated when the vertical wind shear of the basic flow reaches a critical value, as is expected The disturbances transport heat in the expected direction The secondary effect is to transport momentum in such a way as to maintain the jet against frictional dissipation, and thus the westeries are established in the middle latitudes All these results completely agree with what the general circulation theory had postulated As Lewis (1998) documented, this was the first breakthrough in research on climatology Charney mentioned (Platzman 1990) that this was one of three remarkable achievements in the IAS at Princeton, others being the first implementation of a computer for numerical weather prediction, and the realization of cyclone development with a 2-1/2 level model It was surprising that Phillips was successful in running the model without any serious computational instability for such a long time The major reason is that he treated relatively mild weather, and the solutions reached a realistic state after 30 days, He couldn’t continue too long because truncation errors continued to develop and certain instabilities finally destroyed the calculation Numerical integration of GCMs a Finite difference method The period from 1955 to 1963 represents the struggle of unraveling the cause of computational instability and searching for techniques to obtain stable calculation For example, I presented a paper at the first international conference on numerical weather prediction in Tokyo, the paper entitled “500 hour forecasts” (Miyakoda 1960—not 500 Fig Evolution of a square checkerboard embedded in the westerlies of the atmosphere The checkerboard is deformed by the flow and stretched to a filament When the filament becomes too thin, and the grid cannot resolve the filament any more, a numerical instability occurs A number of filaments emerge in parallel to the original one The feature is called the “Spaghetti pattern” (After Welander - see Rossby 1959) -days) (Fig 1) The issue was how to reduce the truncation error, because it was thought essential to obtain an accurate solution for a long run This objective turns out to be wrong The question is, which is preferred: an accurate solution without stability, or a less accurate solution with stability Arakawa (1966) presented a method to obtain a stable solution by using the socalled Arakawa Jacobian This was really a breakthrough for long time integration of the barotropic vorticity equation The principle is simple Energy and enstrophy (squared vorticity) are conserved within the framework of the finite difference equations These two squared quantities can be conserved for all time In other words, the integration of the equation is computationally stable, because two quantities are bounded, and therefore, any quantity does not go to infinity This method was applied to the two-level GCM of the University of California at Los Angels (UCLA), which was referred to as the Mintz-Arakawa model Now GCMs could be integrated as long as desired As mentioned earlier, I was obsessed by the notion of accurate numerical solution In fact, accuracy versus stability was a controversial issue among the applied mathematicians If one approximates a differential Jacobian using finite differences, the resulting formula consists of the main term and the remaining terms of higher order The question is whether the remaining terms should be ignored The Arakawa approach is to prevent production of spurious energy and enstrophy first, and if so desired, the order of accuracy is made higher In those days, I had the impression that mathematicians at the Courant Institute, New York University, were critical of the Arakawa Jacobian, or at best not enthusiastic In fact, the famous text book of Richtmeyer and Morton (1967) did not include the Arakawa Jacobian at all For example, the Lax-Wendroff method (1960) (Courant Institute) lets the remaining term serve as a damping term Sometimes this term appears as a “non-linear viscosity”, and it becomes large, when the deformation of the flow pattern is large Stimulated by the idea of the Arakawa Jacobian, Bryan (1966) at GFDL developed a scheme which conserves a squared quantity Different from the Arakawa scheme, only one quantity is conserved, as opposed to two quantities such as kinetic energy and enstrophy with the application of non-linear viscosity Conservation of one quantity is sufficient from the standpoint of computational stability The GCMs at GFDL ran with this scheme ( see Smagorinsky et al 1965; Manabe et al 1965) The scheme was also applied efficiently to an irregular grid ( Kurihara and Holloway 1967) The Arakawa Jacobian is an excellent scheme, because the solution is not only stable but the resulting patterns are noise-free, compared with, for example, Bryan’s scheme However, the Arakawa scheme is only applicable to the case in which  the advection term is of Jacobian form In other words, the advective velocity V is divided into two components by the Helmholtz theorem, i.e., the rotational component, k  ,  and the divergent component,  ; if then V is represented only by k  , then the Jacobian scheme can be utilized Therefore, a three-dimensional problem needs an extended Arakawa Jacobian Arakawa and Lamb (1981) achieved both an energy and potential enstrophy conservation scheme for the general flow, and applied it to the three diemensional UCLA model (Figs.2 and 3) In Yugoslavia, Mesinger and Janjic (see Mesinger and Arakawa 1976) developed a similar but different scheme Their scheme conserves energy and potential enstrophy, but the potential enstrophy conservation only holds with the -component, not with  and  together The finite difference alogorithm had now become very sophisticated and complicated, so it became more difficult for graduate students, for example, to follow this path without deep involvement Fig Arakawa C-grid (u, v) is the flow vector; h is the depth of the fluid; q is the 1 potential absolute vorticity, q (  f )h ;  and f are the vorticity and Coriolis parameter Fig Solutions of the shallow water equations over an steep mountain as represented by flow vectors and streamlines (upper) by the simpler scheme, i.e., energy and potential enstrophy conserving with only purely horizontal non-divergent flow, and (lower) by the new method, i.e., conserving with general divergent flow (after Arakawa and Lamb 1981) -b Spectral method We now turn to the spectral method The Fourier method can guarantee the conservation of kinetic energy and enstrophy For the global atmosphere, the spherical harmonic functions are more appropriate than Fourier functions (Fig 4) In fact, it is another merit for the spherical harmonic method that the treatment at the poles is straightforward; for example, the “polar filtering” method used in the finite difference scheme for increasing the time step is not needed The activity along this line has been Y mn Pmn e im :longitude  :latitude  cos  Fig Spherical harmonic functions, Y mn ( ,  ) (right) Legendre function, P mn going on since the end of 1950’s (Silberman 1954; Platzman 1960; Kubota 1960; Baer and Platzman 1961) The spectral method is quite suitable for an atmospheric model, compared with oceanic models, because the atmosphere has no lateral boundaries A problem with spectral methods is the representation of discontinuous fields, for example, the distribution of rainfall (Robert 1968) If you apply the Fourier transform to a delta-function, the resulting distribution shows a number of ripples around the main rainfall region, which is called the “Gibbs Phenomena” The reason is that any finite number of terms in a Fourier series is not sufficient to resolve the rainfall profile In this case, a finite difference scheme may have a slight advantage, because although it produces severe truncation error, the resulting pattern is not so bad, compared with the Fourier method Finite- difference-oriented people are concerned about the fact that the wave produced by local rainfall is spread over the whole world instantly, because of the modal nature of the basis functions The real problem in the spectral method is, however, the treatment of non-linear terms, which are products of two or more variables A product of two variables is reduced to two terms of different wave numbers For this reason, the scheme which has been discussed so far is referred to as the “Interaction Coefficient method” Orszag (1970) and Eliasen et al (1970) developed a new method, which simplifies the nonlinear calculation i.e, the “Transform method” (see also Machenhauer 1979) In this method, the mathematical process is switched flexibly between the spectral and the grid calculation, depending upon which is convenient For example, the horizontal advection term in the x-coordinate consists of two variables, i.e., A u and B  x , where u is the speed of the advective flow and  is the vorticity In the Transform method, A B is obtained at grid points, and this set of values is decomposed into Fourier series Bourke, a brand new nuclear physicist in Melbourne, Australia, went to Montreal in 1969, and started to work on the application of the Transform method to a shallow water spherical model under the advice of Robert Different from the approach of Orszag, the basic dependent variables are vorticity,  , and divergence, D (u and v are the so-called pseudo scalars and are not appropriate for the expansion with the spherical harmonics-Robert 1966) I met Bourke at Princeton in 1971 He asked me my opinion on his work, and I encouraged him to continue it Looking back, he had already gone quite far at that time Thus, the shallow water equation model was first constructed by Bourke (1972) This GCM was subsequently distributed to a number of groups around the world Each group which received it constructed its own baroclinic spectral model within 2~4 years For example, the Bureau of Meteorology in Australia did so in 1974, GFDL in 1974, University of Reading in 1975, and the Prediction Unit in Canada in 1976 The Australian and Canadian bureaus of meteorology implemented operational numercal weather prediction systems based on the transform method in early 1976 McAvaney et al (1978), an Australian research group, conducted a pioneering GCM integration utilizing the spectral method and semi-implicit time integration, implying that this method is indeed inexpensive The subsequent development of the atmospheric GCM is relatively straightforward, except the semi-Lagrangian method, as well be described shortly The major efforts of GCM development are more directed to the development of physics The semi-Lagrangian method (Robert 1982; Bates and McDonald 1982) has brought a dramatic change in computational aspect at the European Centre for Medium-Range Weather Forecasts (ECMWF) The model was constructed by a substantial contribution of Montreal scientist, Ritchie ( see the story of Staniforth 1997) The advection terms are replaced by the Lagrangian transport, resulting in no more computational restriction on the time step, t, in the sense of the Courant-Friedrich-Levy restriction This method also permits the same framework for the treatment of advection in all three dimensions ( as opposed to doing a grid calculation in the vertical and a spectral calculation horizontally); no more Gaussian grid restriction for the latitudinal direction; and no concern about aliasing error As a result, a drastic reduction of grid-points near the poles is possible With these arrangements, it is no more certain whether the computational scheme is the spectral or the finite difference version On the other hand, it becomes rather difficult for small research groups to use the Lagrangian model, because the overhead time for model construction is considerable Proliferation of this method is not as easy as that of the spectral method in 1972~76 It is an open question, how many groups among research institutes will go to the semiLagrangian method for all variables, i.e., the wind vectors, u, v,, the temperature, T, and the moisture, q In 1982, Robert called me from Montreal, suggesting for us to use it, and I declined the offer In 1998, ECMWF and Canadian Meteorological Centre are the only operational centers which use this method., together with a small model in Irish Meteorological Service Despite the Lagrangian principle, the conservation of advectived quantities has not been guaranteed Namely the water vapor advected, for example, is not positive definite so far Recently , however, Machenhauer (1997) has developed a new scheme by which the mass, enthalpy and momentum are conserved In the future, operational centers will continue to refine the resolution, and therefore, they will use the semi-Lagrangian methods c Validity of GCM solutions Finally I point out my old concern about the accuracy of the GCM solution As was mentioned earlier, the GCM calculation produces a large amount of truncation error The GCM solution is nothing but truncation error after, say, five days If true, is the GCM solution insignificant, and therefore, invalid ? If the problem is steady state, such as the flow pattern around an airplane’s wing, the solution is significant However, there are problems with the case of long-range forecasts and climate simulation Our wish and belief are that the whole solutions of GCM, including the truncation error, are determined by the governing physics and dynamics of the GCM, and therefore, they should be significant Besides, it is a common practice to produce multiple realizations of GCM integration by changing the initial condition and averaging the ensemble of solutions (Leith 1974) Nonlinear viscosity a Smagorinsky’s non-linear viscosity In the previous section, the “non-linear viscosity” was mentioned Smagorinsky (1963) applied this scheme to his GCM When I joined GFDL, this scheme came to my notice However, if you read his paper, you cannot find the derivation of this scheme anywhere I borrowed his personal notes, and made a copy of them After his retirement, he was Fig An example of non-linear viscosity, represented by the horizontal diffusion terms in an ocean GCM (Rosati and Miyakoda 1989) The grid size is 1/3 in the meridional direction and 10 in the zonal direction within the equatorial belt between 10 N and 100 S, and 10 x 10 outside of 100 equatorial belt The “non-liner viscosity is proportional to ( def ) and ( s) , and this figure indicates that the first term is dominant invited by a group of turbulence experts to talk about his updated view of subgridscale eddy viscosity ( Smagorinsky 1993) The formula is such that the coefficient of this viscosity is assumed to be proportional to the resolvable velocity deformation, and the final result is that the eddy viscosity is proportional to the square of the grid-size, ( s) (Fig 5) Before 1963, Lilly was a member of GFDL He appeared to be appreciably impressed by this work After he moved to the National Center of Atmospheric Research (NCAR) in Colorado, he continued this work In GFDL, this scheme had been used in the GCM until a switch to the spectral method b Turbulence closure scheme In the town of Princeton, there were several scientists who were working on turbulence theories in various research facilities, for example, Mellor, Donaldson, Lewellen, Herring, etc Besides, Pennsylvania State University is not far away from Princeton, where similar activities were going on ( for example, Panofsky, Tennekes, Lumley and Wyngaard) It is not surprising, therefore, that the second-order turbulence closure model was derived by Mellor (1973) and Mellor and Yamada (1974), based on the closure assumptions of Rotta and Kolmogorov Mellor is a unique, independent and bright professor at Princeton University, who was involved in models and experiments on a neutral, rotationless turbulent boundary layer (Mellor 1985) On the other hand, Lilly continued his work in NCAR, extending the treatment to three-dimensional turbulence, and later presented a paper, which shows that Smagorinsky’s formulation is exactly what is needed to cascade resolvable-scale turbulence energy to the scale of the inertial subrange (Lilly 1967) In the group of Lilly, Deardorff worked mainly on boundary layer turbulence He also published his turbulence theory (Deardorff 1973) Ironically the latter is the direct descendant of Smagorinsky’s or can be traced back even to von Neumann and Richtmeyer Yet the equations derived by Mellor in Princeton and by Deardorff in Colorado are very similar to each other, except that the characteristic parameters for the closure assumption are different I documented these theories side by side in a German journal (Miyakoda and Sirutis 1977) The conceptual difference in the turbulence treatment is the definition of turbulence, i.e., the ensemble average in the former (Princeton), as opposed to the space average in the latter (Colorado) Therefore, Mellor-Yamada use the turbulent length scale, , as the characteristic length scale, while Deardorff uses the grid size,  s As a consequence, Mellor and Herring had to propose an empirical formula for the length scale, , in Mellor’s system These theories are appealing, because the formulation of eddy viscosity in the Earth’s planetary boundary layer agrees with the hypothesis on the nocturnal jet, proposed by Blackadar (1957) The hypothesis stresses the decrease of vertical mixing inside the boundary layer at night, and as a result, the inertial oscillation of wind is not weakened by the vertical mixing, but it remains strong Bonner (1968) mentioned that major wet episodes over the central U.S in summer occur associated with the strong low level nocturnal jet (see also Helfand and Schubert 1995; Paegle et al 1996) The low level jets bring Gulf Coast moisture efficiently into the central continent (see Fig 5, by Mo et al 1997) One of questions is, however, that the large scale moisture transport takes place only in a certain synoptic situation Anyway, if you believe the turbulence closure approach, Smagorinsky’s nonlinear viscosity should be reasonable, though the details remain to be refined, such as the magnitude of coefficients and the balance with some neglected terms Fig (left) Composite of rainfall for (a) wet events Contour interval 1,2,4, and mm day -1 (b) Same as (a) but for dry events Contour interval 0.5, 1, and mm day -1 (right) Composite of the vertical profile of meridional wind at 30 N for (a) wet and (b) dry events Contour interval is m s -1 (after Mo et al 1997) One of the merits of the turbulence closure approach is that the formulation and the coefficients are based on the “similarity paradigm”, and that the coefficients should be determined by universal constants Accordingly, the framework should be applicable equally to the atmosphere as well as the ocean, and even to Jupiter’s atmosphere without changing the values of the constants If a bulk method, as opposed to the turbulence closure method, is to be used for economical reasons, it should be consistent with the original multi-level framework But this is just my personal feeling; in practice, one could be flexible to adjust the method to the observational evidence and efficiency So far as the horizontal eddy coefficients are concerned, the necessity of including the Reynolds eddy term varies, depending on the numerical scheme Whether it is the Arakawa scheme or the Bryan scheme or the spectral approach, the constants vary, depending upon the degree of production of deformation In other words, the magnitude of eddy viscosity in the free atmosphere or ocean is not so large in nature, but the deformation in finite difference calculations requires a large amount of damping For the spectral GCM, therefore, it is a general attitude (or policy) to avoid the nonlinear formula for the horizontal Reynolds term, because of efficiency and no strong reason for the requirement Linear formulae such as  K 14 and  K 4 D are often used, where K1 and K2 are constants c Large Eddy Simulation issued seasonal forecasts A WMO committee on LRF was formed in 1980 with Gilman as the chairman, and I was a member of this group (see WMO 1980) From the standpoint of the GCM, the technical capability has proceeded steadily, as described above, but the predictability limit has always bothered us Coughlan, who was a member of the group from Australia, presented a brief report on some success of monthly and seasonal forecasts, referring to a review written by Nicholls (1980) LRF in Australia was a most realistic business, because of the direct influence of El Niño Therefore, their experience has been the driving force of the LRF committee In other words, the long-range evolution of ocean and atmosphere related to El Niño is a most certain scenario for LRF c Development of El Niño related LRF Historically speaking, the concept has emerged gradually through various routes I will describe this evolution related to GCM issues, dividing my memory of the recent scientific development before 1982 into nine routes (i) The idea of the Southern Oscillation was proposed by Walker (1924), and thereafter, many scientists who are mostly from the Southern Hemisphere, contributed to this concept, i.e., Berlage (1957) (Indonesia), Troup (1965) (Australia), Trenberth (1975) (New Zealand), Barnett (1977) (U.S.), and van Loon and Madden (1981) (South Africa and U.S.) They investigated the meteorological activities in the equatorial and South Pacific as well as the Indian Ocean There are distinct Southern Oscillation signatures (ii) An El Niño-extratropics connection was inferred by Bjerknes (1961; 1969) and Rowntree (1972), The first time I heard about El Niño from Bjerknes himself in 1967 Since then, it has been one of my group’s subjects In 1972, Smagorinsky introduced me to Bowen, a scientifc attache from Australia to the U.S., who talked, in my office, about his own papers on El Niño (I don’t remember these papers) A strong El Niño occurred in 1973 A student at Princeton University took this subject as his thesis topic, but his research did not impress the faculty at all (iii) The 1972/73 El Niño gave a considerable stimulation to meteorologists and oceanographers Several papers on this event were immediately published Thereafter, excellent and intriguing observational studies were carried out (Barnett 1977; 1981)3, leading eventually to the dynamic theories of this phenomenon (iv) Wyrtki (1975) and Wyrtki et al (1976) proposed a hypothesis on the mechanism of El Niño from an oceanographic standpoint Stimulated by these works, Hurlburt et al (1976), McCreary (1976), Busalacchi and O’Brien (1981) and Philander (1981) performed oceanographic experiments separately, using simple oceanographic models under specified surface wind stress They reached the conclusion that the relaxation of trade winds causes the high sea surface temperature in the central and eastern equatorial Pacific (v) Prior to this or in parallel to it, meteorological studies were also carried out by Matsuno (1966)4 They depicted the structure of wind and atmospheric pressure anomalies under a local ocean heating along the equator, and this pattern is symmetrical Julian and Chervin (1978), Horel and Wallace (1981), Keshavamurty (1982), and Webster (1982) Wyrtki (1973); Wooster and Guillen (1979); Quinn (1974); Ramage (1975); Miller and Laurs (1975) Egger et al (1981); Newell et al (1982); Pazan and Meyers (1982); Weare (1982) Webster (1972), Gill (1980) and Zebiak (1982) around equator, reflecting the effects of Kelvin and Rossby waves Gill (1982) wrote an excellent textbook, which includes also the oceanic dynamics (vi) The oceanic Rossby and Kelvin wave propagation is normally difficult to detect from observations, but there were some works along this line in association with El Niño (Enfield and Allen 1980; White et al 1980; and Chelton and Davis 1982) In this way, the time was almost ripe for a comprehensive El Niño model of airsea coupling to emerge (vii) One of the most important papers was submitted by Rasmusson and Carpenter (1982) They showed composite maps of wind and SST, based on ship observations for various stages of El Niño evolution (viii) According to the hypothesis of Horel and Wallace (1981), heating due to tropical precipitation, arising as a result of equatorial Pacific SST anomalies, acts as a source of anomalous forcing This excites an atmospheric Rossby wavetrain (Hoskins and Karoly 1981), which propagates into higher latitudes along a roughly great circle ray path (ix) From the standpoint of LRF, propagation alone is not sufficient Predictability is an important aspect In fact, high potential predictability was speculated in the tropics rather than in the extratropics, but the tropical disturbances such as easterly waves, tropical depressions, etc are potential elements to disturb the El Niño signals, preventing accurate LRF for the extratropics Concerning this problem, Shukla proposed a scenario; this goes as follows Charney and Shukla (1981) suggested that since the large scale monsoon circulation is dynamically stable and since the lower boundary conditions exert significant influence on the time averaged monsoon flow, the monsoon circulation must be potentially predictable Shukla (1984) speculated further, based on his numerical GCM experiment, that, although the disturbances are less predictable, the equilibration of their amplitudes is quite rapid, and the upscale-cascade process (small to large eddies) is weak, due to low rotational effect of the Earth In other words, interaction of large-scale overturnings with the tropical disturbances is not strong enough to detract from the predictability of the planetary scale circulation d Outstanding El Niños The WMO committee planned a large meeting on LRF at Princeton (WMO 1982) I was assigned to co-chair with Kurbatkin, of the Soviet Union Several recommendations were submitted as the consensus of participants Highest priority was assigned, first to the improvement of atmospheric GCMs, and second to the development of air-sea-land coupled GCMs As described earlier, the 1972/73 event first awakened meteorologists and oceanographers to investigate El Niño With this preparation, the 1982/83 El Niño created a great deal of enthusiasm toward understanding of the phenomena Then the 1997/98 El Niño came, which was associated with the warm SST (comparable to that for 1982/83) over the eastern Equatorial Pacific, lasting for longest period ever and bringing Fig 10 SST anomalies for January 1998 at the outstanding El Niño Contour interval is 10 C (after NCEP report) a warm winter to the eastern U.S and heavy rains and mudslides to the western U.S Fig 10 is a snap shot of the SST, which reveals the “horseshoe” pattern over the Pacific Ocean, extending to the Indian Ocean In order to utilize the information of El Niño for the forecasts of middle latitudes, it is prerequisite for a GCM to have good teleconnection capability from the equatorial Pacific to the U.S D Straus at COLA (Center for Ocean-Land-Atmosphere Studies) ( personal communication) investigated the results for different GCMs In this comparison, the GCMs of COLA, CPC ( Climate Prediction Center), NCEP (National Center for Environmental Prediction) and NCAR were used Each group carried out weather simulations for three months, specifying the observed SST over the globe The forecasts were done for about 15 winters from 1982 to 1997 The ensemble sizes are different for each group, ranging from to 10 Straus performed the SVD (Singular Value Decomposition) analysis, using winter mean SST on one side and 500 hPa anomalies of analyzed geopotential height on the other side He then regressed the time Fig 11 500 hPa geopotential height variances, which are explained by tropical SST in terms of SVD analysis GCM simulations of groups, i.e., COLA, CPC, NCEP, and NCAR are presented The pattern in the middle is the NCEP Re-analysis, which is regarded as the reference Contours represent the percentage (After Straus 1998) series of simulated seasonal mean height anomalies for each GCM on the time series of the first SVD mode Thus he obtained the variance patterns for GCMs (Fig 11) The transmission of the El Niño effect from the equatorial Pacific to the mid-latitudes turns out to be so delicate that various atmospheric GCMs gave different solutions In other words, the subgrid-scale physics in Weather GCMs influence the simulation of teleconnections This figure indicates a very important point; that is, practically accurate Weather GCMs are needed for obtaining El Niño forecasts At this stage, it is not clear why they are so different Future issues of GCM forecasts My memoir concerning EL Niño forecasts is finished In 1983, the new terminology, ENSO (El Niño/ Southern Oscillation), was proposed So far this name has been used only in the scientific community (not the news media) Philander (1990) proposed a name, La Niña, for the cold episode Meanwhile, the modellers were stimulated to develop air-sea coupled models This time, oceanographers were more active than meteorologists in using GCMs and investigating EL Niño phenomena For example, Cane and Zebiak (1986) were successful in building a simple coupled model and making predictions, though their model is too simple to be classified in a GCM Schopf and Suarez (1988) achieved generating EL Niño processes with a coupled GCM, and analyzed the results, proposed a theory of the “delayed oscillator” mechanism for the EL Niño / La Niña oscillation For this time-scale, the oceanic part sets the slow part of the processes, and the atmospheric part acts as a quick linear response Sensitivity studies of CO2 described in section have now gained overwhelming support by the public The IPCC (International Panel of Climate Change) has issued every year a projection of the global trend of the atmosphere temperature related to the scenario of increasing CO2 and aerosols, which has been calculated by several GCMs around the world Associated with this report, one issue is that the GCM projection of IPCC has been based on a number of caviats; for example, the GCM runs lack of proper ENSO simulations, and use “flux correction”, and include the ambiguity of aerosols estimate What can be done about this problem ? One thing we can is the stepwise extension of forecast range and the confirmation of the realizability of GCM simulation for all time-scale variations How far ahead people wish to know forecasts except the CO issue ? My view is that people would not care too much for the forecasts beyond El Niño, because the ambiguity of forecasts is so large However, they may care about the IPCC report i) Interannual variation The periodicity of ENSO is about years with the warm phase, El Niño, and the cold phase, La Niña, at both extrema It is known that ENSO is connected with the Asian and Australian monsoons In order to unravel the mechanism of these teleconnection phenomena, a coupled ocean-atmosphere GCM is needed, in which the ocean GCM described as the first category in section 5, is utilized Of course, they already exist, but they should be refined, so that the ENSO simulation is more accurate and the simulation of various monsoons should be correct as well, because these monsoons are very likely to be in the relation of cousin with El Nio; the trigger could be common for both monsoons and El Niño The oscillation is not regular, which is one of the key aspects for this phenomenon If the time variation is made clear, the knowledge would contribute appreciably to more reliable El Niño forecasts as well ii) Interdecadal variations Kachi and Nitta (1997) studied the interannual as well as interdecadal variations Fig 12 EOF for the decadal component of the tropical ocean SST between 30 0S and 300N This mode can account for 37.14 % of the total variance of the decadal component (top) the distribution of SST; contour interval is 0.2 C, and (bottom) time series of the coefficients (After Kachi and Nitta 1997) - Fig 13 Five-year running mean of the amplitude of North Pacific January SST EOF 1,and PNA index from 700 mb height Broken line is the linear trend of each variable (After Namias et al 1988) in the real global atmosphere and ocean, focusing on SST, sea-level pressure, surface winds, and 500 hPa geopotential height On the interdecadal time-scale, the variation is dominant over the entire Pacific Ocean, as opposed to the equatorial Pacific It is intriguing that this variation exhibits abrupt changes from the late 1970s to the early 1980s (Fig.12); the tendency was originally pointed out by Namias et al (1988) (Fig 13), Nitta and Yamada (1989), and later by Trenberth (1990) Nakamura et al (1997) found that the strongest variability of SST associated with this slow oscillation (> years) is located around the subarctic front in the Pacific at 420N The SST is increasing over the tropical central and eastern Pacific, while it is decreasing in the mid-latitudes of North and South Pacific The winter PNA pattern has been more intense recently, compared to the period before 1970’s According to Nakamura et al., the interdecadal variation of oceanic system over the northern Pacific is preceding independently of the tropical processes In order to simulate this variability, the ocean GCM in the second category is needed There have been some attempts at simulation with an ocean GCM of this category, such as Dukowicz and Smith (1994), but the long term simulation with an airsea coupled GCM is require The resulting ocean flow chart includes the “Conveyer belt” The knowledge of world ocean current will be extraordinarily increased iii) Half century variation Manabe and Stouffer (1988) investigated the result of simulation with a fully coupled atmosphere-ocean climate model, for realistic ocean basin geometry They showed that there is a solution which represents Atlantic overturning and North Atlantic Deep Water formation On the other hand, another solution does not include North Atlantic sinking, as had been predicted by Stommel (1961) Fig 14 shows the surface air temperature difference between the two climatic equilibria in a coupled air-sea model (the state with North Atlantic sinking minus the state without) (see Held 1993) Further study ( Delworth et al 1993) has revealed that Fig 14 Difference in surface air temperature (0C) between the two solutions (After Manabe and Stouffer 1988) this model has irregular oscillations of the thermohaline circulation with a time scale of approximately 50 years The irregular oscillation appears to be driven by density anomalies in the ocean, and is triggered by nearly random surface buoyancy forcing of heat and water fluxes The sea surface temperature fluctuations associated with this variations have a spatial pattern that bears resemblance to a pattern of observed interdecadal variability (Kushnir 1993) Epilogue Epilogue This essay is my recollection of progress and events prior to 1982 However, without the 1997/98 El Niño, confidence in the utility of LRF would not be established Now people on the street know about the existence of LRF, together with El Niño Perhaps, they don’t care whether the LRF is monthly or seasonal forecast, but they are concerned about whether the gradual increase in the intensity of El Niño from 1972/73 to 1997/98 is due to natural variability or due to the “global warming” Perhaps it is too early to say The contents of Climate GCMs have not been my research subject, and yet I worked at GFDL for 30 years, where I observed the climate research of my colleagues, particularly, Manabe, Bryan, Mahlman (middle atmosphere), Holland (ocean), Williams ( planetary atmosphere), Sarmiento (tracer), etc Manabe’s works have been really fantastic He used a variety of methods to stay on the cutting edge: “flux adjustment”, “moist convective adjustment”, “asynchronous integration”, “bucket soil moisture method”,etc The essence of his GCM approach has been simplicity Perhaps this is an important principle for a first generation modeller or model user Acknowledgments: I wish to express my gratitude to Drs Joe Smagorinsky, A Arakawa, and George Mellor, Bill Bourke, S Manabe, Kinse Mo, and Hisashi Nakamura who reviewed this memoir and gave me many valuable suggestions and comments I thank Drs Jim Kinter and Uma Bhatt, COLA, and Drs Phil Mote, Jassim Al-Saadi and Evi Schuepbach, participants in ASI, who checked the logic and structure, and English of this essay I also wish to express my gratitude to Dr David Straus, who kindly showed me his research results References Arakawa, A (1966) Computational design for long-term numerical integration of the equations of fluid motion: two-dimensional incompressible flow Part Comp Phys., 1, 119-143 Arakawa, A and V.R Lamb (1981) A potential enstrophy and energy conserving scheme for the shallow water equation Mon Wea Rev., 109, 18-36 Baer, F and G.W Platzman (1961) A procedure for numerical integration of the spectral vorticity equation J Meteor., 18, 393-401 Barnett, T.P (1977) The principal time and space scales of the Pacific trade-wind field J Atmos Sci., 34, 221-236 Barnett, T.P (1981) Statistical relations between ocean / atmosphere fluctuations in the tropical Pacific J Phys Oceanogr., 11, 1043-1058 Bates,J.R and A McDonald (1982) Multiply-upstream, semi-Lagrangian advective schemes: Analysis and application to a multilevel primitive equation model Mon.Wea Rev., 112, 1831-1842 Berlage, H.P (1957) Fluctuations of the general atmospheric circulation of more than one year, their nature and prognostic value Mededel en Verhamdel, Koninkl Netherlands Meteor Inst No 69, 152pp Bjerknes, J (1961) El Niño study based on analysis of ocean surface temperatures 1935-57 Bull Inter-Amer Trop Tuna Comm., 5, 219-303 Bjerknes, J.( 1969) Atmospheric teleconnections from the equatorial Pacific Mon Wea Rev., 97, 165-172 Blackadar, A.K.(1957) Boundary layer wind maxima and their significance for the growth of nocturnal jet Bull Amer Meteor Soc., 38, 283-290 Blackmon, M.L., M Wallace, N-C Lau, and S.L Mullen (1977) An observational study of the Northern Hemisphere wintertime circulation J Atmos.Sci., 34, 1040 1053 Bonner, W.D (1968) Climatology of the low level jet Mon Wea Rev., 96, 833850 Bourke, W (1972) An efficient, one level, primitive-equations spectral model Mon Wea Rev., 100, 683-689 Brankovic, C and T.N Palmer (1997) Atmospheric seasonal predictability and estimates of ensemble size Mon Wea Rev., 125, 859-874 Bryan, K (1963): A numerical investigsation of a nonlinear model of a winddriven ocean J Atmos Sci., 20, 594-606 Bryan, K (1966) A scheme for numerical integration of the equations of motions on an irregular grid free of non-linear instability Mon Wea Res., 94, 39-40 Busalachi, A.J and J.J O’Brien (1981) Interannual variability of the equatorial Pacific in the 1960’s J Geophys Res., 86, 10901-10907 Cane, A.M and S.E Zebiak (1986) A theory for El Niño-Southern Oscillation Science, 228,1085-1087 Charney, C.G., R Fjortoft, and J von Neumann (1950) Numerical integration of the barotropic vorticity equation Tellus, 1, 38-54 Charney, J.G and J Shukla (1981) Predictability of monsoons Monsoon Dynamics, J.Lighthill and R Pearce, Eds., Cambridge University Press, 735pp Charney, J.G and J.G DeVore (1979) Multiple flow equlibria in the atmosphere and blocking J Atmos Sci., 36, 1205-1216 Chelton, D.B and R.E.Davis (1982) Monthly mean sea-level variability along the west coast of North America J Phys Oceanogr., 12, 754-784 CLIMAP Project Members (1976) The surface of the ice-age Earth Science, 191, 1131-1136 Deardorff, J.W (1970) Convective velocity and temperature scales for the unstable planetary boundary layer and Rayleigh convection J Atmos Sci., 27, 12111213 Deardorff, J.W (1973) The use of subgrid transport equations in a threedimensional model of atmospheric turbulence ASME Publication, 1-10 Delworth, T., S.Manabe, and R.J Stouffer (1993) Interdecadal variations of the thermohaline circulation in a coupled ocean-atmosphere model Climate, 6, 1993-2011 Dickinson, R.E.,(1987) Climate sensitivity Advan In Geophys 28, part A, 99-129 Dukowicz,J.K and R.D Smith (1994) Implicit free-surface method for the Bryan-CoxSemtner model J Gephys Res., 99, No.C4, 7991-8014 Egger, J., G Meyers and P.B Wright (1981) Pressure, wind and cloudiness in the tropical Pacific related to the Southern Oscillation Mon Wea Rev., 109, 1139-1149 Eliasen, E., B Machenhauer and E Rasmussen (1971) On a numerical method for integration of the hydrodynamical equations with a spectral representation of the horizontal fields Tech Rep., Copenhagen University, Denmark, 37pp Enfield, D.B and J.S Allen (1980) On the structure and dynamics of monthly mean sea level anomalies along the Pacific coast of North and South America J Phys Oceanogr., 10, 557-578.34 Gates, W.L (1976) Modeling the ice age climate Science, 191, 1138-1144 Gent, P.R and J.C McWilliams ( 1990) Isopycnal mixing in ocean circulation models J Phys Oceanogr., 20, 150-155 Gill, A.E (1980) Some simple solutions for heat-induced tropical circulation Quart.J.Roy Meteor Soc., 106, 447-462 Gill, A.E (1982) Atmosphere-Ocean Dynamics Academ Press, 662pp Green, J.S.A (1977) The weather during July 1976: some dynamical considerations of the drought Weather, 32, 120-128 Held, I.M (1993) Large-scale dynamics and global warming BAMS, 74, 228-241 Helfand, H.M and S.D Schubert (1995) Climatology of the Great Plains low-level jet and its contribution to the continental moiture budget of the United States J Climate, 8, 784806 Horel, J.D and J.M Wallace (1981) Planetary-scale atmospheric phenomena associated with the interannual variability of sea surface temperature in the equatorial Pacific Mon Wea Rev., 109, 813-829 Hoskins, B.J and D.J Karoly (1981) The steady linear response of a spherical atmosphere to thermal and orographic forcing J Atmos Sci., 38, 1179-1196 Hurlburt, H.E.,J.C Kindle, and J.J O’Brien (1976) A numerical simulation of the onset of El Niño J Phys Oceanogr., 6, 621-631 Julian, P.R and R.M Chervin (1978) A study of the Southern Oscillation and Walker Circulation phenomenon J Atmos Sci., 106, 1433-1451 Kachi, M and T Nitta (1997) Decadal variations of the global atmosphere-ocean system J Meteor Soc Japan, 75, 657-675 Keeling, C.D (1958) The concentration and isotopic abundances of atmospheric carbon dioxide in rural areas Geochemica et Cosmochica Acta, 13, 322-334 Keeling, C.D (1997) A brief history of atmospheric carbon dioxide, measurements and their impact on thoughts about environmental change In: Better Future for the Planet Earth Asahi Glass Foundation 66-83 Keshavamurty, R.N (1982) Response of the atmosphere to sea surface temperature anomalies over the equatorial Pacific and the teleconnections of the Southern Oscillation J Atmos Sci., 39, 1241-1259 Kubota, S (1960) Surface spherical harmonic representation of system of equations for analysis Papers Meteor Geophys 10, 145-166 Kurihara,Y and J.L Holloway (1967) Numerical integration of a nine-level global primitive equations model formulated by the box method Mon Wea Rev., 95, 509530 Kushnir, Y (1993) Interdecadal variations in North Atlantic sea surface temperature and associated atmospheric conditions J Climate, 7, 141-157 Kutzbach, J.E (1985) Modeling of paleoclimates Advance in Geophyss., 28, part A, 159-196 Lax, P and B Wendroff (1960) Systems of conservation laws Communications on Pure and Applied Mathematics, 13, 217-237 Leith, C.E (1974) Theoretical skill of Monte Carlo forecasts Mon Wea Rev., 102, 409-418 Lewis, J.M (1998) Clarifying the dynamics of the general circulation: Phillips’s 1956 experiment Bull.Amer.Meteor.Soc., 79, 39-60 Lilly, D.K (1967) The representation of small-scale turbulence in numerical simulation experiments Proc IBM Sci., Computing Symp Environmental Sci., IBM Form No 320-1951, 195-210 Machenhauer, B (1979) The spectral method Numerical methods used in atmospheric models Vol 11, GARP Publ Series No 17, Sept 1979, pp 121-275 Manabe, S., J Smagorinsky and R.F Strickler (1965) Simulated climatology of a general circulation model with a hydrologic cycle Mon Wea Rev., 93, 769-798 Manabe, S and K Bryan (1969) Climate calculations with a combined ocean-atmosphere model J Atmos Sci., 26, 786-789 Manabe, S., D.G Hahn, and J.L Holloway (1974) The seasonal variation of the tropical circulation as simulated by a global model of the atmosphere J Atmos Sci., 31, 43-83 Manabe, S and R.F Strickler (1964) Thermal equlibrium of the atmosphere with convective adjustment J Atmos Sci., 21, 361-385 Manabe, S and R.T Wetherald (1967) Thermal equlibrium of the atmosphere with a given distribution of relative humidityJ Atmos Sci., 24, 241-259 Manabe, S and R.T Wetherald (1975) The effect of doubling the co2— concentration of the climate of a general circulation model J Atmos Sci., 32, 3-15 Manabe, S and R.T Wetherald (1983) CO2 and hydrology Advance in Geophys., 28, Part A, 131-156 Manabe, S and R.J Stouffer (1988) Two stable equilibriua of a coupled oceanatmosphere model J Climate, 1, 841-866 Matsuno, T (1966) Quasi-geostrophic motions in equatorial areas J Meteor Soc Japan, 2, 25-43 McAvaney, B.J., W.P Bourke, and K.K Puri (1978) A global spectral model for simulation of the general circulation J Atmos Sci., 35, 1557-1583 McCreary, J.P (1976) Eastern tropical ocean response to changing wind systems with application to El Niño J Phys Oceanogr., 6, 632-645 Mellor, G.L (1973) Analytic prediction of the properties of stratified planetary surface layers J Atmos Sci., 30, 1061-1069 Mellor, G.L and T Yamada (1974) A hierachy of turbulence closure models for planetary boundary layers J Atmos Sci., 31, 1791-1806 Mellor, G.L (1985) Ensemble average, turbulence closure Advances in Geophys., 28B, 345-358 Mesinger, F.and A Arakawa (1976) Numerical methods used in atmospheric models, Vol GARP Publication Series No.17, WMO/ICSU Joint Organizing Committee, Geneva, Switzerland, 65pp Miller, F.R and R.M Laurs (1975) The El Niño of 1972-73 in the eastern tropical Pacific Ocean Bull Inter-Amer Trop Tuna Comm., 16, 403-448 Mintz, Y (1965) Very-long-term global integration of the primitive equations of atmosphereric motion: (an experiment in climate simulation) WMO Tech Notes, no 66, pp 141-167; and Amer Meteor Soc., Monograph, 8, no 30., pp 30-36, 1968 Miyakoda, K (1960) A trial of 500 hour barotropic forecast In: Proc Internat Sym In Numer Wea Pred In Tokyo, Nov 7-13, 1960, 221-240 Miyakoda, K and J Sirutis (1985) Extended range forecasting Advances in Geophysics, 28B, 55-85 Miyakoda, K and J Sirutis (1977) Comparative integrations of global models with various parameterized processes of subgrid-scale vertical transports Description of the parameterisations Contrib Atmos Phys., 50, 445-487 Mo, K.C., J.N Paegle, and R.W Higgins (1997) Atmospheric processes associated with summer gloods and droughts in the central United States J Climate , 10, 30283046 Nakamura, H., G Lin, and T Yamagata (1997) Decadal climate variability in the North Pacific during the recent decades Bull Amer Meteor Soc., 78, 2215-2225 Namias, J (1962) Influences of abnormal surface heat sources and sinks on atmospheric behavior In: Proc Intern Sym Numer Wea Predict., Tokyo, Meteor Soc Japan, 615-627 Namias, J (1969) Seasonal interactions between the North Pacific Ocean and the atmosphere during the 1960’s Mon Wea Rev., 97, 173-192 Namias, J (1976) Negative ocean-air feedback systems over the North Pacific in the transition from warm to cold seasons Mon Wea Rev., 104, 1107-1121 Namias, J., X.Yuan and D.R Cayan 1988: Persistence of North Pacific sea surface temperature and atmospheric flow patterns J Climate, 1, 682-703 Newell, R.E.,R Selkirk, and W Ebisuzaki (1982) The Southern Oscillation: sea surface temperature and wind relationships in a 100-year data set J Climatology, 2, 357-373 Nicholls, N (1980) Long-range weather forecasting, value, status, and prospects Rev Geophys Space Phys., 18, 771-788 Nitta, T and S Yamada (1989) Recent warming of tropical sea surface temperature and its relationship to the Northern hemisphere circulation J Meteor Soc Japan, 71, 367-375 Orszag, S.A (1970) Transform method for the calculation of vector-coupled sums: Application to the spectral form of the vorticity equation J Atmos Sci., 27, 890-895 Paegle, J., K.C Mo, and J.N Paegle (1996) dependence of simulated precipitation on surface evaporation during the 1993 United States summer floods Mon.Wea.Rev., 124, 345-361 Pazan, S and G Meyers (1982) Interannual fluctuations of the tropical Pacific wind field and the Southern Oscillation Mon Wea Rev., 110, 587-600 Philander, S.G.H (1981) The response of equatorial oceans to a relaxation of the trade winds J Phys Oceanogr., 6, 632-645 Philander, S.G.H (1990) El Niño, La Niña and the Southern Oscillation Academ Press, 193pp Philander, S.G.H and A.D Seigel (1984) Simulation of El Niño of 1982-1983 Coupled-Atmosphere Models J.G.J Nihoul Ed., Elsvier Oceanography Series No 40, 517-541 Phillips, N.A (1956) The general circulation of the atmosphere : a numerical experiment Quart J Roy Meteor Soc., 82, 123-164 Platzman, G.W (1960) The spectral form of the vorticity equation J Meteor., 17, 635-644 Platzman,G.W (1990) The atmosphere—A challenge, Charney’s recollection In: The atmosphere—A challenge The science of Jule Gregory Charney, Eds R Lindzen, E Lorenz, and G.W Platzman, Amer Meteor Soc., 11-88 Quinn, W.H (1974) monitoring and predicting El Niño invasions J Appl Meteor., 13, 825-830 Ramage, C.S (1975) Preliminary discussion of the meteorology of the 1972-73 El Niño Bull Amer Meteor Soc., 56, 234-242 Rasmusson, E.M and T.H Carpenter (1982) Variations in tropical sea surface temperature and surface wind fields associated with the Southern Oscillation/ El Niño Mon Wea Rev., 110,354-384 Rex, D.R (1950) Blocking action in the middle troposphere and its effect upon regional climate I An aerological study of blocking action Tellus, 2, 169-211 Richtmeyer, R.D and R Morton (1967) Difference method for initial value problem 2nd edition Interscience Publ., New York Robert ,A.(1982) A semi-Lagrangian and semi-implicit numerical integration scheme for the primitive meteorological equations J.Meteor Soc.Japan, 60, 319-325 Rosati, A and K Miyakoda (1988) A general circulation model for upper ocean circulation J Phys Oceanogr., 18, 1601-1626 Rossby, C.G (1956) Current problems in meteorology In: The Atmosphere and the Sea in Motion: The Rossby Memorial Volume, 9-50 Rowntree, P.R (1972) The influence of tropical east Pacific Ocean temperature on the atmosphere Quart J Roy Meteor Soc., 98, 290-321 Sarkisyan, A.S (1966) Fundamentals of the theory and calculation of ocean currents (Russian) Gidrometeoizdat, Moscow Schopf, P.S and M.J Suarez (1988) Vacillation in a coupled ocean-atmosphere model J Atmos Sci., 45, 549-566 Semtner, B and R M.Chervin, (1988) A simulation of the global ocean circulation with resolved eddies J Geophys Res 93 (C12), 15502-15775 Shukla,J (1981) Dynamical predictability of monthly means J Atmos Sci., 38, 2547- 2572 Shukla, J (1984) Predictability of time averages: Part II: The influence of the boundary forcings In: Problems and prospects in long and medium range weather forecasting Ed D.M Burridge and E Källen Springer-Verlag, Berlin, pp 155-200 Silberman, I.S (1954) Planetary waves in the atmosphere J Meteor ,11,27-34 Smagorinsky, J (1963) General circulation ecxperiments with the primitive equations: I, The basic experiment Mon Wea Rev., 91, 99-164 Smagorinsky, S., S Manabe and J.L Holloway (1965) Numerical results from a nine- level general circulation model of the atmosphere Mon.Wea.Rev., 93, 727-768 Smagorinsky, J (1983) The beginning of numerical weather prediction and general circulation modeling Early recollections Advances Geophys Vol 25, Academic Press 3-37 Smagorinsky, J (1993) Some historical remarks on the use of nonlinear viscosities In: Large Eddy Simulation of Complex Engineering and Geophysical Flows In: Proc Internat Workshop in LES, St Petersburg, FL, Dec 19-21, 1990 Eds B Galperin and S.A Orszag, Cambridge University Press, 1-34 Stommel, H (1961) Thermohaline convection with two stable regimes of flow Tellus, 13, 224-230 Straus, D (1998) Comparing the SST-forced variability of seasonal mean 500 hPa heights in the DSP integrations of COLA, CPC, NCEP and NCAR Internal Rept., No.5, COLA 18 pp Takano, K.(1974) A general circulation model of the world ocean, Numerical simulation of weather and climate, Tech Report No 8, Dept of Meteorology, UCLA, 47 pp Trenberth, K.E., (1975) A quasi-biennial standing wave in the Southern Hemisphere and interrelations with sea surface temperature Quart J Roy Meteor Soc., 101, 55-74 Trenberth, K.E 1990: Recent observed interdecadal climate changes in the Northern Hemisphere BAMS, 71, 988-993 Troup, A.J (1965) The Southern Oscillation Quart J Roy Meteor Soc., 91, 490-506 van Loon, H and R.A Madden (1981) The Southern Oscillation Part I: Global associations with pressure and temperature in northern winter Mon Wea Rev., 109, 1150-1162 Walker, G.T (1924) Correlation in seasonal variations of weather, IX A further study of world weather Memoirs of the India Meteor Depart., 24, 275-352 Wallace, J.M and D.S Gutzler (1981) Teleconnections in the geopotential height field during the Northern Hemisphere winter Mon Wea Rev., 109, 784-812 Weare, B.C., (1982) El Niño and tropical Pacific Ocean surface temperature J Phys Oceanogr., 12, 17-27 Webster, P.J (1972) Response of the tropical atmosphere to local steady forcing Mon Wea Rev., 100, 518-541 Webster, P.J (1982) Seasonality in the local and remote atmospheric response to sea surface temperature anomalies J Atmos Sci., 39, 41-52 White, W.B., R Bernstein, G McNally, S Pazan and R Dickson (1980) The thermocline response to transient atmospheric forcing in the interior midlatitude North Pacific 1976-1978 J Phys Oceanogr., 10, 372-384 Wooster, W.S and O Guillen (1979) Characteristics of El Niño in 1972 J Mar Res., 32, 387-404 WMO (World Meteor Organization) (1980) Report of the informal meeting of experts on long-range forecasting Progress on short-, medium-, and long-range weather prediction research, Geneva, Swiss, 1-10 WMO (World Meteorological Organization) (1982) The WMO-CAS/JSC expert study meeting on long-range forecasting Public Ser No.1, pp238 Wyrtki, K (1973) Teleconnections in the equatorial Pacific Ocean Science, 180, 66-68 Wyrtki,K (1975) El Niño - the dynamic response of the equatorial Pacific Ocean atmospheric forcing J Phys Oceanogr., 5, 572-584 Wyrtki,K., E Stroup, W Patzert, R Williams and W Quinn (1976) Predicting and observing El Niño Science, 191, 343-346 Yamazaki, M (1996) Study on CISK and cloud system In: Evolution from Meteorolgical to Climatological Dynamics Ed A Sumi, Center of Climate System Research (in Japanese) pp 75-96 Zebiak, S.E (1982) A simple atmospheric model of relevance to El Niño J Atmos Sci., 39, 2017-2027 ... needs an extended Arakawa Jacobian Arakawa and Lamb (1981) achieved both an energy and potential enstrophy conservation scheme for the general flow, and applied it to the three diemensional UCLA... wind and atmospheric pressure anomalies under a local ocean heating along the equator, and this pattern is symmetrical Julian and Chervin (1978), Horel and Wallace (1981), Keshavamurty (1982), and. .. Arakawa, and George Mellor, Bill Bourke, S Manabe, Kinse Mo, and Hisashi Nakamura who reviewed this memoir and gave me many valuable suggestions and comments I thank Drs Jim Kinter and Uma Bhatt,