A comparative study of surface air temperature between satellite and model in vietnam from 2004 to 2013

THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY TRAN THI THU THAO A COMPARATIVE STUDY OF SURFACE AIR TEMPERATURE BETWEEN SATELLITE AND MODEL IN VIETNAM FROM 2004 TO 2013 BACHELOR THESIS Study Mode: Full-time Major: Environmental Science and Management Faculty: Advanced Education Program Office Batch: 2014-2018 Thai Nguyen, 10/08/2018 Thai Nguyen University of Agriculture and Forestry Degree Program Bachelor of Environmental Science and Management Student name Tran Thi Thu Thao Student ID DTN1454290063 A comparative study of surface air temperature between satellite Thesis Title and model in Vietnam from 2004 to 2013 Prof Dr Chian Yi Liu- National Central University, Taiwan Supervisor(s) Assoc Prof Dr Tran Quoc Hung- Thai Nguyen University of Agriculture and Forestry, Vietnam Supervior’s signature Abstract: Surface air temperature is both an indicator and a driving force for regional and global changes There is a difference between the years-to-years of air temperature due to random variations Besides, Surface air temperature is an important parameter for a wide ranges of applications such as biogas conversion studies, hydrology and climate change studies Research about climate change in Vietnam is a challenge because the climate in Vietnam is seasonal, according to the geographic location of each region, so that the surface air temperature is an important key This study is about the comparison of surface air temperature from Atmospheric Infrared Sounder (AIRS) of Aqua satellite with the reanalysis European Center for Medium-range Weather Forecasts (ECMWF) model over Vietnam and three sub regions based on differences in altitude and climate from 2004 to 2013 by using Matlab tool It was i conducted not only to compare which datasets captures the surface air temperature in better way, but also to see that during the years of the study climate change has occurred The research performs that AIRS data able to present the effect of topography and climate on the surface air temperature better than ECMWF model Keywords Surface air temperature, atmospheric infrared sounder(AIRS), ECMWF reanalysis Number of pages 53 Date of submission 25th September, 2018 ii ACKNOWLEAGEMENT In the process of implementing the research topics: " A comparative study of surface air temperature between satellite and model in Vietnam from 2004 to 2013" I got the guide and help, encouragement of the lecturers and the other people I would like to express sincere gratitude to: First and foremost, I wish to express sincere thanks to the Director Board of Thai Nguyen University of Agriculture and Forestry, board of managers of International Training and Development Center and all the teachers have dedicated teaching, the scientific knowledge and the valuable experience for me during the training period, learning in school I sincerely thank the cooperation between Thai Nguyen University of Agriculture and Forestry and National Central University for giving me a wonderful opportunity to internship in Taiwan It gives me new knowledge with a thesis to graduate In particular, I take this opportunity to express profound gratitude and deep regards to the supervisor Prof Dr Chian Yi-Liu who guided wholeheartedly, to advise, imparted knowledge and valuable experience to help me during the internship in Taiwan Furthermore, I express my appreciation to Assoc.Prof Dr Tran Quoc Hung for his enthusiastic guidance His detailed instructions and encouraging after I returned from my internship in Taiwan helped me to complete the report I am also thankful to Mr Chi-Hao Chiu and Ms Tran Huyen Trang for teaching me various techniques, methods used in satellite and model data and helps me iii to analysis the data Without the comments and the motivation from them, my research work was not able to complete well Finally, I would like to express our gratitude to my family, relatives and friends who have helped me during the internship I would not have been able to complete this thesis without their continuous help and encouragement Sincerely, Tran Thi Thu Thao iv CONTENTS LIST OF FIGURES vii LIST OF TABLE viii LIST OF ABBREVIATIONS ix PART I INTRODUCTION 1.1 Research rationale 1.2 Research’s objectives 1.3 Research question 1.4 Limitations PART II LITERATURE REVIEW 2.1 Surface air temperature 2.2 AIRS satellite, ECMWF model and Matlab PART III METHODOLOGY 14 3.1 Data collection 14 3.2 Region selected 15 3.3 Data Analysis 17 PART IV RESULTS 19 4.1 The different between AIRS satellite and ECMWF model about SAT 19 4.1.1 The different between AIRS satellite and ECMWF model about SAT in sub regions 19 Fig 6: AIRS measured and ECMWF model estimated over Tay Nguyen region 23 4.1.2 The difference between three sub regions about monthly SAT by ECMFW model estimated and AIRS measured 27 v 4.1.3 The different between AIRS satellite and ECMWF model about SAT in Vietnam 28 4.2 The different between AIRS satellite and ECMWF model about SAT in each season 33 PART V DISCUSSION AND CONCLUSION 37 5.1 Discussion 37 5.2 Conclusion 38 REFERENCES 40 vi LIST OF FIGURES Fig Frame word of study 14 Fig Vietnam region with latitude interval 70N-250N and longitude interval 1000E1100E (from Google earth) 15 Fig Bac Bo region with latitude interval 210N-22030'N and longitude interval 103030'E-116030'E (from Google earth) 16 Fig Tay Nguyen region with latitude interval 120N-14045'Nand longitude interval 1070E-1080E (from Google earth) 16 Fig Nam Bo region with latitude interval 9045'N-10045'Nand longitude interval 105015'E-106015'E (from Google earth) 17 Fig AIRS measured and ECMWF model estimated over Bac bo region 20 Fig AIRS measured and ECMWF model estimated over Tay nguyen region 23 Fig AIRS measured and ECMWF model estimated over Nam bo region 26 Fig ECMWF model estimated over sub regions 27 Fig 10 AIRS measured over sub regions 28 Fig 11 AIRS measured and ECMWF model estimated over study region 31 Fig 12 The different between AIRS satellite and ECMWF model annual SAT by month in each season in Bac Bo region (◦C).a) Hot season; b) Cold season 34 Fig 13 The different between AIRS satellite and ECMWF model about annual SAT by month in each season in Tay Nguyen region(◦C) a) Rainy season; b) Dry season 35 Fig 14 The different between AIRS satellite and ECMWF model about annual SAT by month in each season in Nam Bo region (◦C) a) Rainy season; b) Dry season 36 vii LIST OF TABLE Table 1: CC, difference and rsme between AIRS measured and ECMWF model estimated SAT 31 Table 2: The average annual SAT of study region and sub regions 32 Table 3: CC between AIRS measured and ERA model estimated SAT in each seasons 33 viii ABBREVIATIONS AIRS CC DHS ECMWF EOS IMHEN Atmospheric Infrared Sounder Correlation coefficient data handling system European Center for Medium-range Weather Forecasts Earth Observing System Vietnam on Disaster Risk Management and Extreme Conditions to Promote Climate Change Adaptation IPCC Intergovernmental Panel on Climate Change JCSDA Joint Center for Satellite Data Assimilation Matlab MATrix LABoratory NWP Numerical weather prediction RCPs Representative Concentration Pathways RMES Root mean square error SAT Surface air temperature t2m meter temperature ix General Statistics Office of Vietnam "Population, population and population density in 2011 by province" September 30, 2012 Hu et al, T Hu, Y Sun, X.B ZhangTemperature and precipitation projection at 1.5 °C and 2.0 °C increase in global mean temperature Chin Sci Bull., 62 (26) (2017), pp 3098-3111, 10.1360/N972016-012342017 Hulme, M Hulme1.5 °C and climate research after the Paris agreement Nat Clim Change, (3) (2016), pp 222-224, 2016 IPCC: Climate Change 2007: The Scientific Basis, Contribution of Working Group to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2007 Jiang and Fu, D.B Jiang, Y.H Fu Climate change over China with a °C global warming Chin J Atmos Sci., 36 (2) (2012), pp 234-246 (in Chinese), 2012 Jiang et al, D.B Jiang, Y Sui, X.M LangTiming and associated climate change of a °C global warming Int J Climatol., 36 (2016), pp 4512- 4522, 10.1002/joc.4647, 2016 Joshi et al, M Joshi, E Hawkins, R Sutton, et al.Projections of when temperature change will exceed °C above pre-industrial levels Nat Clim Change, (8) (2011), pp 407-412, 2011 Kosaka, Y., and S.-P Xie: Recent global-warming hiatus tied to equatorial Pacific surface cooling Nature, 501, 403-407, 2013 Le Marshall, J., Jung, J., Derber, J., Treadon, R., Lord, S., Goldberg, M., Wolf, W., Liu, H.C., Joiner, J., Woollen, J and Todling, R 2005a AIRS hyperspectral data improves southern hemisphere forecasts Aust Met Mag., 54, 57-60 41 Le Marshall, J., Jung, J., Derber, J., Treadon, R., Lord, S., Goldberg, M., Wolf, W., Liu, H.C., Joiner, J., Woollen, J and Todling, R 2005b Impact of Atmospheric Infrared Sounder Observations on Weather Forecasts EOS, 86, 109, 115, 116 Mitchell et al, D Mitchell, R James, P.M Forster, et al.Realizing the impacts of a 1.5 °C warmer world Nat Clim Change, (8) (2016), pp 735- 737, 10.1038/nclimate3055, 2016 Nicholls, N., G V Gruza, J Jouzel, T R Karl, L A Ogallo, and D E Parker, Observed climate variability and change, in The IPCC Second Scientific Assessment, edited by J T Houghton et al., pp 133-192, Cambridge Univ Press, New York, 1996 Schleussner et al, C.F Schleussner, J Rogelj, M Schaeffer, et al.Science and policy characteristics of the Paris agreement temperature goal Nat Clim Change, (7) (2016), pp 1-9, 10.1038/nclimate3096, 2016 Schroder M, Jonas M, Lindau R, Schulz J, Fennig K The CM SAF SSM/I-based total column water wapour climate data record: Methods and evaluation against reanalyses and satellite Atmos Meas Tech, 6: 765-775, 2013 Sky News, "The Forecast For Weather Technology" 2015-07-17 Retrieved 2016-0101 Stisen, S., Sandholt, I and Eklundh, L Estimation of diurnal air temperature using MSG SEVIRI data in West Africa Remote Sensing of Environment, 110(2), pp.262-274, 2007 42 Sui et al, Y Sui, X.M Lang, D.B JiangTemperature and precipitation signals over China with a °C global warming Clim Res., 64 (2015), pp 227-242, 2015 The MathWorks Inc MATLAB 7.0 (R14SP2) The MathWorks Inc., 2005 Trenberth K E,: Changes in precipitation with climate change, 2011 Clim Res., 47, 123-138, doi:10.3354/cr00953 Vautard et al, R Vautard, A Gobiet, S Sobolowski, et al.The European climate under a °C global warming Environ Res Lett., (2014), Article 034006, 10.1088/1748-9326/9/3/034006, 2014 Wang Y, Zhang Y, Fu Y F, Li R, Yang Y J A climatologically comparison of columnintegrated water wapor for the third-generation reanalysis datasets Science Cina: Earth Sciences, doi:10.1007/s11430-015-5183-6 2015 Zhai et al, P.M Zhai, R Yu, B.Q Zhou, et al.Research progress in impact of 1.5 °C Global warming on global and regional scales Clim Change Res., 13 (2017), pp 465-472 (in Chinese), 2017 Zhang et al, L Zhang, Y.H Ding, T.W Wu, et al.The 21st century annual mean surface air temperature change and the °C warming threshold over the globe and China as projected by the CMIP5 models Acta Meteorol Sin., 71 (2013), pp 1047-1060, 10.11676/qxxb2013.087 (in Chinese), 2013 Zhang, Y Zhang Projections of 2.0 °C warming over the globe and China under RCP4.5 Atmos Ocean Sci Lett., (6) (2012), pp 514-520, 2012 Vietnamese Source Ministry of Natural Resources and Environment: Scenarios for Climate Change, Sea Level Rise for Vietnam, Hanoi, 2009 43 My Xuan, Climate change in the past and future in Vietnam My Xuan - EINFO (Based on the research of Phan Van Tan, Ngo Duc Thanh, Department of Meteorology, Hydrology and Oceanography, University of Science , VNU) 05/11/2014, 2014 Nguyen Duc Ngu, Nguyen Trong Hieu: Climate change and its impact in Vietnam over the past 100 years - Nature and people Publisher: Truth, Hanoi, 1991 Nguyen Duc Ngu, Nguyen Trong Hieu: Climate change situations in Vietnam in the coming decades Institute of Hydrometeorology, 1999 Nguyen Trong Hieu, Dao Duc Tuan: Climate change situations in Southeast Asia and Vietnam Institute of Hydrometeorology 1993 44 APPENDICES Table Topography of sub regions Region Altitude Bac Bo 2000m Tay 500-600m Northern Southern Eastern Western Altitude Altitude Altitude Altitude >1000m 600m 500m 1000 >500m 24ºC 400mm >24ºC average) Nguyen Nam Bo Monsoon Table AIRS satellite monthly data of SAT over Bac Bo region (◦C) Years 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 15.9 16 16.7 15.8 17.5 15.6 18.5 15.3 15.1 15.5 20 18.6 19.6 19.3 17.1 21.8 20.6 18.9 19.3 20.6 21.5 20.6 21.8 21.9 21.2 22.2 21.8 20.2 20.9 21.3 22.8 23.3 23.9 22.9 23.4 22.2 23.2 22.3 23.9 22.9 23.8 25.3 24.2 23.9 23.7 23.4 24.5 23.9 24.6 24 24 24.3 24.7 24.8 24.2 24.6 24.9 24.4 24.3 24.5 24.3 24.7 24.7 24.6 24.5 24.5 25 23.9 24.9 24.1 24.2 23.9 24.1 24.7 24.2 24.8 24.2 24.4 24.7 24.3 23.2 23.8 23.3 23 23.6 23.9 23.9 23.2 23.1 23.4 10 21.4 21.7 21.9 21.2 21.9 21.5 22.1 20.8 21.8 21.8 11 19.8 19.8 20.8 19.9 18.7 19.8 20 19.4 20.6 20.1 12 14.5 16.1 15.8 18.9 16.4 17.5 19.1 15.3 18 16.3 Months Table ECMWF model monthly data of SAT over Bac Bo region (◦C) Years 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 15.9 16 16.7 15.8 17.5 15.6 18.5 15.3 15.1 15.5 20 18.6 19.6 19.3 17.1 21.8 20.6 18.9 19.3 20.6 21.5 20.6 21.8 21.9 21.2 22.2 21.8 20.2 20.9 21.3 22.8 23.3 23.9 22.9 23.4 22.2 23.2 22.3 23.9 22.9 23.8 25.3 24.2 23.9 23.7 23.4 24.5 23.9 24.6 24 24 24.3 24.7 24.8 24.2 24.6 24.9 24.4 24.3 24.5 24.3 24.7 24.7 24.6 24.5 24.5 25 23.9 24.9 24.1 24.2 23.9 24.1 24.7 24.2 24.8 24.2 24.4 24.7 24.3 23.2 23.8 23.3 23 23.6 23.9 23.9 23.2 23.1 23.4 10 21.4 21.7 21.9 21.2 21.9 21.5 22.1 20.8 21.8 21.8 11 19.8 19.8 20.8 19.9 18.7 19.8 20 19.4 20.6 20.1 12 14.5 16.1 15.8 18.9 16.4 17.5 19.1 15.3 18 16.3 Months Table AIRS satellite monthly data of SAT over Tay Nguyen region (◦C) Years 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 22.5 21.5 22.4 21.4 22.3 20.8 23.3 21.2 22 21.7 23.8 24.3 24.1 24.8 22.5 24.1 25.2 23.2 24.2 24.4 25.4 25 25.7 25.1 24.9 25.4 25.4 24 25.1 25.4 26.1 26.1 25.9 25.6 25.9 25.2 26.2 25.3 25.8 25.6 25.8 26 25.7 25.1 25.1 24.9 26.2 25.6 25.7 26.1 24.8 25.2 25.7 25.6 25.5 25.3 26.1 25.2 25.3 25.3 25.1 24.9 24.9 24.9 25.2 25 25.4 25 24.6 24.7 24.3 24.8 24.4 24.6 27.3 25 24.9 24.7 25 24.5 24.3 24.4 24.2 24.2 24.1 24.1 25 24 24.2 24.3 10 23.4 23.9 23.3 23.5 24.1 23.5 23.8 23.3 23.8 23.3 11 22.8 23.4 23.4 22.4 22.7 22.6 22.6 22.9 24 23 12 21.7 21.3 21.3 22.4 21.6 21.9 22.1 21.2 23.1 21.5 Months Table ECMWF model monthly data of SAT over Tay Nguyen region (◦C) Years 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 18.3 17.6 18.9 18.7 18.4 17.1 19.6 17.8 19.7 18.6 18 20.2 20.1 19.4 17.6 20.4 20.9 18.8 20.3 20.9 21.2 20.5 21.5 22.8 20.5 22.5 22.1 20.1 22 22.9 24.2 23.2 23.8 23.7 23.9 23.9 24.8 22.3 24.2 24.8 25.1 25.2 24.4 24.6 24 24 26.1 25 25.2 25.5 24.7 25.3 25.3 25.5 24.8 24.9 25.8 24.8 25.2 25 24.1 24.1 24.5 24.4 24.4 24.2 24.8 24.4 24.5 24.4 24.3 24.1 24 24.1 23.9 24.4 24.4 24.4 24.5 24.3 23.4 23.8 23.4 24 23.6 23.8 24.4 23.9 23.7 23.5 10 21.7 23.2 22.8 22.7 25.4 23.1 23 23.1 22.9 22.5 11 21.2 22.2 21.8 20.3 21.6 21.4 21.6 21.9 23 22.2 12 18.1 19.6 19.7 19.8 18.9 19.6 19.4 19.4 21.4 17.8 Months Table 10 AIRS satellite monthly data of SAT over Nam Bo region (◦C) Years 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 26.4 25.6 26.6 25.8 26.4 25.5 26.5 25.6 26.4 26.1 26.7 26.6 27.3 26.3 26.4 26.7 27.1 25.8 27.2 27.2 27.8 26.9 27.8 27.1 27.6 27.5 27.7 26.5 27.7 27.9 27.9 27.8 28 27.8 28.2 27.5 28 27.4 27.9 28 28.1 27.9 27.9 27.7 27.5 27.3 28.1 27.9 28 28.3 27.2 27.7 27.7 27.8 27.6 27.8 27.8 27.5 27.8 27.9 27.5 27.4 27.5 27.3 27.5 27.3 27.7 27.6 27.5 27.2 27.1 27.5 26.9 27.4 27.2 27.5 27.7 27.6 27.7 27.3 26.2 27.5 26.8 27.3 27 27.3 27.8 27.1 27.2 27.4 10 26.9 27.3 26.8 27.2 27.6 27.1 27.2 27.3 27.4 27.1 11 26.7 27.1 26.9 26.6 26.6 26.8 26.8 27 27.4 27.2 12 26.1 25.9 26.1 26.5 26 26.1 26.4 26.1 27 26 Months Table 11 ECMWF model monthly data of SAT over Nam Bo region (◦C) Years 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 23.2 22.4 23.5 23.6 23.2 21.6 23.2 22.9 23.8 23.7 23.9 24 24.5 23.1 23.4 23.5 24.2 23.8 24.3 24.6 26 25.3 25.3 25.7 24.7 25.7 25.8 25 25.6 26.3 28 27.8 26.5 27 26.4 26.8 27.4 25.9 26.7 27.3 27.7 27.8 26.7 26.9 26.6 26.5 28.1 27.1 27 27.7 26.6 27.3 26.8 26.9 26.6 27.2 27.4 26.9 27.1 27 26.3 26 26.5 26.1 26.3 26.2 26.6 26.3 26.2 26.3 26.2 26.4 26.2 26.2 25.9 26.7 26.3 26.2 26.6 26.5 25.8 26.2 26 26.1 25.7 26.1 26.3 26.1 25.6 26.1 10 25.2 25.5 25.6 25.3 25.6 25.6 25.6 25.8 25.6 25.6 11 25.1 25 25.5 24.2 24.6 24.9 24.9 25.3 25.5 25.4 12 23 23.4 23.6 23.7 23.4 23.3 24 23.5 24.6 23.1 Months Table 12 AIRS satellite monthly data of SAT over study region (◦C) Years 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 22.4 21.8 22.7 21.8 22.4 21.5 23.1 21.7 22 22.3 24.1 23.7 24.4 23.7 22.9 25.1 24.7 23.5 24.4 24.7 25.2 24.6 25.4 25.4 24.9 25.5 25.4 24.3 25.1 25.3 26.1 26.1 26.4 25.8 26.3 25.7 26.2 25.5 26.3 26.2 26.5 26.9 26.5 26.3 26.1 26 27 26.5 26.8 26.8 26.2 26.5 26.7 26.8 26.4 26.7 26.9 26.6 26.5 26.7 26.3 26.5 26.4 26.5 26.4 26.5 26.8 26.5 26.4 26.2 26.1 26.1 26 26.3 26.2 26.5 26.3 26.3 26.4 26.2 25.5 25.9 25.4 25.7 25.8 26 26.2 25.7 25.7 25.7 10 24.6 25.1 24.8 24.7 25.2 24.9 25 24.6 25.3 24.9 11 23.9 24 24.4 23.5 23.5 23.6 24 23.8 24.8 24.2 12 22.2 21.8 21.9 23 22 22.3 23.1 21.5 23.6 21.7 Months Table 13 ECMWF model monthly data of SAT over study region (◦C) Years 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 18.1 17.6 18.1 17.8 17.6 16.6 19.2 17.8 18.2 18.4 18.5 19.6 19.8 19.5 17.4 20.2 20.2 18.8 19.1 20.6 21.3 20.6 21.4 21.9 20.9 21.6 21.7 19.7 21.3 22.3 23.8 23.7 24 23.4 23.8 23.8 24 22.8 24 24.1 25.1 25.9 24.7 24.8 24.7 24.7 26.3 24.9 25.6 25.6 25.5 26.3 25.9 26.1 25.4 25.9 26.2 25.9 25.9 25.8 25.2 25.6 25.8 25.7 25.4 25.7 26 25.7 25.5 25.5 25.4 25.4 25.2 25.3 25.2 25.6 25.3 25.1 25.4 25.3 25.4 24.8 24.3 24.4 24.7 24.9 25.1 24.8 24.4 24.5 10 22.4 23.4 23.7 23.1 23.9 23.7 23.2 23.1 23.4 22.8 11 21.2 21.8 21.8 19.9 20.8 20.5 20.5 21.3 22.5 21.7 12 17.8 18.5 18.9 19.5 18.2 19 19.4 18.4 20.1 17.1 Months Table 14 Monthly Bias of ECMWF model estimated SAT with respect to AIRS over sub region Bac Bo Month Bias (ºC) Month Bias (ºC) Jan -6.119 Jul -2.001 Feb -7.534 Aug -2.344 Mar -6.793 Sep -2.747 Apr -4.887 Oct -3.13 May -3.307 Nov -5.847 Jun -1.959 Dec -5.468 Table 15 Monthly Bias of ECMWF model estimated SAT with respect to AIRS over sub region Tay Nguyen Month Bias (ºC) Month Bias (ºC) Jan -3.448 Jul -3.448 Feb -4.405 Aug -4.405 Mar -3.517 Sep -3.517 Apr -1.883 Oct -1.883 May -0.698 Nov -0.698 Jun -0.268 Dec -0.268 Table 16 Monthly Bias of ECMWF model estimated SAT with respect to AIRS over sub region Tay Nguyen Month Bias (ºC) Month Bias (ºC) Jan -2.964 Jul -1.18 Feb -2.808 Aug -1.053 Mar -1.895 Sep -1.144 Apr -0.898 Oct -1.646 May -0.641 Nov -1.86 Jun -0.71 Dec -2.661 ... air temperature 2.1.1 Surface air temperature and factors affecting SAT Surface air temperatures are both an indicator and a driver of regional and global changes There are year -to- year and regional... Comparison of satellite and model data (CC, Average difference and rmse) Fig Frame work of study 3.1 Data collection - AIRS data: AIRS3STM: AIRS/Aqua L3 Monthly Standard Physical Retrieval (AIRS-only)... important of Surface air temperature Air temperature conditions many aspects of human life, from the clothing we wear to the fuel costs we pay Air temperature and air temperature cycles also act to