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Nanjing University of Information Science and Technology (南京信息工程大学) 2020

Simulated Moisture Changes over the Arid Central Asia during the past Warm/Cold Period

许红娜

Titre : Simulated Moisture Changes over the Arid Central Asia during the past Warm/Cold Period

Auteur : 许红娜

Grade : Master’s Theses 2020

Université : Nanjing University of Information Science and Technology (南京信息工程大学)

Résumé
In this study,climate changes over Arid Central Asia(ACA),which includes the Central Asia and Xinjiang area in China,during the mid-Holocene(approximately 6,000 calendar years ago,MH)and the Last Glacial Maximum(approximately 21,000 calendar years ago,LGM)are investigated using multimodel simulations derived from the Paleoclimate Modelling Intercomparison Project Phase 3(PMIP3).In addition,this study also investigates the climate between the Medieval Climate Anomaly(MCA ;950-1250 AD)and Current Warm Period(CWP ;1950-2005 AD)over ACA using the Community Earth System Model-Last Millennium Ensemble(CESM-LME)simulations,to better understand global warming’s impact on the climate over ACA.The conclusions are as follows :(1)During the LGM,the strong cooling is evident over the whole ACA,and precipitation decreases significantly.The seasonal cycles of precipitation over the Central Asia and Xinjiang are weakened.Compared with the pre-industrial,the core area of ACA shows drier conditions.Decreasing precipitation plays a dominant role in shaping the drier conditions,whereas reduced potential evapotranspiration(PET)plays a secondary but opposite role.(2)During the MH,due to different orbital parameters,the seasonal cycle of surface air temperature(SAT)is strengthened over ACA.Precipitation over the ACA decreased in all the seasons.A drier climate appears in southern Central Asia and western Xinjiang,which is consistent with reconstructions.And the drier climate is mainly caused by decreased precipitation.(3)With relative to the Little Ice Age(LIA ;1550-1850 AD),warmer conditions over the ACA are simulated during the MCA and CWP.For the MCA,the warming can be seen over the whole region.But for the CWP,the warming can be seen over most ACA except the Caspian Sea and surrounding regions.Moreover,the warming is stronger.During the MCA,the precipitation increases by 0.04% and 1.08% over the Central Asia and Xinjiang area,respectively.During the CWP,enhancement of the precipitation is stronger over the Xinjiang with an increase of 1.33%,whereas the precipitation decreases by 0.82% over the Central Asia.Detailed analysis shows,over the ACA south of 50°N,changes of the precipitation play a dominant role in determining aridity index(AI)changes,and the warming plays a secondary role during the MCA ;For the CWP,over the ACA south of 45°N,the situation is similar,but the influence from changes of temperature on AI is weaker ;In addition,the contribution from changes of wind speed to the AI is weaker during the MCA and CWP,compared with the LGM.

Mots clés : paleoclimate modelling ;Arid Central Asia ;moisture changes ;cold/warm period ;aridity index ;

Présentation (CNKI)

Page publiée le 29 mars 2022