Objective LGM is a critical climate period in the late Quaternary and is the most recent extreme cold event. Clark et al. （2009） used 4271^14C records and 475 cosmogenic nuclide datings to define LGM be in 26.5-19....Objective LGM is a critical climate period in the late Quaternary and is the most recent extreme cold event. Clark et al. （2009） used 4271^14C records and 475 cosmogenic nuclide datings to define LGM be in 26.5-19.0 kaBP. LGM age often changes with time in different regions （Mix et al., 2001; Zhang Zhigang et al., 2015）. However, LGM has not been described to date in the Beijing region. During our field work in 2015-2017, LGM event stratigraphy was discovered from sevral boreholes in the middle and lower region of Yongding river basin, Southern Beijing plain.展开更多
LGM climate study is a hot topic in international fields on global changes. Climate simulation in this study applies both common designs of 21 kaBP boundary conditions from the Paleoclimate Modeling Intercomparison Pr...LGM climate study is a hot topic in international fields on global changes. Climate simulation in this study applies both common designs of 21 kaBP boundary conditions from the Paleoclimate Modeling Intercomparison Project (PMIP), including insolation, glaciation, sea surface temperature and atmospheric CO2 concentration, and land surface conditions from Eurasia continent by compilation of geological evidence. The simulation outputs are in agreement with climate spatial patterns reconstructed by observation records. Sensitive experiment on land surface conditions shows that changes in vegetation would make significant impacts on temperature and precipitation. Particularly in the Tibetan Plateau, this change would increase in differences of winter and summer temperature, precipitation and P-E.展开更多
Chinese lake status database has provided systematic geological records of much higher lake level and fresher water than today at the LGM from western China. This wet condition was significant contrast with very dry c...Chinese lake status database has provided systematic geological records of much higher lake level and fresher water than today at the LGM from western China. This wet condition was significant contrast with very dry conditions in eastern China. Together with lake studies from Eurasian continents, there was a wet-condition belt from the Mediterranean and the Middle East, Central Asia to western China. Palaeoclimate simulations confirmed that the wet conditions in western China were produced by decrease of the evaporation and increase of precipitation by positive anomaly of annual P-E of 70-95 mm/a between the LGM and today. The westerlies enhanced in the strength and shifted southwards-eastwards in the position, and the low thermal conditions in the Eurasian continent creating temperature 4-16℃ lower than today and relatively low evaporation, were the major two important climate conditions to yield cold-wet climates in western China.展开更多
Using a regional climate model MM5 nested to an atmospheric global climate model CCM3, a series of simulations and sensitivity experiments have been performed to investigate the relative LGM climate response to change...Using a regional climate model MM5 nested to an atmospheric global climate model CCM3, a series of simulations and sensitivity experiments have been performed to investigate the relative LGM climate response to changes of land-sea distribution, vegetation, and large-scale circulation background over China. Model results show that compared with the present climate, the fluctuations of sea-land distribution in eastern Asia during the LGM result in the temperature decrease in winter and increase in summer. It has significant impact on the temperature and precipitation in the east coastal region of China. The impact on precipitation in the east coastal region of China is the most significant one, with 25%-50% decrease in the total precipitation change during the LGM. On the other hand, the changes in sea-land distribution have less influence on the climate of inland and western part of China. During the LGM, significant changes in vegetation result in temperature alternating with winter increase and summer decrease, but differences in the annual mean temperature are minor. During the LGM, the global climate, i.e., the large-scale circulation background has changed significantly. These changes have significant influences on temperature and precipitation over China. They result in considerable temperature decreases in this area, and direct the primary patterns and characteristics of temperature changes. Results display that, northeastern China has the greatest temperature decrease, and the temperature decrease in the Tibetan Plateau is larger than in the eastern part of China located at the same latitude. Moreover, the change of large-scale circulation background also controls the pattern of precipitation change. Results also show that, most of the changes in precipitation over western and northeastern parts of China are the consequences of changing large-scale circulation background, of which 50%-75% of precipitation changes over northern and eastern China are the results of changes in large-scale circulation background. Over China, the LGM climate responses to different mechanisms in order of strength from strong to weak are, the large-scale circulation pattern, sea- land distribution, vegetation, CO2 concentration, and earth orbital parameters.展开更多
Using a regional climate model MM5 nested to an atmospheric global climate model CCM3, a series of simulations and sensitivity experiments have been performed to investigate the relative Last Glacial Maximum （LGM） c...Using a regional climate model MM5 nested to an atmospheric global climate model CCM3, a series of simulations and sensitivity experiments have been performed to investigate the relative Last Glacial Maximum （LGM） climate response to different mechanisms over China. Model simulations of the present day （PD） climate and the LGM climate change are in good agreement with the observation data and geological records, especially in the simulation of precipitation change. Under the PD and LGM climate, changes of earth orbital parameters have a small influence on the annual mean temperature over China. However, the magnitude of the effect shows a seasonal pattern, with a significant response in winter. Thus, this influence cannot be neglected. During the LGM, CO2 concentration reached its lowest point to 200 ppmv. This results in a temperature decrease over China. The influences of CO2 concentration on climate show seasonal and regional patterns as well, with a significant influence in winter. On the contrary, CO2 concentration has less impact in summer season. In some cases, temperature even increases with decreasing in CO2 concentration. This temperature increase is the outcome of decrease in cloud amount; hence increase the solar radiation that reached the earth＇s surface. This result suggests that cloud amount plays a very important role in climate change and could direct the response patterns of some climate variables such as temperature during certain periods and over certain regions. In the Tibetan Plateau, the temperature responses to changes of the above two factors are generally weaker than those in other regions because the cloud amount in this area is generally more than in the other areas. Relative to the current climate, changes in orbital parameters have less impact on the LGM climate than changes in CO2 concentration. However, both factors have rather less contributions to the climate change in the LGM. About 3%-10% changes in the annual mean temperature are contributed by CO2.展开更多
Based on the International Satellite Cloud Climatology Project（ISCCP）data in 1983-2006,it is found that there is a high value center of high cloud amount over the Tibetan Plateau（TP）,while there is a high value ce...Based on the International Satellite Cloud Climatology Project（ISCCP）data in 1983-2006,it is found that there is a high value center of high cloud amount over the Tibetan Plateau（TP）,while there is a high value center of middle cloud amount over the Sichuan Basin extending to the coastal area of southeastern China along the same latitude,and a low one over the TP.The present day（PD）and Last Glacial Maximum（LGM）climates are simulated by using the NCAR Community Climate Model（CCM3）nested with a regional mesoscale model（MM5）.Comparing the clouds simulated by MM5 with the ISCCP data,it is found that the main patterns of high and middle clouds over China can be reproduced by MM5,which implies that the climate characteristics of clouds might he dominated by relative humidity.Meanwhile,the vertical distributions of water vapor and temperature are also well simulated by MM5.Furthermore,the hydrological cycle changes between the LGM and PD simulations are examined.The results show that during the LGM,the tropospheric temperature decreases in summer with a high value reduction center in the upper and middle troposphere; in winter,a high value reduction center of temperature appears in the middle troposphere over southern China,while the temperature in the upper and middle troposphere increases over northern China.There obviously exists a positive correlation between the water vapor content and temperature change.The water vapor content mostly decreases with the maximum drop in the near-ground surface layer,but it increases in the upper and middle troposphere over northern China in winter.Changes of water vapor content gradually weaken with the altitude increasing,reaching the minimum in the upper troposphere.The relative humidity can either increase or decrease with the maximum change greater than 15%.It is not conservative on the regional scale,and its change is consistent with the changes of middle and low clouds.During the LGM,the high cloud reduces nationwide except over Southwest China,and the middle and low clouds also decrease with the greatest reduction seen in the low cloud.Precipitation changes correspond to the changes of middle and low clouds.Based on the changes of the relative humidity and effective precipitation,it is found that during the LGM,Southwest China is wetter in summer,so is Northwest China.展开更多
基金financially supported by Beijing 1:50 000 Liulihe,Panggezhuang,Ancixian regional geological survey Projects of China Geological Survey(grant No.12120114007701)
文摘Objective LGM is a critical climate period in the late Quaternary and is the most recent extreme cold event. Clark et al. （2009） used 4271^14C records and 475 cosmogenic nuclide datings to define LGM be in 26.5-19.0 kaBP. LGM age often changes with time in different regions （Mix et al., 2001; Zhang Zhigang et al., 2015）. However, LGM has not been described to date in the Beijing region. During our field work in 2015-2017, LGM event stratigraphy was discovered from sevral boreholes in the middle and lower region of Yongding river basin, Southern Beijing plain.
基金the Hundred Talents Project from the Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant No. 49971075).
文摘LGM climate study is a hot topic in international fields on global changes. Climate simulation in this study applies both common designs of 21 kaBP boundary conditions from the Paleoclimate Modeling Intercomparison Project (PMIP), including insolation, glaciation, sea surface temperature and atmospheric CO2 concentration, and land surface conditions from Eurasia continent by compilation of geological evidence. The simulation outputs are in agreement with climate spatial patterns reconstructed by observation records. Sensitive experiment on land surface conditions shows that changes in vegetation would make significant impacts on temperature and precipitation. Particularly in the Tibetan Plateau, this change would increase in differences of winter and summer temperature, precipitation and P-E.
文摘Chinese lake status database has provided systematic geological records of much higher lake level and fresher water than today at the LGM from western China. This wet condition was significant contrast with very dry conditions in eastern China. Together with lake studies from Eurasian continents, there was a wet-condition belt from the Mediterranean and the Middle East, Central Asia to western China. Palaeoclimate simulations confirmed that the wet conditions in western China were produced by decrease of the evaporation and increase of precipitation by positive anomaly of annual P-E of 70-95 mm/a between the LGM and today. The westerlies enhanced in the strength and shifted southwards-eastwards in the position, and the low thermal conditions in the Eurasian continent creating temperature 4-16℃ lower than today and relatively low evaporation, were the major two important climate conditions to yield cold-wet climates in western China.
基金the National Natural Science Foundation of China under Nos.40231011,90102055,and 40233034
文摘Using a regional climate model MM5 nested to an atmospheric global climate model CCM3, a series of simulations and sensitivity experiments have been performed to investigate the relative LGM climate response to changes of land-sea distribution, vegetation, and large-scale circulation background over China. Model results show that compared with the present climate, the fluctuations of sea-land distribution in eastern Asia during the LGM result in the temperature decrease in winter and increase in summer. It has significant impact on the temperature and precipitation in the east coastal region of China. The impact on precipitation in the east coastal region of China is the most significant one, with 25%-50% decrease in the total precipitation change during the LGM. On the other hand, the changes in sea-land distribution have less influence on the climate of inland and western part of China. During the LGM, significant changes in vegetation result in temperature alternating with winter increase and summer decrease, but differences in the annual mean temperature are minor. During the LGM, the global climate, i.e., the large-scale circulation background has changed significantly. These changes have significant influences on temperature and precipitation over China. They result in considerable temperature decreases in this area, and direct the primary patterns and characteristics of temperature changes. Results display that, northeastern China has the greatest temperature decrease, and the temperature decrease in the Tibetan Plateau is larger than in the eastern part of China located at the same latitude. Moreover, the change of large-scale circulation background also controls the pattern of precipitation change. Results also show that, most of the changes in precipitation over western and northeastern parts of China are the consequences of changing large-scale circulation background, of which 50%-75% of precipitation changes over northern and eastern China are the results of changes in large-scale circulation background. Over China, the LGM climate responses to different mechanisms in order of strength from strong to weak are, the large-scale circulation pattern, sea- land distribution, vegetation, CO2 concentration, and earth orbital parameters.
基金the National Natural Science Foundation of China under Nos.40231011,90102055,and 40233034
文摘Using a regional climate model MM5 nested to an atmospheric global climate model CCM3, a series of simulations and sensitivity experiments have been performed to investigate the relative Last Glacial Maximum （LGM） climate response to different mechanisms over China. Model simulations of the present day （PD） climate and the LGM climate change are in good agreement with the observation data and geological records, especially in the simulation of precipitation change. Under the PD and LGM climate, changes of earth orbital parameters have a small influence on the annual mean temperature over China. However, the magnitude of the effect shows a seasonal pattern, with a significant response in winter. Thus, this influence cannot be neglected. During the LGM, CO2 concentration reached its lowest point to 200 ppmv. This results in a temperature decrease over China. The influences of CO2 concentration on climate show seasonal and regional patterns as well, with a significant influence in winter. On the contrary, CO2 concentration has less impact in summer season. In some cases, temperature even increases with decreasing in CO2 concentration. This temperature increase is the outcome of decrease in cloud amount; hence increase the solar radiation that reached the earth＇s surface. This result suggests that cloud amount plays a very important role in climate change and could direct the response patterns of some climate variables such as temperature during certain periods and over certain regions. In the Tibetan Plateau, the temperature responses to changes of the above two factors are generally weaker than those in other regions because the cloud amount in this area is generally more than in the other areas. Relative to the current climate, changes in orbital parameters have less impact on the LGM climate than changes in CO2 concentration. However, both factors have rather less contributions to the climate change in the LGM. About 3%-10% changes in the annual mean temperature are contributed by CO2.
基金Supported by the National Natural Science Foundation of China under Grant Nos.40231011,90102055,and 40233034
文摘Based on the International Satellite Cloud Climatology Project（ISCCP）data in 1983-2006,it is found that there is a high value center of high cloud amount over the Tibetan Plateau（TP）,while there is a high value center of middle cloud amount over the Sichuan Basin extending to the coastal area of southeastern China along the same latitude,and a low one over the TP.The present day（PD）and Last Glacial Maximum（LGM）climates are simulated by using the NCAR Community Climate Model（CCM3）nested with a regional mesoscale model（MM5）.Comparing the clouds simulated by MM5 with the ISCCP data,it is found that the main patterns of high and middle clouds over China can be reproduced by MM5,which implies that the climate characteristics of clouds might he dominated by relative humidity.Meanwhile,the vertical distributions of water vapor and temperature are also well simulated by MM5.Furthermore,the hydrological cycle changes between the LGM and PD simulations are examined.The results show that during the LGM,the tropospheric temperature decreases in summer with a high value reduction center in the upper and middle troposphere; in winter,a high value reduction center of temperature appears in the middle troposphere over southern China,while the temperature in the upper and middle troposphere increases over northern China.There obviously exists a positive correlation between the water vapor content and temperature change.The water vapor content mostly decreases with the maximum drop in the near-ground surface layer,but it increases in the upper and middle troposphere over northern China in winter.Changes of water vapor content gradually weaken with the altitude increasing,reaching the minimum in the upper troposphere.The relative humidity can either increase or decrease with the maximum change greater than 15%.It is not conservative on the regional scale,and its change is consistent with the changes of middle and low clouds.During the LGM,the high cloud reduces nationwide except over Southwest China,and the middle and low clouds also decrease with the greatest reduction seen in the low cloud.Precipitation changes correspond to the changes of middle and low clouds.Based on the changes of the relative humidity and effective precipitation,it is found that during the LGM,Southwest China is wetter in summer,so is Northwest China.
