Land surface heating of the Tibetan Plateau (TP) plays an important role in the Asian Monsoon system. In this study, the interannual variability of the sensible heat flux over the TP and its connection with the summer...Land surface heating of the Tibetan Plateau (TP) plays an important role in the Asian Monsoon system. In this study, the interannual variability of the sensible heat flux over the TP and its connection with the summer monsoon intensity and onset date was examined based on the newly released land "reanalysis" data, produced by NASA Global Land Data Assimilation System. Although correlation analyses don't show a significant relevance to the summer monsoon intensity, the interannual anomalies in sensible heating near the south flank of the TP indicate a weak reversal in the relationship with the onset date of the West Pacific East Asian monsoon. A diagnostic study shows that above (below) normal sensible heating over the south flake of the TP will lead to rapid (slow) warming of the upper air column over the TP and early (later) reversal of (overturn) the meridional temperature gradient and the vertical wind shear. This will further lead to an earlier (later) onset of the Asian Monsoon.展开更多
In this study,the Weather Research and Forecasting(WRF)model and meteorological observation data were used to research the long-distance moisture transport supply source of the extreme rainfall event that occurred on ...In this study,the Weather Research and Forecasting(WRF)model and meteorological observation data were used to research the long-distance moisture transport supply source of the extreme rainfall event that occurred on July 21,2012 in Beijing.Recording a maximum rainfall amount of 460 mm in 24 h,this rainstorm event had two dominant moisture transport channels.In the early stage of the rainstorm,the first channel comprised southwesterly monsoonal moisture from the Bay of Bengal(BOB)that was directly transported to north China along the eastern edge of Tibetan Plateau(TP)by orographic uplift.During the rainstorm,the southwesterly moisture transport was weakened by the transfer of Typhoon Vicente.Moreover,the southeasterly moisture transport between the typhoon and western Pacific subtropical high(WPSH)became another dominant moisture transport channel.The moisture in the lower troposphere was mainly associated with the southeasterly moisture transport from the South China Sea and the East China Sea,and the moisture in the middle troposphere was mainly transported from the BOB and Indian Ocean.The control experiment well reproduced the distribution and intensity of rainfall and moisture transport.By comparing the control and three sensitivity experiments,we found that the moisture transported from Typhoon Vicente and a tropical cyclone in the BOB both significantly affected this extreme rainfall event.After Typhoon Vicente was removed in a sensitivity experiment,the maximum 24-h accumulated rainfall in north China was reduced by approximately 50%compared with that of the control experiment,while the rainfall after removing the tropical cyclone was reduced by 30%.When both the typhoon and tropical cyclone were removed,the southwesterly moisture transport was enhanced.Moreover,the sensitivity experiment of removing Typhoon Vicente also weakened the tropical cyclone in the BOB.Thus,the moisture pump driven by Typhoon Vicente played an important role in maintaining and strengthening the tropical cyclone in the BOB through its westerly airflow.Typhoon Vicente was not only the moisture transfer source for the southwesterly monsoonal moisture but also affected the tropical cyclone in the BOB,which was a key supply source of long-distance moisture transport for the extreme rainfall event on July21,2012 in Beijing.展开更多
Using NCEP/NCAR R2 reanalysis daily data and daily meteorologicalobservational data of southwest China in 2010, this paper studied the submonthlytimescale oscillation characteristics of the East Asian winter monsoon (...Using NCEP/NCAR R2 reanalysis daily data and daily meteorologicalobservational data of southwest China in 2010, this paper studied the submonthlytimescale oscillation characteristics of the East Asian winter monsoon (EAWM) and itseffect on the temperature of southwest China in 2010 by bandpass filtering, wavelettransformation, composite analysis and correlation analysis. The main conclusions areas follows: The EAWM in 2010 was dominated by low-frequency oscillations of about 7-,12-, and 30-day periods. There existed obviously negative correlation between theEAWM and the winter temperature in southwest China on submonthly, quasi-weeklyand quasi-biweekly timescales, and negative correlation was more obvious on thequasi-biweekly than the quasi-weekly timescale. There was significant difference in thedistribution of high, middle and low layer of the troposphere when the EAWM was onthe submonthly, quasi-one-week and quasi-two-week timescales in the positive andnegative phase. In the positive EAWM phase, the upper-level subtropical westerly jet isstronger and the East Asia trough is deeper, thus it is favorable for the dominance ofmore powerful north wind and lower temperature in southwest China. On the contrary,in the negative EAWM phase, the upper-level subtropical westerly jet is weaker and theEast Asia trough is shallower, thus unfavorable for the north wind and lowertemperature in southwest China.展开更多
基金partially supported by the National Public Benefit Research Foundation (No.GYHY200906018)an open project of the Institute of Plateau Meteorology
文摘Land surface heating of the Tibetan Plateau (TP) plays an important role in the Asian Monsoon system. In this study, the interannual variability of the sensible heat flux over the TP and its connection with the summer monsoon intensity and onset date was examined based on the newly released land "reanalysis" data, produced by NASA Global Land Data Assimilation System. Although correlation analyses don't show a significant relevance to the summer monsoon intensity, the interannual anomalies in sensible heating near the south flank of the TP indicate a weak reversal in the relationship with the onset date of the West Pacific East Asian monsoon. A diagnostic study shows that above (below) normal sensible heating over the south flake of the TP will lead to rapid (slow) warming of the upper air column over the TP and early (later) reversal of (overturn) the meridional temperature gradient and the vertical wind shear. This will further lead to an earlier (later) onset of the Asian Monsoon.
基金National Natural Science Foundation of China(91937301,42030611)Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0103,2019QZKK0105)Scientific and Technological Research Program of China Railway Eryuan Engineering Group CO.LTD(KYY2020066(20-22))
文摘In this study,the Weather Research and Forecasting(WRF)model and meteorological observation data were used to research the long-distance moisture transport supply source of the extreme rainfall event that occurred on July 21,2012 in Beijing.Recording a maximum rainfall amount of 460 mm in 24 h,this rainstorm event had two dominant moisture transport channels.In the early stage of the rainstorm,the first channel comprised southwesterly monsoonal moisture from the Bay of Bengal(BOB)that was directly transported to north China along the eastern edge of Tibetan Plateau(TP)by orographic uplift.During the rainstorm,the southwesterly moisture transport was weakened by the transfer of Typhoon Vicente.Moreover,the southeasterly moisture transport between the typhoon and western Pacific subtropical high(WPSH)became another dominant moisture transport channel.The moisture in the lower troposphere was mainly associated with the southeasterly moisture transport from the South China Sea and the East China Sea,and the moisture in the middle troposphere was mainly transported from the BOB and Indian Ocean.The control experiment well reproduced the distribution and intensity of rainfall and moisture transport.By comparing the control and three sensitivity experiments,we found that the moisture transported from Typhoon Vicente and a tropical cyclone in the BOB both significantly affected this extreme rainfall event.After Typhoon Vicente was removed in a sensitivity experiment,the maximum 24-h accumulated rainfall in north China was reduced by approximately 50%compared with that of the control experiment,while the rainfall after removing the tropical cyclone was reduced by 30%.When both the typhoon and tropical cyclone were removed,the southwesterly moisture transport was enhanced.Moreover,the sensitivity experiment of removing Typhoon Vicente also weakened the tropical cyclone in the BOB.Thus,the moisture pump driven by Typhoon Vicente played an important role in maintaining and strengthening the tropical cyclone in the BOB through its westerly airflow.Typhoon Vicente was not only the moisture transfer source for the southwesterly monsoonal moisture but also affected the tropical cyclone in the BOB,which was a key supply source of long-distance moisture transport for the extreme rainfall event on July21,2012 in Beijing.
文摘Using NCEP/NCAR R2 reanalysis daily data and daily meteorologicalobservational data of southwest China in 2010, this paper studied the submonthlytimescale oscillation characteristics of the East Asian winter monsoon (EAWM) and itseffect on the temperature of southwest China in 2010 by bandpass filtering, wavelettransformation, composite analysis and correlation analysis. The main conclusions areas follows: The EAWM in 2010 was dominated by low-frequency oscillations of about 7-,12-, and 30-day periods. There existed obviously negative correlation between theEAWM and the winter temperature in southwest China on submonthly, quasi-weeklyand quasi-biweekly timescales, and negative correlation was more obvious on thequasi-biweekly than the quasi-weekly timescale. There was significant difference in thedistribution of high, middle and low layer of the troposphere when the EAWM was onthe submonthly, quasi-one-week and quasi-two-week timescales in the positive andnegative phase. In the positive EAWM phase, the upper-level subtropical westerly jet isstronger and the East Asia trough is deeper, thus it is favorable for the dominance ofmore powerful north wind and lower temperature in southwest China. On the contrary,in the negative EAWM phase, the upper-level subtropical westerly jet is weaker and theEast Asia trough is shallower, thus unfavorable for the north wind and lowertemperature in southwest China.
