We use 71-yr(1948–2018) reanalysis data to investigate the interdecadal variation in the atmospheric heat source(Q1) over the Tibetan Plateau and surrounding Asian monsoon region(AMTP) and its effect on the Northern ...We use 71-yr(1948–2018) reanalysis data to investigate the interdecadal variation in the atmospheric heat source(Q1) over the Tibetan Plateau and surrounding Asian monsoon region(AMTP) and its effect on the Northern Hemisphere summer circulation. The large-scale circulation driven by Q1 over the AMTP is characterized by a center of convergent(divergent) or low(high) potential wind function in the lower(upper) troposphere. Q1 over the AMTP shows a clear interdecadal variation(with positive–negative–positive phases) and these three phases correspond to the time periods 1948–1972, 1973–2005, and 2006–2018, respectively. The thermal circulation has a corresponding interdecadal variation as a response to the interdecadal variation in Q1. An enhanced Q1 leads to an increase in the conversion of the total potential energy to non-divergent wind kinetic energy via the divergent wind velocity. The maximum conversion occurs in the tropopause. The primary thermal forcing for Q1 is produced by the intense, large volume precipitation of the summer monsoon. This induces a response in the large-scale circulation, leading to largescale divergence patterns. The synergistic effects of Pacific Decadal Oscillation(PDO) and North Atlantic Multidecadal Oscillation(AMO) influence Q1 over the AMTP, which is ultimately responsible for the modulation of variations in the global divergent circulation. The global divergent circulation in summer is therefore essentially a direct thermodynamic circulation driven by the strong Q1 over the AMTP.展开更多
The characteristics of 200 hPa divergent wind and velocity potential have been analysed for four kinds of tropical cyclone tracks having impact on the SOuth China Sea. It is found that the difference of monsoon circul...The characteristics of 200 hPa divergent wind and velocity potential have been analysed for four kinds of tropical cyclone tracks having impact on the SOuth China Sea. It is found that the difference of monsoon circulation in 200 hPa divergence wind field may affect the medium-range movement characteristics of tropical cyclone tracks. Corresponding to the west Pacific subtropical high,the orientation of 200 hPa secondary convergence line and its extension to the west may indicate the variability of track types.The direction of tropical cyclone movement is 2 longitudes west of and parallel to the 200 hPa secondary divergence line.展开更多
基金the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA20100304)Second Tibetan Plateau Scientific Expedition and Research Program (2019QZKK0208)+1 种基金National Natural Science Foundation of China (41790471)National Key Scientific Research Plan of China (2016YFA0602200)。
文摘We use 71-yr(1948–2018) reanalysis data to investigate the interdecadal variation in the atmospheric heat source(Q1) over the Tibetan Plateau and surrounding Asian monsoon region(AMTP) and its effect on the Northern Hemisphere summer circulation. The large-scale circulation driven by Q1 over the AMTP is characterized by a center of convergent(divergent) or low(high) potential wind function in the lower(upper) troposphere. Q1 over the AMTP shows a clear interdecadal variation(with positive–negative–positive phases) and these three phases correspond to the time periods 1948–1972, 1973–2005, and 2006–2018, respectively. The thermal circulation has a corresponding interdecadal variation as a response to the interdecadal variation in Q1. An enhanced Q1 leads to an increase in the conversion of the total potential energy to non-divergent wind kinetic energy via the divergent wind velocity. The maximum conversion occurs in the tropopause. The primary thermal forcing for Q1 is produced by the intense, large volume precipitation of the summer monsoon. This induces a response in the large-scale circulation, leading to largescale divergence patterns. The synergistic effects of Pacific Decadal Oscillation(PDO) and North Atlantic Multidecadal Oscillation(AMO) influence Q1 over the AMTP, which is ultimately responsible for the modulation of variations in the global divergent circulation. The global divergent circulation in summer is therefore essentially a direct thermodynamic circulation driven by the strong Q1 over the AMTP.
文摘The characteristics of 200 hPa divergent wind and velocity potential have been analysed for four kinds of tropical cyclone tracks having impact on the SOuth China Sea. It is found that the difference of monsoon circulation in 200 hPa divergence wind field may affect the medium-range movement characteristics of tropical cyclone tracks. Corresponding to the west Pacific subtropical high,the orientation of 200 hPa secondary convergence line and its extension to the west may indicate the variability of track types.The direction of tropical cyclone movement is 2 longitudes west of and parallel to the 200 hPa secondary divergence line.
