A singular value decomposition （SVD） analysis is carried out to reveal the relationship between the interannual variation of track and intensity of the western North Pacific tropical cyclones （WNPTCs） in the tropi...A singular value decomposition （SVD） analysis is carried out to reveal the relationship between the interannual variation of track and intensity of the western North Pacific tropical cyclones （WNPTCs） in the tropical cyclone （TC） active season （July–November） and the global net air-sea heat flux （Q net ） in the preceding season （April–June）. For this purpose, a tropical cyclone track and intensity function （TIF） is defined by a combination of accumulated cyclone energy （ACE） index and a cyclone track density function. The SVD analysis reveals that the first mode is responsible for the positive correlation between the upward heat flux in the tropical central Pacific and the increased activity of western North Pacific （WNP） TIF, the second mode for the positive correlation between the upward heat flux in the North Indian Ocean and the northeastward track shift of WNPTCs and the third mode for the negative correlation between the upward heat flux in mid-latitude central Pacific and the northwest displacement of the WNP TC-active center. This suggests that Q net anomalies in some key regions have a substantial remote impact on the WNP TC activity.展开更多
The effects of freshwater flux （FWF） on modulating ENSO have been of great interest in recent years. Large FWF bias is evident in Coupled General Circulation Models （CGCMs）, especially over the tropical Pacific wh...The effects of freshwater flux （FWF） on modulating ENSO have been of great interest in recent years. Large FWF bias is evident in Coupled General Circulation Models （CGCMs）, especially over the tropical Pacific where large precipitation bias exists due to the so-called ＂double ITCZ＂ problem. By applying an empirical correction to FWF over the tropical Pacific, the sensitivity of ENSO variability is investigated using the new version （version 1.0） of the NCAR＇s Community Earth System Model （CESM1.0）, which tends to overestimate the interannual variability of ENSO accompanied by large FWF into the ocean. In response to a small adjustment of FWF, interannual variability in CESM1.0 is reduced significantly, with the amplitude of FWF being reduced due to the applied adjustment part whose sign is always opposite to that of the original FWF field. Furthermore, it is illustrated that the interannual variability of precipitation weakens as a response to the reduced interannual variability of SST. Process analysis indicates that the interannual variability of SST is damped through a reduced FWF-salt-density-mixing-SST feedback, and also through a reduced SST-wind-thermocline feedback. These results highlight the importance of FWF in modulating ENSO, and thus should be adequately taken into account to improve the simulation of FWF in order to reduce the bias of ENSO simulations by CESM.展开更多
This review provides a synopsis of the major progress that has been made in monsoon studies in China and to further bridge the gap between the Chinese and international meteorological community. It consists of seven m...This review provides a synopsis of the major progress that has been made in monsoon studies in China and to further bridge the gap between the Chinese and international meteorological community. It consists of seven major sections. After the introduction, the second section begins with the global monsoon systems and their seasonal variation, based on some new methods proposed in recent years. Besides, some major intraseasonal features of East Asian monsoon, including the onset of South China Sea summer monsoon are discussed. In the third section, we review the interactions between ENSO and the East Asian monsoon, focusing in particular on the results of Chinese meteorologists that indicate the influence of ENSO on the East Asian summer monsoon（EASM） is obviously different from that on the tropical monsoon. Besides the tropical Pacific,other ocean basins, such as the Indian Ocean and the Atlantic Ocean, are also important to the East Asian monsoon, and this topic is discussed in the fourth section. In the fifth section, we address the role of land surface processes in East Asian monsoon. For example, we describe work that has shown more snow cover in spring on the Tibetan Plateau is followed by a weakened EASM and more summer rainfall in the Yangtze River valleys. The sixth section focuses on the influence of atmospheric circulation in the Southern Hemisphere（SH） on EASM, demonstrating how the signal from the SH is likely to provide new clues for the seasonal forecasting of summer rainfall in China. Finally, in the seventh section, we concentrate on the interdecadal variations of EASM. In particular, we look at a significant interdecadal variation that occurred at the end of the 1970 s, and how our understanding of this feature could affect forecasting ability.展开更多
In this study, three tropical cyclones （TCs） that passed through the Taiwan Strait were analyzed; our results show that precipitation is not directly related to the intensity of TCs. From the perspective of water bu...In this study, three tropical cyclones （TCs） that passed through the Taiwan Strait were analyzed; our results show that precipitation is not directly related to the intensity of TCs. From the perspective of water budget, moisture flux convergence was dominant and contributed -70% of the moisture for TC precipitation over the ocean and almost all over the land, especially inside the TC circulation. Their spatial distributions were also similar. Evaporation contributed -30% of the moisture for precipitation over the ocean but changed little with the time. Moisture flux convergence can be divided into two parts： wind convergence and moisture advection. Moisture flux convergence was mostly due to wind convergence, which was dominant in the southwestern quadrants of the TCs. Moisture advection was located in the northern area, and becomes relatively important when the TCs approached the land. The moisture flux convergence and its two parts varied during TC movement, with strengthening and contraction of moisture convergence present near landfall. The vertical structure of the three TC eases all indicated that the moisture convergence was mainly confined to the lower atmosphere under 800 hPa and a weak divergence region was present in the middle troposphere around 550 hPa.展开更多
基金The National Key Basic Research Program of China under Grant No.2009CB421404the National Natural Science Foundation of China-Regional Cooperation Project under Grant No.40921160379+1 种基金the National Natural Science foundation of China under Grant No.40730951the Fundamental Research Funds for the Central Universities under Grant No.11lgjc10
文摘A singular value decomposition （SVD） analysis is carried out to reveal the relationship between the interannual variation of track and intensity of the western North Pacific tropical cyclones （WNPTCs） in the tropical cyclone （TC） active season （July–November） and the global net air-sea heat flux （Q net ） in the preceding season （April–June）. For this purpose, a tropical cyclone track and intensity function （TIF） is defined by a combination of accumulated cyclone energy （ACE） index and a cyclone track density function. The SVD analysis reveals that the first mode is responsible for the positive correlation between the upward heat flux in the tropical central Pacific and the increased activity of western North Pacific （WNP） TIF, the second mode for the positive correlation between the upward heat flux in the North Indian Ocean and the northeastward track shift of WNPTCs and the third mode for the negative correlation between the upward heat flux in mid-latitude central Pacific and the northwest displacement of the WNP TC-active center. This suggests that Q net anomalies in some key regions have a substantial remote impact on the WNP TC activity.
基金supported by the National Natural Science Foundation of China (Grant Nos.41230527 and 41375065)the National Basic Research Program of China (Grant No.2010CB950403)
文摘The effects of freshwater flux （FWF） on modulating ENSO have been of great interest in recent years. Large FWF bias is evident in Coupled General Circulation Models （CGCMs）, especially over the tropical Pacific where large precipitation bias exists due to the so-called ＂double ITCZ＂ problem. By applying an empirical correction to FWF over the tropical Pacific, the sensitivity of ENSO variability is investigated using the new version （version 1.0） of the NCAR＇s Community Earth System Model （CESM1.0）, which tends to overestimate the interannual variability of ENSO accompanied by large FWF into the ocean. In response to a small adjustment of FWF, interannual variability in CESM1.0 is reduced significantly, with the amplitude of FWF being reduced due to the applied adjustment part whose sign is always opposite to that of the original FWF field. Furthermore, it is illustrated that the interannual variability of precipitation weakens as a response to the reduced interannual variability of SST. Process analysis indicates that the interannual variability of SST is damped through a reduced FWF-salt-density-mixing-SST feedback, and also through a reduced SST-wind-thermocline feedback. These results highlight the importance of FWF in modulating ENSO, and thus should be adequately taken into account to improve the simulation of FWF in order to reduce the bias of ENSO simulations by CESM.
基金supported by the Chinese Academy of Sciences (Grant No. XDA05110201)the National Natural Science Foundation of China (Grant No. 41475052)
文摘This review provides a synopsis of the major progress that has been made in monsoon studies in China and to further bridge the gap between the Chinese and international meteorological community. It consists of seven major sections. After the introduction, the second section begins with the global monsoon systems and their seasonal variation, based on some new methods proposed in recent years. Besides, some major intraseasonal features of East Asian monsoon, including the onset of South China Sea summer monsoon are discussed. In the third section, we review the interactions between ENSO and the East Asian monsoon, focusing in particular on the results of Chinese meteorologists that indicate the influence of ENSO on the East Asian summer monsoon（EASM） is obviously different from that on the tropical monsoon. Besides the tropical Pacific,other ocean basins, such as the Indian Ocean and the Atlantic Ocean, are also important to the East Asian monsoon, and this topic is discussed in the fourth section. In the fifth section, we address the role of land surface processes in East Asian monsoon. For example, we describe work that has shown more snow cover in spring on the Tibetan Plateau is followed by a weakened EASM and more summer rainfall in the Yangtze River valleys. The sixth section focuses on the influence of atmospheric circulation in the Southern Hemisphere（SH） on EASM, demonstrating how the signal from the SH is likely to provide new clues for the seasonal forecasting of summer rainfall in China. Finally, in the seventh section, we concentrate on the interdecadal variations of EASM. In particular, we look at a significant interdecadal variation that occurred at the end of the 1970 s, and how our understanding of this feature could affect forecasting ability.
基金grants from the 908 Special Projects of China，the National Basic Research Program of China，the Special Scientific Research Project for Public Interest，the National Natural Science Foundation of China
文摘In this study, three tropical cyclones （TCs） that passed through the Taiwan Strait were analyzed; our results show that precipitation is not directly related to the intensity of TCs. From the perspective of water budget, moisture flux convergence was dominant and contributed -70% of the moisture for TC precipitation over the ocean and almost all over the land, especially inside the TC circulation. Their spatial distributions were also similar. Evaporation contributed -30% of the moisture for precipitation over the ocean but changed little with the time. Moisture flux convergence can be divided into two parts： wind convergence and moisture advection. Moisture flux convergence was mostly due to wind convergence, which was dominant in the southwestern quadrants of the TCs. Moisture advection was located in the northern area, and becomes relatively important when the TCs approached the land. The moisture flux convergence and its two parts varied during TC movement, with strengthening and contraction of moisture convergence present near landfall. The vertical structure of the three TC eases all indicated that the moisture convergence was mainly confined to the lower atmosphere under 800 hPa and a weak divergence region was present in the middle troposphere around 550 hPa.
