By using monthly NCEP/NCAR meridional gridpoint wind data at the levels of 1000, 850, 700, 600, 500, 400, 300, 200, 150 and 100 hPa from 1948 to 2004, the intensity of global cross-equatorial flows is calculated. The ...By using monthly NCEP/NCAR meridional gridpoint wind data at the levels of 1000, 850, 700, 600, 500, 400, 300, 200, 150 and 100 hPa from 1948 to 2004, the intensity of global cross-equatorial flows is calculated. The spatial and temporal variation of global cross-equatorial flows at the 850-hPa level are shown and discussed. The results show that the strength of the 850-hPa global cross-equatorial flows represent obvious long-term variation and interdecadal change during the period. Evidence suggests that the cross-equatorial flow of the passages at 45 - 50 °E in June to August, 105 - 115 °E in May to September, 130 - 140 °E in May to September and May to November and 20 - 25 °E in February to April intensified and that the cross-equatorial flow of the passages at 50 - 35 °W in June to August weaken in the past 57 years, with an increase of 0.25m/s/10a for summer Somali Jet and increase of 0.32 m/s/10a for cross- equatorial flow at 130 - 140 °E in May to September The results of Singular Spectrum Analysis （SSA） for the time series indicate that for the cross-equatorial flow at 850 hPa, the interdecadal and long-term trend changes are 35% - 45%, and the interarmual variation is no more than 30%, in variance contribution. The results also reveal that the interarmual variation of intensity of the summer cross-equatorial flows in the Pacific is significantly correlated with Southern Oscillation. With weak Southern Oscillation, strong crossequatorial flows in Pacific will happen, though the summer Somali Jet is only a little positively correlated with North Atlantic Oscillation （NAO）.展开更多
The relationship between global warming and the variation in tropical cyclone (TC) genesis frequency is analyzed using the data of the Tropical Cyclone Year Book by the China Meteorological Administration and the Nati...The relationship between global warming and the variation in tropical cyclone (TC) genesis frequency is analyzed using the data of the Tropical Cyclone Year Book by the China Meteorological Administration and the National Centers for Environmental Prediction (NCEP) reanalysis data from 1949 to 2007. The observational results indicate that the average sea surface temperature (SST) in the Intertropical Convergence Zone (ITCZ) region (10°N– 20°N, 100°E– 140°E) increases by 0.6°C against the background of global warming, while the frequency of tropical cyclone geneses in this region decreases significantly. Generally, the rise of SSTs is favorable for the genesis of tropical cyclones, but it is now shown to be contrary to the normal effect. Most of the tropical cyclones in the western North Pacific (WNP) are generated in the ITCZ. This is quite different from the case in the Atlantic basin in which the tropical cyclones are mostly generated from the easterly wave. Our research results demonstrate that the ITCZ has a weakening trend in strength, and it has moved much more equatorward in the past 40 years; both are disadvantageous to the formation of tropical cyclones. Furthermore, our study also found that the ridge of the subtropical high tends to shift slightly equatorward, which is another adverse mechanism for the formation of tropical cyclones.展开更多
There is a rainfall variability biennial relationship between Central America （CA） and equatorial South America （ESA） over the tropical western hemisphere, which is known to have arisen due to the combined effects...There is a rainfall variability biennial relationship between Central America （CA） and equatorial South America （ESA） over the tropical western hemisphere, which is known to have arisen due to the combined effects of ENSO and tropical North Atlantic （TNA） SST. Here, the authors report that this biennial rainfall relationship between CA and ESA has weakened remarkably since 2000, with weakening in both in-phase and out-of-phase rainfall transitions. The observed decadal changes in the biennial relationship between CA and ESA rainfall can be attributed to changes in the effects of ENSO and TNA SST since 2000, which may be associated with more frequent occurrences of the central Pacific or＇Modoki＇ type El Ni^o. The weakening of the association with ENSO for CA rainfall since 2000 might have given rise to the weakening of the in-phase rain transition from CA rainfall to the following ESA rainfall. The weakened linkage between boreal-winter ESA rainfall and the subsequent boreal-summer TNA SST since 2000 may have resulted in the weakening of the out- of-phase rainfall transition from boreal-winter ESA rainfall to the subsequent boreal-summer CA rainfall.展开更多
基金Natural Science Foundation of China (40775060)Research Fund for Tropical and MarineMeteorology Key Open Laboratory on Tropical Monsoon, CMA
文摘By using monthly NCEP/NCAR meridional gridpoint wind data at the levels of 1000, 850, 700, 600, 500, 400, 300, 200, 150 and 100 hPa from 1948 to 2004, the intensity of global cross-equatorial flows is calculated. The spatial and temporal variation of global cross-equatorial flows at the 850-hPa level are shown and discussed. The results show that the strength of the 850-hPa global cross-equatorial flows represent obvious long-term variation and interdecadal change during the period. Evidence suggests that the cross-equatorial flow of the passages at 45 - 50 °E in June to August, 105 - 115 °E in May to September, 130 - 140 °E in May to September and May to November and 20 - 25 °E in February to April intensified and that the cross-equatorial flow of the passages at 50 - 35 °W in June to August weaken in the past 57 years, with an increase of 0.25m/s/10a for summer Somali Jet and increase of 0.32 m/s/10a for cross- equatorial flow at 130 - 140 °E in May to September The results of Singular Spectrum Analysis （SSA） for the time series indicate that for the cross-equatorial flow at 850 hPa, the interdecadal and long-term trend changes are 35% - 45%, and the interarmual variation is no more than 30%, in variance contribution. The results also reveal that the interarmual variation of intensity of the summer cross-equatorial flows in the Pacific is significantly correlated with Southern Oscillation. With weak Southern Oscillation, strong crossequatorial flows in Pacific will happen, though the summer Somali Jet is only a little positively correlated with North Atlantic Oscillation （NAO）.
基金Specialized Project on Climate Change by China Meteorological Administration 2008Natural Science Foundation of China (40730948)Typhoon foundation of 2004 (2004STB006) by Shanghai Typhoon Institute
文摘The relationship between global warming and the variation in tropical cyclone (TC) genesis frequency is analyzed using the data of the Tropical Cyclone Year Book by the China Meteorological Administration and the National Centers for Environmental Prediction (NCEP) reanalysis data from 1949 to 2007. The observational results indicate that the average sea surface temperature (SST) in the Intertropical Convergence Zone (ITCZ) region (10°N– 20°N, 100°E– 140°E) increases by 0.6°C against the background of global warming, while the frequency of tropical cyclone geneses in this region decreases significantly. Generally, the rise of SSTs is favorable for the genesis of tropical cyclones, but it is now shown to be contrary to the normal effect. Most of the tropical cyclones in the western North Pacific (WNP) are generated in the ITCZ. This is quite different from the case in the Atlantic basin in which the tropical cyclones are mostly generated from the easterly wave. Our research results demonstrate that the ITCZ has a weakening trend in strength, and it has moved much more equatorward in the past 40 years; both are disadvantageous to the formation of tropical cyclones. Furthermore, our study also found that the ridge of the subtropical high tends to shift slightly equatorward, which is another adverse mechanism for the formation of tropical cyclones.
基金funded by the National Natural Science Foundation of China[grant number 41776031]the Guangdong Natural Science Foundation[grant number 2015A030313796]+3 种基金the National Program on Global Change and Air-Sea Interaction[grant number GASI-IPOVAI-04]the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA11010104]the program for scientific research start-upfunds of Guangdong Ocean Universitythe Foundation for Returned Scholars of the Ministry of Education of China
文摘There is a rainfall variability biennial relationship between Central America （CA） and equatorial South America （ESA） over the tropical western hemisphere, which is known to have arisen due to the combined effects of ENSO and tropical North Atlantic （TNA） SST. Here, the authors report that this biennial rainfall relationship between CA and ESA has weakened remarkably since 2000, with weakening in both in-phase and out-of-phase rainfall transitions. The observed decadal changes in the biennial relationship between CA and ESA rainfall can be attributed to changes in the effects of ENSO and TNA SST since 2000, which may be associated with more frequent occurrences of the central Pacific or＇Modoki＇ type El Ni^o. The weakening of the association with ENSO for CA rainfall since 2000 might have given rise to the weakening of the in-phase rain transition from CA rainfall to the following ESA rainfall. The weakened linkage between boreal-winter ESA rainfall and the subsequent boreal-summer TNA SST since 2000 may have resulted in the weakening of the out- of-phase rainfall transition from boreal-winter ESA rainfall to the subsequent boreal-summer CA rainfall.
