A pair of northeast-southwest-tilted mid-tropospheric ridges and troughs on the continental scale was observed to be the key circulation feature common among wintertime extensive and persistent low tempera-ture events...A pair of northeast-southwest-tilted mid-tropospheric ridges and troughs on the continental scale was observed to be the key circulation feature common among wintertime extensive and persistent low tempera-ture events (EPLTE) in China.During the persistence of such anomalous circulations,the split flow over the inner Asian continent and the influent flow over the southeast-ern coast of China correspond well to the expanded and amplified Siberian high with tightened sea level pressure gradients and hence,a strong,cold advection over south-eastern China.The western Pacific subtropical high tends to expand northward during the early stages of most EPLTEs.展开更多
The splitting of the Northern Hemisphere sub-tropical high (SH) during spring to summer and its possible mechanisms has been analyzed. Results indicate that the splitting of SH occurs over the Bay of Bengal to the Ind...The splitting of the Northern Hemisphere sub-tropical high (SH) during spring to summer and its possible mechanisms has been analyzed. Results indicate that the splitting of SH occurs over the Bay of Bengal to the Indo-China peninsula. However, remarkable contrast exists in the Hadley cell at the lower and upper levels over these sectors during March to May. The land surface sensitive/latent heating both play an important role, and decay the local Hadley cell over the Indo-China peninsula by enhancing the upwelling. In contrast, the dominant land surface sensitive heating over the Bay of Bengal only damages the low-level Hadley cell. Thus, the splitting of SH should occur over the Indo-China peninsula, rather than the Bay of Bengal at lower levels. In addition, the analysis suggests that the faster seasonal snow melting in the east of Indo-China peninsula can enhance the land surface sensitive heating atmosphere and weaken the local Hadley cell, such seasonal change benefits the splitting of the SH.展开更多
With the methods of correlation and composite analyses, Ju et al. discussed the relationship between low-frequency oscillation in the summer monsoon region in East Asia and droughts/floods in the middle and lower reac...With the methods of correlation and composite analyses, Ju et al. discussed the relationship between low-frequency oscillation in the summer monsoon region in East Asia and droughts/floods in the middle and lower reaches of the Yangtze River and found that strong monsoon years usually cause more rain in the region. Studying the interdecadal variation of precipitation in three rain zones over south China, the valley of Yangtze River and north China, Tan et al. showed that mid- and higher- latitude circulation and SST have important effect on the precipitation associated with summer monsoon in east China. With data of north Pacific SST and characteristic subtropical high, Cai et al.discovered that the anomalies of precipitation distribution in rainy seasons were directly affected by the activity of the subtropical high. As shown in an observational study, anti-correlation was found between the rainfall in the middle and lower reaches of the Yangtze River during the Mei-yu season and the frequency of TCs in northwest Pacific, including the South China Sea, in the prime of summer . The less active maritime TCs are, the more southward the westerly zone is over the Asian mid- latitudes. It is favorable for the Southwest Monsoon to transport moisture towards the region the Yangtze and Huaihe Rivers and for frontal rains to stagnate over the middle and lower reaches of the Yangtze, increasing the rainfall during Mei-yu. Otherwise, the mid-latitude westerly is located more northward, frontal rains develop north of the Yangtze River, the Mei-yu season shortens and rainfall decreases. Statistically studying the effect of South China Sea TCs and directionturning TCs on the Mei-yu season from 1980 to 1991, Kang et al.showed that 85% of the TCs had significant effect on Mei-yu and 35% of them would cause it to end. In addition, the Chinese meteorologists have long noted the cut-off role of TCs in the transportation of moisture by Southwest Monsoon to the Mei-yu fronts in the Yangtze and Huaihe Rivers. They found that TCs active offshore China would usually take moisture from the Bay of Bengal and cut off the transportation of moisture and transformation of energy for the frontal areas of Mei-yu, weakening, or even break and end the precipitation （like TC 9106, or Zeke）, but there were few TCs over offshore waters or even the west Pacific when Mei-yu was active. As shown in a numerical study, the disturbance of Zeke triggered a horizontal flow field at lower troposphere that weakened the Southwest Monsoon and further decreased its moisture transportation to the region of Yangtze and Huaihe Rivers and the convergence of moisture flux there. At the same time, the typhoon had indirect impact on the Mei-yu through its effect on the subtropical high.展开更多
Relationship between the variations of West Pacific subtropical high indices in the summer half of the year and preceding SST in North Pacific was examined based on a data set of 1951 2000. The correlation between the...Relationship between the variations of West Pacific subtropical high indices in the summer half of the year and preceding SST in North Pacific was examined based on a data set of 1951 2000. The correlation between the subtropical high indices and preceding SST in the equatorial East Pacific was the strongest among the others, and has great persistency from last autumn to spring. It is indicated that ENSO events appeared about six months earlier than the change of the subtropical high activities, and the subtropical high intensities enhanced (weakened) and western ridge point was westward (eastward) in the year of El Nino (La Nina) events. It was also observed that there were similar interdecadal oscillation and abrupt variations between Nino3 SST, subtropical high intensities and rainfall of rainy season in Fujian. Therefore, experiments were made on rainfall distribution of rainy season in Fujian. The results showed that the distribution was directly affected by the subtropical high activities, pronouncedly caused by ENSO effect.展开更多
The sediment core DGKS9603 collected from the Okinawa Trough was used as research target. By use of unsaturated index U37^k of long-chain alkenone, δ^13C of POC and of planktonic foraminifera (G sacculifer), the evol...The sediment core DGKS9603 collected from the Okinawa Trough was used as research target. By use of unsaturated index U37^k of long-chain alkenone, δ^13C of POC and of planktonic foraminifera (G sacculifer), the evolutions of sea surface temperature and partial pressure of carbon dioxide in the atmosphere during the Holocene were reconstructed in the Okinawa Trough. And in combination of δ^18O of planktonic foraminifera, the relative difference of sea surface salinity during the Holocene was also reconstructed.Consequently, three cooling events (E1-E3) were identified,each of which occurred at 1.7-1.6, 5.1-4.8 and 8.1-7.4kaBP (cal), respectively. Of the three events, E2 and E3 are globally comparable, their occurrence mechanism would be that the main stream of the Kuroshio Current shifted eastward due to the enhanced circulation of the northeastern Pacific Ocean, which was driven in turn by amplified intensity of sunshine and subsequent enhancement of subtropical high pressure; E1 corresponds to the Small Ice-Age Event occurring between 1550 and 1850AD in China. In the Okinawa Trough, E1 might be also related to the eastward shift of main stream of the Kuroshio current driven by powerful Asia winter monsoon.展开更多
基金supported by the National Key Technologies R&D Program of China (Grant No.2009BAC51B02)
文摘A pair of northeast-southwest-tilted mid-tropospheric ridges and troughs on the continental scale was observed to be the key circulation feature common among wintertime extensive and persistent low tempera-ture events (EPLTE) in China.During the persistence of such anomalous circulations,the split flow over the inner Asian continent and the influent flow over the southeast-ern coast of China correspond well to the expanded and amplified Siberian high with tightened sea level pressure gradients and hence,a strong,cold advection over south-eastern China.The western Pacific subtropical high tends to expand northward during the early stages of most EPLTEs.
基金Project "863" (2002AA135360) Key Project from the National Natural Science Foundation ofChina (40135020)+2 种基金 National Natural Science Foundation of China (40375014) Funding Program for OutstandingYoung Teachers from the Ministry of Education Open Project from LASG of the Institute of AtmosphericPhysics of the Chinese Academy of Sciences
文摘The splitting of the Northern Hemisphere sub-tropical high (SH) during spring to summer and its possible mechanisms has been analyzed. Results indicate that the splitting of SH occurs over the Bay of Bengal to the Indo-China peninsula. However, remarkable contrast exists in the Hadley cell at the lower and upper levels over these sectors during March to May. The land surface sensitive/latent heating both play an important role, and decay the local Hadley cell over the Indo-China peninsula by enhancing the upwelling. In contrast, the dominant land surface sensitive heating over the Bay of Bengal only damages the low-level Hadley cell. Thus, the splitting of SH should occur over the Indo-China peninsula, rather than the Bay of Bengal at lower levels. In addition, the analysis suggests that the faster seasonal snow melting in the east of Indo-China peninsula can enhance the land surface sensitive heating atmosphere and weaken the local Hadley cell, such seasonal change benefits the splitting of the SH.
基金Natural Science Foundation of China (40505011) Project of Shanghai Science andTechnology Committee (05DZ05815)
文摘With the methods of correlation and composite analyses, Ju et al. discussed the relationship between low-frequency oscillation in the summer monsoon region in East Asia and droughts/floods in the middle and lower reaches of the Yangtze River and found that strong monsoon years usually cause more rain in the region. Studying the interdecadal variation of precipitation in three rain zones over south China, the valley of Yangtze River and north China, Tan et al. showed that mid- and higher- latitude circulation and SST have important effect on the precipitation associated with summer monsoon in east China. With data of north Pacific SST and characteristic subtropical high, Cai et al.discovered that the anomalies of precipitation distribution in rainy seasons were directly affected by the activity of the subtropical high. As shown in an observational study, anti-correlation was found between the rainfall in the middle and lower reaches of the Yangtze River during the Mei-yu season and the frequency of TCs in northwest Pacific, including the South China Sea, in the prime of summer . The less active maritime TCs are, the more southward the westerly zone is over the Asian mid- latitudes. It is favorable for the Southwest Monsoon to transport moisture towards the region the Yangtze and Huaihe Rivers and for frontal rains to stagnate over the middle and lower reaches of the Yangtze, increasing the rainfall during Mei-yu. Otherwise, the mid-latitude westerly is located more northward, frontal rains develop north of the Yangtze River, the Mei-yu season shortens and rainfall decreases. Statistically studying the effect of South China Sea TCs and directionturning TCs on the Mei-yu season from 1980 to 1991, Kang et al.showed that 85% of the TCs had significant effect on Mei-yu and 35% of them would cause it to end. In addition, the Chinese meteorologists have long noted the cut-off role of TCs in the transportation of moisture by Southwest Monsoon to the Mei-yu fronts in the Yangtze and Huaihe Rivers. They found that TCs active offshore China would usually take moisture from the Bay of Bengal and cut off the transportation of moisture and transformation of energy for the frontal areas of Mei-yu, weakening, or even break and end the precipitation （like TC 9106, or Zeke）, but there were few TCs over offshore waters or even the west Pacific when Mei-yu was active. As shown in a numerical study, the disturbance of Zeke triggered a horizontal flow field at lower troposphere that weakened the Southwest Monsoon and further decreased its moisture transportation to the region of Yangtze and Huaihe Rivers and the convergence of moisture flux there. At the same time, the typhoon had indirect impact on the Mei-yu through its effect on the subtropical high.
基金Research on short-term climate prediction model for rainfall in raining seasons of Fujian Province A Natural Science Foundation project for Fujian Province (D9810010)
文摘Relationship between the variations of West Pacific subtropical high indices in the summer half of the year and preceding SST in North Pacific was examined based on a data set of 1951 2000. The correlation between the subtropical high indices and preceding SST in the equatorial East Pacific was the strongest among the others, and has great persistency from last autumn to spring. It is indicated that ENSO events appeared about six months earlier than the change of the subtropical high activities, and the subtropical high intensities enhanced (weakened) and western ridge point was westward (eastward) in the year of El Nino (La Nina) events. It was also observed that there were similar interdecadal oscillation and abrupt variations between Nino3 SST, subtropical high intensities and rainfall of rainy season in Fujian. Therefore, experiments were made on rainfall distribution of rainy season in Fujian. The results showed that the distribution was directly affected by the subtropical high activities, pronouncedly caused by ENSO effect.
文摘The sediment core DGKS9603 collected from the Okinawa Trough was used as research target. By use of unsaturated index U37^k of long-chain alkenone, δ^13C of POC and of planktonic foraminifera (G sacculifer), the evolutions of sea surface temperature and partial pressure of carbon dioxide in the atmosphere during the Holocene were reconstructed in the Okinawa Trough. And in combination of δ^18O of planktonic foraminifera, the relative difference of sea surface salinity during the Holocene was also reconstructed.Consequently, three cooling events (E1-E3) were identified,each of which occurred at 1.7-1.6, 5.1-4.8 and 8.1-7.4kaBP (cal), respectively. Of the three events, E2 and E3 are globally comparable, their occurrence mechanism would be that the main stream of the Kuroshio Current shifted eastward due to the enhanced circulation of the northeastern Pacific Ocean, which was driven in turn by amplified intensity of sunshine and subsequent enhancement of subtropical high pressure; E1 corresponds to the Small Ice-Age Event occurring between 1550 and 1850AD in China. In the Okinawa Trough, E1 might be also related to the eastward shift of main stream of the Kuroshio current driven by powerful Asia winter monsoon.
