Although Meiyu rainfall has its in-phase spatial variability over the Changjiang-Huaihe River Valley (CHRV) in most years, it is distributed in some years like a seesaw to the north and south of the Changjiang River, ...Although Meiyu rainfall has its in-phase spatial variability over the Changjiang-Huaihe River Valley (CHRV) in most years, it is distributed in some years like a seesaw to the north and south of the Changjiang River, when the precipitation tends to be nearly normal throughout the valley, which would inevitably increase difficulties of making short-term prediction of the rainfall. For this reason, EOF analysis is made on 15 related stations’ precipitation from June to July during 1951─2004, revealing that the EOF2 mode shows largely a north-south seesaw-like pattern, and thereby classifying Meiyu patterns into two types: "northern drought and southern flood (NDSF)" and "northern flood and southern drought (NFSD)". Afterwards, the authors investigated ocean-atmospheric characteristics when these two anomalous types occured using the NCEP reanalysis (version 1) and the extended reconstructed SSTs (version 2). The results show that in the NDSF years, the low-level frontal area and moisture convergence center lie more southward, accompanied by weaker subtropical summer mon- soon over East Asia, with the western Pacific subtropical high and 200 hPa South Asia High being more southward. Both the Northern and Southern Hemisphere Annular Modes are stronger than normal in preceding February; SST is higher off China during boreal winter and spring and the opposite happens in the NFSD years. Also, this seesaw-form Meiyu rainfall distribution might be affected to some degree by the previous ENSO event.展开更多
Attributions of floods/cooler along the Yangtze River Valley anddroughts/warmer in North China for the last 25 years have been reviewed in this paper. Both naturalclimate variability and human activities are considere...Attributions of floods/cooler along the Yangtze River Valley anddroughts/warmer in North China for the last 25 years have been reviewed in this paper. Both naturalclimate variability and human activities are considered. Some stronger evidences contributed to thenatural climate variability, such as decadal and interdecadal variabilities of East Asian summermonsoon, the periodicities and transitions of rainfall and temperature changes in China, abruptclimate change, NAO, AO, AAO, ENSO, and snow cover. The signals produced by the human activitiessuch as greenhouse gases and 'brown clouds' likely play the role for the patterns. But the physicalfeedbacks and mechanisms still keep ambiguous and vague. More researches should be carried out infuture to solve this issue.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 40605022)the National Basic Research Program of China (Grant No. 2006CB403607)the Key Project of the Ministry of Science and Technology, China "South China Sea Monsoon Experiment (SCSMEX)"
文摘Although Meiyu rainfall has its in-phase spatial variability over the Changjiang-Huaihe River Valley (CHRV) in most years, it is distributed in some years like a seesaw to the north and south of the Changjiang River, when the precipitation tends to be nearly normal throughout the valley, which would inevitably increase difficulties of making short-term prediction of the rainfall. For this reason, EOF analysis is made on 15 related stations’ precipitation from June to July during 1951─2004, revealing that the EOF2 mode shows largely a north-south seesaw-like pattern, and thereby classifying Meiyu patterns into two types: "northern drought and southern flood (NDSF)" and "northern flood and southern drought (NFSD)". Afterwards, the authors investigated ocean-atmospheric characteristics when these two anomalous types occured using the NCEP reanalysis (version 1) and the extended reconstructed SSTs (version 2). The results show that in the NDSF years, the low-level frontal area and moisture convergence center lie more southward, accompanied by weaker subtropical summer mon- soon over East Asia, with the western Pacific subtropical high and 200 hPa South Asia High being more southward. Both the Northern and Southern Hemisphere Annular Modes are stronger than normal in preceding February; SST is higher off China during boreal winter and spring and the opposite happens in the NFSD years. Also, this seesaw-form Meiyu rainfall distribution might be affected to some degree by the previous ENSO event.
基金This review was supported by China-IPCC Climate Special Projects and LCS Projects.
文摘Attributions of floods/cooler along the Yangtze River Valley anddroughts/warmer in North China for the last 25 years have been reviewed in this paper. Both naturalclimate variability and human activities are considered. Some stronger evidences contributed to thenatural climate variability, such as decadal and interdecadal variabilities of East Asian summermonsoon, the periodicities and transitions of rainfall and temperature changes in China, abruptclimate change, NAO, AO, AAO, ENSO, and snow cover. The signals produced by the human activitiessuch as greenhouse gases and 'brown clouds' likely play the role for the patterns. But the physicalfeedbacks and mechanisms still keep ambiguous and vague. More researches should be carried out infuture to solve this issue.
