摘要
Based on the daily δ^(18)O data in June―September 2003 at Lijiang and the daily mean NCEP/ NCAR reanalysis data, synoptic-scale variation of δ^(18)O in summer monsoon rainfall was investigated. The 'precipitation amount effect' is obvious for the daily δ^(18)O variation, whereas the 'temperature effect' is insignificant. Alternate occurrences of active phase and break phase of the southwest monsoon probably influence the synoptic-scale δ^(18)O variation prominently. Moreover, the isotopic composition in precipitation during the late monsoon months is presumably influenced significantly by recycling of monsoon precipitation. Both the above factors disturb the 'amount effect' of isotopic variation in the monsoon region. This study also indicates that the synoptic-scale rainfall δ^(18)O variation at Lijiang in summer is domi-nated by the Indian monsoon depression (low pressure) system at large scale. These results are important for further studying the 'amount effect' and reconstructing paleoclimate in the monsoon region.
Based on the daily δ^18O data in June-September 2003 at Lijiang and the daily mean NCEP/ NCAR reanalysis data, synoptic-scale variation of δ^18O in summer monsoon rainfall was investigated. The ‘precipitation amount effect’ is obvious for the daily δ^18O variation, whereas the ‘temperature effect’ is insignificant. Alternate occurrences of active phase and break phase of the southwest monsoon probably influence the synoptic-scale δ^18O variation prominently. Moreover, the isotopic composition in precipitation during the late monsoon months is presumably influenced significantly by recycling of monsoon precipitation. Both the above factors disturb the ‘amount effect’ of isotopic variation in the monsoon region. This study also indicates that the synoptic-scale rainfall δ^18O variation at Lijiang in summer is dominated by the Indian monsoon depression （low pressure） system at large scale. These results are important for further studying the ‘amount effect’ and reconstructing paleoclimate in the monsoon region.
基金
This study was supported by the National Natural Science Foundation of China(Grant Nos.40501014,90511007 and 90302006)
the National Basic Research Program of China(Grant No.2005CB422003)
the Project for 0utstanding Young Scientists of the Natural Science Foundation of China(Grant No.40121101).
