摘要
The NCEP data were applied to analyze causes of 'late spring coldness' occurring twice in Dalian in late April and mid May of 2008.The results showed that the 500 hPa Baikal ridge of high pressure maintained or strengthened in a stable manner.The delivery of accumulated cold air toward southeast was along the northwest airstream before the ridge.Therefore,the ridge of high pressure over Lake Baikal provided access for the cold air southward so that the cold air could continue to decline,resulting in the appearance of low temperature in late April and formation of 'late spring coldness'.The Northeast cold vortex(NECV) occurred frequently in mid May.There was a high possibility for low temperature and pluvial damages over Dalian.Thus the phenomenon of 'late spring coldness' appeared again.
The NCEP data were applied to analyze causes of 'late spring coldness' occurring twice in Dalian in late April and mid May of 2008.The results showed that the 500 hPa Baikal ridge of high pressure maintained or strengthened in a stable manner.The delivery of accumulated cold air toward southeast was along the northwest airstream before the ridge.Therefore,the ridge of high pressure over Lake Baikal provided access for the cold air southward so that the cold air could continue to decline,resulting in the appearance of low temperature in late April and formation of 'late spring coldness'.The Northeast cold vortex(NECV) occurred frequently in mid May.There was a high possibility for low temperature and pluvial damages over Dalian.Thus the phenomenon of 'late spring coldness' appeared again.
