Characteristics of the Main Factors Affecting Prolonged Spring-summer Extreme Drought Events in Northern Drought-prone Belt
Purposes Methods Extreme weather and climate events have been exhibiting an intensification under global warming.This intensified extremity thus augments the damaging impacts on both society and the econo-my.In the Northern Drought-prone Belt(NDPB),extreme drought events are becoming more frequent and more intense with a broader distribution.In this study,by using statistical analysis and composite analysis,characteris-tics of the main factors affecting prolonged spring-summer extreme drought events in NDPB are analyzed based on the meteorological drought composite index,precipitation and near-surface air temperature data observed by meteorological stations,reanalysis dataset,sea surface temperature,snow cover,and the sea ice concentration data.Findings Conclusions Results show that the main circulation factors are as follows:the eastward propagat-ing wave trains from Baffin Bay in March,a"positive-negative-positive-negative-positive-negative"geopoten-tial height anomaly from the south of Hudson Bay to the east of Lake Baikal in May,an eastward wave train near the 60°N latitude,the Silk Road wave train and the eastward,weak Western Pacific Subtropical High in June;the main external forcing factors are listed below:the phase transition from La Niña to El Niño,warmer sea sur-face temperature over the Indian Ocean basin and the central North Atlantic;the shrinking snow cover in the mid-to-high latitudes of Eurasia and between 40°N and 60°N of North America,a snow cover reversal from abnormal-ly high to abnormally low over the Qinghai-Tibet Plateau,a"negative-positive"sea ice concentration anomaly with less near Baffin Bay and Davis Strait but more near Greenland Sea,and a"positive-negative-positive"sea ice concentration anomaly from the Barents Sea to the Kara Sea.
prolonged spring-summer extreme drought eventsinfluencing factorsNorthern Drought-prone Belt
万方数据
维普
