This study investigates the origins of intraseasonal rainfall variations over the southern South China Sea（SCS） region in boreal winter.It is found that intraseasonal rainfall variations over the southern SCS have d...This study investigates the origins of intraseasonal rainfall variations over the southern South China Sea（SCS） region in boreal winter.It is found that intraseasonal rainfall variations over the southern SCS have different origins on the 10-20-day and 30-60-day time scales.On the 10-20-day time scale,large rainfall anomalies over the southern SCS are preceded by strong northerly wind anomalies associated with the East Asian winter monsoon（EAWM）,by about two days.On the 30-60-day time scale,the strong EAWM-related northerly wind anomalies almost appear simultaneously with large rainfall anomalies over the southern SCS.In addition,obvious large rainfall anomalies occur over the southeastern tropical Indian Ocean about one week before the peak southern SCS rainfall anomalies.It indicates that the convection and related circulation anomalies with origins over the tropical Indian Ocean may play an important role in inducing intraseasonal rainfall variations over the southern SCS on the 30-60-day time scale,but not on the 10-20-day time scale.展开更多
The spatial and temporal variations of some important near-surface climate parameters and extreme climate events in North China during 1961-2010 are analyzed by using 94 meteorological stations＇ data in the study are...The spatial and temporal variations of some important near-surface climate parameters and extreme climate events in North China during 1961-2010 are analyzed by using 94 meteorological stations＇ data in the study area. Results show that the annual mean surface air temperature in North China increased at the rate of 0.36℃ per decade, higher than the national average in the same period. Increasing was particularly significant since the mid-1980s, with maximum increase in the middle and northeastern parts of Inner Mongolia. Increasing rate of the annual mean minimum temperature is much higher than that of the maximum temperature, which results in the decrease of the annual mean diurnal temperature range. Noticeable decrease is also observed in the frequency of cold wave. Annual precipitation shows a slight decreasing trend, with more pronounced decrease in southern Shanxi and eastern Hebei provinces, which is mainly represented as decreasing in contribution rates of rainstorm and heavy storm in flood-season （May to September）. During 1961 -2010, North China is characterized by a noticeable reduction in annual extreme precipitation, and an increase in high-temperature days over most parts, as well as more frequent droughts. There are remarkable reductions in annual sunshine duration and mean wind speed, associated with the most significant reduction of mean wind speed in midwestern and eastern parts of Inner Mongolia. Meanwhile, North China has experienced a noticeable decrease/increase in annual mean sanddust/haze days during the study period. However, there is no significant trend in fog days, except a pronounced decrease since the 1990s.展开更多
基金supported by the National Natural Science Foundation of China[grant numbers 41475081,41275081,41505048,41505061,and 41461164005]the State Key Laboratory of Severe Weather Special Fund[grant number 2015LASW-B04]
文摘This study investigates the origins of intraseasonal rainfall variations over the southern South China Sea（SCS） region in boreal winter.It is found that intraseasonal rainfall variations over the southern SCS have different origins on the 10-20-day and 30-60-day time scales.On the 10-20-day time scale,large rainfall anomalies over the southern SCS are preceded by strong northerly wind anomalies associated with the East Asian winter monsoon（EAWM）,by about two days.On the 30-60-day time scale,the strong EAWM-related northerly wind anomalies almost appear simultaneously with large rainfall anomalies over the southern SCS.In addition,obvious large rainfall anomalies occur over the southeastern tropical Indian Ocean about one week before the peak southern SCS rainfall anomalies.It indicates that the convection and related circulation anomalies with origins over the tropical Indian Ocean may play an important role in inducing intraseasonal rainfall variations over the southern SCS on the 30-60-day time scale,but not on the 10-20-day time scale.
基金supported by the Climate Change Special Foundation of China Meteorological Administration(No. CCSF2010-1)
文摘The spatial and temporal variations of some important near-surface climate parameters and extreme climate events in North China during 1961-2010 are analyzed by using 94 meteorological stations＇ data in the study area. Results show that the annual mean surface air temperature in North China increased at the rate of 0.36℃ per decade, higher than the national average in the same period. Increasing was particularly significant since the mid-1980s, with maximum increase in the middle and northeastern parts of Inner Mongolia. Increasing rate of the annual mean minimum temperature is much higher than that of the maximum temperature, which results in the decrease of the annual mean diurnal temperature range. Noticeable decrease is also observed in the frequency of cold wave. Annual precipitation shows a slight decreasing trend, with more pronounced decrease in southern Shanxi and eastern Hebei provinces, which is mainly represented as decreasing in contribution rates of rainstorm and heavy storm in flood-season （May to September）. During 1961 -2010, North China is characterized by a noticeable reduction in annual extreme precipitation, and an increase in high-temperature days over most parts, as well as more frequent droughts. There are remarkable reductions in annual sunshine duration and mean wind speed, associated with the most significant reduction of mean wind speed in midwestern and eastern parts of Inner Mongolia. Meanwhile, North China has experienced a noticeable decrease/increase in annual mean sanddust/haze days during the study period. However, there is no significant trend in fog days, except a pronounced decrease since the 1990s.
