1961-2021年河北省降水变率特征及其影响因子分析

Analysis of precipitation variability characteristics in Hebei province and the impact factors during 1961-2021

利用1961—2021年河北省71个观测站逐月降水资料和NCEP/NCAR再分析资料,采用回归分析、趋势分析等对河北省不同气象地理区划降水相对变率的时空变化特征及相关因子进行分析。结果表明:不同时间尺度的降水相对变率存在明显差异,时间尺度越小,其相对变率越大。季尺度降水相对变率大于年尺度,月尺度降水相对变率大于季尺度。河北省年降水相对变率为14.9%,全省变化范围为13.5%~29.8%,其中,平原地区相对其他区域年降水相对变率较大,坝上地区相对较小。趋势变化上,除坝上地区外,北部山区、西部山区、沿海地区和平原地区的年降水相对变率逐5 a变化呈减少趋势。海拔高度、城市化进程、大气环流等因素对河北省降水稳定性有明显影响。当海拔高度低,城市化程度低,200 hPa风场在40°N附近出现纬向西风正异常,850 hPa风场表现为气旋-反气旋-气旋系统相间的纬向分布特征,并伴有激烈的上升下沉运动的环流形势场时,会导致河北省降水量变化不规律。

Based on the monthly precipitation data from 71 observation stations in Hebei Province from 1961 to 2021 and the NCEP/NCAR reanalysis data,the temporal and spatial variability characteristics and associated factors of precipitation relative variability were analyzed for different climatic subregions of Hebei province through regression analysis and trend analysis.The results indicate that there are significant differences in precipitation relative variabilities across different timescales,with smaller timescales exhibiting larger relative variability.That is,the seasonal precipitation relative variability is greater than that of annual precipitation,which is lower than that of monthly precipitation.The annual precipitation relative variability in Hebei province ranges from 13.5%to 29.8%,with an average of 14.9%.Among the different subregions,the plain areas exhibit greater annual precipitation relative variability,while the Bashang region shows relatively smaller variability.Besides,except for the Bashang region,it shows decreasing trends in the 5 years changes of annual precipitation relative variability over the northern mountainous region,western mountainous region,coastal region,and plain region.Factors such as altitude,urbanization,and atmospheric circulation have significant impacts on the precipitation stability in Hebei province.When the low altitude and low urbanization are accompanied by a westerly wind anomaly at 200 hPa near 40°N and a zonal distribution of cyclonic-anticyclonic-cyclonic systems at 850 hPa,the strong ascending or descending motion circulations may lead to irregular precipitation variability in Hebei province.