基于质心分析的我国降水时空演变特征

Spatial and Temporal Variations of Precipitation in China Based on Centroid Principle

通过引入年内唯一的特征时间点——年降水质心时间,即年降水过程线和时间轴间面域几何质心的时间轴投影,解决了频域规律识别不能反映降水事件发生时间的难题。根据年降水质心时间的时域、空域、频域规律,定量识别出我国降水时空演变规律。研究认为:(1)质心时间对大雨及以上等级降水发生时间的响应较为敏感;(2)空间变化规律与主雨季峰值降水时间的空间分布较一致,从西北至东南呈现"早-晚-早"规律;(3)时间序列多为纯随机过程,且非随机特性以周期性为主,趋势性以提前趋势为主,非随机性站点显著聚集于华中、华北地区;(4)年内各等级的时间分布不一致,大雨及以上等级发生时间晚于其它等级,微雨等级降水年内分布最不稳定;(5)年内降水愈不均匀的地区,年际变异愈加显著,即该区域年内主要降水过程的时间分布愈加不稳定。

The unique characteristic time in a year,known as centroid time of annual precipitation,was introduced to solve the problem of identifying occurrence time of precipitation by frequency domain analysis.The centroid time is the time projection of annual precipitation process line and domain geotroid.The spatial,temporal,and frequency domain characteristics of centroid time of annual precipitation were analyzed to identify the spatial and temporal variations of precipitation quantitatively in China.The results suggested that（1）the centroid time is sensitive to the response of the occurrence time of heavy precipitation;（2）the spatial variation of centroid time is consistent with that of peak precipitation time of rainy season,showing ＂early-late-early＂ characteristics from northwest to southeast;（3）the time series of centroid time of the primary meteorological stations are pure random process with the non-random process is mainly shown at the stations located in central and northern China.The nonrandom characteristics are mainly periodicity,and the trend characteristics are mainly advanced trend;（4）the temporal distribution of precipitation grades are not even.The occurrence time of heavy precipitation is later than that of other precipitation grades,and the intra-annual distribution of moderate and light precipitation is the most unstable;and（5）the more uneven of intra-annual precipitation distribution,the more obvious of inter-annual variation of centroid time,indicating the unstable temporal distribution of precipitation in this area.