Spatial and Temporal Variations of Precipitation in China Based on Centroid Principle
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Abstract:
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 non-random 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.