关键词: 林分空间结构, 距离法, 密度估计, 空间分布格局, 角尺度

Abstract: Based on the 1961-2009 hourly precipitation data from 162 meteorological stations in Huaihe River Basin, this paper analyzed the basic characteristics and spatiotemporal patterns of day and night precipitation in the Basin by the methods of linear trend estimation, REOF analysis, power spectrum, and Mann-Kendall test. The annual day and night precipitation in the Basin varied greatly in different regions, being higher in the south while lower in the north. The annual precipitation and the precipitation days at nighttime were slightly more than those at daytime, but the day and night precipitation had significant difference in intensity in different seasons. Due to the climate change, the day and night precipitation patterns had obvious change. The annual nighttime precipitation presented an increasing trend in most regions, whereas the daytime precipitation decreased in the east while increased in the west of the Basin. The REOF analysis showed the spatial modes of the annual day and night precipitation could be divided into six anomaly regions, i.e., northeast, north-central, northwest, east, west, and south. The annual day and night precipitation showed the same main oscillation period of about 7-9 years, and the second oscillation period of the daytime precipitation was about 2 years. The Mann-Kendall test indicated that the daytime precipitation experienced a mutation of decrease and the nighttime precipitation experienced a mutation of increase, but not passed the reliability test at 0.05.

Key words: stand spatial structure, distance sampling, density estimation, spatial pattern, uniform angle index.