Characteristics of Spatio-Temporal Distribution of Spring and Autumn Precipitation in Henan Province

To achieve more effective operation, the climate background of the target area must be understood when conducting artificial precipitation enhancement operations. A total of 114 meteorological stations in Henan Province were partitioned by cluster analysis with the statistical test method on the basis of precipitation data of April and October during 1971-2001. The regional characteristics of temporal and spatial distributions of precipitation and their variation tendency in this province were then analyzed by precipitation anomaly percentage, precipitation intensity, and number of rain days. The distributions of precipitation and rain days of April and October showed remarkable regional characteristics, increasing from north to south and from northeast to southwest. The regional feature of monthly rainfall was determined mainly by the distribution of rain days with an increase tendency from north to south, in which the increase of moderate rain days plays a decisive role. The yearly variation trends of precipitation and rain days of April in each partitioned area decreased during the 31-year period, and the yearly variation trends of precipitation of October in all partitioned areas are decreased. However, the rain days with different intensities in October showed a different yearly trend; those with weak intensities in individual areas trended to increase. Among the 31 years, dry years and insignificant rain years were dominant both in April and October, and the days of little or no rain occurred often. A comparison of the distributions of precipitation and rain days in the six partitioned areas of April revealed that Area 1 and Area 5, which are located in the northern and southern parts of Henan Province, respectively, had most frequent drought occurrence; and the remaining areas showed similar frequencies of drought occurrences during the dry years. Area 5 had the most rain days with varied rain intensity, while Area 1 had the least. For the distributions of precipitation and rain days of the four partitioned areas of October, Area 1 showed the highest frequency of drought and flood occurrences; the remaining areas showed similar frequencies of drought occurrences during the dry years. Area 4, which is located in the southern part of Henan Province, had the most rain days, while Area 1 has the least. The results of this study can provide an important reference for the layout, planning, and effectiveness evaluation of artificial rain enhancement projects.