| Study on temporal inequality of precipitation in the loess plateau based on Lorenz curve |
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| DOI：10.7606/j.issn.1000-7601.2012.04.31 |
| Key Words: Lorenz curve Gini coefficient Lorenz asymmetry coefficient Mann-Kendall test |
| Author Name | Affiliation | | SHI Wanli | Research Center for Sustainable Hydropower Development, China Institute of Water Resources and Hydropower Research, Beijing 100038, China | | YANG Qinke | College of Urban and Environmental Science, Northwest U
niversity, Xi'an 710127, China | | LI Xiaofang | Ankang Meteorological Bureau, Ankang, Shaanxi 725000, China | | CHEN Ang | Research Center for Sustainable Hydropower Development, China Institute of Water Resources and Hydropower Research, Beijing 100038, China | | HE Xianjin | Handan Design and Research Institue of Water Conservancy and Hydropower, Handan, Hebei 056002, China |
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| Abstract: |
| Based on the model of precipitation distribution describing with Gini coefficient in Yan'an and Yulin, the annual precipitation, Gini coefficient and Lorenz asymmetry coefficient were analysized for the period of 1961—2010 and the Mann-Kendall test was employed to detect the upward or downward trend in precipitation, Gini coefficient and Lorenz asymmetry coefficient during the study period. The results showed that the annual precipitation in Yan'an and Yulin located in the loess plateau was in a decreasing trend during the past 50 years and mean Gini coefficient was respectively 0.56 and 0.61. The yearly Lorenz asymmetry coefficient (S>1) accounted for a high percentage, 33.3% in Yulin and 16.7% in Yan'an. Yulin showed increasing Gini coefficient and decreasing Lorenz asymmetry coefficient while Yan'an indicated decreasing Gini coefficient and increasing Lorenz asymmetry coefficient, but these trends had no significance at a > 95% confidence level. Therefore, precipitation distribution was becoming more and more uneven in Yulin since greater percentages of the yearly total precipitations in a few very unrainy months. However, the monthly precipitation within one year in Yan'an had a uniform distribution and a greater percentage of the precipitation in a few rainy months. In the three years of 1972, 1986 and 1997 in Yulin, the Lorenz asymmetry coefficient was greater than 1. It indicated that the precipitation inequality was caused by the heavy rainfall in some months of the year which was also the most abnormal year of drought. In conclusion, Lorenz curve from a novel perspective is an available way for evaluating quantitatively the temporal distribution of precipitation and analyzing its causes, which provided scientific basis for the analysis of mechanism of natural disasters like drought and soil loss. |
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