| Drought is one of the most serious natural disasters that which influence on humanbeings. There has a worse trend in drought disaster as the global warming. The Yellow Riverbasin is one of the important agricultural production areas in our country, it is imminently tostudy the regular pattern of the drought which caused a serious losses. Currently, there are alot of methods to research on the drought, but most of the methods couldn’t reflect the degreeof drought roundly, which usually considers the single factor. The palmer drought index cancomprehensively reflect the processing of the drought. Therefore, this paper rectify theoriginal palmer drought index and establish a suitable drought index for the Yellow Riverbasin, in order to study the Drought regular pattern in Yellow River basin.Mainly research results are as follows:(1) This paper rectified the original palmer drought index and established a befittingdrought index for the Yellow River basin on the basis of the runoff data of Yellow River basinand available soil moisture data, etc, which published by the ECMWF.(2) Refer to the "flood and drought in Yellow River basin", this paper draw a comparisonwith the correctional palmer drought index of the Yellow River basin from time and space.From the aspect of time, correctional palmer drought index simulate a higher droughtfrequency in August1965, August1972and July2000; From the aspect of space,drought-high value area is located in parts of Ningxia, Inner Mongolia, Henan and Shandong.The results were in keeping with historical records.(3) Analyze the space-time evolution of drought based on the revised drought index ofthe Yellow River basin.From the aspect of time, it had occurred a large range of mild drought in12months, andother months showed a rising trend in all months except June; moderate drought’s scaleslightly decreased and showed a rising trend in all months except June and July; severedrought’s scale decreased significantly in12month and presented the downward trend inFebruary, march, June and October; extreme drought occurred relatively minimal in12monthand revealed a slightly downward trend in August and September.For periodic variation, mild drought has a primary period of22years; moderate droughthas a primary period of13years; severe drought has a same period as moderate drought;extreme drought has a primary period of28years.From the aspect of space, mild drought frequency spread a wide area, especially the partsof Gansu province is more serious; moderate drought frequency decreased significantlycompared with the former; severe drought are seldom appear in most of area, but meander ofShan’ xi located in the high-frequency area; extreme drought and high frequency area rarelyappear, just only be found in the meander of Shan’ xi, xi county and Xing hai. Through the EOF analysis of the drought at all levels shows that the mild droughtoccurrence frequency in northern Yellow River basin is less than the south, the easternoccurrence frequency is greater than the west, southwest occurrence frequency is less than thenortheast; the moderate drought occurrence frequency in north of the Yellow River basin isgreater than the south; the severe drought occurred frequency in east is slightly greater thanthe west and it occurred more easily only in parts of the northeast; the extreme droughtshowed rarely negative value in the northeast.(4) This paper proposed some pertinent countermeasures based on the result of the studyon the Drought regular pattern in Yellow River basin. |
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