Abstract:

The meteorological data from 19 meteorological stations of the Dongting watershed during 1961-2009 were chosen. NCC2CI and CInew are improved form of the traditional CI. NCC2CI is an improved form of the traditional CI in the accumulatedrainfallweight, while the CInew is equivalent to change the SPI30 and M30, which are part of NCC2CI, into SPI90 and M90. The calculation principle of this three drought index is simple synthesis of the standard precipitation index and relative moisture index. This study investigates the applicability of three comprehensive meteorological drought indexes (traditional CI, NCC2CI, CInew) in the Dongting Lake basin, from the unreasonable jump point, the statistical characteristics, the process of sitedrought, the process of regionaldrought and spatial distribution, and so on. Results showed that CInew and NCC2CI could be good solution to the problems such as the unreasonable shocks, the unreasonable increased drought and other shortcomings of the traditional CI. The CInew index is more sensitive to NCC2CI and traditional CI in the monitoring of long duration drought, while there is more possibility to leak the short duration of drought. NCC2CI can better monitor short duration drought, and CInew is better in capturing the starting time of drought than CInew and NCC2CI index. For monitoring the large intensity feature drought, the NCC2CI index can better monitor the higher intensity drought but weakly monitor the extreme drought. NCC2CI index can inherit the distribution and spatial characteristics of the traditional CI index. NCC2CI shows that the influence period of a larger precipitation is 20-40 d, which is more consistent with the development process of drought; while the influence period of a larger precipitation, shown through CInew index, is 45-70 d. In addition, the CInew index has larger difference with the traditional CI index in the spatial distribution, so having a poor reliability 〖JP2〗on application. With a comprehensive comparative analysis, the NCC2CI index is more practical in the Dongting Lake watershed; the research results have a certain reference to other similar watershed on the assessment of drought. In addition，one thing to note is that the meteorological drought index evaluate drought is only based on the evaporation, rainfall and other meteorological information. However, the actual drought is often integrated decision by meteorological, soil moisture, water conservancy facilities and water applications. The comprehensive meteorological drought index can not distinguish the difference between the harm degrees which is caused by the same degree of less precipitation in the farming period and the slack period (i.e. winter). Therefore, the evaluation of drought only based on meteorological index may cause