Uses of Precipitation-Based Climate Indices in Drought Characterization

摘要

The standardized precipitation index (SPI) is widely used in meteorological drought classification on a monthly or seasonal scale. A new monthly drought classification scheme using daily precipitation-based climate indices—consecutive two dry days (CDD2), maximum one-day rainfall (RX1), and maximum five-day rainfall (RX5)-is attempted in this study. A rule was created to derive the drought class from climate indices using northwest Indiana regional rainfall. The U.S. Drought Monitor, which uses the SPI for drought classification, was compared with the proposed new drought classification scheme. The SPIs derived using monthly data do not have a bearing on extreme precipitation indices because of lumping. This study hypothesizes that the climate indices can improve drought classification on a monthly/ seasonal scale. The results are validated using the northwest Upper Mississippi and northeastern Indiana regions. The new classification and the SPI are very similar in most of the months, when the indices and monthly rainfall deviate similarly from normal values. The proposed reclassification incorporates stress to the watershed system when a major portion of the monthly rainfall is due to one or two events. It also captures deviations in the climate indices from normal values and uses them in the classification.