考虑下垫面类型的干旱指数比较研究

干旱作为常见的自然灾害,在世界各地发生的频率日渐增加,已对经济发展、农业生产和人类生活等方面产生了严重影响。但是干旱的类型较多,包括气象干旱、土壤干旱、水文干旱、农田干旱等,无法用单个干旱指数对不同类型的干旱进行监测。按照干旱发生类型,利用气象干旱指数(Standardized Precipitation Index SPI)、土壤水分干旱指数(Soil Moisture Index, SMI)和蒸发压力干旱指数(Evaporative Stress Index,ESI)对美国的旱情进行监测。研究结果表明:不同干旱指数之间呈显著相关,相关系数R在0.7以上。ESI整体监测精度较高,它能够真实反映地表水分盈亏状况,同时与遥感数据结合,可以实现从田块到全球不同尺度干旱实时监测。不同植被类型覆盖下垫面对不同类型干旱响应存在较大差异,草地下垫面对不同类型的干旱响应较为一致,但是随着地上生物量的增加,不同干旱指数监测结果之间差异逐渐增大。因此,在干旱监测时需要考虑植被的结构特征,植被与气候之间的相互作用,才能具体分析不同下垫面的受灾情况,进一步考虑更适合的方法以及干旱指数监测不同下垫面的干旱情况。

Evaluation of Drought Indices of Metrology,Hydrology and Agriculture over the Continental United States

Droughts are one of the more normally natural hazards on a year-to-year basis. And the drought are significant and widespread, affecting economic development, agriculture and people health at any one time. There are various drought indexes have been developed to monitor this hazard which arise precipitation decrease, soil moisture deficit and vegetation stress. However, single drought index cannot consider all of these anomaly to warn and monitor the drought. In this study, remote sensing based data including GLDAS climate data involve precipitation and soil moisture, GLEAM ET and GRACE dataset simulated terrestrial water storage are used to calculate multiple drought indicators including SPI, SMI, ESI and TWSC. These drought indicators refer to anomaly of precipitation, soil moisture and vegetation water supply, and terrestrial water storage change, respectively. Then they were used combined and compared to track the droughts events in United State of American. The results showed that all the drought indexes performed reliable and consistent with each other well, with correlation coefficient value greater than 0.7. However, the ESI performed more reliable, which can reflect the plant water stress under dry condition, additionally, it can be computed in combined with satellite observed data with high spatial resolution to monitor the drought conditions from field scale to global scale. The vegetation have divergent responses to the meteorological, hydrological and droughts except under grassland. The differences between the three drought indexes increase along with the elevated aboveground biomass. Therefore, the land surface vegetation covered conditions involve canopy structure and feedback between plants and climate, which relevant in a drought monitor is often a curial consideration in determining the application of drought indexes.