Publication Date:
2014-02-02
Description:
[1] This study performs three experiments to calibrate the drought area percentages in the Continental United States, six U.S. Drought Monitor (USDM) regions, and forty-eight states downloaded from the USDM archive website. The corresponding three experiments are named CONUS, Region and State, respectively. The datasets used in these experiments are from the North American Land Data Assimilation System Phase 2 (NLDAS-2). The main purpose is to develop an automated USDM-based approach to objectively generate and reconstruct USDM-style drought maps using NLDAS-2 data by mimicking 10-year (2000-2009) USDM statistics. The results show that State and Region have larger correlation coefficients and smaller root-mean-square-error (RMSE) and bias than CONUS when compared to the drought area percentages derived from the USDM, indicating that State and Region perform better than CONUS. In general, State marginally outperforms Region in terms of RMSE, bias, and correlation. Analysis of normalized optimal weight coefficients shows that soil moisture percentiles (top 1 m and total column) play the dominant role in most of the forty-eight states, evapotranspiration percentile plays an important role in eight states (WA, SD, LA, MS, OH, WV, NY, and MA), and total runoff plays an important role in the Southeast region and nine states, most of which are close to the coasts and the lakes (WY, MN, WI, MI, FL, SC, PA, RI, and DE), where streamflow is a large part of the annual water budget. This is a favorable result, as simulated soil moisture is more reliable when compared to total runoff and evapotranspiration, particularly in arid/semi-arid or forest and dense vegetation regions where there are poor simulations for total runoff or evapotranspiration, respectively. The optimal blended NLDAS drought index (OBNDI) has higher simulation skills (correlation coefficient and Nash-Sutcliffe efficiency) in the South, Southeast, High Plains, and Midwest regions when compared to those in the West and Northeast. The highest simulation skills appear in TX and OK. By using optimal equations, we can reconstruct the long-term drought area percentages and OBNDI over the continental United States over the entire period of the NLDAS-2 datasets (Jan 1979 to present).
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
Permalink