Diagnosis and Attribution of a Seasonal Precipitation Deficit in a U.S. Regional Climate Simulation

• Published in: Journal of hydrometeorology 2004-02, Vol.5 (1), p.230-242
• Main Authors: Gutowski, WJ Jr, Otieno, F O, Arritt, R W, Takle, E S, Pan, Z
• Format: Article
• Language: English
• ISSN: 1525-755X
• DOI: 10.1175/1525-7541(2004)005(0230:DAAOAS)2.0.CO;2

Precipitation from a 10-yr regional climate simulation is evaluated using three complementary analyses: self-organizing maps, bias scores, and arithmetic bias. Collectively, the three reveal a precipitation deficit in the south-central United States that emerges in September and lingers through February. Deficient precipitation for this region and time of year is also evident in other simulations, indicating a generic problem in climate simulation. Analysis of terrestrial and atmospheric water balances shows that the 10-yr average precipitation error for the region results primarily from a deficit in horizontal water vapor convergence. However, the 10-yr average for fall only suggests that the primary contributor is a deficit in evapotranspiration. Evaluation of simulated temperature and soil moisture suggests the model has insufficient terrestrial water for evaporation during fall. Results for winter are mixed; errors in both evapotranspiration and lateral moisture convergence may contribute substantially to the precipitation deficit. The model reproduces well both the time-average and time-filtered large-scale circulation, implying that the moisture convergence error arises from an error in simulating mesoscale circulation.