TY - RPRT
AU - A. Betts
AU - J.H. Ball
AU - Michael Bosilovich
AU - P. Viterbo
AU - Yuanchong Zhang
AU - W.B. Rossow
AB - Using monthly means for 1990-1999, we assess the systematic biases in temperature and humidity, and the surface energy and water budgets of both ERA-40, and the climate of the NASA-DAO atmospheric finite-volume general circulation model (fvGCM) for five Mississippi sub-basins. We compare ERA-40 and the fvGCM with basin averages of surface observations of temperature, humidity and precipitation, the river basin estimates for the hydrological balance from Maurer et al. [2002], and the ISCCP retrieved skin temperature and surface radiation fluxes. We show the role of the soil water analysis in ERA-40, which generally supplies water in summer and removes it in winter and spring. The ERA-40 snow analysis increments are a significant contribution to the (smaller) frozen water budget. Compared with NCDC observations of screen temperature, ERA-40 generally has a relatively small (#1K) positive temperature bias in all seasons for the Mississippi basins, while the fvGCM has a large cold bias in temperature in winter. The ISCCP skin temperature estimate is generally high in winter and a little low in summer, compared to ERA-40 and the NCDC screen level temperature. For the western basins, summer precipitation is high in the fvGCM, while for the eastern basins it is high in ERA-40 (in 12-24 hour forecasts after spinup). Summer evaporation is higher in the fvGCM than in ERA-40; while winter evaporation has a high bias in ERA-40, leading to a corresponding high bias in specific humidity. Net shortwave radiation probably has a high bias in the fvGCM in summer. The seasonal cycle of incoming shortwave is much flatter in ERA-40 than the ISCCP data, suggesting that the reanalysis may have too much reflective cloud in summer, and too little in the cooler seasons. The temperature biases at the surface in both the fvGCM and the ISCCP data clearly have a negative impact on the surface long-wave radiation fluxes, although the bias in the net long-wave flux is rather less.
BT - ERA-40 Project Report Series
C1 - Research
CY - Shinfield Park, Reading
DA - 06/2003
LA - eng
M1 - 7
N2 - Using monthly means for 1990-1999, we assess the systematic biases in temperature and humidity, and the surface energy and water budgets of both ERA-40, and the climate of the NASA-DAO atmospheric finite-volume general circulation model (fvGCM) for five Mississippi sub-basins. We compare ERA-40 and the fvGCM with basin averages of surface observations of temperature, humidity and precipitation, the river basin estimates for the hydrological balance from Maurer et al. [2002], and the ISCCP retrieved skin temperature and surface radiation fluxes. We show the role of the soil water analysis in ERA-40, which generally supplies water in summer and removes it in winter and spring. The ERA-40 snow analysis increments are a significant contribution to the (smaller) frozen water budget. Compared with NCDC observations of screen temperature, ERA-40 generally has a relatively small (#1K) positive temperature bias in all seasons for the Mississippi basins, while the fvGCM has a large cold bias in temperature in winter. The ISCCP skin temperature estimate is generally high in winter and a little low in summer, compared to ERA-40 and the NCDC screen level temperature. For the western basins, summer precipitation is high in the fvGCM, while for the eastern basins it is high in ERA-40 (in 12-24 hour forecasts after spinup). Summer evaporation is higher in the fvGCM than in ERA-40; while winter evaporation has a high bias in ERA-40, leading to a corresponding high bias in specific humidity. Net shortwave radiation probably has a high bias in the fvGCM in summer. The seasonal cycle of incoming shortwave is much flatter in ERA-40 than the ISCCP data, suggesting that the reanalysis may have too much reflective cloud in summer, and too little in the cooler seasons. The temperature biases at the surface in both the fvGCM and the ISCCP data clearly have a negative impact on the surface long-wave radiation fluxes, although the bias in the net long-wave flux is rather less.
PB - ECMWF
PP - Shinfield Park, Reading
PY - 2003
T2 - ERA-40 Project Report Series
T3 - ERA Report
TI - Intercomparison of Water and Energy Budgets for Five Mississippi Sub-basins between ECMWF Reanalysis (ERA-40) and NASA-DAO fvGCM for 1990-1999
ER -