HR: 09:30h
AN: A41B-09    [Abstracts]
TI: Seasonal Prediction of the Regional Eta/SSiB model in North American Climate Stu
AU: * Xue, Y
EM: yxue@geog.ucla.edu
AF: Department of Geography, Department of Atmospheric Sceinces, UCLA, CA, 1255 Bunche Hall, Department of Georgaphy UCLA, Los Angeles, CA 90095-1524 United States
AU: Zavisa, R
EM: rvasic@geog.ucla.edu
AF: Department of Geography, Department of Atmospheric Sceinces, UCLA, CA, 1255 Bunche Hall, Department of Georgaphy UCLA, Los Angeles, CA 90095-1524 United States
AU: Janjic, Z
EM: "Zavisa Janjic"
AF: NCEP/NOAA, 5200 Auth Road NCEP/NOAA, w/c2 wwb room 204, Camp Springs, MD 20746 United States
AU: Mesinger, F
AF: NCEP/NOAA, 5200 Auth Road NCEP/NOAA, w/c2 wwb room 204, Camp Springs, MD 20746 United States
AB: This study aims to understand the predictability of the Regional Eta/SSiB model in the North American regional climate study. We mainly focus on model simulations of precipitation and other relevant hydro-meteorological variables. To achieve our goals, a series of sensitivity studies are designed to explore the role of a variety of factors in water cycle simulations. These factors include domain size, lateral boundary conditions, horizontal resolution, sea surface temperature, and convective parameterizations. The summer of 1998 is selected for the experiments. The results show that the domain size and lateral boundary conditions have the most significant impacts on the simulations. In the domain size experiment, a set of domains is selected for testing. The domain that covers only continental U.S. produces the best simulations in temporal evolution and spatial distribution of the precipitation. When the domain is expanded to the southern oceans, although the model is still able to produce reasonable large-scale circulation, the simulations of the intensity and the spatial distribution of the precipitation deteriorate dramatically when the ocean areas become large. It is likely that there is a southern barrier for the Eta model with reanalysis data and also there could be a critical spatial scale beyond which regional climate starts interacting strongly with the global climate. The lateral boundary conditions are also crucial for regional climate studies as the regional model tends to maintain the imposed large-scale features. Because the 200mb zonal wind and low level moisture transfer play crucial roles in proper simulations of the 1998 US summer precipitation, maintaining the same boundary conditions produce similar large scale patterns and cause limitations in the climate sensitivity study. For example, when investigating the deep soil temperature effect using the Eta model, it was found that with the same lateral boundary conditions in both control Eta run and anomaly Eta run, the impact of deep soil temperature is not clear. The climate anomaly signals become evident only when deep soil temperature anomalies are imposed to both regional Eta model and the GCM, which provides the lateral boundary conditions for the Eta model, in the anomaly runs.
DE: 3322 Land/atmosphere interactions
DE: 3337 Numerical modeling and data assimilation
DE: 1833 Hydroclimatology
DE: 1610 Atmosphere (0315, 0325)
DE: 1620 Climate dynamics (3309)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting