Mesoscale modeling and four-dimensional data assimilation in areas of highly complex terrain
- Battelle Pacific Northwest Lab., Richland, WA (United States)
A multiscale four-dimensional data assimilation (FDDA) technique, based on Newtonian relaxation, is incorporated into a mesoscale model and evaluated using meteorological and tracer data collected during a field experiment. The mesoscale model is used to predict synoptically driven flows and small-scale circulations influenced by terrain near the Rocky Flats Plant (RFP) for four nocturnal periods. Data assimilation is used to create dynamically consistent analysis fields based on mesoscale forecasts and asynoptic data. Observations from towers, minisodars, airsondes, tethersondes, rawinsondes, and profilers near RFP, as well as observations from surface stations throughout Colorado, are incorporated into the high-resolution analysis fields. Wind and turbulence quantities produced by the mesoscale model are used to determine the dispersion of tracer released from RFP for each evening. A subjective and statistical evaluation of meteorological and dispersion results is performed to examine FDDA effects on nocturnal circulations and tracer transport. The mesoscale model is able to qualitatively predict the mesobeta-scale drainage flows; however, the largest wind forecast errors occurred in a region immediately adjacent to the foothills. The FDDA technique reduced overall errors in the atmospheric and dispersion calculations, while the model generated realistic small-scale circulations not resolved by the data. Still, the model did not capture the shallow surface drainage flows east of RFP for two evenings during the field experiment. When the model was initialized with high-resolution analysis fields generated by FDDA and left to forecast, little improvement in forecasts were seen two hours after initialization time. This may be due to the fact that only observed horizontal wind components were assimilated into the analyses generated by FDDA; assimilation of temperature observations was not included. 32 refs., 12 figs., 4 tabs.
- OSTI ID:
- 274052
- Journal Information:
- Journal of Applied Meteorology, Vol. 34, Issue 12; Other Information: PBD: Dec 1995
- Country of Publication:
- United States
- Language:
- English
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