HR: 1340h
AN: A33A-0867    [Abstracts]
TI: Numerical model experiments studying fine-scale meso-scale phenomena over the UAE and their impact on cloud and precipitation development
AU: * Jensen, T
EM: jensen@ UCAR.EDU
AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 United States
AU: Bruintjes, R T
A33A-0867 AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 United States
AU: Breed, D
EM: breed@ucer.edu
AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 United States
AU: Yates, D
EM: yates@ucar.edu
AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 United States
AU: Al Mandoos, A
EM: AMandoos@almiyah.gov.ae
AF: Department of Water Resources Studies, P.O.Box 4815, Abu Dhabi, none United Arab Emirates
AU: Al Mangoosh, A
EM: amangoosh@almiyah.gov.ae
AF: Department of Water Resources Studies, P.O.Box 4815, Abu Dhabi, none United Arab Emirates
AB: Mesoscale features, too small to be resolved in global models, play an important role in the formation of clouds and precipitation. The NACR-Penn State MM5 numerical model with a Real-Time Four Dimensional Data Assimilation System was used to simulate several events for typical summer conditions. Summer conditions were typically hot and dry, sometimes resulting in convective showers over and west of the Oman Mountains. With surface temperatures approaching 50o C, some aspects of the model were challenged, and changes were incorporated to benefit future users of the model. As expected, the sea breeze was a dominant factor in determining the conditions along the coast, with occasional convergence leading to convection. These features were not evident in global models due to their coarse resolutions. These detailed meso-scale flows also play an important role in the transport of pollutants and development of cloud and precipitation in the region. Some specific issues arose during the model assessment period. In the MM5 model, the land use categories are associated with specific settings for physical parameters characteristic of those general land use types. These have a strong impact on the diurnal variability of the near surface layers, including the amplitude of the diurnal oscillation in temperature. Sensible and latent heat fluxes can vary widely and be extreme in this environment. For example, unrealistically high moisture availability was known to dampen the daily temperature range. By decreasing the specific moisture availability from 5% for the desert regions (characterized as "sparsely vegetated") to 2% - a value we believe is more characteristic of this region - the diurnal temperature variability became more accurate. The paper will focus on highlighting some of the detailed meso-scale features in the region and provide some insights into these local features. Results from the simulations will also be compared with observations.
DE: 0325 Evolution of the atmosphere (1610, 8125)
DE: 1610 Atmosphere (0315, 0325)
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
DE: 3329 Mesoscale meteorology
DE: 3355 Regional modeling
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005