NUMERICAL FORECASTS OF THE DIURNAL TEMPERATURE CYCLE IN AN ARID URBAN ENVIRONMENT WITH MM5

摘要

Mesoscale model simulations are being performed at increasingly high resolutions in support of operational weather forecasting and air quality monitoring and assessment. Community models, such as the PSU/NCAR Mesoscale Model (MM5) contain reasonably complete parameterizations of sub-grid scale physical processes such as turbulent transfer of heat, moisture and momentum. However, at grid scales on the order of a kilometer, there may not be adequate fine scale detail in region-specific parameters such as land cover. This paper describes the evolution of surface temperature in the MM5 model in a case where there is negligible synoptic forcing, no occurrence of deep convection and where the response of the surface to radiative forcing determines the evolution of the surface temperature. The period of the analysis was 30 May, 2000 - 1 June, 2000. This period was chosen since it is representative of the "dry" summer, after the influence of winter mid-latitude cyclones and prior to the onset of the monsoon. At this time of year, the region is characterized by a diurnal cycle of generally light westerly winds driven by the heating of elevated terrain to the northeast of the city, and a light easterly return flow during the night.