Questions to be addressed in Urban Meteorology Stephen Belcher, Janet Barlow Dept of Meteorology University of Reading

How does the wind direction at street level vary with geostrophic? Might expect wind direction within streets to be rectified with a strong component along the street in either direction. But, how does this wind direction and strength vary with the direction of the wind above the buildings? Can address this question within the observational campaign because: (i) Relatively simple to measure from wind profiles within streets; and (ii) Can compare with analogous measurements taken in Salfex.

What is the magnitude of horizontal vs. vertical transport? Mixing and transport within urban areas is controlled by: (i) horizontal transport along the pathways governed by the street geometry; and (ii) the vertical transport out into the boundary-layer aloft. At Reading we have focussed previously on the case where the wind blows perpendicular to a long 2-D street. In this idealisation there is no horizontal transport only vertical mixing. We have studied this problem using wind tunnel measurements, observations made with Bristol at Hall Farm, and we have a simple model for the vertical mixing in this case.

Horizontal vs. vertical Cont. Now moving to the case when wind blows at an angle to a long 2-D street canyon. How big is the horizontal transport compared to the vertical mixing as a function of wind direction? This question will be tackled by: –Running simulations using our urban canopy model (a neighbourhood model) –Firstly in a 2-D geometry –Secondly in a 3-D geometry –Thirdly perhaps in LES –The observational campaign might also help.

High resolution Meso-scale modelling It is now possible to run the Met Office Unified Model at a resolution of 1Km. Hence the model now begins to resolve urban areas - the question is how do we do this? We need a method for representing urban areas in meso scale models. Work is under way at Reading to address this problem and we hope that the new approach will be implemented over the lifetime of DAPPLE. This offers the opportunity for some case studies to be run, perhaps over the periods covered by the observations.

UWERN urban meteorology prog. The UWERN Urban Met Web pages are currently being revamped. DAPPLE is a project within this initiative and will contribute to these pages when the time comes. The good news for the UWERN Urban Met initiative is that momentum is rising and the atmospheric chemistry community is coming on board so that we can have a serious bid at forecasting urban air quality.