Questions to be addressed in Urban Meteorology

1
Questions to be addressed in Urban Meteorology

• Stephen Belcher, Janet Barlow
• Dept of Meteorology
• University of Reading

2
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.

3
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.

4
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.

5
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.

6
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.