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Verification and Case Studies for Urban Effects in HIRLAM Numerical Weather Forecasting

Verification and Case Studies for Urban Effects in HIRLAM Numerical Weather Forecasting. A. Baklanov , A. Mahura, C. Petersen, N.W. Nielsen, B. Amstrup Danish Meteorological Institute, DMI, Copenhagen, Denmark. 3-4 May 2007, COST-728 Workshop on “Model Urbanization Strategy”

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Verification and Case Studies for Urban Effects in HIRLAM Numerical Weather Forecasting

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  1. Verification and Case Studies for Urban Effectsin HIRLAM Numerical Weather Forecasting A. Baklanov, A. Mahura, C. Petersen, N.W. Nielsen, B. Amstrup Danish Meteorological Institute, DMI, Copenhagen, Denmark 3-4 May 2007, COST-728 Workshop on “Model Urbanization Strategy” UKMO, Exeter, United Kingdom

  2. Goal and Specific Objectives GOAL: • Evaluate effects of urbanization of numerical weather prediction (NWP) model on simulating meteorological fields for specific cases and overall model performance over the urbanized areas SPECIFIC OBJECTIVES: • Perform short- and long-term simulations of meteorological fields using DMI-HIRLAM-U01/I01 models in two modes: control vs. urbanized runs • Evaluate effects of urbanization on temporal-spatial structure and variability of meteorological fields • Estimate on a diurnal cycle the differences between control and urbanized runs for meteorological variables such as surface pressure, temperature, wind, and relative humidity

  3. HIRLAMDomains, Land-Use Classification, & Urban Features • Domain - DMI-HIRLAM-U01 (1.4 km) • Focus - Island of Zeeland (I01) • Land surface scheme - Interaction Soil-Biosphere-Atmosphere (ISBA) • Tiles - 5 (low vegetation, forest, ice, water, bare soil) + urban (fraction >0.1+)

  4. HIRLAM Numerical Weather Prediction Modelling • Model • DMI-HIgh Resolution Limited Area Model (HIRLAM) • Boundary conditions • DMI-HIRLAM-T15 -> -S05 -> U01/I01 • Runs • control vs urbanized (i.e. modif ISBA scheme) for U01/I01 domain • Modification/ Urbanization • SIMPLE: roughness and anthropogenic heat flux for urban grid cells • BEP: Building effect parameterization module • Output • 3D meteorological fields (40 levels) for 2 types of runs

  5. Module 1 (DMI etc): Analytical urban parameterisations (SIMPLE) • Displacement height, • Effective roughness and flux aggregation, • Effects of stratification on the roughness (Zilitinkevich et al, 2004), • Different roughness for momentum, heat, and moisture; • Calculation of anthropogenic and storage urban heat fluxes; • Prognostic MH parameterisations for SBL; • Parameterisations of wind profile in canopy layer (Coceal and Belcher, 2004; Zilitinkevich and Baklanov, 2004). 1st NWP layer

  6. HIRLAMApproaches + Evaluation of Modelling Results • Long-term simulations • Short-term simulations - specific meteorological situations • NWP Control vs. urbanized runs • Diurnal cycle • Difference fields for control vs. urbanized runs • Temperature at 2m, wind at 10m, rel humidity, surf. pressure • Focus: impact of urbanized areas on meteorological fields

  7. Typical Wind Conditions : SIMPLE URBAN ------------------ Difference (control vs. urbanized run) field for wind at 10 m ------------------ ------------------ Difference (control vs. urbanized run) field for temperature at 2 m ------------------ 06 UTC 18 UTC 12 UTC

  8. Low Wind Conditions : SIMPLE URBAN ------------------ Difference (control vs. urbanized run) field for wind at 10 m ------------------ ------------------ Difference (control vs. urbanized run) field for temperature at 2 m ------------------ 03 UTC 21 UTC 12 UTC

  9. Low Wind Conditions : BEP URBAN (a) Difference plots between outputs of DMI-HIRLAM vs. DMI-HIRLAM+BEP for (a) wind velocity at 10 m and (b) air temperature at 2 m for 20 UTC forecast on 12 April 2005 (b)

  10. HIRLAM NWP Model Performance: Overall all stations

  11. HIRLAM NWP Model Performance: Over Urban Areas Wind velocity at 10 m (w10s, in m/s; top panel) & Air temperature at 2 m (T2m, in deg. C; lower panel) based on the DMI-HIRLAM-U01 control (NOA) vs urbanized runs (A20, ZO2) vs. observational data (obs) Værløse urban station (55.8ºN, 12.3ºE) located in metropolitan Copenhagen

  12. Conclusions • Long-term runs with the DMI-HIRLAM-U01/I01 high resolution urbanized model showed a slight improvement for the overall NWP model performance, & this improvement is more considerable over the urbanized areas Differences between NWP control vs. urbanized runs: • For typical wind conditions: • wind at 10 m (m/s) <0.5 (max up to 1.5, at midday) • temperature at 2 m (ºC) <0.25 (max up to 0.5, at nighttime) • relative humidity (%) > 3 (max up to 5, at midday) • For low wind conditions: • wind at 10 m (m/s) >1 (max up to 3 at nighttime) • temperature at 2 m (ºC) >0.5 (max up to 1.5, at nighttime) • relative humidity > 4 (max up to 7, at midday)

  13. Plans • Long-term simulations by DMI-HIRLAM high resolution model urbanized version (on-going runs): • HIRLAM+BEP - building effect parameterization module, • HIRLAM+SM2_U - soil model for sub-meso scales urbanized version, • At first, at least, for 1-2 months; • Second, for a longer period (year) in order to evaluate month-to-month variability.

  14. Thank you • Computing • DMI facilities of NEC SX6 • Advice of DMI EDB Computer Support Department • Financial Support • DMI-ENVIRO-HIRLAM project activities

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