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IUKWC Workshop Nov16: Developing Hydro-climatic Services for Water Security – Session 4 – Item 2 A_Orr


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IUKWC Workshop November 2016: Developing Hydro-climatic Services for Water Security
Session 4.2 Andrew Orr

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IUKWC Workshop Nov16: Developing Hydro-climatic Services for Water Security – Session 4 – Item 2 A_Orr

  1. 1. Assessing WRF model experiments of precipitation in the Himalayas Andrew Orr British Antarctic Survey
  2. 2. HKK Himalaya Bookhagen & Burbank (2010)
  3. 3. Schematic drawing of a regional climate model
  4. 4. Objective: Determine the size distribution of various hydrometeors, i.e. rain particles, cloud droplets, snow crystals, graupel particles and ice particles Cloud microphysics processes and precipitation Cloud microphysics scheme Mixing ratio of hydrometeors Mean diameter or number concentration of hydrometeros Single moment Predicted Fixed Double moment Predicted Predicted Key difference between single and double moment microphysics schemes
  5. 5. Scheme Single moment Double moment WSM5 cloud, ice, rain, snow x WDM6 ice, snow, graupel cloud, rain Thompson cloud, snow, graupel rain, ice Morrison cloud rain, ice, snow, graupel Summary of the hydrometeor species represented by the WSM5, WDM6, Morrison, and Thompson cloud microphysics schemes.
  6. 6. Experiment methodology • Test Morrison, Thompson, WSM5, and WDM6 schemes as the cloud microphysics option in a regional atmosphere model • Each simulation is for a 10-day period from 1-10 July 2012. • Regional atmosphere model employed is the Weather Research and Forecasting (WRF) model • Model output compared to available observations, and used to determine key microphysical processes
  7. 7. Topography of the Langtang Valley, Nepal Site 1 (Kyangjin) Site 2 (Near Yala) Elevation (m asl) 3857 4831 Precipitation Tipping bucket Pluviometer Radiation Radiometer x
  8. 8. Number of domains 4 Horizontal grid spacing 30 km, 10 km, 3.3 km, 1.1 km Number of vertical levels 29 Model top 50 hPa Forcing data ERA-Interim reanalysis Boundary layer Mellor-Yamada-Nakanishi- Niino (MYNN) Cumulus (30 km and 10 km domains only) Betts-Miller-Janjic (BMJ) Shortwave radiation Dudhia scheme Longwave radiation Rapid Radiative Transfer Model (RRTM) Land surface Noah land surface model Microphysics Morrison, Thompson, WSM3, WDM6 Summary of the WRF model setup
  9. 9. Ten-day time-series of accumulated total precipitation measured at sites 1 and 2 (thick lines) for the period 1-10 July 2012. Dashed lines indicate simulated liquid precipitation only.
  10. 10. Histograms of frequency of 3-hourly precipitation (mm) measured at sites1 and 2 for the period 1-10 July 2012.
  11. 11. Ten-day time-series of 3-hourly incoming shortwave radiation (W m-2 ) measured at site 1 for the period 1-10 July 2012.
  12. 12. Ten-day time-series of the vertically-integrated column density (kg m-2 ) of hydrometeors at sites 1 (solid lines) and 2 (dashed lines) for the period 1-10 July 2012.
  13. 13. Accumulated total precipitation (mm) over the Langtang catchment for the period 1-10 July 2012. The precipitation for Thompson, WSM5, and WDM6 is expressed as the difference with respect to that from Morrison. The model topographic height is shown as contours (every 400
  14. 14. Ten-day average column-integrated horizontal moisture flux (vectors, kg m-1 s-1 ) and accumulated total precipitation (shading, mm) over the innermost domain for the period 1-10 July 2012. The model topographic height is shown as contours (every 2000 m).
  15. 15. (top) Air motion vectors (m s-1 ) and relative humidity (%) and (bottom) hydrometeor mixing ratio ratio (g kg-1 ) along a meridional vertical cross section passing through site 1 (filled circle) using the Morrison and Thompson schemes during the precipitation episode on 5 July 2012.
  16. 16. •Cold-rain processes are a key precipitation formation mechanism in Langtang Valley, Himalaya. •The choice of the microphysics scheme strongly affects precipitation over Langtang Valley (particularly over ridges). •As well as microphysical structure, both large-scale and localised orographic forcing are important. •Improved modelling of cold-rain processes are critical for a realistic representation of cloud microphysics and precipitation. Summary
  17. 17. • Efforts to improve model simulation of clouds urgently requires further measurements of the microphysical properties of clouds in the Himalayan region. • This requires field campaigns based on use of Aerial Autonomous Vehicles, precipitation radar, and remote sensing • UK-India collaboration Future work / collaboration