by Robert Banks

PBL height 052714Robert Banks (ESR13) was hosted for a month-long secondment from the 17th of May to the 15th of June in the Laser Remote Sensing Unit (LRSU) at the National Technical University of Athens (NTUA) in Greece. The LRSU is a part of the Physics Department at NTUA. Opportunistically, this secondment coincided with the HygrA-CD (from Hygroscopic Aerosols to Cloud Droplets) campaign. The main contribution from the secondment was to make use of the established know-how of numerical weather prediction from the Barcelona Supercomputing Center and link it with remote sensing instruments (lidars, ceilometer, and microwave radiometer) to study the planetary boundary layer (PBL) over Athens.

During the secondment an assessment of the sensitivity of atmospheric variables in the PBL to different model PBL parameterization schemes was initiated. Hourly numerical simulations of atmospheric variables including PBL height, 2 m air temperature, and wind speed and direction from the WRF-ARW (Weather Research and Forecasting – Advanced Research WRF) mesoscale meteorological model were evaluated against observations from a multiwavelength Raman lidar and radiosoundings from the nearby meteorological institute. PBL heights were determined from the Raman lidar using a Kalman filter approach and from radiosoundings using the bulk Richardson number method. Both lidar-estimated and radiosonde-estimated PBL heights showed good agreement.

Athens secondment 2Future work based upon this secondment will include the assessment of other PBL parameterization schemes, as WRF-ARW v3.5 offers the choice between ten different PBL parameterization schemes, each with a unique method of parameterizing the PBL structure and turbulent kinetic energy. The goal of this project is to improve the accuracy of PBL heights in WRF which are used as inputs into air quality forecast systems.

Very special thanks to the ITaRS team at NTUA, including valuable advice and suggestions from Prof. Dr. Alexandros Papayannis (Head of LSRU) and the gracious hospitality and research collaborations with Athina Argyrouli (ESR12) during this secondment.