DOW radar and water vapor DIAL observations and comparisons with mesoscale models in COPS

The World Weather Research Program (WWRP) Research and Development Project (RDP) Convective and Orographically-induced Precipitation Study (COPS) occurred during the summer of 2007 in southwestern Germany and eastern France. COPS was aimed at advancing the quality of forecasts of orographically-induced convective precipitation with the use of 4-D observations and modeling of its life cycle. One of the components of improving quantitative precipitation forecasting skill is better understanding of convection initiation processes.

A unique combination of pre-convective measurements was obtained during COPS with two Doppler on Wheels (DOW) mobile radars and a high-powered water vapor Differential Absorption Lidar (DIAL). The combination of these wind velocity and water vapor measurements in the pre-convective environment may enable better understanding of low-level boundaries and coherent structures in orographic terrain and their associated influence on the distribution of the 3-D moisture field. This is expected to be important for convection initiation applications.

The DOW and DIAL observations will be compared with an ensemble of convection-permitting models, which were available by collaboration with the WWRP Forecast Demonstration Project (FDP) D-PHASE. The comparisons will be performed either with a model forward operator simulating the DOW performance around its site or by profiling of mixing ratio over the DIAL site. Preliminary results indicate that most models suffered from a strong positive moisture bias in the boundary layer, which may have negative implications on their capability to simulate convection initiation. Ongoing studies will address whether these comparisons can be used to investigate the parameterization of land-surface processes and the ABL in atmospheric models.