Water vapor estimation using near-surface radar refractivity during IHOP_2002

A ground-based radar refractivity mapping technique is used to measure water vapor near the surface during the International H2O Project in May and June, 2002 (IHOP_2002). Radar-measured refractivity is compared with refractivity estimated from surface station observations during this field experiment. Bias in radar and station refractivity is found to occur often when humidity is high. Possible reasons for this difference between radar and station observations are discussed. Most of the biases were associated either with inaccurate humidity observations by stations or with the small height difference of the two measurements. With confirming this last observation further during these wet ground conditions, radar refractivity shows much better agreement with radiosonde sounding refractivity just above the surface than with station refractivity.;In addition, columnar water vapor is computed using the mixing ratios retrieved from radar and station refractivity and using the observed height of the convective boundary layer from a FM-CW radar. Surface moisture fluxes are computed as a residual of the columnar water vapor and compared with observations from flux-towers, which compute this using the eddy-covariance technique. Although the results show that the radar-based measurements may have some skill over longer time periods, the technique completely fails to reproduce observations over scales smaller than 1 hour.