Evaluation of rainfall evaporation retrieved by lidar means and its intercomparison with an analytical solution model during a virga episode.

Abstract:

The water cycle describes the fluxes and the continuous circulation of the water inside the earth hydrosphere through its three different phases (liquid, solid and gaseous). It refers to the continuous hydric mass exchanges between the atmosphere, earth, surface and underground waters. Other than water accumulation in different regions, i. e. the oceans, the terrestrial water fulfills multiple cycles including condensation, precipitation and evaporation. The contribution of the rain direct evaporation to the heat and moisture of the clouds and to the atmospheric moisture cycling is fundamental, but very few measurements of those processes are available. Rain evaporation directly influences the induction and mainteinance of the downdrafts under the cloud base both in mesoscale precipitation or convective environment. In the past, different approaches measured and retrieved rain evaporation both through remote sensing (radar) or in-situ measurements, but the different methods came with serious errors in the estimation. We first present with this study a retrieval of the rainfall evaporation using dual-wavelength high-resolution lidar. This already proven technique (Lolli et al., 2013) permits to retrieve the raindrop equivolumetric diameter and then the evaporation at each range bin up to full evaporation. The results are then utilized to assess the discrepancies with an approximate analytical solution model for raindrop evaporation.