Analysis of Sudden Mesoscale Drying at the Surface

Abstract

Mesoscale surface data and special satellite-derived soundings from the Visible Infrared Spin Scan Radiometer (VISSR) Atmospheric Sounder (VAS) are used to investigate a case of sudden mesoscale drying at the surface on 17 June 1986, a day during the Cooperative Huntsville Meteorological Experiment (COHMEX). Dewpoints fall as much as ?6.3°C in less than 1 h over a small portion of central Tennessee. The drying occurs prior to the onset of convective activity. The satellite retrievals detect a narrow tongue of midtropospheric dry air that overlays moist air near the surface. The analyses indicate that heating-induced surface-based mixing penetrates the midlevels, bringing drier air to the surface and resulting in the sudden decreases in surface dewpoints.