Observations of the Afternoon Transition of the Convective Boundary Layer

Abstract

This manuscript uses 915-MHz wind profiler reflectivity and Doppler spectral width data in time versus altitude to characterize general behaviors of the ending of the daytime convective boundary layer. From a wide variety of observed patterns, two categories are identified: inversion layer separation (ILS) and descent. Several possible causes for the different shapes of the patterns are discussed. Results show the descent cases occur on relatively warm and moist days with weak turbulence and a weak capping inversion and ILS days occur on cooler and drier days with stronger turbulence and a stronger temperature capping inversion. The time at which the transition begins is also investigated and is found to be variable, sometimes beginning several hours before sunset.