Development and Evolution of the Convective Boundary Layer

The International H₂O Project (IHOP_2002) was designed to sample the three-dimensional time-varying moisture field to better understand convective processes. Numerous research and operational water vapor measuring systems and retrievals were operated in the U.S. Southern Great Plains from 13 May to 25 June 2002. This was done in combination with more traditional observations of wind and temperature. Boundary-layer evolution studies were designed to maximize observational overlap from multiple instruments to better understand the development of the moisture distribution during the evolution of the daytime convective boundary layer (CBL).

Three datasets on boundary-layer evolution were collected during IHOP (14 June, 21 June and 25 June 2002). The evolution of the moisture profiles from the Scanning Raman Lidar are used as the foundation for evaluating observations from other diverse datasets, including S-Pol radar with refractivity measurements; two Doppler on Wheels (DOW) mobile radars; P-3 aircraft with Leandre II water vapor Differential Absorption Lidar (DIAL); DLR water vapor DIAL onboard the German Falcon; University of Wyoming King Air in situ measurements and Wyoming Cloud Radar (WCR); a tethersonde; Integrated Sounding System (ISS) with a wind profiler, sodar and RASS; serial ascents from four nearby radiosondes; AERI interferometer; mobile radiometer and mobile and fixed mesonets. These three days comprise highly-coordinated data collection periods from before sunrise through the development of the CBL.

Preliminary results on 14 June 2002 suggest that the CBL grows up from the surface several hours after sunrise and penetrates into and dominates the wave motions from the previous evening's stable layer. Low-level bores and internal gravity waves may have an impact on the transition from the nocturnal boundary layer to the daytime CBL. The CBL continues its growth into the previous day's residual layer and becomes the dominant surface-based layer by 1815 UTC. The vertical distribution of moisture shows a dramatic mixing ratio decrease ~200 m below the top of the CBL, as defined from numerous independent datasets. Preliminary analyses suggest a great deal of spatial and temporal and daily variability in the moisture distribution on the three days. A comprehensive description of the development and evolution of the CBL will be presented.