The International Water Vapor Project: overview and UWyo participation

Bart Geerts, University of Wyoming

The International Water Vapor Project (IHOP), to be conducted in the central Great Plains in the late spring of 2002, will bring together an unprecedented array of mainly remote-sensing probes to measure or deduce water vapor distributions and their sources and sinks, in an attempt to improve our understanding of convective initiation, and to increase short-term precipitation forecasting skills. IHOP brings together interests in (a) convective initiation CI, (b) boundary-layer BL processes, and (c) cloud & precipitation processes. These three groups have as common objective to use state-of-the art technology to describe the water vapor field and its evolution at scales ranging from tens of meters to a few 100 km. The UW King Air is an essential platform, mainly for the CI and BL interests. Key hypotheses, instruments, and flight patterns will be presented.

The Wyoming Cloud Radar has been proposed to be operating on the UWKA, mainly in a vertical-plane dual Doppler (VPDD) mode. Previous work, mainly by Dave Leon, has demonstrated that the WCR, in VPDD mode, is able to describe the air motion in a vertical plane below the aircraft at a resolution of about 30 m and an accuracy of about 1 ms^-1. Of particular interest to the CI community is the detailed vertical structure, origin, and trigger potential of ‘radar fine-lines’. Operational forecasters are familiar with these lines and monitor them as the potential locus of CI. In flying stepped transects, the UWKA will document the kinematic and moisture structure of these shallow convergence lines.

This will be the first time that the WCR will be operating in VPDD mode aboard the UWKA. It is also the first time that the WCR will generally target optically clear air. Indirect evidence and WCR observations under less optimal conditions suggest that the echo concentration in the clear BL is sufficiently dense, certainly near convergence zones. These echoes are mostly or exclusively insects. The odds of a sufficiently strong signal, and of a quality synthesis of the airflow in transects will be discussed, as well as further plans for a comprehensive analysis and dynamical interpretation.