Collaborative Research: Doppler on Wheels International H2O Project Participation and Studies of Convective Initiation

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The International H20 Project (IHOP) is a multi-investigator, multi-agency program whose chief aim is improved characterization of the four-dimensional distribution of water vapor and its application to improving the understanding and prediction of convection. Program emphasis is on four important research areas: quantitative precipitation forecasting; convective initiation, atmospheric boundary layer processes; and instrumentation testing. Critical to the success of the IHOP is the measurement of wind and thermodynamic values spanning several scales of motion. This will be accomplished with unique and varied instrumentation. To contribute to achieving the goals of IHOP, the Principal Investigators have submitted collaborative proposals. As part of the required IHOP instrumentation suite, the Principal Investigators will deploy the University of Oklahoma Doppler on Wheels (DOW) radars. These radars provide the IHOP researchers with a high resolution instrument for obtaining detailed wind measurements. These measurements have applications to all four IHOP research components. The DOWs will coordinate with both fixed-site and mobile observing platforms to sample with unprecedented data density and resolution the pre-convective environment, including wind and thermodynamic properties within and along boundaries and convergence lines.For their research contribution to the IHOP, the Principal Investigators will analyze these data to elucidate the magnitude of gradients in the water vapor field and the role of the wind field in focusing these inhomogeneities. For example, the Principal Investigators will determine if locally convergent mesoscale circulations along boundaries or intersections between convergence zones, possibly associated with horizontal convective rolls (HCRs), create pockets of high water vapor content. They will further assess the orientation of water vapor gradients with respect to the HCRs. In addition to boundary studies, the Principal Investigators will perform analyses of data collected on days without obvious convergence zones to determine the degree of variability in the water vapor field in the absence of substantial focusing mechanisms. After understanding the nature and degree of water vapor variability in the pre-convective environment further analysis will focus on the relationship of these inhomogeneities to the convective initiation process based on current hypotheses. For example, if pockets of high water vapor content are found to exist, the Principal Investigators will then examine whether deep convection indeed is favored at these locations. They will examine in detail the depth of lifting associated with observed very small scale circulations and convergence zones to determine the transport of water vapor in the boundary layer. The goal is a better understanding of the mechanisms governing water vapor variability in the preconvective environment and the dynamical processes by which this variability is manifested in the convective initiation process.