11A.2 A MULTI-DOPPLER ANALYSIS OF CONVECTIVE INITIATION ON 10 JUNE 2002 DURING IHOP_2002

Forecasts of the initiation of deep moist convection are important in a variety of meteorological applications: flash flood, severe storm, and quantitative precipitation forecasting. Determining where and when convection occurs affects the aircraft and agriculture industries as well as the general public. Recently, the research community has placed a strong emphasis on factors that determine the likelihood of convection initiation. Field experiments have increased understanding of the processes leading to initiation. For example, Atkins et al. (1995) and Weckwerth (2000) observed horizontal convective rolls (HCRs) along a sea-breeze in Florida and found that their kinematic and thermodynamic properties played a significant roll in convection initiation. Similarly, Fankhauser et al. (1995) found that merging of thunderstorm gust fronts with HCRs lead to initiation. Other favored locations include discontinuities or kinks along a front (Kingsmill, 1995). Often, small variations in surface moisture and temperature have a profound effect on whether thunderstorms form (Mueller et al. 1993). Numerical simulations have also advanced understanding of convection initiation. For example, Crook (1996) used numerical simulations to conclude that variations in boundary layer temperature and moisture as small as 1 C and 1 gm kg-1 respectively can distinguish between no convection and intense convection. Lee et al. (1991) demonstrated how small variations in vertical shear, moisture, and convergence along a boundary can greatly affect the likelihood and timing of initiation, and the storm intensity when initiation occurs. Each of these studies suggests that observations of small scale variations in the thermodynamic and kinematic fields are necessary for understanding the processes that initiate convection. To this end, the International H2O Project (IHOP) gathered many ground-based and airborne research platforms in order to observe the effects of small-scale water vapor inhomogeneities in initiating convection. While airborne platforms surveyed a large region, ground-based assets were focused mainly within an intensive observation region (IOR) defined by the locations of the mobile Doppler radars. The IOR of each deployment was confined to approximately a 20 km by 20 km quadrilateral, obtaining high resolution observations to determine the role of water vapor in initiating convection. In accord with the goals of IHOP, this particular study attempts to characterize the properties of the wind and water vapor fields on 10 June 2002, and examine the interaction of these fields and their influence on storm initiation. Multi-Doppler wind syntheses are here examined to determine the kinematic structure of the boundary layer, and ultimately will be linked with airborne lidar measurements and surface in-situ data to examine the water vapor field. On 10 June 2002, the Doppler on Wheels (DOW) mobile radars, the XPOL radar, and the Shared Mobile Atmospheric Research and Teaching radar (SMART-R) along with the rest of the IHOP armada continuously observed a quasi-stationary cold front for three hours. The boundary layer structure transitions from horizontal convective rolls (HCRs) behind the cold front to open cell convection ahead of the front. As observed by Atkins et al. (1998) and Wilson et al. (1992), misocyclones are located along the cold front prior to initiation. The multiDoppler analyses provide the kinematic structure and evolution of these circulations. The corresponding water vapor field will be examined to determine the relationship of these circulations to the moisture variability along the front. Additionally, the evolution of the cold frontal depth and moisture convergence will be studied to determine why a lull in cloud growth occurred in the hour before convection initiated on the edge of the IOR and why convection did not initiate along the intensely observed portion of the front.