11th Conference on Mesoscale Processes
32nd Conference on Radar Meteorology

J6J.3

The structure and evolution of the dryline and surrounding boundary layer on 22 May 2002 during IHOP

Michael S. Buban, CIMMS/Univ. of Oklahoma, Norman, OK OK; and C. Ziegler, E. N. Rasmussen, and Y. P. Richardson

During the afternoon and evening of 22 May 2002, dense multi-platform high-resolution data were collected over a small portion of the Oklahoma and Texas panhandles as part of the International H2O (IHOP) project. Using over-determined multiple Doppler radar syntheses in concert with an innovative Lagrangian analysis technique, the full 3-dimensional kinematic and thermodynamic structure of the dryline and surrounding boundary layer (BL) was obtained for a nearly 2 hour period. These analyses reveal the dryline as a strong (2-4 g kg-1 km-1) gradient of water vapor mixing ratio, which separated a shallow moist internal boundary layer to its east from a deep, dry CBL to its west.

The dryline was located within a persistent virtual potential temperature gradient, which solenoidally forced a thermally direct secondary circulation. The analyses show substantial along-line variability in the frontogenetical forcing that produces and extends the dryline gradient downstream. The secondary dryline-normal circulation was enhanced in regions of strong frontogenesis, increasing moisture lift within the updraft collocated with the dryline. The secondary circulation also enhanced top-down entrainment of dry air in the downdraft on the downstream (moist) side of the dryline. The boundary layer surrounding the dryline exhibited a complex, evolving organization consisting of varying combinations of open dry convective cells and horizontal convective rolls (HCRs). A field of updrafts and vortices were observed to move northward along and interact with the dryline to produce small-scale waves. The resulting deepening of moisture on the northern flank and drying on the southern flank of a vortex may be potentially important to convection initiation.

extended abstract  Extended Abstract (3.0M)

wrf recording  Recorded presentation

Joint Session 6J, IHOP
Thursday, 27 October 2005, 8:15 AM-10:00 AM, Alvarado ABCD

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