Observations of the 9 June 2002 Dryline During IHOP

ABSTRACT

Detailed studies of drylines that do not initiate storms are rare but scientifically important. Studying these null cases will improve the understanding of critical factors separating whether convection would be initiated along a dryline. This observational study presents a null case dryline near the Oklahoma/New Mexico border during the International H2O Project (IHOP_2002) on 9 June 2002. High-resolution observations obtained from an airborne Doppler radar (ELDORA), two water-vapor Differential Absorption Lidar (LEANDRE II and LASE), Learjet dropsondes, as well as aircraft in situ measurements were used to describe the dryline environment and mesoscale structures in both along- and cross-line directions. The 9 June dryline was characterized by a rather broad radar reflectivity thinline with a large moisture gradient. Its updrafts were found generally associated with the local maximum of radar reflectivity; however, they were not colocated. The simultaneous observations from ELDORA and LEANDRE II confirmed that the dryline updrafts tend to be located near its moisture gradient, consistent with previous findings using aircraft in situ measurements.

The dryline moisture boundary was found to be greatly modified by mesocyclone circulations, which caused the alongline moisture gradient at certain segments of the dryline to become greater than the cross-line moisture gradient. Twodimensional water vapor fields derived from LEANDRE II across the dryline clearly showed the moisture gradient associated with the dryline and moisture variations on the order of ~ 1 g kg-1 on both sides of the dryline. No storms initiated within the IHOP_2002 domain associated with this dryline owing to unfavorable atmospheric instability conditions and only weak upward forcing near the dryline.

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