Abstract

Boundary layer convergence zones (BLCZs), atmospheric features that are capable of causing convergence near the surface, are well-known to be precursors of thunderstorm development. Recent field projects have provided useful data from surface stations as well as reflectivity, velocity, and a new ... Show moreBoundary layer convergence zones (BLCZs), atmospheric features that are capable of causing convergence near the surface, are well-known to be precursors of thunderstorm development. Recent field projects have provided useful data from surface stations as well as reflectivity, velocity, and a new radar-derived field for water vapor measurements, refractivity, all of which can be used to better characterize the three-dimensional structure of BLCZs. This research analyzed selected boundaries from the 2002 International H₂O Project (IHOP) and the 2006 Refractivity Experiment For H₂O Research And Collaborative operational Technology Transfer (REFRACTT). There were a total of 8 cases selected from IHOP and REFRACTT that were analyzed and compared on a variety of aspects: boundary type (4 outflows, 2 bores, 1 moving boundary of unknown origin, and 1 topography-induced boundary), differences within boundary type (outflow, bore), location (between Colorado (REFRACTT) and Oklahoma (IHOP), between surface stations in IHOP), and observation type (surface station vs. radar). For the eight cases examined, the boundary-layer depth varied from 1.0 to 2.4 km. The depth, propagation speed, and fine-line width of the four outflows were positively correlated. The two bores lasted up to several hours, longer than any other BLCZ types, and the boundary-layer depth of the bores varied inversely with the propagation speed. Refractivity data showed that the moisture gradient varied either ahead, behind, or with the reflectivity fine-line. However, more work is needed to verify these characteristics, which will help extend the knowledge on these and other types of BLCZs. Show less