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 analyzes selected boundaries from the 2002 International H20 Project (IHOP) and the 2006 Refractivity Experiment For H20 Research And Collaborative operational Technology Transfer (REFRACTT). The 8 cases selected from IHOP and REFRACTT 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 and Oklahoma, 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 kilometers. 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 other BLCZ types, and the boundary-layer depth of the bores varied inversely with the propagation speed. Refractivity data showed that the gradient of moisture was on the west side of boundaries regardless of their direction of motion. More work is needed to verify these characteristics of BLCZs types and extend the knowledge to other types. Show less
