Mesoscale boundaries observed by SPOL in sowmex/timrex

During Southwest Monsoon Experiment (SoWMEX)/Terrain-influenced Rainfall Experiment (TiMREX) (May and June 2008), the NCAR S-POL radar deployed at river mouth of Gao-Ping, south of Taiwan to collect data for monsoon rainfall systems. SPOL CMD filter was applied to remove noise signals (Hubbert et al. 2009). Following Wilson and Schreiber (1986), 146 mesoscale boundaries are identified using filtered PPI scans reflectivity data by manual during whole experiment period (15th May to 29th June, 2008). According to the occurrence time, location, propagation characteristic, and the information from surface stations, the mesoscale boundaries are classified into 6 different categories. They are: (1) Onshore boundaries: The line echo near and parallel to the shore line, forms during the morning, moves onshore. (2) Offshore boundaries: The line echo near and parallel to the shore line, forms during the night, moves offshore. (3) Storm outflow boundaries: Thin line echo that forms near a storm, often propagates away from the storm. (4) Weak echo line over hill: Thin line echo that forms just east and parallel to a north-south orientation of hills. Surface winds are southerly. (5) Weak echo line over sea: Line of low reflectivity echoes align over the sea. It's likely a line of cumulus clouds associated with low-level convergence which can be divided into two groups: (a) Remote: The radar weak echo lines moves into radar range. (b) Local: The radar weak echo lines forms within radar range. (6) Unknown weak echo line overland: The other weak echo lines which don't have the common features to group. Observational characteristics of these boundaries will be discussed and presented.