EOL Seminar Series - Phillip Chilson, University of Oklahoma

Detection of Bragg scatter using S-band polarimetric weather radar: Theoretical and experimental considerationsPhillip B. ChilsonSchool of MeteorologyUniversity of OklahomaAlthough S-band (3 GHz, 10 cm) weather radars are conventionally used for the study and routine observation of precipitation, they can also detect backscatter from a host of other entities and phenomena: clouds; flying animals such as birds, bats and insects; and clear air turbulence.  Unlike Rayleigh and Mie scatter, which relies on the presence of discrete dielectric entities, echoes from the optically clear air is typically associated with gradients in the refractive index.  Wind profiling radars primarily rely on turbulence generated refractive index gradients (Bragg scatter) as the source of the backscattered signal they detect and process; however, Bragg scatter can also be detected by weather radar - especially those operating at S-band.  In this presentation I will discuss 1) the fundamental differences between Rayleigh and Bragg scatter; 2) why Bragg scatter is typically not detected by weather radar; 3) how the probability of detecting Bragg scatter in the atmosphere using weather radar can be enhanced, i.e., through polarimetry; and 4) why such measurements are important for meteorology and the atmospheric sciences.  After a brief overview of previous observations of Bragg scatter using other radar systems, I will present observations of Bragg scatter collected using NCAR S-Pol during a recent experiment conducted at the NOAA Boulder Atmospheric Observatory called LATTE (Lower Atmospheric Thermodynamics and Turbulence Experiment).  The ability to extend the measurement capacity of weather radar to observe Bragg scatter could have significant impacts, for example, on studies of boundary layer development, the formation of upper-level layers of enhanced turbulence and moisture, and elevated convection.Tuesday, 6 May 2014, 3:30PMRefreshments 3:15 PMNCAR-Foothills Laboratory 3450 Mitchell LaneBldg. 2 Large Auditorium (Rm 1022)

Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
May 1, 2014 to May 6, 2014