Comparison of convective boundary layer heights derived from radar profiler and scanning aerosol lidar data near Chico, California

Comparison of convective boundary layer heights derived from radar profiler and scanning aerosol lidar data near Chico, California

James A. Schafer, California State University, Chico, Chico, CA; and L. Bianco and S. D. Mayor

Observations of daytime convective boundary layer (CBL) height derived from a National Oceanic and Atmospheric Administration (NOAA) radar profiler and the National Center for Atmospheric Research (NCAR) Raman-shifted Eye-safe Aerosol Lidar (REAL) will be presented. The instruments are located near Chico, California, separated by 7.8 kilometers, and operated on eleven common days in May, June, and July of 2012. An algorithm developed by Bianco et al. (2008) was applied to the 915 MHz wind-profiling radar data to estimate hourly CBL heights. Results were also “eye-inspected” to remove possible outliers. The algorithm uses fuzzy logic to evaluate three different wind-profiling radar parameters to estimate CBL heights. It combines information from the hourly profile of signal-to-noise ratio of the backscattered power with those from the profile of hourly variance of vertical velocity and the hourly profile of the spectral width of vertical velocity. A wavelet algorithm developed by Davis et al. (2000) was applied to the columns of the 1.54 micron wavelength aerosol backscatter images from the scanning lidar. The wavelet algorithm uses a Haar wavelet basis to detect step-like changes in aerosol backscatter that usually correspond to the CBL top. The scanning aerosol lidar provides spatial images that often reveal the entrainment zone within each single scan taken every 17 seconds. The figure in this abstract shows our preliminary comparisons of radar and lidar derived CBL heights from six days. The general trend from the limited data shows slightly higher CBL height readings from the scanning aerosol lidar compared to the radar profiler. The differences may be the result of actual differences in the height of the CBL due to location of the instruments, performance of the measurement techniques, and/or design of algorithms. A larger data set is needed to determine if a statistically significant difference is present. We intend to collect more data as resources permit to investigate.

REFERENCES: Bianco, L., J. M. Wilczak, and A. B. White, 2008: Convective Boundary Layer Depth Estimation from Wind Profilers: Statistical comparison between an automated algorithm and expert estimations, J. Atmos. Ocean. Tech., 25, 1397-1413. Davis, K. J., N. Gamage, C. R. Hagelberg, C. Kiemle, D. H. Lenschow, P. P. Sullivan, 2000: An objective method for deriving atmospheric structure from airborne lidar observations, J. Atmos. Ocean. Tech., 17, 1455-1468.