Comparisons of Raman lidar water vapor measurements and aircraft data

Description

The Raman lidar at the Southern Great Plains (SGP) site measures water vapor mixing ratio, as well as other constituents, at a maximum sampling rate of 10 s and 7.5 m vertical resolution. This is averaged to produce low-noise 10-s, 75-m resolution measurements, which are capable of resolving the major portion of turbulent motions in the convective boundary layer. While it is important to maintain the maximum temporal sampling rate possible, there is a trade-off in the selected vertical resolution on sampling error vs. random noise. This study investigates the optimal vertical resolution of the Raman lidar for calculating higher order moments of water vapor mixing ratios in the turbulent boundary layer. In addition, we compare the SGP Raman lidar water vapor measurements and the derived moments (i.e., variance and skewness) as a function of altitude to the Diode Laser Hygrometer (DLH) measurements collected during the Routine AAF Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) experiment. Of the numerous RACORO flights that occurred between January and June 2009, 16 were designed to capture turbulence information as a function of height through the boundary layer over the SGP site. Water vapor moments derived from the DLH data collected during these missions will be compared against the collocated Raman lidar measurements to evaluate the methodology used to derive the moments from the Raman lidar data.