Airborne water vapor DIAL and in situ observations of a sea-land interface

Two contrasting boundary layers in an enclosed valley are observed with a water vapor differential absorption lidar (DIAL) and in situ instruments on board the National Center for Atmospheric Research (NCAR) Electra and University of Wyoming King Air research aircraft, Lidar observations of water vapor and aerosols agree very well with in situ observations over agricultural land in the Imperial Valley of California and the Salton Sea. DIAL water vapor profiles averaged over 12 km in the horizontal and 200 m in the vertical are within 10 % of in situ measurements. Lidar observations reveal the very heterogeneous nature of the planetary boundary layer (PBL) over land, and show a pronounced difference in PBL structure between the land and sea. The structure superficially resembles a sea breeze, but in situ observations reveal an advected convective boundary layer mixing into a stably-stratified layer that overlies a much shallower PBL over the sea. The observations show the benefit of complementary remote profiling and in situ observations in airborne studies of the planetary boundary layer (PBL). The airborne DIAL system is proven capable of describing very fine boundary-layer structure in aerosol backscatter, and water vapor features on the scale of about 200 m in the vertical and a few kilometers in the horizontal.