Latent heat flux profiles from collocated airborne water vapor and wind lidars during IHOP_2002

A water vapor budget analysis reveals that this flux divergence [(0.9 ± 0.4) g kg⁻¹ h⁻¹] plus the advection (0.3 g kg⁻¹ h⁻¹) are nearly balanced by substantial CBL drying [(1.5 ± 0.2) g kg⁻¹ h⁻¹] observed by airborne and surface in situ instruments, within the limits of the overall budget rms error of 0.5 g kg−1 h−1. Entrainment of dry air from aloft and net upward humidity transport caused the CBL drying and finally inhibited the initiation of deep convection.

All cospectra show significant contributions to the flux between 1- and 10-km wavelength, with peaks between 2 and 6 km, originating from large eddies. The main flux uncertainty is due to low sampling (55% rmse at mid-CBL), while instrument noise (15%) and systematic errors (7%) play a minor role. The combination of a water vapor and a wind lidar on an aircraft appears as an attractive new tool that allows measuring latent heat flux profiles from a single overflight of the investigated area.