High horizontal resolution PBL water vapor from the synergistic combination of VSWIR and IR measurements

A recent study has shown that fine horizontal resolution (tens of meters) retrievals of column water vapor and surface properties are possible from instruments measuring reflected solar spectra in the visible and shortwave infrared (VSWIR). Meanwhile, thermal infrared (TIR) instruments can reliably retrieve water vapor profiles above the planetary boundary layer (PBL), but its footprint sizes are of order of a few kilometers. We will show how to combine VSWIR and TIR retrievals to get new information about PBL water vapor, relying on the assumption that water vapors spatial variance is largely dominated by the variance in the PBL. Our presentation examines the validity of this assumption and demonstrates the ability to retrieve both the mean and horizontal variance of bulk-PBL water vapor within a TIR footprint. We combine airborne data with simulated retrievals applied to large eddy simulated PBLs, and provide evidence that deeper integration of the TIR and VSWIR retrievals could further reduce errors.