ORACLES Campaign, September 2016: Inversion of HSRL-2 Observations with Regularization Algorithm into Particle Microphysical Parameters and Comparison to Airborne In-Situ Data

We present microphysical properties of pollution layers observed with NASA Langley Research Center’s airborne high-spectral-Resolution lidar (HSRL-2). The data obtained by HSRL-2 consist of vertical profiles of three backscatter coefficients (β) taken at 355, 532 and 1064 nm and two extinction coefficients (α) measured at 355 and 532 nm. In our study we (1) inverted the 3β + 2α data into particle size distributions with a regularization algorithm, and subsequently computed (2) number concentration and (3) single-scattering albedo for four measurement profiles. We carried out a first comparison to the same particle characteristics measured with airborne in-situ instruments. The in-situ instruments were flown aboard the P-3B aircraft, which followed the flight track of the aircraft ER-2 that carried HSRL-2. We found good agreement of the co-located (space and time) data products, with a degree of reliability reaching 90%. A more detailed study on a larger dataset needs to be carried out in future work to (a) obtain important correction factors, (b) study the influence of different light-scattering models on the inversion results, and (c) identify sources of retrieval and measurement uncertainties.