Aerosol Simulator

Abstract

We have developed a new aerosol lidar simulator to facilitate fair comparison of aerosols between global climate models (GCMs) and CALIPSO measurements. Mie scattering calculations are performed to compute the extinction and the 180-degree aerosol backscatter by species, which is then used to compute the lidar attenuated backscatter (ATB) and signal ratio (SR). The simulator also identifies the types of aerosols using an algorithm similar to that used to produce the standard CALIPSO level-2 aerosol data product, which is based on the surface type, the height of the aerosol layer, SR, and the depolarization ratio. We have also created a new GCM-oriented CALIPSO Aerosol Product (GOCAP) for model-observation comparison using the same algorithms for cloud screening, noise elimination, and aerosol typing as those used in the simulator. Using ACME v0.0, we demonstrate that the simulator accounts for the sampling and algorithmic differences between models and observations, making fair comparison possible. This new aerosol simulator and the corresponding new GOCAP dataset can be very useful for evaluating/constraining aerosol and aerosol-cloud-precipitation interactions in GCMs.