Arctic Aerosols Revisited Using the New Version 4 CALIPSO Level 2 Data: Contributions from Siberian Fires and Asian Dust Storms

CALIPSO has been providing vertical profiles of aerosols and clouds globally since June 2006 from space borne lidar measurements. The quality of the data products has continuously improved and the latest version of the level 1 data, released in April 2014, offers significant improvements in calibration of both 532 nm and 1064 nm backscatter measurements. Based on this level 1 input, a new version 4 level 2 data product is now scheduled for release in fall 2016. Among the important algorithm updates included in this new release are changes in the probability density functions that drive the Cloud-Aerosol Discrimination (CAD) technique as well as substantial updates to the downstream aerosol subtyping routines. We show how these changes are reflected in the version 4 aerosol distributions over the Arctic. Misclassifications of aerosols as clouds in version 3 in this region have been largely resolved. As a result, many more smoke layers originating e.g. from Siberian fires as well as dust and polluted dust layers transported from Asian dust source regions that were misclassified as cirrus in version 3 are now being correctly classified. The seasonal variation of these layers (smoke/dust/polluted dust) is consistent with the timings of major fire and dust events. We will present the distribution of the aerosol subtypes over the Arctic and aerosol CAD scores, a confidence metric quantifying the degree of separation between aerosol and cloud properties. The new subtyping scheme allows for all types of aerosol in the Arctic and thus a significant fraction of layers classified as clean continental in version 3 are now getting classified as other aerosol types. This results in changes in the ascribed lidar ratios and retrieved extinction profiles and aerosol optical depths. The increased number of smoke and dust/polluted dust layers over the Arctic resulting from these improvements will have implications for our understanding of Arctic climate and climate change. We will complement these results by providing a preliminary estimate of the changes in the aerosol mass flux from Siberian fires and Asian dust sources.