Comparing Estimated Cirrus Radiative Forcing from HSRL and Standard Backscatter Lidar Derived Optical Properties
Abstract
Cirrus are the most common cloud type in the atmosphere (Stubenrauch et al. 2013), and play a crucial role in modulating Earth's radiative energy balance. They are the only cloud type that can have a positive net daytime radiative forcing at the top of the atmosphere (TOA), however, depending on their microphysical properties can also have a net cooling affect (Campbell et al. 2016). Lidar instruments provide valuable vertical profiles of cirrus layer microphysical and optical properties, which are incorporated into radiative transfer (RT) simulations. The NASA Airborne Cloud Aerosol Transport System (ACATS) is a high spectral resolution lidar (HSRL), which has the ability to discriminate between the particulate and molecular components of a lidar return signal. This allows for the direct calculation of cirrus optical properties such as particulate extinction and particulate backscatter coefficients without assuming a lidar ratio, which is common with standard backscatter lidar optical property retrievals (Fernald et al. 1972 and Klett 1981, 1985). The ACATS lidar has been collecting zenith-pointing data of varying cirrus subtypes (winter and summertime synoptic) over Goddard Space Flight Center (GSFC) simultaneously with the standard backscatter NASA Cloud Physics Lidar (CPL). ACATS optical properties have less uncertainty compared to those calculated from the standard lidars due to the absence of the lidar ratio assumption. This results in more realistic RT simulations, which incorporate these optical properties as input parameters. The dataset will provide a robust comparison between HSRL and standard backscatter lidar cirrus optical retrievals, and further elucidate how these differences affect radiative forcing estimates. Preliminary RT simulations have been run using the Fu-Liou Gu RT model (Fu and Liou, 1992; Gu et al., 2003), and will be discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.A11B1879O
- Keywords:
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- 0319 Cloud optics;
- ATMOSPHERIC COMPOSITION AND STRUCTURE