Lidar-Retrieved Aerosol Humidification Factors at SGP Derived from CHARMS
Poster PDF
Authors
Kyle William Dawson — Universities Space Research Association
Richard A. Ferrare — NASA - Langley Research Center
Richard Moore — NASA Langley Research Center
Tyler Thorsen — NASA - Langley Research Center
Eduard Chemyakin — Science Systems and Applications, Inc.
Sharon P Burton — NASA - Langley Research Center
Marian B. Clayton — Science Systems and Applications, Inc. (SSAI)
Chris A. Hostetler — NASA Langley Research Center
Detlef Mueller — Science Systems and Applications, Inc.
Edwin W. Eloranta — University of Wisconsin
Robert E. Holz — University of Wisconsin/CIMMS
Category
ARM field campaigns – Results from recent ARM field campaigns
Description
Lidar measurements acquired during the Combined HSRL And Raman lidar Measurement Study (CHARMS) are used to investigate the vertical distribution of aerosols and explore observational capabilities at the SGP site in northern Oklahoma. Synergistic measurements with co-located Raman and HSRL lidar, combined with an AERI Interferometer allowed for a thorough investigation of aerosol properties as a function of simultaneous retrievals of relative humidity (RH). The ARM SGP Raman lidar measured profiles of aerosol backscatter and extinction and water vapor mixing ratio. The University of Wisconsin HSRL simultaneously measured profiles of aerosol backscatter, extinction and depolarization at 532 nm and aerosol backscatter at 1064 nm. Relative humidity profiles were derived using the Raman lidar water vapor mixing ratio profiles and AERI temperature profiles.
We show that the remote sensing measurements described above can be used to retrieve aerosol humidification factors, denoted by f(RH), which are then used to describe the hygroscopic properties of aerosol of a particular chemical composition and size, both of which can vary in the atmospheric mixed layer. To observe effects caused primarily by aerosol humidification rather than a change in the aerosol amount, we first isolate regions with nearly constant water vapor mixing ratio which are indicative of a well-mixed, daytime convective boundary layer (CBL). These analysis regions, which are identified using the Raman lidar water vapor mixing ratio profiles, are near the top of the CBL as determined by the HSRL aerosol backscatter measurements at 532 nm. We also examine how retrievals of f(RH) differ depending on the presence or absence of clouds and show that lidar and nephelometer retrieved f(RH) factors agree well using data acquired in regions away from the influence of clouds.
Surface measurements from the ARM Aerosol Chemical Speciation Monitor are combined with AERONET aerosol retrievals and the E-AIM model simulations to estimate f(RH) using the surface aerosol chemistry data and the retrieved column-effective aerosol size distributions. We show generally good agreement between lidar-retrieved and modeled f(RH) for times coincident with the AERONET aerosol retrievals emphasizing the importance of high-quality estimates of vertically-resolved size distribution parameters for retrievals of f(RH).
