Comparison Between Lidar and Nephelometer Measurements of Aerosol Hygroscopicity at the Southern Great Plains Atmospheric Radiation Measurement Site

[1] Aerosol hygroscopicity has a significant effect on radiative properties of aerosols. Here a lidar method, applicable to cloud-capped, well-mixed atmospheric boundary layers, is employed to determine the hygroscopic growth factor f(RH) under unperturbed, ambient atmospheric conditions. The data used for the analysis were collected under a wide range of atmospheric aerosol levels during both routine measurement periods and during the intensive operations period (IOP) in May 2003 at the Southern Great Plains (SGP) Climate Research Facility in Oklahoma, USA, as part of the Atmospheric Radiation Measurement (ARM) program. There is a good correlation (∼0.7) between a lidar-derived growth factor (measured over the range 85% RH to 96% RH) with a nephelometer-derived growth factor measured over the RH range 40% to 85%. For these RH ranges, the slope of the lidar-derived growth curve is much steeper than that of the nephelometer-derived growth curve, reflecting the rapid increase in particle size with increasing RH. The results are corroborated by aerosol model calculations of lidar backscatter and nephelometer equivalent f(RH) based on in situ aerosol size and composition measurements during the IOP. It is suggested that the lidar method can provide useful measurements of the dependence of aerosol optical properties on relative humidity and under conditions closer to saturation than can currently be achieved with humidified nephelometers.

[1]  David D. Turner,et al.  Automated Retrievals of Water Vapor and Aerosol Profiles from an Operational Raman Lidar , 2002 .

[2]  John A. Dutton,et al.  Dynamics of atmospheric motion , 1995 .

[3]  J. Ogren,et al.  Four years of continuous surface aerosol measurements from the Department of Energy's Atmospheric Radiation Measurement Program Southern Great Plains Cloud and Radiation Testbed site , 2001 .

[4]  Bruce Morley,et al.  Aerosol hygroscopic properties as measured by lidar and comparison with in situ measurements , 2003 .

[5]  R. Ferrare,et al.  Raman lidar measurements of aerosol extinction and backscattering 2. Derivation of aerosol real refractive index, single-scattering albedo, and humidification factor using Raman lidar , 1998 .

[6]  David D. Turner,et al.  Continuous Water Vapor Profiles from Operational Ground-Based Active and Passive Remote Sensors , 2000 .

[7]  David J. Delene,et al.  Variability of Aerosol Optical Properties at Four North American Surface Monitoring Sites , 2002 .

[8]  P. Minnett,et al.  Observations of large aerosol infrared forcing at the surface , 2003 .

[9]  Peter V. Hobbs,et al.  Humidification factors for atmospheric aerosols off the mid‐Atlantic coast of the United States , 1999 .

[10]  F. Kasten.  Visibility forecast in the phase of pre-condensation , 1969 .

[11]  S. Kreidenweis,et al.  Predicting Particle Critical Supersaturation from Hygroscopic Growth Measurements in the Humidified TDMA. Part II: Laboratory and Ambient Studies , 2000 .

[12]  Amy P. Sullivan,et al.  Refinements to the particle-into-liquid sampler (PILS) for ground and airborne measurements of water soluble aerosol composition , 2003 .

[13]  M. Stolzenburg,et al.  On the sensitivity of particle size to relative humidity for Los Angeles aerosols , 1989 .

[14]  S. Twomey.  Pollution and the Planetary Albedo , 1974 .

[15]  S. Pandis,et al.  Cloud activation of single‐component organic aerosol particles , 2002 .

[16]  P. Saxena,et al.  Water-soluble organics in atmospheric particles: A critical review of the literature and application of thermodynamics to identify candidate compounds , 1996 .

[17]  W. Malm,et al.  Humidity‐dependent optical properties of fine particles during the Big Bend Regional Aerosol and Visibility Observational Study , 2003 .

[18]  Peter V. Hobbs,et al.  Humidification factors of aerosols from biomass burning in Brazil , 1998 .

[19]  D. Covert,et al.  Size distributions and chemical properties of aerosol at Ny Ålesund, Svalbard , 1993 .

[20]  J. Goldsmith,et al.  Turn-key Raman lidar for profiling atmospheric water vapor, clouds, and aerosols. , 1997, Applied optics.

[21]  Tim Elliott,et al.  Four Years of Continuous Surface Aerosol Measurements from the Department of Energy's Atmospheric Radiation Measurement Program Southern Great Plains Cloud and Radiation Testbed Site , 2022 .

[22]  Robert J. Charlson,et al.  A Study of the Relationship of Chemical Composition and Humidity to Light Scattering by Aerosols , 1972 .

[23]  Volker Wulfmeyer,et al.  On the relationship between relative humidity and particle backscattering coefficient in the marine boundary layer determined with differential absorption lidar , 2000 .

[24]  S. Schwartz,et al.  Apportionment of light scattering and hygroscopic growth to aerosol composition , 1998 .

[25]  Olivier Boucher,et al.  General circulation model assessment of the sensitivity of direct climate forcing by anthropogenic sulfate aerosols to aerosol size and chemistry , 1995 .

[26]  J. Coakley,et al.  Climate Forcing by Anthropogenic Aerosols , 1992, Science.