Raman Lidar Observations of Aerosol Humidification Near Clouds

Ferrare, R. A., NASA - Langley Research Center

Aerosol Properties

Aerosol

Ferrare, R., et al., Evaluation of Daytime Measurements of Aerosols and Water Vapor Made by an Operational Raman Lidar over the Southern Great Plains, J. Geophys. Res., 111, D05S08, doi:10.1029/2005JD005836, 2006.


Relative humidity profiles derived from the Raman lidar during the ALIVE 2005 field experiment.


Aerosol extinction profiles derived from the Raman lidar during the ALIVE 2005 field experiment.


Aerosol humidification factor f(RH) from Raman lidar measured profiles of aerosol extinction and relative humidity.


Relative humidity profiles derived from the Raman lidar during the ALIVE 2005 field experiment.

Aerosol extinction profiles derived from the Raman lidar during the ALIVE 2005 field experiment.

Aerosol humidification factor f(RH) from Raman lidar measured profiles of aerosol extinction and relative humidity.

Upgrades to the Raman lidar at the ARM Climate Research Facility (ACRF) Southern Great Plains (SGP) were performed in 2004 and permit a much more detailed view of the variability of aerosols and water vapor near clouds at or near the top of the Planetary Boundary layer (PBL). Such studies were difficult, if not impossible, before the upgrades.

The aerosol and water vapor profiles from the upgraded Raman lidar were validated using data acquired during the September 2005 Aerosol Lidar Validation Experiment (ALIVE). Preliminary studies during ALIVE have demonstrated that Raman lidar measurements can be used to quantify how aerosol scattering and extinction vary with relative humidity. In addition, recent investigations using satellite, airborne, and surface remote sensing data have shown significant changes in aerosol properties within the "twilight zone" near clouds (i.e., the region near clouds of forming and evaporating cloud fragments and hydrated aerosols). High temporal resolution measurements of aerosol scattering and water vapor by Raman lidar can be used to directly investigate aerosol properties near clouds. The ground-based Raman lidar measurements, used in conjunction with airborne remote sensing and in situ measurements of aerosols and clouds acquired during the Cloud and Land Surface Interaction Campaign/Cumulus Humilis Aerosol Plume Study (June 2007), can be used to study in detail aerosol/cloud interactions.

The Raman lidar upgrades have resulted in a vastly improved capability to jointly assess aerosol extinction and its dependence on humidity near clouds. It can be used to evaluate the utility of using surface measurements of aerosol humidification and to assess model simulations of water uptake.