Raman Lidar Profiling of Aerosols and Water Vapor Over the Southern Great Plains
Ferrare, R.A.(a), Turner, D.D.(b), Clayton, M.B.(c), Brasseur, L.H.(c), Tooman, T.P.(d), Goldsmith, J.E.M.(d), Ogren, J.(e), and Andrews, E.(f), NASA Langley (a), Pacific Northwest National Laboratory (b), SAIC (c), Sandia National Laboratories (d), NOAA (e), CIRES/NOAA (f)
Twelfth Atmospheric Radiation Measurement (ARM) Science Team Meeting
The automated Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) Raman Lidar (CARL) has routinely been measuring profiles of water vapor mixing ratio, relative humidity, aerosol extinction, aerosol backscattering, and aerosol and cloud depolarization during both daytime and nighttime operations. Aerosol and water vapor profiles acquired since March 1998 are used to investigate the seasonal and diurnal variabilities of the vertical distributions of water vapor and aerosols. The vertical distribution of aerosol extinction varies with both season and with aerosol optical thickness. The scale height for aerosol extinction increases from below 1 km during the winter to above 2 km during the summer. These profiles show the presence of elevated aerosol layers as the aerosol optical thickness increases. In contrast to the aerosol extinction profiles, the vertical distribution of water vapor mixing ratio is relatively constant and scales with the total precipitable water vapor. The average lidar aerosol extinction profiles show considerably greater diurnal variability than the total aerosol optical thickness. Near the surface, this diurnal variability of aerosol extinction is correlated with the diurnal variability of relative humidity. Profiles of the aerosol extinction/backscattering ratio, Sa, are also derived from the CARL data. Large (>15%) variations in the vertical profile of Sa occurred about 30% of the time, which implies that significant variability in the vertical distribution of the aerosol size distribution and/or composition often occurs. In order to help understand this aerosol vertical variability, we have also begun examining profiles of aerosol scattering and absorption and relative humidity measured by the In-situ Aerosol Profiling (IAP) sensors on a light aircraft flown periodically (2-3 times/week) above the SGP site. While initial comparisons of water vapor mixing ratio and relative humidity measured by CARL and the IAP aircraft instrument generally show agreement to within about 5%, initial comparisons show that the IAP retrievals of aerosol extinction are about 30% lower than the CARL measurements of aerosol extinction. We will discuss how CARL and IAP measurements are being used to examine the vertical variability of aerosol optical parameters.
Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).
