HR: 1340h
AN: A23A-0916    [Abstracts]
TI: Surface and Space-based Estimates of the Surface Radiation Budget for the Northeastern Pacific
AU: * Guo, G
EM: gguo@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, 104 COAS Admin Bldg Oregon State University, Corvallis, OR 97331-5503 United States
AU: Coakley, J A
EM: coakley@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, 104 COAS Admin Bldg Oregon State University, Corvallis, OR 97331-5503 United States
AB: Clouds and the Earth's Radiant Energy System (CERES) uses a suite of instruments on the Terra and Aqua satellites combined with analyzed weather data and information on surface conditions to estimate surface radiative fluxes. These estimates are compared here with measurements of the surface radiation budget collected with the RV Wecoma's radiometers for summertime cruises in the Northeastern Pacific. To assess the shipboard measurements, the radiometer observations were analyzed to identify cloud-free conditions. Cloud-free conditions are characterized by long periods (~ 2 - 4 hours) of relatively stable measurements in the normalized shortwave radiative flux. The normalized flux is the downward shortwave flux at the surface divided by the cosine of the solar zenith angle and is thus a measure of the broadband shortwave transmittance of the cloud-free atmosphere. Under cloud-free conditions, variability of the normalized shortwave flux is less than 1% for 15-minute periods of 1-minute observations. The longwave flux is likewise steady, but the longwave flux is less sensitive to the presence of broken clouds than the normalized shortwave flux. Observations for cloud-free conditions are compared with those calculated using broadband radiative transfer models. Profiles of temperature and humidity for these calculations are obtained from analyzed meteorological fields associated with the radiative flux measurements. In addition, for the shortwave flux, the optical depth of a marine aerosol is adjusted to achieve agreement with the measured fluxes. For summertime conditions in the Northeastern Pacific, a 0.55-μm aerosol optical depth of 0.1 reduces the noontime normalized shortwave flux by 15 Wm^-2, or by approximately 1.5%. Aerosol optical depths inferred from the comparisons typically fall within the range of 0.1-0.3, and once the optical depth is set, modeled and observed values of the normalized shortwave flux agree to within 2%. Comparisons will be presented of observed and calculated surface fluxes and estimates of these fluxes from collocated CERES data.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0360 Radiation: transmission and scattering
DE: 3359 Radiative processes
DE: 3360 Remote sensing
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005