HR: 15:10h
AN: A33F-07 [Abstracts]
TI: Atmospheric Solar Absorption measurements in the lowest 3-km of the atmosphere with small UAVs
AU: * Ramana, M V
EM: ramana@fiji.ucsd.edu
AF: Center For Atmospheric Sciences, Scripps Institution of Oceanography, University of
California at San Diego, 9500 Gilman Drive, MC 0221, La Jolla, CA 92093, United States
AU: Ramanathan, V
EM: vram@fiji.ucsd.edu
AF: Center For Atmospheric Sciences, Scripps Institution of Oceanography, University of
California at San Diego, 9500 Gilman Drive, MC 0221, La Jolla, CA 92093, United States
AU: Roberts, G
EM: greg@fiji.ucsd.edu
AF: Center For Atmospheric Sciences, Scripps Institution of Oceanography, University of
California at San Diego, 9500 Gilman Drive, MC 0221, La Jolla, CA 92093, United States
AU: Corrigan, C
EM: ccorrigan@ucsd.edu
AF: Center For Atmospheric Sciences, Scripps Institution of Oceanography, University of
California at San Diego, 9500 Gilman Drive, MC 0221, La Jolla, CA 92093, United States
AU: Nguyen, H V
EM: hung@fiji.ucsd.edu
AF: Center For Atmospheric Sciences, Scripps Institution of Oceanography, University of
California at San Diego, 9500 Gilman Drive, MC 0221, La Jolla, CA 92093, United States
AU: McFarquhar, G
EM: mcfarq@atmos.uiuc.edu
AF: Department of Atmospheric Sciences, University of Illinois, 105S. Gregory Street, Urbana,
IL 61801, United States
AB:
This paper reports unique measurements of atmospheric solar absorption and heating rates in the visible (0.4-
0.7 ƒÝm) and broadband (0.3-2.8 ƒÝm) spectral regions using vertically stacked multiple light weight
autonomous unmanned aerial vehicles (UAVs) during the Maldives autonomous UAV campaign (MAC). The UAVs
and ground based remote sensing instruments determined most of the parameters required for calculating the
albedo and vertical distribution of solar fluxes. Measured fluxes have been compared with those derived from a
Monte-Carlo radiative transfer algorithm which can incorporate both gaseous and aerosol components. The
analysis focuses on a cloud-free day when the air was polluted due to long range transport from India, and the
mean aerosol optical depth (AOD) was 0.31 and mean single scattering albedo was 0.92. The UAV measured
absorption AOD was 0.019 which agreed within 20% of the value of 0.024 reported by a ground based instrument.
The observed and simulated solar absorption agreed within 5% above 1.0 km and aerosol absorption accounted
for 30% to 50% of the absorption depending upon the altitude and solar zenith angle. Thus there was no need to
invoke anomalous or excess absorption or unknown physics in clear skies, provided we account for aerosol
black carbon. The diurnal mean absorption values for altitudes between 0.5 and 3.0 km msl were observed to be
41¡Ó3 Wm-2 (1.5 K/day) in the broadband region and 8¡Ó2 Wm-2 (0.3 K/day) in the visible region.
Future investigations into the atmospheric absorption in cloudy skies will characterize the spatial and temporal
variation of the cloudy atmosphere in sufficient detail to simulate the vertical distribution of net solar fluxes to
permit comparison with the collected radiative observations. This next phase will utilize 4 stacked UAVs to
observe the extended cloud decks off the coast of California. A combination of observations and models will then
be used to assess if the amount of solar absorption observed to occur in cloudy atmosphere can be accounted
for without invoking unknown or anomalous physics.
DE: 0321 Cloud/radiation interaction
DE: 0360 Radiation: transmission and scattering
DE: 1610 Atmosphere (0315, 0325)
DE: 1704 Atmospheric sciences
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting