HR: 1340h
AN: A43D-0125    [Abstracts]
TI: Measuring the Interannual Variability of Arctic Cloud Properties and Influences on Surface Temperatures and Radiation Budgets
AU: * Uttal, T
EM: Taneil.Uttal@noaa.gov
AF: National Oceanic and Atmospheric Administration, R/E/ET6 325 Broadway, Boulder, CO 80305 United States
AU: Frisch, S
EM: Shelby.Frisch@noaa.gov
AF: Cooperative Institute for Research of the Atmosphere, 325 Broadway, Boulder, CO 80305 United States
AU: Shupe, M
EM: Matthew.Shupe@noaa.gov
AF: Cooperative Institute for Research in the Environmental Sciences, 325 Broadway, Boulder, CO 80305 United States
AB: In Barrow, Alaska a sophisticated suite of surface radiometers and cloud radars and lidars has collected an eight year history of detailed cloud properties including geometrical, optical and microphysical properties. This time record is now long enough (several consecutive annual cycles) to begin to determine patterns in interannual variability of not only cloudiness and cloud properties, but also direct and indirect cloud impacts on other environmental parameters. Three studies are summarized. The first compares monthly averages of cloud fraction and cloud optical depth computed with the surface sensors to 5 different satellite data sets. The satellite sets are determined with different sensors (e.g. MODIS, AVHRR and TOVS) and utilize different radiometric channels and retrieval methodologies. It is concluded that while all methods seem to agree reasonably well on detection of cloud fraction, there is substantial disagreement on detection of cloud optical depth. The second study examines the effect of Arctic clouds on the accurate determination of surface temperatures with satellites. In this study, in-situ and satellite determined surface temperatures are compared for periods of fractional cloudiness ranging from 0% to 100%. Not unexpectedly, cloud fractions larger than 50% are shown create significant biases in the satellite derived surface temperature, and that the biases can be positive or negative depending on the time of year. In the third study, cloud forcing is determined from broad-band radiometers and clear-sky radiation models. It is determined that while there is significant interannual variability in cloud forcing, that the net cloud forcing is generally positive (warming the surface) for most of the year, except for a short period in the summer when solar elevation angles are relatively high. The cloud forcing information is further partitioned with cloud phase/optical depth information which indicate that the cloud liquid water path is a much more significant determinant of cloud forcing that cloud fraction. This result is significance on the first study in this presentation which indicates that satellites are not particularly good at determining cloud optical depth/liquid water path.
UR: http://www.etl.noaa.gov/arctic
DE: 0321 Cloud/radiation interaction
DE: 1610 Atmosphere (0315, 0325)
DE: 1637 Regional climate change
DE: 3310 Clouds and cloud feedbacks
DE: 9315 Arctic region (0718, 4207)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005