Comparisons Between Measured and Modeled Longwave Irradiances During Arctic Winter: Results from the Second International Pyrgeometer and Absolute Sky-Scanning Radiometer Comparison (IPARSC-II)
Marty, Ch.(a), Storvold, R.(a), Philipona, R.(b), Delamere, J.(c), Dutton, E.(d), Michalsky, J.(e), Stamnes, K.(f), Eide, H.(f), and Stoffel, T.(g), Geophysical Institute, University of Alaska Fairbanks (a), World Radiation Center, Davos, Switzerland (b), Atmospheric and Environmental Research, Boston (c), Climate Monitoring and Diagnostics Laboratory NOAA, Boulder (d), State University of New York at Albany (e), Stevens Institute of Technology, Hoboken, New Jersey (f), National Renewable Energy Laboratory, Golden (g)
Twelfth Atmospheric Radiation Measurement (ARM) Science Team Meeting
The longwave downward irradiance depends directly on the magnitude of the greenhouse effect. A recent comparison of longwave downward irradiances between global climate models and the best available surface measurements showed an especially large disagreement at observation sites with cold and dry climates. Accurate measurements and modeling of this irradiance is therefore required to detect and monitor possible changes in the greenhouse effect. The low water vapor content and the frigid meteorological conditions in the Arctic make measurements and modeling of the longwave downward irradiance a special challenge. The second International Pyrgeometer and Absolute Sky-scanning Radiometer Comparison (IPARSC-II), which was conducted at DOE’s Atmospheric Radiation Measurement (ARM) program site in Barrow, Alaska provided a unique opportunity to compare high accuracy longwave downward irradiance measurements and radiative transfer model computations during arctic winter. Participants from 12 international institutions deployed 15 pyrgeometers, which were field-calibrated against the Absolute Sky-scanning Radiometer (ASR). Continuous measurements over a 10 days period in early March 2001 with frequent clear-sky conditions yielded longwave downward irradiances between 120 and 160 Wm-2. The small average difference between pyrgeometer measurements, ASR irradiances and Modtran computations indicate that the absolute uncertainty of measured longwave downward irradiance under artic winter conditions is within ± 2 Wm-2 or about 1%.
Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).
