Comparison of Recalibrated AERI Observations with LBLRTM Calculations

The comparison of recalibrated spectra from AERI-00 and LBLRTM calculations show much smaller differences in the 800-1200 cm-1 atmospheric window region under “clear conditions” compared with the preliminary calibrated data. Results indicate that the new AERI-00 data is in good agreement with similar comparisons using SPECTRE data. However, the recalibrated spectra have small changes in other spectral regions. Large observation-model differences still exist in the 550-630 cm-1 region, especially for dry cases, indicating a potential problem in arctic radiance and atmospheric cooling rate calculations. Background Preliminary calibrated spectra from the Atmospheric Emitted Radiance Interferometer prototype (AERI-00) showed differences with LBLRTM calculations in the 800-1250 cm-1 interval under “clear conditions” that were much larger than similar comparisons using SPECTRE data (Ellingson et al., 1994ab). Recently, University of Wisconsin personnel discovered some problems in the AERI-00 observations and corrections have been made to the data from April 1994 July 1995. The corrections primarily affect the window region with largest changes under clear conditions (Knuteson et al., 1995). Data Preparation Clear-sky conditions for intercomparison of observations with calculations were selected from April, May, August, September, and November 1994 using Micro-pulsed Lidar (MPL) data. A given radiosonde launch time is considered to be clear if the MPL data indicate no clouds within a 40 minutes window (20 minutes before and after the given time). We have obtained 131 clear cases during above five months.