A line-by-line radiation transfer model is used to simulate the brightness temperatures measured in the atmospheric ''window'' between 10 and 13 μm by the advanced very high resolution radiometer (AVHRR/2) on the NOAA 7 satellite. The atmospheric properties are described by a large set of marine radiosonde profiles over the NE Atlantic Ocean and characterize the month of July. The effects of anomalous atmospheric conditions on the brightness temperatures are simulated by independently adjusting the humidity and temperature profiles, and it is found that the consequences of humidity anomalies are greater if they occur at height (pressure of <850 mbar), whereas temperature anomalies have greater effect if they are in the lower troposphere. Sea surface temperature (SST) retrieval coefficients, optimized for these July conditions, are derived and tested against simulated brightness temperatures derived using a ''withheld'' set of profiles and found to be accurate. Mean errors of several tenths of a kelvin were found when other, nonoptimized coefficients, taken from the literature, were applied to the original July conditions. The mean errors in SST derived using the optimized coefficients can also be a few tenths of a kelvin in extremely anomalous atmospheric conditions. These errors are large enough to be of concern to climate researchers but probably too small to permit direct verification by comparison with currently available conventional SST measurements.