Factors Contributing to Non-Linear Variation in Clear Sky Outgoing Longwave Radiation with Sea Surface Temperature

Abstract:

This study investigates the ratio of clear sky longwave radiation leaving the top of the atmosphere to longwave radiation emitted by the ocean surface as a function of wavelength and atmospheric conditions. Non-linear variations occur around a critical sea surface temperature of approximately 300K. We find that the "water vapor window" wavelength range is the primary contributor to non-linear variations in broadband radiation. Using vertical profiles of temperature, water vapor, and other greenhouse gases from AIRS and forward radiative transfer, we identify what specific changes in atmospheric properties cause non-linear variations in the ratio of clear sky longwave radiation at the top of the atmosphere and the surface. These results will be helpful for understanding how the strength of the water vapor greenhouse effect will change at high temperature.