Infrared radiative properties of the maritime Antarctic atmosphere

Abstract

The longwave radiation environment of the Antarctic Peninsula and Southern Ocean has been investigated using radiometric Fourier Transform Infrared (FTIR) measurements of atmospheric emission in conjunction with detailed radiative transfer theory. Temperatures in the lower troposphere between 259 K and 273 K diminish the radiative importance of water vapor and enhance the importance of clouds and CO2 relative to midlatitudes. Springtime variability in stratospheric temperature and ozone abundance has a small but noticeable impact of about 1.0 W m-2 on surface longwave flux under clear skies. The mid-IR window emissivities of low stratiform clouds are most often between 0.90 and 0.98, with few as large as unity. Most low stratiform clouds appear to have moderate mid-IR optical depth (5-10), but relatively large equivalent radius (9-11 μm). However, clouds with base height between 1 and 2 km have noticeably smaller emissivities and optical depths. -from Author