The Energy Budget of the Mesosphere Derived from SABER

Abstract:

The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument measures the vertical distribution of infrared radiation emitted by various atmospheric gases (ozone, water vapor, nitric oxide, and carbon dioxide), providing important information about the radiation budget in the upper atmosphere. From the SABER radiances, we determine the radiative cooling by CO2, solar heating by O3 and O2, and chemical heating from a suite of exothermic reactions over the vertical range of 65-100 km. In addition, we derive amounts of several constituents of those chemical reactions and are able to determine bounds on a key parameter in the energy calculation, atomic oxygen. In general we find the global annual mean heating and cooling to be in balance within the measurement uncertainties. This is because the atomic oxygen concentrations derived from SABER are at the maximum, radiatively allowed limit. The results will be discussed in terms of the absolute energy balance and its variation with the solar cycle. In general the changes in radiative cooling appear consistent with changes in solar and chemical heating over the solar cycle. SABER, launched in December 2001, will soon have collected 13 years of this unique, comprehensive dataset on middle atmosphere structure and energy balance.