Infrared Measurements of Atmospheric Composition over Antarctica

University Of Denver, Denver CO

Investigators

Abstract

The proposed project is to develop a program of observations of atmospheric chemistry using passive infrared instruments at McMurdo and the South Pole. The measurements will be made year round for two years, and will provide significantly more and better data and constraints for photochemical transport models. Since these models are used to predict future ozone depletion and climate change, it is important that they be as accurate as possible. The Antarctic ozone hole has shown the sensitivity of the southern polar stratosphere to chlorine, and it is expected that the gradual healing of the hole to mark the success of the policy. However, model predictions indicate the possibility of a delay in recovery due to the impact of global warming on the catalytic ozone destruction process. Since most current satellite instruments do not sample the polar regions in the winter, ground based instruments can make important contributions and data from the proposed instruments would also provide validation for new satellite sensors. These instruments are the four Fourier Transform Spectrometers (FTS) operated at Arrival Heights (in collaboration with the New Zealand National Institute for Water and Air Research) and at South Pole. Two of these FTS (0.1-1.0 cm resolution atmospheric emission) will be placed at South Pole and at McMurdo for year round operation, and a 0.003 cm-1 resolution solar FTS will be deployed at South Pole to be operated during the summer. The emission instruments will provide important information during the polar night regarding HNO3 and denitrification, as well as dehydration. The transmission FTS's will provide high resolution spectra from which we will derive vertical profiles as well as vertical column amounts of many molecules important in the ozone destruction process as well as atmospheric tracers such as HF. The spectra from the emission instruments will provide year round column abundance measurements of HNO3, CH4, O3, H2O, N2O, the CFC's, ClONO2, and NO2 prior to its conversion to other odd nitrogen. The solar instruments will additionally provide some altitude profile information about those molecules, as well as HCl, ClONO2, NO, NO2, HNO3, HF, and others. The obtained spectral data set will be used to determine the current state of NOx partitioning, to measure the extent of the denitrification, to measure water vapor profiles into the stratosphere, to measure dehydration, to determine the current CFC 11, 12, and 22 levels as well as stratospheric Cl in the form of HCl and ClONO2, and to perform comparisons between the two Antarctic sites in an effort to gain more insight into vortex related chemical and dynamical effects. In addition, the collected data will provide photochemical transport modelers the ability to compare model outputs to actual measurements, especially at intermediate stages. It is important at this time when we are approaching the beginning of the recovery from Cl-catalyzed ozone destruction, that we have a data set that comprehensively covers the major constituents of both the catalytic ozone destruction sequence and global warming, so as to be able to place in perspective the relative influence of the two mechanisms.