HU Professors' Instrumentation Indicate Ozone Layer Is Recovering

Hampton, VA -Co-Directors for Hampton University's Center for Atmospheric Sciences Dr. James Russell III and Dr. M. Patrick McCormick are principal investigators for two satellite instruments that were key in concluding that the earth's protective ozone layer stopped declining beginning in 1997. Data collected from the Stratospheric Aerosol and Gas Experiment II (SAGE II) and Halogen Occultation Experiment (HALOE) were instrumental in the findings.

According to the paper "Attribution of Recovery in Lower-Stratospheric Ozone" that will be released in September in the Journal of Geophysical Research-Atmospheres, the ozone between 18-25 km has stopped depleting due to the decline of atmospheric chlorine and bromine, which were limited by the 1987 Montreal Protocol and its amendments. Ozone at altitudes below 18 km are also improving but surprisingly at a faster rate than expected and chlorine and bromine may not be the reason. Data are still being analyzed to conclude why, but leading theories point to dynamics or chemistry changes possibly caused by global warming.

A team led by Eun-Su Yang of the Georgia Institute of Technology, Atlanta, analyzed 25 years of independent ozone observations at different altitudes in Earth's stratosphere, which lies between six and 31 miles above the surface. The observations were gathered from balloons, ground-based instruments, NASA and NOAA satellites.

McCormick is the principal investigator of SAGE II. SAGE II collected vertical profile data on ozone, aerosol extinction, nitrogen dioxide, and water vapor in the lower and middle stratosphere. Russell is principal investigator for HALOE which collected data on middle atmosphere composition and temperature, measuring vertical profiles of ozone, hydrogen chloride, hydrogen fluoride, and other gases and aerosols involved in the ozone chemistry.

"We could not say in 1997 that ozone decreases were slowing down because we needed a longer time series to show it's turnaround and that is what we have now," states Russell.

Without the data collected by these two sensors, this conclusion could not have been made. "HALOE and SAGE provide altitude-resolved ozone data and they have been extensively validated by the science community. The data are accepted as the gold standard measurements for ozone," states McCormick.

The complete research findings are published in the "Attribution of Recovery in Lower-Stratospheric Ozone" article authored by scientists at Georgia Institute of Technology, Jet Propulsion Laboratory/California Institute of Technology, NASA/Langley Research Center, NOAA Earth System Research Laboratory, Global Monitoring Division, the University of Alabama in Huntsville, and Hampton University.

SAGE II, launched in October 1984 aboard the Earth Radiation Budget Satellite and HALOE, launched in 1991 aboard the Upper Atmosphere Research Satellite, were turned off last year.

The NASA/Langley Research Center developed both the SAGE II and HALOE instruments under McCormick's and Russell's direction while they were both at LaRC. They joined Hampton University in 1996.