The modeling and analysis research activities at JPL consist of the development of computer programs that simulate:

        the hundreds of chemical reactions that affect atmospheric ozone

        the transport of ozone and other gases by atmospheric winds

        the thermodynamic changes that occur when air cools below the threshold for formation of polar stratospheric clouds.

    The results from these computer simulations are used to guide the interpretation of field observations in the context of the latest laboratory kinetic and spectroscopic parameters.  Typically, the computer codes are written in a programming language called FORTRAN and  run on Unix workstations.  A variety of graphically based programming languages are used to display maps of meteorological data and field. observations. 

Tools of the Trade: A Modeler and his Workstation

    The research activities in this area are individual efforts led by:

Mark Allen JPL/Caltech Multi-dimensional Model
Lucien Froidevaux Studies of Tropospheric Ozone
Michael Gunson Upper Tropospheric Trace Gases
Gloria Manney Polar Vortex Evolution
Ross Salawitch Photochemistry of Earth's Ozone Layer
Michelle Santee Polar Stratospheric Clouds and Denitrification

    Among the data sets used in these studies are satellite observations from MLS and other instruments aboard the Upper Atmospheric Research Satellite, shuttle-borne observations from ATMOS and balloon-borne observations from MkIV, and aircraft data from a number of ER-2, DC-8, and WB-57 aircraft missions.  Many of the modeling efforts in recent years have been focused on understanding the details of how polar stratospheric clouds and man-made chlorine affect ozone depletion.  It is well established that reactions on the  surface of polar stratospheric clouds (PSCs) initiate the depletion of ozone at high latitude during winter.  Our  activities have used model simulations to: 

        isolate the changes in ozone due to both chemistry and transport for individual years in the Arctic and Antarctic

        determine the phase (e.g., solid or liquid) and precise composition of PSCs based on the thermodynamic effects of these clouds on residual gas phase nitric acid and water vapor 

        understand the details of how nitric acid is permanently removed from the polar stratosphere by sedimentation of these clouds

        assess the quantitative consistency between observed chemical loss of ozone for individual winters and the "expected" loss based on observed concentrations of ClO.

    Other studies have played a key role in better quantifying how ozone is affected by sulfate aerosols under conditions of both quiescent background (e.g., non-volcanic) loadings and greatly enhanced (e.g., a factor of 30 above background) loadings that resulted following the volcanic eruption of Mt. Pinatubo in June, 1991. 

    Ultimately, all of these studies are directed towards gaining a more accurate predictive capability for future changes in stratospheric ozone.

    Several of the new investigations are focused on determining the global distribution of tropospheric ozone and gaining insight into how space-borne observations of trace gases can be used to quantify the effect of human activities on tropospheric ozone. 


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Author: Ross J. Salawitch
Page Design: Aaron B. Milam