Investigation of Chemical and Dynamical Changes in the Stratosphere up to and during the EOS Observing Period

ABSTRACT

The primary scientific goal of this EOS Interdisciplinary Science (IDS) investigation is the isolation of anthropogenic ozone changes from natural changes. To achieve these goals, we have developed an array of linked activities including model (tool) development, observational data analysis, simulation of EOS instrument measurements, and production of specialized data sets. This IDS has generated 17 years of National Meteorological Center (NMC) balanced wind data, which are being transferred to the Goddard Distributed Active Archive Center (DAAC), and maintains the trajectory automailer used worldwide. In cooperation with the Data Assimilation Office (DAO), an additional goal of this IDS and the DAO is the production of assimilated chemical data sets. As part of that effort, this IDS is responsible for the development of chemical modules and quality control of the assimilation data product.

Currently, our research focus is on the UARS data as a precursor to the EOS data sets. Among our more significant recent research results are the simulation of the historical Antarctic ozone loss using new Lagrangian chemical modeling methods and UARS observations, a new understanding of the processes behind late-winter polar chemical recovery, new results from our interactive 2-D model on the asymmetry of mid-stratosphere polar ozone trends, new insights into the transport of tropospheric pollutants, and data analysis on the impact of the Pinatubo eruption on atmospheric chemistry. This IDS investigation has also been very active within the EOS program. For example, one of our members is the EOS CHEM Project Scientist. We also have sponsored student researchers and post-doctoral investigators.

This EOS IDS investigation's proposed goal is to use model and observational data in the EOS and pre-EOS time frames to separate anthropogenic from natural chemical processes within the stratosphere. The original proposal included the development of a stratospheric assimilation system for meteorological and chemical data. Tropospheric chemistry was added to our proposal in the subsequent negotiation phase. With the formation of the Data Assimilation Office (DAO) at the NASA Goddard Space Flight Center (GSFC), the assimilation efforts under our proposal and the Bates/Rood proposals were combined. The current role of our IDS is to provide expertise in stratospheric data, chemical modules for the assimilation system, support in the stratospheric assimilation chemistry package, and quality control of the assimilated product. Dr. Cohn, Co-Investigator (Co-I) on the EOS assimilation proposal, was added to this investigation to strengthen the link to the DAO. We continue to have a very strong interaction with the DAO, which is collocated with most members of our group at GSFC.

The current ongoing research activities and some of the scientific accomplishments of this IDS are summarized in the section below. These activities indicate current extensive utilization of aircraft (e.g., ER-2, DC-8) and satellite [e.g., UARS, TOMS] data. The tools and modeling approaches we are currently developing are directed toward utilizing the upcoming EOS data sets.

Within this IDS, EOS supports a post-doc at GSFC and a graduate student at Stony Brook. During the 1995 year, we also supported the visit of Mr. Gianluca Redaelli from the Universita' degli Studi l'Aquila as a graduate student.

This section describes some of the chemical and dynamical activities supported under this IDS. The testing and development of models as tools for our science objectives and analysis of EOS data is a critical activity in the pre-EOS time frame. Most of our activity centers around analysis of satellite and aircraft data sets .

2.2.1 Simulation of the onset of Arctic processing using the 3-D chemical model

The three-dimensional chemical model is being developed under research and analysis (R&A) funding with some augmentation by the IDS. The chemical package and transport scheme eventually will be used in the chemical assimilation effort. Thus, scientific testing of the 3-D chemical model is essential for the success of the IDS assimilation program and also allows us to move toward our goal of using the 3-D chemical model for interpreting long-term trends.

The 3-D transport model, using winds and temperatures from the Goddard Data Assimilation procedure, has been used with simple representations of photochemical processes. Recently, comparisons of an ozone simulation with observations from the Total Ozone Mapping Spectrometer (TOMS) and from the MLS show that the lower stratospheric transport is realistic for a year-long integration [Douglass et al., 1995a]. In an earlier study [Douglass et al., 1993], the early winter activation of chlorine was simulated using a simple parameterization for HCl loss at temperatures cold enough for polar stratospheric clouds (PSCs) to form. The HCl loss was due to the heterogeneous reactions of the chlorine reservoirs HCl and ClONO2. The difference between HCl calculated with and without this extra loss process was compared with early winter ClO observations by MLS. In no case are observed high values of ClO coincident with temperatures cold enough for PSC formation. The simulation also shows that air which has experienced cold temperatures is transported from higher latitudes to sunlit lower latitudes where high ClO is observed by MLS. The simulation shows the importance of transport to the appearance and disappearance of high values of ClO and the importance of mixing processes to the decrease in the magnitude of the ClO [Douglass et al., 1993].

The critical role of transport is also shown in the work of Schoeberl et al. [1993a]. Analysis of the UARS MLS observations in early January 1992 shows a clear relationship between predicted polar stratospheric cloud (PSC) formation along back trajectories and elevated ClO amounts. These findings are in good agreement with previous analysis of aircraft observations [Schoeberl et al., 1993b]. The observed decrease in ClO following a PSC encounter agrees with the decrease calculated using a photochemical model, provided the calculation accounts for the movement of the parcel. Schoeberl et al. [1993a] also showed that the occasional high values of ClO seen by MLS outside the polar vortex are accounted for by statistical fluctuations in the MLS data retrieval.

One advantage of the UARS data set is that many of the key stratospheric constituents are observed by at least one of the instruments. It is possible to combine observations from different instruments by accounting for dynamical variability. This technique was first used by Schoeberl et al. [1989] as potential vorticity (PV) mapping. PV mapping is one of the types of tools we can apply to EOS data sets. The mapping technique and its power in interpreting chemical observations is demonstrated by an analysis of CLAES observations of ClONO2 and HNO3; HALOE observations of ozone, HCl, NO, and NO2; and MLS observations of ozone and ClO [Douglass et al., 1995b].

Maps of ClO, ClONO2, HNO3, and ozone for the Northern and Southern Hemispheres show the major differences which lead to the formation of the ozone hole. In the Southern Hemisphere, deep within the polar vortex, the HNO3 is removed from the stratosphere. ClO levels are high, ClONO2 values are low, and ozone depletion is drastic. Nearer to the vortex edge, temperatures generally are still cold enough to produce nitric acid trihydrate (NAT) PSCs, but not cold enough for ice clouds. Both HNO3 values and ClONO2 values are large in this region, forming a "collar" surrounding the inner vortex. ClO, while elevated, is much lower than deep within the vortex.

In the Northern Hemisphere, low values of HNO3 are found only when NAT PSCs are actually present. High values of ClONO2 and moderate O3 loss are seen at the end of the winter. It was originally thought that the photochemistry of the Northern Hemisphere would resemble the photochemistry of the collar region.

The trajectory mapping technique developed under this IDS [Morris et al., 1995] is another powerful new procedure developed under this IDS which can be used to effectively collocate data measured at different times and places. Trajectory mapping has applications to data assimilation and will make an important contribution to validation of the EOS data sets. We have already applied the technique to UARS data sets.

The measurements of EOS AM's Measurements of Pollution in the Troposphere (MOPITT) instrument will produce low vertical resolution CO profiles and column CH4 measurements. The Ozone Dynamic Ultraviolet Spectrometer (ODUS), scheduled for the EOS CHEM payload, will produce column ozone. We have developed a new method using trajectories which allows us to reconstruct the vertical structure of trace gases from column measurements under certain conditions. The column can be thought of as a shadow or projection of the three-dimensional field. The time evolution of the projection along with the column information can be used to reconstruct the three-dimensional field. We combine the various projections (like a medical CAT scan) to estimate the three-dimensional structure. The technique is an improvement of the method originally developed by Schoeberl et al. [1992c].

Under this IDS, we have developed an interactive 2-D model based on the dynamics package of Bacmeister and Schoeberl [Bacmeister et al., 1995] to study long-term trends in trace gases. This model fully couples chemistry dynamics and radiation, and thus can be used to study the feedbacks between the processes which we have not been able to study with the fixed circulation 2-D model. Over the last year, the model's troposphere has been extensively tuned and the radiation routines upgraded. The chemistry package will be upgraded within the coming year to become compatible with the chemical packages used by the 2-D assessment model.

The stratospheric assimilation effort is focused on two activities, traditional meteorological assimilation, and constituent assimilation. Both of these are core activities of the Data Assimilation Office (DAO). The meteorological analyses (and forecasts) are used for both trajectory and chemical transport models, as well as flight planning in the aircraft missions. The constituent efforts are in their early stages, but have already contributed to advancement of Kalman filter data assimilation methods.

Accomplishments in the stratospheric assimilation effort include:

1. A three-and-one-half-year UARS assimilation
2. Operational support of the SPADE, ASHOE/MAESA, and STRAT campaigns
3. Use of the assimilation in successful multi-year 3-D transport chemistry applications
4. Assimilation of UARS temperature observations
5. New assimilation methodologies to improve stratospheric wind estimates
6. A theoretical study of the impact of the HIRDLS scanning
7. Kalman filter constituent assimilation
8. The use of assimilation winds in chemical assessments.

Constituent assimilation has a special role in the assimilation effort. It not only should provide a scientifically useful data product, but constituent assimilation provides an effective mechanism to build advanced assimilation capabilities. The role of constituent assimilation, plans, and interactions with NMC are described in the Data Assimilation Office Plan (available from R. Rood). Initial experiments with an idealized model have focused on the impact of the scanning capabilities of HIRDLS, compared with the single profile limb view of the UARS instruments. First results show that the scanning capability of HIRDLS does allow effective filling in of the tracer spectra (also see Section 2.5.2).

In early 1995, the world's first assimilation of UARS N2O on isentropic surfaces was completed. This is the first Kalman filter data assimilation of a global geophysical field. Because of the computational demands, the assimilation was run on the 512 node Intel/Paragon at JPL. The effort has been reported in Lyster et al. [1995].

The tropospheric chemistry effort is now utilizing the tools developed for stratospheric chemical and dynamical analysis including the trajectory models and the assimilated data. With the launch of EOS AM, MOPITT CO and CH4 data will be analyzed using the tools and techniques developed to analyze TRACE-A data discussed below. Two current activities in the tropospheric chemistry area are (1) use of models to evaluate the role of convection in stratospheric-tropospheric exchange and ozone formation; and (2) development of tropospheric ozone satellite products. Both of these efforts are also supported by the NASA R&A program.

In the area of convection, the multi-scale study of midwest convection (comparison of GEOS-1 and GCE-scaled up mass fluxes; GCE = Goddard Cumulus Ensemble model) was published [Pickering et al., 1995a] and a similar analysis completed for a tropical mesoscale convective event during TRACE-A [Wang et al., 1995]. Implementation and evaluation of the RAS (Relaxed Arakawa-Schubert) parameterization in the GEOS-1 transport scheme are in progress [Allen et al., 1995]. Variations in tropospheric Radon-222 data, signifying convective impact on transport at a number of tropical and mid-latitude sites, are well-simulated for a one-year simulation in 1991-92 and for shorter periods covered during intensive experiments (e. g. during 1987 STEP-Tropical experiment).

An important accomplishment during this year has been a unique application of models, in situ and satellite (TOMS and AVHRR) data to quantify causes of the observed south tropical Atlantic tropospheric ozone maximum in the GTE/TRACE-A aircraft mission period (September-October 1992). Major EOS-relevant results of these studies are summarized in the following paragraphs.

The section below summarizes some of the other activities supported by this IDS. These research efforts do not fall under the categories described above but are an important part of this investigation.

Heating rates computed with a radiation model and NMC temperature observations were used in a one-dimensional vortex interior descent model to determine diabatic descent rates for the fall and winter periods in the Northern Hemisphere for 1988-89 and 1991-94, and in the Southern Hemisphere for 1987 and 1992 [Rosenfield et al., 1995]. The computed descent rates generally agree well with observations of long-lived tracers [Rosenfield et al., 1994; Strahan et al., 1994], thus validating the radiative model. These results argue against the "flowing processor" concept of the polar vortex, which would require much larger cooling rates than those computed.

Several molecules important in the chemistry of the stratosphere photodissociate in the Schumann-Runge bands of oxygen, a spectral region in which the penetration of solar radiation into the middle atmosphere varies by several orders of magnitude as a function of wavelength. It has been suggested that a knowledge of the fine structure of the solar spectrum is therefore necessary for an accurate calculation of photolysis rates for these molecules. The SURE option proposed for the EOS SOLSTICE instrument was designed to provide measurements of the solar UV fine structure. Computations of the sensitivity of the computed photolysis rates to the solar spectral resolution show that knowledge of the fine structure in the Schumann-Runge region of the solar spectrum produces only a marginal (1 -2 %) difference in the computation of photolysis rates [Rosenfield, 1995]. As a result of these computations, we recommended that the EOS Payload Panel drop the high resolution UV spectrometer option for SOLSTICE.

An ongoing project is to study the radiative and dynamical effects of the Pinatubo volcanic aerosol. A parameterization of the optical thicknesses of both the background and the volcanic aerosol has been developed for use in our wide band radiative transfer model. Stratospheric Aerosol and Gas Experiment II (SAGE II) observations of one-micron extinctions, along with Mie calculations of absorption and extinction cross sections using observed particle size distributions for the sulfate aerosol, have been used. The volcanic aerosol perturbation was included in our 2-D interactive model by imposing monthly, latitudinally varying fields of aerosol extinction coefficients and surface area densities. The 2-D model studies of this volcanic perturbation are described in Section 2.2.5.1. Currently the aerosol fields which are imposed on the model are tied to 1 micron SAGE II extinctions and a single measured particle size distribution. We plan to improve the spatial and temporal distributions of the aerosols, and their absorption and extinction spectrum, by combining the SAGE II aerosol data set with other data sets, including Stratospheric Aerosol Measurement II (SAM II) and UARS.

The HIRDLS instrument on the EOS CHEM platform is designed to make horizontal and vertical observations at higher resolutions than have previously been made, while observing the upper troposphere and lower stratosphere with improved sensitivity and accuracy. The higher horizontal resolution is achieved by azimuthal scanning of the instrument's field of view. Previous limb-viewing sounders (LIMS, ISAMS, CLAES, MLS, etc.) did not have this azimuthal scanning capability and thus were unable to sample a given latitude circle more than twice per orbit.

In this study, we attempt to determine what degree of improvement HIRDLS' horizontal scanning capability yields in creating gridded maps of constituent fields. This is done by sampling model output using the anticipated HIRDLS sampling pattern, gridding the simulated satellite measurements thereby obtained, and comparing the resulting gridded fields to the originals.

One simulation, performed at SUNY, used as its original fields the output temperature of the Goddard STRATAN effort and ozone from the 3-D Chemical-Transport Model (CTM); these fields had a relatively low resolution (4° latitude by 5° longitude), so they were interpolated to a 2- by 2.5-degree grid before being sampled on the 85 and 10 mb pressure surfaces by a scanning and non-scanning modeled HIRDLS instrument. The 2- by 2.5-degree model fields were also put onto a 1- by 1-degree grid using a simple isentropic transport model; scanning and non-scanning HIRDLS sampling then were done on the 465 and 850 K potential temperature surfaces. Next, these simulated satellite soundings were used to reconstruct gridded horizontal maps via bilinear interpolation. The results for a single day (January 22, 1992) indicate, as expected, that the maps obtained from scanning HIRDLS samples exhibit more detail than in those derived from the non-scanning samples. In addition to visual inspection of the maps, root mean square (RMS) differences were calculated between the model ozone fields and the scanning HIRDLS' maps ("RMS-S"), and between the model ozone fields and the non-scanning HIRDLS' maps ("RMS-NS"); the former are about 20% lower than the latter. When calculated for temperature fields, on the other hand, RMS-NS values were about 30% lower than RMS-S, indicating that maps made from non-scanning HIRDLS samples are somewhat superior for temperature; the reason appears to be that the temperature field's broader-scale structures were oversampled by the scanning HIRDLS near the pole as they evolved with time. A more sophisticated gridding technique such as Kalman filtering, which takes into account the asynoptic nature of the data, might reduce this effect.

A second simulation used high resolution trace gas fields instead of the lower resolution model data; several days varying by season were examined instead of one day, and a measure of the statistical reliability of the results also has been performed. The high-resolution fields were simulated using the Reverse Domain Filling technique (described in section 2.2.3) to put nitrous oxide (N2O) measurements from the UARS CLAES instrument on a 1 by 1 degree grid for subsequent HIRDLS sampling. Three potential temperature surfaces were used: 465 K, 560 K, and 850 K, covering the lower to middle stratosphere. One day for each season in each hemisphere was selected for analysis and comparison.

Our work on solar proton events (SPEs) is also related to the overall goals of this IDS. SPEs can cause natural changes in the atmosphere on relatively short time-scales (days to months). We have investigated the effects of the extremely intense SPEs of October 1989 with both our 2-D and 3-D model. In Jackman et al. [1993, 1995] we noted the importance of properly representing the polar vortices and warming events and the importance of the interannual variations in the downward transport when studying the atmospheric effects of the SPEs weeks to months after the events. We also showed that our simulations of the polar NOx increases during the SPEs are close to observations (both rocket and SAGE II) and that these large SPEs can have a significant impact on polar lower stratospheric NOx a few months after the events. Such large natural perturbations to the polar stratosphere are the anthropogenically-caused polar changes observed in the Antarctic spring.

These are references which are not included in the list of IDS publications given in Section 7.

Fisher, M., and A. O'Neill, Rapid descent of mesospheric air into the stratospheric polar vortex, Geophys. Res. Lett., 20, 1267-1270, 1993.

Gleason, J., F., P. K. Bhartia, J. R. Herman, R. McPeters, P. A. Newman, R. S. Stolarski, L. Flynn, G. Labow, D. Larko, C. Seftor, C. Wellemeyer, W. D. Komhyr, A. J. Miller, and W. Planet, Record low global ozone in 1992, Science, 260, 523-526, 1993.

Hood, L. L, R. D. McPeters, J. P. McCormack, L. E. Flynn, S. M. Hollandsworth, and J. F. Gleason, Altitude dependence of stratospheric ozone trends based on Nimbus 7 SBUV data, Geophys. Res. Lett., 20, 2667-2670, 1993.

Justice C. O., J. D. Kendall, P. R. Dowty, and R. J. Scholes, Satellite remote sensing of fires during the SAFARI campaign using NOAA-AVHRR data, J. Geophys. Res., in press, 1995.

Randel, et al., Stratospheric transport from the tropics to middle latitudes by planetary wave mixing, Nature, 365, 533-537, 1993.

Schoeberl, M. R., et al., Reconstruction of the constituent distribution and trends in the Antarctic polar vortex from ER-2 flight observations, J. Geophys. Res., 94, 16815-16845, 1989.

Schoeberl, M. R., and L. R. Lait, Conservative coordinate transformations for atmospheric measurements, in Tools in Atmospheric Science, Proceedings of the International School of Physics "Enrico Fermi", G. Visconti and J. Gille, Editors, Italian Physical Society, 1992.

Stolarski, R. S., P. Bloomfield, R. D. McPeters, and J. R. Herman, Total ozone trends deduced from Nimbus 7 TOMS data, Geophys. Res. Lett., 19, 159-162, 1991.

Sutton, R. T., H. Maclean, R. Swinbank, A. O'Neill, F. W. Taylor, High resolution stratospheric tracer fields estimated from satellite observations using Lagrangian trajectory calculations, J. Atmos. Sci., 51, 2995-3005, 1994.

Weaver, C. J., A. R. Douglass, and R. B. Rood, Thermodynamic balance of three-dimensional stratospheric winds derived from a data assimilation procedure, J. Atmos. Sci., 50, 2987-2993, 1993.

WMO, Scientific Assessment of Ozone Depletion: 1994, Report No. 37, World Meteorological Organization Global Ozone Research and Monitoring Project, 1995.

Woodbridge, E. L. et al., Estimates of total organic and inorganic chlorine in the lower stratosphere from in situ and flask measurements during AASE II, J. Geophys. Res., 100, 3057-3064, 1995.

This IDS has performed a number of programmatic duties associated with the EOS effort. Dr. Schoeberl was the first Atmospheres Panel chairman (1990-1993) and became the first EOS CHEM Project Scientist for most of FY 1994. Dr. Gleason, was added to the IDS team in 1994 and became the EOS CHEM Project Scientist in August 1994.

This IDS has been heavily involved in the EOS restructuring/rebaselining/reshaping programs. For example, we have conducted and are performing specific instrument studies for the Payload Panel (see Sections 2.5.1, 2). Drs. Newman and Lait have served on EOSDIS committees. In July 1994, Dr. McNeal, the HQ Program Scientist, and our IDS sponsored a workshop to familiarize the science community with measurements on EOS CHEM. The workshop report has been published in the Earth Observer. This IDS is now involved in the 1995 EOS reshape activity, the PI is the lead author of Chapter 9 of the Science Implementation Plan.

This IDS presently produces two data products. First, we generate and transfer to the DAAC the NMC balance wind data set which includes heights, balanced winds, temperatures, and potential vorticity. Transfer of the data set from 1979-August 1995 will start in September, 1995; currently we have nearly finished debugging the transfer and conversion software. Second, this IDS supports the GSFC Automailer trajectory model. The automailer is a scheme by which NASA and non NASA users can generate forward and back trajectories for analysis of aircraft and satellite data. The automailer also supports visualization of meteorological data files - support for that activity is under the R&A program. To use the automailer, the requester e-mails a request to a special account. This starts a job on one of the EOS supported workstations which computes the trajectory using NMC balanced winds. The results are then e-mailed back to the requester. This facility will soon be available on our home page. Appendix 3.2-1 shows the national and international usage of the GSFC Automailer.

Early in this IDS investigation we developed a self documenting data formatting scheme called DF [Lait et al., 1993]. This scheme is similar to HDF (although HDF was developed at the time, there were few tools for HDF). The DF scheme has been very popular and we have used it to provide general access to satellite, aircraft and ground-based data sets within the IDS. Our experience with DF has given us valuable insights into self-documenting storage schemes.

Most of the co-investigators are located at GSFC and are collocated. The exceptions are Dr. Hudson at the University of Maryland, Dr. Geller at the University of New York at Stony Brook, and Dr. Cohn who is located at the DAO off-site facility. The team has formal meetings roughly quarterly, but communicates informally every day as needed.

Within the IDS, the PI assumes the responsibility for overall research activities. As indicated in Figure 1.1-1 and 1.1-2, individual team members work on various aspects of the project. Dr. Rood is in charge of the data assimilation component, while Dr. Douglass works on the 3-D chemical model, the Lagrangian chemical model, and UARS data analysis. Dr. Jackman is in charge of the 2-D modeling work and Dr. Rosenfield heads the group effort on the interactive 2-D model. Dr. Lait, who is currently working on the HIRDLS sampling pattern with Dr. Geller, is also responsible for maintenance of the IDS home page and the trajectory automailer. Dr. Lait also supports aircraft mission data analysis and NMC analysis. Dr. Stolarski, Dr. Newman, and Dr. Gleason work on the analysis of TOMS data. Dr. Newman also analyses aircraft and UARS data and is in charge of moving the NMC balanced wind data to the Goddard DAAC. Dr. Thompson works on tropospheric chemistry. Dr. Hudson is developing tropospheric ozone retrieval algorithms.

5.1 Recent Changes

With the availability of UARS data, the IDS has shifted much of its focus from aircraft data and NMC analysis to UARS and assimilation data analysis. Both of these changes have been made because of the wider availability and improved quality of both UARS and assimilation data sets. Research directions have also changed with the increase in workstation computer power, cheap mass storage in the form of 10 gigabyte disk drives, and the availability of the new Interactive 2-D model and Lagrangian chemical model tools. This shift has allowed us to plan and undertake investigations (such as MODE, section 2.1) that were previously only possible with the more computationally costly 3-D model.

In general, our research focus is shifting away from polar processes toward understanding the mechanism producing the mid-latitude ozone trends. We have also begun to focus on the lower stratosphere, especially the processes associated with strat-trop exchange, tropical mid-latitude interaction, and upper tropospheric physical processes. This change in focus draws closer together the troposphere and the stratosphere chemical efforts, and is phased to take advantage of the availability of MOPPIT observations on EOS AM as well as data from the STRAT ER-2 missions. Over the next two years we will be completing the MODE effort and improving the interactive 2-D model's troposphere and mesosphere. We intend to apply the trajectory mapping technique to a wider range of UARS data such as investigating the NOy budget in a manner similar to the Cly analysis of Dessler et al. [1995], and the searching for filamentary structures in the high horizontal resolution ATLAS - CHRISTA limb sounding data. Our investigation of EOS instrument performance will also continue.

A number of the tools we have developed for the stratosphere are currently being tested in the troposphere. Recently we have applied the RDF technique to tropospheric water vapor observed by GOES. We find that the fine scale structure in the upper tropospheric water vapor seen by GOES can be well simulated using assimilation analysis (or forecasts) augmented by 3 day RDF calculations. This effort is actually part of a broader research effort we have begun with the Hartmann IDS and Dr. James Anderson at Harvard University, to understand the role of water vapor in the tropical upper tropopause using the Perseus remotely piloted aircraft (RPA).

Since this IDS task was begun (in 1990) there has been considerable progress. The scientific direction remains the same: the isolation of man-made from natural chemical changes in the atmosphere and the understanding of their mechanisms. But, we have broadened our scope to include tropospheric chemical processes, and we are branching out to begin studying water vapor in the upper troposphere using our stratospheric transport tools. Our overall focus has been on tool and model development for interpretation of EOS and non-EOS data. We also have a very close collaboration with the EOS data assimilation effort. Our most active current research focus is on the analysis of available satellite and aircraft data sets (UARS, TOMS, STRAT, SPADE, etc.). Two new models have been recently developed under this IDS, the Lagrangian chemical model and the coupled 2-D model. We support development efforts in radiative transfer, the 3-D chemical model, and the trajectory model. Our present data products include balanced wind, potential vorticity and height fields from NMC data, and trajectories to order from the GSFC trajectory automailer.

Our IDS effort has been very active within the EOS program. One of our members is the EOS CHEM Project Scientist, the PI has headed the Atmospheres Panel, has been involved in several of the EOS rescope activities, and is in charge of a Science Implementation Plan Chapter. Our Co-Is head the EOS data assimilation panel and serve on EOSDIS advisory committees. We also have an active program in instrument evaluation with an eye to efficient observing strategy or instrument problems. Our IDS currently supports a post-doc at GSFC and a student at Stony Brook.

Our near term future research activities involve continued analysis of available satellite and aircraft data, a larger focus on stratosphere-troposphere interaction, and a tropospheric chemical modeling.

(all 53 of these references were sponsored or co-sponsored by this IDS)

Allen, D., R. B. Rood, A. M. Thompson, and R. D. Hudson, Three-dimensional Rn-22 calculations using assimilated data and a convective mixing algorithm, submitted to J. Geophys. Res., 1995.

Bacmeister, J. T., M. R. Schoeberl, M. E. Summers, J. E. Rosenfield, and X. Zhu, Descent of long-lived trace gases in the winter polar vortex, J. Geophys. Res., 100, 11669-11684, 1995.

Chappellaz, J. A., I. Y. Fung, and A. M. Thompson, Atmospheric methane increase since the last glacial maximum, 1. Source, Estimates, Tellus, 45B, 228-241, 1993.

Dessler, A. E. et al., Correlated observations of HCl and ClONO2 from UARS and implications for stratospheric chlorine partitioning, Geophys. Res. Lett., 22, 1721-1724, 1995.

Douglass, A., R. Rood, J. Waters, L. Froidevaux, W. Read, L. Elson, M. Geller, Y. Chi, M. Cerniglia and S. Steenrod, A 3-D simulation of the early winter distribution of reactive chlorine in the north polar vortex, Geophys. Res. Lett., 20, 1271-1274, 1993.

Douglass, A. R., C. J. Weaver, R. B. Rood, and L. Coy, A three-dimensional simulation of the ozone annual cycle using winds from a data assimilation system, J. Geophys. Res., in press, 1995a.

Douglass, A. R., M. R. Schoeberl, R. S. Stolarski, J. W. Waters, J. M. Russell III, and A. E. Roche, Inter-hemispheric differences in springtime deactivation of vortex ClO, J. Geophys. Res., 100, 133967-13978, 1995b.

Hudson, R. D., J. Kim, and A. M. Thompson, On the derivation of tropospheric column ozone from radiances measured by the Total Ozone Mapping Spectrometer, J. Geophys. Res., 100, 11137-11145, 1995.

Jackman, C. H., J. E. Nielsen, D. J. Allen, M. C. Cerniglia, R. D. McPeters, A. R. Douglass, and R. B. Rood, The effects of the October 1989 solar proton events on the stratosphere as computed using a three-dimensional model, Geophys. Res. Lett., 20, 459-462, 1993.

Jackman, C. H., M. C. Cerniglia, J. E. Nielsen, D. J. Allen, J. M. Zawodny, R. D. McPeters, A. R. Douglass, J. E. Rosenfield, and R. B. Rood, Two-dimensional and three-dimensional model simulations, measurements, and interpretation of the influence of the October 1989 solar proton events on the middle atmosphere, J. Geophys. Res., 100, 11641-11660, 1995.

Jacob, D. J., et al., The origin of ozone and NOx in the tropical troposphere: A photochemical analysis of aircraft observations over the South Atlantic Basin, submitted to J. Geophys. Res., 1995.

Kawa, S. R., D. W. Fahey, J. C. Wilson, M. R. Schoeberl, A. R. Douglass, R. S. Stolarski, E. L. Woodbridge, H. Jonsson, L. R. Lait, P. A. Newman, M. H. Proffitt, D. W. Toohey, D. E. Anderson, M. Loewenstein, K. R. Chan, C. R. Webster, R. D. May, and K. K. Kelly, Interpretation of NOx/NOy Observations from AASE-II using a model of chemistry along trajectories, Geophys. Res. Lett., 20, 2507-2510, 1993.

Kawa, S. R., J. Kumer, A. Douglass, A. Roche, S. Smith, F. Taylor, and D. Allen, Missing chemistry of reactive nitrogen in the upper stratospheric polar vortex, Geophys. Res. Lett., in press, 1995.

Kim, J. H., R. D. Hudson, and A. M. Thompson, Derivation of time-averaged tropospheric column ozone from radiances measured by the Total Ozone Mapping Spectrometer: Intercomparison and analysis, submitted to J. Geophys. Res., 1995a.

Kim, J. H., R. D. Hudson, and A. M. Thompson, A new method of deriving tropospheric column ozone from TOMS radiances: October 1989 and 1992, in Biomass Burning and Global Change (Chapman Conference Book), J. S. Levine, Editor, submitted, 1995b.

Lait, L. R., E. R. Nash and P. A. Newman, DF: A proposed data format standard, NASA Tech. Memo., 4467, 1993.

Lait, L. R. , An alternative form of potential vorticity, J. Atmos. Sci., 51, 1754-1759, 1994.

Lehmann, P. , D. J. Karoly, P. A. Newman, T. S. Clarkson, and W. A. Matthews, Long-term winter total ozone changes at Macquarie Island, Geophys. Res. Lett., 19, 1459-1462, 1992.

Lyster, P. M., S. E. Cohn, R. Menard, L.-P. Chang, S.-J. Lin, and R. Olsen, An implementation of a two-dimensional filter for atmospheric chemical constituent assimilation on massively parallel computers, submitted to Mon. Wea. Rev., 1995.

Morris, G. et al., Trajectory mapping and applications to data from the upper atmosphere research satellite, J. Geophys. Res., in press, 1995.

Nash, E. R., P. A. Newman, J. E. Rosenfield, and M. R. Schoeberl, An objective determination of the polar vortex using Ertel's potential vorticity, submitted to J. Geophys. Res., 1994.

Newman, P. A., and M. R. Schoeberl, A reinterpretation of the data from the NASA Stratosphere-Troposphere Exchange Project, Geophys. Res. Lett., in press, 1995.

Newman, P. A., Antarctic total ozone in 1958, Science, 264, 543-546, 1994.

Nielsen, J. E., R. B. Rood, A. R. Douglass, M. C. Cerniglia, D. A. Allen, Loewenstein, M., J. Podolske, D. Fahey, E. Woodbridge, P. Tin, A. Weaver, P. Newman, S. Strahan, S. Kawa, M. Schoeberl, and L. Lait, New observations of the NOy/N2O correlation in the lower stratosphere, Geophys. Res. Lett., 20, 2531-2534, 1993.

Pickering, K. E. , A. M. Thompson, D. P. McNamara, and M. R. Schoeberl, An intercomparison of isentropic trajectories over the South Atlantic, Monthly Wea. Rev., 122, 864-897, 1994.

Pickering, K. E., A. M. Thompson, W-K. Tao, R. B. Rood, D. P. McNamara, and A. M. Molod, Vertical Transport by convective clouds: Comparisons between cloud-scale and global-scale models, Geophys. Res. Lett., 22, 1089-1092, 1995a.

Pickering, K. E., A. M. Thompson, Y. Wang, W-K. Tao, D. P. McNamara, V. W. J. H. Kirchhoff, B. G. Heikes, G. W. Sachse, J. D. Bradshaw, G. L. Gregory, and D. R. Blake, Convective transport of biomass burning emissions over Brazil during TRACE-A, submitted to J. Geophys. Res., 1995b.

Plumb, R. A., D. W. Waugh, R. J. Atkinson, P. A. Newman, L. R. Lait, M. R. Schoeberl, E. V. Browell, A. J. Simmons, M. Loewenstein, and D. W. Toohey, Intrusions into the lower stratospheric Arctic vortex during the winter of 1991/92, J. Geophys. Res., 1993.

Redaelli, G. , L. Lait, M. Schoeberl, P. A. Newman, G. Visconti, A. d'Alturio, F. Masci, V. Rizi, L. Froidevaux, J. W. Waters, A. J. Miller, UARS MLS O3 soundings compared with lidar measurements using the conservative coordinates reconstruction technique, Geophys. Res. Lett., 21, 1535-1538, 1994.

Rosenfield, J. E., The radiative feedback of polar stratospheric clouds on Antarctic temperatures, Geophys. Res. Lett., 20, 1195-1198, 1993.

Rosenfield, J. E., P. A. Newman, and M. R. Schoeberl, Computations of diabatic descent in the stratospheric polar vortex, J. Geophys. Res., 99, 16677-16689, 1994.

Rosenfield, J. E., The sensitivity of stratospheric photodissociation rates to the solar spectral resolution in the Schumann-Runge Bands, J. Atm. Terr. Phys., 57, 843-855, 1995.

Schoeberl, M. R., and D. L. Hartmann, The dynamics of the stratospheric polar vortex and its relation to the springtime ozone depletions, Science, 251, 46-52, 1991.

Schoeberl, M. R., R. S. Stolarski, A. R. Douglass, P. A. Newman, L. R. Lait, J. W. Waters, L. Froidevaux, and W. G. Read, MLS ClO observations and Arctic polar vortex temperatures, Geophys. Res. Lett., 20, 2861-2864, 1993a.

Schoeberl, M. R., A. R. Douglass, R. S. Stolarski, P. A. Newman, L. R. Lait, D. Toohey, L. Avallone, J. G. Anderson, W. Brune, D. W. Fahey, and K. Kelly, The evolution of ClO and NO along air parcel trajectories, Geophys. Res. Lett., 20, 2511-2514, 1993b.

Schoeberl, M. R. S. D. Doiron, L. R. Lait, P. A. Newman, A. J. Krueger, A simulation of the Cerro Hudson SO2 cloud, J. Geophys. Res., 98, 2949-2955, 1993c.

Schoeberl, M. R., M. Luo, J. M. Russell III, and J. E. Rosenfield, An analysis of the Antarctic HALOE trace gas observations, J. Geophys. Res., 100, 5159-5172, 1995.

Schoeberl, M. R., and L. C. Sparling, Trajectory modeling, diagnostic tools in Atmospheric Physics, Proceedings of the International School of Physics "Enrico Fermi", G. Fiocco and G. Visconti, Editors, Italian Physical Society, 289-304, 1995.

Schoeberl, M. R., and P. A. Newman, A multiple level trajectory analysis of vortex filaments, J. Geophys. Res., in press, 1995.

Sieber, C., J. H. Kim, R. D. Hudson, and A. M. Thompson, Time-averaged tropospheric ozone derived from TOMS radiances: A comparison of maps for the tropical Atlantic from 1-15 Oct. 1989 and 1-15 Oct. 1992, Eos, Trans. AGU, 25 Apr. 1995 Suppl., S72, 1995.

Smyth, S., et al., Factors influencing the upper free tropospheric distribution of reactive nitrogen over the south Atlantic during the TRACE-A experiment, submitted to J. Geophys. Res., 1995.

Strahan, S. E., J. E. Rosenfield, M. Loewenstein, J. R. Podolske, and A. Weaver, The evolution of the 1991-2 Arctic vortex and comparison with the GFDL `SKYHI' general circulation model, J. Geophys. Res., 99, 713-723, 1994.

Talbot, R., et al., Chemical characteristics of continental outflow over the tropical south Atlantic Ocean from Brazil and southern Africa, submitted to J. Geophys. Res., 1995.

Thompson, A. M., J. A. Chappellaz, I. Y. Fung, and T. L. Kucsera, Atmospheric methane increase since the last glacial maximum, 2. Interactions with oxidants, Tellus, 45B, 242-257, 1993a.

Thompson, A. M., K. E. Pickering, D. P. McNamara, and R. D. McPeters, Effect of marine stratocumulus on TOMS ozone, J. Geophys. Res., 98, 23051-23057, 1993b.

Thompson, A. M., Aspects of modeling the tropospheric hydroxyl radical concentration, Israel J. Chem., Special Issue on Atmospheric Chemistry, 34, 277-287, 1994a.

Thompson, A. M., Measuring and modeling the tropospheric hydroxyl radical (OH), J. Atmos. Sci., Special AMS OH Symposium Issue, in press, 1994b.

Thompson, A. M., Photochemical Modeling of Chemical Cycles: Issues related to the interpretation of ice core data, in Biogeochemical Cycles and Ice Cores, R. Delmas, Editor, Springer-Verlag, in press, 1995.

Thompson, A. M., K. E. Pickering, D. P. McNamara, M. R. Schoeberl, R. D. Hudson, J. H. Kim, E. V. Browell, J. Fishman, V. W. J. H. Kirchhoff, and D. Nganga, Where did tropospheric ozone over southern Africa and the tropical Atlantic come from in October 1992? Insights from TOMS, GTE/TRACE-A and SAFARI-92, submitted to J. Geophys. Res., 1995a.

Thompson, A. M., R. D. Diab, G. E. Bodeker, M. Zunckel, G. Coetzee, C. Archer, K. E. Pickering, D. P. McNamara, J. Combrink, J. Fishman, and D. Nganga, Total ozone over Southern Africa and the adjacent Atlantic during SAFARI-92, J. Geophys. Res., SAFARI Special Issue, in press, 1995b.

Thompson, A. M., T. Zenker, G. E. Bodeker, and D. P. McNamara, Ozone over southern Africa: Patterns and influences, in Fire in Southern African Savanna: Ecological and Atmospheric Perspectives, J. A. Lindesay, M. O. Andreae, P. D. Tyson, and B. van Wilgen, Editors, Univ. of Witwatersrand Press, in press, 1996.

Waugh, W. D., R. A. Plumb, R. J. Atkinson, M. R. Schoeberl, L. R. Lait, P. A. Newman, M Loewenstein, D. W. Toohey, and C. R. Webster, Transport of material out of the stratospheric Arctic vortex by Rossby Wave Breaking, J. Geophys. Res., 1993.

Wang, Y., W-K. Tao, K. E. Pickering, A. M. Thompson, R. Adler, J. Simpson, P. Keehn, G. Lai, Mesoscale (MM5) simulations of TRACE-A and PRE-STORM convective events, submitted to J. Geophys. Res., 1995.

9.0 SUMMARY OF OUR MOST SIGNIFICANT RECENT SCIENTIFIC FINDINGS

The list below summarizes our most recent and significant recent scientific findings.

(1) We believe that we have discovered the explanation for the observed asymmetry in ozone trends in the upper stratosphere. The differences are apparently due to the different dynamics in the two hemispheres. The larger, broader descent over the Antarctic winter pole leads to lower methane amounts compared to the Arctic. This is a finding from the new Interactive 2-D model which was developed under this IDS (Section 2.2.5.2, Fig. 2.2.5.2-1). This work is currently being prepared for publication.

(2) Our second major discovery is of the anomalous growth in HCl inside the Antarctic vortex after the ozone depletion [Douglass et al., 1995]. This discovery came from our work with the UARS data, and the use of PV analysis tools and the Lagrangian chemical model that were developed by this IDS. Our analysis showed that once ozone disappears in the Antarctic polar vortex, the balance between Cl and ClO shifts toward Cl. Cl then attacks methane forming HCl. The HCl rise is observed in the UARS HALOE data. This result was later confirmed by the ASHOE/MAESA aircraft expedition (Section 2.2.2, Figs. 2.2.2-1,2).

(3) Our third significant result is the first quantitative simulation of the historical Antarctic ozone hole. This study uses the new Lagrangian chemical model combined with UARS data. Our simulation shows that the Antarctic ozone depletion development matches observations from UARS. Using chlorine estimates from previous years, we have been able to show that the secular decline in Antarctic ozone is consistent with TOMS observations and that dynamics plays little role in the secular trend (Section 2.1, Figs. 2.1-1,2). This work is currently being prepared for publication.

Appendix 3.2-1

                          GSFC /science Automailer Usage Report
                            Covering 1994-01-01 to 1994-12-31


                                       USER  ACCESSES

                      cadyp@aer.com    16	           johnson@grizzly.uwyo.edu   134
                  wyojim@sovusa.com     3	                 zhao@wolf.uwyo.edu    60
      zhang@asrcss2.asrc.albany.edu   152	        deshler@mcmsun5.mcmurdo.gov   348
                  atmophys@uwyo.edu     5	       voemelho@mcmsun5.mcmurdo.gov   896
                  awhitten@uwyo.edu    13	          hamill@light.arc.nasa.gov    15
          lj@mercu1.gps.caltech.edu    32	              taba@sky.arc.nasa.gov    48
       cbrock@cassandra.cair.du.edu    48	         westphal@halo.arc.nasa.gov    19
     manderbe@cassandra.cair.du.edu    25	  huahu@laserspec1.cc.espo.nasa.gov     1
         psulliva@diana.cair.du.edu    12	      lait@triffid.cc.espo.nasa.gov     4
             xliu@diana.cair.du.edu     6	        root@notus.cc.espo.nasa.gov     3
          dan@bottesini.harvard.edu     5	      theory@fermi.cc.espo.nasa.gov    23
       elliot@bottesini.harvard.edu    32	           gregg@skye.gsfc.nasa.gov     1
         eric@bottesini.harvard.edu    17	          huahu@vs4000.jpl.nasa.gov     9
             ewg@triton.harvard.edu    48	          jjm@mark4sun.jpl.nasa.gov     1
             ham@triton.harvard.edu     2	          chip@mirage.larc.nasa.gov    20
          hintsa@huarp2.harvard.edu     1	         hervig@teton.larc.nasa.gov   278
             kab@triton.harvard.edu    10	        mcinerny@hops.larc.nasa.gov    27
          theory@triton.harvard.edu     1	             bjohnson@cmdl.noaa.gov     6
                    psulliva@du.edu     7	        johnson@cmdl1.cmdl.noaa.gov     1
             dcheng@uars.sunysb.edu   824	               voemel@cmdl.noaa.gov     5
          dshindell@uars.sunysb.edu    28	          s107a.mcmurdo@mcmurdo.gov    17
            lemmons@uars.sunysb.edu    20	          s148b.mcmurdo@mcmurdo.gov    13
           screwell@uars.sunysb.edu    42	         adriani@hp.ifsi.fra.cnr.it    13
             vyudin@uars.sunysb.edu     1	        didonfra@hp.ifsi.fra.cnr.it    13
              xpeng@uars.sunysb.edu    72	          fromm@poam_a.nrl.navy.mil    99
               ychi@uars.sunysb.edu   128	        hornstei@poamb.nrl.navy.mil     5
                jamesw@acd.ucar.edu    47	             mas@atlas.nrl.navy.mil    29
             katja@ash.mmm.ucar.edu   150	           poam@poam_a.nrl.navy.mil     1
             renate@meeker.ucar.edu    49	            coetzee@aqua.ccwr.ac.za    15
              hervig@dingo.uwyo.edu    14	         coetzee@cirrus.sawb.gov.za    62

                         TOTALS:    60  users,        3976 accesses



                                     FUNCTION  ACCESSES
                         
                                     plot_met  1622
                                   trajectory  1357
                                      metmaps   478
                                   metprofile   329
                         trajectory curt mail    68
                                    metxsects    67
                                      curtain    33
                                   nmc_status    22
                         
                                       TOTAL:  3976

This averages to about 11 jobs submitted per day. Emphasis denotes support by this IDS.

_______________________________