Richard S. Eckman

An intercomparison of model ozone deficits in the upper stratosphere and mesosphere from two data sets

We have compared a diurnal photochemical model of ozone with nighttime data from the limb infrared monitor of the stratosphere (LIMS) and ground-based microwave observations. Consistent with previous studies, the model underpredicts the observations by about 10–30%. This agreement is strong confirmation that the model ozone deficit is not simply an artifact of observational error since it is unlikely to occur for two completely different ozone data sets. We have also examined the seasonal, altitudinal, and diurnal morphology of the ozone deficit. Both comparisons show a deficit that peaks in the upper stratosphere (2–3 mbar) and goes through a minimum in the lower mesosphere from 1.0 to 0.4 mbar. At lower pressures (<0.2 mbar) the deficit appears to increase again. The seasonal variation of the deficit is less consistent. The deficit with respect to the LIMS data is least in winter while with respect to the microwave data, the deficit shows little seasonal variation. Finally, the night-to-day ratio in our model is in generally good agreement with that seen in the microwave experiment. Increasing the rate coefficient for the reaction O + O2 + M → O3 + M improves the fit, while a very large (50%) decrease in the HOx catalytic cycle is not consistent with our observations. Increasing the atomic oxygen recombination rate also improves the overall agreement with both data sets; however, a residual discrepancy still remains. There appears to be no single chemical parameter which, when modified, can simultaneously resolve both the stratospheric and mesospheric ozone deficits.

Response of middle atmosphere chemistry and dynamics to volcanically elevated sulfate aerosol: Three‐dimensional coupled model simulations

The NASA Langley Research Center Interactive Modeling Project for Atmospheric Chemistry and Transport (IMPACT) model has been used to examine the response of the middle atmosphere to a large tropical stratospheric injection of sulfate aerosol, such as that following the June 1991 eruption of Mount Pinatubo. The influence of elevated aerosol on heterogeneous chemical processing was simulated using a three-dimensional climatology of surface area density (SAD)developed using observations made from the Halogen Occultation Experiment, Stratospheric Aerosol and Gas Experiment II, and Stratospheric Aerosol Measurement satellite instruments beginning in June 1991. Radiative effects of the elevated aerosol were represented by monthly mean zonally averaged heating perturbations obtained from a study conducted with the European Center/Hamburg (ECHAM4) general circulation model combined with an observationally derived set of aerosol parameters. Two elevated-aerosol simulations were integrated for 31/2 years following the volcanic injection. One simulation included only the aerosol radiative perturbation, and one simulation included both the radiative perturbation and the elevated SAD. These perturbation simulations are compared with multiple-year control simulations to isolate relative contributions of transport and heterogeneous chemical processing. Significance of modeled responses is assessed through comparison with interannual variability. Dynamical and photochemical contributions to ozone decreases are of comparable magnitude. Important stratospheric chemical/dynamical feedback effects are shown, as ozone reductions modulate aerosol-induced heating by up to 10% in the lower stratosphere and 25% in the middle stratosphere. Dynamically induced changes in chemical constituents which propagate into the upper stratosphere are still pronounced at the end of the simulations.

Polar ozone depletion: A three-dimensional chemical modeling study of its long-term global impact

The export of ozone-poor air from the polar region following the breakup of the southern hemisphere polar vortex is examined with a three-dimensional chemistry transport model. This volume of depleted ozone, the result of chemical processing during the southern wintertime and springtime, is long-lived in the lower stratosphere and can affect ozone concentrations at southern middle latitudes following its transport out of the polar region. Two 5-year simulations were performed utilizing the NASA Langley Research Center three-dimensional chemistry transport model. One simulation included only gas phase and sulfate aerosol chemistry, while the second simulation also included reactions occurring on polar stratospheric clouds (PSCs). The model-calculated seasonal variation of southern hemispheric O3, HNO3, and active chlorine as a result of PSC chemistry is in reasonable accord with satellite observations. The model reveals that ozone is transported equatorward following the breakup of the polar vortex to approximately 20°S latitude by the first southern summer following the activation of PSC chemistry. A residual column-integrated ozone depletion of 9% remained by the springtime of the second year. In subsequent years, the southern ozone hole itself increased in depth from a column-integrated depletion of 37% in the first year to 43% in the fifth year with respect to the baseline simulation with no PSC chemistry. The isopleths of column-integrated ozone loss showed a slow equatorward movement during the 5-year run. These model results, in general agreement with earlier model studies using parameterized chemistry, show that a potential exists for a long-term accumulation of ozone loss in the southern polar region and a gradual increase in the global impact of polar ozone depletion. Comparison with satellite and ground-based observations of ozone trends at midlatitudes suggests that ozone dilution may be a contributing factor. Experiments were performed to examine the sensitivity of the rate of local ozone recovery following the breakup of the vortex to the depth and spatial extent of the denitrification of polar air. These simulations revealed that deeper denitrification led to a more persistent column-integrated ozone loss and a slight increase in its equatorward progression.

Microwave observations and modeling of O2(1Δg) and O3 diurnal variation in the mesosphere

The first microwave measurements of an electronically excited molecular species in the Earths atmosphere are presented. Local thermodynamic equilibrium (LTE) rotational line emission from mesospheric O2(1Δg) was observed at a frequency of 255.01794 GHz (λ∼1.2 mm), employing the National Radio Astronomy Observatory (NRAO) millimeter facility at Kitt Peak, Arizona (32°N, 111°W). The pressure-broadened line shapes of the O2(1Δg) spectra, which were obtained in January and April 1992 and in January and November 1993, are inverted to retrieve O2(1Δg) mixing profiles over the 50–70 km altitude region. The observed daytime abundances exceed ozone abundances in the lower mesosphere, which are separately retrieved with coincident O3 spectral line (249.7886 GHz) observations. The January and November 1993 observations are binned into 20–60 min time intervals to study O2(1Δg) diurnal behavior. Derived abundances of O2(1Δg) between 50 and 70 km for the four observation dates are 9%, 31%, 3%, and 26%, respectively, each ±10% higher than predicted, based on the simple photochemistry of lower mesospheric O2(1Δg). Modeled variation of [O2(1Δg)] with time of day agrees with observed variation in that the observed difference between model and data abundances is constant throughout the daylight hours of each observation date. Model underprediction of [O2(1Δg)] is consistent with similar model underprediction of mesospheric [O3]. A perturbation to the photochemical model that forces decreased ozone chemical loss brings brings both model [O3] and [O2(1Δg)] into agreement with the observations. O2(1Δg) abundances derived from these 1.2 mm observations agree with [O2(1Δg)] values derived from comparable SME observations of the 1.27 μm emission, with assumption of a 3880 s O2(1Δg) radiative lifetime [Badger et al., 1965]. The 6800 s O2(1Δg) radiative lifetime proposed by Mlynczak and Nesbitt [1995] is ruled out by the similar comparison.

Photodissociation of O2 and H2O in the middle atmosphere: Comparison of numerical methods and impact on model O3 and OH

We have compared three photochemical diurnal models of O3 and OH in the upper stratosphere and mesosphere which use different techniques for calculating the absorption of solar ultraviolet radiation by the O2 Schumann-Runge bands. One model uses a detailed line-by-line representation of the O2 cross section from 1750–2050 A, while the two others use lower resolution, parameterized cross sections. Using the parameterized cross sections, the calculated O3 profiles for both day and night agree with those obtained from the line-by-line model to within 6%. This appears to eliminate inaccuracies in the parameterized O2 cross section as a major cause of previously reported model O3 deficits. A portion of the residual differences from the line-by-line model are attributed to inaccuracies in the calculated H2O photolysis rate. A parameterized H2O cross section is offered which improves the accuracy of this calculation.

Effect of the HITRAN 92 spectral data on the retrieval of NO2 mixing ratios from Nimbus 7 LIMS

To ensure spectral consistency when comparing Nimbus 7 LIMS NO2 distributions with those from ATMOS and UARS, 1 day (May 5, 1979) of LIMS measurements were reprocessed using the NO2 line list on the HITRAN 92 tape compiled by AFGL. The revised NO2 mixing ratios are smaller by up to 20%. The decrease is not constant with height, latitude, or time of day but depends on the absolute amount of NO2 in the profile, as a result of a change in the degree of saturation for the strong NO2 spectral lines. The revised NO2 agrees better with correlative measurements and with NO2 distributions from the SAGE and HALOE satellite experiments but not with those from ATMOS 85. Profiles of the day/night ratio of revised NO2 are now larger near 5 hPa. There is also some improvement between observed and modeled ozone in the upper stratosphere, when the revised nighttime NO2 profile is used as the estimate of NOy for the model calculations.

Dynamical climatology of the NASA Langley Research Center Interactive Modeling Project for Atmospheric Chemistry and Transport (IMPACT) model

A comparison of the NASA Langley Research Center (LaRC) Interactive Modeling Project for Atmospheric Chemistry and Transport (IMPACT) models dynamical characteristics with assimilated data sets and observations is presented to demonstrate the ability of the model to represent the dynamical characteristics of Earths troposphere and stratosphere. The LaRC IMPACT model is a coupled chemical/dynamical general circulation model (GCM) of the Earths atmosphere extending from the surface to the lower mesosphere. It has been developed as a tool for assessing the effects of chemical, dynamical, and radiative coupling in the stratosphere on the Earths climate. The LaRC IMPACT model winds and temperatures are found to be in fairly good agreement with Upper Atmospheric Research Satellite (UARS) United Kingdom Meteorological Office (UKMO) assimilated winds and temperatures in the lower stratosphere. The model upper stratospheric zonal mean temperatures are also in good agreement with the UARS-UKMO climatology except for a cold winter pole which results from the upward extension of the cold vortex temperatures and an elevated winter stratopause in the model. The cold pole bias is consistent with the overprediction of the winter stratospheric jet strength, and is characteristic of stratospheric GCMs in general. The model northern and southern hemisphere stratospheric eddy heat and momentum fluxes are within the expected interannual variability of the UARS-UKMO climatology. The combined effects of water vapor transport, radiative, convective, and planetary boundary layer parameterizations are shown to produce tropospheric winds and circulation statistics that are in good agreement with the UARS-UKMO climatology, although the model tropopause and upper tropospheric temperatures are generally cold relative to the UARS-UKMO temperatures. Comparisons between the model and UARS-UKMO climatology indicate that the model does a reasonable job in reproducing the frequency of observed synoptic-scale storms during the northern and southern hemisphere winters. Generally good agreement is found between the model and observations in the distribution of outgoing longwave radiation and precipitable water. However, the model precipitation and cloud distributions are influenced by spectral truncation errors which indicate that the T32 spectral resolution of the model is probably not adequate to accurately represent coupling between localized convection and large-scale water vapor transport. The agreement between the observed and model stratospheric circulation and temperatures, reasonableness of the model stratospheric wave driving, and stability of the model climatology provides confidence that the LaRC IMPACT model is appropriate for multiyear coupled radiation/chemistry/dynamics studies of the stratosphere.

Application of Satellite Sensor Data and Models for Energy Management

Effective, environmentally sound development, production, and delivery of energy depend on Earth monitoring information. Satellite remote sensing data and products provide unique, objective information that has the additional advantage of yielding global, homogeneous, and repetitive coverage. Satellite remote sensing data and products have been used extensively in parts of the energy sector for applications ranging from climatology to identification of solar and wind energy sources, yet there is significant potential to expand energy applications. This paper discusses the key energy sector organizations and decision-support tools with the greatest potential to benefit from new applications of satellite remote sensing data, identifies relevant remote sensing data and products with a focus on NASA Earth science resources, and provides examples that show the added value of the Earth observations. These examples come from the application of NASA data to solar energy information needs. Although continued work for support of solar energy is warranted, this paper focuses on areas identified with the greatest demonstrated potential for new or expanded applications: renewable energy (specifically wind, biomass, and hydroelectric resources), load forecasting, and long-term energy modeling. This study also addresses the evolving context of the Global Earth Observation System of Systems (GEOSS), and the broader framework of integrating satellite remote sensing into energy sector decision-support tools.

Some aspects of the interaction between chemical and dynamic processes relating to the Antarctic ozone hole

Abstract Observational and modeling studies have been conducted to examine the interaction between the chemical and dynamical processes that occur during springtime in the lower stratosphere of the Southern Hemisphere. The temporal evolution of the ozone distribution and the circulation during 1987 is contrasted with that for 1988 as an illustrative example of how dynamical processes and the resulting meteorological conditions modulate the ozone depletion. Concurrently with the observational analysis, an effort was initiated to simulate the ozone depletion during austral spring using a three-dimensional chemical/transport model. The model includes a parameterized representation of the heterogeneous processes thought to be important in this region. The simulation indicates that the inclusion of this additional chemistry, which results in the release of free chlorine and the redistribution of odd nitrogen into reservoir species, reproduces many aspects of the observations. While significant uncertainties and difficulties remain in order to include heterogeneous chemistry in stratospheric models in a self-consistent manner, the preliminary results are encouraging and provide the impetus for improving current models.

Global Modeling of Ozone and Trace Gases

Abstract A three-dimensional, global atmospheric model for simulation of the distribution of ozone and other trace gases Is described. The model extends from the surface to 60 km, Including a comprehensive formulation of the relevant chemistry. Simulated distributions of some of the constituents Important to understanding the stratospheric ozone budget are presented and discussed with respect to degree of agreement with observations. The seasonal evolution of the global distribution of the stratospheric ozone column Is discussed. The interaction between dynamical and chemical processes is illustrated during disturbed winter conditions in the mid-stratosphere.