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NASA NTRS1985

Far-infrared spectroscopy of the earth's stratosphere

This paper discusses the spectrum of the earth's stratosphere in the far-infrared, from 5 to 250/cm. Many of the trace gases that are important in stratospheric photochemistry have been measured, or are potentially measurable in the far-infrared. The spectral features of these gases are discussed with application to spacecraft measurements. In particular, the suitability of the spectrum for measurements of the HO(x) and ClO(x) families and of O3 are compared for different classes of instruments: Fourier transform spectrometers, filter radiometers, and scanning high-resolution Fabry-Perot instruments. It is found that these types of instruments have complementary capabilities that would best be used in combination in a comprehensive multispecies measurement scheme.

Chance, K. V.↗
NASA NTRS1985

Synopsis of the Fifth Conference on the Meteorology of the Stratosphere and Mesosphere

The papers presented at the Fifth Conference on the Meteorology of the Stratosphere and Mesosphere held on April 23-26, 1985, are reviewed. The observational aspects of large-scale circulation, such as summer and winter circulation in the Southern Hemisphere, and analysis schemes, like the multivariate statistical analysis scheme, are discussed. The topics of numerical simulations of the general circulation and sudden-warming are examined. Papers concerning processes of O3, NO2, H2, and HNO3 are described. Research on large-scale mixing processes in the stratosphere is presented. The topic of equatorial dynamics and stability is analyzed. Papers focusing on the effect of gravity waves on the general circulation are studied.

Schoeberl, M. R.↗
NASA NTRS1986

The solar and dynamically induced oscillations in the stratosphere

The temporal and spatial features of stratospheric fluctuations are analyzed using 2.5 years of ozone and temperature data from the Nimbus 7 solar backscattered ultraviolet and the SAMS experiments. It is observed that the oscillations are dynamically induced perturbations in the winter hemisphere and the 27-day modulation of the solar UV radiation. The fluctuations in the ozone and temperature are compared with solar activity. The effects of solar and temperature perturbations on stratospheric ozone are examined; it is shown that the dynamically induced oscillations are global and independent of solar activity. The seasonal, latitudinal, and altitudinal variations of the regression factors and their influence on the ozone are studied. Multiple regression and cross-spectral analyses of ozone, temperature, and solar flux data reveal that the ozone mixing ratio is more sensitive to changes in temperature than changes in solar activity.

Chandra, S.↗
NASA NTRS1986

In situ stratospheric ozone measurements by long path UV absorption - Developments and interpretation

A high-sensitivity, in situ UV absorption ozone sensor has been developed for use in the stratosphere. The instrument couples 254-nm radiation from a low-pressure mercury discharge lamp into a 40-pass White cell to attain a high-sensitivity ozone absorption measurement. Preflight/postflight laboratory tests utilizing an ozone source coupled to a laboratory UV ozone photometer in a fast-flow system as well as in-flight diagnostics verify the successful operation of the instrument. Evidence is presented to verify that in situ UV absorption ozone photometers can measure stratospheric ozone with better than 3 percent precision and 5 percent accuracy, provided proper attention is given to both the thermal field surrounding the gondola and the ambient pressure measurements. Ozone data are compared with modeled profiles in the 28- to 40-km region. An assessment of the disagreement between observations and modeled profiles is given along with suggestions for future experiments designed to constrain photochemical models.

Weinstock, E. M.↗
NASA NTRS1986

Observations of the diurnal variation of nitrogen dioxide in the stratosphere

Observations of NO2 from the limb infrared monitor of the stratosphere (LIMS) experiment in high-latitude summer are presented. Appropriate selection of latitude and days during the month of May yields NO2 observations obtained during the afternoon and evening at solar zenith angles ranging from about 35-110 deg. These data show that the NO2 abundances in the stratosphere become strongly dependent on the solar zenith angle for angles exceeding about 80 deg. Model calculations and other observations suggest that from about 80-95 deg this dependence probably reflects variations in the propagation of the visible radiation that photodissociates NO2. The data obtained at zenith angles greater than about 95 deg provide clear evidence for the night decay of NO2 to form N2O5, and the observed decay rate is shown to be consistent with present theory.

Solomon, S.↗
NASA NTRS1986

SAGE observations of stratospheric nitrogen dioxide

The global distribution of nitrogen dioxide in the middle to upper stratosphere (25-45 km altitude) for the period February 1979 to November 1981 has been determined from observations of attenuated solar radiation in the visible region 0.385-0.45 micron by the Stratospheric Aerosol and Gas Experiment (SAGE) satellite instrument. The SAGE-derived NO2 vertical profiles compare well with observations by balloon- and aircraft-borne sensors. The global SAGE NO2 distributions generally show a maximum in mixing ratio of 8 parts per billion by volume at about 35 km altitude near the equatorial latitudes at local sunset. The location of the mixing ratio peak moves synchronously with the overhead sun for the four different seasons. High-latitude NO2 column content shows strong seasonal variation, with a maximum in local summer and a minimum in local winter. Selected data at high-latitude winter seasons are presented, suggesting that the large variation shown could be explained by the coupling of both dynamics and photochemistry of the NO(x) species. Finally, profiles of the ratio of sunset to sunrise NO2 mixing ratios, peaking at about a factor of two at 30 km, are shown.

Chu, W. P.↗
NASA NTRS1986

Comparison of stratospheric air parcel trajectories calculated from SSU and LIMS satellite data

Midstratospheric trajectories for February and March 1979 are calculated using geopotential analyses derived from limb infrared monitor of the stratosphere data. These trajectories are compared with the corresponding results using stratospheric sounding unit data. The trajectories are quasi-isentropic in that a radiation scheme is used to simply cross-isentrope flow. The results show that in disturbed conditions, quantitative agreement the trajectories, that is, within 25 great circle degrees (GCD) (one GCD about 110 km) may be valid for only 3 or 4 days, whereas during quiescent periods, quantitative agreement may last up to 10 days. By comparing trajectories calculated with different data some insight can be gained as to errors due to vertical resolution and horizontal resolution (due to infrequent sampling) in the analyzed geopotential height fields. For the disturbed trajectories described in this paper the horizontal resolution of the data was more important than vertical resolution; however, for the quiescent trajectories, which could be calculated accurately for a longer duration because of the absence of appreciable transients, the vertical resolution of the data was found to be more important than the horizontal resolution. It is speculated that these characteristics are also applicable to trajectories calculated during disturbed and quiescent periods in general. A review of some recently published trajectories shows that the qualitative conclusions of such works remains unaffected when the calculations are repeated using different data.

Austin, J.↗
NASA NTRS1986

Detection of stratospheric HNO3 and NO2 response to short-term solar ultraviolet variability

It is pointed out that variations in the solar ultraviolet irradiance with a period equal to or approximately one-half of the rotation period of the sun are currently observed by satellite monitoring. Information regarding the response of stratospheric species to solar ultraviolet variability is indispensable for an understanding of the photochemical behavior of the middle atmosphere. Relations are considered between LIMS (limb infrared monitor of the stratosphere) measurements of HNO3 and NO2, and the SBUV (solar backscatter ultraviolet) measurements of short-term variations in 205-nm radiation. It is found that the response of HNO3 is much stronger than, but in the opposite sense to the ozone response, while the NO2 response is in the opposite sense to the HNO3 response. Model calculations predict large variations in HNO3 over the 11-yr solar cycle.

Keating, G. M.↗
NASA NTRS1985

Effects of stratospheric lapse rate on numerically simulated thunderstorm cloud top structure

The study of overshooting midlatitude severe thunderstorm tops has led to the detection of some intriguing patterns. This paper provides a summary of an investigation of the effects of stratospheric stability on thunderstorm cloud top structure, taking into account the utilization of a fully three-dimensional (3D) anelastic model discussed by Schlesinger (1975, 1978, 1984). The layout of model experiments is discussed, giving attention to initial environmental soundings, and initial forcing. The time variation of the vertical velocity extreme is examined, and a description of the mature storm structure is presented. Constant-altitude plane views throughout storm depth are considered along with cloud top height fields. With the stratospheric lapse, the warm region is small and breaks down into separate spots with secondary cold spots downshear of them.

Schlesinger, R. E.↗
NASA NTRS1986

Features of stratospheric aerosol lidar observations at Mauna Loa, 1974 - 1985

Lidar observations of the stratospheric aerosol over Mauna Loa were begun in the fall of 1974 and have continued to the present. An analysis of these observations has yielded interesting features of the stratospheric aerosol profile that change according to perturbed (from volcanic activity) and quiescent conditions. In the Mauna Loa lidar record there are two major perturbations that are contrasted, Fuego and El Chichon. The variations in relative aerosol cloud thickness, altitude of the maximum concentration and nonsymmetry are compared for the quiescent and perturbed time periods. Also, a climatology of annual average aerosol profiles is descrbied. A brief description will be given of procedures used to validate the lidar optical thickness information.

Delusi, J. J.↗
NASA NTRS1986

El Chichon aerosols in the stratosphere: Analyses of lidar data and calculations of radiation budget

Lidar observation at Fukuoka has provided over four years the data of ElChichon aerosols in the stratosphere. Analyses of the data show that an enormous amount of volcanic aerosols has continuously decreased since the beginning of 1983 with significant fluctuations. These fluctuations reveal themselves as a seasonal variation of aerosol content with a maximum in winter-spring and a minimum in summer. The vertical structure of the aerosol layer also shows the seasonal variation. Although the height of a peak around 18 km in the vertical profile of scattering ratio show littel variation, the higher second peak appears frequently from late fall and the lower third peak from late winter to late spring just as two and more tropopauses appear in these periods. The mechanism which causes the seasonal variation will be discussed in terms of the transport by the atmoshperic circulation and the removal through the tropopause gap. Radiation budget in the atmosphere was calculated taking into account the large amount of aerosols observed in the early stages of the El Chichon event. The heating rate of the atmosphere is more than 1 K in the bottom region of the stratosphere even in the nighttime. The possible effect of the volcanic aerosols on the other geophysical phenomena will be discussed using the calculated values of the heating rate.

Fujiwara, M.↗
NASA NTRS1986

The application of lidar to stratospheric aerosol studies

The global climatology and understanding of stratospheric aerosols evolving primarily from lidar and satellite measurements is presented. The importance of validation of these remotely sensed data with in situ measurements is also discussed. The advantage of lidar for providing high vertical and horizontal resolution and its independence from a remote source for measurement will become evident with examples of long term lidar data sets at fixed sites and the use of lidar on airborne platforms. Volcanic impacts of the last 20 years are described with emphasis on the last 8 years where satellite data are available. With satellite and high resolution lidar measurements, an understanding of the global circulation of volcanic material is attempted along with the temporal change of aerosol physical parameters and the stratospheric cleansing or decay times associated with these eruptions.

Mccormick, M. P.↗
NASA NTRS1986

The GSFC gound-based lidar for the measurement of stratospheric ozone

Concern has risen over the last decade concerning the release of gases into the atmosphere which when photolyzed in the stratosphere can catalyze the destruction of ozone. Although the expected change is only on the order of 5%, significant changes in the vertical profile are anticipated. Predictions at 40 km run as high as a 60% change in the next 50 to 100 years. Because of the importance of ozone in the thermal budget of the atmosphere, such a change will have a direct impact on the earth's climate. Long term monitoring of stratospheric ozone is required to validate the predictions and Differential Absorption Lidar is particularly well suited to this measurement. GSFC is currently constructing a mobile lidar system based on a high powered XeCl excimer laser. The system is expected to be operating by fall 1986 and a campaign to compare the lidar results with a series of ROCOZ flights is planned.

Mcgee, T. J.↗
NASA NTRS1986

A study of gravity-wave spectra in the troposphere and stratosphere at 5-min to 5-day periods with the Poker Flat MST radar

An analysis of frequency spectra at periods of about 5 days to 5 min from two 20-day sets of velocity measurements in the stratosphere and troposphere region obtained with the Poker Flat mesosphere-stratosphere-troposphere (MST) radar during January and June, 1984 is presented. A technique based on median filtering and averaged order statistics for automatic editing, smoothing and spectral analysis of velocity time series contaminated with spurious data points or outliers is outlined. The validity of this technique and its effects on the inferred spectral index was tested through simulation. Spectra obtained with this technique are discussed. The measured spectral indices show variability with season and height, especially across the tropopause. The discussion briefly outlines the need for obtaining better climatologies of velocity spectra and for the refinements of the existing theories to explain their behavior.

Bemra, R. S.↗
NASA NTRS1986

The area of the stratospheric polar vortex as a diagnostic for tracer transport on an isentropic surface

Daily isentropic distributions of Ertel potential vorticity, O3, water vapor, and HNO3 at the 850-K level of the Northern-Hemisphere stratosphere are determined on the basis of data from the Limb IR Monitor of the Stratosphere (Gille and Russell, 1984) on Nimbus 7 for the period October 25, 1978-April 2, 1979. The results are presented in graphs and maps and analyzed in detail. The surf-zone main-vortex structure identified by McIntyre and Palmer (1983 and 1984) is observed, superimposed on the seasonal patterns, with expansion of the surf zone and shrinking of the main vortex as the winter progresses. Irreversible mixing is found to be the dominant mechanism controlling the redistribution of all measured species except HNO3.

Butchart, N.↗
NASA NTRS1986

On the radiative balance of the stratosphere

The zonally averaged radiative balance of the stratosphere based on the measured temperature structure and gas concentrations available from the LIMS instrument is examined in detail. These data are extant for seven months (November 1978 to May 1979). The contribution to the net radiative balance due to the individual components of solar heating and longwave cooling is discussed. These components are further broken down by individual gas constituent to understand the role each gas plays in determining the total radiative heating/cooling. The deficiencies of employing a latitudinally and temporally independent Newtonian damping coefficient are also explored. In particular, the Newtonian damping time is shown to vary by a factor of two in both latitude and season. Net zonally averaged stratospheric radiative heating for the seven months of LIMS data are presented. These net heating rates are important in determining the role of advective transport of chemical constituents. An important feature that appears in the derived radiative heating is the existence of a region of net radiative cooling near the equatorial stratopause.

Kiehl, J. T.↗
NASA NTRS1986

Characteristics of Arctic polar stratospheric clouds and as measured by airborne lidar

Airborne lidar measurements of backscattering from polar stratospheric clouds (PSCs) obtained in January 1984 are examined. The flights, principal characteristics of the lidar system, and the meteorological conditions during the flights are described. The characteristics and conditions for the formation of PSCs and the optical characteristics of the clouds are discussed. The properties of the North Polar vortex and El Chichon stratospheric aerosol are studied. Variations in the aerosol optical properties with temperature and water vapor concentrations are analyzed and modeled using a model based on volcanic aerosols and water vapor concentration. The modeled and experimental backscattering-temperature relationship are compared and good correlation is observed at pressure levels of 100 and 70 mb.

Kent, G. S.↗
NASA NTRS1987

Statistical analysis of total ozone and stratospheric Umkehr data for trends and solar cycle relationship

Dobson total ozone data from 1970-1984 and stratospheric Umkehr profile ozone data from 1970-1981 are analyzed. The relationship between ozone and long-term solar cycle activity is examined using 10.7 cm solar flux data. From the Dobson data it is estimated that the overall global trend in total ozone is -0.26 + or -0.92 percent per decade, which indicates no significant overall trend; and for the total ozone-solar flux relationship there is a 1.18 + or - 0.66 percent change in total ozone from solar cycle minimum to maximum that reveals a positive relationship. Analysis of the Umkehr data reveals a negative trend of -0.30 + or - 0.17 percent per year in the layers 7 snd 8. The relationship between Umkehr data and solar flux in layers 6 and 7 is 2.57 + or - 1.25 percent and 3.40 + or - 2.16 percent change from solar cycle minimum to maximum; however, no significant relationship is detected in the higher layers 8 and 9. These estimates are compared with theoretical model calculations. It is noted that the estimated effects of solar cycle activity on total ozone and stratospheric ozone agree with calculations of photochemical models.

Reinsel, Gregory C.↗