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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The distribution and annual cycle of ozone in the upper stratosphere

Study of the global distribution of upper stratospheric ozone derived from backscatter ultraviolet (BUV/SBUV) instruments on the Nimbus 4 and 7 satellites reveals the following characteristics for the period June 1970 May 1972 plus portions of 1978 and 1979. At pressures less than 5 mbar a local midlatitude maximum in the ozone mixing ratio develops in autumn and persists through the winter season in both hemispheres. However, by a pressure of 10 mbar the seasonal trend has reversed, with midlatitude summer values exceeding those in winter. The largest ozone mixing ratios in a global sense occur at tropical latitudes between pressures of 7 and 9 mbar. The general character of this pattern repeats from year to year, although differences in detail exist, especially in winter. This interannual variability in ozone increases the difficulty in extracting small long-term trends from the available data base. The overall seasonal pattern revealed by the measurements is in accord with photochemical model predictions which include the annual variation in temperature and solar illumination.

Frederick, J. E.↗
NASA NTRS1983

On the role of the seasonal cycle

The definition of the seasonal cycle as the projection of an atmospheric time series onto a suitably defined subset of orthogonal basis functions guarantees that any atmospheric covariance may be expressed as the sum of a seasonal cycle part and a transient part (where transient refers to departures from the seasonal cycle rather than the time mean). Results are presented for the seasonal cycle contribution to the zonally averaged fluxes of momentum and heat, and for the zonally averaged height variance, in data for: the winter season, the winter season with the Fourier basis set appropriate for the seven-year time series, and the seven-year mean. The Fourier basis set calculation indicates that the interannual variability of the momentum flux is dominated by the interactions between the seasonal cycle and the meteorologically low frequency flow.

Straus, D. M.↗
NASA NTRS1985

North American vegetation patterns observed with the NOAA-7 advanced very high resolution radiometer

Spectral vegetation index measurements derived from remotely sensed observations show great promise as a means to improve knowledge of land vegetation patterns. The daily, global observations acquired by the advanced very high resolution radiometer, a sensor on the current series of U.S. National Oceanic and Atmospheric Administration meteorological satellites, may be particularly well suited for global studies of vegetation. Preliminary results from analysis of North American observations, extending from April to November 1982, show that the vegetation index patterns observed correspond to the known seasonality of North American natural and cultivated vegetation. Integration of the observations over the growing season produced measurements that are related to net primary productivity patterns of the major North American natural vegetation formations. Regions of intense cultivation were observed as anomalous areas in the integrated growing season measurements. Significant information on seasonality, annual extent and interannual variability of vegetation photosynthetic activity at continental and global scales can be derived from these satellite observations.

Goward, S. N.↗
NASA NTRS1984

Midwinter Disturbances in the Middle Atmosphere

The Middle Atmosphere is coupled to the troposphere during winter because planetary scale waves can propagate upwards if the prevailing winds are from the west. It is during this time of the year that the well-known midwinter disturbances are observed which ultimately affect the whole of the Middle Atmosphere. The mechanism of these disturbances is not completely understood. The large-scale circulation features up to the upper mesosphere are investigated to demonstrate the synoptic-scale behavior of the midwinter disturbances. Ground-based and satellite observations are combined. The interannual variability of the disturbances is discussed briefly. It is shown that the QBO (Quasi Biennial Oscillation) of the equatorial stratosphere appears to modulate the planetary waves during the northern winters, in the troposphere as well as in the Middle Atmosphere.

Labitzke, K.↗
NASA NTRS1983

Climatological studies of cloudiness

The influence of subresolution clouds on estimates of synoptic-scale averages and the effect of synoptic-scale clouds on estimates of planetary scale interannual variability are discussed. It is shown that climatic noise is strongly dependent on the season and geographic region, so that the largest anomaly is not always the most significant. The role of advection in determining the time-scales and degrees of freedom of synoptic scale cloudiness is empirically demonstrated and described in terms of a simple model of stochastic 'cloud patches'.

Cahalan, R. F.↗
NASA NTRS1985

Interim Reference Ozone Models for the Middle Atmosphere

A set of models was generated based on six satellite experiments of the monthly latitudinal variations in total column ozone and the vertical structure of ozone from 20 mb to 0.003 mb. Generally, interannual variability in monthly zonal means is only a few percent. Comparisons of measurements using various techniques to measure global ozone reveal very good agreement between the techniques. Agreement between individual satellite experiments and the reference model of monthly zonal means is generally within 10% below altitudes of 0.4 mb. This has allowed the first global model of ozone measurements to be constructed from multiple sets of satellite measurements. The ozone measurements based on the satellite data are in excellent agreement with previous midlatitude mean annual model based on rocket and balloon data. Also, models are provided of the relation between total ozone and vertical structure.

Keating, G. M.↗
NASA NTRS1985

Middle atmosphere general circulation statistics

With the increased availability of remote sensing data for the middle atmosphere from satellites, more analyses of the middle atmosphere circulation are being published. Some of these are process studies for limited periods, and some are statistical analyses of middle atmosphere general circulation statistics. Results from the latter class of studies will be reviewed. These include analysis of the zonally averaged middle atmosphere structure, temperature, and zonal winds; analysis of planetary wave structures, analysis of heat and momentum fluxes; and analysis of Eliassen-and-Palm flux vectors and flux divergences. Emphasis is on the annual march of these quantities; Northern and Southern Hemisphere asymmetries; and interannual variability in these statistics. Statistics involving the global ozone distribution and transports of ozone are also discussed.

Geller, M. A.↗
NASA NTRS1985

Monthly mean distribution of ozone and temperature

Global monthly mean charts for both hemispheres are given for four mid-season months, and for the pressure levels 30, 10, 1, and 0.1 mbar for temperature and 0.4 mbar for ozone. Charts of total ozone are provided separately. This set of charts shows clearly the very close coupling between the temperature and ozone distributions and demonstrates the influence of the large-scale planetary waves which give rise to very large longitudinal variations. The regular and interannual variability of temperature and ozone are discussed.

Labitzke, K.↗
NASA NTRS1986

El Nino and outgoing longwave radiation - Observations from Nimbus-7 ERB

Nimbus-7 longwave radiation data are analyzed with respect to temporal and spatial changes in the anomalies induced by the El Nino event of 1982-1983. The components and functions of the earth radiation budget (ERB) instruments, which record satellite-altitude irradiances, are described. Local-noon analyses of outgoing longwave radiation (OLR) are presented; interannual variability is observed. El Nino-induced perturbations in the planetary-scale fields which affect OLR are studied. The onset, intensification, expansion, and decay of the OLR associated with El Nino are examined. A comparison of the ERS data with a three month average OLR anomaly map reveals that the ERS data have sufficient accuracy and stability with which to observe OLR anomalies induced by El Nino.

Ardanuy, P. E.↗
NASA NTRS1985

Dynamical processes

The techniques used to observe the middle atmosphere; the zonally-averaged and eddy structure of the middle atmosphere; seasonal variations and interannual variability; theoretical understanding of the middle atmospheric circulation are discussed. Recent satellite-based observational studies of stratospheric transport process, as revealed by the behavior of constituents and of potential vorticity (a dynamical tracer) are reviewed. The theory of global transport and its representation in transport models is discussed.

Plumb, R. A.↗
NASA NTRS1986

A simple model for the interaction of planetary and synoptic-scale waves in the troposphere

The time-mean circulation of the troposphere during the Northern hemisphere winter is dominated by planetary-scale stationary waves superposed on longitudinal-mean westerly flow. The movement and generation of weather-making, synoptic-scale transient waves are controlled by this large-scale circulation. The interannual variablity of planetary scale waves determines the severity of the winter season over broad geographic regions through such factors as frequency of storms, precipitation and temperature. A conceptual model that incorporates these feedbacks between the two scales is developed and guides the formulation of the quantitative low-order model which retains a few basic physical processes and wave components. In the low-order model the fluxes of sensible heat and momentum and latent heat release by transient eddies are parameterized in terms of the evolving large-scale circulation. Radiative forcing and damping, planetary-scale variations in moisture and topography and Ekman dissipation are also included. Testing of this model is in progress. The results will help interpret experiments from sophisticated general-circulation models and ascertain the need for satellite observations of precipitation.

Branscome, Lee E.↗
NASA NTRS1987

Investigating the role of the land surface in explaining the interannual variation of the net radiation balance over the Western Sahara and sub-Sahara

The status of the data sets is discussed. Progress was made in both data analysis and modeling areas. The atmospheric and land surface contributions to the net radiation budget over the Sahara-Sahel region is being decoupled. The interannual variability of these two processes was investigated and this variability related to seasonal rainfall fluctuations. A modified Barnes objective analysis scheme was developed which uses an eliptic scan pattern and a 3-pass iteration of the difference fields.

Smith, Eric A.↗
NASA NTRS1986

Some observations on the role of planetary waves in determining the spring time ozone distribution in the Antarctic

Ozone measurements from 1970 to 1984 from the Nimbus 4 backscattered ultraviolet and the Nimbus 7 solar backscattered ultraviolet spectrometers show significant decrease in total ozone only after 1979. The downward trend is most apparent in October south of 70 deg S in the longitude zone 0 to 30 deg W where planetary wave activity is weak. Outside this longitude region, the trend in total ozone is much smaller due to strong interannual variability of wave activity. This paper gives a phenomenological description of ozone depletion in the Antarctic region based on vertical advection and transient planetary waves.

Chandra, S.↗
NASA NTRS1986

Computations of atmospheric angular momentum, with emphasis on the merit period

Three-dimensional wind and pressure fields used to calculate effective angular momentum functions (EAMFs) for earth rotation/polar motion are produced by a complex 3-step system at the U.S. National Meteorological Center. The resulting series of functions have errors which can be estimated by comparisons with similar series produced by the European Center for Medium Range Weather Forecasts. For the axial wind component, related to length of day (lod) changes, the small differences between the two series of atmospheric angular momentum (AAM) are confined to the tropics and the higher latitudes of the Southern Hemisphere. In addition, differences between the seasonal components of the AAM series and those of lod are found to be significantly reduced by including the entire stratosphere's momentum. Comparisons of the EAMFs for 8 calendar years indicate substantial interannual variability exists in the annual amplitudes of these forcing terms. In particular, the axial AAM showed quite different behavior from normal in 1983 and 1984, the years of the MERIT campaign. These two years showed very high and low annual amplitudes for AAM, respectively, which can be attributed to the effect of the tropical Pacific sea surface warming (El Nino) and its aftermath.

Salstein, David A.↗
NASA NTRS1987

The stratosphere - Climatologies of the radiative heating and cooling rates and the diabatically diagnosed net circulation fields

Stratospheric solar, IR, and net radiative heating are calculated on a monthly basis using solar and IR radiative codes and satellite derived distributions of ozone, water vapor, and temperature. Divergence-free, zonally averaged, advective fields are diagnosed using the calculated diabatic heating; associated stream functions are derived. The stratospheric transport of inert tracers is studied. Analysis of the diagnosed advective fields reveal that: (1) entry into the mid- to upper stratosphere of tropospheric air is mainly from altitude regions of + or - 10 deg at the equatorial tropopause; (2) at latitudes poleward of + or - 15 deg, tracers transported from the troposphere into the stratosphere are transported toward the pole and then downward and out of the stratosphere; and (3) the presence of net cooling cells in the lower stratospheric polar regions is important. The interannual variability of the diabatic circulation is estimated using heating and advection fields derived from LIMS data.

Callis, Linwood B.↗
NASA NTRS1987

Classification, seasonality and persistence of low-frequency atmospheric circulation patterns

The seasonality and persistence of the major modes of interannual variability in the low-frequency atmospheric circulation were studied using orthogonally rotated principle component analysis (RPCA) of Northern Hemisphere 1-month mean 700 mb heights. The twice-daily data for the 1950-1984 period were used. Winter results are similar to those of other recent RPCA and teleconnection studies. The strongest summer pattern is the North Atlantic Oscillation, which is also the strongest winter pattern; it systematically contracts northward in summer and expands southward in winter, being the only pattern found for every month of the year. The robustness of the RPCA results was examined through consistency with results of other studies and of adjacent month solutions within this study, as well as by replicating the results using 3-month and 10-day means of 700-mb height. It is concluded that the RPCA method provides a physically meaningful and statistically stable product with the simplicity of teleconnection patterns but with superior pattern choice and depiction.

Barnston, Anthony G.↗
NASA NTRS1987

Dynamical factors affecting ozone mixing ratios in the Antarctic lower stratosphere

An account is given of the climatology and interannual variability of dynamical quantities and ozone mixing ratios during the Southern Hemisphere spring for 1979-1984. The seasonal variation in temperature in the lower stratosphere is repeatable; a steep decrease in zonal mean ozone mixing ratios is observed around 60 deg S toward the South Pole in September which, with time, becomes shallower in association with minor warmings and a final warming. Climatological synoptic charts in the lower stratosphere show the circumpolar circulation in the geopotential height field and the prominence of planetary wave 1 in the temperature and ozone fields. When wave activity is strong, there are weaker westeries, higher temperatures, and higher ozone mixing ratios at high latitudes.

Shiotani, Masato↗
NASA NTRS1987

MECA Conference on Mars: The Evolution of Its Climate and Atmosphere, Washington, DC, July 18, 19, 1986, Proceedings

The geological, atmospheric, and climatic history of Mars is explored in reviews and reports of recent observational and interpretive investigations. Topics addressed include evidence for a warm wet climate on early Mars, volatiles on earth and on Mars, CO2 adsorption on palagonite and its implications for Martian regolith partitioning, and the effect of spatial resolution on interpretations of Martian subsurface volatiles. Consideration is given to high-resolution observations of rampart craters, ring furrows in highland terrains, the interannual variability of the south polar cap, telescopic observations of the north polar cap and circumpolar clouds, and dynamical modeling of a planetary-wave polar-warming mechanism.

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