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  • Author or Editor: Mark R. Schoeberl x
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Mark R. Schoeberl
and
John H. E. Clark

Abstract

A global model of planetary wave propagation in a spherical atmosphere is used to examine the spectrum of free or resonant planetary waves of the solstitial stratosphere. These free modes are located by forcing the model with a weak periodic vertical velocity along the lower boundary and looking for a resonant response in wave amplitude. The modes correspond to the natural traveling oscillations in the earth's atmosphere, of which the 5-day wave is the best known example.

The 15-day wave observed by Madden (1978) and others is found to be such a resonant mode. We find that the strong stratospheric winds cause the 15-day wave to become baroclinic by trapping the wave between the earth's surface and the strong winds at the stratopause. The strong winds effectively reduce the atmospheric damping which greatly reduces the amplitude of barotropic waves with periods >10 days. The computed meridional structure of the 15-day wave is in reasonable agreement with Madden's (1978) observations at extratropical latitudes. Our results indicate that a mode resembling the H⅓ Hough function represents the principal resonant component.

Other resonances at periods longer than 15 days for zonal harmonies 1, 2 and 3 are shown, and these modes are also baroclinic. At very long periods (50–100 days) broad resonant peaks are observed for all three zonal harmonics. These peaks indicate that the structure of stationary planetary waves is very sensitive to changes in the mean zonal wind (frequency changes in this model) as has been noted by other authors.

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Joan E. Rosenfield
,
Mark R. Schoeberl
, and
Marvin A. Geller

Abstract

The global diabatic circulation is computed for the months of January, April, July and October over the altitude region 100 to 0.1 mb using an accurate troposphere-stratosphere radiative transfer model, SBUV and SME ozone data, and NMC temperatures. There is high correlation between the level of wave activity and the local departure of the atmosphere from radiative equilibrium. For example, the summer lower stratosphere is close to radiative equilibrium while the winter is not. We find much greater heating in the upper stratosphere at low latitudes in the summer hemisphere, and roughly a factor of two less heating in the lower stratosphere at low latitudes, than did Murgatroyd and Singleton. An excess in the globally averaged net stratospheric heating from 40 to 50 km is computed for all months, and a deficit from 50 to 60 km is computed during solstice. Roughly a 20% uniform reduction in ozone from 40 to 50 km, or a temperature perturbation with an increase of 5 K at 1 mb, will bring the atmosphere into global radiative equilibrium without significant impact on the diabatic circulation. In the transitional mouths of April and October, the net heating in the fall hemispheres are very similar, while substantial differences exist between the spring hemispheres.

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Mark R. Schoeberl
,
Marvin A. Geller
, and
Susan K. Avery

Abstract

Due to a coding error, the amplitude and phases of stationary planetary waves in the mesosphere were incorrectly calculated by Schoeberl and Geller (1976, 1977). We report the corrected amplitudes and phases here, and note that our findings of strong sensitivity of the wave amplitude to the mean zonal wind profile remain unchanged.

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Richard S. Stolarski
,
Anne R. Douglass
,
Paul A. Newman
,
Steven Pawson
, and
Mark R. Schoeberl

Abstract

The temperature of the stratosphere has decreased over the past several decades. Two causes contribute to that decrease: well-mixed greenhouse gases (GHGs) and ozone-depleting substances (ODSs). This paper addresses the attribution of temperature decreases to these two causes and the implications of that attribution for the future evolution of stratospheric temperature. Time series analysis is applied to simulations of the Goddard Earth Observing System Chemistry–Climate Model (GEOS CCM) to separate the contributions of GHGs from those of ODSs based on their different time-dependent signatures. The analysis indicates that about 60%–70% of the temperature decrease of the past two decades in the upper stratosphere near 1 hPa and in the lower midlatitude stratosphere near 50 hPa resulted from changes attributable to ODSs, primarily through their impact on ozone. As ozone recovers over the next several decades, the temperature should continue to decrease in the middle and upper stratosphere because of GHG increases. The time series of observed temperature in the upper stratosphere is approaching the length needed to separate the effects of ozone-depleting substances from those of greenhouse gases using temperature time series data.

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Kenneth E. Pickering
,
Anne M. Thompson
,
Donna P. McNamara
, and
Mark R. Schoeberl

Abstract

The authors have compared isentropic trajectories computed from meteorological fields from different analysis centers. The analysis was performed for the South Atlantic, where a springtime maximum in tropospheric ozone has sparked considerable interest in the transport meteorology. Using the model of Schoeberl et al., isentropic forward trajectories were computed from an array of points over southern Africa and backward trajectories from an array of points over the South Atlantic. The model was run for an 8-day period in October 1989 with input taken from the twice-daily global gridded data fields from the National Meteorological Center (NMC) and from the European Centre for Medium-Range Weather Forecasts (BCMWF). There were large differences between the trajectories based on the two fields in terms of travel distance, horizontal separation, and vertical separation. Best comparisons for individual trajectories were found in the low-latitude easterlies, and the poorest comparisons were found in the westerlies and in the vicinity of the center of the South Atlantic subtropical anticyclone. Significant differences in wind speeds between the two analyses also led to large trajectory differences.

Trajectories were also computed using once-daily NMC fields. The effect of this degradation of the data was small. Trajectories computed from balanced winds computed from the NMC geopotential height and temperature fields showed the largest differences when compared with the ECMWF trajectories. The balanced wind fields should not be used in trajectory construction in the tropical lower troposphere.

It is difficult to make a definitive recommendation concerning which set of fields should be used in future transport analysts in this region due to the very large trajectory differences found in this analysis and the lack of any independent verification data. Any extensive analysis of transport in this region should be done only in conjunction with considerable additional data collection.

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Hui Su
,
Jonathan H. Jiang
,
Xiaohong Liu
,
Joyce E. Penner
,
William G. Read
,
Steven Massie
,
Mark R. Schoeberl
,
Peter Colarco
,
Nathaniel J. Livesey
, and
Michelle L. Santee

Abstract

Satellite observations are analyzed to examine the correlations between aerosols and the tropical tropopause layer (TTL) temperature and water vapor. This study focuses on two regions, both of which are important pathways for the mass transport from the troposphere to the stratosphere and over which Asian pollution prevails: South and East Asia during boreal summer and the Maritime Continent during boreal winter. Using the upper-tropospheric carbon monoxide measurements from the Aura Microwave Limb Sounder as a proxy of aerosols to classify ice clouds as polluted or clean, the authors find that polluted clouds have a smaller ice effective radius and a higher temperature and specific humidity near the tropopause than clean clouds. The increase in water vapor appears to be related to the increase in temperature, as a result of increased aerosols. Meteorological differences between the clouds cannot explain the differences in temperature and water vapor for the polluted and clean clouds. The authors hypothesize that aerosol semidirect radiative heating and/or changes in cirrus radiative heating, resulting from aerosol microphysical effects on clouds, may contribute to the increased TTL temperature and thus increased water vapor in the polluted clouds.

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Eric J. Jensen
,
Leonhard Pfister
,
David E. Jordan
,
Thaopaul V. Bui
,
Rei Ueyama
,
Hanwant B. Singh
,
Troy D. Thornberry
,
Andrew W. Rollins
,
Ru-Shan Gao
,
David W. Fahey
,
Karen H. Rosenlof
,
James W. Elkins
,
Glenn S. Diskin
,
Joshua P. DiGangi
,
R. Paul Lawson
,
Sarah Woods
,
Elliot L. Atlas
,
Maria A. Navarro Rodriguez
,
Steven C. Wofsy
,
Jasna Pittman
,
Charles G. Bardeen
,
Owen B. Toon
,
Bruce C. Kindel
,
Paul A. Newman
,
Matthew J. McGill
,
Dennis L. Hlavka
,
Leslie R. Lait
,
Mark R. Schoeberl
,
John W. Bergman
,
Henry B. Selkirk
,
M. Joan Alexander
,
Ji-Eun Kim
,
Boon H. Lim
,
Jochen Stutz
, and
Klaus Pfeilsticker

Abstract

The February–March 2014 deployment of the National Aeronautics and Space Administration (NASA) Airborne Tropical Tropopause Experiment (ATTREX) provided unique in situ measurements in the western Pacific tropical tropopause layer (TTL). Six flights were conducted from Guam with the long-range, high-altitude, unmanned Global Hawk aircraft. The ATTREX Global Hawk payload provided measurements of water vapor, meteorological conditions, cloud properties, tracer and chemical radical concentrations, and radiative fluxes. The campaign was partially coincident with the Convective Transport of Active Species in the Tropics (CONTRAST) and the Coordinated Airborne Studies in the Tropics (CAST) airborne campaigns based in Guam using lower-altitude aircraft (see companion articles in this issue). The ATTREX dataset is being used for investigations of TTL cloud, transport, dynamical, and chemical processes, as well as for evaluation and improvement of global-model representations of TTL processes. The ATTREX data are publicly available online (at https://espoarchive.nasa.gov/).

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