Showing papers on "Tropopause published in 1982"

On the Height of the Tropopause and the Static Stability of the Troposphere

Abstract: Speculative arguments are, presented that describe how radiative and dynamical constraints conspire to determine the height of the tropopause and the tropospheric static stability in midlatitudes and in the tropics. The arguments suggest an explanation for the observation that climatological isentropic slopes in midlatitudes are close to the critical slope required for baroclinic instability in a two-layer model.

Radio science with voyager 2 at saturn: atmosphere and ionosphere and the masses of mimas, tethys, and iapetus.

Abstract: Results of Voyager 2 radio occultation studies of the atmosphere and ionosphere of Saturn and radio tracking determinations of the masses of Mimas, Tethys, and Iapetus are presented. Measurement of received signal frequency for signals of 3.6 and 13 cm wavelength during Voyager occultation immersion at 36.5 deg N and emmersion at 31 deg S reveal atmospheric temperatures of 143 K at the 1.2 bar level, falling to 82 K at the tropopause at about 70 mbar and rising to about 140 K at the tropopause at about 70 mbar and rising to about 140 K at the 1-mbar pressure level in the stratosphere. Peak electron concentrations of 17,000 and 6400/cu cm are found in the predawn and late afternoon locations, respectively, with topside plasma scale heights of 260-1100 km and 1000 km. Direct measurements of the masses of Tethys and Iapetus yield values of 7.55 and 18.8 x 10 to the 20th kg respectively, and an implied mass of 0.455 x 10 to the 20 kg for Mimas. Results suggest that satellite density tends to decrease with increasing orbital radius, and imply that the intermediate-sized satellites of Saturn may represent objects with differing relative amounts of water, ammonia and methane ices. The apparent low density of Iapetus may then be explained by a large hydrocarbon content.

Transport of water through the tropical tropopause

Abstract: Total water was measured in the high troposphere and low stratosphere over Panama during ten aircraft flights. The results show that convective storms provide the means of transporting water into the stratosphere. From a consideration of the anvil heights over different areas of the tropical zone, it follows that a negative gradient of water vapor mixing ratio with altitude must exist over most of the lower stratosphere.

Vertical distribution of deuterium in atmospheric water vapour

Abstract: Available experimental data on the vertical deuterium distribution in atmospheric water vapour show a steep decrease of deuterium with altitude in the lower troposphere. Condensation removal of water alone does not correctly reproduce the isotopic evolution of ascending air masses and the steep deuterium profiles observed. Therefore, a multibox cloud model is proposed to explain the experimental data. In this one-dimensional model a complete isotope exchange between the falling raindrops and the vapour and cloud water at various atmospheric levels is proposed. The observed deuterium increase near the tropopause is proposed to be at least partly due to downward mixing of isotopically heavy water vapour produced by methane decomposition in the upper atmosphere. DOI: 10.1111/j.2153-3490.1982.tb01800.x

Gravity‐wave generation by thunderstorms observed with a vertically‐pointing 430 MHz radar

Abstract: During September of 1979, the Arecibo Observatory 430 MHz Doppler radar was used to study the upper troposphere and lower stratosphere during thunderstorm activity in the afternoon hours. It was found that when the clouds developed sufficiently in the vertical direction to reach the height of the tropopause, gravity-wave oscillations in the vertical velocity above the tropopause would develop. The amplitude was 2 m/s, and the period was close to 6 min.

The transport of heat, water vapor and particulate material to the south polar plateau

Abstract: A systematic series of aerosol observations was begun at South Pole in 1974. These observations were coordinated with surface meteorological observations and soundings. Concurrent ozone observations began shortly after, and water vapor measurements, using an electrolytic cell, were begun in 1976. During 1977 and 1978 airborne aerosol and meteorological observations from an instrumented LC 130R were used to construct vertical profiles over the polar plateau, the Ross Sea, and Ross Ice Shelf, and to make constant altitude transects from the periphery to the interior of the continent. Analysis of the airborne aerosol observation shows that the most moist and aerosol-laden air over the interior of the continent is found in, and just above, the inversion, a few hundred meters above the surface. Aerosol concentrations decrease above this layer, to and through the tropopause. The surface aerosol, water vapor, and temperature record has been stratified by 20° sectors of wind direction occurring concurrent with the observations. This analysis supports a simple meteorological model of transport to the South Polar Plateau. When the polar high is centered over the center of the Antarctic ice mass, the normal condition katabatically reinforced weak gradient wind occurs, and South Pole receives surface winds from the grid northeast. When this high is centered on the Greenwich meridian, warm, moist, aerosol-laden air can flow along a short path from the Weddell Sea to the pole. When this high is centered along the dateline, the air has a long trajectory over ice and arrives at the pole along 090° depleted of heat, water vapor, and aerosol. Combining the surface and airborne aerosol observations for analysis indicates that the preferred levels for transport of particulate matter to the pole occurred in the lower troposphere.

An Objective Method for the Determination of Tropopause Height from VHF Radar Observations

Abstract: The relationship between the magnitude of backscattered power observed at vertical incidence by a VHF radar is related to atmospheric stability in accordance with the recently developed Fresnel scattering model. Utilizing the Fresnel scattering model, tropopause height can be determined objectively from the observed vertical profile of backscattered power. The method is demonstrated with observations from the Sunset VHF radar. A preliminary error analysis shows that the technique is potentially capable of determining tropopause heights within about 300 m of the tropopause heights determined from radiosonde soundings.

Baroclinic Waves and Frontogenesis in a Non-Uniform Potential Vorticity Semi-Geostrophic Model.

Abstract: A three-dimensional semi-geostrophic model is used to study the nonlinear development of baroclinic waves on a zonal jet in a model atmosphere with a large change in potential vorticity in the region of the tropopause. The surface frontogenesis proceeds much as in the previous studies in which the tropopause was represented by a lid. However, the upper air development is much more realistic. In particular, there is a locally indirect forcing of the vertical circulation in the region of the upper air front which is easily understood in the present content.

A Technique for Determining the Temperature Profile from VHF Radar Observations.

Abstract: A technique is presented which enables an estimate of the atmospheric temperature profile from atmospheric stability measurements made by vertically looking VHF radars. The determination of the tropopause height leads to a most probable temperature at the tropopause for a given station and season. Measurements of atmospheric stability permit the temperature profile to be constructed from the tropopause upward. The profile can be continued to the surface simply by assuming a uniform lapse rate between the surface and the tropopause. We illustrate the technique with observations from the Sunset VHF radar located near Boulder, Colorado.

Orbiting lidar simulations. 2: Density, temperature, aerosol, and cloud measurements by a wavelength-combining technique.

Abstract: A technique is described for combining several wavelength backscatter measurements to yield profiles of molecular density and temperature plus aerosol and cloud backscatter with associated error-bar profiles. Error sources include signal, transmission, calibration, conventional density, lidar density normalization, temperature or pressure estimation at a reference height, and backscatter wavelength-dependence estimation. Strong particulate contamination limits the technique to the cloud-free upper troposphere and above. Error bars automatically returned as part of the measurement show when such contamination occurs. Relative density (temperature) profiles have rms errors of 0.5–2% (1.2–2.5 K) in the nonvolcanic stratosphere and upper troposphere. The density profiles significantly improve aerosol retrievals. The fine vertical resolution of the temperature profiles would permit defining the tropopause to ∼0.5 km and higher wave structures to 1 or 2 km.

Altitude variations in stratospheric aerosols of a tropical region

Abstract: To investigate the possibility that significant amounts of tropical tropospheric air may be convectively introduced into the stratosphere, aerosol samplings over Panama were made at various altitudes using a wire impactor collector. The percentage of particle sizes less than the mean mode decreases with height above the tropopause, suggesting depletion of small particles, possibly due to coagulation. Larger aerosols (greater than 0.3 micron in diam.) are more abundant farther above the tropopause, indicating growth, mainly by condensation. The total particle concentration decreases with increasing height above the tropopause, and also with increasing temperature. Aerosols containing smaller-size particles are thus found closer to the tropopause, and larger-size, more-evolved aerosols occur at higher altitudes. These data indicate that convective activity at the Intertropical Convergence Zone may be a source mechanism for stratospheric aerosols.

Stratospheric aerosol inferred from electrical conductivity during a volcanically quiescent period

Abstract: Profiles of electrical conductivity in the troposphere and stratosphere were measured by balloon-borne conductivity sondes at Garmisch-Partenkirchen, West Germany, from January to May, 1980, when volcanic activity was low. The aerosol concentration has been deduced from the relative decrease of conductivity from surrounding values by assuming the effective attachment coefficient of ions to aerosols. A prominent decrease of the conductivity near the tropopause is usually observed indicating high concentrations of Aitken particles (500–1000 cm−3). A decrease of conductivity, well above the tropopause, is sometimes observed, probably due to the transport of tropospheric Aitken particles with high concentration (200–400 cm−3) into the stratosphere.

Further Discussion of “Questions Concerning the Possible Influence of Anthropogenic CO2 on Atmospheric Temperature”

Abstract: The calculation by Newell and Dopplick (1979) of atmospheric temperature change due to CO2 doubling yielded such a small increase because the analysis was incomplete. In fact, the method of calculation is itself of questionable utility because it is so sensitive to parameter errors. In simple climate models the heat balance at the tropopause is the most logical way to study the CO2-climate change problem.

Satellite infrared imagery, rawinsonde data, and gravity wave remote sensing of severe convective storms

Abstract: GOES digital infrared data during the time period between two hours before the touchdown of tornado and the tornado touchdown time were used in this study. Comparison between tornado-associated clouds and non-tornado-associated clouds indicates that the difference between overshooting cloud top temperature and the tropopause temperature, or how much the cloud has penetrated above the tropopause, rather than either the absolute temperature of penetrative cloud top or the height of the top of overshooting turret is significant for the possible formation of severe storms. The penetrative overshooting cloud top collapses about 15 to 30 minutes before the touchdown of tornado. Gravity waves were detected from the severe convective storms.

NASA Experiment on Tropospheric-Stratospheric Water Vapor Transport in the Intertropical Convergence Zone

Abstract: The following six papers report preliminary results obtained from a field experiment designed to study the role of tropical cumulo-nimbus clouds in the transfer of water vapor from the troposphere to the stratosphere over the region of Panama. The measurements were made utilizing special NOAA enhanced IR satellite images, radiosonde-ozonesondes and a NASA U-2 aircraft carrying. nine experiments. The experiments were provided by a group of NASA, NOAA, industry, and university scientists. Measurements included atmospheric humidity, air and cloud top temperatures, atmospheric tracer constituents, cloud particle characteristics and cloud morphology. The aircraft made a total of eleven flights from August 30 through September 18, 1980, from Howard Air Force Base, Panama; the pilots obtained horizontal and vertical profiles in and near convectively active regions and flew around and over cumulo-nimbus towers and through the extended anvils in the stratosphere. Cumulo-nimbus clouds in the tropics appear to play an important role in upward water vapor transport and may represent the principal source influencing the stratospheric water vapor budget. The clouds provide strong vertical circulation in the troposphere, mixing surface air and its trace materials (water vapor, CFM's sulfur compounds, etc.) quickly up to the tropopause. It is usually assumed that large scale mean motions or eddy scale motions transport the trace materials through the tropopause and into the stratosphere where they are further dispersed and react with other stratospheric constituents. The important step between the troposphere and stratosphere for water vapor appears to depend upon the processes occurring at or near the tropopause at the tops of the cumulo-nimbus towers. Several processes have been sugested: (1) The highest towers penetrate the tropopause and carry water in the form of small ice particles directly into the stratosphere. (2) Water vapor from the tops of the cumulonimbus clouds is transported somehow through the tropopause, the vapor pressure being controlled by the temperature at the tops of the clouds; the dryness of the stratosphere could be explained if most of the transport occurs in connection with very high clouds in regions with very high and cold tropopause. (3) Cumulo-nimbus anvils act as terrestrial-radiation shields allowing the ice particle temperatures near cloud tops to cool radiatively below the supersaturation point; this cooling would cause a vapor deposition on the ice particles which will settle out and thus act as water scavengers. The experiment was designed to collect information on these detailed physical processes near and above the tropopause in order to assess their importance and the role they play in controlling stratospheric water vapor humidity.

Aircraft sampling of the sulfate layer near the tropopause following the eruption of Mount St. Helens

Abstract: Twenty filter sampling flights of the NASA Lewis F-106 aircraft were conducted in the Great Lakes region between June 4 and August 8, 1980, following the major eruption of Mount St. Helens, Washington on May 18. The IPC-1478 filters were exposed over an altitude range spanning the local tropopause. Quarter sections were analyzed for sulfate and nitrate by ion chromatography and selected samples were analyzed for chloride by selective ion electrode. Trace elements were searched by X-ray fluorescence analysis. A filter sample taken above the tropopause on June 5 indicated a sulfate level of 50 times the baseline measurements. Subsequent measurements over a period of 2 months showed an initial dropoff and formation of a persistent layer of sulfate above the tropopause with a concentration of 10 to 18 times previously measured background-levels. Concentrations of nitrate above the tropopause exhibited considerable variability and some enhancement compared with previously measured concentration levels. It is suggested that the source of the nitrate may also be volcanic as evidenced by its temporal relationship to the sulfate concentration changes. Based on the null results of X-ray fluorescence measurements, there is no evidence of ash particle concentrations greater than 3.4 microns g/cubic m persisting in the layer above the tropopause after the second transit of the cloud.

The chlorine budget of the troposphere

Abstract: It has been hypothesized that chlorine compounds in the stratosphere could photodissociate and release atomic chlorine which catalytically destroys ozone. For an accurate assessment of the possibility of stratospheric ozone depletion, it will be necessary to know the chlorine budget of the entire atmosphere, including the troposphere and the stratosphere. Most chlorine species in the atmosphere are emitted at the surface and diffuse upward. Measurements involving chlorine are reviewed and photochemical calculations are discussed. It is found that between 0.1-1.0 ppbv of inorganic chlorine is present at the surface and about 0.02 ppbv (parts per billion by volume) at the tropopause. Most of the inorganic chlorine is believed to be in the form of HCl, and thus natural in origin. For organic chlorine the corresponding numbers are 1.9 ppbv and 1.7 ppbv, respectively. At the surface approximately 32% of the organic chlorine is natural and 68% anthropogenic.

Global distribution of stratospheric aerosols by satellite measurements

Abstract: A description is given of the first-ever global stratospheric aerosol climatology which is being developed by the earth-orbiting SAM II and SAGE satellite-based sensors. These sensors use the technique of solar occulation; that is, for every spacecraft sunrise and sunset, the modulation of solar intensity caused by the intervening earth-limb is measured. These data are mathematically inverted to yield vertical profiles of aerosol extinction coefficients with 1 km resolution. The data show seasonal variations which are similar in each hemisphere, with strong correlation between aerosol extinction and the corresponding temperature field. Typical values of extinction in the stratosphere are found to be about 0.0001 to 0.0002 per km at 1 micrometer; stratospheric optical depths at this wavelength are about 0.002. The peak extinction in the stratospheric aerosol layer follows the tropopause with altitude, with peak extinction ratios about 10 km above the local tropopause.

Tropospheric Gases, Aerosols and Photochemical Reactions Group Report

Abstract: The exploration of chemical reactions in the atmosphere near the Earth became a subject of intense interest only one decade ago. Earlier investigations were limited to components of stratospheric ozone photochemistry or of specific portions of urban air-pollution problems. It is indeed difficult for one to comprehend today how little was known conceptually two or three decades ago, unless one reviews how little was known of the composition of the air at that time. Quantitatively, one was sure only of the atmospheric amounts of N2, O2, the noble gases, CO2, H2O below the tropopause, and O3 in the stratosphere. By 1950, CH4, N2O, and CO had been detected but measured only to about 50% accuracy. The presence of tropospheric ozone was attributed to the subsidence of air from the stratosphere. The existence of the airborne particulate was known, but little information, even on bulk properties, was available. Extant data on the visible- and ultraviolet-light spectrum of the sun allowed the speculation that stratospheric ozone was important as an ultraviolet shield, but other possible absorbers were unexplored. The roles of CO2, H2O, and in climate and atmospheric dynamics were identified qualitatively but were not well understood.

Contribution of Tropospheric SO2 to the Stratospheric Aerosol Layer

Abstract: Measurements of SO2 mixing ratio in the upper troposphere and lower stratosphere have been performed with a sensitve chemi-luminescence method which permits the detection of atmospheric SO2 traces below 10 pptv. Results of 9 aircraft ascents over Europe from 1978 – 1980 are reported. It is shown that the meteorological conditions at the tropopause level have an important influence on the observed SO2 mixing ratio. The weak vertical SO2 gradients in the upper troposphere suggest only a small flux of tropospheric SO2 into the stratosphere. Furthermore, increasing SO2 mixing ratios within the first kilometers of the stratosphere give strong support to a stratospheric SO2 source due to the oxidation of organic sulfur compounds (COS, CS2). SO2 measurements are discussed in the light of improved 1 D models concerning the stratospheric sulfur budget. The results clearly show that tropospheric SO2 is of only minor importance for the non-volcanic formation of the stratospheric aerosol.