Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Warming”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,063 records · Page 59

Development testing of large volume water sprays for warm fog dispersal

A new brute-force method of warm fog dispersal is described. The method uses large volume recycled water sprays to create curtains of falling drops through which the fog is processed by the ambient wind and spray induced air flow. Fog droplets are removed by coalescence/rainout. The efficiency of the technique depends upon the drop size spectra in the spray, the height to which the spray can be projected, the efficiency with which fog laden air is processed through the curtain of spray, and the rate at which new fog may be formed due to temperature differences between the air and spray water. Results of a field test program, implemented to develop the data base necessary to assess the proposed method, are presented. Analytical calculations based upon the field test results indicate that this proposed method of warm fog dispersal is feasible. Even more convincingly, the technique was successfully demonstrated in the one natural fog event which occurred during the test program. Energy requirements for this technique are an order of magnitude less than those to operate a thermokinetic system. An important side benefit is the considerable emergency fire extinguishing capability it provides along the runway.

Keller, V. W.↗

Dynamic characteristics of observed sudden warmings

The planetary wave dynamics of stratospheric sudden warmings in the Northern Hemisphere for a large number of observed events that occurred during winters from 1970 to 1975 and 1978 to 1981 are investigated. The analysis describes wave propagation and zonal flow interaction from the troposphere upwards to near 50 km, and in some years to near 80 km. Three primary topics are covered here: (1) the interaction of zonally propagating and quasi-stationary planetary waves during warming events; (2) planetary wave influence on zonal flow near the stratopause; and (3) planetary wave propagation to near 80 km as seen from Stratospheric and Mesospheric Sounder (SAMS) data.

Dartt, D. G.↗

An observational study of the final warming in the Southern Hemisphere stratosphere

The final warming in the Southern Hemisphere stratosphere during the period September 1-November 30 for the years 1978-1983 is studied. The change in zonally averaged temperatures during that period is almost the same for each year. However, there is substantial interannual variability in the time evolution of the warming as events of enhanced wave, mean-flow interaction associated with bursts of upward propagating planetary waves develop at different times in different years. Polar temperatures in the middle stratosphere can increase as much as about 20 K in 4 days during these events. Such dynamical processes can play a significant role in the interannual variability of stratospheric ozone and other constituents.

Farrara, John D.↗

Transport of atmospheric tracers by planetary waves during a winter stratospheric warming event - A three-dimensional model simulation

In a simple three-dimensional primitive equation model, a wave number 1 major stratospheric warming is simulated. With the aid of two idealized tracers it is shown that the transport during a major warming event is characterized by a small, well-organized tongue of subtropical air flowing around the displaced winter vortex into the polar cap and by a wide area with strong quasi-horizontal mixing (surf zone). The description of these dynamical processes requires a full three-dimensional space resolution.

Kouker, W.↗

Possible dynamical mechanisms for the Martian polar warming phenomenon

The research performed under NASA contract NAGW-727 falls into three major categories, i.e., dynamical modeling of the Martian polar warming phenomenon, studies of dust and water transport associated with a Martian polar warming, and studies of the possible effects of breaking gravity waves on the Martian atmospheric circulation. The work carried out in each of these areas is summarized.

Barnes, Jeffrey R.↗

Mass extinctions, atmospheric sulphur and climatic warming at the K/T boundary

The possible climatic effects of a drastic decrease in cloud condensation nuclei (CCN) associated with a severe reduction in the global marine phytoplankton abundance are investigated. Calculations suggest that a reduction in CCN of more than 80 percent and the resulting decrease in marine cloud albedo could have produced a rapid global warming of 6 C or more. Oxygen isotope analyses of marine sediments from many parts of the world have been interpreted as indicating a marked warming coincident with the demise of calcareous nannoplankton at the K/T boundary. Decreased marine cloud albedo and resulting high sea surface temperatures could have been a factor in the maintenance of low productivity in the 'Strangelove Ocean' period following the K/T extinctions.

Rampino, Michael R.↗

Studies of warm-rain development

The development of rain in warm (over 0 C) clouds due to the combined effects of condensation and coalescence following collisions is discussed. The detailed shape of the size distribution produced by condensation has a controlling influence on the rate of coalescence, and this shape is affected by entrainment of dry air, mixing of various cloud parcels, and radiative effects. Aspects of these processes in cloud types where rain formed through warm-rain processes are reviewed. Results suggest that diffusional growth may be enhanced in highly mixed regions of maritime cumulus in a manner similar to that in wave clouds, but that this effect is minor in updraft cores or in the stratocumulus layers examined.

Cooper, William A.↗

Infrared-selected 'warm' galaxies observed in X-rays

Infrared, optical, and X-ray observations are presented for a sample of 'warm' infrared selected galaxies listed in the IRAS Point Source Catalog. These galaxies have also been observed serendipitously in X-rays by the Einstein Observatory. From low-resolution optical spectra, it is found that all have emission lines, indicating a Seyfert or H II region type nucleus. Many of these galaxies were previously uncataloged. Based on the X-ray detection rate of this sample, it is concluded that large numbers of warm IRAS Seyfert 1-1.9 galaxies may be detectable in X-rays by future surveys such as Rosat.

Green, Paul J.↗

Greenhouse warming and the tropical water budget

The present work takes issue with some of the theses of Lindzen's (1990) work on global warming, arguing in particular that Lindzen's work is hampered by the use of oversimplified models. Lindzen then presents a detailed reply to these arguments, emphasizing the fundamental importance of the upper tropospheric water-vapor budget to the question of global warming.

Betts, Alan K.↗

The influence of the equatorial QBO on sudden stratospheric warmings

A global primitive-equation model of the stratosphere and mesosphere is integrated for specified planetary-wave forcing at the 100-mb level with mean zonal flow conditions corresponding to the westerly and easterly phases of the equatorial QBO, respectively. The responses in the two QBO phases were compared for integrations with wavenumber-1 forcing-amplitude maxima at 100 mb and 60 deg N varying from 100 to 400 m. The phase of the QBO had little effect on the results in the weak-wave (100-m) cases, which did not produce warmings, and strong-wave (400-m) cases, which produced major sudden warmings.

Holton, James R.↗

Was early Mars warmed by ammonia?

Runoff channels and valley networks present on ancient, heavily cratered Martian terrain suggests that the climate of Mars was originally warm and wet. One explanation for the formation of these channels is that the surface was warmed by the greenhouse effect of a dense, CO2 atmosphere. However, recent work shows that this theory is not consistent for the early period of the solar system. One way to increase the surface temperature predicted is to assume that other greenhouse gases were present in Mars' atmosphere in addition to CO2 and H2O. This possible gas is ammonia, NH3. If ammonia was present in sufficient quantities, it could have raised the surface temperature to 273 K. An adequate source would have been volcanic outgassing if the NH3 produced was shielded from photolysis by an ultraviolet light absorber.

Kasting, J. F.↗

Winter warming from large volcanic eruptions

An examination of the Northern Hemisphere winter surface temperature patterns after the 12 largest volcanic eruptions from 1883-1992 shows warming over Eurasia and North America and cooling over the Middle East which are significant at the 95 percent level. This pattern is found in the first winter after tropical eruptions, in the first or second winter after midlatitude eruptions, and in the second winter after high latitude eruptions. The effects are independent of the hemisphere of the volcanoes. An enhanced zonal wind driven by heating of the tropical stratosphere by the volcanic aerosols is responsible for the regions of warming, while the cooling is caused by blocking of incoming sunlight.

Robock, Alan↗

Winter warming from large volcanic eruptions

An examination of the Northern Hemisphere winter surface temperature patterns after the 12 largest volcanic eruptions from 1883-1992 shows warming over Eurasia and North America and cooling over the Middle East which are significant at the 95-percent level. This pattern is found in the first winter after tropical eruptions, in the first or second winter after midlatitude eruptions, and in the second winter after high latitude eruptions. The effects are independent of the hemisphere of the volcanoes. An enhanced zonal wind driven by heating of the tropical stratosphere by the volcanic aerosols is responsible for the regions of warming, while the cooling is caused by blocking of incoming sunlight.

Robock, Alan↗

Optically thin cirrus clouds - Radiative impact on the warm pool

The role of the radiative effects of thin cirrus clouds in the energy balance of the 'warm pool' region is examined with reference to data obtained by the Infrared Interferometer Spectrometer (IRIS) flown on the Nimbus 4 satellite in 1970. First, the IRIS observations and a method for deriving the thin cirrus information are briefly discussed. A simple radiative energy balance model is then developed which is applicable to the mesoscale convective systems in the 'warm pool'. The radiative energy balance model, which does not explicitly account for the transports, is used to demonstrate the net radiative heating produced by the thin cirrus clouds.

Prabhakara, C.↗

A Lagrangian analysis of a sudden stratospheric warming - Comparison of a model simulation and LIMS observations

Lagrangian area diagnostics and trajectory techniques are used to investigate the radiative and dynamical characteristics of a spontaneous sudden warming which occurred during a 2-yr Langley Research Center model simulation. The ability of the Langley Research Center GCM to simulate the major features of the stratospheric circulation during such highly disturbed periods is illustrated by comparison of the simulated warming to the observed circulation during the LIMS observation period. The apparent sink of vortex area associated with Rossby wave-breaking accounts for the majority of the reduction of the size of the vortex and also acts to offset the radiatively driven increase in the area occupied by the 'surf zone'. Trajectory analysis of selected material lines substantiates the conclusions from the area diagnostics.

Pierce, R. B.↗

Global variations of zonal mean ozone during stratospheric warming events

Eight years of Solar Backscatter Ultraviolet (SBUV) ozone data are examined to study zonal mean variations associated with stratospheric planetary wave (warming) events. These fluctuations are found to be nearly global in extent, with relatively large variations in the tropics, and coherent signatures reaching up to 50 deg in the opposite (summer) hemisphere. These ozone variations are a manifestation of the global circulation cells associated with stratospheric warming events; the ozone responds dynamically in the lower stratosphere to transport, and photochemically in the upper stratosphere to the circulation-induced temperature changes. The observed ozone variations in the tropics are of particular interest because transport is dominated by zonal-mean vertical motions (eddy flux divergences and mean meridional transports are negligible), and hence, substantial simplifications to the governing equations occur. The response of the atmosphere to these impulsive circulation changes provides a situation for robust estimates of the ozone-temperature sensitivity in the upper stratosphere.

Randel, William J.↗

Stratospheric Warmings During February and March 1993

Two stratospheric warnings during February and March 1993 are described using UKMO analyses, calculated PV and diabatic heating, and N2O observed by the CLAES instrument on the UARS. The first warming affected temperatures over a larger region. while the second produced a larger region of reversed zonal winds. Tilted baroclinic zones formed in the temperature field, and the polar vortex tilted westward with height. Narrow tongues of high PV and low N2O were drawn off the polar vortex, and irreversibly mixed. Tongues of material were drawn from low latitudes into the region between the polar vortex and the anticyclone; diabatic descent was also strongest in this region. Increased N2O over a broad region near the edge of the polar vortex indicates the importance of horizontal transport. N2O decreased in the vortex, consistent with enhanced diabatic descent during the warmings.

Manney, G. L.↗

Recent Warming Event in the Pacific May be an El Nino

A recent anomalous warming event in the tropical Pacific consist of a series of intraseasonal episodes, observations from four spaceborne sensors and simulation by an ocean general circulation model show. Four distinct groups of equatorial westerly wind anomalies near the date line were observed by scatterometer. Anomalous integrated water vapor was observed by a microwave radiometer. To study the warming event, the anomalous sea level and sea surface temperature were simulated with an ocean general circulation model forced by realistic winds.

Liu, W. Timothy↗