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At least 199 records · Page 11
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NASA NTRS1982

Mars' atmospheric behavior from Viking infra-red thermal mapper measurements

Data from the 15 micron band of CO2 readings with the two Viking IR thermal mappers are discussed. Contrasts were observed to be strong between clear and dusty conditions, with a latitudinal gradient and a diurnal amplitude variation in the winter southern hemisphere. Consistency was found in zonal mean temperatures in the absence of dust, with a peak temperature of 180 K at the poles and a diurnal amplitude of 15 K at the equator. Large temperature increases occur in dusty conditions, with global dust storms being present in the northern, but not southern, hemisphere. Estimations of the surface and atmospheric temperatures are calculated in order to derive optical depths from the IR measurements of atmospheric opacity. The optical depth around the whole planet is found to be relatively uniform at any given moment. Finally, the diurnal behavior of the brightness temperature is outlined for 1.4 Mars years.

Martin, T. Z.↗
NASA NTRS2012

Mars Atmospheric CO2 Condensation Above the North and South Poles as Revealed by Radio Occultation, Climate Sounder, and Laser Ranging Observations

We study the condensation of CO2 in Mars atmosphere using temperature profilesretrieved from radio occultation measurements from Mars Global Surveyor (MGS) as wellas the climate sounding instrument onboard the Mars Reconnaissance Orbiter (MRO),and detection of reflective clouds by the MGS Mars Orbiter Laser Altimeter (MOLA). Wefind 11 events in 1999 where MGS temperature profiles indicate CO2 condensation andMOLA simultaneously detects reflective clouds. We thus provide causal evidence thatMOLA non-ground returns are associated with CO2 condensation, which strongly indicatestheir nature being CO2 clouds. The MGS and MRO temperature profiles together revealthe seasonal expansion and shrinking of the area and the vertical extent of atmosphericsaturation. The occurrence rate of atmospheric saturation is maximized at high latitudes inthe middle of winter. The atmospheric saturation in the northern polar region exhibits moreintense seasonal variation than in the southern polar region. In particular, a shrinking ofsaturation area and thickness from LS 270 to 300 in 2007 is found; this is probablyrelated to a planet-encircling dust storm. Furthermore, we integrate the condensation areaand the condensation occurrence rate to estimate cumulative masses of CO2 condensatesdeposited onto the northern and southern seasonal polar caps. The precipitation flux isapproximated by the particle settling flux which is estimated using the impulse responses ofMOLA filter channels. With our approach, the total atmospheric condensation mass canbe estimated from these observational data sets with average particle size as the onlyfree parameter. By comparison with the seasonal polar cap masses inferred from thetime-varying gravity of Mars, our estimates indicate that the average condensate particleradius is 822 mm in the northern hemisphere and 413 mm in the southern hemisphere.Our multi-instrument data analysis provides new constraints on modeling the global climateof Mars.

MOLA↗
NASA NTRS1979

Martian wind activity detected by a seismometer at Viking lander 2 site

Since the Viking lander 2 seismometer (Anderson et al., 1977) located on top of the lander is extremely sensitive to Martian winds, it can provide a record of Martian wind activity. The seismograph continuously samples the wind-induced lander vibration, and its output complements meteorological data. Some pertinent seismic data are presented along with results of a preliminary spectral analysis of the data. Attention is given to wind speed/seismic noise correlation, and to long-term variation and periodicity. The results indicate that wind variations on Mars are very regular in the summer and winter seasons. Winds are light in summer and exhibit a strong diurnal periodicity, the strongest winds occurring in the early afternoon. Winds become stronger and more irregular in autumn. In all seasons nighttime conditions are usually very quiet. The high wind season correlates with the global dust storm duration. Spring is characterized by very strong though variable wind activity. Other details are also presented.

Nakamura, Y.↗
NASA NTRS1992

The seasonal cycle of carbon dioxide on Mars

Results of Viking investigations relevant to the CO2 cycle on Mars are presented, and the extensive modeling efforts directed towards understanding this cycle and its couplings to the seasonal cycles of water and dust are reviewed. It is found that winter condensation is suppressed either because the solid CO2 deposits are inefficient radiators or because of the scattering effects of CO2 clouds. With regard to the qualitative difference between the spring regression curves and between the wind systems for the two seasonal caps, it is suggested that the greater amount of aerosols in the atmosphere during northern winter results in a greater proportion of atmospheric condensation there than in the south. The seasonal pressure curves obtained by the Viking Landers during four Martian years are remarkably similar. It is suggested that the CO2 cycle is not sensitive to atmospheric dust and the meteorological variations accompanying global storms or that some subtle cancellation between different mechanisms suppresses variations.

James, Philip B.↗
NASA NTRS2019

Daily evaluation of 26 precipitation datasets using Stage-IV gauge-radar data for the CONUS

New precipitation (P) datasets are released regularly, following innovations in weather forecasting models, satellite retrieval methods, and multi-source merging techniques. Using the conterminous US as a case study, we evaluated the performance of 26 gridded (sub-)daily P datasets to obtain insight into the merit of these innovations. The evaluation was performed at a daily timescale for the period 2008–2017 using the Kling–Gupta efficiency (KGE), a performance metric combining correlation, bias, and variability. As a reference, we used the high-resolution (4 km) Stage-IV gauge-radar P dataset. Among the three KGE components, the P datasets performed worst overall in terms of correlation (related to event identification). In terms of improving KGE scores for these datasets, improved P totals (affecting the bias score) and improved distribution of P intensity (affecting the variability score) are of secondary importance. Among the 11 gauge-corrected P datasets, the best overall performance was obtained by MSWEP V2.2, underscoring the importance of applying daily gauge corrections and accounting for gauge reporting times. Several uncorrected P datasets outperformed gauge-corrected ones. Among the 15 uncorrected P datasets, the best performance was obtained by the ERA5-HRES fourth-generation reanalysis, reflecting the significant advances in earth system modeling during the last decade. The (re)analyses generally performed better in winter than in summer, while the opposite was the case for the satellite-based datasets. IMERGHH V05 performed substantially better than TMPA-3B42RT V7, attributable to the many improvements implemented in the IMERG satellite P retrieval algorithm. IMERGHH V05 outperformed ERA5-HRES in regions dominated by convective storms, while the opposite was observed in regions of complex terrain. The ERA5-EDA ensemble average exhibited higher correlations than the ERA5-HRES deterministic run, highlighting the value of ensemble modeling. The WRF regional convection-permitting climate model showed considerably more accurate P totals over the mountainous west and performed best among the uncorrected datasets in terms of variability, suggesting there is merit in using high-resolution models to obtain climatological P statistics. Our findings provide some guidance to choose the most suitable P dataset for a particular application.

Hylke E. Beck↗
NASA NTRS1995

A study of lightning in winter thunderstorms and the analysis of thunderstorm overflight data

Thunderstorms and the activities associated with them was the emphasis of this final report. The primary goal of the investigation of the dynamics, microphysics, and the electrical properties of tropical thunderstorms, was to understand the process or processes which initiate the precipitation in various convective clouds. A concept that the degree of atmospheric instability that determines the updraft velocity is different between those storms that generate electrical activity and those that do not. This is apparent in temperate latitudes, but in tropical regions, little knowledge of these interactions is available. Several ground monitoring stations have been set up and, along with a waveform recorder at one of the stations, the data collected from these stations will be analyzed in conjunction with other data collected from ship and airborne radars and airborne in situ measurements of electrical activity in coordination with the TOGA-COARE program.

Brook, Marx↗
NASA NTRS2005

Observation of NO(x) Enhancement and Ozone Depletion in the Northern and Southern hemispheres after the October-November 2003 Solar Proton Events

The large solar storms in October-November 2003 produced enormous solar proton events (SPEs) where high energetic particles reached the Earth and penetrated into the middle atmosphere in the polar regions. At this time, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) was observing the atmosphere in the 6-68 km altitude range. MIPAS observations of NO(x) (NO+NO2) and O3 of the period from 25 October to 14 November 2003 are the first global measurements of NO(x) species, covering both the summer (daylight) and winter (dark) polar regions during an SPE. Very large values of NO(x) in the upper stratosphere of 180 ppbv (parts per billion by volume) have been measured, and a large asymmetry in Northern and Southern polar cap NO(x) enhancements was found. Arctic mean polar cap (>60 deg) NO(x) enhancements of 20 to 70 ppbv between 40 to 60 km lasted for at least two weeks, while the Antarctic mean NO(x) enhancement was between 10 and 35 ppbv and was halved after two weeks. Ozone shows depletion signatures associated with both HO(x) (H+OH+HO2) and NO(x) enhancements but at different time scales. Arctic lower mesospheric (upper stratospheric) ozone is reduced by 50-70% (30-40%) for about two weeks The large solar storms in October-November 2003 produced after the SPEs. A smaller ozone depletion signal was observed in the Antarctic atmosphere. After the locally produced Arctic middle and upper stratospheric as well as mesospheric NO(x) enhancement, large amounts of NO(x) were observed until the end of December. These are explained by downward transport processes.

Lopez-Puertas, M.↗
NASA NTRS1981

Wind induced composition effects at high latitudes

The temperature and compositional structure of the upper atmosphere are discussed in relation to the impacts of wind-induced diffusion processes. Seasonal variations in thermospheric temperature and composition are explained by energy and mass transport from the summer to the winter hemisphere induced by preferential heating, with the winter oxygen bulge participating in a feedback mechanism which acts to dampen wind velocities and increase temperature contrast. Changes in the eddy diffusion coefficient are considered as a complementary mechanism of producing the seasonal anomalies. The role of winds induced by high-latitude heating by particles and Joule dissipation during magnetic storms and substorms in accounting for thermospheric density increases and N2 and Ar enhancements and O and He depletions at high latitudes are discussed, and the rather weak compositional signature of E x B momentum coupling is distinguished from the effects of Joule dissipation.

Mayr, H. G.↗
NASA NTRS1972

The light ion trough.

A distinct feature of the ion composition results from the OGO-2, 4 and 6 satellites is the light ion trough, wherein the mid-latitude concentrations of H+ and He+ decrease sharply with latitude. In contrast to the 'main trough' in electron density observed primarily as a nightside phenomenon, the light ion trough persists during both day and night. For daytime winter hemisphere conditions and for all seasons during night, the mid-latitude light ion concentration decrease is a pronounced feature. In the dayside summer and equinox hemispheres, the rate of light ion decrease with latitude is comparatively gradual, and the trough boundary is less well defined, particularly for quiet magnetic conditions. In response to magnetic storms, the light ion trough minimum moves equatorward, and deepens, consistent with earlier evidence of the contraction of the plasmasphere in response to storm time enhancements in magnetospheric plasma convection.

Taylor, H. A., Jr.↗
NASA NTRS2003

The NASA/NOAA Electronic Theater

The NASA/NOAA Electronic Theater presents Earth science observations and visualizations from space in a historical perspective. Fly in from outer space to Cambridge and Harvard University. Zoom through the Cosmos to SLC and site of the 2002 Winter Olympics using 1 m IKONOS "Spy Satellite" data. Contrast the 1972 Apollo 17 "Blue Marble" image of the Earth with the latest US and International global satellite images that allow us to view our Planet from any vantage point. See the latest spectacular images from NASA/NOAA remote sensing missions like Terra, GOES, TRMM, SeaWiFS, & Landsat 7, of storms & fires like Hurricane Isabel and the LNSan Diego firestorms of 2003. See how High Definition Television (HDTV) is revolutionizing the way we do science communication. Take the pulse of the planet on a daily, annual and 30-year time scale. See daily thunderstorms, the annual blooming of the northern hemisphere landmasses and oceans, fires in Africa, dust storms in Iraq, and carbon monoxide exhaust from global burning. See visualizations featured on Newsweek, TIME, National Geographic, Popular Science covers & National & International Network TV. Spectacular new global visualizations of the observed and simulated atmosphere & oceans are shown. See the currents and vortexes in the oceans that bring up the nutrients to feed tiny plankton and draw the fish, whales and fishermen. See the how the ocean blooms in response to El Niiioh Niiia climate changes. The Etheater will be presented using the latest High Definition TV (HDTV) and video projection technology on a large screen. See the global city lights, and the great NE US blackout of August 2003 observed by the "night-vision" DMSP satellite.

Hasler, A. F.↗
NASA NTRS2004

NASA/NOAA Electronic Theater: 90 Minutes of Spectacular Visualization

The NASA/NOAA Electronic Theater presents Earth science observations and visualizations from space in a historical perspective. Fly in from outer space to Ashville and the Conference Auditorium. Zoom through the Cosmos to SLC and site of the 2002 Winter Olympics using 1 m IKONOS 'Spy Satellite' data. Contrast the 1972 Apollo 17 'Blue Marble' image of the Earth with the latest US and International global satellite images that allow us to view our Planet from any vantage point. See the latest spectacular images from NASA/NOAA remote sensing missions like Terra, GOES, TRMM, SeaWiFS, & Landsat 7, of storms & fires like Hurricane Isabel and the LA/San Diego Fire Storms of 2003. See how High Definition Television (HDTV) is revolutionizing the way we do science communication. Take the pulse of the planet on a daily, annual and 30-year time scale. See daily thunderstorms, the annual blooming of the northern hemisphere land masses and oceans, fires in Africa, dust storms in Iraq, and carbon monoxide exhaust from global burning. See visualizations featured on Newsweek, TIME, National Geographic, Popular Science covers & National & International Network TV. Spectacular new global visualizations of the observed and simulated atmosphere and Oceans are shown. See the currents and vortexes in the Oceans that bring up the nutrients blooms in response to El Nino/La Nina climate changes. The Etheater will be presented using the latest High Definition TV (HDTV) and video projection technology on a large screen. See the global city lights, and the great NE US blackout of August 2003 observed by the 'night-vision' DMSP satellite.

Hasler, A. F.↗
NASA NTRS2004

NASA/NOAA Electronic Theater: An Hour of Spectacular Visualization

The NASA/NOAA Electronic Theater presents Earth science observations and visualizations from space in a historical perspective. Fly in from outer space to Utah, Logan and the USU Agriculture Station. Compare zooms through the Cosmos to the sites of the 2004 Summer and 2002 Winter Olympic games using 1 m IKONOS "Spy Satellite" data. Contrast the 1972 Apollo 17 "Blue Marble" image of the Earth with the latest US and International global satellite images that allow us to view our Planet from any vantage point. See the latest spectacular images h m NASA/NOAA remote sensing missions like Terra, GOES, TRMM, SeaWiF!3,& Landsat 7, of storms & fires like Hurricanes Charlie & Isabel and the LA/San Diego Fire Storms of 2003. See how High Definition Television (HDTV) is revolutionizing the way we do science communication. Take the pulse of the planet on a daily, annual and 30-year time scale. See daily thunderstorms, the annual greening of the northern hemisphere land masses and oceans, fires in Africa, dust storms in Iraq, and carbon monoxide exhaust from global burning. See visualizations featured on Newsweek, TIME, National Geographic, Popular Science covers & National & International Network TV. Spectacular new global visualizations of the observed and simulated atmosphere & oceans are shown. See the currents and vortexes in the oceans that bring up the nutrients to feed tiny plankton and draw the fish, whales and fishermen. See the how the Ocean blooms in response to El Nino/La Nina climate changes. The E-theater will be presented using the latest High Definition TV and video projection technology on a large screen. See the global city lights, and the great NE US blackout of August 2003 observed by the "night-vision" DMSP satellite.

Hasier, A. F.↗
NASA NTRS1974

Significance of semiannual waves in the mesospheric zonal wind and evidence of influence by the geomagnetic field

The recently described polar semiannual oscillations in zonal wind can explain midwinter weakening of the polar winter vortex and the relatively short stratospheric and mesospheric summer easterlies. This explanation implies that stratospheric sudden warmings may be caused or affected by the polar semiannual oscillation. Two potential physical mechanisms (not mutually exclusive) for the oscillation are presented: planetary wave action and changes in the radiation field. Radiation absorption changes are suggested to result from changes in ozone concentration during magnetic storms. Contours of amplitude of both the polar and tropical semiannual wind oscillations are more nearly congruent with geomagnetic than with geographic latitude.

Belmont, A. D.↗
NASA NTRSDate not supplied

Post-Severe Thunderstorm Damage Assessment from March 2-3, 2020, Nashville, TN, Using Synthetic Aperture Radar Observations

Severe weather events (e.g., hurricanes, tornadoes) are responsible for most weather-related infrastructure and building damages. The destruction caused by these events can cross several states, making damage estimates difficult, especially in heavily vegetated or rural areas. Drone or optical imagery is often relied upon in these cases but is limited by solar and atmospheric conditions. Synthetic Aperture Radar (SAR) is an active sensor allowing for day and night collections in all weather conditions. This research highlights the benefits and limitations of using SAR to detect tornado tracks and associated damages while also assessing the strengths and weaknesses of two SAR sensors with varying wavelengths and spatial resolutions from the March 2020 Tornado Outbreak. The outbreak occurred overnight on March 2-3, when several supercell thunderstorms tracked across multiple states producing numerous tornadoes (EF-0 through EF-4) and large hail. Most of the damage occurred in central Tennessee, resulting in 25 fatalities, hundreds of injuries, and over a billion dollars worth of damage. Publicly available C-band (~6 cm) imagery from the European Space Agency’s Sentinel-1 satellite and commercial X-band (~3 cm) imagery from Airbus’s TerraSAR-X satellite were used to generate amplitude and coherence products. The closest post-event collections were used for the amplitude products, and the closest pre- and post-collections were used to create the coherence pairs. If damage tracks were identified in any of the SAR products, the length (miles) and max width (yards) were recorded and compared to the National Weather Service Storm Data official records. SAR successfully detected five rated EF-1 or higher out of ten recorded tornadoes. However, none of the four EF-0 tornadoes were identified. X- and C-band SAR sensors are heavily impacted by dense vegetation, underestimating the extent of damage. Despite these limitations, SAR products can be beneficial when looking at severe weather impacts, especially during the winter and early spring when the coherence products are less influenced by vegetation. The upcoming L-band (~24 cm) NISAR mission will provide more accurate estimates of damage, with the longer wavelength, expanding the applications of SAR to assist in damage assessment caused by severe thunderstorms.

Hannah G Pankratz↗
NASA NTRS1994

Monitoring Mars with the Hubble Space Telescope: 1990-1991 observations

Images of Mars obtained using the Planetary Camera on the Hubble Space Telescope during 1990 and 1991 are described and analyzed. Multispectral images of Mars record the martian season between L(sub s) = 348 deg and 60 deg corresponding to late winter and spring in the northern hemisphere. The wavelengths of these observations varied between 230 nm in the ultraviolet and 890 nm in the near infrared. We use these images to discuss atmospheric and polar phenomena, to constrain the aerosols and ozone in the martian atmosphere, and to compare surface albedo features within this data set as well as with previous observations. Two methods are used to constrain the opacity of the martian atmosphere: comparisons of ultraviolet images with atmospheric scattering models and examination of contrast changes of surface features observed at visible wavelengths. Our observations are consistent with a Mars which was quite different from the planet when it was viewed by Viking; we estimate an upper limit of 0.1 for equatorial dust opacity near vernal equinox, compared to values of 0.4 to 0.5 measured in Chryse by Viking Lander 1. Later, at L(sub s) = 60 deg, and upper limit of 0.2 was found for dust in the southern hemisphere. Except for suggestions of local dust activity near the north polar cap in late spring, there was no visual evidence of dust storms on the planet. The Hartley band of ozone is within the F230W filter bandpass, and the 230W/336W ratio is therefore sensitive to ozone. High latitude ozone is observed at a concentration similar to that observed by Mariner 9; a seasonal dependence in ozone concentration was observed with concentration decreasing at northern arctic latitudes and increasing at southern midlatitudes as L(sub s) increases from 350 deg to 60 deg. Despite the difference in dust loading, the behavior of condensate clouds and the recession of the north polar cap are consistent with those observed during Viking years. Late winter images of the north polar region reveal an active north polar hood with a maximum (UV) opacity of about 0.25 near 50 deg latitude; the hood seems to have an annular form, with the central, polar regions having smaller opacity. Clouds observed in the northern hemisphere to the south of the hood boundary are suggestive of fronts similar to those observed during the Mariner 9 mission. A diurnal variation in the hood clouds which is (anti) correlated with the amount of water vapor in the atmosphere is noted. Images were deconvolved using the Richardson-Lucy iterative algorithm to remove the defocussing effects of the spherical aberration of the HST primary. Even when Mars subtended less than 5 arcsec, in May 1991, the images were scientifically useful and comparable to photographic images obtained at opposition. Although the data are subject to the solar pointing constraint for HST, the relatively slow movement of the allowed observation window, which is more than one half martian year, with respect to the martian seasons will permit us to address the question of major variations in the martian atmosphere.

James, Philip B.↗
NASA NTRS1984

Solar Flare and IMF Sector Structure Effects in the Lower Ionosphere

About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L = 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (= magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

Lastovicka, J.↗
NASA NTRS1975

Polar symmetric flow of a viscous compressible atmosphere - An application to Mars

The atmosphere is assumed to be driven by a polar symmetric temperature field. The surface pressure gradient exhibits a latitudinal dependence opposite that of the depth-averaged temperature. The magnitude of the gradient is dependent upon the depth of the boundary layer, which depends upon the eddy viscosity, the boundary conditions imposed at the surface, and upon the temperature lapse rate. Using a temperature model for Mars based on Mariner 9 infrared spectral data with a 30% increase in the depth-averaged temperature from the winter pole to the subsolar point, the increase in surface pressure from the subsolar point to the winter pole was calculated as a function of eddy viscosity with no-slip conditions imposed at the surface. The meridional cellular flow rate is correlated with the eddy viscosity, causing a complete overturning of the atmosphere in tens of days for an eddy viscosity of .1 billion sq cm/sec and in hundreds of days for 1 million sq cm/sec. The implication of this overturning in the dust storm observed during the early part of the Mariner 9 mission is discussed briefly.

Pirraglia, J. A.↗
NASA NTRS1994

Cooling the Martian atmosphere: The spectral overlap of the C02 15 micrometers band and dust

Careful consideration must be given to the simultaneous treatment of the radiative transfer of the CO2 15 micron band and dust calculations for the Martian winter polar region show that a simple sum of separately calculated CO2 cooling rates and dust cooling rates can easily result a 30 percent error in the net cooling particularly near the surface. CO2 and dust hinder each others ability to cool the atmosphere. Even during periods of low dust opacity, dust still reduces the efficacy of CO2 at cooling the atmosphere. At the other extreme, when dust storms occur, CO2 still significantly impedes the ability of dust to cool the atmosphere. Hence, both CO2 and dust must be considered in radiative transfer models.

Lindner, Bernhard Lee↗