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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.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Comparison of the Seasonal Change in Cloud-Radiative Forcing from Atmospheric General Circulation Models and Satellite Observations

We compare seasonal changes in cloud-radiative forcing (CRF) at the top of the atmosphere from 18 atmospheric general circulation models, and observations from the Earth Radiation Budget Experiment (ERBE). To enhance the CRF signal and suppress interannual variability, we consider only zonal mean quantities for which the extreme months (January and July), as well as the northern and southern hemispheres, have been differenced. Since seasonal variations of the shortwave component of CRF are caused by seasonal changes in both cloudiness and solar irradiance, the latter was removed. In the ERBE data, seasonal changes in CRF are driven primarily by changes in cloud amount. The same conclusion applies to the models. The shortwave component of seasonal CRF is a measure of changes in cloud amount at all altitudes, while the longwave component is more a measure of upper level clouds. Thus important insights into seasonal cloud amount variations of the models have been obtained by comparing both components, as generated by the models, with the satellite data. For example, in 10 of the 18 models the seasonal oscillations of zonal cloud patterns extend too far poleward by one latitudinal grid.

Cess, R. D.↗
NASA NTRS1967

The winter helium bulge.

Diurnal atmospheric density bulge shifts observed by Explorer, showing latitudinal-seasonal variation in helium concentration

ATMOSPHERIC DENSITY↗
NASA NTRS1992

Simulations of the seasonal polar caps on Mars

One of the most puzzling mysteries about the planet Mars is the hemispherical asymmetry in the polar caps. Every spring the seasonal polar cap of CO2 recedes until the end of the summer, when only a small part, the residual polar cap, remains. Scientists have sought to explain this asymmetry by modeling observations of the latitudinal recession of the polar cap and seasonal variations in atmospheric pressure (since the seasonal polar caps are primarily frozen atmosphere, they are directly related to changes in atmospheric mass). These models reproduce most aspects of the observed annual variations in atmospheric pressure fairly accurately. Furthermore, the predicted latitudinal recession of the northern polar cap in the spring agrees well with observations, including the fact that the CO2 ice is predicted to completely sublime away during the summer in the Southern Hemisphere, unlike what is observed. This power will show how the radiative effects of ozone, clouds, and airborne dust, light penetration into and through the polar caps, and the dependence of albedo on solar zenith angle affect CO2 ice formation and sublimation, and how they help explain the hemispherical asymmetry in the residual polar caps. These effects have not been studied with prior polar cap models.

Lindner, Bernhard Lee↗
NASA NTRS1992

Why is the north polar cap on Mars different than the south polar cap?

One of the most puzzling mysteries about the planet Mars is the hemispherical asymmetry in the polar caps. Every spring, the seasonal polar cap of CO2 recedes until the end of summer, when only a small part, the residual polar cap, remains. During the year that Viking observed Mars, the residual polar cap was composed of water ice in the Northern Hemisphere (Kieffer et al., Science, 194, 1341, 1976) but was primarily carbon dioxide ice in the Southern Hemisphere (Kieffer, J. Geophys. Res., 84, 8263, 1979). Scientists have sought to explain this asymmetry by modeling observations of the latitudinal recession of the polar cap and seasonal variations in atmospheric pressure (since the seasonal polar caps are primarily frozen atmosphere, they are directly related to changes in atmospheric mass). These models reproduce most aspects of the observed annual variation in atmospheric pressure fairly accurately. Furthermore, the predicted latitudinal recession of the northern polar cap in the spring agrees well with observations, including the fact that the CO2 ice is predicted to completely sublime away. However, these models all predict that the carbon dioxide ice will also sublime away during the summer in the Southern Hemisphere, unlike what is observed. This paper will show how the radiative effects of ozone, clouds, and airborne dust, light penetration into and through the polar cap, and the dependence of albedo on solar zenith angle affect CO2 ice formation and sublimation, and how they help explain the hemispherical asymmetry in the residual polar caps. These effects have not been studied with prior polar cap models.

Lindner, Bernhard Lee↗
NASA NTRS1992

Simulations of the seasonal polar caps on Mars

One of the most puzzling mysteries about the planet Mars is the hemispherical asymmetry in the polar caps. Every spring the seasonal polar cap of CO2 recedes until the end of summer, when only a small part, the residual polar cap, remains. During the year that Viking observed Mars, the residual polar cap was composed of water ice in the Northern Hemisphere (Kieffer et al., Science, 194, 1341, 1976), but was primarily carbon dioxide ice in the Southern Hemisphere (Kieffer, J. Geophys. Res., 84, 8263, 1979). Scientists have sought to explain this asymmetry by modeling observations of the latitudinal recession of the polar cap and seasonal variations in atmospheric pressure (since the seasonal polar caps are primarily frozen atmosphere, they are directly related to changes in atmospheric mass). These models reproduce most aspects of the observed annual variation in atmospheric pressure fairly accurately. Furthermore, the predicted latitudinal recession of the northern polar cap in the spring agrees well with observations, including the fact that CO2 ice is predicted to completely sublime away. However, these models all predict that the carbon dioxide ice will also sublime away during the summer in the Southern Hemisphere, unlike what is observed. It is shown here how the radiative effects of ozone, clouds, and airborne dust, light penetration into and through the polar cap, and the dependence of albedo on solar zenith angle affect CO2 ice formation and sublimation, and how they help explain the hemispherical asymmetry in the residual polar caps. These effects have not been studied with prior polar cap models. The combination of the effects of solar zenith angle on albedo and the radiative effects of clouds and dust act to extend the lifetime of CO2 ice on the south pole relatively more than on the north pole, possibly explaining the hemispherical asymmetry in the residual polar caps without the need of a hemispherical asymmetry in polar cap albedo. This does not imply that a hemispherical asymmetry in polar cap albedo does not exist, but that one is not necessary. Observations of the regression of the polar caps and the annual cycle in atmospheric pressure are reproduced fairly well by the model, as shown in the figures, although further improvement is needed. When CO2 ice is retained at the south pole, the model predictions of the annual cycle in atmospheric pressure have a phase shift relative to the data, no matter what model input parameters are used. We are investigating other processes not included in prior polar cap models.

Lindner, Bernhard Lee↗
NASA NTRS1994

Why is the north polar cap on Mars different than the south polar cap?

One of the most puzzling mysteries about the planet Mars is the hemispherical asymmetry in the polar caps. Every spring the seasonal polar cap of CO2 recedes until the end of summer, when only a small part, the residual polar cap, remains. During the year that Viking observed Mars, the residual polar cap was composed of water ice in the northern hemisphere but was primarily carbon dioxide ice in the southern hemisphere. Scientists have sought to explain this asymmetry by modeling observations of the latitudinal recession of the polar cap and seasonal variations in atmospheric pressure (since the seasonal polar caps are primarily frozen atmosphere, they are directly related to changes in atmospheric mass). These models reproduce most aspects of the observed annual variation in atmospheric pressure fairly accurately. Furthermore, the predicted latitudinal recession of the northern polar cap in the spring agrees well with observations, including the fact that the CO2 ice is predicted to completely sublime away. However, these models all predict that the carbon dioxide ice will also sublime away during the summer in the southern hemisphere, unlike what is observed. This paper will show how the radiative effects of ozone, clouds, airborne dust, light penetration into and through the polar cap, and the dependence of albedo on solar zenith angle affect CO2 ice formation and sublimation, and how they help explain the hemispherical asymmetry in the residual polar caps. These effects have not been studied with prior polar cap models.

Lindner, Bernhard Lee↗
NASA NTRS2000

In-Situ Environmental Measurements Needed for Future Mars Missions

Existing measurements and modeling studies indicate that the climate and general circulation of the thin, predominately CO2 Martian atmosphere are characterized by large-amplitude variations with a wide range of spatial and temporal scales. Remote sensing observations from Earth-based telescopes and the Mariner 9, Viking, Phobos, and Mars Global Surveyor (MGS) orbiters show that the prevailing climate includes large-scale seasonal variations in surface and atmospheric temperatures (140 to 300 K), dust optical depth (0.15 to 1), and water vapor (10 to 100 precipitable microns). These observations also provided the first evidence for episodic regional and global dust storms that produce even larger perturbations in the atmospheric thermal structure and general circulation. In-situ measurements by the Viking and Mars Pathfinder Landers reinforced these conclusions, documenting changes in the atmospheric pressure on diurnal (5%) and seasonal (>20%) time scales, as well as large diurnal variations in the near-surface temperature (40 to 70 K), wind velocity (0 to 35 m/s), and dust optical depth (0.3 to 6). These in-situ measurements also reveal phenomena with temporal and spatial scales that cannot be resolved from orbit, including rapid changes in near-surface temperatures (+/- 10 K in 10 seconds), large near-surface vertical temperature gradients (+/- 15 K/meter), diurnally-varying slope winds, and dust devils . Modeling studies indicate that these changes are forced primarily by diurnal and seasonal variations in solar insolation, but they also include contributions from atmospheric thermal tides, baroclinic waves (fronts), Kelvin waves, slope winds, and monsoonal flows from the polar caps.

Crisp, D.↗
NASA NTRS1973

Short and long periodic atmospheric variations between 25 and 200 km

Previously collected data on atmospheric pressure, density, temperature and winds between 25 and 200 km from sources including Meteorological Rocket Network data, ROBIN falling sphere data, grenade release and pitot tube data, meteor winds, chemical release winds, satellite data, and others were analyzed by a daily difference method and results on the distribution statistics, magnitude, and spatial structure of gravity wave and planetary wave atmospheric variations are presented. Time structure of the gravity wave variations were determined by the analysis of residuals from harmonic analysis of time series data. Planetary wave contributions in the 25-85 km range were discovered and found to have significant height and latitudinal variation. Long period planetary waves, and seasonal variations were also computed by harmonic analysis. Revised height variations of the gravity wave contributions in the 25 to 85 km height range were computed. An engineering method and design values for gravity wave magnitudes and wave lengths are given to be used for such tasks as evaluating the effects on the dynamical heating, stability and control of spacecraft such as the space shuttle vehicle in launch or reentry trajectories.

Justus, C. G.↗
NASA NTRS1985

Mesospheric winds observed by the Kyoto meteor radar

The Kyoto meteor radar has been operated almost continuously from May 1983. By using a large amount of radar data, seasonal variations of mean winds, planetary waves and atmospheric tides can be delinated. Seasonal and latitudinal variation of tidally corrected mean winds including Kyoto observations have been examined in comparison with the CIRA 1972 model. A power spectral density of the zonal wind field for 60 days of data is formed from an autocorrelation function with a maximum time lag of 30 days. A quasi-2-day oscillation was evident in the period from June to September, and seems to be repeated in 1983 and 1983. It had large amplitudes in June and July and became weak in August; then it was again amplified in September. In summer months, the period of the wave was indicated as 2.2 days, and it became shorter in September. At Kyoto (35 deg N), the diurnal tide is the main component of atmospheric tides. The monthly mean amplitude of the eastward component of diurnal tide is plotted for the period from May 1983 to September 1984. It was clearly amplified in summer months at around 92 to 96 km altitudes. This feature was repeated in two successive years except for the maximum amplitude which exceeded 40 m/sec and 30 m/sec in 1983 and 1984, respectively.

Tsuda, T.↗
NASA NTRS1986

Lidar observations of the decline of the El Chichon stratospheric load

The eruption of the Mexican volcano El Chichon in Apr. 1982 enhanced the stratospheric aerosol load to a level which so far has not been observed by remote sensing techniques. The ruby lidar system at Garmisch-Partenkirchen recorded an increase of about two orders of magnitude above the background level of the years 1977/78. At northern midlatitudes backscattering was peaking in Jan./Feb. 1983, as illustrated. The decline of the El Chichon stratospheric perturbation is discussed. The decay of the El Chichon stratospheric cloud is characterized by an overall 1/e lifetime of about 12 months. The El Chichon decay is further characterized by seasonal variations of the integral backscattering coefficient, which exhibit a winter maximum and a summer minimum. These variations are inversely correlated with the seasonal mean movement of the tropopause height indicating transport processes.

Jaeger, H.↗
NASA NTRS2016

Detection of Northern Hemisphere Transient Baroclinic Eddies at Gale Crater Mars

The Rover Environmental Monitoring Station (REMS) on the Mars Science Laboratory’s (MSL) Curiosity rover has been operating in Gale Crater Mars (4.5°S, 137.4°E) for over 2 Mars years. Analysis of its pressure data, which have a precision of approximately 0.2 Pa (see Haberle et al., 2014; Harri et al., 2014), reveal temporal oscillations in its seasonally de-trended daily averaged pressures at some seasons with 2-5 Pa amplitudes that have periods similar to those observed at the Viking Lander 2 (VL-2) site (48.3°N, 134.0°E) several decades ago. As illustrated in Fig 1 there are clear peaks in the variance at a frequency f approximately 0.45 and 0.06 per sol for the fall season of Mars Year (MY) 31, and at f approximately 0.15 and 0.06 per sol for MY 32. These frequencies correspond to periods of 2.2, 6.7, and 16.7 sols, and are very similar to those observed at VL-2 (Fig 2, and see Barnes, 1980). Since orbital imaging data show dust frontal systems associated with eastward traveling baroclinic eddies that occasionally cross the equator (Wang et al., 2003), these findings suggest that MSL may be seeing their signature in its pressure data. To make this case we show that (a) the spectral peaks in the MSL are not only similar to those at VL-2, they have the same seasonal variation, (b) at least for some seasons the peaks are statistically significant and not likely due to random noise in the data, and (c) Global Circulation Model (GCM) results from the Ames GCM support this interpretation.

The Rover Environmental Monitoring Station (REMS)↗
NASA NTRS1989

OH-asterisk (7-5) Meinel band dayglow and nightglow measured by the SME limb scanning near infrared spectrometer - Comparison of the observed seasonal variability with two-dimensional model simulations

Seasonal variations of the OH-asterisk (7-5) mesospheric hydroxyl emission at 1.89 microns observed by the SME near-IR spectrometer are compared with the theoretical predictions of a two-dimensional dynamical/chemical model. The good agreement found at low latitudes for both dayglow and nightglow provides support for the model assumption that breaking gravity waves induce seasonal and latitudinal variations in diffusion. The seasonal behavior of atomic hydrogen in the upper mesosphere (related to vertical transport) and/or uncertainties in the OH Meinel band parameters are proposed as possible explanations for the discrepancy noted between model and observational data for the middle latitudes.

Le Texier, H.↗
NASA NTRS1988

Wintertime losses of ozone in high northern latitudes

Total column ozone data over the past 22 to 30 years from ground-based Dobson and filter ozonometer stations between 30 N and 80 N are analyzed for residual trends remaining after allowance for the known geophysical variations corresponding to: (1) the change of seasons; (2) the quasi-biennial oscillation; and (3) the 11-year solar sunspot cycle. Examination of the data from several ground stations between 45 and 55 N indicated a seasonal difference in the long-term ozone series, with statistically significant losses in several winter months. Accordingly, the data from individual stations were analyzed with multiple regression analysis, seeking trends on a monthly basis after allowance for the known geophysical cycles. Previous statistical analyses were conducted as tests of 1-D model calculations which do not show any differences with the seasons, and any trend toward change in ozone concentrations is expressed in a yearly trend without seasonal variation. Such a model is inappropriate for calculations with a data set which exhibits a pronounced tendency toward seasonal differences in the trends. Comparisons with model calculations then require 2-D models into which seasonal and latitudinal differences can easily be programmed.

Harris, Neil↗