The temperature variations in the troposphere,stratosphere, and mesosphere of the Northern Hemisphere, 1965–1981

We have used temperature data obtained from radiosondes and rocketsondes for the time interval 1965–1981 to estimate the interconnection of mean-annual temperature fluctuations at the various layers from the surface to the lower mesosphere of the Northern Hemisphere. Profiles of coefficients of correlation of the mean-annual temperature at each layer with mean-annual temperature at higher layers are shown for locations in the low, middle, and high latitudes. It is suggested that the mean-annual temperature variations at high latitudes of the troposphere are related with mean-annual temperature variations of the high latitudes of the lower stratosphere. Also, the mean-annual temperature variations at the high latitudes of the lower stratosphere are connected with mean-annual temperature variations at the high latitudes of the upper stratosphere. Furthermore, the mean-annual temperature variations of the upper stratosphere have an impressive correlation with mean-annual temperature variations of the lower mesosphere for whole northern hemisphere.     

Long wavelength ground surface temperature history from continuous temperature logs in the Transylvanian Basin

Continuous temperature logs to depths between 750 and 1400 m in the Transylvanian Basin, Romania, in many cases show temperature gradient variations with depth which cannot be explained by depth variations in thermal conductivity, topography and ground water flow. The only possible responsible agent seems to be past surface temperature variations. The temperature logs from nine boreholes have been interpreted individually and jointly by least squares inverse modelling with the surface temperature history and background heat flux as unknown parameters. All the temperature profiles are consistent with a temperature rise at the end of the last glaciation. The effects of borehole depth, of a wrong choice of thermal conductivity, and the level of uncorrelated random noise were examined using synthetic examples.     

Absolute measurements and computed values for Martian irradiance between 10.5 and 12.5 μm

The combination of seasonal and orbital changes in Martian insolation result in complex latitude dependent surface temperature variations that effect the total radiance of the planet as seen from the earth. These surface temperature variations have been calculated, based upon a computer simulation of the thermal environment of the planet. The temperature variations are then integrated to yield the total radiance of the planet as seen from the earth as a function of time. The absolute radiance of Mars was measured on April 4, 1971, with a balloon-borne radiometer system operating in the wavelength range between 10.5 and 12.5 μm. The average brightness temperature of the Mars disk determined from these measurements was 254°K with a 1 σ error of 4°K.     

A first look at atmospheric dynamics and temperature variations on Titan

Pollack (1973) has used a radiative equilibrium model to match radiometric data for Titan and infers the atmospheric mass, composition, opacity, and gross vertical thermal structure. These results are used to estimate the atmospheric temperature variations by means of scaling analysis, taking into account dynamics both for a baroclinic wave regime and for an axially symmetric circulation regime. Horizontal temperature variations of the atmosphere and surface are found to be very small, and the circulation is found to be weak and probably axially symmetric. The small temperature variations appear to preclude the storage of volatiles in polar caps, so that the present atmospheric methane content may be due to a balance between outgassing and photodissociation.     

Free convection and mass transfer effects on the unsteady laminar boundary-layer accelerated flow past a vertical porous limiting surface with uniform suction

An analysis of the mass transfer and free convection effects on the unsteady laminar accelerated flow of a viscous incompressible fluid past an infinite vertical porous limiting surface is presented when the free stream is accelerated and the limiting surface temperature and concentration changes with step-wise variations. Expressions for velocity and skin-friction are obtained by using Laplace transform, when the Prandtl number and the Schmidt number are equal to one. Graphs showing variations of velocity and skin-friction, for different values of Gr (Grashof number) and Gc (modified Grashof number) are plotted, and the results of them are discussed.     

Interpretation of the lunar microwave brightness temperature spectrum: Feasibility of orbital heat flow mapping

A detailed model of the lunar regolith is analyzed to examine the feasibility of an orbital mapping of heat flow using microwave radiometers. For regolith thermal and electrical properties which are representative of Apollo findings, brightness temperature observations in the bandλ = 5–30 cm would be required for heat flow analysis. Spectral variations shortward of 5 cm are controlled primarily by the temperature dependencies of the thermal conductivity and electrical absorption within the diurnal-varying layer. For wavelengths longer than 30 cm, unwanted emission from high impedance subregolith layers can be significant and size limitations on spacecraft radiometers is a factor. Over the 5- to 30-cm band, lunation-averaged brightness temperature increases of 2–10°K are predicted for heat flow values representative of the Apollo measurements. The magnitude of this increase depends directly on the value of regolith microwave absorption. For absorption values consistent with Apollo laboratory measurements, a spectral increase of 5°K is predicted. This value is considered marginally sufficient for an orbital heat flow measurement. However, important non-heat flow effects must be accounted for. Spectral variations can occur due to surface topography and subsurface scattering. For nadir viewing, surface roughness effects are not expected to be significant and topographic effects are nearly constant with wavelength for λ > 5cm. Volume scattering due to subsurface rock fragments can cause emission darkening of 1–6°K. However, spectral variations will not be large unless the distribution of scatterer sizes is sharply skewed. For the Moon, the most serious spurious effect appears to be emissivity variations due to the near-surface density gradient. A brightness temperature decrease of 10°K is predicted from centimeter to decameter wavelengths. If the transition from porous surface fines to compacted regolith soil occurs rapidly (within the upper 3–5 cm), most of the emissivity decrease will occur in the 5- to 30-cm wavelength band. It is recommended that complementary radar measurements be utilized to augment constraints on regolith emissivity and scattering properties.     

Vertical-structure effects on planetary microwave brightness temperature measurements: Applications to the lunar regolith

The effects of vertical variations in density and dielectric constant on nadir-viewing microwave brightness temperatures are examined. Stratification models as well as models of a continuous increase in density with depth are analyzed. Specific applications address the vertical structure of the lunar frontside regolith, utilizing combined constraints from Apollo data, bistatic radar signatures, and Earth-based measurements of the lunar microwave brightness temperature.Results have been analyzed in terms of the effects on the zeroth and first harmonic of the lunar disk-center brightness temperature variation over a lunation, and their wavelength dependence. Lunation-mean brightness temperatures, which are diagnostic of emissivity and steady-state sub-surface temperatures, are sensitive to both near-surface soil density gradients and single high-impedance dielectric contrasts. Models of the rapid density increase in the upper 5–10 cm of the lunar regolith predict brightness temperature decreases of 2–10°K between λ₀ = 3 and 30 cm. The magnitude of this spectral variation depends upon the thickness of a postulated low-density surface coating layer, and the magnitude of the density gradient in the transition soil layer. Comparable decreases in brightness temperature can be produced by a stratified two-layer model of soil overlaying bedrock if the high-density substrate lies within 1–2 m of the surface. Multiple soil layering on a centimeter scale, such as is observed in the Apollo core samples, is not likely to induce spectral variations in mean brightness temperature due to rapid regional variations in layer depths and thicknesses.The fractional variation in disk-center brightness temperature over a lunation (first harmonic) can be altered by vertical-structure effects only for the case in which a larger and abrupt dielectric contrast exists within the upper surface layer where the significant diurnal variations in physical temperature occur. Soil density variations do not cause scattering effects sufficient to significantly alter the microwave emission weighting function within the diurnal layer. For the Moon, this layer consists of the upper 10 cm. Since no widespread rock substrate as shallow as 10 cm exists in the lunar frontside, only volume scattering effects, due to buried shallow rock fragments, can explain the apparent high electrical loss inferred from Earth-based measurements of the amplitude of lunation brightness temperature variations.Representative models of the lunar frontside vertical structure have also been examined for their effects of radar cross-section measurements and resultant inferences of bulk dielectric constant. Models of the near-surface density gradient predict a significant increase in the remotely inferred dielectric constant value from centimeter to meter wavelengths. Such a model is in general agreement with the dielectric constant spectrum inferred from Earth-based brightness temperature polarization measurements, but is difficult to reconcile with the Apollo bistatic radar results at λ₀ = 13 and 116 cm.     

Dielectric properties of lunar surface

Measurements of the dielectric characteristics of lunar soil samples are analyzed in the context of dielectric theory. It has been shown that the real component of the dielectric permittivity and the loss tangent of rocks greatly depend on the frequency of the interacting electromagnetic field and the soil temperature. It follows from the analysis that one should take into account diurnal variations in the lunar surface temperature when interpreting the radar-sounding results, especially for the gigahertz radio range.     

Free convection and mass transfer effects on the control of the unsteady boundary layer on an infinite vertical porous limiting surface

The present study presents an analytical solution to the flow field of the unsteady laminar accelerated flow of a viscous incompressible fluid past an infinite vertical porous limiting surface, when the freestream is accelerated and the limiting surface temperature and concentration are given functions of time. The expressions for the velocity, temperature and skin friction are obtained by using Laplace transform, when the Prandtl and Schmidt numbers are given. Graphs showing variations of the velocity and the skin friction, for different values ofG _r andG _c (modified Grashof number), as well as of the temperature are plotted and the results are discussed.     

The thermal history of the moon

A simple analysis shows that the normal assumption of an outward heat flow, together with the normally assumed surface layer of low thermal conductivity, would give rise to microwave emission effects and to local variations in surface temperature which are not in fact observed. It is concluded that either the surface layer must be much thinner than is at present postulated, or that the outward flow of heat must be much smaller than is supposed.     

Titan's surface from Cassini RADAR SAR and high resolution radiometry data of the first five flybys

The first five Titan flybys with Cassini's Synthetic Aperture RADAR (SAR) and radiometer are examined with emphasis on the calibration and interpretation of the high-resolution radiometry data acquired during the SAR mode (SAR-radiometry). Maps of the 2-cm wavelength brightness temperature are obtained coincident with the SAR swath imaging, with spatial resolution approaching 6 km. A preliminary calibration shows that brightness temperature in these maps varies from 64 to 89 K. Surface features and physical properties derived from the SAR-radiometry maps and SAR imaging are strongly correlated; in general, we find that surface features with high radar reflectivity are associated with radiometrically cold regions, while surface features with low radar reflectivity correlate with radiometrically warm regions. We examined scatterplots of the normalized radar cross-section σ⁰ versus brightness temperature, finding differing signatures that characterize various terrains and surface features. Implications for the physical and compositional properties of these features are discussed. The results indicate that volume scattering is important in many areas of Titan's surface, particularly Xanadu, while other areas exhibit complex brightness temperature variations consistent with variable slopes or surface material and compositional properties.     

A simplified model for deriving planetary surface temperatures as a function of atmospheric chemical composition

The surface temperature of a planet with an atmosphere depends, amongst other factors, on the atmospheric chemical composition and surface pressure. However, the detailed calculation of surface temperature variations as a function of atmospheric composition is extremely complex. We therefore present in this paper a simplified model which can be used to follow surface temperature changes over periods up to the lifetime of the solar system. We apply this model to a number of chemical constituents of interest in studying the evolution of planetary atmospheres (with special reference to the Earth).     

Some features of climate change on Earth and its possible relation to solar-activity variations

The global warming on Earth during the last century has been discussed in many studies. The most significant factors of climate change are the increase in the atmospheric concentration of greenhouse gases, catastrophic eruptions of volcanoes, and variations in the solar activity. In this paper, we consider the character of climate change and its possible relation to solar-activity variations using the data of the global network of meteorological stations on temperature variations in different regions across the globe from 1880 and information about variations in the relative sunspot number over the last 300 years and temporal variations in the total solar irradiation. We found that the annual mean sunspot number increased on average by about 0.2% per year in both 11-year and secular cycles. The increase in the globally averaged surface air temperature in the period 1880–2004 was Δt = 0.61 ± 0.04 °C. The difference in Δt calculated for periods with different solar-activity levels in 11-year cycles was estimated. This difference was most clearly revealed over land at high latitudes of the northern hemisphere. The medians of the distributions of the annual mean surface air temperature over land, ocean, and over the entire globe in years with high solar activity in the secular cycle are significantly greater than the corresponding values related to the years of low solar activity. Noticeable falls in temperature (by ～0.1–0.2°C) through ～1900–1920 and 1945–1980 are likely to be associated with the radiation balance perturbation caused by a large number of catastrophic volcanic eruptions during these periods. A considerable warming during the last three decades is most probably due to the substantial growth in the rate of carbon dioxide input to the atmosphere and the corresponding large increase in its concentration. The importance of this factor of global warming becomes even greater if we bear in mind that the solar activity in the secular cycle declines after 1970.     

A model of temporal variations in ozone density in the Martian atmosphere

Temporal variations of the Martian ozone density profile at high latitudes have been calculated for an entire Martian year, taking into account the seasonal and diurnal variations in temperature, water vapor and solar radiation. A new technique facilitates the long-term model calculations, including diurnal variations. The result is in better agreement with MARINER 9 observations of the time and magnitude of the seasonal maximum than is the result of the previous seasonal model calculated for the diurnally averaged temperature, water vapor and solar radiation. The large scatter of the MARINER 9 data may be partly experimental, but the effect of surface condition, including the water vapor variability and the surface chemistry, may explain some of the dispersion of the observed data. The predicted diurnal variation is substantial except near solstices, and the nighttime total column density is generally larger than the daytime value. The magnitude of the day-and-night difference and the shape of the diurnal variation change markedly with season. The opposite temporal variation is predicted for ozone density between the upper and lower regions. The model predicts the production of a ozone layer at 35–50 km, which is consistent with observations at low latitudes by MARS-5. The observed ozone density may be explained, if the atmospheric temperature is as low as ～ 140 K or if the atmosphere is subsaturated. Effects of the simultaneous existence of an aerosol layer, also observed by MARS-5, are briefly discussed.     

Evidence for subsurface water ice in Korolev crater, Mars

Following the work of Kieffer and Titus (2001, Icarus 154, 162-180), we present results of thermal IR observations of Korolev crater, located at ∼73° latitude in the martian northern polar region. Similar to techniques employed by Titus et al. (2003, Science 299, 1048-1050), we use infrared images from the Thermal Emission Imaging System (THEMIS) aboard Mars Odyssey to identify several regions within the crater basin with distinct thermal properties that correlate with topography. The THEMIS results show these regions exhibit temperature variations, spatially within the crater and throughout the martian year. In addition to the variations identified in the THEMIS observations, Mars Global Surveyor Thermal Emission Spectrometer (TES) observations show differences in albedo and temperature of these regions on both daily and seasonal cycles. Modeling annual temperature variations of the surface, we use TES observations to examine the thermal properties of these regions. This analysis reveals the crater interior deposits are likely thick layers (several meters) of high thermal inertia material (water ice, or extremely ice-rich regolith). Spatial variations of the physical properties of these regions are likely due to topography and possibly variations in the subsurface material itself. The nature of these deposits may help constrain polar processes, as well as provide context for the polar lander mission, Phoenix.     

The depth of the convective boundary layer on Mars

We are using observations obtained with Mars Express to explore the structure and dynamics of the martian lower atmosphere. We consider a series of radio occultation experiments conducted in May-August 2004, when the season on Mars was midspring of the northern hemisphere. The measurements are widely distributed in latitude and longitude, but the local time remained within a narrow range, 17.0-17.2 h. Most of the atmospheric profiles retrieved from these data contain a distinct, well-mixed convective boundary layer (CBL). We have accurately determined the depth of the CBL and its spatial variations at fixed local time through analysis of these profiles. The CBL extends to a height of 3-10 km above the surface at the season and locations of these measurements. Its depth at fixed local time is clearly correlated with variations in surface elevation on planetary scales, with a weaker dependence on spatial variations in surface temperature. In general, the CBL is deep (8-10 km) where the surface elevation is high, as in Tharsis Montes and Syrtis Major, and shallow (4-6 km) where the surface elevation is low, as in Amazonis and Utopia. This variability results from the combined effects of conditions near the surface and in the atmosphere above the CBL. Convection arises from solar heating of the ground, and the impact of this heat source on thermal structure is largest where the surface pressure and atmospheric density are smallest, at high surface elevations. The vertical extent of the CBL is in turn constrained by the static stability of the overlying atmosphere. These results greatly reduce the long-standing uncertainty concerning the depth of the CBL.     

The dependence of the climate sensitivity on convective parametrization: statistical evaluation

Two sensitivity experiments, in which CO₂ is instantaneously doubled, have been performed with a general circulation model to determine the influence of the convective parametrization on simulated climate change. We have examined the spatial structure of changes in the annual mean and annual cycle for surface temperature and precipitation for both experiments; similarly we have examined changes in the variance for these two fields. We have also computed a range of test statistics in order to obtain reliable measures of the signal-to-noise ratio in the climate change signal from each experiment. We have computed test statistics for the entire globe and for five different region and we contrast the global response with the response in the Australian region taken as a representative sample.We find that the highest signal-to-noise ratios in the change from 1 * CO₂ to 2 * CO₂ are for the change in surface temperature for both experiments with little difference in the global averages between the experiments. Globally averaged precipitation shows a greater noise level but perhaps the greatest contrast between experiments. There are generally significant increases in the temporal and spatial variability of precipitation in the change from the 1 * CO₂ to 2 * CO₂ and with some differences apparent between the two experiments. The temporal variability of surface temperature does not change significantly in any of the 2 * CO₂ cases, and there is little difference between the experiments. There is a significant decrease in the spatial variability of surface temperature in all 2 * CO₂ experiments in all cases and with significant differences in the seasonal variations between different experiments. The spatial variability of precipitation increases in all 2 * CO₂ cases and also with substantial differences in the seasonal variations between the experiments. There are accompanying significantly different spatial pattern correlations for both surface temperature and precipitation. In general we find that the global changes are fairly robust with the differences associated with convective parametrization schemes being very small. However, at the regional level, there are marked differences between experiments with changes both in the means and in the spatial and temporal variances but often with low levels of significance.     

Thermal behavior of horizontally mixed surfaces on Mars

Current methods for deriving thermal inertia from spacecraft observations of planetary brightness temperature generally assume that surface properties are uniform for any given observation or co-located set of observations. As a result of this assumption and the nonlinear relationship between temperature and thermal inertia, sub-pixel horizontal heterogeneity may yield different apparent thermal inertia at different times of day or seasons. We examine the effects of horizontal heterogeneity on Mars by modeling the thermal behavior of various idealized mixed surfaces containing differing proportions of either dust, sand, duricrust, and rock or slope facets at different angles and azimuths. Latitudinal effects on mixed-surface thermal behavior are also investigated. We find large (several 100 J m⁻² K⁻¹ s^−1/2) diurnal and seasonal variations in apparent thermal inertia even for small (∼10%) admixtures of materials with moderately contrasting thermal properties or slope angles. Together with similar results for layered surfaces [Mellon, M.T., Putzig, N.E., 2007. Lunar Planet. Sci. XXXVIII. Abstract 2184], this work shows that the effects of heterogeneity on the thermal behavior of the martian surface are substantial and may be expected to result in large variations in apparent thermal inertia as derived from spacecraft instruments. While our results caution against the over-interpretation of thermal inertia taken from median or average maps or derived from single temperature measurements, they also suggest the possibility of using a suite of apparent thermal inertia values derived from single observations over a range of times of day and seasons to constrain the heterogeneity of the martian surface.     

Evidence of climatic warming in the southern Urals region derived from borehole temperatures and meteorological data

Thirty borehole temperature–depth profiles in the central and southern Urals, Russia were scrutinized for evidence of ground surface temperature histories. We explored two inversion schemes: a simple ramp inversion in which solutions are parameterized in terms of an onset time and magnitude of change and a more sophisticated functional space inverse algorithm in which the functional form of the solution is left unspecified. To enhance and potentially identify latitudinal differences in the ground surface temperature signal, we subdivided the data into three groups based on geographic proximity and simultaneously inverted the borehole temperature–depth logs. The simultaneous inversions highlighted 13 temperature–depth logs that could not both fit a common ground surface temperature history and a priori models within reasonable bounds. Our results confirm that this is an effective way to reduce site-specific noise from an ensemble of boreholes. Each inversion scheme gives comparable results indicating locally variable warming on the order of 1°C starting between 1800 and 1900 AD. Similarly surface air temperature records from 12 nearby meteorological stations exhibit locally variable warming also on the order of 1°C of warming during the 20th century. To explore the degree to which borehole temperatures and surface air temperature (SAT) time series are responding to the same signal, we average the SAT data into the same three groups and used these averages as a forcing function at the Earth's surface to generate synthetic transient temperature profiles. Root mean square (RMS) misfits between these synthetic temperature profiles and averaged temperature–depth profiles are low, suggesting that first-order curvature in borehole temperatures and variations in SAT records are correlated.     

Photospheric limb-darkening signatures of global structure variations

Observations of short-term irradiance variations and consideration of mechanisms of the solar activity cycle suggest the possibility of long-term variation of the solar flux. Since the limb darkening is sensitive to effective temperature and convective efficiency, observations of the solar limb darkening may provide a useful means to detect and study long-term global variations. The limb-darkening responses to impulsive variation (in depth) of the source function, to effective temperature variation, and to convection variations are presented. For the variations considered, the limb-darkening variation is approximately linearly proportional to the associated parameters. The minimum detectable amplitude of those parametric variations is derived as a function of observational noise. Given our demonstrated errors of observation, single-parameter sensitivies are 3 K for effective temperature variation and 0.007 for local mixing-length variation for year to year changes at 99% confidence.