Atmospheric Thermal Radiation Research Articles

Three dimensional atmospheric entry simulation of a high altitude cometary dustball meteoroid

Aims. The break-up of a dustball meteoroid is investigated numerically based on fluid dynamics simulations of the meteoroid’s atmospheric entry flow. Both thermal and mechanical break-up mechanisms are implemented, in order to investigate dustball meteoroid disintegration. Methods. A three dimensional model of a dustball meteoroid composed of thousands of small spherical grains was used in the atmospheric entry flow simulation, performed with the direct simulation Monte Carlo (DSMC) method. The dynamics of each meteoroid grain were calculated by means of the discrete element method (DEM), which models contact dynamics between grains. By coupling DEM with DSMC, the dynamics of a dustball meteoroid were calculated during atmospheric entry. In addition, thermal computations were also carried out taking into account the incoming atmospheric heat flux, thermal radiation, and grain ablation. Thus, this methodology is able to compute mechanical as well as thermal dustball meteoroid disintegration. Results. To test this novel multi-physics simulation framework, a prototypical dustball meteoroid, namely a Draconid meteoroid, was simulated. Using typical material properties from the literature, the Draconid meteoroid was compressed due to aerodynamic forces to roughly half its size immediately after the start of the simulation at 200 km altitude. Later, aerodynamic-induced meteoroid rotation occured until the meteoroid disintegrated mechanically at 120 km altitude. The fact that the meteoroid disintegrated mechanically is directly related to the combination of material properties used in the simulation.

Space-based full chain multi-spectral imaging features accurate prediction and analysis for aircraft plume under sea/cloud background.

Building a wide-area, high-efficiency, and accurate detection technology for air targets has become a new challenge for the construction of space situational awareness. Firstly, based on the space-based optical detection requirements for aircraft plume, the method of integrated modeling for sea/cloud background radiation characteristics based on coupling of remote sensing data and physical model is proposed, which can effectively deduce the background radiation field distribution under any environmental conditions. Specifically, combined with meteorological satellite sensor data, such as cloud top temperature, cloud type and cloud top height, three-dimensional atmospheric transmittance and atmospheric path thermal radiation texture are generated for different cloud heights and cloud phase conditions. Then, a coupled sea/cloud bidirectional reflectance model matched to the sampling of space-based detectors is established. Further, the accurate prediction model for multi-spectral imaging features of aircraft plume is built by considering the space-based full imaging chains including the complex coupling of aircraft plume, sea/cloud background, environmental atmosphere, optical system, and imaging detector. Finally, combined with the diffraction effect of the optical system, the multi-spectral imaging features of the aircraft plume are simulated under various spectral bands, flying heights, sea/cloud backgrounds, and detection angles, and the detection performances are analyzed and discussed by using the signal-to-clutter ratio (SCR). Research results show that the detection capability in the narrow band of 2.65-2.90µm and 4.25-4.50µm is better than the wide band of 3-5µm. When the aircraft flying height is greater than 5km, the aircraft plume can be detected in both narrow bands. It is more reliable to use the multispectral joint-band to detect aircraft plume in different backgrounds.

Bidirectional reflectance characteristics of the sea surface based on midinfrared measured data

In order to establish a more realistic radiation model of the sea surface, the effects of solar radiation, sky radiation, and atmospheric thermal radiation on sea surface radiation are taken into consideration, on the basis of which the infrared radiative transfer equation of the sea surface is deduced in this paper. A method for calculating the bidirectional reflection characteristics of the sea surface based on measured data is proposed according to the projection imaging of beam propagation. Based on the measurements of sea surface temperature, incident sky radiation, incident solar radiation, and radiance of sea crests at different times, the radiative transfer equation is used to retrieve the bidirectional reflectance of a midwave infrared sea surface. Meanwhile, the results of the method mentioned above are compared with the calculated results of Cox-Munk, Mermelstein, Wu, and Beckmann bidirectional reflection characteristics models. Research shows that the bidirectional reflectance at the wave crest of a sea surface increases gradually, when the solar incident zenith angle changes from 56.39° to 76.02° as well as the direction of observation remaining constant (θr=80.0°; ϕr=73.0°). The reflection ability at the wave crest of the sea surface is strongest when the incident direction of the sun is close to the observation direction, which is in accordance with the law of reflection. The Cox-Munk model and Wu model are closer to our values when the solar incidence zenith angle is small (θi≤65.93°). On the other hand, the calculated values of the Mermelstein and Wu models are closer to the values in this paper when the solar incidence zenith angle is large (θi≤65.93°). In general, the error of the Beckmann model is a little greater than that of the other three models.

The Definition of the Optimal Energy-Efficient form of the Building

We consider the problem of finding a geometrical form of a body in a thermal radiation field, for which the thermal balance between the body and the surrounding air is minimal. The case of a point source of heat is investigated. To consider an analogous problem for buildings, one must know the value of incoming thermal energy to a unit square in relation to its orientation. We develop an application package in MATLAB that represents this relation in table form and takes into consideration the direct, diffuse, ground-reflected solar radiation and the thermal radiation of atmosphere.

Determining the Tropospheric Delay of a Radio Signal by the Radiometric Method

We present a method and algorithm for real-time determination of the tropospheric delay of a radio signal and the radiometric complex developed on their basis. The method is based on the measurement of the atmospheric thermal microwave radiation intensity at the frequencies ν 1 = 20.7 GHz, ν 2 = 32 GHz, and ν 3 = 56.7 GHz and solution of the corresponding inverse problem with respect to the atmospheric parameters (temperature, pressure, humidity, and water content) which completely determine the tropospheric delay of a radio signal. The method was experimentally tested by comparing the radio-signal delay series obtained by the radiometric method and the GLONASS/GPS data. The error of determining the wet component of the radio-signal delay was about 3 mm.

MWR: Microwave Radiometer for the Juno Mission to Jupiter

The Juno Microwave Radiometer (MWR) is a six-frequency scientific instrument designed and built to investigate the deep atmosphere of Jupiter. It is one of a suite of instruments on NASA’s New Frontiers Mission Juno launched to Jupiter on August 5, 2011. The focus of this paper is the description of the scientific objectives of the MWR investigation along with the experimental design, observational approach, and calibration that will achieve these objectives, based on the Juno mission plan up to Jupiter orbit insertion on July 4, 2016. With frequencies distributed approximately by octave from 600 MHz to 22 GHz, the MWR will sample the atmospheric thermal radiation from depths extending from the ammonia cloud region at around 1 bar to pressure levels as deep as 1000 bars. The primary scientific objectives of the MWR investigation are to determine the presently unknown dynamical properties of Jupiter’s subcloud atmosphere and to determine the global abundance of oxygen and nitrogen, present in the atmosphere as water and ammonia deep below their respective cloud decks. The MWR experiment is designed to measure both the thermal radiation from Jupiter and its emission-angle dependence at each frequency relative to the atmospheric local normal with high accuracy. The antennas at the four highest frequencies (21.9, 10.0, 5.2, and 2.6 GHz) have ∼12° beamwidths and will achieve a spatial resolution approaching 600 km near perijove. The antennas at the lowest frequencies (0.6 and 1.25 GHz) are constrained by physical size limitations and have 20° beamwidths, enabling a spatial resolution of as high as 1000 km to be obtained. The MWR will obtain Jupiter’s brightness temperature and its emission-angle dependence at each point along the subspacecraft track, over angles up to 60° from the normal over most latitudes, during at least six perijove passes after orbit insertion. The emission-angle dependence will be obtained for all frequencies to an accuracy of better than one part in 10^3, sufficient to detect small variations in atmospheric temperature and absorber concentration profiles that distinguish dynamical and compositional properties of the deep Jovian atmosphere.

Nanophotonics-enabled smart windows, buildings and wearables

AbstractDesign and production of spectrally smart windows, walls, roofs and fabrics has a long history, which includes early examples of applied nanophotonics. Evolving nanoscience has a special role to play as it provides the means to improve the functionality of these everyday materials. Improvement in the quality of human experience in any location at any time of year is the goal. Energy savings, thermal and visual comfort indoors and outdoors, visual experience, air quality and better health are all made possible by materials, whose “smartness” is aimed at designed responses to environmental energy flows. The spectral and angle of incidence responses of these nanomaterials must thus take account of the spectral and directional aspects of solar energy and of atmospheric thermal radiation plus the visible and color sensitivity of the human eye. The structures required may use resonant absorption, multilayer stacks, optical anisotropy and scattering to achieve their functionality. These structures are, in turn, constructed out of particles, columns, ultrathin layers, voids, wires, pure and doped oxides, metals, polymers or transparent conductors (TCs). The need to cater for wavelengths stretching from 0.3 to 35 μm including ultraviolet-visible, near-infrared (IR) and thermal or Planck radiation, with a spectrally and directionally complex atmosphere, and both being dynamic, means that hierarchical and graded nanostructures often feature. Nature has evolved to deal with the same energy flows, so biomimicry is sometimes a useful guide.

Atmospheric thermal radiation – from historical measurements to investigations of the Earth's greenhouse effect

Atmospheric thermal radiation – from historical measurements to investigations of the Earth's greenhouse effect

Modification of the IR sky temperature under different atmospheric conditions in an arid region in central Saudi Arabia: Experimental and theoretical justification

Sky temperatures that were estimated from a single‐channel IR detector over Riyadh, Saudi Arabia, were analyzed from June 2008 to May 2011. The data were divided into three main categories: clear sky, cloudy sky, and dusty conditions. The observation and the research results were as follows. During periods of clear‐sky conditions, it was found that the sky temperatures depend mainly on the atmospheric water content, the screen level temperature, and the suspended aerosol particles in the atmosphere. Under cloudy conditions, the sky temperature ranges between −37°C and 5°C. The mean sky temperatures in this case are higher than those of the clear‐sky conditions by approximately 11°C to 18°C. The radiative properties of cloudy skies depend on the cloud characteristics and the intervening atmosphere between the ground and the cloud base. The sky temperature during dusty conditions ranged between −20°C and 8.5°C. The study showed that dusty conditions increase the atmospheric temperatures by approximately 17°C to 31°C. The sky temperatures during dusty periods are affected by several factors, such as the air mass properties, which bring the dust, and the dust particle characteristics, such as size, shape, and chemical composition, which are initially determined by the sources from which the dust originated. Theoretical simulations using MODTRAN software were used to investigate the atmospheric thermal radiation spectral distributions in the three categories. The results show that the major changes occurred within the atmospheric window (8–14μm).

An atmospheric radiation model for Cerro Paranal

The Earth's atmosphere affects ground-based astronomical observations. Scattering, absorption, and radiation processes deteriorate the signal-to-noise ratio of the data received. For scheduling astronomical observations it is, therefore, important to accurately estimate the wavelength-dependent effect of the Earth's atmosphere on the observed flux. In order to increase the accuracy of the exposure time calculator of the European Southern Observatory's (ESO) Very Large Telescope (VLT) at Cerro Paranal, an atmospheric model was developed as part of the Austrian ESO In-Kind contribution. It includes all relevant components, such as scattered moonlight, scattered starlight, zodiacal light, atmospheric thermal radiation and absorption, and non-thermal airglow emission. This paper focuses on atmospheric scattering processes that mostly affect the blue (< 0.55 mum) wavelength regime, and airglow emission lines and continuum that dominate the red (> 0.55 mum) wavelength regime. While the former is mainly investigated by means of radiative transfer models, the intensity and variability of the latter is studied with a sample of 1186 VLT FORS1 spectra. For a set of parameters such as the object altitude angle, Moon-object angular distance, ecliptic latitude, bimonthly period, and solar radio flux, our model predicts atmospheric radiation and transmission at a requested resolution. A comparison of our model with the FORS1 spectra and photometric data for the night-sky brightness from the literature, suggest a model accuracy of about 20%. This is a significant improvement with respect to existing predictive atmospheric models for astronomical exposure time calculators.

Gravitation and Gas Laws: An Alternative Approach to Climatology

The “natural greenhouse effect” is one of the fundamentals of traditional climatology. To maintain the outgoing thermal radiation from the Earth's surface in equilibrium with solar irradiation requires the mathematical construct of back-radiation emitted by some infrared-active constituents in the atmosphere; otherwise, the convection and evapotranspiration flows from the surface and the corresponding back flows cannot be explained in view of the net radiation budget. To surmount the biased view of all-dominating radiative processes in the atmosphere, an alternative approach should take into account the effects of gravity on the atmosphere. An atmospheric temperature effect is completely determined by the mean global temperature at the surface, the radiative-equilibrium temperature of the earth/atmosphere system (in an altitude of some kilometres) and the pseudoadiabatic temperature lapse rate. There is no separate conservation law for radiation at the Earth's surface but only one for energy. In the unequal competition with atmospheric thermal radiation, solar radiation has an unique position relating to the transformation into heat in the absorbing material.

Oxygen and carbon isotope ratios in the martian atmosphere

Oxygen and carbon isotope ratios in the martian CO 2 are key values to study evolution of volatiles on Mars. The major problems in spectroscopic determinations of these ratios on Mars are uncertainties associated with: (1) equivalent widths of the observed absorption lines, (2) line strengths in spectroscopic databases, and (3) thermal structure of the martian atmosphere during the observation. We have made special efforts to reduce all these uncertainties. We observed Mars using the Fourier Transform Spectrometer at the Canada–France–Hawaii Telescope. While the oxygen and carbon isotope ratios on Mars were byproducts in the previous observations, our observation was specifically aimed at these isotope ratios. We covered a range of 6022 to 6308 cm −1 with the highest resolving power of ν / δ ν = 3.5 × 10 5 and a signal-to-noise ratio of 180 in the middle of the spectrum. The chosen spectral range involves 475 lines of the main isotope, 184 lines of 13CO 2, 181 lines of CO 18O, and 119 lines of CO 17O. (Lines with strengths exceeding 10 −27 cm at 218 K are considered here.) Due to the high spectral resolution, most of the lines are not blended. Uncertainties of retrieved isotope abundances are in inverse proportion to resolving power, signal-to-noise ratio, and square root of the number of lines. Laboratory studies of the CO 2 isotope spectra in the range of our observation achieved an accuracy of ∼ 1 % in the line strengths. Detailed observations of temperature profiles using MGS/TES and data on temperature variations with local time from two GCMs are used to simulate each absorption line at various heights in each part of the instrument field of view and then sum up the results. Thermal radiation of Mars' surface and atmosphere is negligible in the chosen spectral range, and this reduces errors associated with uncertainties in the thermal structure on Mars. Using a combination of all these factors, the highest accuracy has been achieved in measuring the CO 2 isotope ratios: 13C/ 12C = 0.978 ± 0.020 and 18O/ 16O = 1.018 ± 0.018 times the terrestrial standards. Heavy isotopes in the atmosphere are enriched by nonthermal escape and sputtering, and depleted by fractionation with solid-phase reservoirs. The retrieved ratios show that isotope fractionation between CO 2 and oxygen and carbon reservoirs in the solid phase is almost balanced by nonthermal escape and sputtering of O and C from Mars.

Longwave Infrared Camera onboard the Venus Climate Orbiter

The Longwave Infrared Camera (LIR) onboard the first Japanese Venus mission, PLANET-C, or the Venus Climate Orbiter, operates in the middle infrared region with a single bandpass filter of 8–12 μm, measuring thermal radiation emitted from the cloud tops of the Venusian atmosphere. A horizontal wind vector field at the cloud-top height will be retrieved by means of a cloud tracking method. In addition, absolute temperature will be determined with an accuracy of 3 K. Since solar irradiation scattered by the atmosphere is much weaker than the atmospheric thermal radiation, LIR can continuously monitor a hemispheric wind field independent of the local time of the apocenter throughout the mission life. Wind and temperature fields obtained by LIR will provide key parameters to solve climatological issues related to the Venusian atmosphere. The use of an uncooled micro-bolometer array (UMBA), which requires no cryogenic apparatus, as an image sensor contributes to the reduction of power consumption and the weight of the LIR imager. An instrumental field-of-view of 12° is equal to the angle subtended by Venus when observed from a height of 9.5 Rv. The pixel field-of-view corresponds to a spatial resolution of 70 km viewed from the apocenter. A mechanical shutter functions not only as an optical shutter but also as a reference blackbody. The temperature stability of the sensor is especially important, because fluctuation of thermal radiation from the internal environment of the sensor itself causes background noise. Therefore, the temperature of the UMBA package is stabilized at 313 ± 0.1 K with a feedback controlled Peltier cooler/heater, and a NETD of 0.3 K, which is required for this infrared imager, will be achieved. Flat field images are taken with the shutter closed several seconds before and after 1 s exposure for a Venus thermal image. After a Venus image is taken, the LIR imager takes a cold calibration image of deep space. This measurement sequence is repeated every two hours when the spacecraft is orbiting at apocenter. Image data are transmitted down to the Earth after onboard calibration and data compression by common digital electronics.

Polarization of Thermal Microwave Atmospheric Radiation Due to Scattering by Ice Particles in Clouds

The polarization difference DTb between the vertical and horizontal components of thermal radiation emitted by clouds was studied using 37- and 85-GHz radiometers. The measurements were conducted during the Alliance Icing Research Project in Ottawa, Canada, during the winter of 1999/2000. Polarization differences ( DTb) greater than 0.1 K were observed in approximately 30% of the cloudy periods. Characteristic values of the polarization difference at 85 GHz were about 2 K with a maximum value of about 4.5 K. Polarization difference at 37 GHz usually did not exceed 2.5 K and was typically 2‐6 times less than that at 85 GHz. Both positive and negative polarization differences were observed. It is suggested that the microwave polarization results from scattering of atmospheric thermal radiation by cloud ice particles. The observations were interpreted with a model of radiative transfer in mixed-phase clouds. The characteristic polarization difference observed during groundbased measurements was found to agree with predictions of the radiative transfer model for typical values of cloud liquid and ice water content.

Long-term changes in net radiation and its components above a pine forest and a grass surface in Germany

Long-term measurements (1974–1993 and 1996, respectively) of the net radiation (Q), global radiation (G), reflected global radiation (R), long-wave atmospheric radiation (A) and thermal radiation (E) of a pine forest in Southern Germany (index p) and of a grass surface in Northern Germany (index g) are compared. The influence of changes in surface properties is discussed. There are, in the case of the pine stand, forest growth and forest management and in the case of the grass surface, the shifting of the site from a climatic garden to a horizontal roof. Both series of radiant fluxes are analyzed with respect to the influences of the weather (cloudiness, heat advection). To eliminate the different influence of the solar radiation of the two sites, it is necessary to normalize by means of the global radiation G, yielding the radiation efficiency Q/G, the albedo R/G=α and the normalized long-wave net radiation (A+E)/G. Furthermore, the long-term mean values and the long-term trend of yearly mean values are discussed and, moreover, a comparison is made of individual monthly values. Qp is twice as large as Qg. The reason for this is the higher values of G and A above the pine forest and half values of αp compared to αg. Ep is only a little greater than Eg. The time series of the radiation fluxes show the following trends: Qp declines continuously despite a slight increase of Gp. This is mainly due to the long-wave radiation fluxes. The net radiation of the grass surface Qg shows noticeably lower values after the merging of the site. This phenomenon is also dominated by the long-wave radiation processes. Although the properties of both site surfaces alter, Ep and Eg remain relatively stable. Ap and Ag show a remarkable decrease however. The reason for this is to be found in a modification of the heat advection, showing a more pronounced impact on the more continentally exposed site (pine forest). Compared to αg, αp shows only a small variability. The changes of αp can be easily explained as resulting from the influence on the albedo of alterations in cloudiness and the changes in the water storage in stand and soil produced by varying weather conditions. The influence of the forest management is only small and short-termed. αg reacted with a leap on site merging, followed by a continuous drop. The drop of the grass surface albedo αg on top of the observatory is probably related to the gradual development of the newly sown lawn there and the resultant change in the specific hydrological balance of the soil. A decreasing radiation efficiency Q/G at both sites is observed, which is principally due to an increase in −(A+E)/G. The investigation discovered changes in the long-wave radiation processes. Its influence in Q should lead to more attention to the long-wave radiation processes in routine monitoring of radiation. Copyright © 1999 Royal Meteorological Society

The estimation of thermal atmospheric radiation under cloudy conditions

AbstractAmong the surface radiation budget components that are needed to understand the climate of the Earth, the thermal atmospheric radiation component is the only one that is not measured routinely, so it must be estimated indirectly. The presence of clouds substantially hampers this task, supplementing the emission of water vapour and carbon dioxide in the lower atmosphere. The methods proposed to estimate thermal atmospheric radiation often rely on a cloudless sky model and a corrective term that takes into account the cloud contribution. Several models for estimating the thermal atmospheric radiation under cloudy conditions have been tested using measurements recorded in Granada (Spain) during a period of 2 years. The cloudless sky model provides estimation with an error of about 5 per cent, whereas the cloudy skies models, after some modifications, estimate thermal atmospheric radiation with an error of about 6 per cent. Our results show the convenience of a quadratic dependence on cloud amount for cloudy skies models. In addition to this, it seems convenient to use available information about the radiative properties of clouds to assign different cloud emittances for different types of clouds within each level, especially for middle level clouds.

A toy model linking atmospheric thermal radiation and sea ice growth

A highly simplified analytical model of sea ice growth is presented in which the atmosphere is in thermal radiative equilibrium with the ice. This makes the downwelling longwave radiation reaching the ice surface an internal variable rather than a specified forcing. The ice is characterized by only two variables, thickness and surface temperature. The seasonal cycle is resolved into four steps, in which either the thickness or the temperature can vary. An ocean mixed layer of fixed depth but variable temperature provides a heat sink if the ice melts away during the summer. Analytical results show how the ice state depends on properties of the ice and on the externally specified climate. The main result is that this bare bones physics is enough to produce an annual cycle of temperature and thickness not unlike today's conditions. The results also suggest how much the climate must change to produce qualitatively different cycles. Reducing the atmospheric poleward heat transport by 20 W m−2 is enough to make the ice so thick (&gt;12 m) that it never warms up to the melting point in summer. Increasing the poleward flux by 30 W m−2 is enough to produce an arctic ocean which stores enough heat in summer to prevent any ice forming in winter. The model predicts that today's climate can support either a perennial ice pack or an ice free Arctic. However, a winter ice pack which melts completely each summer is not possible under any climate.

Some results of thermal atmospheric radiation measurements in Manresa (Spain)

Thermal atmosphericr adiation measurements have been carried out in Manresa, atown 60 km away from Barcelona. Computations of the correlations with the most common used equations for long-wave radiation are performed. Brutsaert and Idso equations show the best fitting with experimental data. A new equation is proposed, with almost the same properties than Idso-Jackson's obtaining a better correlation coefficient.

On calculating thermal radiation from cloudless skies

Several recent empirical findings and theoretical developments related to the estimation of clear-sky atmospheric thermal radiation are discussed. It is demonstrated that the radiative behavior of water vapor at air temperatures above freezing has been parameterized as well as can or need be done, but that there may be room for some improvement at air temperatures below freezing. It is additionally shown that any procedure designed to accurately calculate atmospheric thermal radiation must be able to handle effects of airborne dust variability of both a temporal and spatial nature.

On the Systematic Nature of Diurnal Patterns of Differences Between Calculations and Measurements of Clear Sky Atmospheric Thermal Radiation

On the Systematic Nature of Diurnal Patterns of Differences Between Calculations and Measurements of Clear Sky Atmospheric Thermal Radiation