Altitude Dependence Research Articles

A critical fluid in the Earth’s gravity field

This work proposes a mechanism for the physical processes underlying the wide practical application of the unique properties of a substance in a critical state—critical fluid (CF)—in contemporary technologies. According to the fluctuation theory of phase transitions (FTPT), this mechanism may be due to the fluctuation and structural characteristics of a critical fluid, which determine its equilibrium and kinetic properties. Among such characteristics are the system correlation radius Rs, the number of order parameter fluctuations Nf ~ Rs-3 per mole of critical fluid, and the fluctuation component of the thermodynamic potential F*f = NfkTc/(PcVc) = C0Rs-3. These structural characteristics are studied with the use of experimental gravity effect data, such as the altitude and temperature dependencies of the scattered light intensity I(z, t) in a heterogeneous substance (n-pentane) near the critical vaporization temperature. Using these results and the literature data on the formation of Al2O3 nanoparticles with the use of SC-H2O, the propagation velocity of substance molecules vf ≈ 106 cm/s is estimated for the origination and decay of order parameter fluctuations. It has been concluded that just such high propagation velocities of substance molecules most likely cause the unique properties of a critical fluid during their practical application in a number of engineering processes.

Simultaneous observations of F2 layer stratification and spread F at postmidnight over a northern equatorial anomaly region

AbstractSimultaneous observations of F2 layer stratification and spread F at postmidnight (00:00 LT to 05:00 LT) were carried out on 22, 23, and 28 November 2013, using ionosondes distributed over a northern equatorial anomaly region at three specific locations, i.e., Puer (PUR, 22.7°N, 101.05°E, dip latitude 12.9°N), Chiang Mai (CMU, 18.8°N, 98.9°E, dip latitude 9.04°N), and Chumphon (CPN, 10.7°N, 99.4°E, dip latitude 0.93°N). The results show that both the PUR and CMU stations observed the F2 layer stratification at postmidnight in the Northern Hemisphere, frequently accompanied with gravity waves (the periods~30–100 min). It is reported that F2 layer stratification at postmidnight can be observed in the Northern Hemisphere for the first time. It is suggested that the thermospheric neutral wind triggered by gravity waves strongly contribute to the altitude dependence of the combined vertical plasma velocity, which consequently poses significant impacts on the occurrence of the low‐latitude F2 layer stratification at postmidnight. In addition, the spread F other than F2 layer stratification was observed at the CPN station located at the geomagnetic equator, suggesting that smaller geomagnetic inclination tend to inhibit the postmidnight F2 layer stratification in the equatorial region. Furthermore, on 23 November 2013 a good correlation was identified between the F2 layer stratification at PUR and the spread F at both CMU and CPN, possibly due to that the large‐scale gravity waves originating at middle latitudes contribute to the nighttime spread F observed in the low‐latitude and equatorial regions.

Altitude dependence of nightside Martian suprathermal electron depletions as revealed by MAVEN observations

AbstractThe MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft is providing new detailed observations of the Martian ionosphere thanks to its unique orbital coverage and instrument suite. During most periapsis passages on the nightside ionosphere suprathermal electron depletions were detected. A simple criterion was implemented to identify the 1742 depletions observed from 16 November 2014 to 28 February 2015. A statistical analysis reveals that the main ion and electron populations within the depletions are surprisingly constant in time and altitude. Absorption by CO2 is the main loss process for suprathermal electrons, and electrons that strongly peaked around 6 eV are resulting from this interaction. The observation of depletions appears however highly dependent on altitude. Depletions are mainly located above strong crustal magnetic sources above 170 km, whereas the depletions observed for the first time below 170 km are globally scattered onto the Martian surface with no particular dependence on crustal fields.

Effect of aerosol vertical distribution on aerosol-radiation interaction: A theoretical prospect.

This study presents a theoretical investigation of the effect of the aerosol vertical distribution on the aerosol radiative effect (ARE). Four aerosol composition models (dust, polluted dust, pollution and pure scattering aerosols) with varying aerosol vertical profiles are incorporated into a radiative transfer model. The simulations show interesting spectral dependence of the ARE on the aerosol layer height. ARE increases with the aerosol layer height in the ultraviolet (UV: 0.25–0.42 μm) and thermal-infrared (TH-IR: 4.0–20.0 μm) regions, whereas it decreases in the visible-near infrared (VIS-NIR: 0.42–4.0 μm) region. Changes in the ARE with aerosol layer height are associated with different dominant processes for each spectral region. The combination of molecular (Rayleigh) scattering and aerosol absorption is the key process in the UV region, whereas aerosol (Mie) scattering and atmospheric gaseous absorption are key players in the VIS-NIR region. The longwave emission fluxes are controlled by the environmental temperature at the aerosol layer level. ARE shows maximum sensitivity to the aerosol layer height in the TH-IR region, followed by the UV and VIS-NIR regions. These changes are significant even in relatively low aerosol loading cases (aerosol optical depth ∼0.2–0.3). Dust aerosols are the most sensitive to altitude followed by polluted dust and pollution in all three different wavelength regions. Differences in the sensitivity of the aerosol type are explained by the relative strength of their spectral absorption/scattering properties. The role of surface reflectivity on the overall altitude dependency is shown to be important in the VIS-NIR and UV regions, whereas it is insensitive in the TH-IR region. Our results indicate that the vertical distribution of water vapor with respect to the aerosol layer is an important factor in the ARE estimations. Therefore, improved estimations of the water vapor profiles are needed for the further reduction in uncertainties associated with the ARE estimation.

Methodologies to obtain aerosol property profiles from three-wavelength elastic lidar signals

The Lidar/Radiometer Inversion Code (LIRIC) and the Constrained Iterative Inversion (CII) procedure combined with a graphical aerosol classification framework (GF) have been used to analyse their ability in characterizing the altitude dependence of aerosol properties and evaluate their benefits and weaknesses. LIRIC and the CII technique rely on elastic lidar signals at 355, 532, and 1064 nm and collocated Aerosol Robotic Network (AERONET) Sun/sky photometer measurements to retrieve aerosol parameter profiles at the lidar wavelengths. The aerosol GF relies on the combined analysis of the Ångström exponent at the wavelength pairs 355 and 1064 nm (A(355, 1064)) and its spectral curvature (ΔA = A(355, 532) – A(532, 1064)) to estimate the fine-modal radius and the 532 nm fine-mode fraction. The application of the LIRIC and CII-GF techniques to three selected case studies representative of Central Mediterranean aerosol scenarios has revealed that the differences between the aerosol products from LIRIC and the corresponding ones from the CII-GF procedure varied with altitude, increased with the lidar wavelength decrease, and were significantly large when aerosol from different sources and/or from different advection routes was located at the altitudes sounded by the lidar. The plot on the aerosol GF of A(355, 1064) versus the spectral curvature has indicated that the LIRIC constraint that the fine-modal radius is height independent may represent a weakness if aerosol types and hence aerosol size distributions vary with altitude. The use of lidar ratios (LRs) constant with altitude could represent one of the main weaknesses of the CII-GF technique. The combined use of both techniques should allow obtaining a better characterization of the altitude dependence of aerosol properties from three-wavelength elastic lidar signals.

Results of the Ion–Neutral Collision Frequency Measurements in the Lower Thermosphere by the Method of Resonance Scattering of the Radio Waves by Artificial Periodic Irregularities

UDC 550.388.2+551.510.536 We present for the first time the experimental data on the frequency of ion–neutral collisions at the altitudes of the ionospheric E layer, which were obtained by the method of resonance scattering of the radio waves by artificial periodic irregularities of the ionospheric plasma. The measurements were carried out in different time periods from 1990 to 2012. Time and altitude dependences of the collision frequency are given. The dependence of the collision frequency on the solar and geomagnetic activity has been analyzed. Collisions of electrons and ions with atoms and molecules play an important role in physics of the ionosphere and atmosphere. In particular, they determine the friction force and should be taken into account in the equations of motion of a medium when its viscosity increases. The frequency of ion–neutral collisions affects the energy and momentum transfer processes [1–4]. When propagation of internal gravity waves above 100 km is considered, it is needed to allow for dissipation due to increasing viscosity of the medium [4–7], which is directly related to collisions. The frequency νin of collisions between ions and neutral molecules should also be taken into account when the low-frequency processes associated with the plasma conductivity are analyzed (see, e. g., [8]). However, the experimental data on νin are fairly scarce. Meanwhile, considerable variations in the ion–neutral collision frequency can be observed in the upper ionosphere. These variations are due most frequently to the neutral atmosphere density variations caused by the transmission of internal gravity and tidal waves. Variations from day to day can be due to propagation of planetary waves. At the altitudes of the upper mesosphere and lower thermosphere, the neutral atmosphere density variations according to the lidar data can exceed 20%, while the temperature variations can reach 70 K [9, 10]. Observations suggest that during propagation of gravity waves the collision frequency can be changed by a factor of 1.5–2 for half an hour [9, 11]. The collision frequency variations can also be a consequence of variations in the composition of both the ion component and the neutral atoms and molecules. In particular, in the ionospheric E region, variations in the ion–neutral collision frequency can be caused by the penetration of metal meteor particles and ions that contribute to the formation of both the sporadic layers of the electron density and the layer with increased content of Na, K, Fe, etc. atoms [12–15]. In this paper, we present the results of determining the ion–molecule collision frequency obtained by the method of resonant scattering of radio waves by artificial periodic irregularities of the plasma at the altitudes of the ionospheric E region.

A simple formulation of the CH<sub>2</sub>O photolysis quantum yields

Abstract. New expressions for the wavelength-dependent photolysis quantum yields of CH2O, Φj, are presented. They are based on combinations of functions of the type Ai/(1+exp[−(1/λ − 1/λ0i)/bi]). The parameters Ai, bi, and λ0i which have a physical meaning, are obtained by fits to the measured Φj data available from literature. The altitude dependence of the photolysis frequencies resulting from the new quantum yield expressions are compared to those derived from the Φj recommended by JPL and IUPAC.

Altitude and solar activity dependence of 1967–2005 thermospheric density trends derived from orbital drag

AbstractWe examine 1967–2005 thermospheric mass density trends (as well as 1967–2013 trends) derived from satellite orbit data, as a function of altitude, solar flux, and geomagnetic activity. At 400 km altitude, the estimated 1967–2005 trend is −2.0 ± 0.5% per decade. The estimated trends become increasingly negative with increasing height between 250 and 575 km, suggesting an exospheric temperature trend of −1 to −2 K per decade, which is much smaller than temperature trends that have been inferred from ground‐based incoherent scatter radar measurements. The orbit‐derived trend height profiles are in good agreement with model simulations of the enhanced cooling that results from increasing concentration of CO2 in the mesosphere and lower thermosphere. In contrast to earlier results, the solar flux dependence of the estimated trends is weak, relative to the trend uncertainty. There is some indication that the trends may be stronger during very low geomagnetic activity conditions. Estimation of the solar flux and geomagnetic activity dependence of the trends is complicated by monotonic decreases in these drivers over the past four solar minima together with the CO2 increase, all of which drive interminima decreases in density.

Long-term midlatitude mesopause region temperature trend deduced from quarter century (1990–2014) Na lidar observations

Abstract. The long-term midlatitude temperature trend between 85 and 105 km is deduced from 25 years (March 1990–December 2014) of Na Lidar observations. With a strong warming episode in the 1990s, the time series was least-square fitted to an 11-parameter nonlinear function. This yields a cooling trend starting from an insignificant value of 0.64 ± 0.99 K decade−1 at 85 km, increasing to a maximum of 2.8 ± 0.58 K decade−1 between 91 and 93 km, and then decreasing to a warming trend above 103 km. The geographic altitude dependence of the trend is in general agreement with model predictions. To shed light on the nature of the warming episode, we show that the recently reported prolonged global surface temperature cooling after the Mt Pinatubo eruption can also be very well represented by the same response function.

Evaluation of radar precipitation estimates near gap regions: a case study in the Colorado River basin

Radar precipitation estimation is very useful for hydrological and climatological studies. However, radar precipitation has inherent difficulty in estimating precipitation in mountainous regions. In developed countries such as the United States where there are extensive precipitation radar networks, gaps in the radar precipitation field are usually due to radar beam blockage by mountains. The goal of this study is to evaluate the performance of a daily radar precipitation field (Stage-II) against rain gauge measurements near radar gap areas in the Colorado River basin of the United States (southwestern Colorado, southeastern Utah, northeastern Arizona and northwestern New Mexico). We evaluated daily precipitation data for the years spanning from 2007 to 2009. Statistical score skills including correlation and bias are used for evaluation. Compared to gauge measurements, Stage-II fails to capture the altitude dependence of precipitation in the region. Bias analysis shows that Stage-II underestimates precipitation at higher elevation. Seasonal evaluations of Stage-II indicate that it underestimates cold season precipitation in the study area. Overall, the results show that the error in Stage-II precipitation estimates made within 100 km from the gap area, as measured against rain gauge measurements, is considerable, and caution is warranted for its use in hydrological and water management applications.

Fifth-Power Altitude Dependence of Particle Precipitation at The Minimum Geomagnetic Field Position

Fifth-Power Altitude Dependence of Particle Precipitation at The Minimum Geomagnetic Field Position

Radiation survey in the International Space Station

The project ALTEA-shield/survey is part of an European Space Agency (ESA) – ILSRA (International Life Science Research Announcement) program and provides a detailed study of the International Space Station (ISS) (USLab and partly Columbus) radiation environment. The experiment spans over 2 years, from September 20, 2010 to September 30, 2012, for a total of about 1.5 years of effective measurements. The ALTEA detector system measures all heavy ions above helium and, to a limited extent, hydrogen and helium (respectively, in 25 Mev–45 MeV and 25 MeV/n–250 MeV/n energy windows) while tracking every individual particle. It measures independently the radiation along the three ISS coordinate axes. The data presented consist of flux, dose, and dose equivalent over the time of investigation, at the different surveyed locations. Data are selected from the different geographic regions (low and high latitudes and South Atlantic Anomaly, SAA). Even with a limited acceptance window for the proton contribution, the flux/dose/dose equivalent results as well as the radiation spectra provide information on how the radiation risks change in the different surveyed sites. The large changes in radiation environment found among the measured sites, due to the different shield/mass distribution, require a detailed Computer-Aided Design (CAD) model to be used together with these measurements for the validation of radiation models in space habitats. Altitude also affects measured radiation, especially in the SAA. In the period of measurements, the altitude (averaged over each minute) ranged from 339 km to 447 km. Measurements show the significant shielding effect of the ISS truss, responsible for a consistent amount of reduction in dose equivalent (and so in radiation quality). Measured Galactic Cosmic Ray (GCR) dose rates at high latitude range from 0.354 ± 0.002 nGy/s to 0.770 ± 0.006 nGy/s while dose equivalent from 1.21 ± 0.04 nSv/s to 6.05 ± 0.09 nSv/s. The radiation variation over the SAA is studied. Even with the reduced proton sensitivity, the high day-by-day variability, as well as the strong altitude dependence is clearly observed. The ability of filtering out this contribution from the data is presented as a tool to construct a radiation data set well mimicking deep space radiation, useful for model validations and improvements.

Exoplanet atmosphere. Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy.

Exoplanets that orbit close to their host stars are much more highly irradiated than their solar system counterparts. Understanding the thermal structures and appearances of these planets requires investigating how their atmospheres respond to such extreme stellar forcing. We present spectroscopic thermal emission measurements as a function of orbital phase ("phase-curve observations") for the highly irradiated exoplanet WASP-43b spanning three full planet rotations using the Hubble Space Telescope. With these data, we construct a map of the planet's atmospheric thermal structure, from which we find large day-night temperature variations at all measured altitudes and a monotonically decreasing temperature with pressure at all longitudes. We also derive a Bond albedo of 0.18(-0.12)(+0.07) and an altitude dependence in the hot-spot offset relative to the substellar point.

Altitude and Latitude Distribution of the Production Rate of 7Вe in the Earth’s Atmosphere in the PARMA Model

The contribution of spallation reactions on protons and neutrons to the production of the cosmogenic isotope 7Be is analyzed on the basis of calculations of a nuclear-electromagnetic cascade in the atmosphere in the analytical model PARMA, along with its latitude and altitude dependences. It is shown that the main contribution to 7Ве production comes from the reaction 14N7(n, X)7Be4. It is determined that 7Ве production increases as one approaches the poles. Results of the PARMA model are in overall agreement with earlier empirical and semi-empirical models.

Solar wind-driven geopotential height anomalies originate in the Antarctic lower troposphere

We use National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data to estimate the altitude and time lag dependence of the correlation between the interplanetary magnetic field component, By, and the geopotential height anomaly above Antarctica. The correlation is most statistically significant within the troposphere. The peak in the correlation occurs at greater time lags at the tropopause (∼6–8 days) and in the midtroposphere (∼4 days) than in the lower troposphere (∼1 day). This supports a mechanism involving the action of the global atmospheric electric circuit, modified by variations in the solar wind, on lower tropospheric clouds. The increase in time lag with increasing altitude is consistent with the upward propagation by conventional atmospheric processes of the solar wind-induced variability in the lower troposphere. This is in contrast to the downward propagation of atmospheric effects to the lower troposphere from the stratosphere due to solar variability-driven mechanisms involving ultraviolet radiation or energetic particle precipitation.

Polychlorinated dibenzo-p-dioxins and dibenzofurans and polychlorinated biphenyls in surface soil from the Tibetan Plateau

Concentrations of Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in soil samples from Tibetan Plateau were determined. The average concentration of total 2,3,7,8-PCDD/Fs was (2.30±1.02) pg/g, and World Health Organization Toxicity Equivalency (WHO-TEQ) average concentration was (0.013±0.010) pgWHO-TEQ/g. The average concentration of ∑PCBs (7 indicator PCB and 12 dioxin like-PCB congeners) was (16.2±9.25) pg/g, and WHO-TEQ average concentration was 0.043±0.049pgWHO-TEQ/g. Comparing to previous studies in similar environmental conditions, PCDD/Fs and PCBs in this study showed a relatively lower concentration. The altitude dependences of PCDD/Fs and PCBs were also studied. Total organic carbon (TOC) normalized concentrations presented a quadratic relation with the altitudes, and an inflection could be found on the parabola of the total concentrations and some congeners of high concentration. The concentrations decreased with altitudes below about 4500m above sea level (a.s.l.), while they increased with altitudes above it. These phenomena indicate that cold condensation of PCDD/Fs and PCBs would happen above 4500m a.s.l, on the Tibetan Plateau.

Energy, altitude, and mass dependence of steepness of the lateral distribution function of electrons and muons in extensive air showers

In the present work, the energy and mass dependence of the steepness of the lateral distribution function of electrons and muons (η) are investigated. Based on a CORSIKA simulation, different characteristics of η for proton, helium, oxygen, and iron primaries in the energy range 1014–1017eV are presented. It is found that η is a mass sensitive parameter, and its potential as a mass discrimination parameter between light and heavy primaries is studied. Moreover, the altitude dependence of η for KASCADE and Auger experiments (110 and 1400m) is discussed. It is shown that the Auger experiment is potentially more effective for applying this parameter as a mass discriminator between light and heavy cosmic ray components, especially at high energies.

Storm-time behaviors of O/N2 and NO variations

Algorithms have been developed to extract net nitric oxide (NO) radiances in the wavelength range of 172–182nm from the dayside TIMED/GUVI spectrograph data and convert them to NO column density (100–150km). The thermospheric O/N2 column density ratios (referenced from an altitude ~135km with a N2 column density of 1017cm−2) are also obtained from the spectrograph data. The spatial resolution of the NO and O/N2 products along the GUVI orbit is 240km. The coincident O/N2 ratio and NO column density maps during a few geomagnetic storms reveal two major features: (1) Storm-time O/N2 depletion and NO enhancement extend from high to mid and low latitudes. They are anti-correlated on a global scale, (2) the NO enhancement covers a wider longitude and latitude region than O/N2 depletion on a local scale. The similarity between O/N2 depletion and NO enhancement on global scale is due to storm-time equatorward meridional wind that brings both O/N2 depleted and NO enhanced air from high to low latitudes. The altitude dependence of the storm-time meridional wind, different peaks altitudes of the local O/N2 and NO variations, and long life time of NO (one day or longer) may explain the different behaviors of O/N2 and NO on a local scale.

Ozone photolysis: Strong isotopologue/isotopomer selectivity in the stratosphere

AbstractWe calculated the photolysis rate coefficients of five ozone isotopologues/isotopomers as functions of altitude up to 80 km using recent ab initio absorption cross sections and an averaged actinic flux. Three of the five ozone isotopologues/isotopomers are symmetric, with a single isotopic dissociation channel, and two are asymmetric with two isotopic dissociation channels. The specific contributions of the Chappuis, Huggins, and Hartley bands to the photolysis rates and enrichments have been determined as a function of altitude. The Chappuis and Hartley bands have a dominant contribution to the photolysis rates, respectively at low and high altitudes, but these two bands are characterized by small fractionations. In contrast, the Huggins band has a minor contribution to the overall photolysis rate at any altitude, but it generates most of the strong fractionation which peaks around 35 km. The photolysis fractionations are “mass dependent” in contrast with those due to the ozone formation process which are “non–mass dependent.” The altitude dependences of our photolysis fractionations are in qualitative agreement with those of Liang et al. (2006) but differ quantitatively, most notably because the contribution of the Huggins band has been reevaluated. The branching ratio between the two electronic dissociation channels (either O(3P) or O(1D) products) has been used to calculate the isotopic enrichments of the reactive O(1D) induced by ozone photolysis. The isotopic photolysis rates can be included in a global kinetic model that includes ozone formation processes and collision with O2 and other oxygen‐containing species.

Cosmic-ray neutron simulations and measurements in Taiwan

This study used simulations of galactic cosmic ray in the atmosphere to investigate the neutron background environment in Taiwan, emphasising its altitude dependence and spectrum variation near interfaces. The calculated results were analysed and compared with two measurements. The first measurement was a mobile neutron survey from sea level up to 3275 m in altitude conducted using a car-mounted high-sensitivity neutron detector. The second was a previous measured result focusing on the changes in neutron spectra near air/ground and air/water interfaces. The attenuation length of cosmic-ray neutrons in the lower atmosphere was estimated to be 163 g cm(-2) in Taiwan. Cosmic-ray neutron spectra vary with altitude and especially near interfaces. The determined spectra near the air/ground and air/water interfaces agree well with measurements for neutrons below 10 MeV. However, the high-energy portion of spectra was observed to be much higher than our previous estimation. Because high-energy neutrons contribute substantially to a dose evaluation, revising the annual sea-level effective dose from cosmic-ray neutrons at ground level in Taiwan to 35 μSv, which corresponds to a neutron flux of 5.30 × 10(-3) n cm(-2) s(-1), was suggested.