Altitude Dependence Research Articles

Mathematical Modeling the Biology of Single Nucleotide Polymorphisms (SNPs) in Whole Genome Adaptation

As a living information and communications system, the genome encodes patterns in single nucleotide polymorphisms (SNPs) reflecting human adaptation that optimizes population survival in differing environments. This paper mathematically models environmentally induced adaptive forces that quantify changes in the distribution of SNP frequencies between populations. We make direct connections between biophysical methods (e.g. minimizing genomic free energy) and concepts in population genetics. Our unbiased computer program scanned a large set of SNPs in the major histocompatibility complex region and flagged an altitude dependency on a SNP associated with response to oxygen deprivation. The statistical power of our double-blind approach is demonstrated in the flagging of mathematical functional correlations of SNP information-based potentials in multiple populations with specific environmental parameters. Furthermore, our approach provides insights for new discoveries on the biology of common variants. This paper demonstrates the power of biophysical modeling of population diversity for better understanding genome-environment interactions in biological phenomenon.

Behavioural tuning in a tropical amphibian along an altitudinal gradient.

Males of the coqui treefrog, Eleutherodactylus coqui, produce a distinct two-note 'co-qui' advertisement call from sunset to midnight throughout most of the year. Previous work established that both the spectrotemporal aspects of the call and the frequency of highest inner-ear sensitivity change with altitude above sea level. These variations are such that the frequency of the emitted co-note closely matches the frequency to which the inner ear is most sensitive. Given this parallel variation, we expected that the call-evoked behavioural response of male coqui treefrogs would also show an altitude dependence, and hypothesized that males would produce their most robust acoustical territorial response to advertisement calls that match calls from their own altitude. We tested this hypothesis in the field by studying the vocal response behaviour of coquis to playbacks of synthetic, altitude-dependent conspecific calls, and indeed found that the most robust vocal responses were obtained using stimuli closely matching the calls from the same altitude.

Dusty plasma near the surface of phobos

It has been shown that a dusty plasma is formed in the surface layer over the illuminated part of Mars’ satellite Phobos owing to photoelectric and electrostatic processes. The distribution functions of photoelectrons near its surface, altitude dependences of the density of dust particles, and their charges and sizes, as well as electric fields, have been determined within a physicomathematical model for the self-consistent description of densities of photoelectrons and dust particles over the surface of the illuminated part of Phobos. In view of a weak gravitational field, dust particles rising over the surface of Phobos are larger than those over the surface of the Moon. In this case, the role of adhesion, which is a significant process preventing the separation of dust particles from the lunar surface, is much smaller on Phobos.

Analysis of Precipitation Extremes in the Qinghai-Tibetan Plateau, China: Spatio-Temporal Characteristics and Topography Effects

Although precipitation extremes exert a major influence on populations and the environment, trend analysis for the entire Qinghai-Tibetan plateau (QTP) has not previously been undertaken. In this study, meteorological data from 83 weather stations was used to analyze the temporal trends and spatial distribution of 10 extreme precipitation indices over the QTP during 1975–2014. The Mann Kendall test and Sen’s slope estimator were used to determine significances and magnitudes of station trends. Spatially, stations recording increasing trends were mainly distributed in the southwestern, central and northern regions. Stations with decreasing trends were centered on the eastern and southeastern areas. Temporally, all indices had an increasing trend except for consecutive dry days (CDD) and consecutive wet days (CWD) during the study period. The contribution of extreme precipitation to total precipitation showed a significant increasing trend. These findings may be due to the complex interaction between the large-scale circulation and topography. In general, the changes of extreme precipitation indicated an enhanced tendency, with the frequency, intensity and amount of heavy precipitation increasing over time. Furthermore, altitude dependency of extreme precipitation does not exist in QTP, with topography effects on changes in precipitation extremes being more obvious in the higher elevation, flat, and hill stations.

Internal Gravity Waves in the Lower Thermosphere with Linear Temperature Profile: Theory and Experiment

The problem of internal gravity waves in a medium with linear altitude profile of equilibrium temperature as applied to the experiments related to the creation of artificial periodic irregularities and diagnostics of the neutral atmosphere at the altitudes of the E region is considered. A solution to the initial linearized system of equations for weak disturbances of the thermospheric parameters, such as pressure, density, temperature, and velocity of the medium, is obtained. Among a large array of experimental data on the temperature profiles of the neutral component, the sessions in which the altitude dependence of the equilibrium temperature was well approximated by a linear function were selected. The characteristics of internal gravity waves obtained for such a temperature profile are compared with the results of measuring the atmospheric parameters. Satisfactory agreement between the theoretical and experimental values of the quantities being determined is established, which confirms the validity of the chosen model.

Examination of Derived Gust Velocities from a Fleet of Aerial Supervision Module/Lead Aircraft

Flight data collected from a fleet of Beechcraft King Air airframes have been analyzed. The data consisted of information from 3094 flights in various missions flown for the U.S. Forest Service. The missions consisted of those in support of aerial firefighting as well as passenger and ferry operations. The 2 s rule for separation of gust and maneuver load factors has been examined and deemed adequate. Gust and maneuver loads spectra for ground–air–ground are shown to correlate better with altitude above ground than with altitude relative to mean sea level. The flights are separated into six specific phases, some of which are unique for firefighting missions. The incremental vertical gust loads are then used to find derived gust velocities for each flight phase and for the entire flight. The derived gust velocity spectra are shown to be independent of the flight phase and depend only on altitude. It is concluded that the development of such spectra for individual flight phases is unnecessary and that a single spectrum, showing altitude dependence, is equally applicable to all phases of flight.

Altitude dependence of electrohydrodynamic flow in an electrostatic lifter

Experiments carried out during the last 50 years have elucidated the basic mechanism of the Biefeld-Brown effect. Recent research has focused on establishing design rules in order to maximize the lifting force resulting from this effect. For this purpose, a numerical estimation that takes the effect of altitude into account is needed. In the present contribution, the thrust due to Biefeld-Brown effect was computed by simulating the corona-discharge-induced electrohydrodynamic flow in a widely used high-voltage asymmetric capacitor with the major goal to elucidate the dependence of thrust on the altitude, pressure, temperature and humidity, respectively. Our numerical results reproduced the experimentally observed decrease of thrust with altitude and shown that this is a consequence of various competing effects.

Cloud removing method for daily snow mapping over Central Asia and Xinjiang, China

Central Asia and Xinjiang, China are conjunct areas, located in the hinterland of the Eurasian continent, where the snowfall is an important water resource supplement form. The induced seasonal snow cover is vita factors to the regional energy and water balance, remote sensing plays a key role in the snow mapping filed, while the daily remote sensing products are normally contaminated by the occurrence of cloud, that obviously obstacles the utility of snow cover parameters. In this paper, based on the daily snow product from Moderate Resolution Imaging Spectroradiometer (MODIS A1), a cloud removing method was developed by considering the regional snow distribution characteristics with latitude and altitude dependence respectively. In the end, the daily cloud free products was compared with the same period of eight days MODIS standard product, revealing that the cloud free snow products are reasonable, while could provide higher temporal resolution, and more details over Center Asia and Xinjiang Province.

An upper-branch Brewer–Dobson circulation index for attribution of stratospheric variability and improved ozone and temperature trend analysis

Abstract. We find that wintertime temperature anomalies near 4 hPa and 50° N/S are related, through dynamics, to anomalies in ozone and temperature, particularly in the tropical stratosphere but also throughout the upper stratosphere and mesosphere. These mid-latitude anomalies occur on timescales of up to a month, and are related to changes in wave forcing. A change in the meridional Brewer–Dobson circulation extends from the middle stratosphere into the mesosphere and forms a temperature-change quadrupole from Equator to pole. We develop a dynamical index based on detrended, deseasonalised mid-latitude temperature. When employed in multiple linear regression, this index can account for up to 60 % of the total variability of temperature, peaking at ∼ 5 hPa and dropping to 0 at ∼ 50 and ∼ 0.5 hPa, respectively, and increasing again into the mesosphere. Ozone similarly sees up to an additional 50 % of variability accounted for, with a slightly higher maximum and strong altitude dependence, with zero improvement found at 10 hPa. Further, the uncertainty on all equatorial multiple-linear regression coefficients can be reduced by up to 35 and 20 % in temperature and ozone, respectively, and so this index is an important tool for quantifying current and future ozone recovery.

On improving the accuracy of electron density profiles obtained at high altitudes by the ionospheric sounder on the Mars Express spacecraft

AbstractWe attempt to improve the standard inversion routine used to obtain electron density profiles from the data measured by the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) topside radar sounder on board the Mars Express spacecraft. Artificial ionospheric traces corresponding to how the MARSIS instrument would see model electron density profiles are constructed, and they are inverted using the standard routine. Ideally, this should result in the original electron density profiles. However, it is found that discrepancies between the original and resulting electron density profiles may be significant, in particular at larger solar zenith angles and for higher spacecraft altitudes. This is due to a gap of MARSIS time delay measurements at low‐sounding frequencies, and a necessity to interpolate electron density profiles in this plasma frequency range. Although the ionospheric scale height likely increases with the altitude, the standard inversion routine uses an exponential interpolation with a constant scale height. We suggest a new inversion method, which takes into account expected shapes of ionospheric profiles in the interpolation region. We verify the performance of this method both on the model electron density profiles and on real MARSIS data. We demonstrate that it seems to perform considerably better than the standard routine, in particular for higher spacecraft altitudes. Finally, we use the new inversion method to obtain a revised dependence of the peak altitude on the solar zenith angle.

A new parameterization of the UV irradiance altitude dependence for clear-sky conditions and its application in the on-line UV tool over Northern Eurasia

Abstract. A new method for calculating the altitude UV dependence is proposed for different types of biologically active UV radiation (erythemally weighted, vitamin-D-weighted and cataract-weighted types). We show that for the specified groups of parameters the altitude UV amplification (AUV) can be presented as a composite of independent contributions of UV amplification from different factors within a wide range of their changes with mean uncertainty of 1 % and standard deviation of 3 % compared with the exact model simulations with the same input parameters. The parameterization takes into account for the altitude dependence of molecular number density, ozone content, aerosol and spatial surface albedo. We also provide generalized altitude dependencies of the parameters for evaluating the AUV. The resulting comparison of the altitude UV effects using the proposed method shows a good agreement with the accurate 8-stream DISORT model simulations with correlation coefficient r > 0.996. A satisfactory agreement was also obtained with the experimental UV data in mountain regions. Using this parameterization we analyzed the role of different geophysical parameters in UV variations with altitude. The decrease in molecular number density, especially at high altitudes, and the increase in surface albedo play the most significant role in the UV growth. Typical aerosol and ozone altitude UV effects do not exceed 10–20 %. Using the proposed parameterization implemented in the on-line UV tool (http://momsu.ru/uv/) for Northern Eurasia over the PEEX domain we analyzed the altitude UV increase and its possible effects on human health considering different skin types and various open body fraction for January and April conditions in the Alpine region.

Evaluation of World Population-Weighted Effective Dose due to Cosmic Ray Exposure.

After the release of the Report of the United Nations Scientific Committee of the Effects of Atomic Radiation in 2000 (UNSCEAR2000), it became commonly accepted that the world population-weighted effective dose due to cosmic-ray exposure is 0.38 mSv, with a range from 0.3 to 2 mSv. However, these values were derived from approximate projections of altitude and geographic dependences of the cosmic-ray dose rates as well as the world population. This study hence re-evaluated the population-weighted annual effective doses and their probability densities for the entire world as well as for 230 individual nations, using a sophisticated cosmic-ray flux calculation model in tandem with detailed grid population and elevation databases. The resulting world population-weighted annual effective dose was determined to be 0.32 mSv, which is smaller than the UNSCEAR’s evaluation by 16%, with a range from 0.23 to 0.70 mSv covering 99% of the world population. These values were noted to vary with the solar modulation condition within a range of approximately 15%. All assessed population-weighted annual effective doses as well as their statistical information for each nation are provided in the supplementary files annexed to this report. These data improve our understanding of cosmic-ray radiation exposures to populations globally.

Ionospheric ion temperature climate and upper atmospheric long‐term cooling

AbstractIt is now recognized that Earth's upper atmosphere is experiencing a long‐term cooling over the past several solar cycles. The potential impact of the cooling on societal activities is significant, but a fundamental scientific question exists regarding the drivers of the cooling. New observations and analyses provide crucial advances in our knowledge of these important processes. We investigate ionospheric ion temperature climatology and long‐term trends using up‐to‐date large and consistent ground‐based data sets as measured by multiple incoherent scatter radars (ISRs). The very comprehensive view provided by these unique observations of the upper atmospheric thermal status allows us to address drivers of strong cooling previously observed by ISRs. We use observations from two high‐latitude sites at Sondrestrom (invariant latitude 73.2°N) from 1990 to 2015 and Chatanika/Poker Flat (invariant latitude 65.9°N) over the span of 1976–2015 (with a gap from 1983 to 2006). Results are compared to conditions at the midlatitude Millstone Hill site (invariant latitude 52.8°N) from 1968 to 2015. The aggregate radar observations have very comparable and consistent altitude dependence of long‐term trends. In particular, the lower F region (<275 km) exhibits dayside cooling trends that are significantly higher (−3 to −1 K/yr at 250 km) than anticipated from model predictions given the anthropogenic increase of greenhouse gases. Above 275 km, cooling trends continue to increase in magnitude but values are strongly dependent on magnetic latitude, suggesting the presence of significant downward influences from nonneutral atmospheric processes.

A new angle for probing field‐aligned irregularities with the Murchison Widefield Array

AbstractElectron density irregularities in the ionosphere are known to be magnetically anisotropic, preferentially elongated along the lines of force. While many studies of their morphology have been undertaken by topside sounding and whistler measurements, it is only recently that detailed regional‐scale reconstructions have become possible, enabled by the advent of widefield radio telescopes. Here we present a new approach for visualizing and studying field‐aligned irregularities (FAIs), which involves transforming interferometric measurements of total electron content gradients onto a magnetic shell tangent plane. This removes the perspective distortion associated with the oblique viewing angle of the irregularities from the ground, facilitating the decomposition of dynamics along and across magnetic field lines. We apply this transformation to the data set of Loi et al. (2015a), obtained on 15 October 2013 by the Murchison Widefield Array (MWA) radio telescope and displaying prominent FAIs. We study these FAIs in the new reference frame, quantifying field‐aligned and field‐transverse behavior, examining time and altitude dependencies, and extending the analysis to FAIs on subarray scales. We show that the inclination of the plane can be derived solely from the data and verify that the best fit value is consistent with the known magnetic inclination. The ability of the model to concentrate the fluctuations along a single spatial direction may find practical application to future calibration strategies for widefield interferometry, by providing a compact representation of FAI‐induced distortions.

Effects of wet deposition on the abundance and size distribution of black carbon in East Asia

AbstractAn improved understanding of the variations in the mass concentration and size distribution of black carbon (BC) in the free troposphere (FT) over East Asia, where BC emissions are very high, is needed to reliably estimate the radiative forcing of BC in climate models. We measured these parameters and the carbon monoxide (CO) concentration by conducting the Aerosol Radiative Forcing in East Asia (A‐FORCE) 2013W aircraft campaign in East Asia in winter 2013 and compared these data with measurements made in the same region in spring 2009. The median BC concentrations in the FT originating from North China (NC) and South China (SC) showed different seasonal variations, which were primarily caused by variations in meteorological conditions. CO concentrations above the background were much higher in SC than in NC in both seasons, suggesting a more active upward transport of CO. In SC, precipitation greatly increased from winter to spring, leading to an increased wet deposition of BC. As a result, the median BC concentration in the FT was highest in SC air in winter. This season and region were optimal for the effective transport of BC from the planetary boundary layer to the FT. The count median diameters of the BC size distributions generally decreased with altitude via wet removal during upward transport. The altitude dependence of the BC size distributions was similar in winter and spring, in accord with the similarity in the BC mixing state. The observed BC concentrations and microphysical properties will be useful for evaluating the performance of climate models.

The results from ten years of measuring several parameters of the antarctic atmosphere with tethered balloons

The results from measuring several parameters of the Antarctic atmosphere’s lower layers over the period 2004 through 2014 (Russian Antarctic expeditions 49 through 59) are presented. Such atmospheric parameters as the altitude dependence of the velocity and direction of the ground wind, the level of background radiation, and the concentrations of ozone and singlet oxygen are studied. Devices are installed on board the vessel Akademik Fedorov and at Antarctic ground stations. Tethered balloons are also used.

Solar wind‐generated current in the Lunar Dust Experiment

AbstractMeasurements from the Lunar Dust Experiment (LDEX) show that the current associated with lofted lunar dust lacks an altitude dependence, implying that the current may come from other sources. Here we present some evidences for solar wind (SW)‐generated current. Direct SW influx on the nightside can cause a large current, and the backscattered energetic neutral atoms (ENAs) on the dayside can bring a good correlation between the current and SW density. It is found that the current favors a lower SW speed and a smaller SW incident angle, but the dependences are also affected by the solar zenith angle (SZA) and the scattering function of ENAs. Picked‐up ions can enhance the current when the angle between the convection electric field and LDEX's normal is larger than 90°. But when the angle is smaller than 90°, the enhancement is negligible.

On the polarization relations of diurnal and semidiurnal tide in the mesopause region

The polarization relations for gravity waves are well known and have proven to be very powerful for the investigation of their dynamics. Though tides are sometimes regarded as low-frequency gravity waves, their polarization relations are hardly considered. We derive the polarization relationships of tides from the primitive equations for perturbations of a dissipation-less atmosphere. The vertical wind tide is found to relate directly to temperature tide, independent of tidal structure and geometric location. On the other hand, the relation between meridional wind tide and zonal wind tide is found to depend on the horizontal derivatives of the associated geopotential perturbation, thus depending on tidal structure and geometric location. Lidar observed tides at a local station (tidal period perturbations) in the midlatitude mesopause region (80–105km) and the Climatological Tidal Model of the Thermosphere (CTMT) based on Hough Mode Extension (HME) technique at the lidar site, both of which include the effect of dissipation, are then compared. These tidal amplitudes and phases are employed to discuss the results and implications of the derived tidal wave polarization relations. The dominance of the migrating tide follows from the phase relationship between zonal and meridional wind tides. By comparing the observed and derived vertical wind tides, we reveal qualitatively the altitude dependence of tidal wave dissipation.

Observed high-altitude warming and snow cover retreat over Tibet and the Himalayas enhanced by black carbon aerosols

Abstract. Himalayan mountain glaciers and the snowpack over the Tibetan Plateau provide the headwater of several major rivers in Asia. In situ observations of snow cover extent since the 1960s suggest that the snowpack in the region have retreated significantly, accompanied by a surface warming of 2–2.5 °C observed over the peak altitudes (5000 m). Using a high-resolution ocean–atmosphere global climate model and an observationally constrained black carbon (BC) aerosol forcing, we attribute the observed altitude dependence of the warming trends as well as the spatial pattern of reductions in snow depths and snow cover extent to various anthropogenic factors. At the Tibetan Plateau altitudes, the increase in atmospheric CO2 concentration exerted a warming of 1.7 °C, BC 1.3 °C where as cooling aerosols cause about 0.7 °C cooling, bringing the net simulated warming consistent with the anomalously large observed warming. We therefore conclude that BC together with CO2 has contributed to the snow retreat trends. In particular, BC increase is the major factor in the strong elevation dependence of the observed surface warming. The atmospheric warming by BC as well as its surface darkening of snow is coupled with the positive snow albedo feedbacks to account for the disproportionately large role of BC in high-elevation regions. These findings reveal that BC impact needs to be properly accounted for in future regional climate projections, in particular on high-altitude cryosphere.

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.