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At least 811 records · Page 45

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NASA NTRS2015

Sensitivity of Water Scarcity Events to ENSO-Driven Climate Variability at the Global Scale

Globally, freshwater shortage is one of the most dangerous risks for society. Changing hydro-climatic and socioeconomic conditions have aggravated water scarcity over the past decades. A wide range of studies show that water scarcity will intensify in the future, as a result of both increased consumptive water use and, in some regions, climate change. Although it is well-known that El Niño- Southern Oscillation (ENSO) affects patterns of precipitation and drought at global and regional scales, little attention has yet been paid to the impacts of climate variability on water scarcity conditions, despite its importance for adaptation planning. Therefore, we present the first global-scale sensitivity assessment of water scarcity to ENSO, the most dominant signal of climate variability. We show that over the time period 1961-2010, both water availability and water scarcity conditions are significantly correlated with ENSO-driven climate variability over a large proportion of the global land area (> 28.1 %); an area inhabited by more than 31.4% of the global population. We also found, however, that climate variability alone is often not enough to trigger the actual incidence of water scarcity events. The sensitivity of a region to water scarcity events, expressed in terms of land area or population exposed, is determined by both hydro-climatic and socioeconomic conditions. Currently, the population actually impacted by water scarcity events consists of 39.6% (CTA: consumption-to-availability ratio) and 41.1% (WCI: water crowding index) of the global population, whilst only 11.4% (CTA) and 15.9% (WCI) of the global population is at the same time living in areas sensitive to ENSO-driven climate variability. These results are contrasted, however, by differences in growth rates found under changing socioeconomic conditions, which are relatively high in regions exposed to water scarcity events. Given the correlations found between ENSO and water availability and scarcity conditions, and the relative developments of water scarcity impacts under changing socioeconomic conditions, we suggest that there is potential for ENSO-based adaptation and risk reduction that could be facilitated by more research on this emerging topic.

risk↗

NASA NTRS2016

Aging Will Amplify the Heat-Related Mortality Risk Under a Changing Climate: Projection for the Elderly in Beijing, China

An aging population could substantially enhance the burden of heat-related health risks in a warming climate because of their higher susceptibility to extreme heat health effects. Here, we project heatrelated mortality for adults 65 years and older in Beijing China across 31 downscaled climate models and 2 representative concentration pathways (RCPs) in the 2020s, 2050s, and 2080s. Under a scenario of medium population and RCP8.5, by the 2080s, Beijing is projected to experience 14,401 heat-related deaths per year for elderly individuals, which is a 264.9% increase compared with the 1980s. These impacts could be moderated through adaptation. In the 2080s, even with the 30% and 50% adaptation rate assumed in our study, the increase in heat-related death is approximately 7.4 times and 1.3 times larger than in the 1980s respectively under a scenario of high population and RCP8.5. These findings could assist countries in establishing public health intervention policies for the dual problems of climate change and aging population. Examples could include ensuring facilities with large elderly populations are protected from extreme heat (for example through back-up power supplies and/or passive cooling) and using databases and community networks to ensure the home-bound elderly are safe during extreme heat events.

age factor↗

NASA NTRS1972

A method for phenomenological analysis of ecological data.

The experimental meaning of the phenomenological differential equations for a competing population is reviewed. It is concluded that it is virtually impossible to construct the differential equations precise enough for studying stability. We consider instead a method of phenomenological analysis which can be applied to a set of population curves. We suggest an ecological index calculated from the population curves, which indicates a group property of the entire system. As a function of time, the index is presumably insensitive to Volterra type fluctuations. A marked increase of the index's value however indicates a marked change of the environmental conditions. It is not easy to deduce the group property from the population curves alone, because a change in population is in general due to the superposition of external disturbances and Volterra fluctuations.

Huang, H.-W.↗

NASA NTRS1976

The record of impact cratering on the great volcanic shields of the Tharsis region of Mars

The spatial density of impact craters larger than 100 m on the four great volcanic shields in the Tharsis region is analyzed, assuming that each observed crater population represents the total formed since the local surface was last renewed. Previous investigations of this type are reviewed, problems encountered in those studies are discussed, and an attempt is made to overcome these problems by applying explicit criteria for the separation of craters smaller than approximately 1 km in diameter according to their origin and by ignoring larger craters. Relative ages are determined by comparing crater populations at a common diameter, and such comparisons are carried out for six populations on Arsia Mons, one population on Pavonis Mons, several craters on Ascraeus Mons, and two populations on Olympus Mons. The results, presented in terms of 'crater ages', indicate that most dated surfaces on the great shields range in age from 0.5 to 1.2 billion years, that the eruption patterns of the volcanoes are similar to those of the Hawaiian basaltic shields, and that the most frequently renewed surfaces are on the middle-to-lower flanks as well as within the summit calderas. The youngest surfaces are estimated to date from the period between 0.5 billion years ago and the present; the oldest dated surfaces are shown to suggest that the volcanoes had attained essentially their present sizes over 1 billion years ago.

Blasius, K. R.↗

NASA NTRS1977

Crater saturation and equilibrium - A Monte Carlo simulation

Conditions of crater saturation and equilibrium have been simulated with a Monte Carlo computer program which utilizes a generating function of the form N = b x D to the -a. The following conclusions have been deduced from the results of the model: (1) saturation and equilibrium for large craters occur at crater densities substantially greater than those observed on the moon, Mars, and Mercury, an indication that the observed populations are essentially production populations, (2) generating functions with a greater than 2 lead to final crater populations with a = 2, (3) generating functions with a between 2 and 1.5 lead to crater populations with the parameter a approaching 1.0, and (4) changes in the slope of crater populations occur gradually and over a wide interval of crater densities and diameters as saturation is approached.

Woronow, A.↗

NASA NTRS1978

A general cratering-history model and its implications for the lunar highlands

Through analysis of a large number of Monte Carlo and Markov Chain simulations, a model for determining crater accumulation and crater obliteration histories has been derived. The model generally applies to populations of large craters. It predicts that the following relationships hold for subequilibrium-density crater populations: (1) the more negative the production function's exponent, alpha (N near D super alpha) the lower the crater density at which the population size-frequency distribution will significantly depart from its production function; (2) the more negative the production function's exponent, the less obliteration a crater population will sustain after a set number of impacts. Application of the model to the lunar highlands implies (1) the production function for the large craters is highly structured, resembling the observed size-frequency distribution and not the function N near D to the -2; (2) even the densely cratered highlands have not attained crater saturation or equilibrium. Direct simulations of the highlands' crater population supports the model's implications.

Woronow, A.↗

NASA NTRS1980

Some problems of human adaptation and ecology under the aspect of general pathology

The main problems of human adaptation at the level of the body and the population in connection with the features of current morbidity of the population and certain demographic processes are analyzed. The concepts of health and adaptation of the individual and human populations are determined. The importance of the anthropo-ecological approach to the investigation of the adaptation process of human populations is demonstrated. Certain features of the etiopathogenesis of diseases are considered in connection with the population-ecological regularities of human adaptation. The importance of research on general pathology aspects of adaptation and the ecology of man for planning, and organization of public health protection is discussed.

Kaznacheyev, V. P.↗

NASA NTRS1984

The fallacy of using NII in analyzing aircraft operations

Three measures of noise annoyance (Noise Impact Index, Level-Weighted Population, and Annoyed Population Number) are compared, regarding their utility in assessing noise reduction schemes for aircraft operations. While NII is intended to measure the average annoyance per person in a community, it is found that the method of averaging can lead to erroneous conclusions, particularly if the population does not have uniform spatial distribution. Level-Weighted Population and Annoyed Population Number are shown to be better indicators of noise annoyance when rating different strategies for noise reduction in a given community.

Melton, R. G.↗

NASA NTRS1983

Ferromagnesian chondrules in carbonaceous chondrites

Carbonaceous chondrites (groups CO and CV) contain three types of ferromagnesian chondrules that can be distinguished on the basis of mineralogy and texture. Statistical analysis of the bulk chemical compositions of these chondrule types suggest that two of the three types are genetically related. The chondrules in carbonaceous chondrites can thus be separated into two populations. These populations are also apparently distinct in terms of redox state and oxygen isotopic composition. The more abundant population (I) is clearly different from chondrules in unequilibrated ordinary chondrites, but the minor population (II) is similar to them in many respects. These chondrule populations may have formed by melting of solid, locally homogeneous precursor materials in different regions of the nebula, and were mixed after solidification was complete.

Mcsween, H. Y., Jr.↗

NASA NTRS1986

Is Jupiter's ionosphere a significant plasma source for its magnetosphere?

A semikinetic model was used to study the steady state, collisionless, polar wind outflow from the Jovian polar caps. H(+)-escape fluxes and energies were calculated for a range of conditions, including several values of the ambient electron temperature, different hot electron populations, and both with and without the effects of the centrifugal force. The calculations indicate that if hot electron populations exist over the Jovian polar caps, as they do on earth, polar wind escape fluxes of the order of 10 to the 8th per sq cm s are possible. When integrated over the polar cap area, escape fluxes of this order of magnitude imply an ionospheric source strength of 2 x 10 to the 28th ions/s, which is comparable to the present estimate of the total magnetospheric plasma source population. Therefore, the ionosphere may play an important role in populating the Jovian magnetosphere, specifically the hidden, low energy, light ion component of the population.

Nagy, A. F.↗

NASA NTRS1988

Bimodal abundances in the energetic particles of solar and interplanetary origin

This letter reports the first results from an examination of the daily-averaged abundances of the elements from H through Fe as well as electrons and isotopes of He in energetic particles observed in interplanetary space by the ISEE 3 spacecraft over an 8.5 yr period. The abundances of heavy elements such as Fe/O show, for the first time, clear evidence of the presence of two distinct populations of particles. Earlier observations could be interpreted as extreme variations within a single population. The population with enhanced Fe/O shows correlated enhancements in He-3/He-4, p/e, and He/H. This population is consistent with material that has been processed to high temperatures in the impulsively heated regions of solar flares. The second population, with more normal abundances, is probably accelerated from ambient material by coronal and interplanetary shocks.

Reames, Donald V.↗

NASA NTRS1988

The ridged plains as a possible landing site for the Mars sample return mission

Differences in the shape and density of crater size-frequency distribution curves have been interpreted as indicators of different impactor populations. Within the inner solar system two production populations are seen. The signature of the first is recorded in the heavily cratered regions of the Moon, Mercury, and Mars and displays a multi-sloped distribution curve which cannot be described by a power law function at all crater diameters. The signature of the second population is seen in the lightly cratered lunar and Martian plains, where the size-frequency distribution curve can be approximated by a power law function of -3 differential slope in the 8- to 70-km diameter range. Based on data obtained from the Apollo lunar samples and crater flux estimates, the first population is believed to have been emplaced during the period of heavy bombardment which, at least on the Moon, ended about 3.8 BY ago. The second population has dominated the cratering record since that time and is commonly assumed to be due to comets and asteroids.

Barlow, Nadine G.↗

NASA NTRS1989

Anisotropy of shock-accelerated ion distributions in interplanetary space

The discrepancy between theory and observation is discussed with regard to the ability of interplanetary shock waves to accelerate a small percentage of the thermal ion population. The major point of departure rests with the spatial dependence of the energetic particle intensity and anisotropy in the region upstream of interplanetary shocks. It is argued that the discrepancy is due to the presence of solar flare particles forming an additional seed population which alters the upstream boundary condition of the energetic population. The resulting anisotropy of the energetic particle distribution several scale lengths upstream of the shock is proportional to the ratio of the streaming of the shock-accelerated population to the density of the solar flare population. This theory is then compared with the results of observed upstream anisotropy and measured particle intensities and anisotropies.

Smith, Charles W.↗

NASA NTRS1989

Long-slit optical spectroscopy of powerful far-infrared galaxies - The nature of the nuclear energy source

Optical spectroscopic data are presented for a sample of 47 powerful far-IR galaxies chosen for IR spectral shape, and for six other IR-bright galaxies. The stellar absorption lines expected from a population of old stars are generally very weak in the nuclei of the galaxies. Very weak Mg I absorption is found in regions well off the nucleus, implying that the visible spectrum is dominated by young stars and not by an AGN. At least one, and probably five, of the galaxies have detectable WR emission features, providing additional evidence for a young stellar population. About 20 percent of the galaxies have strong Balmer absorption lines, indicating the presence of a substantial intermediate-age stellar population. The equivalent width of the H-alpha emission line can be modeled as arising from a mixture of a large young population and an intermediate-age population of stars.

Armus, Lee↗

NASA NTRS1990

Stellar content of nearby galaxies. III - The local group spiral galaxy M33

BVRI CCD photometry is presented for stars brighter than V = 21 mag in four fields in the nearby spiral galaxy M33. V vs (B - V) and I vs (V - I) color-magnitude diagrams clearly show both a young stellar population (as indicated by the blue main sequence and red supergiant plumes) as well as an intermediate-age population of asymptotic giant branch stars. Deep photometry in the outer field (where crowding is less severe) reveals a population consistent in color and magnitude with the tip of the first red giant branch. The M33 distance modulus, 24.6 + or - 0.3 mag, derived from this Population II component is consistent with a recent redetermination of the distance modulus found from Population I Cepheid variables. Finally, some evidence is presented for a radial gradient in the average internal reddening for the fields in M33 reported here.

Wilson, Christine D.↗

NASA NTRS1991

Ancient fluvial processes in the equatorial highlands of Mars

Martian highland craters typically lack ejecta deposits, have no noticeable rim, and are flat floored. In addition, crater size frequency distribution curves show that highland craters have depleted populations less than 20 km in diameter. A variety of processes have been suggested to explain these observations including deposition of aeolian or volcanic materials up to the crater rim crests, thermal creep, terrain softening, and mass wasting. However, none of these processes adequately explains both the crater morphology and population distribution. In order to explain both the Martian highland crater morphology and population distribution, a fluvial process is proposed which is capable of removing the loose crater rim material. The resulting effect is to decrease the crater diameter, thereby causing the population curves to bendover. The eroded material is redistributed, burying or partially burying smaller diameter craters before complete erosion. This material may also be deposited into local topographic lows, creating the depositional basins observed. A fluvial process explains both sets of observations: crater morphology and crater population distribution curves.

Craddock, Robert A.↗

NASA NTRS1992

Solar wind halo electrons from 1-4 AU

Observations from the Ulysses solar wind electron spectrometer are used to make a first examination of the evolution of the solar wind suprathermal or halo electron population as a function of heliocentric distance beyond 1 AU. As the core population cools with increasing heliocentric distance, no gap is formed between the core and halo populations. Rather, the halo electrons extend to increasingly lower energies. As predicted previously on theoretical grounds, the ratio of the core electron temperature to the low energy cutoff of the halo population appears to be roughly constant with a value of about 7.5. The total integrated heat flux drops rapidly with increasing heliocentric distance; a best fit power law of R exp -2.36 is found. In addition, it is found that the ratio of the halo to core densities is roughly constant over heliocentric distance with the halo representing 4 percent of the total electron distribution. These results suggest that the halo population may not consist of truly noninteractive test particles over the heliocentric range of 1-4 AU.

Mccomas, D. J.↗

NASA NTRS1993

Deep, wide-field, multi-band imaging of z approximately equal to 0.4 clusters and their environs

The existence of an excess population of blue galaxies in the cores of distant, rich clusters of galaxies, commonly referred to as the 'Butcher-Oemler' effect is now well established. Spectroscopy of clusters at z = 0.2-0.4 has confirmed that the luminous blue populations comprise as much as 20 percent of these clusters. This fraction is much higher that the 2 percent blue fraction found for nearby rich clusters, such as Coma, indicating that rapid galaxy evolution has occurred on a relatively short time scale. Spectroscopy has also shown that the 'blue' galaxies can basically be divided into three classes: 'starburst' galaxies with large (O II) equivalent widths, 'post-starburst' E+A galaxies (i.e. galaxies with strong Balmer lines shortward of 4000A but elliptical-like colors, and normal spiral/irregulars. Unfortunately, it is difficult to obtain enough spectra of individual galaxies in these intermediate redshift clusters to say anything statistically meaningful. Thus, limited information is available about the relative numbers of these three classes of 'blue' galaxies and the associated E/SO population in these intermediate redshift clusters. More statistically meaningful results can be derived from deep imaging of these clusters. However, the best published data to date (e.g. MacLaren et al. 1988; Dressler & Gunn 1992) are limited to the cluster cores and do not sample the galaxy luminosity functions very deeply at the bluest wavelengths. Furthermore, only limited spectro-energy distribution data is available below 4000A in the observed cluster rest frame providing limited sensitivity to 'recent' star formation activity. To improve this situation, we are currently obtaining deep, wide-field UBRI images of all known rich clusters at z approx. equals 0.4. Our main objective is to obtain the necessary color information to distinguish between the E+SO, 'E+A', and spiral/irregular galaxy populations throughout the cluster/supercluster complex. At this redshift, UBRI correspond to rest-frame 2500A/UVR bandpasses. The rest-frame UVR system provides a powerful 'blue' galaxy discriminate given the expected color distribution. Moreover, since 'hot' stars peak near 2500A, that bandpass is a powerful probe of recent star formation activity in all classes of galaxies. In particular, it is sensitive to ellipticals with 'UV excess' populations (MacLaren et al. 1988).

Silva, David R.↗