Atmospheric pressure

About: Atmospheric pressure is a(n) research topic. Over the lifetime, 23452 publication(s) have been published within this topic receiving 348669 citation(s). The topic is also known as: presión del aire & presión barométrica.

Air pressure and cosmogenic isotope production

Abstract: The cosmic ray flux increases at higher altitude as air pressure and the shielding effect of the atmosphere decrease. Altitude-dependent scaling factors are required to compensate for this effect in calculating cosmic ray exposure ages. Scaling factors in current use assume a uniform relationship between altitude and atmospheric pressure over the Earth's surface. This masks regional differences in mean annual pressure and spatial variation in cosmogenic isotope production rates. Outside Antarctica, air pressures over land depart from the standard atmosphere by ±4.4 hPa (1σ) near sea level, corresponding to offsets of ±3–4% in isotope production rates. Greater offsets occur in regions of persistent high and low pressure such as Siberia and Iceland, where conventional scaling factors predict production rates in error by ±10%. The largest deviations occur over Antarctica where ground level pressures are 20–40 hPa lower than the standard atmosphere at all altitudes. Isotope production rates in Antarctica are therefore 25–30% higher than values calculated by scaling Northern Hemisphere production rates with conventional scaling factors. Exposure ages of old Antarctic surfaces, especially those based on cosmogenic radionuclides at levels close to saturation, may be millions of years younger than published estimates.

Influence of land-surface evapotranspiration on the earth's climate

Abstract: Land-surface evapotranspiration is shown to strongly influence global fields of rainfall, temperature and motion by calculations using a numerical model of the atmosphere, confirming the general belief in the importance of evapotranspiration-producing surface vegetation for the earth's climate. The current version of the Goddard Laboratory atmospheric general circulation model is used in the present experiment, in which conservation equations for mass, momentum, moisture and energy are expressed in finite-difference form for a spherical grid to calculate (1) surface pressure field evolution, and (2) the wind, temperature, and water vapor fields at nine levels between the surface and a 20 km height.

Deep Ultraviolet Light-Emitting Hexagonal Boron Nitride Synthesized at Atmospheric Pressure

Abstract: Materials emitting light in the deep ultraviolet region around 200 nanometers are essential in a wide-range of applications, such as information storage technology, environmental protection, and medical treatment Hexagonal boron nitride (hBN), which was recently found to be a promising deep ultraviolet light emitter, has traditionally been synthesized under high pressure and at high temperature We successfully synthesized high-purity hBN crystals at atmospheric pressure by using a nickel-molybdenum solvent The obtained hBN crystals emitted intense 215-nanometer luminescence at room temperature This study demonstrates an easier way to grow high-quality hBN crystals, through their liquid-phase deposition on a substrate at atmospheric pressure

Experimental and theoretical study of a glow discharge at atmospheric pressure controlled by dielectric barrier

Abstract: The aim of this paper is to confirm the existence of atmospheric pressure dielectric controlled glow discharge and to describe its main behavior. Electrical measurements, short time exposure photographs, and numerical modeling were used to achieve this task. Experimental observations and numerical simulation are in good agreement. Therefore, the analysis of the calculated space and time variations of the electric field together with the ion and electron densities helps to explain the discharge mechanisms involved, showing the main role played by the electron as well as helium metastable density just before the discharge is turned on.

AFGL atmospheric constituent profiles (0-120km)

Abstract: : An atmospheric data base consisting of volume mixing ratios (o0 to 12okm) for twenty eight (28) minor and trace gases has been assembled for use with spectral radiance transmittance models. Six references atmospheres, each defining temperature, pressure and density as a function of altitude (selected from the U.S. Standard Supplements, 1966 and the U.S. Standard Atmosphere, 1976) provide a range of climatological choices. Analogous zonal-mean descriptions for 2O, O3, N2O, CO, and CH4 have been subsequently adapted from satellite data and/or dynamical-photochemical analyses. The remaining species are defined by single profiles, usually appropriate for U.S. Standard conditions. Because the entire profile set is preferentially based on available measurements, explicit photochemical consistency between the different species has not been maintained. Keywords: ATMOSPHERIC CONSTITUENTS; TEMPERATURE PROFILES; MODEL ATMOSPHERES.