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- Author or Editor: R. D. Hudson x
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Abstract
Knowledge of the agronomic production of odd hydrogen in the dissociation of water vapor is limited by uncertainties in the penetration of solar irradiance in the Schumann-Rung bands of O2 and by incomplete information concerning the products of photolysis at Lyman alpha. Consideration of an error sources involved in computing the H2o dissociation rate in the wavelength region 175–200 nm leads to an estimated uncertainty of ±35% at an altitude of 90 km for an overhead sun. The uncertainty increases with decreasing altitude such that the true dissociation rate at 60 km for an overhead sun lies between 0.45 and 1.55 times the result computed using the best input parameters currently available. Calculations of the H2o dissociation rate by Lyman alpha should include the variation in O2 opacity across the solar line width. Neglect of this can lead to errors as large as 50% at altitudes where the process is the major source of odd hydrogen.
Abstract
Knowledge of the agronomic production of odd hydrogen in the dissociation of water vapor is limited by uncertainties in the penetration of solar irradiance in the Schumann-Rung bands of O2 and by incomplete information concerning the products of photolysis at Lyman alpha. Consideration of an error sources involved in computing the H2o dissociation rate in the wavelength region 175–200 nm leads to an estimated uncertainty of ±35% at an altitude of 90 km for an overhead sun. The uncertainty increases with decreasing altitude such that the true dissociation rate at 60 km for an overhead sun lies between 0.45 and 1.55 times the result computed using the best input parameters currently available. Calculations of the H2o dissociation rate by Lyman alpha should include the variation in O2 opacity across the solar line width. Neglect of this can lead to errors as large as 50% at altitudes where the process is the major source of odd hydrogen.
Abstract
Oscillator strengths and predissociation linewidths deduced in recent studies predict a dissociation rate for O2 in the Schumann-Runge bands which is significantly larger in the upper stratosphere and lower mesosphere than previously believed. Error bars on molecular parameters required in the cross-section calculation translate into uncertainties in the dissociation rate which are less than ±10% at all altitudes where the Schumann-Runge bands are agronomically significant.
Abstract
Oscillator strengths and predissociation linewidths deduced in recent studies predict a dissociation rate for O2 in the Schumann-Runge bands which is significantly larger in the upper stratosphere and lower mesosphere than previously believed. Error bars on molecular parameters required in the cross-section calculation translate into uncertainties in the dissociation rate which are less than ±10% at all altitudes where the Schumann-Runge bands are agronomically significant.
Abstract
Absorption of solar photons by nitric oxide in the wavelength ranges 181.3–183.5 and 189.4–191.6 nm leads to predissociation of the molecule in the mesosphere and upper stratosphere. Molecular oxygen controls the penetration of the required solar irradiance via absorption in the Schumann-Runge bands, while attenuation due to ozone becomes significant in the upper stratosphere. The calculation of the nitric oxide dissociation rate is complicated by the need to include all rotational fine structure in both the NO and O2 cross sections. The dissociation rate computed here for the upper mesosphere is a factor of 3.6 less than that reported in past work when currently accepted values of the oscillator strengths and solar irradiance are used. In addition, improved molecular parameters describing the O2 cross section predict less attenuation of the dissociation rate with decreasing altitude than results previously available.
Abstract
Absorption of solar photons by nitric oxide in the wavelength ranges 181.3–183.5 and 189.4–191.6 nm leads to predissociation of the molecule in the mesosphere and upper stratosphere. Molecular oxygen controls the penetration of the required solar irradiance via absorption in the Schumann-Runge bands, while attenuation due to ozone becomes significant in the upper stratosphere. The calculation of the nitric oxide dissociation rate is complicated by the need to include all rotational fine structure in both the NO and O2 cross sections. The dissociation rate computed here for the upper mesosphere is a factor of 3.6 less than that reported in past work when currently accepted values of the oscillator strengths and solar irradiance are used. In addition, improved molecular parameters describing the O2 cross section predict less attenuation of the dissociation rate with decreasing altitude than results previously available.
Radiation is the driving force for the general circulation of the atmosphere and controls the Earth's climate. Ozone is responsible for the warm stratosphere and protects life on Earth from harmful solar ultraviolet radiation. In July 1959, the International Radiation Commission and the International Ozone Commission organized a joint meeting in Oxford, United Kingdom. The meeting took place just after the conclusion of the world's first international global observing program in the Earth sciences—the International Geophysical Year of 1957/58. The “Symposia on Radiation and Ozone” at the Oxford meeting included many reports with first results from the IGY, but there were also papers that foreshadowed future developments in atmospheric science. We take this opportunity on the 50th anniversary of the Oxford meeting to present a brief account of the roles of the Radiation and Ozone Commissions, and, more broadly, their interactions with the international science structure, in advancing atmospheric science over the last century. We also take a look at some of the topics discussed and the key figures at the 1959 Oxford meeting.
Radiation is the driving force for the general circulation of the atmosphere and controls the Earth's climate. Ozone is responsible for the warm stratosphere and protects life on Earth from harmful solar ultraviolet radiation. In July 1959, the International Radiation Commission and the International Ozone Commission organized a joint meeting in Oxford, United Kingdom. The meeting took place just after the conclusion of the world's first international global observing program in the Earth sciences—the International Geophysical Year of 1957/58. The “Symposia on Radiation and Ozone” at the Oxford meeting included many reports with first results from the IGY, but there were also papers that foreshadowed future developments in atmospheric science. We take this opportunity on the 50th anniversary of the Oxford meeting to present a brief account of the roles of the Radiation and Ozone Commissions, and, more broadly, their interactions with the international science structure, in advancing atmospheric science over the last century. We also take a look at some of the topics discussed and the key figures at the 1959 Oxford meeting.
Abstract
Reliable and accurate environmental sensing is a cornerstone of modern meteorology. This paper presents a laboratory environmental simulator capable of reproducing extreme environments and performing tests and calibrations of meteorological sensor systems under controlled conditions. This facility is available to the research community as well as industry and is intended to encourage advancement in the field of sensor metrology applied to meteorology and climatology. Discussion will be made of the temperature, pressure, humidity and wind flow control, and sensing systems with reference to specific sensor test programs and future research activities.
Abstract
Reliable and accurate environmental sensing is a cornerstone of modern meteorology. This paper presents a laboratory environmental simulator capable of reproducing extreme environments and performing tests and calibrations of meteorological sensor systems under controlled conditions. This facility is available to the research community as well as industry and is intended to encourage advancement in the field of sensor metrology applied to meteorology and climatology. Discussion will be made of the temperature, pressure, humidity and wind flow control, and sensing systems with reference to specific sensor test programs and future research activities.
Shallow, maritime cumuli are ubiquitous over much of the tropical oceans, and characterizing their properties is important to understanding weather and climate. The Rain in Cumulus over the Ocean (RICO) field campaign, which took place during November 2004–January 2005 in the trades over the western Atlantic, emphasized measurements of processes related to the formation of rain in shallow cumuli, and how rain subsequently modifies the structure and ensemble statistics of trade wind clouds. Eight weeks of nearly continuous S-band polarimetric radar sampling, 57 flights from three heavily instrumented research aircraft, and a suite of ground- and ship-based instrumentation provided data on trade wind clouds with unprecedented resolution. Observational strategies employed during RICO capitalized on the advances in remote sensing and other instrumentation to provide insight into processes that span a range of scales and that lie at the heart of questions relating to the cause and effects of rain from shallow maritime cumuli.
Shallow, maritime cumuli are ubiquitous over much of the tropical oceans, and characterizing their properties is important to understanding weather and climate. The Rain in Cumulus over the Ocean (RICO) field campaign, which took place during November 2004–January 2005 in the trades over the western Atlantic, emphasized measurements of processes related to the formation of rain in shallow cumuli, and how rain subsequently modifies the structure and ensemble statistics of trade wind clouds. Eight weeks of nearly continuous S-band polarimetric radar sampling, 57 flights from three heavily instrumented research aircraft, and a suite of ground- and ship-based instrumentation provided data on trade wind clouds with unprecedented resolution. Observational strategies employed during RICO capitalized on the advances in remote sensing and other instrumentation to provide insight into processes that span a range of scales and that lie at the heart of questions relating to the cause and effects of rain from shallow maritime cumuli.
Abstract
Anomalously high reflectivity tracks in stratus and stratocumulus sheets associated with ships (known as ship tracks) are commonly seen in visible and near-infrared satellite imagery. Until now there have been only a limited number of in situ measurements made in ship tracks. The Monterey Area Ship Track (MAST) experiment, which was conducted off the coast of California in June 1994, provided a substantial dataset on ship emissions and their effects on boundary layer clouds. Several platforms, including the University of Washington C-131A aircraft, the Meteorological Research Flight C-130 aircraft, the National Aeronautics and Space Administration ER-2 aircraft, the Naval Research Laboratory airship, the Research Vessel Glorita, and dedicated U.S. Navy ships, participated in MAST in order to study processes governing the formation and maintenance of ship tracks.
This paper tests the hypotheses that the cloud microphysical changes that produce ship tracks are due to (a) particulate emission from the ship’s stack and/or (b) sea-salt particles from the ship’s wake. It was found that ships powered by diesel propulsion units that emitted high concentrations of aerosols in the accumulation mode produced ship tracks. Ships that produced few particles (such as nuclear ships), or ships that produced high concentrations of particles but at sizes too small to be activated as cloud drops in typical stratocumulus (such as gas turbine and some steam-powered ships), did not produce ship tracks. Statistics and case studies, combined with model simulations, show that provided a cloud layer is susceptible to an aerosol perturbation, and the atmospheric stability enables aerosol to be mixed throughout the boundary layer, the direct emissions of cloud condensation nuclei from the stack of a diesel-powered ship is the most likely, if not the only, cause of the formation of ship tracks. There was no evidence that salt particles from ship wakes cause ship tracks.
Abstract
Anomalously high reflectivity tracks in stratus and stratocumulus sheets associated with ships (known as ship tracks) are commonly seen in visible and near-infrared satellite imagery. Until now there have been only a limited number of in situ measurements made in ship tracks. The Monterey Area Ship Track (MAST) experiment, which was conducted off the coast of California in June 1994, provided a substantial dataset on ship emissions and their effects on boundary layer clouds. Several platforms, including the University of Washington C-131A aircraft, the Meteorological Research Flight C-130 aircraft, the National Aeronautics and Space Administration ER-2 aircraft, the Naval Research Laboratory airship, the Research Vessel Glorita, and dedicated U.S. Navy ships, participated in MAST in order to study processes governing the formation and maintenance of ship tracks.
This paper tests the hypotheses that the cloud microphysical changes that produce ship tracks are due to (a) particulate emission from the ship’s stack and/or (b) sea-salt particles from the ship’s wake. It was found that ships powered by diesel propulsion units that emitted high concentrations of aerosols in the accumulation mode produced ship tracks. Ships that produced few particles (such as nuclear ships), or ships that produced high concentrations of particles but at sizes too small to be activated as cloud drops in typical stratocumulus (such as gas turbine and some steam-powered ships), did not produce ship tracks. Statistics and case studies, combined with model simulations, show that provided a cloud layer is susceptible to an aerosol perturbation, and the atmospheric stability enables aerosol to be mixed throughout the boundary layer, the direct emissions of cloud condensation nuclei from the stack of a diesel-powered ship is the most likely, if not the only, cause of the formation of ship tracks. There was no evidence that salt particles from ship wakes cause ship tracks.
