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- Author or Editor: S. Twomey x
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Abstract
The composition of the larger (> 10−12 g) hygroscopic particles in the atmosphere was investigated, with use of a phase-transition method. Particles were collected on stretched spider webs exposed from an aircraft, and samples were taken in both maritime and continental air in different meteorological and geographical situations. It was found that the great majority of hygroscopic particles was composed of sea salt, sometimes in combination with insoluble material. A chemical test on individual particles indicated that no appreciable decrease in chloride content or replacement of chlorides by carbonates took place. Only occasionally were large soluble particles, other than sea salt, detected.
Abstract
The composition of the larger (> 10−12 g) hygroscopic particles in the atmosphere was investigated, with use of a phase-transition method. Particles were collected on stretched spider webs exposed from an aircraft, and samples were taken in both maritime and continental air in different meteorological and geographical situations. It was found that the great majority of hygroscopic particles was composed of sea salt, sometimes in combination with insoluble material. A chemical test on individual particles indicated that no appreciable decrease in chloride content or replacement of chlorides by carbonates took place. Only occasionally were large soluble particles, other than sea salt, detected.
Abstract
Maritime air was followed from the coast, and measurements of seal-salt nucleus distributions were carried out. It was found that the concentrations encountered in air which had been over land for a considerable time ranged from very low values to values approaching those usually found in maritime air. It also seemed that convective cloud formation or precipitation rapidly lowered the salt concentration. In the absence of such factors, no appreciable diminution in total concentration occurred; vertical mixing, however, often gave rise to elevated salt concentrations at higher levels. Very low concentrations were found above post-frontal subsidence inversions over land, in air streams which had recently come from over the ocean.
Abstract
Maritime air was followed from the coast, and measurements of seal-salt nucleus distributions were carried out. It was found that the concentrations encountered in air which had been over land for a considerable time ranged from very low values to values approaching those usually found in maritime air. It also seemed that convective cloud formation or precipitation rapidly lowered the salt concentration. In the absence of such factors, no appreciable diminution in total concentration occurred; vertical mixing, however, often gave rise to elevated salt concentrations at higher levels. Very low concentrations were found above post-frontal subsidence inversions over land, in air streams which had recently come from over the ocean.
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The application of nonlinear iterafive algorithms to two-dimensional tomographic reconstructions is discttszed and a number of numerical examples are given, using as an illustrative basis reconstruction of the spatial distribution of liquid water in clouds from measurements of microwave attenuation. (The method, however, is not restricted to that specific problem and appears to be especially suitable for inversions involving a large number of unknowns.)
Abstract
The application of nonlinear iterafive algorithms to two-dimensional tomographic reconstructions is discttszed and a number of numerical examples are given, using as an illustrative basis reconstruction of the spatial distribution of liquid water in clouds from measurements of microwave attenuation. (The method, however, is not restricted to that specific problem and appears to be especially suitable for inversions involving a large number of unknowns.)
Abstract
By increasing droplet concentration and thereby the optical thickness of a cloud, pollution acts to increase the reflectance (albedo) of clouds; by increasing the absorption coefficient it acts to decrease the reflectance. Calculations suggest that the former effect (brightening of the clouds in reflection, hence climatically a cooling effect) dominates for thin to moderately thick clouds, whereas for sufficiently thick clouds the latter effect (climatically a warming effect) can become dominant.
Abstract
By increasing droplet concentration and thereby the optical thickness of a cloud, pollution acts to increase the reflectance (albedo) of clouds; by increasing the absorption coefficient it acts to decrease the reflectance. Calculations suggest that the former effect (brightening of the clouds in reflection, hence climatically a cooling effect) dominates for thin to moderately thick clouds, whereas for sufficiently thick clouds the latter effect (climatically a warming effect) can become dominant.
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Particles grown from molecular size by ultraviolet irradiation of initially particle-free air were found not to nucleate condensation at slight (∼1%) supersaturations until sufficient time had elapsed. By monitoring the size of the growing particles by use of Nuclepore filters a size/critical supersaturation relationship was obtained and compared with the predictions of nucleation theory. Substantial agreement with the theory resulted.
Abstract
Particles grown from molecular size by ultraviolet irradiation of initially particle-free air were found not to nucleate condensation at slight (∼1%) supersaturations until sufficient time had elapsed. By monitoring the size of the growing particles by use of Nuclepore filters a size/critical supersaturation relationship was obtained and compared with the predictions of nucleation theory. Substantial agreement with the theory resulted.
Abstract
Because of the nonlinearity of the coagulation equation the evolution of large drops by coalescence is likely to be very sensitive to liquid water content. This implies that a cloud containing pockets of high liquid water content can produce rain much more quickly than an identical cloud in which the liquid water content is uniform.
Abstract
Because of the nonlinearity of the coagulation equation the evolution of large drops by coalescence is likely to be very sensitive to liquid water content. This implies that a cloud containing pockets of high liquid water content can produce rain much more quickly than an identical cloud in which the liquid water content is uniform.
