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- Author or Editor: Richard G. Semonin x
- Journal of Applied Meteorology and Climatology x
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Abstract
Millipore filter samples obtained at the Mauna Loa Observatory and at Hillo, Hawaii, were analyzed for chloride particle concentrations. These data are used in a transport model to determine the removal efficiency of particles.
The most interesting result from the analysis is that the percentage of particles removed is uniform from the shore to the mountain observatory regardless of size. These results lead to calculations of the impaction-sedimentation ratio which range from 212 for 20μm diameter particles to 6413 for 4μm particles. The total impaction factors (removal by trees and other vegetation) ringed from 0.267 to 0.323 along the 60-km path.
Abstract
Millipore filter samples obtained at the Mauna Loa Observatory and at Hillo, Hawaii, were analyzed for chloride particle concentrations. These data are used in a transport model to determine the removal efficiency of particles.
The most interesting result from the analysis is that the percentage of particles removed is uniform from the shore to the mountain observatory regardless of size. These results lead to calculations of the impaction-sedimentation ratio which range from 212 for 20μm diameter particles to 6413 for 4μm particles. The total impaction factors (removal by trees and other vegetation) ringed from 0.267 to 0.323 along the 60-km path.
Abstract
To investigate the hypothesis that dust storms enhanced the calcium concentrations in precipitation in the mid-1950s, two case studies were performed for major dust events in the southern Plains of the United States during March and April of 1981. Forward trajectories were calculated from source areas of blowing dust and then compared with hourly radar summaries to see if the advected dust cloud intercepted precipitation over sites of the National Atmospheric Deposition Program. Four sites met these criteria between the two case studies and exhibited extremely high calcium concentration and deposition values for the study period.
Abstract
To investigate the hypothesis that dust storms enhanced the calcium concentrations in precipitation in the mid-1950s, two case studies were performed for major dust events in the southern Plains of the United States during March and April of 1981. Forward trajectories were calculated from source areas of blowing dust and then compared with hourly radar summaries to see if the advected dust cloud intercepted precipitation over sites of the National Atmospheric Deposition Program. Four sites met these criteria between the two case studies and exhibited extremely high calcium concentration and deposition values for the study period.
Abstract
Observations showed increased concentrations of cloud condensation nuclei (CCN) in air samples collected over and downwind of St. Louis when compared to upwind samples. Aircraft observations of urban clouds showed corresponding increased concentrations of cloud base droplets. In addition, observations indicated higher cloud bases and decreased elevations of average first echo base heights in the St. Louis/East St. Louis area as compared with similar clouds over rural areas.
The purpose of this paper is to examine the possible role of CCN chemical composition and number concentration in producing the observed phenomena. A closed parcel model of condensation and collection was employed for this purpose. The results suggest that the observed differences of depth from cloud base to first echo height between urban and rural clouds do not result from concentration differences in any CCN size range. Results of model calculations also suggest that variations in chemical composition of the largest CCN (≥1.0 μm radius) were not responsible for the observed urban/rural differences. A hypothesis based on observations and model results is presented for explaining the observed differences in cloud base to first echo depth in terms of differences between the evolution and strength of updrafts in urban and rural clouds.
Abstract
Observations showed increased concentrations of cloud condensation nuclei (CCN) in air samples collected over and downwind of St. Louis when compared to upwind samples. Aircraft observations of urban clouds showed corresponding increased concentrations of cloud base droplets. In addition, observations indicated higher cloud bases and decreased elevations of average first echo base heights in the St. Louis/East St. Louis area as compared with similar clouds over rural areas.
The purpose of this paper is to examine the possible role of CCN chemical composition and number concentration in producing the observed phenomena. A closed parcel model of condensation and collection was employed for this purpose. The results suggest that the observed differences of depth from cloud base to first echo height between urban and rural clouds do not result from concentration differences in any CCN size range. Results of model calculations also suggest that variations in chemical composition of the largest CCN (≥1.0 μm radius) were not responsible for the observed urban/rural differences. A hypothesis based on observations and model results is presented for explaining the observed differences in cloud base to first echo depth in terms of differences between the evolution and strength of updrafts in urban and rural clouds.
