Leonard O. Myrup

Spatial scales of current speed and phytoplankton biomass fluctuations in lake tahoe.

Spectral analysis of current speed and chlorophyll a measurements in Lake Tahoe, California and Nevada, indicates that considerably more variance exists at longer length scales in chlorophyll than in the current speeds. Increasingly, above scales of approximately 100 meters, chlorophyll does not behave as a simple passive contaminant distributed by turbulence, which indicates that biological processes contribute significantly to the observed variance at these large length scales.

A principal component analysis of sulfur concentrations in the Western United States

Abstract Data from a 40 site network of air samplers in the western United States were used in a principal components analysis to obtain spatial patterns of the inter-site correlations of sulfur concentrations. After rotation of the initial eigenvectors, two large regions were identified which accounted for 33.1% of the variance in the data. Three other smaller regions were identified which also had significant variance. The first eigenvector included all sites in the southern part of the network and was attributed to copper smelter emissions in Arizona and New Mexico. The second eigenvector included sites in the northern great plains and was attributed to episodic incursions of sulfur from the east. The third, fourth and fifth eigenvectors were attributed to locally important conditions.

The relationship of the extinction coefficient distribution to wind field patterns in southern California

Abstract The averaged distribution of the extinction coefficient, including its diurnal variation, in southern California is shown for commonly occurring winter and summer wind field patterns. The wind field patterns were generated by an objectively based method using empirical orthogonal function (EOF) analysis of the vector wind, similarity criteria and cluster analysis. For the days assigned to each pattern, averaged extinction coefficient fields were calculated for six diurnal periods. Three main winter and three main summer patterns were identified. Associated with the wind field patterns were distinctly differing extinction coefficient patterns. Transport of visibility reducing aerosols can be inferred by comparing the wind and extinction fields and their diurnal variation. Transport of visibility reducing pollutants from the Los Angeles Basin and San Joaquin Valley into the Mojave Desert and the south-western U.S. was shown to be highly persistent in summer, while only sporadic in winter. The San Joaquin Valley was identified as having a significant potential for additional visibility impacts in the southwest with higher emissions of visibility affecting pollutants associated with the increasing urbanization of the valley. The analysis illustrated a technique for organizing large wind data sets into a reasonable number of patterns. The clear and consistent relationship between the extinction and wind fields demonstrates the usefulness of this technique in air pollution analysis.

Aerosol Transport in the Southern Sierra Nevada

Abstract Aerosol transport and meteorology were investigated during 10 days in August 1985, at three elevations in the southern Sierra. Ground weather station and pilot balloon data revealed the diurnal variation of the topographic winds to be remarkably similar from day to day unless disrupted by synoptic meteorological events. Vertical aerosol and meteorological profiles were collected up to 250 m above ground level at one of the study sites using tethered balloon systems. Afternoon aerosol concentrations and horizontal fluxes were significantly higher than those in the morning and evening. No vertical gradients in aerosol concentration were detected expect during the evening profiles for coarse aerosols.

Use of Temporal Principal Components Analysis to Determine Seasonal Periods

Abstract Temporal principal components analysis was applied separately to monthly long-term wind, temperature, and precipitation data for Southern California. Physical explanations of the significant eigenvectors are presented. Cluster analysis of the component loadings was then used to form groups of months (seasons) having similar spatial patterns. The resulting groupings of months differed from the conventional definition of seasons. The wind and temperature analyses grouped the same months, with long summers, moderately long winters, short springs, and very short autumns. The precipitation analysis formed a long season, including the winter months, representing synoptic systems occasionally passing through the area, a summer thunderstorm season associated with influx of moisture from the south, and dry transitional periods separating these seasons. The purpose of the analysis was to pregroup two years of hourly wind data to remove most of the annual signal before applying spatial eigenvector analysis ...

Diffusion from a line source in an urban atmosphere

Abstract A model for the diffusion of material from a line source in an urban atmosphere is presented. The plume is assumed to have a well-defined edge at which the concentration falls to zero. The vertical wind shear is accounted for by using a power law, the exponent of which is explicitly determinable as a function of surface roughness characteristics of the terrain and the stability of the atmosphere (Monin-Obukhov length, L). The concentrations estimated from the model compare favorably with the field observations of other investigators.

Surface layer transport of sulfate particles in the western United States by the large-scale wind field

Abstract The transport patterns of fine sulfur aerosols in the western United States are shown. The large-scale resultant horizontal flux was computed in terms of that contributed by the mean flux versus that contributed by a turbulence, or eddy, component. The large-scale eddy component of the resultant flux is shown to be important in many cases. In the northern Great Plains the eddy flux often has a greater magnitude than the mean flux and its direction is from the east, opposite the mean flux. In the southwestern United States, the transport is accomplished primarily by the mean flow and the direction is from the south. This indicates that high sulfur concentrations are carried into the northern Great Plains from the east as periodic episodes, while high concentrations in the south are caused by sources to the south which are within the mean flow field.

A technique for determining regional scale flow and precipitation patterns upwind of a receptor site

Abstract A method of analyzing spatial flow and precipitation patterns associated with long-range transport is presented. This technique uses hourly precipitation data and model-calculated mixed layer trajectories to determine these patterns upwind of a receptor site. Precipitation is determined at hourly points along trajectories in a statistical sense using estimates of error in long-range trajectory calculations. This technique is used in seasonal analyses of fine particle concentrations at a remote northern Great Plains sampling site during summer 1980. The analyses show that there are distinctly different flow and precipitation patterns during high and low fine particle concentration periods. Highest fine sulfur particle concentrations occurred when flow was from the south with a higher frequency of precipitation. Highest fine soil particle concentrations occurred when precipitation frequencies were lower.