Edward Aguado

Climatic Fluctuations and the Timing of West Coast Streamflow

Abstract Since about 1950 there has been a trend in the California Sierra Nevada toward a decreasing portion of the total annual streamflow occurring during April through July, while the streamflow during autumn and winter has increase. This trend not only has important ramifications with regard to water management, it also brings up the question of whether this represents a shift toward earlier release of the snowpack resulting from greenhouse warming. Therefore, the observed record has been examined in terms of relative influences of temperature and precipitation anomalies on the timing of streamflow in this region. To carry out this study, the fraction of annual streamflow (called the fractional streamflow) occurring in November-January (NDJ), February-April (FMA), and May-July (MJJ) at low, medium, and high elevation basins in California and 0regon was examined. Linear regression models were used to relate precipitation and temperature to the fractional streamflow at the three elevations for each seas...

Use of April 1 SWE measurements as estimates of peak seasonal snowpack and total cold-season precipitation

Many previous studies of snow accumulation and ablation have been based on snow course data obtained at monthly intervals, using April 1 snow-water equivalents (SWE) as surrogates for the total seasonal accumulation and for the maximum seasonal snowpack on the ground. This article uses daily snow pillow data to determine how well the April 1 SWEs represent the total accumulation and the maximum snowpack within the entire Rocky Mountain region and in individual subregions. April 1 SWE tends to underestimate the peak SWE by ∼6 cm (12%). April 1 SWE provides a more accurate estimate of the total seasonal precipitation, with mean errors of approximately −1.7 cm (4%) for most of the study area and approximately +2 cm (6%) in the eastern portion. The error incurred by the use of April 1 SWE in the estimation of peak SWE does not vary systematically with elevation, but errors in the estimation of total seasonal precipitation do.

Effect of advected pollutants on solar radiation attenuation: Mojave Desert, California

Abstract During the summer, sea breezes advect high concentrations of pollutants from the Los Angeles Basin into the Mojave Desert during the afternoon. Clear-sky pyrheliometer and pyranometer data were obtained to determine the effect of the advected contaminants on the attenuation of solar radiation and its breakdown into direct and diffuse components. Even under the most extreme conditions, the amount of global radiation received is not reduced by more than about 7 per cent. On the other hand, reductions in the direct component can be as great as 140 W m−2, which are nearly compensated for by large increases (up to almost 300 per cent) in diffuse radiation. The spatial and temporal variability in the budgeting of global radiation into the diffuse and direct components calls into question the feasibility of estimating diffuse energy based on the ratio of global to extraterrestrial radiation.