Atmospheric Circulation Patterns

Unlike other features of the physical environment, the gases that constitute the atmosphere are invisible, so that it is necessary to use indirect means to describe graphically and to map continuously changing atmospheric conditions. Atmospheric motions are complex, but when studied they are found to follow patterns. To understand the weather regimes of the White-Inyo mountains, it is helpful to recognize three principal scales of motion, each roughly an order of magnitude greater than the next.

The first and largest of these is the synoptic scale , so called because it is analyzed from numerous soundings, measurements, and observations made at the same time at hundreds of locations around the world. This is the scale of the familiar weather maps seen in daily newspapers and on television. These surface and upper-air charts cover horizontal distances of 100 to 2,000 mi (160 to 3,200 km) and depict such features as low- and high-pressure areas, cyclones, and anticyclones, air masses, weather fronts, and regions of precipitation. Generally, these features progress in a predictable manner,

and from them it is possible to produce, by computerized prediction models, future patterns of airflow, moisture, temperature, clouds, and precipitation. These are used to forecast, with varying degrees of certainty, weather conditions for a particular region for a few days following receipt of the climatic data.

The second scale of atmospheric motion, the mesoscale , describes airflow patterns over distances of, say, 1 to 100 mi (or 1.6 to 150 km), a range that includes many of the spectacular cloud formations and weather conditions experienced in and near the mountains of eastern California (Plates 1.1–1.8). These phenomena are closely related to the synoptic flow patterns but are controlled and shaped by major terrain features such as the Sierra Nevada and the White-Inyo Range.

The third scale, the toposcale , applies to weather and climatic conditions within a distance of, say, 1 mi (1.6 km) that vary in relation to prominent features shown on local (15-minute or 7.5-minute series) topographic maps. Thus, under differing synoptic and mesoscale conditions different air temperatures, wind velocities, and snow accumulations are measured, whether the location is on a mountain ridge or in a canyon, on a windward or leeward slope, or in a broad valley.

In the sections that follow we discuss the principal patterns that affect the White-Inyo Range, its inhabitants, and its visitors in each of these different scales. We begin with a survey of synoptic-scale airflow and its relation to seasonal weather.