In your reading of the AG2 manual, volume 1, you became familiar with the terms convergence, divergence, and vorticity when used in relation to surface lows and highs. You were also presented with a basic understanding of the principles involved In this section, we will cover the terms, the motions involved in upper air features and surface features, and the relationship of these processes to other meteorological applications,

We will first discuss convergence and divergence, followed by a discussion of vorticity.

The World Meteorological Organization adopted "hectopascals" (hPa) as its standard unit of measurement for pressure. Because the units of hectopascals and millibars are interchangeable (1 hPa = 1 mb), hectopascals have been substituted for millibars in this TRAMAN.

CONVERGENCE AND DIVERGENCE

LEARNING OBJECTIVES: Define the terms convergence and divergence. Recognize directional and velocity wind shear rules. Recognize areas of mass divergence and mass convergence on surface pressure charts. Identify the isopycnic level. Retail the effects that convergence and divergence have on surface pressure systems and features aloft. Identify rules associated with divergence and convergence.

As mentioned in the AG2 manual, volume 1, unit 8, convergence is the accumulation of air in a region or layer of the atmosphere, while divergence is the depletion of air in a region or layer. The layer of maximum convergence and divergence occurs between the 300- and 200-hPa levels. Coincidentally, this is also the layer of maximum winds in the atmosphere; where jet stream cores are usually found. These high-speed winds are directly related to convergence and divergence. The combined effects of wind direction and wind speed (velocity) is what produces convergent and divergent airflow.

CONVERGENCE AND DIVERGENCE (SIMPLE MOTIONS)

Simply stated, convergence is defined as the increase of mass within a given layer of the atmosphere, while divergence is the decrease of mass within a given layer of the atmosphere.

For convergence to take place, the winds must result in a net inflow of, air into that layer. We generally associate this type of convergence with low-pressure areas, where convergence of winds toward the center of the low results in an increase of mass into the low and an upward motion. In meteorology, we distinguish between two types of convergence as either horizontal or vertical convergence, depending upon the axis of the flow.

Winds in this situation produce a net flow of air outward from the layer. We associate this type of divergence with high-pressure cells, where the flow of air is directed outward from the center, causing a downward motion. Divergence, too, is classified as either horizontal or vertical.

This information is now available on CD in Adobe PDF Printable Format

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing