Positive Energy Areas and Negative Energy Areas 

Within the atmosphere, there are areas of positive energy and negative energy that control stability. These areas may be connectively or mechanically induced. The type and size of these energy areas often determine the type of weather that will occur over a region. When a parcel of air lies in a stable layer within the atmosphere, energy has to be supplied to it if the air parcel is to move up or down. Such a layer is classified as a negative energy area (NEA).

When an air parcel lies in an unstable layer within the atmosphere, energy need NOT be sup-plied to get the parcel to move. The parcel moves upward freely because it cools adiabatically and remains warmer than the surrounding air. Such a layer is known as a positive energy area (PEA).

Refer to figure 6-2-11 to determine positive and negative energy areas pertaining to CONVECTIVE LIFTING. The procedure used in determining these areas is as follows:

1. Find CCL (moist-layer and/or parcel method).

2. From CCL, draw a line to the top of the chart paralleling the nearest saturation adiabat.

3. Draw a line from CCL to the surface paralleling the nearest dry adiabat.

4. Using a red pencil, shade in any area bounded by the temperature curve on the left and the drawn saturation adiabat on the right. These areas are the POSITIVE energy areas.

5. Using a blue pencil, shade in any area bounded by the temperature curve on the right and the drawn saturation adiabat on the left. These areas are the NEGATIVE energy areas. 

Refer to figure 6-2-12 to determine positive energy areas and negative energy areas that pertain to MECHANICAL LIFTING. The procedure for determining these areas is as follows:

2. From LFC, extend the saturation adiabat to the top of the chart.

3. Using a red pencil, shade in any area above LFC that is bounded by the temperature curve on the left and the saturation adiabat on the right. These are PEAs.

4. Using a blue pencil, shade in any area above LFC that is bounded by the temperature curve on the right and the saturation adiabat on the left. These are NEAs.

5. Below LFC, shade in blue the area bounded on the right by the temperature curve, on the left by the dry adiabat, up to LCL, and by the saturation adiabat on the left from LCL to LFC.

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