ATSC-110L: Meteorology 1 Lab

Upper-Level Chart Analysis

Image Description: Pressure levels up to the tropopause. Start from the surface and move vertically upward. 1000 mb- surface station plots, see real-time weather, identify surface highs/lows. 850 mb - identify the movement of warm and cold air masses (cold air advection, warm air advection). 700 mb relative humidity. 500 mb - Freezing line; trough-ridge pattern (what we will be focusing on today). 200/300mb - Jet streaks and Jet streams; identify upper-level divergence/convergence. Above these levels is the tropopause.

Troughs & Ridges

Image Description: Drawing the axis of a trough and a ridge. Troughs are shaped like a "U", with a dashed line going through the center. This line will often have a slope (either positive or negative). Ridges are shaped opposite of a trough, with a squiggly line going through the center. In the image a trough with an axis line is drawn through North Dakota - Oklahoma. A ridge with an axis line is drawn through Ontario to the Gulf coast of Alabama/Mississippi.

The trough axis is denoted by a dashed line
The ridge axis is denoted by the squiggly line through the crest
Axes go in the middle of the curve!

Winds

Image Description: Winds around troughs/ridges. 500mb winds (kts) are plotted. A trough is located over the Dakotas region. This map highlights the counterclockwise rotation around the "U" shape of the trough. A ridge is located north of the Great Lakes region. This map highlights the clockwise rotation around the ridge pattern. Note: strongest winds in this map are over the Atlantic where the isobars are closest together. Weaker winds are located over the south east, where the isobars are more spaced out.

The strongest winds are when the isobars are closest together
Weaker winds when they are far apart
Winds blow counter-clockwise around a trough (cyclonic)
Winds blow clockwise around a ridge (anti-cyclonic)

Associated Temperatures

Trough = Colder Temperatures

Ridge = Warmer Temperatures

Image Description: Associated Temperatures with troughs/ridges. The 500mb temperature is plotted. A trough is located over the four corners region (southwest). This map is showing colder temperatures associated with the trough. These colder temperatures are within the "U". A ridge is located over the Ohio River Valley. This map is showing warmer temperatures associated with the ridge. These warmer temperatures are within the ridge pattern.

Upper-Level Convergence & Divergence

Upper-level divergence is found downwind of a trough
Upper-level convergence is found downwind of a ridge

Image Description: Upper-Level convergence and divergence. The image shows a wave-like pattern with ridges being the peaks, and troughs being the minimums. The order is trough, ridge, trough. Showing within the wave pattern is a pattern to upper-level convergence/divergence. The order being: convergence, divergence, convergence, divergence. The order for convergence aligns on the downwind side of a ridge, while the order for divergence aligns with the down wind side of a trough.

Jet Streaks

Looking at 200/250/300 mb maps are where we look for areas of enhanced flow, known as "jet streaks"
These jet streaks also have dynamics that can reinforce the ventilation of air aloft by having upper-level divergence
We break the areas of the jet streak into something called the "Four quadrant jet theory":
- Upper-level divergence: right entrance, left exit
- Upper-level convergence: left entrance, right exit

Four quadrant jet theory examples

Upper-level divergence: right entrance, left exit
Upper-level convergence: left entrance, right exit

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