Soundings

What is a Sounding?

Used to plot the vertical distribution of temperature, dew-point, and pressure obtained by a radiosonde

It creates a vertical profile of the atmosphere!

Radiosondes can obtain data up to a height of around 30 km

Image Description: Radiosonde 1 Radiosondes are often called "Weather Balloons". It is shaped like a balloon and rises through the atmosphere with a tool that collects different atmospheric variables.

Image Description: Radiosonde 2 A person about to release a radiosonde standing in a snowy environment.

Skew-T Log-P Diagram

Skew-T = Isotherms (see left image below)

Lines of equal temperature that are slanted or skewed

Log-P = Isobars (see right image below)

Lines of equal pressure that are spaced logarithmically

Each data point is plotted and then connected with a line

Image Description: Skew-T Log-P (Isotherms)

Pressure (mb) is recorded to the left of the graph. Temperature (C) is recorded on the bottom (x-axis) and is repeated around the right y-axis.

*Note: the lines are of constant temperature, so whether you are looking at them from the x or y axis shouldn't matter, as each line has its value repeated.

Isotherms in this image are highlighted as teal diagonal lines, crossing the isobars

Image Description: Skew-T Log-P (Isobars)

Pressure (mb) is recorded to the left of the graph. Temperature (C) is recorded on the bottom (x-axis) and gets wrapped around the right y-axis.

Isobars in this image are highlighted as orange horizontal lines, crossing the isotherms

Example Sounding

Image Description: Skew-T Log-P Diagram Pressure is plotted on the vertical axis, with a logarithmic scale, and the temperature is plotted skewed at a 45° angle. the green line on the left represents the Dew-Point Temperature Td ; the line on the right represents the Temperature (T).

Reminder: Td should never be greater than T!

Important Features

Inversion: Any segment in the troposphere where temperature increases with height

Image Description: Important Feature (Inversion) This Skew-T Log-P diagram highlights how the temperature line (on the right in red) shows a positive slope up until a certain point. This positive slope in the temperature line is what represents the inversion Positive slope: increasing with height

Possible Cloud Layers: Any segments where the difference between the temperature and dew point temperature is 5ºC or less

Image Description: Important Features (Possible Cloud Layers) This Skew-T Log-P diagram highlights how the space between the Dew-Point (left in green) and Temperature (right in red) lines can help indicate cloud layers. If this space is less than 5ºC, then there is a possible cloud layer. This image shows approximately a 5ºC difference.

Freezing level: The level at which the temperature drops below 0ºC

If the entire temperature profile is below zero, the freezing level is reported at the surface (usually 100mb).

Image Description: Important Features (Freezing Level) This Skew-T Log-P diagram highlights how to find the freezing level given the temperature. Start at the 0ºC isotherm. Follow the skewed line to where it meets the recorded red line (representing temperature). Follow the isobar (horizontal line) to the edge of the graph and record the pressure level associated with it.

Tropopause Height: Boundary between troposphere and stratosphere, where the temperature increases with height.

Look just below where the temperature starts increasing at the top of the atmosphere

Image Description: Important Features (Tropopause Height) This Skew-T Log-P diagram highlights how the temperature line (on the right in red) shows a positive slope. This positive slope will continue to the top of the diagram. At the point of this inversion is the tropopause (boundary between the troposphere and stratosphere)

Wind Barbs

Winds can also be plotted on a sounding to visualize how wind is changing with height (see example sounding below)
Wind barb is the direction the wind is coming from, given in degrees

Image 1 Description: Wind Direction With respect to the Surface Station Model Center circle with a "+" in the center North is indicated as 0° East is indicated as 90° South is indicated as 180° West is indicated as 270°

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