Tuesday, August 8, 2017

UW Soundings Generator

A couple recent notes about fog and smoke depended in the background on how the temperature of the air changes with increasing altitude above the surface.  Normally it is dropping at about 10ºC per 1,000 meters (5.5 Fº per 1,000 ft).  When it does not do that, but rather warms as it rises, we have a temperature inversion that can trap smoke or smog on the surface.  That is what was taking place over the recent fog discussion, and there is a nice way to view that, again from UW Atmospheric Sciences resources online. 

We used their Meteogram on the Fly, but they also have a Soundings on the Fly display (called Timeheights on the Fly) of their WRF model, which is one of the best forecasters for local weather.  Below is a sample of that.

These are complex diagrams of temp (red) and dew point (green) as a function of altitude expressed in terms of pressure.  Other such diagrams will also have altitude on the right in km.  They are called skew-t log-p diagrams because the temp scale is rotated 45º to the left and the pressure is on a log scale.   We will have notes on these diagrams later on.

The main observation here is the air temp is going up, not down, as it rises above the surface.  We can see this better in another source of these diagrams using plain GFS (not the WRF), shown below

This is from a powerful sounding generator link at rucsoundings.noaa.gov/gwt.  Here we see the km scale on the right.  This one can also be zoomed, along with other neat user operations.

Here we see the air rising in temperature up to about 3,700 ft.  Normally the air would rise from the surface roughly like the top part of the red line, where the temp drops with increasing altitude.  More on these diagrams later on. They are crucial to the prediction of squalls and storms.

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