Sunday, July 19, 2020

The Hidden Beauty of Atmospheric Water Vapor

In many ways, meteorologists are in the art business, because many images produced by our models and observing systems are simply beautiful in their own right.  Many could be framed and would provide esthetic pleasure to most viewers.

Perhaps among the most beautiful types of meteorological imagery are the satellite depictions of atmospheric water vapor.  Let me show you.

Water vapor is a clear gas that is invisible to the naked eye.

When you see a typical satellite image in the visible part of the spectrum (example below from today), you see the light from the sun reflected off the surface and clouds.   Water vapor in the atmosphere does not interact with visible light and so you can't see it. 

Water vapor does interact with radiation in the infrared portion of the electromagnetic spectrum, where it both absorbs and emits radiation.

NOAA GOES weather satellites have the capability of viewing the emission of water in the atmosphere.  In fact, the latest GOES satellites can look at water vapor in three wavelengths, which can tell us about the amount of water vapor in the upper, middle, and lower portions of the atmosphere (mostly in the troposphere, the lowest layer of the atmosphere where all the weather takes place.

For example, here is the water vapor in the upper part of the atmosphere (6.2 micron wavelength, micron is a millionth of a meter), with blue being small values and green the most.  All kinds of amazing swirls associated with atmospheric circulations.  Lots of moisture in the tropics and dry zones in the subtropics.

Using a slightly longer wavelength (6.9 microns) we can see water vapor in the middle portion of the troposphere (using roughly 6.9 microns).  In this image, the driest air includes the yellows and orange colors, with green colors being very moist.   Stunning image.



These images are impressive even in black and white, as illustrated by the water vapor image on July 12th.  You can see an upper level cyclone north of Hawaii (the swirl of clouds) and the very, white blobs associated with thunderstorms.


Knowing about these structures are very useful for meteorologists--telling us about circulations not apparent in other wavelengths.   And the water vapor structures can be used to inform our numerical weather prediction models regarding the three-dimensional structure of the atmosphere, which contributes to better forecasts.

Both beautiful and practical:  it doesn't get much better than that!

6 comments:

  1. It needs to be combined into a false color image with each of the wavelengths mapped to respective RGB channels, kind of like Landsat.

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  2. It's quite muggy today in western Whatcom County. I measured a maximum dew point of 69F at my location in NW Bellingham - tied with a measurement from June 2019 for highest dew point in my POR.

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  3. Great pictures, thanks for posting these. There's nothing that can quite match the natural beauty found in the atmosphere.

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  4. The maximum temperature at my location in NW Bellingham today was 79F - the warmest since 5/10.

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  5. Yes, it is beautiful! Blows me away!

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  6. I use GOES 17 water vapor imagery to plan astro imaging trips.

    If I see an influx coming into our region, I may go to a different area or plan my observing sessions taking the potential seeing degradation into account.

    Last night and this morning were actually good for here with stable low level winds and low WV levels up high.

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