Weekly Labs
- Lab 1 - Week 1
- Lab 2 - Week 2
- Lab 3 - Week 3
- Lab 4 - Week 4
- Lab 5 - Week 5
- Lab 6 - Week 6
- Lab 7 - Week 7
- Lab 8 - Week 8
- Lab 9 - Week 9
- Lab 10 - Week 10
- Lab 11 - Week 11
- Lab 12 - Week 12
- Lab 13 - Week 13
Meteorology 411 - Weekly Labs
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Week 5- Thermal Wind and Thickness
The name "thermal wind" is somewhat misleading since it is not an approximation to the real wind in the way that geostrophic or gradient winds are. However, thermal wind is a powerful concept because it shows how the wind shear is related to horizontal temperature gradients. Thermal wind is simply the difference vector between the geostrophic winds aloft and the geostrophic winds at some lower level. Its computation involves vector subtraction, so remember that you must break the geostrophic winds into u and v components to compute it. The thermal wind is oriented so that colder air lies to its left. The thermal wind can be used to explain why backing (veering) of geostrophic winds with height is associated with cold (warm) air advection. Thickness is simply the difference in heights between two pressure levels, and it is a function of the mean temperature. Thus, thickness and temperature are often used interchangeably. Most forecasters are aware of thickness because tools such as the 1000-500 mb thickness have long been used as a guide to where snow will fall instead of rain.
Look at the 700 mb map and pick a few locations where noticeable warm or cold (temperature) advection is occurring. Next, look at the 850 and 500 mb maps, and see if the geostrophic winds are backing or veering with height at these locations. Do your answers agree with theory? Estimate what the thermal wind vector looks like at each place. Look back at your 700 mb map. The thermal wind vector should roughly be aligned like the temperature contours. Remember that warm advection favors upward motion, and is therefore a region more favorable for cloud formation. Check the satellite image to see if cloudcover is occurring in the regions where you saw warm advection at 700 mb. |
