Saturday, August 04, 2012

Clouds North Fife August 4th

Candy floss clouds North Fife today August 4th. We've been used to a rather rainy wet time but today it really had a feel of summer.
Put them on a stick and you could eat it.
Across the River Tay one can clearly see the flat bottomed cloud dewpoint, and precipitation. The dewpoint temperature is the temperature at which the air can no longer hold all of its water vapour, and some of the water vapour must condense into liquid water. The dew point is always lower than (or equal to) the air temperature. If the air temperature cools to the dew point, or if the dew point rises to equal the air temperature, then dew, fog or clouds begin to form. At this point where the dew point temperature equals the air temperature, the relative humidity is 100%. If there is then further cooling of the air, more water vapour must condense out as even more dew, fog, or cloud, so that the dew point temperature then falls along with the air temperature. While relative humidity is (as its name suggests) a relative measure of how humid the air is, the dewpoint temperature is an absolute measure of how much water vapour is in the air. In very warm, humid conditions, the dewpoint temperature often reaches 75 to 77 degrees F, and sometimes exceeds 80 degrees. No matter how hot the temperature gets, a dewpoint temperature of (say) 75 deg. F always represents the same amount of water vapour in the air. During the summer, the dewpoint temperature -- not the relative humidity -- is usually a better measure of how humid it feels outside. It is also a good measure of how much "fuel" is available to showers and thunderstorms, with a higher dewpoint representing more water vapour available for conversion to rain. Once when flying in a microlight I was amazed to see and feel the turbulent air currents boiling a few meters under the cloud base

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