Notes for Meteorology 356

October 25, 2004

Julie Arden and Nathan Maas

Assignments: Week of October 25, 2004

* Homework 2 due Friday, October 29.

Housekeeping:

Making sure everyone in class had done the class notes at least once.

Information covered:

We first looked at an infrared picture (10 UMT, Oct. 25), including the East Pacific and most of North America. It showed thunderstorms on the Northwest coast with tops reaching altitudes ranging from 18,000 to 20,000 feet. It also showed the remnants of a hurricane moving east over Mexico.

We then looked at a 500mb (1200 UMT, Oct. 25), which showed the jet stream following the isobars, coinciding with the cloud movement and placement on the infrared picture. It also appears that the Lows are following the jetstream, moving along the storm-track.

Next, we discussed the heavy October rainfall we have experienced thus far, and how we may have the wettest Oct. for San Francisco in 32 years. The wettest recorded October here was in 1962, when 8" fell. This is unusual, but does not signify a climatic change or a wet year.

Air that rises cools because it expands as it moves upward into less pressure. If the relative humidity is less than 100%, the cooling rate is about 5.5 degrees Fahrenheit per 1000 feet.

The higher the dewpoint, the higher the rainfall, because both are being cooled to their dewpoint.

For every 10 degrees we raise the dewpoint, the rainfall DOUBLES.

Q: If the air in two regions with high relative humidity is experiencing rising motion, and in one region the dewpoints are quite low, and in the other region they are quite high, in which of these two regions would you expect more precipitation?

A: The higher the dewpoint, the more rainfall, since both are being cooled to the dewpoint.

Ground fog (Tule fog) = Radiation fog. This is what is often seen in horror movies.

Rocks are made of minerals which are comprised of different metals. Metal absorbs heat in the daytime and releases it as the temperature cools. These two facts explain why continents (in the Northern Hemisphere) heat up during the summer and cool down in the winter. Meanwhile, water does not behave quite the same, so in the summer, the land is hotter than the ocean in the daytime, but cooler than the ocean at night.

We also briefly covered tides, with the highest in January and the lowest in July. The high winter tides prevent rainfall runoff, increasing chances for flooding.