Ozone

This is my attempt to explain some of the variables in this data set. I am not an atmospheric scientist nor have I ever pretended to be one. These notes come courtesy of some web sites and vague recollections of college physics. (See http://www.britannica.com/bcom/eb/article/7/0,5716,73497+1,00.html.)

These data are for 330 days in 1976. All measurements are in the area of

Upland, CA, east of Los Angeles.

Name Type n Info

Height Variate 330 Vandenburg 500 millibar height (m)

Humidity Variate 330 humidity, percent

InversionHt Variate 330 Inversion base height, feet

Ozone Variate 330 Ozone conc., ppm, at Sandbug AFB.

Pressure Variate 330 Daggett pressure gradient (mm Hg)

Temp2 Variate 330 inversion base temperature, degrees F.

Temperature Variate 330 Temperature F. (max?).

Visibility Variate 330 Visibility (miles)

WindSpeed Variate 330 wind speed, mph

Suppose it is a clear night. The ground quickly loses its heat and its possible for the air near the ground to cool more rapidly than the overlying air. When this happens, a phenomenon takes place that is the inverse of what we expect: the air temperature increases as altitude increases. This phenomenon is called an inversion layer. At one height, this trend changes, and the air begins to become colder with altitude, and this height is called the inversion base height. Because cold air is heavier than warm air, the effect is that this overlying layer of cold air acts as a lid and traps the air down below it. This usually means that it gets even hotter below, and also means smog and gasses get trapped down below.

Hear in LA, the ocean usually provides another source for cooling the ground. So when cooler air comes in from the sea, and the sky is clear, conditions are ripe for an inversion layer.

If a Santa Ana blows, well then I don't really know how this might affect an inversion layer, but probably it would diminish or end it. Wind generally (to a good approximation) flows from high pressure zones to low pressure zones. The Daggett Pressure Gradient is a measure of the difference between the air pressure at Upland and the air pressure at a field station in Daggett, which is near Barstow. So if the pressure is higher in Daggett, then probably we have Santa Ana winds blowing. The problem is that I don't know whether a "+" sign means its higher pressure in Daggett or at Upland. Most likely, according to my sources, a + sign means the pressure is higher at Upland.