Notes for Meteorology 356

November 10, 2004

Sarah Rombawa

- Looked at the following sites:

o Diablo Winds and Fire Danger in Coastal California

§ Winds are “hot” because (focused on Section B. Only) surface:

1. Are in contact with a relative hot surface (deserts to the east);

2. Are sinking to sea level and therefore warmed compressionally.

§ Winds are “dry” (focused on Section B. Only) because surface:

1. Associated with “desert” air characterized by low dewpoints and a great difference between temps and dewpoints.

2. Associated with sinking to sealevel, thus further lowering relative humidity.

§ Winds are also associated with very strong surface winds speeds because:

A. Surface pressure difference between the interior and the coast are often extremely great (Dynamic Highs tend to be very strong.)

B. Wind direction is at right angles to the mountain ranges and tends to be “funneled by mountain passes and canyons. (Air accumulates east of mountains (higher pressure) and a net deficit of air occurs west of “break” through or over mountains, very high wind speeds occur, often far in excess of what may be evident from a glance at pressures differences seen on the large-scale weather map.

§ Discussed how these strong winds and other elements such as the dry and hot autumn season, fire watches occur in places such as Berkeley.

§ Briefly described the Berkeley Hills fire n 1991. Strong winds coming from the mountain ranges during this time of season ignited embers, thus causing the rapid spread of the fire.

o Rainfall Variability (characterized by climate change)

§ Defined: The degree to which rainfall amounts vary across an area or through time is an important characteristic of the climate of an area. Two types: Areal and Temporal

§ 1^st Type - Areal variability of rainfall

· Is across an entire area such as California.

· Has a specific time variable such as annually.

· Examined chart annual average precipitation, which shows California as having huge variations in rainfall amount and is not changing due to topography.

· Purpose of areal variability: Used by Water Resource Planning to find a huge source of rainfall in the area of California to build a damn or reservoir for the population residing in California. One such type of area would by close to Yosemite, where Hetch Hetchy was established.

§ 2^nd type – Temporal variability of rainfall:

· focused on one spot such as Downtown San Francisco, and how that spot changes across time.

· Purpose of temporal variability: Used by Water Resource Planning to plan the usage of the amount of water and making sure there is a dependable amount of water for the population residing that one spot.

o Measures of Temporal Precipitation Variability:

§ Examined way of measuring temporal precipitation:

· Average Value: (+) Add total rainfall for each year / divide by the number of years used.

· Extreme Values: Larges amount of rainfall (-) subtracted by smallest amount of rainfall.

· Average variation:

· Standard deviation: (not completely discussed in class, further information given on Friday) Best way of measuring precipitation.

· Analyzed seasonal rainfall by referring to the Downtown San Francisco & New York graph, which showed Downtown San Francisco as having variations of rainfall each year compared to New York, which had a continuous amount of rainfall every year.