Assignments

Williams: Preface, Introduction, Chapter 1

Zebrowski, Preface, Chapter 1 (point of view, definition of “disaster”)

Housekeeping

-received this morning’s weather map

Definition of Storm

We reviewed the definition of a storm once more.

Storm—Any organized (orderly, structured whole) disturbed state of the atmosphere, especially as affecting the earth’s surface and strongly implying destructive or otherwise unpleasant weather.

Today’s Weather Map

We then took a look at the weather map for this morning. It is a public consumption map, so only major observation sites have been plotted. Weather maps are drawn at least 24 hours a day because of frequent weather changes. The legend contains information such as surface level, ~~weather data, the date and time~~ wind speed and direction as well as temperature and dew point. This weather information is shared throughout the world.

Standard and Local Time

The international dateline runs through Greenwich, England, and serves as the starting point for longitudinal measurements—one direction being Easterly longitude and the other being Westerly. Local Universal Time (or Greenwich-Mean Time) is linked to the location’s longitude, and is measured in hours: one hour for every 15° longitude measured away from Greenwich, England. To obtain the Universal Time for California, for example, simply subtract 8 hours from Greenwich Mean tTime.

Weather Map Symbols

The different symbols shown on the map are in shorthand so that meteorologists can easily determine weather conditions.

Station Circles--The station circle helps us determine how cloudy that area was at the time of the observation. A fully colored in circle means that it was cloudy. An empty circle represents clear skies. If the circle is shaded 1/4, it was partly cloudy. If the circle is shaded 3/4, it was mostly cloudy.

Wind direction—The symbol connected to the station circle represents wind direction. If we visualize the symbol as an arrow that always points toward the station circle, we can see where the wind is coming from. For example, the weather map from February 2 illustrates the wind direction in San Francisco as a southeast wind.

Wind Speed—The lines that are drawn perpendicular to the wind direction symbol tells us the wind speed in miles per hour. A long line represents 10 mph, while a short line represents 5 mph. In addition, a flag represents 50 mph. The wind speeds are sustained winds (average winds over a long period of time).

Temperature—The number located in the top left corner of the station circle tells us the temperature at the observation time in Fahrenheit.

Signal of a Storm

In the state of Missouri, we noticed that if we draw arrows (called stream lines) that run parallel to the wind directions of the surrounding observation centers, we could see wind coming to a common point. Air converging to one spot is a signal of a storm. This is an example of organization in the definition of a storm.

Temperature Scales

We then looked at the temperature scales for Fahrenheit, Centigrade and Kelvin (the scale scientists use) to get a conceptual feel for temperature.

Composition of the Atmosphere

The earth’s atmosphere is 79% nitrogen, 20% oxygen, less than .1% carbon dioxide (yet it is still very important), and 1-4% water vapor (depending on where you are).

Visualize Temperature

In order to get a feel for what temperature is, we visualized many little balls floating in the room. If we were to look at the balls under a microscope, we would see them vibrating. It is this vibration that we perceive as temperature. The temperatures we feel is the body’s interpretation of the vibration of molecules. The hotter it is, the greater the vibration.