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California Content Standards - Science

Standard 4. Many phenomena on Earth's surface are affected by the transfer of energy through radiation and convection currents. As a basis for understanding this concept:

e. Students know differences in pressure, heat, air movement, and humidity result in changes of weather.

Weather

Vocabulary:

weather	water cycle	humidity	relative humidity
psychrometer	condensation	dew point	cloud
cumulus clouds	stratus clouds	cirrus clouds	precipitation
air mass	front	severe weather	thunderstorms
lightning	thunder	tornado	hurricane
weather forecast	thermometer	barometer	windsock
wind vane	anemometer	station model	isobars

Interpreting Upper Level Observation Symbols:

	Temperature: The value highlighted in yellow located in the upper left corner is the temperature in degrees Celsius. In this example, the reported temperature is -14 degrees. Temperature is defined as a measure of the average kinetic energy (or speed) of the molecules in the air.
	Dew Point Temperature: The value highlighted in yellow located in the lower left corner is the dew point temperature in degrees Celsius. In this example, the reported dew point temperature is -34 degrees. Dew Point Temperature is defined as the temperature at which air would have to cool (at constant pressure and constant water vapor content) in order to reach saturation. Dew points provide insight into the amount of moisture in the air. The higher the dew point temperature, the higher the moisture content for air at a given temperature. When the dew point temperature and air temperature are equal, the air is said to be saturated. Dew point temperature is NEVER GREATER than the air temperature. Therefore, if the air cools, moisture must be removed from the air and this is accomplished through condensation. This process results in the formation of tiny water droplets that can lead to the development of fog, frost, clouds, or even precipitation.
	Geopotential Height: The value highlighted in yellow located in the upper right corner represents the geopotential height in meters (m). Geopotential Height approximates the actual height of a pressure surface above mean sea-level. Therefore, for the example given above, the height of the pressure surface on which the observation was taken is 5800 meters. When a collection of geopotential height reports are contoured on a given pressure surface, we are able to identify upper air troughs and ridges, which are very important influences on surface weather conditions.
	Wind Barb: The symbol highlighted in yellow is known as a wind barb. The wind barb indicates wind direction and wind speed. Wind barbs always point in the direction the wind is blowing "from". As is the case of the diagram below, the orientation of the wind barb indicates winds from the Northeast.

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