State of the Atmosphere (What do scientists measure when they talk about the weather?)

What do scientists measure? Temperature Dew point Air pressure Wind speed Relative humidity

Temperature vs. Heat Temperature is a measurement of how rapidly or slowly molecules moves around. More molecules in a smaller space moving around quickly will give you a higher temp. Instrument used: Thermometer Heat, on the other hand, is the transfer of energy that occurs because of a difference in temperature between substances. Heat flows from an object of higher temperature to an object of lower temperature. Instrument used: usually a thermometer

How are Temperature and Heat related? Heat is the transfer of energy that fuels atmospheric processes, while temperature is used to measure and interpret that heat.

Dew Point Dew Point is the temperature to which air must be cooled at constant pressure to reach saturation. Short and sweet: Dew Point is the temperature at which condensation forms. Instrument used: Hygrometer

Air Pressure and Density As we know, air pressure is the amount of atmospheric weight that is weighing down on something at a given time. The closer you are to the bottom of the atmosphere (land) the more air particles you have weighing down on you – thus, the more air pressure you have weighing down on you. The higher you go in the atmosphere, the less air pressure there is because there are less air particles. Instrument used: barometer

Density Density works the same way as air pressure. The closer you are to land (at the bottom of the atmosphere) the more gases at the top of the atmosphere pressing down on the air below – thereby, compressing the particles and increasing the density of air.

Pressure-Temperature-Density Relationships In the atmosphere, temperature is directly related to pressure. The higher the temperature, the higher the pressure. The higher the pressure, the higher the temperature. The relationship between temperature and density is inversely proportional. As temperature increases, density decreases. As temperature decreases, density increases. This is why air rises when it’s temperature increases, it becomes less dense.

Wind In simple terms, wind is created as air moves from areas of high pressure to areas of low pressure. In the atmosphere, cool air, being more dense, sinks and forces warm, less dense air upward. The air in the atmosphere moves in response to density imbalances created by unequal heating and cooling of the earth’s surface. Instrument used: anemometer

Humidity Humidity – the amount of water vapor in the air. Relative Humidity – the amount of water vapor that a column of air can hold. Expressed in a percentage (%). If there is 100% relative humidity, a column of air is filled to the brink with as much water as it can take. Instrument: sling psychrometer or a hair hygrometer