Guided Notes on Guided Notes on Gathering Weather DataGathering Weather Data

Chapter 12, Section 3Chapter 12, Section 3

1.1. Meteorologists measure the Meteorologists measure the atmospheric variables of atmospheric variables of temperature, air pressure, wind, temperature, air pressure, wind, and relative humidityand relative humidity in order in order to make accurate weather to make accurate weather forecasts.forecasts.

2. Two of the most important 2. Two of the most important factors in weather forecasting factors in weather forecasting are are the accuracy and the the accuracy and the density of the datadensity of the data, which refers , which refers to the amount of data available.to the amount of data available.

3. Barometers measure 3. Barometers measure air air pressurepressure using mercury. using mercury. Changes in air pressure are Changes in air pressure are indicated by indicated by changes in the changes in the height of a column of mercuryheight of a column of mercury..

4. An anemometer is used to 4. An anemometer is used to measure measure wind speedwind speed and a and a hygrometer measures hygrometer measures relative humidityrelative humidity..

5. The National Weather Service 5. The National Weather Service in the U.S. has established a in the U.S. has established a surface observation network surface observation network across the countryacross the country, which , which gathers data in a gathers data in a consistentconsistent manner at manner at regularregular intervals. intervals.

What does a ceilometer measure and What does a ceilometer measure and estimate?estimate?

It measures the height of cloud It measures the height of cloud layers and estimates the amount layers and estimates the amount of sky covered by cloudsof sky covered by clouds

7. The weather that we 7. The weather that we experience is largely the result experience is largely the result of of changes that take place high changes that take place high in the tropospherein the troposphere. . Meteorologists must gather Meteorologists must gather atmospheric dataatmospheric data at heights of at heights of up to up to 30,000 m30,000 m..

8. A radiosonde is a 8. A radiosonde is a balloon-borneballoon-borne package of sensors that is used to package of sensors that is used to gather upper-level data. These gather upper-level data. These sensors measure sensors measure temperature, air temperature, air pressure, and humiditypressure, and humidity and are sent and are sent by radio signal to a ground station by radio signal to a ground station that tracks the movements of the that tracks the movements of the radiosonde.radiosonde.

9. Electromagnetic waves in a 9. Electromagnetic waves in a weather radar system are weather radar system are programmed to bounce off programmed to bounce off large large raindropsraindrops. The radar system . The radar system rotates in a rotates in a circlecircle, allowing , allowing meteorologists to gauge where meteorologists to gauge where rain rain is falling within the radar’s rangeis falling within the radar’s range..

10.Because the motion of moving 10.Because the motion of moving raindrops is caused by wind, raindrops is caused by wind, Doppler radar provides Doppler radar provides a good a good estimation of the wind speedsestimation of the wind speeds associated with precipitation areas, associated with precipitation areas, especially those experiencing especially those experiencing thunderstormsthunderstorms and and tornadostornados..

11.Cameras mounted aboard a 11.Cameras mounted aboard a weather satellite weather satellite take photos of take photos of Earth at regular intervalsEarth at regular intervals. Satellites . Satellites track track cloudsclouds, but not necessarily , but not necessarily precipitation. Scientists combine precipitation. Scientists combine data from radar and satellites to data from radar and satellites to determine where determine where both clouds and both clouds and precipitation are occurringprecipitation are occurring..

12.Some satellites use infrared 12.Some satellites use infrared imagery to detect imagery to detect differences in differences in thermal energythermal energy, which are used , which are used to map cloud cover or surface to map cloud cover or surface temperatures. temperatures.

13. Infrared images allow 13. Infrared images allow meteorologists to determine the meteorologists to determine the temperaturetemperature of a cloud, from which of a cloud, from which they can infer they can infer its type and its its type and its heightheight. This is especially useful in . This is especially useful in detecting detecting strong thunderstormsstrong thunderstorms that extend to great heights in the that extend to great heights in the atmosphere.atmosphere.

14. Because the strength of a 14. Because the strength of a thunderstorm is related to its thunderstorm is related to its heightheight, infrared imagery can be , infrared imagery can be used to establish used to establish a storm’s a storm’s potential to produce severe potential to produce severe weatherweather..