Weather Instruments

A Thermometer measures air temperature. A Thermometer works because matter expands when heated. Most thermometers are closed glass tubes containing liquids such as alcohol. When air around the tube heats the liquid, the liquid expands and moves up the tube. A scale then shows the actual temperature of the air.

Thermometers This also has a Hygrometer, which measures humidity.

A Barometer measures air pressure. An Italian scientist named Torricelli built the first barometer in People still use barometers based on Torricelli's design to measure air pressure.

Barometers Torricelli’s Barometer

A Psychrometer measures relative humidity. Two thermometers are used in a Psychrometer. A wet cloth covers the end of one of the thermometers. Water evaporates from this cloth, causing the temperature on that thermometer to be different from the other.

A Psychrometer If the surrounding air is dry, more moisture evaporates from the wick, cooling the wet-bulb thermometer more so there is a greater difference between the temperatures of the two thermometers. If the surrounding air holds as much moisture as possible - if the relative humidity is 100% - there is no difference between the two temperatures.

Psychrometers See the wet “wick” on one of these bulbs. One of these bulbs should have a piece of wet cheesecloth on it.

An Anemometer measures wind speed. The cups catch the wind, turning a dial attached to the instrument. The dial shows the wind speed. Wind speed can be estimated without special tools by observation.

Anemometers

A Windsock is used at airports to indicate wind direction for takeoffs and landings. They help the pilots select the proper runway so that they can take off and land into the wind.

Windsocks

A Wind Vane is used to measure wind direction. It spins on a rod and points in the direction from which the wind comes.

Wind Vanes Most airport Wind Vanes have Anemometers also.

A Hygrometer is an instrument used to measure the humidity of the air. A mechanical Hygrometer uses human or horse hairs which stretch as they absorb moisture.

Hygrometers

A Rain Gauge is used to measure amount of rainfall. An official Rain Gauge consists of a large cylinder with a funnel and a smaller measuring tube inside.

Rain Gauges

A Weather Balloon measures weather conditions higher in the atmosphere. Measures temperature, air pressure, wind speed and direction

Weather Balloons Sometimes weather balloons land in the oddest places!

A Weather Satellite is able to photograph, track, and measure the conditions of large-scale air movements. A meteorologist then compiles and analyzes the data with the help of computers. NOAA weather satellite launched in 2005.

Weather Satellites Weather Satellite Image Tiros First usuable Tiros 1 image NOOA-M measures information about Earth radiation, sea and land surface temperature, atmospheric vertical temperature, water vapor, and ozone in the troposphere and stratosphere.

Weather Prediction All these instruments are used by meteorologists to report the current and predict the future weather. The End.

Weather Maps

Much information is needed to interpret what is happening with the atmosphere. Need to condense this information in a small space Need to show the geographic characteristics of this data Weather maps can both display this data and summarize the patterns

Station Model Allows the data to be plotted in a condensed and usable format

Location of the station on the map. The name of the location or airport abbreviation might be given nearby.

Temp Temperature information in degrees Fahrenheit.

Temp dewpt Dew Point Temperature in degrees Fahrenheit.

Temp dewpt Wind direction A staff is rotated around the station. Remember, winds are identified as the direction FROM which they come. This would be a west northwest wind or about 290º.

Temp dewpt Wind Speed Attached to the staff are symbols for speed.

The coding for the wind speed symbols can be generalized as: half staff about 5 knots note, it is not on the end of the wind direction staff full staff about 10 knots these are additive for the total amounts three full staffs=30 knots flag about 50 knots 65 knots

Temp dewpt pressure Current Barometric Pressure

Barometric Pressure is VERY important! average barometric pressure at sea level is mb. current barometric pressure is reported to the nearest TENTH BUT, they don’t want to waste space

average barometric pressure at sea level is mb. barometric pressure varies around this value somewhat higher somewhat lower + about 30 = about 30 = 983

average barometric pressure at sea level is mb. barometric pressure varies around this value they do not PRINT the beginning number or numbers they, also, do not PRINT the decimal point, but report to the nearest TENTH x 133

From the three numbers, you must INTERPRET whether the preceding value is 10 or 9 Which would make the value most realistic?

add the decimal point and then consider which, a 10 or a 9 places the value NEAREST to the average pressure of mb.

(1013.3) What is the pressure?

Not only is the pressure itself important, but so is the way the pressure has been changing. So, more information may be given and must be coded.

Temp dewpt pressure trend How has the barometer been changing? + it is higher now than in the past - it is lower now than in the past

Temp dewpt pressure trend change How much the pressure has changed the amount of change in the past three hours again, reported in TENTHS without the decimal

Temp dewpt pressure trend change shown What has the pressure been doing? Shown diagrammatically

Temp dewpt pressure trend change shown Total amount of cloud graphic depiction of percentage of the sky covered by clouds

no clouds about 10% about 25% about 40% about 50% about 60% about 75% about 80% completely overcast sky obscured

Temp dewpt pressure trend change shown low clouds middle clouds high clouds Symbol positions to identify the cloud types Cloud types tell much about the weather conditions. The cloud types are identified by symbols, and classed as low, middle, and high clouds.

Temp dewpt pressure trend change shown low clouds middle clouds high clouds low or middle cloud cover How much of the sky is covered by low and middle cloud cover? What amount, in tenths, of the sky is covered by low or middle clouds. This is a coded number with the percentage close to the printed number.

Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow What is the present weather? The current weather is very important. A detailed set of symbols provides weather descriptions. low or middle cloud cover

Samples of present weather symbols. fog haze thunderstor m, drizzle lightning rain * snow slight rain showers. ice or snow pellets cloud development not observed

intermittent rain, slight at time of observation continuous rain, slight at time of observation intermittent rain, moderate at time of observation continuous rain, moderate at time of observation intermittent rain, heavy at time of observation Combining symbols tells more of the detail. continuous rain, heavy at time of observation

100 different symbols provide details about the PRESENT WEATHER.

Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow visibilit y The visibility is especially important for pilots. Visibility is given in miles and fractions low or middle cloud cover

The past weather uses symbols. Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow visibilit y low or middle cloud cover PAST, *

Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow visibilit y low or middle cloud cover PASTwhen Time precipitation began or ended Coded for how many hours ago the precipitation began or ended. Again, the code is close to the number of hours.

Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow visibilit y low or middle cloud cover PASTwhen base Height of cloud base Coded height of base of clouds. Important for pilots.

Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow visibilit y low or middle cloud cover PASTwhen base amount The amount of precipitation Amount of precipitation is plotted in inches to the nearest hundredth of an inch.

Decode this station ,,

,, temperature dew point wind direction wind speed amount of sky cover any low clouds? any middle clouds? any high clouds? amount of low and middle clouds height of cloud base visibility barometric pressure trend in pressure pressure three hours ago how has pressure changed present weather past weather when precipitation began/ended amount of precipitation south 25 knots 80% yes mile mb falling down then steady continuous slight drizzle rain 4.36”