Weather Instruments

1. Weather Instruments P 611-614

2. We need data to forecast the weather • Temperature • Air pressure • Humidity • Type of clouds • Level of precipitation • Wind direction and speed

3. Instruments used to gather the data • Lower Atmospheric Conditions Temperature • Thermometer • Uses a liquid either mercury or alcohol sealed in a glass tube • Electrical thermometer • As temp rises the electrical current increases • A thermistor responds very quickly and is used where temps change quickly

4. Air pressure Barometer • Aneroid (pictured) • Mercury • fronts are usually indicated by a drop in air pressure

5. Wind Speed and direction • Anemometer • Wind speed • Wind vane • Wind direction

6. Rainfall • Rain gauge

7. Measuring Upper Atmospheric Conditions

8. Doppler image of a hurricane

9. Radar Stands for radio detection and ranging • Uses reflected radio waves Doppler radar • Can indicate precise location, intensity of precip and extent of a storm • Shows wind patterns • Towards or away from the radar

10. Radiosonde • An instrument package that is carried by a helium-filled balloon • Radio sends info to ground • Determines direction and speed of high altitude winds

12. Skew-T • Shows a vertical slice of the atmosphere • Temperature on right • Dew point on left • Air pressure • Wind speed and direction

14. Weather Satellites Can measure • visible • Infrared • Ocean conditions • temperature and flow of ocean currents and • height of ocean waves

15. Computers • Solve mathematical equations that describe the behavior of the atmosphere • Can store weather data • Can store weather records

16. This info is reported from stations • WMO World Meteorological Organization • 10,000 land based stations and hundreds of ship-based stations • Weather satellites • GOES Global Orbiting Earth Satellite

17. Data from stations is compiled and analyzed to forecast • In the past this was done by hand • Now much is done by computer • But, different programs work better for different locations and types of weather • Often two or three computer models are consulted to make one forecast

18. Weather Station Symbols • Temperature is upper left corner • Barometric (air) pressure is upper right

19. Air pressure • represents the last three digits of the observed pressure reading in millibars (mb) • Like on previous labs

20. Dew point • Dew Point is lower left corner • When the air temperature and the dew point are the same the air is saturated • Relative humidity can be inferred • High if temp and dp are close • Low if large difference between dp and temp

21. Relative Humidity can be inferred • When the air and dew point temperatures are very close, this indicates that the air has a high relative humidity. • The opposite is true when there is a large difference between air and dew point temperatures, which points to air with a low relative humidity.

22. Wind Speed and Direction • Wind stick points in the direction "from" which the wind is blowing • Which direction is the wind from?

23. Wind Speed • May be measured in mph, km/hr or knots • The more barbs the windier it is • Each long barb is approx 10 knots

25. Cloud Cover

26. Precipitation Symbols

27. Worksheets Surface Weather Map • Study the tables and the station model • Use the info to answer the questions Transparency worksheets • Study the tables and the station model • Use the info to answer the questions

28. Dry Line • Note the sharp difference in dew points • The line that separates dry air from moist air

29. Isobars • Lines that connect points with equal air pressure • Drawn at 4 mb (millibar) intervals

30. Pressure and Wind Relationships • Draw isobars • Use pencil • CI = 4 • Mark high and low pressure • Answer the questions

31. Methods of Forecasting • Persistence • Trend • Analog

32. Persistence • Persistence—based on continuity of a weather pattern—if it is raining now it will probably be raining tomorrow

33. Trend • Trend—based on the movement or trend of the weather system Ex. Cold front moving E at 20 Km/hr will affect weather 80 KM away in 4 hours

34. Happy Birthday, Hoang

35. Others Climatology—data accumulated through many years 4th of July is usually hot and dry Numerical Weather Prediction—uses programs built by meteorologists Not exact compares present weather (cloud cover, wind, temperature, humidity, etc) with weather conditions produced by same features in the past Analog

36. Meteorologists What high school courses are necessary to prepare for a career in meteorology? • Because meteorology is a science, a good background in mathematics and the sciences is mandatory. Knowledge of physics and chemistry is helpful toward a career in the atmospheric sciences.

37. OU is the Best for Meteorology

38. Weather Station Symbols • Temperature is upper left corner • Barometric (air) pressure is upper right

39. Lab • Do isotherms in red (every 2) • Do lightly in pencil first • Do isobars in blue (Every4) • Do lightly in pencil first

40. Winds

41. Three causes of motion(recap) WIND ALWAYS FLOWS FROM HIGH TO LOW PRESSURE 1. Warm air rises and cool air sinks because of density • This is called a convection current 2.pressure differences in the atmosphere that are a result of temperature differences • Wind is horizontal air movement 3. The deflection of objects to the right in the northern hemisphere—called the Coriolis Effect • Due to rotation of the earth

42. Winds blow from high to low pressure.

43. Highs and Lows? • Winds circle Clockwise around a high • Highs generally mean cold dry air that is sinking • High pressure usually = fair weather

44. Low Pressure Systems • Winds circle counterclockwise around a low • Warmer air rises and cools and forms clouds and precipitation • Low pressure usually = rainy weather

45. Global Circulation Patterns • We are located in theWesterlies section • That means our weather moves from the west coast to the east coast

46. Overall movement is west to east • Local wind patterns can be from any direction

47. Recognizing fronts on a map • sharp temperature changes over relatively short distances • changes in the moisture content of the air (dew point) • shifts in wind direction • low pressure troughs and pressure changes • clouds and precipitation patterns

48. Types of fronts • Named for the invader • Each type of front has a typical weather scenario

49. Cold Front • heavy cold air displaces lighter warm air, pushing it upward • Cumulus clouds form and usually grow into thunderstorms • Temperatures drop anywhere from 5 to 15. • Winds become gusty and erratic. • Rain, snow, sleet, and hail can occur with a cold front.

50. Warm Front • Warm fronts occur when warm air replaces cold air by sliding over it. • Altocumulus clouds form and may be associated with rain, snow, or sleet. • Temperatures may warm slightly. • Winds are usually gentle with this kind of front.