10-Observations.ppt
- 1. Observations ENVI 1400 : Lecture 10
- 2. ENVI 1400 : Meteorology and Forecasting 2
- 3. ENVI 1400 : Meteorology and Forecasting 3 Synoptic Observations Observations synchronised worldwide at: 0000, 0600, 1200, 1800 UTC. – Some stations report more frequently: every 3 hours or hourly, some at only some of the above times. Two main sets of measurements: – Surface Observations – Upper air observations (radiosondes)
- 4. ENVI 1400 : Meteorology and Forecasting 4 Surface Observations Basic measurements: • Temperature, dew-point temperature, pressure, rainfall, wind speed & direction. • Manual observations of cloud cover & current weather: precipitation type, visibility,… Also: • Automated measurements of solar & IR radiation, visibility
- 5. ENVI 1400 : Meteorology and Forecasting 5
- 6. ENVI 1400 : Meteorology and Forecasting 6 Sources of Data • Surface-based measurements – Surface observations – Radiosondes • Remote Sensing – Satellites – Radar profilers, lidar, sodar • Numerical Model Analyses – Closely linked with forecasts
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- 8. ENVI 1400 : Meteorology and Forecasting 8
- 9. ENVI 1400 : Meteorology and Forecasting 9
- 10. ENVI 1400 : Meteorology and Forecasting 10
- 11. ENVI 1400 : Meteorology and Forecasting 11 Pyranometer – solar radiation Pyrgeometer – infra red radiation
- 12. ENVI 1400 : Meteorology and Forecasting 12 Beaufort Scale Beaufort Force Wind Speed (kts) Description Sea Condition 0 0 Calm Sea is like a mirror 1 1 – 3 Light air Ripples but without foam crests 2 4 – 6 Light breeze Small wavelets. Crests do not break 3 7 – 10 Gentle breeze Large wavelets, perhaps scattered white-caps 4 11 – 16 Moderate breeze Small waves. Frequent white-caps 5 17 – 21 Fresh breeze Moderate waves. Many white-caps 6 22 – 27 Strong breeze Large waves begin to form. White foam crests, perhaps some spray 7 28 – 33 Near gale Sea heaps up. White foams blown in streaks along wind 8 34 – 40 Gale Moderately high waves. Crests begin to break into spindrift 9 41 – 47 Strong gale High waves. Dense foam along the direction of the wind. Crests of waves begin to roll over. Spray may affect visibility 10 48 – 55 Storm Very high waves with long overhanging crests. The surface of the sea takes a white appearance. The tumbling of the sea becomes heavy and shock like. Visibility affected 11 56 – 63 Violent storm Exceptionally high waves. The sea is completely covered with long white patches of foam lying in the direction of the wind. Visibility affected 12 64+ Hurricane The air is filled with foam and spray. Sea completely white with driving spray. Visibility very seriously affected. Defined by Admiral Sir Francis Beaufort (1774-1857)
- 13. ENVI 1400 : Meteorology and Forecasting 13 Beaufort Force Wind Speed (kts) Description Conditions on Land 0 0 Calm Calm; smoke rises vertically 1 1 – 3 Light air Direction of wind shown by smoke drift, but not by wind vanes. 2 4 – 6 Light breeze Wind felt on face; leaves rustle; ordinary wind vanes moved by wind. 3 7 – 10 Gentle breeze Leaves and small twigs in constant motion; wind extends light flags. 4 11 – 16 Moderate breeze Raises dust and loose paper; small branches are moved. 5 17 – 21 Fresh breeze Small trees in leaf begin to sway; crested wavelets form on inland waters. 6 22 – 27 Strong breeze Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty. 7 28 – 33 Near gale Whole trees in motion; inconvenience felt when walking against the wind. 8 34 – 40 Gale Breaks twigs off trees; generally impedes progress. 9 41 – 47 Strong gale Slight structural damage occurs (chimney-pots and slates removed). 10 48 – 55 Storm Seldom experienced inland; trees uprooted; considerable structural damage occurs. 11 56 – 63 Violent storm Very rarely experienced; accompanied by wide-spread damage. 12 64+ Hurricane -
- 14. ENVI 1400 : Meteorology and Forecasting 14 Surface observations
- 15. ENVI 1400 : Meteorology and Forecasting 15
- 16. ENVI 1400 : Meteorology and Forecasting 16 Surface Observation Charts Charts of surface observations use a set of standard symbols to represent the meteorological conditions: – Wind speed and direction – Temperature – Humidity (dew point) – Cloud cover – Precipitation type & (approximate) amount – Pressure Symbols are defined by the World Meteorological Organisation (WMO), but feature some national additions or modifications. For UK surface maps see: www.medvale.demon.co.uk/weather/charts.htm http://meteocentre.com/analyse/map.php?hour= 0&lang=en&map=UK
- 17. ENVI 1400 : Meteorology and Forecasting 17 http://meteocentre.com/analyse/map.php?hour=0&lang=en&map=UK
- 18. ENVI 1400 : Meteorology and Forecasting 18 http://www.medvale.demon.co.uk/weather/charts.htm
- 19. ENVI 1400 : Meteorology and Forecasting 19 http://www.meteo.uni-koeln.de/meteo.php?show=En_We_Wk
- 20. ENVI 1400 : Meteorology and Forecasting 20 013 14 19 Temperature Dew point Current Weather conditions Pressure Wind barb Cloud cover 20 Visibility 20 = 2000m
- 21. ENVI 1400 : Meteorology and Forecasting 21 Clear skies 2/8 (25%) cloud cover 4/8 (50%) cloud cover 100% cloud cover 1/8 or less 3/8 cloud cover 7/8 or more cloud cover 6/8 (75%) cloud cover
- 22. ENVI 1400 : Meteorology and Forecasting 22 M Visibility obscured Missing data
- 23. ENVI 1400 : Meteorology and Forecasting 23 Long bar = 10 Short bar = 5 Units are KNOTS or m s-1 (usually knots) Flag = 50 5 kts 15 kts 25 kts 60 kts
- 24. ENVI 1400 : Meteorology and Forecasting 24 N Wind Wind direction N.B. Wind barb points in the direction the wind is blowing, but direction is quoted as angle wind is coming from (eg 135°, or southeasterly).
- 25. ENVI 1400 : Meteorology and Forecasting 25 Interpreting Pressure Reports If reported value > 500: Initial 9 is missing. Place it on left and divide by 10. e.g. 827 becomes 982.7 mb If reported value < 500 Initial 10 is missing. Place it on left and divide by 10. e.g. 027 becomes 1002.7 mb 013
- 26. ENVI 1400 : Meteorology and Forecasting 26 RAIN SNOW DRIZZLE light moderate heavy light rain shower moderate rain shower light moderate heavy light moderate FREEZING RAIN light moderate heavy light snow shower moderate snow shower
- 27. ENVI 1400 : Meteorology and Forecasting 27 thunderstorm Heavy thunderstorm Haze Fog Ice crystals Hail Tropical Storm Hurricane
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- 29. ENVI 1400 : Meteorology and Forecasting 29
- 30. ENVI 1400 : Meteorology and Forecasting 30
- 31. ENVI 1400 : Meteorology and Forecasting 31
- 32. ENVI 1400 : Meteorology and Forecasting 32 Radiosondes • Balloon-borne, ascent from surface to ~25km • Measure Temperature, humidity, pressure • Windspeed & direction are derived from change in GPS measured position • In past, position determined from radar reflection, or manual tracking with theodolite
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- 34. ENVI 1400 : Meteorology and Forecasting 34 Upper air observations
- 35. ENVI 1400 : Meteorology and Forecasting 35 Other Measurements An increasing variety of automated measurements are available: – Instruments fitted to commercial airliners – Weather radar – Radar wind profilers – Sodar wind profilers – RASS temperature profilers • Satellite remote sensing: – Surface temperatures – Cloud height – Water vapour concentration – Aerosol loading – Temperature profiles – Chemical concentrations (ozone, CO,…) – Surface winds over oceans
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- 37. ENVI 1400 : Meteorology and Forecasting 37
- 38. ENVI 1400 : Meteorology and Forecasting 38 Radar wind profiler: Obtains wind profiles from doppler shift of radar signal from array of antenna. Beam steered by phasing transmission.
- 39. ENVI 1400 : Meteorology and Forecasting 39 Wind profiler time-series