Surface weather observation

Surface weather observations are the fundamental data used for safety as well as climatological reasons to forecast weather and issue warnings worldwide.[1] They can be taken manually, by a weather observer, by computer through the use of automated weather stations, or in a hybrid scheme using weather observers to augment the otherwise automated weather station. The ICAO defines the International Standard Atmosphere, which is the model of the standard variation of pressure, temperature, density, and viscosity with altitude in the Earth's atmosphere, and is used to reduce a station pressure to sea level pressure. Airport observations can be transmitted worldwide through the use of the METAR observing code. Personal weather stations taking automated observations can transmit their data to the United States mesonet through the use of the Citizen Weather Observer Program (CWOP), or internationally through the Weather Underground Internet site.[2] A thirty-year average of a location's weather observations is traditionally used to determine the station's climate.[3]

Contents

Airports

Surface weather observations have traditionally been taken at airports due to safety concerns during takeoffs and landings. The ICAO defines the International Standard Atmosphere (also known as ICAO Standard Atmosphere), which is the model of the standard variation of pressure, temperature, density, and viscosity with altitude in the Earth's atmosphere. This is useful in calibrating instruments and designing aircraft,[4] and is used to reduce a station's pressure to sea level pressure where it can then be used on weather maps.[5]

In the United States, the FAA mandates the taking of weather observations for safety reasons. To help facilitate the purchase of an automated airport weather station, such as ASOS, the FAA allows federal dollars to be used for the installation of certified weather stations at airports.[6] The airport observations are then transmitted worldwide using the METAR observing code. METAR reports typically come from airports or permanent weather observation stations. Reports are generated once an hour; however, if conditions change significantly, they may be updated in special reports called SPECI's.[7]

Data Reported

Surface weather observations can include the following elements:

Example of a METAR surface weather observation

METAR LBBG 041600Z 12003MPS 310V290 1400 R04/P1500N R22/P1500U +SN BKN022 OVC050 M04/M07 Q1020 NOSIG 9949//91=[21]

Personal weather stations, maintained by citizens rather than government officials, do not use METAR code. Software allows information to be transmitted to various sites, such as Weather Underground globally,[2] or CWOP within the United States,[22] which can then be used by the appropriate meteorological organizations either to diagnose real-time conditions, or be used within weather forecast models.

Use on weather maps

Data collected by land locations coding in METAR are conveyed worldwide via phone lines or wireless technology. Within many nations' meteorological organizations, this data is then plotted onto a weather map using the station model. A station model is a symbolic illustration showing the weather occurring at a given reporting station.[23] Meteorologists created the station model to plot a number of weather elements in a small space on weather maps.[24] Maps filled with dense station-model plots can be difficult to read, but they allow meteorologists, pilots, and mariners to see important weather patterns.

Weather maps are used to display information quickly showing the analysis of various meteorological quantities at various levels of the atmosphere, in this case the surface layer.[25] Maps containing station models aid in the drawing of isotherms, which more readily identifies temperature gradients,[26] and can help in the location of weather fronts. Two-dimensional streamlines based on wind speeds show areas of convergence and divergence in the wind field, which are helpful in determining the location of features within the wind pattern. A popular type of surface weather map is the surface weather analysis, which plots isobars to depict areas of high pressure and low pressure.

Ship and buoy reports

For over a century, reports from the world's oceans have been received real-time for safety reasons and to help with general weather forecasting. The reports are coded using the synoptic code, and relayed via radio or satellite to weather organizations worldwide.[27] Buoy reports are automated, and maintained by the country that moored the buoy in that location. Larger moored buoys are used near shore, while smaller drifting buoys are used farther out at sea.[28]

Due to the importance of reports from the surface of the ocean, the voluntary observing ship program, known as VOS, was set up to train crews how to take weather observations while at sea and also to calibrate weather sensors used aboard ships when they arrive in port, such as barometers and thermometers.[29] The beaufort scale is still generally used to determine wind speed from manual observers out at sea. Ships with anemometers have issues with determining wind speeds at higher wind speeds due to blockage of the instruments by increasing high seas.

Use in establishing climate of a location

Climate, (from Ancient Greek klima) is commonly defined as the weather averaged over a long period of time.[30] The standard averaging period is 30 years for an individual location,[3] but other periods may be used. Climate includes statistics other than the average, such as the magnitudes of day-to-day or year-to-year variations. The Intergovernmental Panel on Climate Change (IPCC) glossary definition is:

Climate in a narrow sense is usually defined as the “average weather”, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period is 30 years, as defined by the World Meteorological Organization (WMO). These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system.[31]

The main difference between climate and everyday weather is best summarized by the popular phrase "Climate is what you expect, weather is what you get."[32] Over historic time spans there are a number of static variables that determine climate, including: latitude, altitude, proportion of land to water, and proximity to oceans and mountains. Degree of vegetation coverage affects solar heat absorption, water retention, and rainfall on a regional level.

See also

References

  1. ^ Office of the Federal Coordinator of Meteorology. Surface Weather Observation Program. Retrieved on 2008-01-12.
  2. ^ a b Weather Underground. Personal Weather Station. Retrieved on 2008-03-09.
  3. ^ a b MetOffice. Climate Averages. Retrieved on 2008-03-09.
  4. ^ ICAO, Manual of the ICAO Standard Atmosphere (extended to 80 kilometres (262 500 feet)), Doc 7488-CD, Third Edition, 1993, ISBN 92-9194-004-6
  5. ^ Patricia M. Pauley. An Example of Uncertainty in Sea Level Pressure Reduction. Retrieved on 2008-03-29.
  6. ^ Allweatherinc. Why buy an AWOS? Retrieved on 2008-01-12.
  7. ^ National Climatic Data Center. METAR Home Page. Retrieved on 2008-01-12.
  8. ^ Texas A&M University. Coding the Type of Report, Station Identifier, Date/Time, and Report Modifier groups. Retrieved on 2008-04-06.
  9. ^ a b c National Weather Service. Frequently Asked Questions about METAR/SPECI and TAF. Retrieved on 2008-04-06.
  10. ^ Glossary of Meteorology. Temperature. Retrieved on 2008-04-06.
  11. ^ Glossary of Meteorology. Air Temperature. Retrieved on 2008-04-06.
  12. ^ Glossary of Meteorology. Dewpoint. Retrieved on 2008-04-06.
  13. ^ Glossary of Meteorology. Dewpoint Formula. Retrieved on 2008-04-06.
  14. ^ a b Office of the Federal Coordinator for Meteorology. Federal Meteorological Handbook No. 1 - Surface Weather Observations and Reports September 2005 Appendix A: Glossary. Retrieved on 2008-04-06.
  15. ^ Hurricane Research Division. Frequently Asked Questions Subject D4) What does "maximum sustained wind" mean? How does it relate to gusts in tropical cyclones? Retrieved on 2008-04-06.
  16. ^ Patricia M. Pauley. An Example of Uncertainty in Sea Level Pressure Reduction. Retrieved on 2008-04-14.
  17. ^ USA Today. Understanding Air Pressure. Retrieved on 2008-04-14.
  18. ^ Texas A&M University. Present Weather Group w'w'(ww). Retrieved on 2008-04-14.
  19. ^ Ben C. Bernstein, Thomas P. Ratvasky, Dean R. Miller, and Frank McDonough. Freezing Rain as in In-Flight Icing Hazard. Retrieved on 2008-04-14.
  20. ^ NOAA Meteorological Assimilation Data Ingest System. How to Take Snow Measurements. Retrieved on 2008-04-14.
  21. ^ National Climatic Data Center. Key to METAR Surface Weather Observations. Retrieved on 2008-03-09.
  22. ^ Russ Chadwick. Citizen Weather Observer Program. Retrieved on 2008-03-09.
  23. ^ Steve Ackerman and Tom Whittaker. Station Model. Retrieved on 2008-03-27.
  24. ^ Illinois Central College. LAB J: Weather Maps and Humidity. Retrieved on 2008-03-27.
  25. ^ Encarta. Chart. Retrieved on 2007-11-25.
  26. ^ DataStreme. AIR TEMPERATURE PATTERNS. Retrieved on 2007-11-25.
  27. ^ National Weather Service. National Weather Service Observing Handbook 1: Marine Surface Weather Observations. Retrieved on 2008-01-13.
  28. ^ National Data Buoy Center. Moored Buoy Program. Retrieved on 2008-01-13.
  29. ^ National Data Buoy Center. The WMO Voluntary Observing Ships (VOS) Scheme. Retrieved on 2008-01-13.
  30. ^ Glossary of Meteorology. Climate. Retrieved on 2008-03-09.
  31. ^ Intergovernmental Panel on Climate Change. Appendix I: Glossary. Retrieved on 2007-06-01.
  32. ^ National Weather Service Office Tucson, Arizona. Main page. Retrieved on 2007-06-01.