Wednesday, 11 April 2012

Fieldwork Opportunities: Hazardous Environments

Fieldwork Opportunities: Hazardous Environments

Measuring, collecting and recording weather data:
  • During the passage of a tropical storm, local weather stations will record an enormous increase in wind speed and rainfall.
  • Instrument area is used to measure local weather conditions in calmer, drier conditions-providing primary data.
  • Care and accuracy important when measuring weather-instrument itself has to be suitable as well as its use accurate.
  • Should have an easy to complete record sheet showing date, time and columns for each element of the weather you have instruments for. Eg maximum/minimum temperature and rainfall.
  • Records should be kept daily and for at least a week. Readings should be taken preferably at same time each day.

Rain Gauge:
  • It should be placed in open space so it can collect rain water straight from the sky.
  • Rain is collected in a measuring flask and the measurement can be read easily.
  • Once reading is noted, the water has to be tipped away daily.

Stevenson Screen:
  • Instruments used to measure temperature and humidity should be kept inside a Stevenson Screen.
  • It’s a wooden box used to shade from direct sunlight and radiation so that the instruments inside can measure air temperature.
  • It’s painted white to reflect sunlight and has vents to allow free flow of air. This makes the readings fair.
  • Maximum-minimum thermometer housed inside measures the highest and lowest temperature, often within a 24-hour period. –weather data should be standardised.
  • Readings have to be taken so that they can be compared with those taken at other places and at other times.
  • After noting temperature readings, the thermometer has to be reset by sliding the magnetic base over the mercury columns.

Cup Anemometer and wind valve:
  • Wind valve measures wind direction.
  • Cup anemometer is a weather instrument that measures wind speed/strength.
  • There are 3 to 4 cups mounted on a vertical pole. The cups catch the blowing wind and turn the pole.
  • Each time the anemometer makes a full rotation, the wind speed is measured by the number of revolutions per minute (RPM).
  • The number of revolutions is recorded over time and an average is determined.

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