Weather

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 Background material

 Curriculum goals

Aim

• Map weather and wind conditions in the explored area.
• Understand the conditions impact on biological diversity in the area.

Co-operation partners

The local weather station.

Equipment

Pennant or weathercock, anemometer, thermometer, barometer, compass, precipitation gauge

Accomplishment

The more often you measure these physical elements, the better foundation you have for assessing the impact on biological diversity

How weather-exposed is the area ?

Try to assess whether the the area is sheltered, moderately exposed or exposed of weather and wind. This means alot to the plants and animal life in the area. Usually the diversity is higher in sheltered areas.

Wind force and direction

For information on wind force and direction on the exploration day, contact your local weather station, or measure it yourself when in the field using a anemometer.
Wind force may also be measured in the field using a simple ombrometer (a light ball moving up a tube with a measure scale). The wind direction can be measured with a pennant or weathercock on selected measuring points. Use the compass for directional support.

Air temperature and atmospheric pressure

Measure the air temperature with a thermometer in a shadowed area.
The atmospheric pressure can be measured with a barometer. The barometric pressure is the normal atmospheric pressure at sea-level. This pressure is 760 mm Hg (the pressure exerted by a column of mercury, 760 mm high) or 1013 hPa (1013 hPa = 1013 millibars = 101,3 Newtons per square meter). Values lower than the barometric pressure is concidered as low atmospheric pressure, and values above as high atmospheric pressure. Pressure decreases with increased altitude. Clear days implies high atmospheric pressure and clouded weather implies low atmospheric pressure. The unofficial world record in high pressure was measured in Siberia in 1968 at 812,1 mm Hg (1083,8 hPa) on a cold winter day. The lowest documented barometric pressure in the North Atlantic was measured south of Greenland in 1986, showing 689,8 mm Hg (920,2 hPa). The lowest pressure in the world you will probably find in the tropical forests, in the rainy season.

Precipitation

Measure the precipitation with a precipitation gauge. You can buy a precipitation gauge, or you can fasten a measuring cylinder to the end of a pole an stick the pole in the ground. Set out the precipitation gauge for 24 hours and measure the volume (be accurate - even if it hasn't rained in any extended time, evaporation might influence the other way around). if the precipitation is snow, bring it in and melt it before reading the result.

Cloud cover and visibility

There are different ways of estimating the cloud cover. Most ways include dividing the sky into squares, but the number of square varies. Some ways use the percentage cover in each square and calculates an average value. In this project we follow these instructions: The cloud cover is estimated by dividing the vault of heaven into 8 parts and counting how many parts have clouds in them. If one part is only partially clouded it is still counted as clouded. Your results on this will be more accurate if you look through a frame of 8 squares.
In order to follow the rules of weather forecasting for assessing the visibility you actually need to stand on place which have the potensial of over 10 km of free view. If it reaches it's potensial it is named as a "Clear view". "Somewhat hazy" covers the moderate visibility range of 4 to 10 km, and "Very hazy" covers all below 4 km.

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Weather

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