Weather and Climate: notes

Weather

• Weather vs climate: weather is the day to day state of the air. Climate is the average weather over about 30 years.
• Instruments: thermometer (temperature), rain gauge (rainfall), barometer (pressure), anemometer (wind speed), wind vane (direction), hygrometer (humidity).
• Stevenson screen: a white, louvred box on legs that shades instruments and lets air through.

Rainfall Types

• Relief rain: moist air is forced up a mountain, cools and drops rain on the windward side.
• Convectional rain: hot ground heats the air, it rises, cools and gives afternoon storms. Common in Zimbabwe's rainy season.
• Frontal rain: warm air rises over cold air at a front.

Climate of Zimbabwe

• Seasons: hot wet season (November to March), cool dry season (May to August), hot dry season (September to October).
• What shapes climate: latitude, altitude (about 1 degree C cooler for every 150 m up), distance from the sea, ocean currents and prevailing winds.
• Global warming: extra greenhouse gases such as carbon dioxide trap heat and raise temperatures.