Weather Instruments

Weather Instruments Meteorologist use different tools to measure weather. Here are some of the instruments they use: Thermometer Barometer Anemometer Hygrometer Rain gauge Wind Vane Weather balloon Satellite

Thermometer A thermometer measures heat and cold. Meteorologist use it to measure air temperature. Liquids expand (get bigger) when heated and contract (get smaller) when cooled. That means their volume (occupied space) changes with their temperature.

Thermometer The liquid inside older thermometers is mercury. It was used because of its resistance to heat and cold. Unlike water, mercury freezes at minus 39 degrees Celsius (-39°C) and boils at three hundred fifty seven degrees Celsius (357°C).

Thermometer Units of Measure The two (2) measurement units used with a thermometer are degrees Fahrenheit and degrees Celsius. The Celsius scale sets the freezing point of water at 0 degrees (0°C) and the boiling point at 100 degrees (100°C). The Fahrenheit scale sets the freezing point of water at 32 degrees (32°F) and the boiling point at 212 degrees (212°F).

Barometer A barometer measures air pressure or barometric pressure. The barometer dial is marked in two scales. The outer scale shows the units of inches of mercury. The inner scale shows air pressure in millibars.

Air Pressure Air pressure is a function of the quantity of air and the amount of space in which the air is contained. Air pressure is also the function of temperature.

Air Pressure and Weather Changing air pressure indicates changing weather. Rising air pressure usually means that cooler, drier air is coming, so there will be fair weather. Falling air pressure usually means that warmer, moister air is coming, so there will be wet weather.

Anemometer An anemometer measures the speed or strength of wind. The most common types of anemometer have a mechanism that rotates as it catches the wind.

Wind Speed and Weather Wind speed is related directly to wind strength. Wind strength is commonly reported on the Beaufort scale. The Beaufort scale rates the strength of wind on a scale of 0 – 12. A Beaufort number of 0 indicates total calm. A Beaufort number of 12 indicates hurricane strength winds (exceeding 74 mph).

Hygrometer A hygrometer measures relative humidity. Humidity is the amount of water vapor in the air. A reading of 100 percent relative humidity means that the air is totally saturated with water vapor and cannot hold any more, creating the possibility of rain.

People and Humidity The process of sweating is the human body's attempt to keep cool and maintain its current temperature. If the air is at 100-percent relative humidity, sweat will not evaporate into the air. As a result, we feel much hotter than the actual temperature when the relative humidity is high. If the relative humidity is low, we can feel much cooler than the actual temperature because our sweat evaporates easily, cooling us off.

Rain Gauge A rain gauge is an instrument used to gather and measure the amount of liquid precipitation over a set period of time. Most standard rain gauges have a wide funnel leading into a cylinder that is marked in inches or centimeters. They are calibrated (set up) so that one-tenth of an inch of rain measures one inch when it collects inside. In other words, each inch in the funnel counts as one-tenth of an inch of rain.

Wind Vane A wind vane indicates in what direction the wind is traveling.

Weather Balloon A Weather balloon is a mobile weather station sent up to measure atmospheric pressures, temperature, wind speeds and humidity.

Satellite Weather satellites are used for viewing large weather systems on Earth such as hurricanes and other cloud formations.