※Silver Star Weather Station – Weather Observation Instruments
Weather instruments are essential for every meteorologist. They cannot observe weather without these instruments, and we would not have known weather change in advance. Weather is very important in our life. For example, we have to hang our clothes every day. In the past, farmers had to bring in helpers in advance during harvest season. If the weather changes unannounced, they could suffer heavy loss of crops, or even in danger of losing their life or household.
This day we went to master Lu’s house and saw the famous Silver Star weather station. Master pointed at the roof above the ladder, indicating his instruments. Team Pika members looked at the ceiling ten meters above the ground. Although there were risks of falling down the ladder, we still insisted to climb up to see his weather instruments. We thought of giving up, but with the help of master we overcame our fears climbing up. In fact, it’s not as difficult as we thought. The view on the roof was really beautiful, and we could see most of Hemei and beyond. We were very amazed by master on his extraordinary ability to install all these instruments on this limited space.
The followings are his introduction of weather instruments at Silver Star weather station(please click the headings below)
The followings are his introduction of weather instruments at Silver Star weather station(please click the headings below)
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Siphon Rain Gauge
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Tipping Bucket Rain Gauge
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Wind Vane
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Anemometer
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Rain is the combined amount of precipitation on level surface without leakage, drainage, evaporation during a particular time period. It is the measurement of precipitation for specific area. Siphon rain gauge has been used:since the beginning of this station. Usage:to measure the amount of rainfall. Structure and principle:the funnel receive rains from a pipe and channels water into a float and a container. The float rises as the water level rises. Its movement is recorded by a pen moving on a recording drum actuated by a clock work. When the container is full of water, a glass or metal siphon releases the water. After all water is drained out, the float would drop to the bottom of the container, and the pen would return to zero on the paper. When rain stops, the pen would also stop its movement and recording into a straight line.
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Siphon Rain Gauge
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Tipping bucket rain gauge is a remote control rain gauge consisted of a sensor and signal recorder. Sensor consists of receiver, funnel, tipping bucket, counter, level;recorder consists of counter, pen, self-recording clock, control circuit board. Its operating principle:rain flows into a funnel through a receiver nozzle, then channels into a container. When a pre-set amount of precipitation falls (for example, 0.1 mm), the lever would tip. Every time it tips, the circuit would send an electrical signal. The pen on the recorder would move up and down recording the precipitation process.
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Tipping Bucket Rain Gauge
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Wind vane is an instrument for showing the direction of the wind. It is usually installed on a pole 10 meters above the ground in an open space. Under air pressure, its arrow points at the direction of the wind. Generally a wind vane is divided into head, leveling rod, and tail three parts. Wind speed and wind direction are measured respectively by cup anemometer and wind vane. Cup anemometer is usually consisted of three symmetrical cups fixed on the vertical axis, so diametral plane of every cup is vertical. Concave surface of cup can withstand stronger wind than its convex surface, so the cup would rotate with the wind. Observer can measure wind speed based on rotating speed of the cup. Wind direction is measured by wind vane. Wind vane is basically an asymmetrical object with its center of gravity fixed on vertical axis. When wind blows by, the one end which can withstand stronger wind would rotate with the wind, indicating wind direction.
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Wind Vane
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Anemometer is a device used for measuring wind speed. There are vane and cup anemometer. It is a cup anemometer at this weather station. It is installed on a pole 10 meters above the ground in an open space. Based on rotating speed of the cup in a particular time, we can calculate average wind speed.
Anemometer is an instrument for measuring air flow rate. There are various types of anemometers. Cup anemometer is the most common one at weather station. Concave surface of the cup is pointed at one direction. The entire sensor part is installed on a vertical axis of rotation. Under wind effect, the cup rotates in direct proportion with wind speed. Another rotating anemometer is propeller anemometer. It is consisted of a three or four vane propeller as sensor. It is installed on the front end of a wind vane, so it can always point at the direction of the wind. The propeller rotates around horizontal axis in direct proportion with wind speed. |
Anemometer
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Anemograph
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Wind Speed Alarm
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Psychrometer
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Aneroid Barometer
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Wind is a 3-Dimensional vector. There are only horizontal wind speed and wind direction in weather observation. Vertical vector is never considered. Electric propeller anemograph was used: from 1951 to 1971. Usage: to measure wind direction and wind speed. Structure and principle: a four-blade propeller as a sensor, a streamline frame connecting to an AC synchronous generator, the propeller on the top of the frame rotating with the wind, electric generation when the rotating shaft connecting to the rotor of AC generator, different wind speeds generate different voltages, when installing a variable resistor on the fulcrum, every bearing has its own corresponding resistance. The value of wind speed voltage and wind direction resistance can be converted into wind speed and wind direction through a convertor. The numbers will transmit on a recorder. Sensor is installed on a wind tower. Convertor and recorder are installed inside observation room.
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Anemograph
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Wind speed alarm consists of microprocessor and high dynamic sensor. It can observe instantaneous wind speed and two or ten minute average wind speed. It contains wind speed alarm setting and output control function. Wind speed alarm has two screen and high brightness LED segment display. It can be displayed in distance, under dim light, and at night.
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Wind Speed Alarm
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Psychrometer consists of two thermometers:one is dry-bulb thermometer (usually used for measuring temperature), one is wet-bulb thermometer, its mercury (or alcohol) bulb is kept moist with water on the wick. Therefore it is called wet-and-dry-bulb thermometer, or psychrometer.
When moisture content in the air has not reached saturation, evaporation of the water would absorb heat and lower wet-bulb temperature. At the same time, wet bulb absorbs heat from nearby air. When these two heat sources reach a balance, wet-bulb temperature stops dropping. Meteorologists have formulated humidity conversion table and dew point temperature graph based on related elements. Therefore, we only have to measure wet-bulb and dry-bulb temperatures, and by substituting them into corresponding charts we can figure out relative humidity and dew point. |
Psychrometer
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Aneroid barometer, also called non-liquid barometer, is a barometer uses an evacuated metal box as sensor. Small changes in external air pressure cause the box to expand or contract. This expansion and contraction drives tiny movements that can be displayed on the barometer. The advantage is more portable and easy to install. However, elastic coefficients of metal change with different temperatures. Temperature compensation has to be applied. Elastic hysteresis causes deformation of metal box. Within a particular air pressure, stress-strain curves do not coincide.
The above two factors cause aneroid barometer to have lower accuracy than mercury barometer. Aneroid barometer is based upon the principle of manometer. It is an automatic recording manometer, and a physical measurement instrument which measuring air pressure. It is mainly used for physics experiment class, measurement of atmospheric pressure by weather station, and measuring the pressure of closed vessels (such as oxygen cylinder, nitrogen bottle, acetylene bottle and dry-powder extinguisher) by welding or fire departments. |
Aneroid Barometer
Internal structure of aneroid barometer
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Texts:Team Pika, Central Weather Bureau-Weather Observation Instruments
Pictures:Silver Star Weather Station
Pictures:Silver Star Weather Station