Rain Data Collection At Airports: Who's Responsible?

Airports are equipped with automated weather stations that collect rain data. These weather stations are known as AWOS (Automatic Weather Observation System) and are usually operated by agencies that oversee aviation safety, like the Federal Aviation Administration (FAA). AWOS provides real-time data to airports, pilots, national weather services, and the media. One of the instruments used to collect rain data is the tipping bucket rain gauge, which is widely used due to its accuracy and automation capabilities.

Automated airport weather stations

Larger regional and big international airports have dedicated weather stations known as AWOS (Automatic Weather Observation System) weather stations. These systems are usually operated by agencies that oversee aviation safety, like the Federal Aviation Administration (FAA). AWOS provides real-time data to airports and pilots, national weather services, and the media.

Another instrument used in automated airport weather stations is the lightning detection system. Many stations in the United States use the National Lightning Detection Network (NLDN) in conjunction with the automatic lightning detection and reporting system (ALDARS). The NLDN uses 106 sensors to triangulate lightning strikes, and this data is then fed into ALDARS, which sends messages to each automated airport station informing them of the proximity of lightning strikes. This information is crucial for aviation safety, as lightning strikes within a certain range of the station result in reports of thunderstorms, which can impact flight operations.

Additionally, automated airport weather stations use sensors to detect and report icing conditions. These sensors measure the resonant frequency of a vibrating rod, which decreases as ice, hoarfrost, freezing fog, or wet snow accumulates. By combining this sensor output with data from LEDWI (likely an acronym for a specific system or device), the system can accurately report freezing rain. This information is vital for airports to ensure safe flight operations and make informed decisions regarding runway conditions and de-icing procedures.

In conclusion, automated airport weather stations play a critical role in collecting and disseminating real-time weather data. By utilising various instruments and sensors, these stations provide essential information on precipitation, lightning, and icing conditions to support aviation safety and efficient airport operations.

Tipping bucket rain gauges

The device consists of a receiver (a funnel) that collects rainwater into a bucket, which is one-half of a two-bucket receptacle. The bucket is pivoted on a cylindrical axis, and once the upper bucket fills up to a specified amount of water (tipping volume, Vt), it tips, emptying the water and moving the other bucket under the funnel. The tipping motion activates a switch (either a reed or mercury switch), which sends an electrical pulse for each specified amount of precipitation collected. The tipping volume can be set by two calibration stop screws, one for each bucket.

TBRs have some disadvantages, including measurement biases, particularly in wind and mechanical underestimations. Calibration methodologies are not frequently implemented, which can cause uncertainty in modelling, management, and forecasting in hydrological research.

There are several different models of TBRs, including the HS-TB3 (Hydrological Services Pty Ltd), ISCO-674 (Isco, Inc.), and TR-525 (Texas Electronics, Inc.). Researchers have also developed an all-electronic rain gauge that uses microwave sensors, although this consumes significant power.

Freezing rain detection

Automated airport weather stations are used to collect rain data at airports. These stations are automated sensor suites designed to serve aviation and meteorological operations, weather forecasting, and climatology. They are widely used due to their accuracy and automation capabilities.

Automated airport weather stations can detect freezing rain using a combination of sensors. One such sensor is a vibrating rod that measures the resonant frequency of the precipitation. The resonant frequency decreases as the mass of ice increases. Another sensor used in conjunction with the vibrating rod is the Light Emitting Diode Weather Identifier (LEDWI). The LEDWI uses an infrared beam to measure the scintillation pattern of the precipitation, including particle size and fall velocity, to determine if it is rain or snow. If the LEDWI detects precipitation but cannot identify it as rain or snow, it is reported as unknown.

In addition to these sensors, the National Lightning Detection Network (NLDN) is used to detect lightning and provide data to automated airport stations. This data helps to identify potential thunderstorms in the vicinity of the airport.

To ensure the safety of aircraft and efficient airport operations during freezing rain events, weather forecasts are critical. Airports use a mix of public and aviation weather forecasts to prepare for these events, which often require increased staffing and coordination. Aircraft are typically routed away from forecasted or reported freezing rain, and ground operations may be suspended during periods of freezing rain due to the challenges posed by ice accretion.

Weather Surveillance Radar

Modern weather radars, such as the NEXRAD or WSR-88D (Weather Surveillance Radar 1988 Doppler), are mostly pulse-Doppler radars capable of detecting the motion of rain droplets and the intensity of precipitation. This data can be analysed to determine the structure of storms and their potential to cause severe weather. Doppler weather radar is not limited to determining the location and velocity of precipitation but also provides detailed information on each storm cloud being tracked. For example, once a thunderstorm cell is identified, its speed, distance covered, direction, and Estimated Time of Arrival (ETA) are all tracked and recorded.

The Next Generation Weather Radar system is a network of 160 high-resolution Doppler radars around the world, jointly operated by the National Weather Service, Federal Aviation Administration, and the Department of Defense. The network operates 24/7, providing real-time precipitation and wind data to meteorologists for weather forecasts and severe weather warnings. The data is also made available to the public. In 2012, the network was upgraded to dual-polarization, improving the ability to identify precipitation type, estimate rainfall for flash flood warnings, and locate conditions for potential tornadoes.

Automated airport weather stations use various instruments to collect and report weather data, including rain gauges, freezing rain sensors, and lightning detection systems. Tipping bucket rain gauges, such as the heated tipping bucket rain gauge, are widely used due to their accuracy and automation capabilities. This device collects precipitation in a pivoting bucket until it reaches a certain weight, causing the bucket to tip and activate a switch that sends an electrical pulse for each 0.01-inch (0.25 mm) of precipitation collected. Other instruments used by automated airport weather stations include the National Lightning Detection Network (NLDN) to detect lightning and automated surface observing systems (ASOS) to measure parameters such as barometric pressure, altimeter setting, and runway surface conditions.

Upper air observation systems

Upper-air observations are crucial for accurate weather forecasts, research, and historical climatology. The National Weather Service (NWS) in the United States operates an Upper-air Observations Program, managed by the Office of Observations (OBS) in Silver Spring, Maryland. This program oversees the operation of 92 Radiosonde stations in North America and the Pacific Islands, with an additional 10 stations in the Caribbean supported by the Cooperative Hurricane Upper Air Stations (CHUAS) program.

Radiosondes are instrument packages that measure upper-air data such as atmospheric pressure, temperature, humidity, wind speed, and direction. They are carried by weather balloons launched twice daily from nearly 100 locations across the United States. The data collected by these radiosondes is vital for weather forecasts and research, and the OBS staff also work on developing and implementing new radiosonde ground systems.

In addition to radiosondes, other methods are used to collect upper-air data. For instance, the National Oceanic and Atmospheric Administration (NOAA) utilizes moored buoys to measure and transmit data such as barometric pressure, wind speed and direction, air and sea temperature, and wave energy. These buoys are deployed in coastal and offshore waters, from the western Atlantic to the Pacific Ocean, and are valuable for operational forecasting, emergency response, and scientific research.

Furthermore, the NWS also collects data from aircraft. The Meteorological Data Collection and Reporting System (MDCRS) is a system where data is gathered from commercial aircraft. This includes measurements of static and total air pressure, air temperature, and wind speed. The data is then used to improve numerical weather prediction models, leading to more accurate forecasts.

These upper-air observation systems, including radiosondes, moored buoys, and aircraft-based data collection, play a critical role in gathering information about the Earth's atmosphere, enabling meteorologists to provide timely and accurate weather forecasts, warnings, and research data.

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