Weather Station

A Weather Station (also known as an AWOS – Automated Weather Observing System, or METAR station) is an integrated system of meteorological sensors and data processing equipment that measures, records, and disseminates weather conditions at an airfield. These systems provide critical environmental data for ATC, pilots, airport operations, and maintenance teams. A typical airfield weather station includes sensors for wind speed and direction, temperature, humidity, barometric pressure, precipitation, visibility (RVR – Runway Visual Range), cloud height (ceilometer), and present weather (rain, snow, fog). The data is transmitted to ATC, flight planning systems, airfield displays, and often broadcast via ATIS (Automatic Terminal Information Service). Weather stations are essential for safe aircraft operations, enabling low‑visibility procedures (CAT II/III), runway selection, and winter maintenance planning. They are typically installed at multiple locations across the airfield, with primary units near the runway threshold and secondary units at other key points.

The weather station's purpose is to turn a set of individually noisy sensor readings, wind, visibility, ceiling, pressure, into a single, consistent operational picture that ATC, pilots, and airport operations can all act on with confidence. Because low-visibility procedures such as CAT II/III activation, runway selection, and winter maintenance triggers depend on threshold values being crossed reliably rather than approximately, the station's role is as much about measurement integrity and consistent siting as it is about the sensors themselves; a reading taken at the wrong point on the airfield or with a miscalibrated instrument can trigger the wrong operational response. Distributing primary and secondary units across key locations, rather than relying on one central reading, is what lets the reported conditions actually reflect what a specific runway threshold or approach path is experiencing rather than an airfield-wide average.

Weather stations are deployed at various critical locations across the airfield:

• Runway Thresholds: Primary weather stations located near runway ends, providing RVR, wind, and visibility data for approach and landing.
• ATC Towers: Integrated weather displays for controllers, often with dedicated wind sensors on the tower itself.
• Mid‑Runway: Additional wind and visibility sensors for cross‑wind and mid‑field conditions.
• Apron Areas: Weather data for ground handling, gate operations, and de‑icing procedures.
• Remote Locations: Stand‑alone weather stations for specific approach paths or outlying areas.
• Maintenance Facilities: Weather data for winter maintenance planning and runway friction management.
• Flight Planning & Briefing: Providing weather data to pilots for pre‑flight planning and dispatch.
• ATIS Broadcast Systems: Automated weather reporting for pilot information.

Individual sensor heads (wind, RVR transmissometer, ceilometer, temperature/humidity) are distributed at the specific locations their reading applies to — threshold, mid-runway, or apron — each mounted on its own mast or post at the height and setback specified for that sensor type, kept clear of turbulence-inducing obstacles and of the runway strip's frangibility requirements. Sensor cabling runs back to a local field enclosure and from there, generally over fibre or a dedicated data link, to the central weather processing system so RVR and wind readings reach ATC with minimal latency; mast foundations account for wind loading given the sensors' typically exposed siting, and each sensor's exact position is surveyed and documented since its reading is only valid for the specific location it represents.

The weather station operates as an integrated data acquisition and dissemination system. Key functional aspects include:

• Sensor Suite: The station includes multiple sensors, each measuring a specific parameter:
  • Wind Sensors: Ultrasonic or cup‑and‑vane anemometers for speed and direction, often with gust measurement.
  • Temperature & Humidity: Platinum resistance thermometers (RTD) and capacitive humidity sensors in a radiation shield.
  • Barometric Pressure: Silicon‑based or capacitive pressure transducers, providing QNH and QFE readings.
  • Visibility (RVR): Forward scatter meters or transmissometers measuring atmospheric transparency.
  • Ceilometer: Laser‑based instrument measuring cloud ceiling height (up to 15,000 ft).
  • Precipitation: Tipping‑bucket rain gauge or optical disdrometer for rain/snow measurement.
  • Present Weather: Optical sensors that detect fog, haze, rain, snow, and other obscurations.
• Data Acquisition: A central data logger samples sensors at high frequency (typically 1‑10 Hz), processes raw data, and computes averaged and instant values.
• Quality Control: The system applies algorithms to detect sensor failures, outliers, and consistency checks (e.g., comparing redundant sensors) to ensure data reliability.
• Data Dissemination: Real‑time data is transmitted via Ethernet, serial (RS‑232/485), or wireless to ATC displays, A‑SMGCS, ATIS, and weather networks (e.g., World Meteorological Organization).
• Data Logging: Historical weather data is stored locally and often transmitted to central servers for analysis, reporting, and regulatory compliance.
• Self‑Diagnostics: The station monitors its own health (power, communication, sensor status) and provides alarms for maintenance.

Weather stations are designed for 24/7/365 operation in harsh environments, with heated sensors for icing conditions, redundant power supplies, and lightning protection.

The weather station's data has two separate downstream paths rather than a single control loop. Raw sensor readings are aggregated and quality-checked by the station's own data logger, then distributed over Ethernet or serial to ATC displays, ATIS, and A-SMGCS for direct human and system use — these paths carry information only, with no lighting action attached. Where RVR is used to drive airfield lighting intensity, a separate path feeds the RVR reading (via the ALCMS server or a dedicated interface) into the brightness-step logic that also considers ATC instruction and pilot-controlled lighting input, and it is that combined logic — not the weather station directly — that commands the CCR to change intensity. A sensor fault or data-quality flag is reported at the station level and, if it affects a value used for lighting control, is escalated to the ALCMS as a degraded-input condition rather than silently continuing to drive brightness decisions on unreliable data.

Each sensor — anemometer, thermometer, hygrometer, barometer, precipitation gauge, ceilometer, or visibility sensor — is housed in its own sealed, weatherproof enclosure rated IP65/IP67, mounted at the height and orientation its measurement principle requires on a common mast, pole, or tripod, typically 10–30 m tall for wind sensors and lower for temperature and precipitation instruments. Sensors exposed to icing conditions incorporate internal heating elements to keep moving parts (anemometer cups or vanes) and measurement surfaces free of ice, drawing the higher end of the unit's power consumption range during cold-weather operation. All sensor cabling runs down the mast in a common duct or cable tray to a base-mounted data logger enclosure, itself sealed to IP65/IP67 and housing the signal-conditioning electronics, communication interfaces, and battery/solar backup where mains power is not available at the site. The mast or tripod structure is engineered for the local wind-loading design case, and where sited near the runway, mast height and guy-wire anchoring are coordinated with obstacle-limitation surface requirements.