Overview

OVERVIEW

The History of AWOS

In the 1960's, MSC launched MARS (Meteorological Automatic Reporting Stations). These first autostations were modest - 13 stations sending hourly reports via teletype circuits to a central data base. In the early 1970's, MARS II was designed and built, 39 were installed.

Another series of autostations dubbed MAPS (Modular Acquisition Processing System), which drew upon solar power and satellite technology, was developed to serve the needs of isolated areas, such as coastal areas and the Arctic, where communications were difficult.

Since the mid-1980s, Environment Canada has been proceeding with changes in the way it provides weather information to Canadians, with the aim of creating a more modern and streamlined weather service. Technological advances led to the design of a new autostation and MSC emerged with plans for READAC (Remote Environmental Automated Data Acquisition Concept), later renamed AWOS (Automated Weather Observation System). Designed as a rugged field unit, AWOS is effective, durable and compact - about 1/3 the size of its predecessors - and built for ease of maintenance. Each AWOS sensor has its own microprocessors and the system can accommodate new technology as it becomes available.

How does AWOS Work?

AWOS does not predict the weather but sends current information to users, including weather offices, where forecasts are produced using this information along with computer modelling outputs, satellite photos and radar images, to name a few. AWOS is made up of a suite of sensors which measure, collect and disseminate weather data to help meteorologists, pilots and flight dispatchers prepare and monitor weather forecasts. The sensors measure such elements as wind velocity, ambient air and dew point temperatures, visibility, cloud height and sky condition, precipitation occurrence and type, as well as identifying icing or freezing conditions.

Each AWOS digitizes the measured weather parameters and transmits the data to assigned peripheral interfaces housed in a mainframe. With the exception of the pressure sensor, which is part of its peripheral interface, all sensors are normally situated within a sensor field, or compound, in the vicinity of the building housing the mainframe and the main signal distribution panel.

Every hour on the hour AWOS data is processed and made available to off-site users. When significant weather changes occur, AWOS automatically sends out special reports. This applies to changes in visibility, precipitation, sky and wind conditions.

As of 2002, there were approximately 110 AWOS sites across Canada, with 58 of them being used for aviation purposes.

A standard AWOS installation includes the following sensors.


Sensor	Weather Parameter
Laser ceilometer	Cloud height and density.
Visibility sensor	Visibility in miles.
Precipitation occurrence sensor	Type and intensity of precipitation
Pressure sensor	Barometric pressure
Temperature sensor	Ambient temperature
Dewcel	Dew point temperature
Wind speed and direction detectors	Wind speed and direction
Total precipitation sensor	Total collected precipitation since the sensor was last emptied and re-set.
Ice accretion sensor	Conditions conducive to the formation of ice.