Page 256 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

220 part II The Water, Weather, and Climate Systems
(a) Doppler radar installation at Exeter, Ontario, operated by the Meteorological Service of Canada. The radar antenna is sheltered within the dome structure.
• Current weather
• State of the sky (current sky conditions)
• Visibility; vision obstruction (fog, haze)
• Precipitation since last observation
Environmental satellites are one of the key tools in forecasting weather and analyzing climate. Massive computers handle volumes of data from surface, air- craft, and orbital platforms for accurate forecasting of near-term weather. These data are also used for assess- ing climatic change. In Canada, the Meteorological Ser- vice of Canada provides forecasts at www.weatheroffice.gc.ca/ canada_e.html. In the United States, the National Weather Service (NWS) provides weather forecasts and current sat- ellite images (see www.nws.noaa.gov/). Internationally, the World Meteorological Organization coordinates weather information (see www.wmo.ch/).
An essential element of weather forecasting is Dop- pler radar. Using backscatter from two radar pulses, it detects the direction of moisture droplets toward or away from the radar source indicating wind direction and speed (Figure 8.11). This information is critical to making accurate severe storm warnings. As part of the Next Generation Weather Radar (NEXRAD) program, 31 WSR-88D (Weather Surveillance Radar) Doppler radar systems are operational through the Meteorological Ser- vice of Canada and the NWS operates 159 Doppler radar systems, mainly in the United States (radar.weather.gov/); installations also exist in Japan, Guam, South Korea, and the Azores. For links to weather maps, current forecasts, satellite images, and the latest radar, please go to the MasteringGeography website.
Weather information in Canada comes mainly from the Automated Weather Observing System (AWOS). AWOS sensor instrument arrays are a primary surface weather-observing network (Figure 8.11b). An AWOS
installation includes rain gauge (tipping bucket), tem- perature/dew-point sensor, barometer, present weather identifier, wind speed indi- cator, direction sensor, cloud height indicator, freezing rain sensor, thunderstorm sensor, and visibility sensor, among other items.
Automated stations use the Automatic Weather Ob- servation System (AWOS) developed in partnership between the Atmospheric
Environment Service and a private corporation. Canada currently has 31 upper air stations that send two ra- diosondes up each day at 1200 UTC and 0000 UTC. Additionally, there are six emergency stations and five Department of National Defence stations that occasion- ally produce upper air soundings. Nationally, there are 31 Doppler weather radar installations, 84 stations in the Canadian Lightning Detection Network, and over 800 hourly weather observation sites across the country. This includes 243 NAV Canada aviation observation sites, 243 Department of National Defence sites, and differing types of automated observation sites that have various types of observation equipment. There are 302 Reference Climate Stations (RCS sites) that record maximum and minimum temperatures and precipitation amounts twice a day. Finally, there are 1425 climate stations operated by volunteers. The numbers of hourly observation stations, reference climate stations, and volunteer climate stations change frequently.
Violent Weather
Weather is a continuous reminder that the flow of en- ergy across the latitudes can at times set into motion destructive, violent events. We focus in this chapter on ice storms, thunderstorms, tornadoes, and hurricanes; coverage of floods appears in Chapter 15 and coastal haz- ards in Chapter 16.
Weather is often front-page news. Weather-related destruction has risen more than 500% over the past three decades as population has increased in areas prone to vi- olent weather and as climate change intensifies weather anomalies. Canadian government research and monitor- ing of severe weather is part of the mandate of the Science and Technology branch of Environment Canada. Experts
(b) Automated Weather Observation System (AWOS) weather station.
◀Figure 8.11 NWS weather installation and AWOS weather instruments. [(a) Mary- Louise Byrne. (b) geoff Coulson Warning Prepared- ness Meteorologist environ- ment Canada.]
Animation
Midlatitude Cyclones