The compound NF3 is quite stable, but NCl3 is very unstable (NCl3 was first synthesized in 1811 by P. L. Dulong, who lost three fingers and an eye studying its properties). The compounds NBr3 and NI3 are rare, although the explosive compound NI3 NH3 is known. Account for the instability of these halides of nitrogen.
418 Development of Extratropical Cyclone Geographic Regions at Risk for cyclones •Most serious threat in North America –Eastern contiguous United States –Puerto Rico –Virgin Islands –U.S. territories in the Pacific Ocean •They are a lesser threat to Hawai’i and Atlantic Canada •On the Pacific coast, hurricanes strike Baja California and the west coast of the Mexican mainland Cont. •Most hurricanes that affect East and Gulf Coasts form off the western coast of Africa •They take one of three tracks 1.West toward East coast of Florida, sometimes passing over Caribbean •Move out into the Atlantic Ocean to the northeast 2.Westward over Cuba and into the Gulf of Mexico to strike the Gulf Coast 3.Westward to the Caribbean and then northeastward skirting the East Coast •May strike the continent from central Florida to New York Cont. •Northwest Pacific is much more active than North Atlantic •Indian Ocean is also a very active hurricane zone •South Atlantic and southeast Pacific, rarely have hurricanes because of cold ocean water •Hurricanes do not form close to the equator because of the absence of the Coriolis effect Hazard Greatest in Right Forward Quadrant of Atlantic Hurricanes •Local rise in sea level resulting from storm winds •Can be > 3 m (10 ft.) •Because of spinning, surge is greatest in right quadrant of storm as it makes landfall •Height is greatest near time of maximum winds •Height is also greater if landfall coincides with high tide Storm Surge •Largest effect from stress exerted by wind on water –Fetch refers to the area over which the wind blows –Larger fetch results in larger storm surge •Smaller effect from low atmospheric pressure in storm pulling up on water surface •Also depends on shape of coastline •Continual increase in sea level as storm approaches •Overwash can create washover channels, isolating one area from another Heavy Rains •Average hurricane produces trillion gallons of water each day •Rainfall from cyclones can cause inland flooding •Flooding affected by: –Storm’s speed –Land elevation over which the storm moves –Interaction with other weather systems –Amount of water in soil, streams, and lakes prior to storm Linkages and Natural Services •Coastal erosion –Some of the fastest rates during the landfall of cyclones •Some sand replaced during fairweather conditions •Other sand is removed entirely •Flooding –Saltwater from storm surge –Freshwater from heavy rains •Mass wasting –Heavy rains can cause devastating landslides and debris flows •Primary source of precipitation •Redistribute warm air from tropics •Maintain ecosystems –Winds carry plants, animals, and microorganisms –Waves stir up deeper, nutrientrich waters –Winds topple weak and diseased trees in forests –Waves break apart some corals Human Interaction with Cyclones •Human i–Population growth greatest in coastal areasdly in the past four decades –About 53 percent of United States population live in coastal counties •Urban development in coastal areas –Urbanization of vulnerable coastlines increases magnitude of the effect of cyclones –Destruction of sand dunes makes areas more susceptible to hurricane winds –Construction (increase) of seawalls and bulkheads reflect waves and contribute to beach erosion –Poor building materials and practices can make hurricanes more dangerous to people cont. •Global warming may contribute to higher intensity and frequency of hurricanes in the future –Raising temperatures of the seas surface •Possible that warmer ocean water will increase hurricane intensity –Contributing to rising sea level •Increase the reach of large waves that ride the surge Forecasts and Warnings •Cannot prevent the cyclone hazard •Enforcing building codes and evacuation procedures Need for accurately forecasts and warnings •Forecast includes: –If it will make landfall –Where and when it will strike –Wind strength –Width of affected area –Rainfall amount –Storm surge •Monitored by U.S. Hurricane Center, Canadian Hurricane Center •Hurricane watch means likely hurricane in 36 hours •Hurricane warning given when hurricane is likely within 24 hours or less Cont. •Hurricane forecasting tools –Weather satellites •Detect early warning signs •Can not show wind speed –Aircraft •U.S. Air Force, NOAA airplanes fly into the storm to collect data –Doppler radar •Give information on rainfall, wind speed, and direction of the storm –Weather buoys •Continuously record weather conditions –Computer models •Make predictions about storm tracks •Global Forecast System (GFS) model runs four times a day •Still not completely accurate in predicting storm intensity Cont. Storm Surge predictions = Time and elevation of surge Based on wind speed, fetch, ave, water depth, central pressure, forward speed Adjustment to Cyclones Hurricanes and Extratropical Cyclones •Community adjustments to cyclone hazard –Warning systems •Give public maximum possible advance notice •Media broadcasts, local use of sirens –Evacuation plans and shelters •Developed prior to hurricane season •Public transportation provided during hazard –Insurance –Building design •Withstand hurricaneforce winds •Allow passage of storm surge •Recommendations available from Partnerships for Advancing Technology in Housing (PATH) •Personal adjustments to cyclone hazard –Be aware of hurricane season –Prepare homes and property for hazard –Obtain flood insurance –Install heavy shutters that can be latched –Learn evacuation route –Make a family emergency plan –Collect emergency supplies Chapter 11 Coastal Hazards Folly Island and Submerging Coast Barrier island south of Charleston, SC Barrier to ocean waves that would strike the mainland About 10 km (~6mi) long, less than 1 km (0.6mi) wide Most of the island has an elevation of l.5.3 m (~510 ft.) Typical Atlantic Barrier Island Eroding at a high rate (proceed to the slides where 11.1 occurs to the powerpoint)