December 04, 2015

Review Classic Cold Front:

A cold front is the leading edge of a mass of cold air as it displaces a warmer mass of air at ground level.

Cold air is denser than hot air (hot air balloons rise) and so as a cold front advances it slides under the warmer air forcing it up. As the warm air is forced up its moisture condenses. This movement of moist air upwards is often quite dramatic and this can lead to bad weather: heavy downpours, often thunderstorms.

This brief band of very unsettled weather and high winds is typically followed by three things. There will be a shift in wind direction and there will also be a drop in temperature and a big improvement in visibility, often very clear air and skies.

December 04, 2015

-when cold air moves into an area occupied by warm air, the cold air "scoops up" warm air and pushes it violently up into the atmosphere-moisture in the warm air cools and condenses to form clouds- as more and more clouds form, the storm increases in intensity until moisture is released- heavy rain/ snow/ hail falls- after the cold front passes and the storm dies, the weather becomes clear and drier

video clip

- when a thunderstorm drops heavy rain onto (1) saturated ground or (2) non-absorbent rocksall the rainfall becomes runoff and causes flash flood

December 04, 2015

- high wind can snap branches- branches commonly fall on power lines causing power outages for hundreds → thousands

-only if the thunderstorm becomes a supercell

Lab: Thunderstorms and Lightning6 pages

-lightning is an electrical discharge between:(1) a thundercloud and the ground(2) between different parts of the same cloud- occurs when electrical energy in a cloud exceeds the high resistance of air- 30,000amp and 1 billion volts-up to 54,000°F = 6 times hotter than the surface of the sun

December 04, 2015

-lightning is an electrical discharge between:(1) a thundercloud and the ground(2) between different parts of the same cloud- occurs when electrical energy in a cloud exceeds the high resistance of air- 30,000amp and 1 billion volts-up to 54,000°F = 6 times hotter than the surface of the sun

-lightning is an electrical discharge between:(1) a thundercloud and the ground(2) between different parts of the same cloud- occurs when electrical energy in a cloud exceeds the high resistance of air- 30,000amp and 1 billion volts-up to 54,000°F = 6 times hotter than the surface of the sun

December 04, 2015

-up drafts carry tiny ice crystals up into a thunderstorm- as crystals collide with each other, electrons are stripped away- now rising ice crystals charge the top of the cloud positive- the electrons gather at the bottom of the cloud giving a negative charge- a stream of negative electrons extends down from bottom of cloud in zig-zag pattern toward ground = step leader

-as step leader approaches ground, it pulls up a stream of positive charges from objects on the ground = positive streamer (Ex: St Elmos Fire)- as a step leader touches a positive streamer, the electrical circuit is complete = bolt of lightning- this repeats several times per second until the negative charges are drained from the thundercloudhandout

December 04, 2015

Ex: (Transient Luminous Events) sprites, blue jets, ball lighting, green elves- most are poorly understood but considered to be real electrical phenomena

St Elmos Fire is matter called plasma, formed on pointed objects like ship masts, lighting rods, chimneys, the electrical field ionizes the air molecules and glows blue or violet.Ball Lighting is spherical lightning possibly caused by silicon vaporization. Elf is a transient luminous event in the upper atmosphere, much higher in the atmosphere than normal lightingSprites are luminous, red-orange flashes high in the atmosphere, well above the normal altitude for lightning. Sprites are cold plasma discharges, unlike normal lightning which is hot plasma.

December 04, 2015

- in the US lightning strikes start about 15,000 fires per year- very dangerous in areas with low rainfall or drought

December 04, 2015

- in the US, about 100 deaths per year and another 500 injured* more deaths than by tornados or blizzards- about 20% of victims die immediately of a heart attack-survivors of lightning strikes often have serious health issues for years or for rest of life- Keraunopathy = medical science of studying lighting strikes to the human body- Side Flash = when lightning bolt strikes a tree then jumps to a nearby person

December 04, 2015

- drought is an interruption in the water cycle- the amount of precipitation is much much less than evaporation and transpiration- drought can result from many reasons, but one main reason is High pressure weather systems- high pressure weather is low humidity, clear, cloudless skies* drought cycles are linked to La Nina cycles in the Pacific Ocean

- drought is an interruption in the water cycle- the amount of precipitation is much much less than evaporation and transpiration- drought can result from many reasons, but one main reason is High pressure weather systems- high pressure weather is low humidity, clear, cloudless skies* drought cycles are linked to La Nina cycles in the Pacific Ocean

December 04, 2015

- severe water shortage - it may not rain for years- produces dry, desert conditionsEx: Death Valley, California- often, wind blown sand and dust covers the regionEx: Sahara Desert

-shortage of rainfall in a predictable seasonal weather cycles Ex: the extreme dry season on the African Savannah- due to normal regional weather patterns

December 04, 2015

- occurs in an area that may receive a few rain showers but not nearly enough to keep up with(1) sweltering summer heat(2) high evaporation rateEx: most of Texas and southern Arizona

- farmers and ranchers depend on large volumes of water for their crops and livestock- in a drought, crops wither and die, livestock dehydrate and die * creates food shortages, increased food prices* farmers and ranchers can lose their land

December 04, 2015

-in many Third World counties (Ex: Ethiopia) thousands of people suffer from the effects of drought- crops won't grow- children die- farm animals die- generates refugees and mass homelessness- in US water rationing can affect industry and other businesses that utilize water- often drives up prices of consumer goods

- modern farms tractors and machinery came into widespread use in the late 1920's- thousands of farmers in the midwest plowed under the native drought-resistant grasses and planted drought-sensitive wheat- in early 1930's, a long drought set in for Oklahoma, Colorado, New Mexico, and Texas* as the drought worsened, the wheat crop failed and the topsoil became very dry and crumbly** strong winds blew dust away form the farmland and formed huge dust storms = black Blizzards- in 1932 there were 14 black blizzards- in 1933 there were 39 black blizzards- by 1934 35 million acres of topsoil was stripped from the land and millions of farms were abandoned

December 04, 2015

- modern farms tractors and machinery came into widespread use in the late 1920's- thousands of farmers in the midwest plowed under the native drought-resistant grasses and planted drought-sensitive wheat- in early 1930's, a long drought set in for Oklahoma, Colorado, New Mexico, and Texas* as the drought worsened, the wheat crop failed and the topsoil became very dry and crumbly

** strong winds blew dust away form the farmland and formed huge dust storms = black Blizzards- in 1932 there were 14 black blizzards- in 1933 there were 39 black blizzards- by 1934 35 million acres of topsoil was stripped from the land and millions of farms were abandoned

December 04, 2015

Rains did not return until 1939

- during prolonged drought, many cities in SW US impose water usage bansEx: fines for watering lawns- consumer products; washers, showers fixtures, decrease amount of water used by the household* all in an effort to conserve water in reservoirs and water towersVideos: California DroughtMega Drought

December 04, 2015

- a heavy rainstorm or series of storms can drop 4 - 5 inches of water in a short period of time in a region- in spring, snow melt in mountains can overwhelm local streams, cannot handle this volume of water

- dry land can actually resist water seeping in- difficult for the water molecules to absorb into the ground- thus, all the rain turn into runoff and no water is added to the ground

December 04, 2015

- hurricanes and tsunamis deliver huge amounts of water that an area cannot handle

- when a river cannot contain all the water flowing within it- water flows over the flood plain ( a flood plain is an area of low lying ground adjacent to a river)

December 04, 2015

- when ocean levels rise and overcome any levees or barriers- usually occurs in a hurricane storm surge

- due to large amounts of rain, usually in high elevation, mountainous areas- water flows rapidly down a canyon and spills out into valleys, where towns are usually located- can come and go within 6 hours, very unpredictable

December 04, 2015

- due to totally unexpected situationsEx: hurricane storm surge, tsunami caused by an underwater earthquake, a dam fails and reservoir water is released

Portfolio: Big Thompson Flood due 5/29Homework: Floods due 5/27

- large scale flooding destroys thousands of acres of crops and drowns thousands of farm animals- very often, farmers suffer total loss and must declare bankruptcy- loss of crops/animals will drive up food prices - in 3rd word countries, this leads to widespread starvation and disease

December 04, 2015

- major flooding events can wipe out entire villages/ towns and render homes uninhabitable

Ex: 1931 China - Yangze and Yellow Rivers flooded and forces 2 - 4 million people to be homeless

- flood waters can mix with water from sewage plants, industrial plants and landfills- once the flood waters recede, thick mud is left and is contaminated with feces, industrial chemicals etc...- these toxic muds must be safely disposed of in special landfills

December 04, 2015

- many costal cities and regions build seawalls and levees to protect from floodingEx: New Orleans, Holland- usually good for small flooding events, but often inadequate for larger flooding events- very expensive to build and maintain

- Weather experts on TV and radio can predict flooding and give ample warning- in terms of larger storms: Ex: Hurricane Sandy - there may be mandatory evacuation from low lying areas and places prone to flooding

December 04, 2015

- need zero degree temperatures in the clouds and near the ground

- condensation of water vapor leads to snow and ice pellets forming

- typically warm air is rising because it is less dense, this raises the moisture into the cold air

December 04, 2015

two kinds of snowstorms1) Flurry or Shower = snow falling of varying intensity, but for brief time2) Squall - brief but intense snowstorm accompanied by strong, gusty winds

Video: Buffalo Blizzard

= raindrops that freeze before hitting ground- sleet usually bounces up if it strikes a solid surface

December 04, 2015

= raindrops that fall onto a surface that is below 0°C or 32°F- rain instantly freezes forming a coating or glaze of ice

- Heavy snowfall and drifting snow can immobilize a region or paralyze a cityEx: shut down all car, train, bus, plane travel, close schools and businesses - Strong winds can create whiteout conditions, reducing visibility to near zero- Homes in rural areas may be isolated for days or weeks until plows can clear roads

Homework: Donner Pass

December 04, 2015

-Can cause frostbite or hypothermia, both can be life- threateningFrostbite: common in fingers, toes, ears, nose - freezing and death of body tissuesHypothermia: drop in body temperatureSymptoms: uncontrolled shivering, slow speech, exhaustion, drowsiness

- occurs in early winter months when a large lake has not frozen over- the water is relatively warm compared to the air -evaporation takes place, fuels existing storm, causes large accumulations of heavy wet snow

Internet Lab: Blizzards and Winter Storms

December 04, 2015

Ex: tree limbs fall and take out power lines- car accidents increase as roads ice up and whiteouts occur- can burst water pipes - weight of snow can collapse roofs

- ice can bring down trees, power lines etc- virtually impossible to driveEx: surprise ice storm Oct 2006, Buffalo40,000 without power4 died

December 04, 2015

will explore next

- try to stay dry- find any shelter whatsoever- cover exposed skin

December 04, 2015

- run engine for only 10 minutes per hour- make sure the exhaust pipe is clear- exercise as best you can- keep an emergency kit in your car*include energy bars or candy

December 04, 2015

- most common cause is hot dry drought weather conditions that dries out the vegetation, becomes very easy to igniteother causes: lightning strikes, slash and burn agriculture, accidents, arson

= leading edge of an advancing fire- temps up to 1600°F, which can melt some metals- can travel up to 30 mph-wind gusts up to 80 mph in advance of front

December 04, 2015

b) pyrocumulus cloud

- a cloud like structure above a wildfire- consists mostly of smoke and ash

- a large wildfire can release trillions of tons of CO2 into the atmosphere, contributes to global warming* firefighters can die if they breathe in the CO2

December 04, 2015

- can divert or shut down air travel- smoke and ash can cross highways and railroad lines, stopping them

- many families have homes in mountain canyons-risk losing house to fire because very hard to fight- fewer fire hydrants- roads may be blocked by fire