January 15, 2015

Review Classic Cold Front:

-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

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- warm updrafts carry ice crystals up into the storm- water refreezes layer after layer- once the weight of the hailstone is greater than the updraft strength, it falls

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

January 15, 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

-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

-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

January 15, 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.

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

January 15, 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

- 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

- 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

January 15, 2015

- 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

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

- 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

-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

January 15, 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

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 towers

- 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

January 15, 2015

- 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

- 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)

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

January 15, 2015

- 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

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

Big Thompson Flood

- 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

- 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

January 15, 2015

- 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

- 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

January 15, 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

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January 15, 2015

January 15, 2015

January 15, 2015

January 15, 2015