Climate and Weather Forecasting

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Climate is a word that refers to weather, but does not actually describe the weather occurring in a certain area. Weather, by definition, is the CURRENT state or condition of the atmosphere at a GIVEN TIME and place.

Climate

Climate, on the other hand, describes the average weather conditions that could be expected during a certain time of year at a specific place. Climate is much less specific than a weather forecast… and the weather on a given day may not

actually reflect the expected climate for an area. For example, climatically in Virginia, during the month of November, the temperatures are usually in the 50’s However, the weather on a random day in November might actually be Sunny and 80… or snowy and 30.

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TEMPERATURE PRECIPITATION

Climate is determined by two major factors

TEMPERATURE FACTORS

1. Latitude - Low latitudes near tropics are warmer. - High latitudes near poles are colder.

2. Elevation - Valley cities are warmer. - Mountains are colder.

3. Closeness to body of water - Areas near water have smaller changes in temperature. Example: Los Angels does not get very warm in the summer or very cold in the winter.

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TEMPERATURE PRECIPITATION

Climate is determined by two major factors

PRECIPITATION FACTORS

1. Prevailing Winds - Prevailing winds push air masses across the country. - Winds blowing from the ocean bring moisture. Example: Seattle, Washington is very rainy.

2. Mountains Ranges - Mountains make air rise. - Rising air creates precipitation.

One way mountains influence precipitation on a climate scale is through the Rainshadow effect. The Rainshadow effect makes one side of a mountain wet, while the other side remains dry. An example of this would be the mountain ranges in the western United States. On the west side, or windward of the mountain ranges, air is forced upward, rises, cools, condenses and forms precipitation. However, after air cross the mountain peak, it sinks on the other side. Remember, sinking air makes clear skies… and therefore dry conditions. Most deserts are located on the east side, or leeward side of mountain ranges. NEXT

- Downwind - Air sinks - Air warms and dries - No precipitation

Leeward Side - Faces the wind - Air rises - Air cools and condenses - Precipitation occurs

Windward Side

The Rainshadow Effect

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In addition, another factor that influences our climate is the green house effect and global warming. Often, unfortunately, many people confuse these two terms and use them incorrectly and/or interchangeably. Let’s take a look at the difference and understand how each affects our climate.

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The Greenhouse Effect The greenhouse effect is a NATURAL, very beneficial process that takes place in our atmosphere. In short, energy from the sun enters our atmosphere, but is not absorbed by the gasses in the atmosphere, but rather by earth’s surface. Earth’s surface later re-radiates this energy back into the atmosphere and now certain the gasses in the atmosphere trap and absorb the energy. Those gasses are called greenhouse gasses. 1. Carbon Dioxide 2. Methane 3. Water Vapor

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This trapping of energy is a good thing. Without greenhouse gasses Earth would be wayyyy to cold to be a livable planet. The process gets its name because it works similar to a greenhouse.

Energy from the sun enters the greenhouse, but gets trapped and can not get out. This helps keep the plants warm.

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Some solar radiation is reflected by the Earth and the atmosphere

Solar radiation passes right through the atmosphere.

Most radiation is absorbed by Earth’s surface and warms it.

Infrared radiation (HEAT) is warmed by Earth’s surface and warms it.

Greenhouse gasses then trap this infrared radiation and bounce it back to Earth warming Earth more in the processes. The gasses act the glass walls of a greenhouse to trap the heat.

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Global Warming Global Warming on the other hand is an unnaturally change to the natural process of greenhouse. Humans that create excess amounts of greenhouse gasses, more than are naturally produced in the atmosphere, can speed up and increase the amount of energy trapped in Earth’s atmosphere. As a result, the planet warm much more than it would normally on its own. Humans greatest influence is increase the amount of Methane and Carbon dioxide in the atmosphere through the burning of fossil fuels in automobiles, factors, etc.

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Polar

Temperate Tropical

Climate Zones There are three major climate zones that have been established due to the temperature and precipitation factors we have just talked about. The three zones include:

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Polar

Temperate

Polar

Temperate

Tropical

Tropical

Polar From 60-90 degrees longitude. Cold climate.

Temperate From 23-60 degrees longitude. No extremes. In between temperature

Tropics From 0-23 degrees longitude. Very warm tempeartures.

Climate Change Over the years, the location and conditions of Earth’s climate has changed and continues to change. As Earth’s orbit and tilt changes, the locations where weather patterns, temperature patterns, precipitation patters, and climate in general sets up. This is one reason why Earth has gone through extreme changes like ice-ages.

Climate Change In addition, changes in the location of the continents and tectonic plates move, changes in sunspots, and solar output all also affect the climate.

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El Nino

-Named in 1891 by people in Peru

-Occurs around Christmas so El Nino means the Christ Child

-Occurs every 3 to 10 years

-The Trade Winds Weaken

-Cause surface water temperatures along the west coast of

of South America to rise

-This can cause Global Weather Patterns to change

-Increase in floods, typhoons in the Pacific Ocean

-Droughts may strike other areas such as Australia

La Nina

-Water is cooler than normal

-The Trade Winds cause these

temperature differences

-Weaker trade winds do not

push the warm water toward

Indonesia and this prevents

upwelling in Peru.

-Without warm water the

precipitation decreases in

Indonesia which results in

drought.

-In the US you get more storms

esp. in Texas, Gulf, and Florida.

-The Jet Stream shifts