Wednesday May 11, 2011 (El Nino and La Nina; Koppen Climates)

The Launch Pad Wednesday, 5/11/11 What is being illustrated in this picture?

Announcements Please check your yearly average in this class. If you are below 70 for the year, please come and see me ASAP! There are only two more grades remaining!

Assignments For This Six-WeeksDate IssuedDate Due Lab – Air Masses, the Mid-Latitude Cyclones, and Weather Maps 4/204/25 Lab Quiz - Air Masses, the Middle-Latitude Cyclone, and Weather Maps 5/3 Lab – Weather Maps5/45/6 Lab - National Weather Service Southern Regional Headquarters Local Weather Information 5/6 Test 105/10

El Niño El Niño is a warm countercurrent that flows southward along the coasts of Ecuador and Peru, usually during the Christmas season. This warm current blocks the upwelling of colder, nutrient-filled water, and anchovies starve from lack of food. The strongest El Niño events on record occurred between 1982– 83 and 1997–98.

El Niño The 1997–98 El Niño event caused heavy rains in Ecuador and Peru and ferocious storms in California. El Niño is related to large-scale atmospheric circulation. The pressure change between the eastern and western Pacific is called the Southern Oscillation. Changes in trade winds creates a major change in the equatorial current system, with warm water flowing eastward. El Nino effects are highly variable depending in part on the temperatures and size of the warm water pools.

Normal Conditions Figure A El Niño

La Niña La Niña events are the opposite of El Niño. La Niña is triggered by colder-than-average surface temperatures in the eastern Pacific. A typical La Niña winter blows colder than normal air over the Pacific Northwest and northern Great Plains, while warming much of the rest of the United States. Greater precipitation is expected in the Northwest during a La Niña year.

El Niño and La Niña Events associated with El Niño and La Niña are now understood to have a significant influence on the state of weather and climate almost everywhere.

World Climates and Global Climate Change

The Climate System Climate is an aggregate of weather. Climate involves the exchanges of energy and moisture that occur among the: atmosphere, hydrosphere, lithosphere, biosphere, and cryosphere (ice and snow)

Several components of Earth’s climate system.

World Climates All locations on Earth have a distinctive climate. The most important elements in a climatic description are: temperature, and precipitation.

Climate Classification A climate classification system brings order to large quantities of information, and many climatic-classification systems have been devised. The Köppen classification of climates is the best known and most widely used system. This system uses mean monthly and annual values of temperature and precipitation.

Climate Classification The Köppen classification of climates describes five principal climate groups: humid tropical (A) dry (B) humid middle-latitude with mild winters (C) humid middle-latitude with severe winters (D) polar (E) A, C, D, and E climates are defined on the basis of temperature characteristics. Precipitation is the primary criterion for the B group.

Climates of the World Based on the Köppen Classification Figure 20.4

Köppen Climates Humid Tropical (A) Climates These are winterless climates, with all months having a mean temperature above 64ºF. The two main types are: wet tropics, with high temperatures and year-round rainfall, luxuriant vegetation (tropical rain forest.) These climates exist in a discontinuous belt astride the equator, and are strongly influenced by the equatorial low pressures.

Köppen Climates Humid Tropical (A) Climates These are winterless climates, with all months having a mean temperature above 64ºF. The two main types are: tropical wet and dry, which are found poleward of wet tropics and equatorward of the tropical deserts. These climates consist of tropical grassland (savanna), with seasonal rainfall.

Comparison of A-Type Climates Figure 20.6