Presentation on theme: "Factors Affecting Wind Climate- A Wind of Change Friction Friction acts to slow air movement, which changes wind direction. Jet streams are fast-moving."— Presentation transcript:
Factors Affecting Wind Climate- A Wind of Change Friction Friction acts to slow air movement, which changes wind direction. Jet streams are fast-moving rivers of air that travel between 120 and 240 kilometers per hour in a west-to-east direction. Mountain-building can cause the jet to be force to move around it, causing climate changes locally.
Climate generalizations Find: Heat low, Bermuda High ITCZ
Local Winds Special Climate/Wind topics The local winds are caused either by topographic effects or by variations in surface composition—land and water—in the immediate area. In coastal areas during the warm summer months, the land surface is heated more intensely during the daylight hours than an adjacent body of water is heated. As a result, the air above the land surface heats, expands, and rises, creating an area of lower pressure. At night the reverse takes place. Land and Sea Breezes
Local Winds 19.3 Regional Wind Systems In mountainous regions during daylight hours, the air along the slopes of the mountains is heated more intensely than the air at the same elevation over the valley floor. Because this warmer air on the mountain slopes is less dense, it glides up along the slope and generates a valley breeze. After sunset the pattern may reverse. Valley and Mountain Breezes
Valley and Mountain Breezes: which one is the mountain breeze?
Reminder: Wind Systems The prevailing wind is the wind that blows more often from one direction than from any other. Wind Direction In the United States, the westerlies consistently move weather from west to east across the continent.
Monsoons are the seasonal reversal of wind direction associated with large continents, especially Asia. In winter, the wind blows from land to sea. In summer, the wind blows from sea to land.
El Ni ñ o and La Ni ñ a Ocean variables that effect climate: At irregular intervals of three to seven years*, these warm countercurrents become unusually strong and replace normally cold offshore waters with warm equatorial waters. (>intensity, >time) El Ni ño El Ni ñ o is the name given to the periodic warming of the ocean that occurs in the central and eastern Pacific. A major El Ni ñ o episode can cause extreme weather in many parts of the world.
Definition: Warm Waters in the eastern S. Pacific (Peru/Chile) El Niño Conditions
El Ni ñ o and La Ni ñ a Regional Wind Systems Researchers have come to recognize that when surface temperatures in the eastern Pacific are colder than average, a La Ni ñ a event is triggered that has a distinctive set of weather patterns. La Ni ñ a
Sea-Surface Temperatures: Using the color key below, is this situation an El Nino or a La Nina?
North Atlantic Oscillation index Negative NAO= colder winters in N. America and Europe..2008-9 (due to a weak Icelandic low subtropical high) Positive NAO= Mild and wet winters (due to stronger subtropical high pressure and a deep, lower than normal Icelandic low)
Volcanoes and Climate Particulates (Dust and Ash) Aerosols (Fine particles that stay aloft) Sulfur Dioxide (add water) If material is ejected into the stratosphere, it can remain for years, cooling the planet 1991 (Mt. Pinatubo), Tambora (1815) –Caused the “summer that wasn’t” (USA/Europe
THE SOLAR RADIATION VARIES DUE TO CHANGES IN EARTH’S TILT, REVOLUTION LESS INSOLATION IN HIGH LATITUDES IN SUMMER AN INCREASE IN SNOW, SO IT LASTS LONGER (ALBEDO) Milankovitch Theory: Orbital Variations and Glaciation (three)
66% more solar energy in Jan now. When more elliptical, 20-30% more energy at perihelion than aphelion. Presently, the orbital eccentricity is nearly at minimum.