Download CLIMATE CONTROLS

 CLIMATE CONTROLS‐‐LACEMOPS LACEMOPS is an acronym which summarizes all of the important controls on climate. These are Latitude, Air masses, Continentality, Elevation, Mountain barriers, Ocean currents, Pressure cells, and Storm tracks. Most climates will have some combination of these elements. Very few places are affected by all of them. Latitude. This is the main control on temperature. Tropical climates are hot, polar climates are cold due to differences in the energy received from the sun. Mid‐latitude climates are hot or cold, or moderate depending on season and other controls. Air Masses. The type of air masses that is typical of a place reveals much about the climate. Also seasonal changes and frequency of change are very important. For instance, the tropical wet and dry climates have two air masses, Maritime tropical during the wet season and Continental tropical during the dry season. Texas sees frequent changes in these two plus Continental polar air. However Cp air seldom visits Texas during the summer. Northwest Europe is controlled by Maritime polar air all the time. Continentality. This refers to the annual range in temperatures. The idea is that temperatures in the interior of a large land mass will change more with the seasons than the temps along the coast which are (may be) moderated by the ocean. The most "continental" locations are Central Canada and Siberia. These are large land masses at fairly northern latitudes and have differences in winter vs. summer temperatures of nearly 100 degrees F. Elevation. Generally the higher the elevation of a station, the cooler its temperature. Two good examples are Quito, Ecuador and Nairobi Kenya. Both of these cities are essentially on the equator in terms of latitude, but the climates are very pleasant because both are well over a mile above sea level. In contrast, some of the world’s highest recorded temperatures have been in places below sea level like Death Valley, Ca. and the Dead Sea in the Near East. Elevation will also have an effect on Precipitation patterns depending on a windward or leeward location. Certain mountain slopes in Hawaii receive over 350 inches of precipitation annually where the trade winds bring moisture laden breezes all the time. Mountain Barriers. Do not confuse this one with Elevation. This one is not so much about mountains as their "rain shadow" effect on the areas down wind from the mountains. Since all of the moisture is dropped in the windward side of the mountain range, there is a dry zone on the leeward side that can extend for hundreds of miles (downstream). The whole western U.S. is a rain shadow area because of the mountain ranges near the West Coast. Central Asia is another good example. Ocean Currents. This one is more subtle. Students always seem to overestimate the importance of this one. This does not apply to all stations that are located along the sea coast. It really refers to the temperature of the ocean current, and whether it makes the station warmer or cooler than it would be otherwise. A good example is San Francisco, Ca. where the cold California Current moves southward along the west coast and moderates the temperatures somewhat. Another example is Ireland and England which are much warmer that you might expect given their latitude. These are warmed by the Gulf Stream which brings relatively warm water across the Atlantic and warms these islands. This does not apply to Houston, TX. While there are currents off shore, they are not necessarily warm or cold given the latitude. It might apply if there were a cool current off shore which would make Houston lest hot and sticky, but, unfortunately for Houston, this is not the case. Pressure cells. Low pressure and High pressure cells are critical elements in climate. If Low pressure controls the weather most of the time, especially in the mid‐latitudes the place will be cool and wet (Seattle WA., Glasgow, Scotland). If high pressure controls the weather most of the time, especially in the tropics the place will be hot and dry, like Tucson, AZ, and Cairo, Egypt. Many places in the Mid‐latitudes see alternating low pressure (cyclonic storms) and high pressure (anticyclones) Kansas City, Mo. China and Southeast Asia are affected by the Asian Monsoon circulation which has low pressure, wet summers, and high pressure cold winters. Storm tracks. Large storm systems like cyclonic storms and hurricanes are more frequent in certain places and tend to follow paths (more or less). Thus certain places are in very stormy locations. The islands of the Caribbean region and the Philippines are subject to many hurricanes. The Northeastern U.S. and Northwestern Europe have many cyclonic storms.