A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve along which the function has a constant value.[1] It is a cross-section of the three-dimensional graph of the function f(x, y) parallel to the x, y plane. In cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level.[2] A contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness of slopes.[3] The contour interval of a contour map is the difference in elevation between successive contour lines.[4]
More generally, a contour line for a function of two variables is a curve connecting points where the function has the same particular value. The gradient of the function is always perpendicular to the contour lines. When the lines are close together the magnitude of the gradient is large: the variation is steep. A level set is a generalization of a contour line for functions of any number of variables.
Contour lines are curved, straight or a mixture of both lines on a map describing the intersection of a real or hypothetical surface with one or more horizontal planes. The configuration of these contours allows map readers to infer relative gradient of a parameter and estimate that parameter at specific places. Contour lines may be either traced on a visible three-dimensional model of the surface, as when a photogrammetrist viewing a stereo-model plots elevation contours, or interpolated from estimated surface elevations, as when a computer program threads contours through a network of observation points of area centroids. In the latter case, the method ofinterpolation affects the reliability of individual isolines and their portrayal of slope, pits and peaks.<span>[5]</span>
Katrina made landfall as a Category 3 storm near Buras-Triumph, Louisiana, and once more near the Mississippi/Louisiana border. Katrina progressed northward through the central United States and finally dissipated near the Great Lakes on August 31, when it was absorbed by a cold front.
Chris's city is in a wet tropical climate.
High amount of precipitation, and warm humid climate is typical for the regions around the Equator, thus the climate in which Chris's city is located seems to belong to a tropical wet climate type, somewhere around the Equator.
Mark's city is in a cold desert climate.
The big variation of temperatures, with having hot summers and cold winters, as well as extremely low amount of precipitation, are typical for the cold deserts that are mostly dispersed in Asia, thus the city in which Mark lives will belong to a cold desert climate.
