Isotherms are contour lines on a weather map that connect points with equal temperatures. They show temperature gradients and are affected by factors such as elevation, water bodies, and latitude. The 32°F isotherm is important for predicting precipitation. Temperature advection occurs when winds blow across the isothermal gradient, causing extreme weather.
In meteorology, the term “isotherm” refers to a contour line connecting points on a weather map that have equal temperatures at any given time. Just as contour lines on topographic maps are used to show elevation gradients, isotherms are used to show temperature gradients. Isotherms are usually shown on maps at intervals of five or ten degrees. The temperature differences they delineate are often indicated by different colors.
The curve of an isotherm is shaped by the temperature changes in the area to be mapped. Factors affecting temperature include elevation, presence of water bodies, ocean currents, and latitude. Mountainous areas with a higher altitude are generally colder than lower-lying areas, causing the isotherms to bend strongly around these areas. Isotherms also curve at ocean-land boundaries due to the mitigating effect oceans have on extreme temperatures. Oceans have a higher specific heat than land, meaning it takes more heat or cold to raise or lower their temperature, so mid-ocean temperatures tend to be more stable than inland temperatures.
Temperature decreases with increasing latitude, so isotherms generally show a constant gradient as you move poleward. The Arctic Circle is often defined using the July isotherm of 50 degrees Fahrenheit (10 degrees Celsius). Although this isotherm moves based on climatic factors, it usually curves through the upper parts of Russia and Canada during July, circling the North Pole.
The isothermal gradient can vary according to the time of year. During the winter there is a greater variation of solar radiation, and therefore of the temperature, between low and high latitudes. This means that the isothermal gradient in the winter months is globally “steeper” than in the summer and isotherms on a map will appear closer together. In other words, the temperature variation across the distance from the equator to the pole is greater in winter than in summer.
The 32 degrees Fahrenheit (0 degrees Celsius) isotherm is an important weather indicator. This isotherm is of great importance for weather forecasting, because it shows the temperature line at which rain will freeze into sleet or snow. By following this isotherm at different atmospheric pressures, forecasters can predict the movement and accumulation of precipitation in a given area.
The process that produces occasional cloud cover and extreme weather is known as temperature advection. Temperature advection occurs in baroclinic regions, which means that winds blow across the isothermal gradient. Cold advection occurs when cold air is transported across isotherms to warmer areas, and warm advection occurs when warm air is transported to colder areas.
Protect your devices with Threat Protection by NordVPN
