What Is a Temperature Gradient?

Temperature gradient (temperature gradient) is a stepwise increase or decrease in natural air temperature, water temperature or soil temperature with the change of land height or water area and soil depth. It is a physical quantity that describes the direction in which the most rapid change in temperature in a particular area environment will go, and at what rate.

Temperature gradient is a physical quantity that describes the direction in which the temperature changes most rapidly in a specific regional environment, and at what rate; in nature, air temperature, water temperature, or soil temperature varies with land height or water area and soil depth. Out

Calculated from the troposphere to the ground

The troposphere is located from the ground to an altitude of 12 kilometers. The temperature in the troposphere decreases with increasing altitude, which is about 6.5 ° C decrease per 1 km. Due to the large temperature change, the air is unstable and convection occurs. All meteorological changes occur in this layer.

Temperature gradient is closely related to biological activity and biological distribution

The growth, development and reproduction of various organisms have a certain temperature range. Temperatures outside the temperature range affect the normal life activities of the organism and even cause death. Temperature gradients in nature limit the activity and distribution of organisms. For example, when the surface temperature of a lake rises, some plankton move to the lower waters, and other organisms that feed on it also move to the area. For another example, the vertical distribution of the vegetation on Mount Emei in China is determined by the vertical temperature gradient of the mountain: the vegetation in the hilly areas below 600 meters is mainly evergreen broad-leaved forests, and the low mountain zones between 600 and 1100 meters are evergreen broad-leaved forests, Deciduous broad-leaved forest and coniferous mixed forest. The 1100-1900 m middle mountain belt is deciduous broad-leaved forest and coniferous mixed forest, the 1900-2800 m alpine belt is coniferous forest, and the area above 2800 m is alpine meadow. The distribution of birds there also varies with vegetation; thrushes are predominant in the Zhongshan Belt, and salamanders are mainly in the Alpine Belt. Breeding birds above the Zhongshan Belt are mainly Pheasants.

Vertical geographic differentiation

The temperature gradient varies not only with the seasons, but also with the topography. For example, in China, the northern slope of the Qinling Mountains is smaller than the southern slope. The annual average temperature gradient of the northern slope is -0.45 / 100 meters, but the southern slope is -0.54 . /100 metres. The main reason is that in winter, cold air often accumulates on the northern slope, reducing the temperature difference between the basin and the mountains. The monthly temperature gradient in winter on the north slope is only -0.34 / 100 meters, while the south slope is in the northerly position of cold air currents, and there is still -0.54 / 100 meters in January, but this situation does not exist in summer. The gradients are all -0.55 ° C / 100 meters.

In China, the effect of horizontal temperature gradients on vegetation distribution due to latitude differences is also obvious. Generally, the northeast plain is a forest steppe zone, north China is a summer green forest zone, and the middle and lower reaches of the Yangtze River are a mixture of deciduous broad-leaved forest and evergreen broad-leaved Forest belt, Jiangnan hills and Nanling are evergreen forests, southeast coast and Hainan Island are tropical rain forests and monsoon forests. There are also large differences in the distribution of crops: wheat, cotton, and miscellaneous grains dominate the North China Plain, while rice is dominated by the Jiangnan hills, the Sichuan Basin, and the southeast coast. In addition, due to the adjustment of the free atmosphere, the annual and daily temperature changes in the mountains decrease with increasing altitude. The difference between the temperature of the hottest month minus the temperature of the coldest month is used to represent the annual change, which is called annual comparison. difference. The annual difference in Jiujiang is 25.2 , and it will drop to 22.7 in Lushan. The annual difference may not only vary with the height, but also because of the different aspect. Xi'an, north of the Qinling Mountains, has an annual difference of 27.6 ° C, and it has dropped to 24.2 ° C to Huashan. However, the Ankang years south of the Qinling Mountains are only 24.2 ° C, which is almost the same as Huashan.

Animal distribution and migration are determined by temperature gradients

For example, in China, the salamander is mainly distributed in the area south of 36 ° north latitude. The armyworm migrates south in autumn because it cannot overwinter in northeast or north China. Migratory birds migrate south to find suitable temperature areas for winter. In addition, the number of generations of polymorphic insects in different latitudes is different, and generally decreases with increasing latitude. For example, the second generation of locusts occurs at 35 ° north latitude and the third generation occurs at 23 ° north latitude.

One of the conditions for the product of the conflict between the heating and cooling groups

The heat exchange between the cooling and heating groups on both sides of the front and the underlying surface is always at the same time, which affects the change of the temperature level gradient on both sides of the front. If the cold and heating groups stay on the colder and warmer mats, the result of the heat exchange may make the cold air groups become colder, the heating groups become warmer, and the temperature gradient between the cold and heating groups increases. Large, front is strengthened, but this situation is rare in nature. In most cases, the air masses on both sides of the front migrate to the ground surface with similar properties, regardless of whether the surface temperature is lower than the cold air mass or warmer than the warm air mass, or somewhere in between. As a result, either the heating group loses more heat or the cold air group gets hotter, it will reduce the temperature gradient between the cold and heating groups, which is beneficial to the sharpening. Therefore, the non-adiabatic change of the air mass is generally conducive to frontal dissipation. The distribution of water vapor in the atmosphere is very uneven. Under normal circumstances, there is more water vapor in the heating mass and less water vapor in the cold air mass. Therefore, cloud formation and rain mainly occur in the heating mass, and the released latent heat of condensation is mainly concentrated in One side of the heating group in the front area will increase the temperature gradient between the heating and cooling groups, becoming one of the conditions for generating the front.