What are the characteristics of temperature and wind distribution on both sides of the front?

Frontal is a three-dimensional weather system. It is not a geometric surface, but an irregular inclined plane. There is cold air under it and warm air above it. Because cold air is heavier than warm air, their joint area is inclined.

quasi-stationary front

Transition area. The interface near the warm air mass is called the upper boundary of the front, and the interface near the cold air mass is called the lower boundary of the front. The horizontal distance between the upper and lower boundaries is called the leading edge width. The near-surface layer is about tens of kilometers wide and the top layer can reach 200-400 kilometers. This width is very small compared with its horizontal length (hundreds to thousands of kilometers). Therefore, people often regard it as a curved surface approximately, which is called the front. The area where the front intersects the plane in the air is called the front area (the area between the upper bound and the lower bound).

The front is a transitional zone where two air masses with different properties interact, so the meteorological factors such as temperature, humidity, stability, wind, cloud and air pressure on both sides of the front are different.

Obviously, the front can be regarded as a discontinuity of meteorological elements in the atmosphere.

(1) Frontal slope: Frontal slope to cold area with a certain slope in space. The front is inclined in space, which is an important feature. The formation and maintenance of the front slope is the result of the earth's deflection force. The slope of the general front is around 1/50- 1/200. Because the slope of the front is very small, the area covered by the front is bound to be large. For example, a front with a slope of1100, a front length of 1000 km and a height of 100km can cover an area of1000,000 square kilometers; Because of the slope, warm air can rise along the slope, which provides favorable conditions for the formation of rainy weather.

(2) Sudden change of meteorological elements: There is little difference in temperature, humidity, air pressure and other meteorological elements inside the air mass, but there is great difference on both sides of the front.

① Temperature field: The horizontal distribution of air temperature in the air mass is relatively uniform. Usually, the temperature difference within 100 km is 1℃, and the maximum is 2℃. In the area near the front, the temperature difference in the horizontal direction is very obvious, which can be close to 10℃ within the horizontal distance of 100 km, which is 5- 10 times larger than the temperature difference in the air mass; In the vertical direction, the vertical distribution of temperature in the air mass decreases with height. But near the front area, because the lower part is a cold air mass and the upper part is a warm air mass, the temperature difference between the upper and lower parts of the front area is quite large, and the front area is often an inversion layer.

② Pressure field: There are cold and warm air masses with different densities on both sides of the front, so the pressure change in the front area is much greater than that in the air mass. The pressure distribution near the front is uneven. The front is in an air pressure trough, and the isobar has an angle pointing to the high pressure through the front, or the front is in a relatively low pressure area between two high pressures, and the isobar is almost parallel to the front.

(3) Wind field near the front: the wind has obvious inverse transformation on both sides of the front, that is, from the back of the front to the front, the wind direction changes counterclockwise.

(3) The weather near the front changes dramatically: Due to the gradient of the front and the intersection of cold and warm air, warm air can rise or be forced to rise along the slope, and the warm air contains more water vapor, so the air rises adiabatically and the water vapor condenses, which is easy to form rainy weather. Because the front is an area where the level of various meteorological elements is quite different, the energy is concentrated and the weather changes dramatically. Therefore, the front is an area where the weather changes dramatically.