Isobaric surface refers to the surface with the same air pressure.Connect the pressure in a space full of equilibrium fluidequalThe surface composed of points with equal air pressure in space.In general, due to the unequal pressure at the same altitude, the isobaric surface is not flat in space, but undulating like the terrain.
The air pressure is different because of the difference between the altitude and the cold and hot ground. Generally speaking, the value of the isobaric surface decreases with the rise of the altitude in the vertical direction. If the nature of the ground is uniform, and the nature of the atmosphere is also uniform, then the isobaric surface is parallel to each other, otherwise it is ups and downs.Isobaric surface is a surface composed of points with equal air pressure in space.Since the air pressure is not equal at the same height, the isobaric surface is not flat in space, but undulating like the terrain.
Using the method of drawing topographic map, the undulating isobaric surface is projected onto the plan with contour lines to formIsobaric diagram。[1]On the isobaric surface, the contour line is used to represent the spatial distribution of air pressure.The bulge of the isobaric surface indicates that at the same height, the air pressure is higher than that around.On the isobaric surface, it is a high value area composed of a group of closed contour lines, namelyHigh pressure area。The concave isobaric surface indicates that the air pressure at the same height is lower than that around.On the isobaric surface, it is a low value area composed of a group of closed contour lines, that isLow pressure area。Therefore, on the isobaric surface, the distribution of contour lines can reflect the fluctuation of the isobaric surface and indicate the spatial distribution of air pressure.
The height of isobaric surface is notGeometric height, butGeopotential height。The geopotential height is expressed by the work done by a unit mass object to overcome gravity when it is lifted from sea level to a certain height in space.There are 850 hPa, 700 hPa and 500 hPa isobaric maps commonly used in meteorology.The combination of isobaric maps at different heights can not only reflect the spatial distribution of high pressure, low pressure and other weather systems in Dafan area, but also reflect the structure and evolution law of the upper atmosphere. It is a large-scale weathersituationBasis of forecast.
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aboutIsobarRead: Pay attention to the numerical value.GenerallyIsobaric、Isobars。Generally, the isobaric distance between every two isobars in a picture is equal, so as long as you know the value of two of them, you can deduce the value of any one of them.If the isobaric line is closed, the center with large value is the high-pressure center, also calledAnticyclone。
The weather under its control is sunny, otherwise it is the center of low pressurecallcyclone, under its control is rainy weather.Of course, you can also judge the size of the wind force according to the density of the isobars.
Advantages of isobaric surface
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When the vertical coordinate is expressed in height, the geostrophic wind formula is:
If the barometric coordinate is used (i.e. on the isobaric surface), the geostrophic wind formula is:
Obviously, the geostrophic wind calculation on the isobaric surface will not have a density variable, which is more convenient than that in the altitude coordinate system.thereforeWeather analysisThe vertical coordinate of atmospheric pressure is generally used in the prediction, that is, analysis and calculation on the isobaric surface.[1]
Characteristics of isobaric surface
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The characteristic of the isobaric surface is that the isobaric surface is alwaysMass forceOrthogonal.
Therefore, given the direction of the mass force, the direction of the isobaric surface can be obtained;On the contrary, if the direction of the isobaric surface is known, the direction of the mass force can be determined.[2]
