The shape of the curve on the isobaric surface at different heights of the atmosphere is changing all the time, which can be summarized into several basic types: high pressure, low pressure, high pressure ridge, low pressure trough and saddle shaped pressure area.
(1) Low atmospheric pressure
The spatial isobaric surface of a pressure system whose central pressure is lower than the surrounding pressure is shaped like a valley, which is shown as a set of closed curves on the graph. according to White Bellow's law , the airflow in the low-pressure area rotates counterclockwise in the Northern Hemisphere, called cyclone 。 For the lower atmosphere, the ground friction not only reduces the wind speed, but also makes the wind direction incline to the low pressure, which makes the air flow flow and rise from the periphery to the center of the low pressure, so the low pressure area often has cloud and rain weather. (2) High barometric pressure
The air pressure system whose center air pressure is higher than the surrounding air pressure, the shape of its spatial isobaric surface is like a mountain peak, and the figure shows a group of closed curves. The airflow in the high pressure area rotates clockwise in the Northern Hemisphere, called Anticyclone 。 The lower atmosphere in the high pressure area diffuses outward, making the high air flow sink, so the weather in the high pressure area is fine [2] 。 
Low and high air pressure (3) Low pressure tank
The weather characteristics near the low pressure trough are similar to the low pressure in the long and narrow area with high pressure extending from the low pressure area.
(4) High pressure ridge
The narrow and long area with high air pressure extending from the high pressure zone has the shape of the spatial isobaric surface like a ridge, and the weather characteristics near the high pressure ridge are similar to the high pressure.
(5) Saddle shaped pressure zone
In the middle area composed of two high pressures or two low pressures, the shape of the spatial isobaric surface is like a saddle. When the saddle type pressure field was first established, the wind speed was low, the wind direction was variable, and the pressure value was relatively stable. However, severe weather changes may occur soon.
