Generally, the gage is put in the atmosphere, it can only measure the difference between the absolute pressure and local atmospheric pressure. It can not give out the absolute pressure.
测量压力的仪表通常处于大气环境中，不能直接测量出绝对压力，显示的是绝对压力和当时当地大气压的差值。
3
The more instable the stratification of the atmosphere and the smaller the absolute and relative angular velocities, the more likely it forms the spiral wave.