Why is the precipitation area located in the trough of low pressure indicating that the river area is a front? What does the trough look like? What's the weather like at the ridge of high pressure? th

Why is the precipitation area located in the trough of low pressure indicating that the river area is a front? What does the trough look like? What's the weather like at the ridge of high pressure? thank you

It's not always rainy below the trough, but mainly in front of the trough.

It can be deduced from the formula that there is vorticity advection in front of the trough, so that the air on the ground will converge and rise, and the rising airflow is easy to condense water vapor and form precipitation, which is called "bad weather behind the ridge in front of the trough", while the negative vorticity advection behind the trough is conducive to airflow sinking, while downward flow is not conducive to water vapor condensation, so the weather is mostly sunny.

The lower part of the trough often corresponds to a weather system such as a cold front, which is the intersection of cold and warm air masses. If the cold front crosses the border, it will easily lead to strong convective weather, and precipitation will often occur at this time, but if there is no cold air going south, the probability of precipitation below the trough will be relatively small

The cold front precipitation will be behind the front. Warm wind and precipitation are in front of the front (this textbook has a reason)