What's that mean?

That means when the air that contains water vapor is being pushed up into the skies by upward forcing air mass, then clouds will form. Formation of the clouds means that the water vapor in the air is condensing to form the cloud. As a result, there is no rain so this will cause a drought. It's like taking all the water away from the surface and depositing them into the skies. So this causes drought to occur in the local area where the upward forcing air mass is located.

The Chinese translation is:

當包含水蒸的空氣一大堆地向天上迫使將導致天旱