Absolute humidity measures the total amount of water in the air. Unlike relative humidity, it does not change with air temperature. In automotive engineering, it is used to calculate engine combustion efficiency. High water vapor replaces oxygen in the air. This can cause a slight drop in engine power on humid days.
Car climate control systems also use absolute humidity sensors. These sensors calculate the workload needed to dry the air. This prevents the windows from fogging up while keeping the cabin comfortable.