Speaking of composition, it is said that water vapor in the air accounts for 0.03%, and the weather forecast usually says 50%. Why is it different?

Speaking of composition, it is said that water vapor in the air accounts for 0.03%, and it is absolute humidity. Usually the weather forecast says 50%, which is probably relative humidity.

Air has the characteristics of absorbing moisture, and the concept of humidity is how much water vapor is contained in the air. There are three expressions: the first is absolute humidity, which means the amount of water vapor contained in the air per cubic meter, and the unit is kg/cubic meter; The second is moisture content, which means the amount of water vapor per kilogram of dry air, and the unit is kg/kg of dry air; The third is relative humidity, which represents the ratio of absolute humidity in the air to saturated absolute humidity at the same temperature. The number is percentage. (That is to say, the amount of water vapor contained in the air in a certain place accounts for the percentage of saturated water vapor at that temperature in a certain time. Relative humidity is expressed in RH. Relative humidity is defined as the percentage of the actual water vapor density (expressed by d 1) in air per unit volume to the saturated water vapor density (expressed by d2) at the same temperature, that is, RH (%) = d1/d2x100%; Another calculation method is: the percentage of actual air vapor pressure (expressed by p 1) and saturated vapor pressure (expressed by p2) at the same temperature, that is, RH(%)= p 1/ p2 x 100%.