in the "ω"-"t" chart, the dry bulb temperature ("t") appears as the abscissa (horizontal axis) and the humidity ratio ("ω") appear as the ordinate (vertical axis). a chart is valid for a given air pressure (or elevation above sea level). from any two independent ones of the six parameters dry bulb temperature, wet bulb temperature, relative humidity, humidity ratio, specific enthalpy, and specific volume, all the others can be determined. there are formula_6 possible combinations of independent and derived parameters.