Dry-Bulb Ambient Air Temperature (T)Thermodynamic Kinetic Temperature (Freely Exposed)
The actual physical temperature of air measured by a standard thermometer shielded from direct solar radiation and moisture. It quantifies the kinetic energy of air molecules and governs the maximum water vapor storage capacity of the atmosphere.
Default: 20.0 °C (68.0 °F, Standard Ambient Room Temperature)
Relative Humidity (RH %)Vapor Pressure Ratio (Partial-to-Saturation Percentage)
The percentage of moisture currently held in the air compared to the absolute maximum amount the air could hold at that exact temperature: RH = (e / Es) * 100%. Health organizations and ASHRAE recommend maintaining indoor levels between 30% and 60% to ease respiratory breathing, prevent dry skin, and prevent mold spores.
Default: 50.0% RH (Optimal Indoor Comfort Level)
Dew Point Temperature (Td)Isobaric Saturation Phase Boundary Temperature
The precise temperature to which air must cool at constant barometric pressure for water vapor to condense into visible liquid droplets, such as morning dew, window fog, or cloud mist. Dew point represents an absolute measure of atmospheric water content independent of ambient temperature swings.
Default: 9.3 °C (48.7 °F, Crisp and Comfortable)
Saturation Vapor Pressure (Es)Equilibrium Thermodynamic Vapor Pressure
The maximum partial pressure exerted by water vapor molecules in thermodynamic equilibrium with liquid water at temperature T. Evaluated using the Arden Buck formulation, rising exponentially from 6.11 hPa at freezing (0 °C) to 23.38 hPa at room temperature (20 °C) and 123.5 hPa in extreme heat (50 °C).
Default: 23.38 hPa / 2.338 kPa (at 20.0 °C)
Actual Partial Vapor Pressure (e)Partial Atmospheric Water Vapor Pressure
The physical barometric pressure exerted specifically by water vapor molecules in the atmosphere: e = Es(T) * (RH / 100). When ambient air cools to its dew point temperature, actual vapor pressure equals saturation vapor pressure (e = Es), initiating condensation.
Default: 11.69 hPa / 1.169 kPa (at 20.0 °C and 50% RH)
Dew Point Depression (T - Td)Saturation Deficit Temperature Margin
The numerical temperature difference between dry-bulb air temperature and dew point. A depression of 0 °C indicates 100% moisture saturation where fog, rain, or heavy dew forms immediately, while margins exceeding 15 °C characterize dry, high-evaporative arid climates where perspiration evaporates rapidly.
Default: 10.7 °C (Delta Margin to Condensation)
Vapor Pressure Deficit (VPD)Botanical & Psychrometric Evaporative Force
The drying power of the atmosphere, calculated as the difference between saturation vapor pressure inside a plant leaf (or skin surface) and ambient partial vapor pressure: VPD = Es - e. In home gardening and living spaces, a VPD between 0.8 and 1.2 kPa maintains healthy plant transpiration and respiratory comfort.
Default: 1.17 kPa (Optimal Plant & Living Comfort Zone)
Surface Condensation Margin (T_surface - Td)Substrate Dew Point Safety Margin
The temperature delta between a physical solid substrate (such as window glass, a vehicle windshield, concrete foundation, or steel beam) and the air's dew point. International industrial and building standards (ISO 8502-4) mandate keeping surfaces at least 3.0 °C (5.4 °F) above dew point to avoid moisture condensation, staining, and rust.
Default: +5.0 °C (Compliant with ISO 8502-4 Safety Standard)
Absolute Humidity (Volumetric Moisture Mass)Atmospheric Vapor Density (Mass-per-Volume)
The total physical mass of water vapor in grams contained within each cubic meter of air: AH = (216.7 * e) / (T + 273.15). Unlike relative humidity, absolute humidity remains constant when air temperature fluctuates without adding or extracting moisture.
Default: 8.65 g/m³ (Grams of Water per Cubic Meter)
