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where temperature T is in degrees Celsius (°C) and saturation vapor pressure P is in kilopascals (kPa). According to Monteith and Unsworth, "Values of saturation vapour pressure from Tetens' formula are within 1 Pa of exact values up to 35 °C." Murray (1967) provides Tetens' equation for temperatures below 0 °C: [3]
The Arden Buck equations are a group of empirical correlations that relate the saturation vapor pressure to temperature for moist air. The curve fits have been optimized for more accuracy than the Goff–Gratch equation in the range −80 to 50 °C (−112 to 122 °F).
The Lee–Kesler method [1] allows the estimation of the saturated vapor pressure at a given temperature for all components for which the critical pressure P c, the critical temperature T c, and the acentric factor ω are known.
e * is the saturation water vapor pressure T is the absolute air temperature in kelvins T st is the steam-point (i.e. boiling point at 1 atm.) temperature (373.15 K) e * st is e * at the steam-point pressure (1 atm = 1013.25 hPa) Similarly, the correlation for the saturation water vapor pressure over ice is:
Δ = Rate of change of saturation specific humidity with air temperature. (Pa K −1) R n = Net irradiance (MJ m −2 day −1), the external source of energy flux G = Ground heat flux (MJ m −2 day −1), usually equivalent to zero on a day T = Air temperature at 2m height (K) u 2 = Wind speed at 2m height (m −1) δe = vapor pressure ...
Δ = Rate of change of saturation specific humidity with air temperature. (Pa K −1) R n = Net irradiance (MJ m −2 day −1), the external source of energy flux G = Ground heat flux (MJ m −2 day −1), usually equivalent to zero on a day T = Air temperature at 2m (K) u 2 = Wind speed at 2m height (m/s) δe = vapor pressure deficit (kPa)
The Universal Soil Loss Equation (USLE) is a widely used mathematical model that describes soil erosion processes. [1]Erosion models play critical roles in soil and water resource conservation and nonpoint source pollution assessments, including: sediment load assessment and inventory, conservation planning and design for sediment control, and for the advancement of scientific understanding.
Values are given in terms of temperature necessary to reach the specified pressure. Valid results within the quoted ranges from most equations are included in the table for comparison. A conversion factor is included into the original first coefficients of the equations to provide the pressure in pascals (CR2: 5.006, SMI: -0.875).