Compute dew point temperature from air temperature and relative humidity using the Magnus formula.
由气温与相对湿度，按 Magnus 公式反算露点温度 Td。
| Item | Formula | Source / Standard |
|---|---|---|
| Saturation vapour pressure | es = 6.112 exp(17.62 T / (243.12 + T)) | WMO Magnus-Tetens formula |
| Dew point temperature | Td from inverted Magnus relation | WMO Magnus-Tetens formula |
| Relative humidity | RH = e / es * 100 | WMO humidity measurement guide |
Constants and standards used on this page with their authoritative sources, for verification and citation.
| Quantity | Value | Unit | Source |
|---|---|---|---|
| Magnus coefficient a | 17.625 | dimensionless | Alduchov & Eskridge (1996), J. Appl. Meteorol. 35:601-609 (revision of Bolton) |
| Magnus coefficient b | 243.04 | °C | Alduchov & Eskridge (1996) |
| Bolton coefficients a / b | 17.67 / 243.5 | °C | Bolton D. (1980), Mon. Wea. Rev. 108:1046-1053 |
| Saturation vapour pressure at 0 °C | 6.112 | hPa | Common value in Bolton (1980) / WMO CIMO Guide |
| Higher-accuracy formulations | Goff-Gratch (1946), Buck (1996), IAPWS-95 | — | Recommended in WMO CIMO Guide (WMO-No.8, Vol. I, Ch. 4) |
| Applicability | Water surface, about -40 to +50 °C; accuracy about ±0.5 °C | °C | Accepted range of the Magnus empirical form |
Note: the Magnus form is an empirical fit for water surfaces; use ice coefficients for frost point, and the WMO-recommended Goff-Gratch or Buck formulations for strict work.