Water Vapor Calculated from Dewpoint Temperature

Calculates total precipitable atmospheric water vapor (PW) based on air temperature and relative humidity. From these two values, the the dewpoint temperature is calculated using the AWIPS formula. Dewpoint temperature is then used to calculate PW using Smith's and Reitan's equations. The latter is essentially a global average calculation, while the former uses empirically determined values for four seasons and nine latitude bands, based on atmospheric soundings.

References:

W. L. Smith. Note on the relationship between total precipitable water and surface dew point. Journal of Applied Meteorology, 5, 726-727, 1966.

C. H. Reitan. Surface dew point and water vapor aloft. Journal of Applied Meteorology, 2, 776-777, 1963.

Enter air temperature (°C):     Enter relative humidity (%):
Choose season: winter     spring     summer     fall
Choose latitude zone: 0-10     10-20     20-30     30-40     40-50     50-60     60-70     70-80     80-90

                   Dewpoint (°C):     Smith's equation (cm H2O):       Reitan's equation (cm H2O):

Continue if you want to convert overhead precipitable water vapor value to what you would observe if you are using a sun photometer water vapor instrument to measure direct sunlight along a path through the atmosphere:
Latitude (deg, + for N, - for S):     Longitude (deg, + for E, - for W):   (default coordinates for Philadelphia, PA, USA)
Date (mm/dd/yyyy): / /     Time (UT hr:min:sec): : :

Julian Date:     Earth/sun distance (AU):     Solar elevation angle (deg):
Relative air mass:
PW (cm H2O) along slant path (from Smith's equation):
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