I have radiosonde measurements of temp, relative humidity, pressure, altitude, etc.
I would like to use this data to derive the total atmospheric water vapor content for the purpose of performing atmospheric correction of remote sensing imagery.
I'm not sure I understood what you mean by "total". If you want the vertically integrated water vapour amount (kg/m2), it's quite straightforward if you make the approximation that the horizontal winds are small enough (which is obviously wrong).
If you do not have it already, You can derive the mixing ratio r = 0.622 * RH * e_sat /( P - RH * e_sat )
RH being the relative humidity. You need to calculate the saturation vapour pressure e_sat.
and then calculate the density (or volume mixing ratio) of water vapour (kg / m3)
rho_v = P/(Rd*T) * r/(1-1.608 * r)
Before doing that, you should make sure your data have been corrected for the well-known day-time dry bias of some of the most commonly used radiosondes (see e.g. Miloshevich et al., 2009, JGR)
If you want the total amount of water vapour in a box, you can estimate it by interpolating horizontally between your radiosonde data (e.g. with a Voronoi interpolation), before performing both a horizontal and vertical integration of rho_v in your box. By doing so you're likely to make quite large error due to un-resolved water vapour field heterogeneities. This could be improved by performing a proper variational analysis instead of a simple interpolation.
I hope it helps a bit.
Hi Offer,
When I'm replying to your question I read the answer of Laurent that I think is the correct answer to your question.
If you want I can provide you a matlab function that should do this job.
Guido
I think there are different methods to calculate the total atmospheric water vapor from radiosonde measurements and Laurent noticed one of them.For example see this page:http://www.eumetrain.org/data/3/359/print_2.htm
Mohammad
Here I attached the matlab function for the water vapor conversion.
It converts water vapor from:
Mass Mixing Ratio (g/Kg); Volume Mixing Ratio (ppv); Relative Umidity (%); Specific Humidity; Dew Point (K); Partial Pressure (hPa); Number Density (cm-3); Mass Density (kg/m3);
To:
Mass Mixing Ratio (g/Kg); Volume Mixing Ratio (ppv); Relative Umidity (%); Specific Humidity; Dew Point (K); Partial Pressure (hPa); Number Density (cm-3); Mass Density (kg/m3); Colummn (mm)
!!New version of the conversion routine!!
It includes optimization for Dewpoint Output
In the current version the routine solves analytically Clausius - Clapeyron law avoiding iterative approach of matlab fsolve function (used in the past version).
Hi, everyone
I found that the calculated total atmospheric water vapor using cnvrth
2o.m and formula in http://www.eumetrain.org/data/3/359/print_2.htm was different, which result is correct?
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