[gradsusr] what is the unit of moisture convergence?

Kishore Ragi kishoreragi at gmail.com
Tue Jun 11 08:44:14 EDT 2013 

Hi Mohsen,

Thank you for the help.

Could you please send me the script of you attached .jpg file so that it
directs me to visualize my results?

Looking forwards to hearing from you.

Thank you Mohsen,

Regards,

KIshore




On Tue, Jun 11, 2013 at 11:28 AM, Mohsen Soltani <soltani.clima at gmail.com>wrote:

> Hi Kishore,
>
> Use the following script to calculate moisture convergence:
> ***********************************************************************
> ************************************************
> * rh    = Relative Humidity in %
> * t     = Temp at *set level in degrees Kelvin
> * tc    = Temp in degrees C
>  * td    = Dewpoint at *set level in degrees C
> * e     = Vapor pressure
> * mixr  = Mixing ratio
> * u     = U-wind in m/s
> * v     = V-wind in m/s
> * mconv = moisture convergence/divergence.
>
> 'tc = (t-273.16)'
> 'td = tc-((14.55+0.114*tc)*(1-0.01*rh) + pow((2.5+0.007*tc)*(1-0.01*rh),3)
> + (15.9+0.117*tc)*pow((1-0.01*rh),14))'
> 'vapr = 6.112*exp((17.67*td)/(td+243.5))'
> 'e = vapr*1.001+(lev-100)/900*0.0034'
> 'mixr = 0.62197*(e/(lev-e))*1000'
> 'mconv = (1)*hdivg(u*mixr,v*mixr)*1e4'
> 'd mconv'
> ****************************
> **************************************************
> I have to say that neither vapor pressure, mixing ratio nor even dewpoint
> temperature is needed! This is because, equation (2) computes dewpoint
> temperature:
> That is:
> 'td =
> tc-((14.55+0.114*tc)*(1-0.01*rh)+pow((2.5+0.007*tc)*(1-0.01*rh),3)+(15.9+0.117*tc)*pow((1-0.01*rh),14))'
>
> **************************
> Therefore, you only need 4 variables to calculate moisture convergence:
> Those are:
>
> 1- relative humidity (%)
> 2- air temperature (K)
> 3- u-wind component (m/s)
> 4-v-wind component (m/s)
> *************************************************
> All you have to do is to define variables based on the equations in the
> script. For example:
>
> define u = uwnd
> define v = vwnd
> define t = air
> define rh = rhum
> **********************************************************
> I'm attaching a "moisture convergence plot" over Iran. Based on the plot,
> the convergence (positive) areas shown in green color and vice versa. To
> verify my output, I overlaid wind streams. They are quite in a good
> agreement with convergence and divergence regions.
>
> BTW, that's a surface level. And as Davide suggested, the unit of the MC
> will be: (g/kg*s-1)
>
>
> Good luck,
> Mohsen
>
>
> --
> some are weather-wise some are otherwise!
> --
> Best Wishes,
> (Mr.) Mohsen Soltani
> Climatology Grad Student (M.Sc.),
> Faculty of Geography, University of Tehran, Tehran, Iran
> Tel: (+98) 9119772934
> e-mail: soltani.clima at gmail.com
>
>
> On Mon, Jun 10, 2013 at 9:59 PM, Kishore Ragi <kishoreragi at gmail.com>wrote:
>
>> Dear users,
>>
>> I can understand how to calculate moisture convergence with specific
>> humidity/mixing ratio but, I have relative humidity.
>>
>> Could anybody please help me how to calculate moisture convergence with
>> relative humidity?
>>
>> Thank you in advance,
>>
>> Sincerely,
>>
>> Kishore
>>
>>
>> On Thu, May 30, 2013 at 7:11 PM, Mohsen Soltani <soltani.clima at gmail.com>wrote:
>>
>>> Dear Davide,
>>>
>>> It sounds logical! Thank you very much for your kindness.
>>>
>>> Mohsen
>>>
>>> --
>>> some are weather-wise some are otherwise!
>>> --
>>> Best Wishes,
>>> (Mr.) Mohsen Soltani
>>> Climatology Grad Student (M.Sc.),
>>> Faculty of Geography, University of Tehran, Tehran, Iran
>>> Tel: (+98) 9119772934
>>> e-mail: soltani.clima at gmail.com
>>>
>>>
>>> On Thu, May 30, 2013 at 2:54 AM, Davide Sacchetti <
>>> davide.sacchetti at arpal.gov.it> wrote:
>>>
>>>> specific humidity is defined as ratio of water vapor mass (g) over air
>>>> mass (kg) (units: g/kg)
>>>> mixing ratio is almost the same: ratio of water vapor mass (g) over DRY
>>>> air mass (kg) (units: g/kg)
>>>>
>>>> your divergence is like d(u*mixr)/dx, then has units of (m/s * g/kg)/m:
>>>> units should be g/kg*s-1
>>>>
>>>> bye bye
>>>> Davide
>>>>
>>>> On Thu, 2013-05-30 at 01:39 -0700, Mohsen Soltani wrote:
>>>> > Dear GrADS Users,
>>>> >
>>>> >
>>>> > I employed the following script to display the moisture convergence.
>>>> > But, I don't know what is the unit of the output! Please see the
>>>> > attached plot and let me know what's your opinion.
>>>> >
>>>> >
>>>> >
>>>> ************************************************************************
>>>> > * rh    = Relative Humidity in %
>>>> > * t     = Temp at *set level in degrees Kelvin
>>>> > * tc    = Temp in degrees C
>>>> > * td    = Dewpoint at *set level in degrees C
>>>> > * e     = Vapor pressure
>>>> > * mixr  = Mixing ratio
>>>> > * u     = U-wind in m/s
>>>> > * v     = V-wind in m/s
>>>> > * mconv = moisture convergence/divergence.
>>>> >
>>>> >
>>>> > 'tc = (t-273.16)'
>>>> > 'td = tc-((14.55+0.114*tc)*(1-0.01*rh) + pow((2.5
>>>> > +0.007*tc)*(1-0.01*rh),3) + (15.9+0.117*tc)*pow((1-0.01*rh),14))'
>>>> > 'vapr = 6.112*exp((17.67*td)/(td+243.5))'
>>>> > 'e = vapr*1.001+(lev-100)/900*0.0034'
>>>> > 'mixr = 0.62197*(e/(lev-e))*1000'
>>>> > 'mconv = (1)*hdivg(u*mixr,v*mixr)*1e4'
>>>> > 'd mconv'
>>>> > ********************************************************
>>>> >
>>>> >
>>>> >
>>>> >
>>>> > Thank you,
>>>> > Mohsen
>>>> >
>>>> >
>>>> > --
>>>> > some are weather-wise some are otherwise!
>>>> > --
>>>> > Best Wishes,
>>>> > (Mr.) Mohsen Soltani
>>>> > Climatology Grad Student (M.Sc.),
>>>> > Faculty of Geography, University of Tehran, Tehran, Iran
>>>> > Tel: (+98) 9119772934
>>>> > e-mail: soltani.clima at gmail.com
>>>> >
>>>> > _______________________________________________
>>>> > gradsusr mailing list
>>>> > gradsusr at gradsusr.org
>>>> > http://gradsusr.org/mailman/listinfo/gradsusr
>>>>
>>>> --
>>>> --> Attenzione cambio indirizzo: davide.sacchetti at arpal.gov.it
>>>> --
>>>> Davide Sacchetti
>>>> Centro Funzionale Meteo Idrologico di Protezione Civile della Regione
>>>> Liguria
>>>> ARPAL Unità Tecnica Complessa di livello Regionale
>>>> V.le Brigare Partigiane 2 16121 Genova (I)
>>>> tel: +39 010 6437535                    fax: +39 010 6437520
>>>> mail: davide.sacchetti at arpal.gov.it     web: www.meteoliguria.it
>>>>
>>>>
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>>>>
>>>
>>>
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>>
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