[gradsusr] Moisture Convergence Data

[Mohsen Soltani]

Dear Abayomi,

You're right! Thank you for your nice recommendation.
Actually, I closely rechecked the script and found 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))'

As you see, dewpoint temperature is computed using "temperature+relative
humidity" in the above equation.

**************************************************************
Therefore, 4 variables are needed to display moisture convergence:
Those are:
1- relative humidity (%)
2- air temperature (K)
3- u-wind component (m/s)
4-v-wind component (m/s)
***********************************
The attached map is just as an example of "moisture convergence" over Iran.
I chose a heavy storm (rainfall) over the country to display moisture
convergence for that event. As it can be seen from the map, it clearly
shows the convergence-positive areas (light green to dark green) and
divergence-negative areas (light pink to dark rose).
In order to verify the output, I overlaid wind streams on the map for the
same time. It's in a good agreement with the convergence and divergence
regions.

****************************************************************
By the way, I also found that there is a BUG in the script!
That is:
'mconv = (-1)*hdivg(u*mixr,v*mixr)*1e4'

The minus sign (-) reverses the convergence (positive areas) with
divergence (negative areas)! What I mean is that, the  regions that should
be positive and convergence are displayed in a negative form! and vice
versa. Therefore, the (-) should be removed from the equation.
**********************************
*Now, I wonder what the unit of the moisture convergence is?  Who
knows? **Please
see the enclosed file and** let me know ...*


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


On Sun, May 26, 2013 at 9:40 AM, Abatan Abayomi <yomiabatan69 at gmail.com>wrote:

> Hey Mohsen,
>
> You don't need to look for these data again. Equation (3) above will
> compute vapor pressure for you once you have Dew point temperature,
> likewise you get mixing ratio from equation (5).
>
> Hope that help you?
>
> Abayomi
>
>
> On Sun, May 26, 2013 at 3:07 AM, Mohsen Soltani <soltani.clima at gmail.com>wrote:
>
>> Hi,
>>
>> I'm trying to display "Moisture Convergence" using the following script,
>> which written by Michael Maxwell:
>>
>> ************************************************************************
>> * 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've got all the required data to display MC, except for "vapor pressure
>> and mixing ratio". Do you possibly know where I can get those data? Would
>> you share the link(s) with me, please?
>>
>>
>> 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
>>
>>
>
>
> --
>
>
>           Trust in the Lord......
>
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