[gradsusr] A problem in calculating average relative humidity in merra

[avi kojokro]

Well I changed the lon and the lat  to 33 34 ,And the script works fine, I
got a decimal result, but it works. Attaching a screenshot of Grads.
The problem is that I must the relative humidity points I mentioned at the
beginning 32  35   Which Located within inland.
You mentioned there is a possibility to "compute RH using surface data"
.   Can you give me an example of how to do it, I am pretty new in Grads.

Avi.


2013/7/19 Mike Bosilovich <mike.bosilovich at gmail.com>

> This likely isn't a problem with grads.  Grads is returning the undef
> value. If you take a look at the region around that point, at 1000mb most
> land points are undef. This is because MERRA does not extrapolate to
> pressure levels >  Ps.
>
> http://gmao.gsfc.nasa.gov/research/merra/pressure_surface.php
>
> So, check PS to see if it is < 1000mb.  It maybe a land point. If a water
> point is OK to use in your work, move just a bit into the Meditterenean Sea
> and you should find real values. but it is possible that there may be
> undeffs over water, if the Ps becomes <1000.
>
> If you really want data at this point, you can compute RH using surface
> data, or, there is a third party routine available to perform the
> extrapolation to values under the surface.
>
>
> https://reanalyses.org/atmosphere/extrapolation-merra-reanalyses-obtain-continuous-fields
>
> If you find that this is not a grads issue, feel free to contact me
> offline, or use the merra-questions at lists.nasa.gov listserv.
>
> Mike
>
>
> On Fri, Jul 19, 2013 at 5:51 AM, avi kojokro <kojokroavi at gmail.com> wrote:
>
>> I'm trying to calculate a monthly average of relative humidity, but the
>> answer of Grads unreasonable.
>> Is the script right? I attach it.
>> I am also attaching a screenshot of Grads answer.
>>
>> The Script:
>>
>>
>> 'reinit'
>> 'c'
>> 'set display color white'
>> 'c'
>> 'sdfopen http://goldsmr3.sci.gsfc.nasa.gov:80/dods/MATMCPCLD'
>> 'set lev 1000'
>> 'set lat 32.0'
>> 'set lon 35.0'
>> yr=1979
>> tt=''
>> while(yr<=2013)
>> 'set time 1MAY'yr
>> 'q time'
>> say ' 'result
>> *'set gxout print'
>> 'd rh'
>> tt1=subwrd(result,4)
>> tt=tt' 'tt1
>> say ' 'result
>> yr=yr+1
>> endwhile
>> say 'apr (1979-2013) 850_hgt [m] : 'tt
>>
>>
>>
>>
>>
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>>
>
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