This is great! Thanks for producing those for me. I will investigate
these in the near future to see if they work for me when comparing to local
AWIPS version.
So one of the questions I had that didn't get answered thus far is, "Can we
choose anywhere in the model domain to plot a sounding?" We are looking to
validate locations that might not be RAOB locations, so needed to know
where it was possible to plot just for a give lat-lon point.
Thanks for any more info on that.
Bryan
On Thu, Jul 14, 2016 at 1:43 PM, Michael James <mjames@xxxxxxxx> wrote:
> I made some corrections (incl. wind barbs correctly plotted in knots) to
> the notebook and added different dewpoint-from-specific humidity
> calculations to compare, as well as verification against the AWIPS2 NSHARP
> modelsounding display.
>
> For reference:
>
> - datetime = 20160714/1200 UTC
> - source = ETAbufr
> - station = WSC
> - lat/lon = 44.13999938964844 ,-93.55999755859375
>
>
> Dewpoint is calculated three times:
>
> 1) metpy-calculated mixing ratio and vapor pressure
>
> - rmix = (s/(1-s)) *1000 * units('g/kg')
> - e = vapor_pressure(p, rmix)
> - td = dewpoint(e)
>
> 2) metpy assuming specHum = mixing ratio:
>
> - td2 = dewpoint(vapor_pressure(p, s))
>
> 3) following
> https://github.com/Unidata/awips2-ncep/blob/unidata_16.2.2/edex/gov.noaa.nws.ncep.edex.plugin.soundingrequest/src/gov/noaa/nws/ncep/edex/plugin/soundingrequest/handler/MergeSounding.java#L1783
>
> - rh = 0.263*nprs*nsh / (np.exp(17.67*ntmp/(ntmp+273.16-29.65)))
> - vaps = 6.112 * np.exp((17.67 * ntmp) / (ntmp + 243.5))
> - vapr = rh * vaps / 100
> - dwpc = np.array(243.5 * (np.log(6.112) - np.log(vapr)) /
> (np.log(vapr) - np.log(6.112) - 17.67)) * units.degC
>
> The differences between these are negligible, simply print differences and
> visually check the overlay of each on the attached notebook skewt plot and
> you can see they align well, though they are not exact (they are printed as
> columns at the end of the attached notebook).
>
> I also added an array "a2td" which contains the dewpoint values scraped
> from the AWIPS2 NSHARP "ShowText" window. Again the difference is
> negligible.
>
> But you are right that something was off in that GFSbufr 0713/1200 UTC
> plot yesterday (unfortunately our EDEX server purged those data and I'm
> unable to re-ingest since the files on both ftp.ncep.noaa.gov and
> tgftp.nws.noaa.gov seem to be formatted differently that what comes
> across the HDS NOAAport feed).
>
> In these two attached images notice the MetPy-calculated dewpoint values
> exceed temperature above 300mb, which is obviously incorrect. I haven't
> found another case like this in the 0714 soundings.
>
> Michael James
> Unidata Program Center
> Boulder, CO
>
> On Wed, Jul 13, 2016 at 5:33 PM, Bryan Guarente <guarente@xxxxxxxx> wrote:
>
>> Does this mean that we can only plot for RAOB locations or can we plot
>> for any lat lon point available in the dataset?
>>
>> I thought we could just replace that "geom = POINT (... , ...)" line with
>> an appropriate lat lon location and then "fool" it into getting the data
>> from that location instead of OAX.
>>
>> I don't believe that we could use the specific humidity for the vapor
>> pressure. The linked sounding (AWIPS 2 Cave) here is the same as you had
>> in the example posted (KOAX, July 13, 12Z).
>>
>>
>> https://drive.google.com/a/ucar.edu/file/d/0BwAYX88KH9wDSVd2dUNPWWEyckU/view?usp=sharing
>>
>> It didn't look to me like these were the same.
>>
>> Thanks for the quick response.
>>
>> Bryan
>>
>> On Wed, Jul 13, 2016 at 2:13 PM, Michael James <mjames@xxxxxxxx> wrote:
>>
>>> and online now
>>>
>>> http://python-awips.readthedocs.io/en/latest/examples/generated/Model_Sounding_Data.html
>>>
>>> Michael James
>>> Unidata Program Center
>>> Boulder, CO
>>>
>>> On Wed, Jul 13, 2016 at 2:47 PM, Ryan May <rmay@xxxxxxxx> wrote:
>>>
>>>> On Tue, Jul 12, 2016 at 11:21 AM, Bryan Guarente <guarente@xxxxxxxx>
>>>> wrote:
>>>>
>>>>> I have worked through my own version of your sounding and advanced
>>>>> sounding examples using python-awips and metpy. However, I never saw any
>>>>> ability to make a model sounding. Is there an example of making a model
>>>>> sounding with MetPy and python-awips? Initially, I think this would be
>>>>> simple, but then I realized we would be using a completely different
>>>>> filetype and thus would likely have to use a different library to decode
>>>>> it.
>>>>>
>>>>> If you have any examples, can you post them to github?
>>>>>
>>>>
>>>> Bryan,
>>>>
>>>> Michael James (cc'ed, maintainer of python-awips) came up with the
>>>> attached and had this to add:
>>>>
>>>> "I believe this is correct, assuming specific humidity is equal to
>>>> vapor pressure e (modelsounding doesn't return dewpoint). Also note that
>>>> the available locations are limited to areas around OAX due to
>>>> localization. I'll have to update this to allow global access in the next
>>>> release."
>>>>
>>>> I'm currently working on a gallery of notebooks that work across all of
>>>> the meteorology tools, and I'll add these when that's ready (I don't want
>>>> MetPy's own examples pulling from external, online data sources.)
>>>>
>>>> Ryan
>>>>
>>>> --
>>>> Ryan May, Ph.D.
>>>> Software Engineer
>>>> UCAR/Unidata
>>>> Boulder, CO
>>>>
>>>
>>>
>>
>>
>> --
>> Bryan Guarente
>> Instructional Designer/Meteorologist
>> The COMET Program
>> Boulder, CO
>>
>
>
--
Bryan Guarente
Instructional Designer/Meteorologist
The COMET Program
Boulder, CO
