[icoads_usa] Improving the humidity calculations used for ICOADS as part of R3.0?

Eric Freeman eric.freeman at noaa.gov
Fri Feb 7 07:20:17 MST 2014


Hi Shawn,
I'm using these in Java, so not much use for the Fortran community.
It will be useful to have in lmrlib as I transition to Fortan on coming 
projects.
Thanks,
Eric
On 2/7/2014 9:18 AM, Shawn R. Smith wrote:
> I also agree with using WMO 8. Has anyone converted these equations 
> into program source code to allow dewpoint calculation from various 
> input humidity types? I know Mark Bourassa has a code like this, but 
> may not be based on WMO 8 equations.
>
> Shawn
>
> On Feb 6, 2014, at 7:36 PM, Steve Worley wrote:
>
>> I agree with this approach.  Can we put this in the library and 
>> validate the
>> code easily?
>>
>> On Feb 5, 2014, at 10:45 AM, "Berry, David I." <dyb at noc.ac.uk 
>> <mailto:dyb at noc.ac.uk>> wrote:
>>
>>> Hi All,
>>>
>>> Personally, I believe that WMO 8 should be used - but with the 
>>> caveat that
>>> the equations from the body of the text should be used rather than the
>>> single page in the attachment. The body of the text gives more 
>>> information
>>> / guidance on the different methods, including on the variable
>>> psychrometric coefficient.
>>>
>>> The value of the psychrometric coefficient used should depend on the
>>> instrumentation - the different met agencies have previously determined
>>> the best ones to use with the instruments that they use - for 
>>> example the
>>> UK Met Office lists the different values used for screens and
>>> pscychrometers in their hygrometric tables. I believe other agencies do
>>> similar. Whether or not they have been updated for the current 
>>> instruments
>>> in use is another matter entirely. We also then have the issue of the
>>> e-logbooks.
>>>
>>> This 'can-o-worms' highlights the importance of reporting the wet-bulb
>>> temperature when this is the observed parameter as we can then go 
>>> back and
>>> repeat the calculation of the humidity and dew point if new 
>>> knowledge over
>>> observing methods becomes available.
>>>
>>> Dave.
>>>
>>> ---------------------------------------------------------------------------
>>> -----------------------------------------
>>> Dr. David Berry,                                Tel (direct)    +44 23
>>> 8059 7740
>>> Marine Physics and Ocean Climate (254/24),      (Group Office)  +44 23
>>> 8059 6434
>>> National Oceanography Centre,                   Fax             +44 23
>>> 8059 6400
>>> University of Southampton Waterfront Campus, dyb at noc.ac.uk 
>>> <mailto:dyb at noc.ac.uk>
>>> European Way,
>>> SOUTHAMPTON, SO14 3ZH, UK
>>> ---------------------------------------------------------------------------
>>> -----------------------------------------
>>> This e-mail (and any attachment) is confidential and intended solely for
>>> the use of the individual or entity to whom it is addressed. Both the
>>> Natural Environment Research Council  (NERC) and the University of
>>> Southampton, who share the Southampton waterfront campus and email
>>> facilities, are subject to the Freedom of Information Act 2000. The
>>> information contained in this e-mail and any reply you make may be
>>> disclosed unless it is legally exempt from disclosure. Any material
>>> supplied to the National Oceanography Centre or the University of
>>> Southampton may be stored in the electronic records management system of
>>> either party as appropriate.
>>>
>>>
>>>
>>>
>>>
>>> On 27/01/2014 21:28, "Eric Freeman" <eric.freeman at noaa.gov 
>>> <mailto:eric.freeman at noaa.gov>> wrote:
>>>
>>>> Hi Shawn,
>>>> Good point. If we are going to use anything for now it should probably
>>>> be the moisture formulae in WMO No. 8.
>>>> What's the status of TR 63? Is that pending on pyschrometric values?
>>>>
>>>> We will all have to agree on a standard for sure.
>>>>
>>>> Cheers,
>>>> Eric
>>>>
>>>>
>>>> On 1/27/2014 4:00 PM, Smith, Shawn wrote:
>>>>> Hey Scott and Eric,
>>>>>
>>>>> Although I agree that including a standard calculation of DPT in 
>>>>> ICOADS
>>>>> R3.0 may be very beneficial, I can see no good way forward without
>>>>> resolution to the JCOMM TR 63. Would be better to be tied to the JCOMM
>>>>> standard, though if properly documented, I guess the ICOADS
>>>>> international partners can agree on an algorithm and go with it.
>>>>>
>>>>> This also opens the "can o' worms" about when you calculate a missing
>>>>> dew point. Your comments below note that the current algorithm
>>>>> calculates DPT when T and WBT are available. What about when T and RH
>>>>> are all you get? Very common in the day of automated weather systems.
>>>>>
>>>>> Just something else to consider.
>>>>>
>>>>> Shawn
>>>>> ________________________________________
>>>>> From: icoads_usa-bounces at mailman.ucar.edu 
>>>>> <mailto:icoads_usa-bounces at mailman.ucar.edu>
>>>>> [icoads_usa-bounces at mailman.ucar.edu 
>>>>> <mailto:icoads_usa-bounces at mailman.ucar.edu>] on behalf of Scott 
>>>>> Woodruff
>>>>> [scott.d.woodruff at noaa.gov <mailto:scott.d.woodruff at noaa.gov>]
>>>>> Sent: Saturday, January 18, 2014 2:09 PM
>>>>> To: Eric Freeman
>>>>> Cc: Dave Berry; icoads_usa; Elizabeth Kent
>>>>> Subject: [icoads_usa] Improving the humidity calculations used for
>>>>> ICOADS as    part of R3.0?
>>>>>
>>>>> Eric,
>>>>>
>>>>> Thanks for your e-mail, and sorry it took so long to respond. I agree
>>>>> with Liz' comments about considering the possibility of a review 
>>>>> of the
>>>>> ICOADS humidity calculations as part of R3, to ensure that recommended
>>>>> practice is being used--or at minimum to make our documentation more
>>>>> clear and accessible on what is being done.
>>>>>
>>>>> As part of the dupelim processing (i.e. under Field preconditioning
>>>>> modifications) we have had a fairly simple algorithm in place for 
>>>>> a long
>>>>> time to calculate missing DPT. See PS. I think this was suggested by
>>>>> NCAR way back during COADS Release 1 days as a computationally 
>>>>> efficient
>>>>> method.
>>>>>
>>>>> Whether we have had any other individual data translations to IMMA
>>>>> where missing DPT was computed (i.e. by the ICOADS project) would have
>>>>> to be looked into. But I think we have generally avoided that 
>>>>> approach,
>>>>> at least for Boulder-based translations, so the computation could be
>>>>> done with more consistency at the dupelim level.
>>>>>
>>>>> Back in 2011, I was discussing with Henry Kleta (Chair JCOMM SOT
>>>>> TT-Instrument Standards) the desirability of better harmonizing key
>>>>> ICOADS computations (e.g. PS) with JCOMM best practices, including the
>>>>> feasibility of comprehensive numerical comparisons against 
>>>>> international
>>>>> methods (e.g. http://www.indigo2.de/download/dewpoint.pro).
>>>>>
>>>>> While ICOADS NOAA/ESRL funding problems starting in late 2011 
>>>>> suspended
>>>>> that idea for a long while, I'm thinking we should probably revisit it
>>>>> in conjunction with the R3.0 work. We (including Dave, Liz, & Shawn;
>>>>> also members of TT-IS) also participated in the drafting of a still
>>>>> pending JCOMM TR (Recommended Algorithms for the Computation of Marine
>>>>> Meteorological Variables; if interested see attached draft 
>>>>> version), but
>>>>> publication unfortunately may still be hung up on resolving some
>>>>> international disagreements on the fine details of the algorithms (see
>>>>> PPS).
>>>>>
>>>>> Developing further/better DPT/humidity calculation routines, e.g. to
>>>>> share with partners (plus ETMC, etc.), also sounds to me like a good
>>>>> idea. We'd have to think more about whether {lmrlib} would be the best
>>>>> place for those though, or whether this might be another good area for
>>>>> initiating GitHub-type collaboration (e.g. IMMA tools as recently
>>>>> provided by Philip Brohan: https://github.com/oldweather/IMMA).
>>>>>
>>>>> Maybe others will have comments regarding the way forward from 
>>>>> here for
>>>>> ICOADS, but I think a sticking point may be the still unresolved 
>>>>> status
>>>>> of JCOMM TR 63 and its coded algorithms (which we TT-IS folks 
>>>>> might want
>>>>> to check on, and see if an interested  nudge might be helpful). -Scott
>>>>>
>>>>> PS: From http://icoads.noaa.gov/e-doc/other/dupelim_1784 (or it 
>>>>> appears
>>>>> identically in other dupelim e-docs):
>>>>>        e) Compute a missing dew point temperature if WBT and AT are
>>>>> extant; if
>>>>>        SLP is missing 1015.0 is used as SLP.  This rule is not applied
>>>>> if any
>>>>>        of the data used for computation of DPT (i.e., SLP, AT, WBT, or
>>>>> T2) are
>>>>>        in the error attachment, or if WBT is greater than AT.
>>>>> Constants ACON
>>>>>        and BCON are set for computation of DPT relative to water:
>>>>> ACON=7.5
>>>>>        and BCON=237.3.  The following Fortran code is then used to
>>>>> attempt
>>>>>        computation of DPT [NOTE: this computation actually occurs as a
>>>>> final
>>>>>        step in field modifications, since AT and WBT values may be
>>>>> modified by
>>>>>        rules given below that are applied to individual decks]:
>>>>>             ESW = 6.1078*10.**(WBT*ACON/(WBT+BCON))
>>>>>             E = ESW-(.00066*SLP)*(((.00115*WBT)+1)*(AT-WBT))
>>>>>             IF(E.LT.0.) RETURN
>>>>>             CCON = ALOG10(E/6.1078)
>>>>>             DPT = BCON*CCON/(ACON-CCON)
>>>>>        where the RETURN if vapor pressure (E) is less than zero leads
>>>>> to an
>>>>>        error diagnostic, and otherwise the resulting DPT is rounded to
>>>>> the
>>>>>        nearest 0.1 at C.  To indicate that this calculation has taken
>>>>> place
>>>>>        during preconditioning, T2 is set to 3, 4, 5, or 6, simply
>>>>> depending on
>>>>>        whether the previous value of T2 was missing, 0, 1, or 2.
>>>>>
>>>>> PPS: Regarding status of JCOMM TR 63:
>>>>> On 8/5/13 5:38 PM, Graeme Ball wrote:
>>>>>
>>>>> Henry et al
>>>>>
>>>>> Perhaps clarification should be sought from CIMO.
>>>>>
>>>>> regards,
>>>>> Graeme
>>>>>
>>>>> Graeme Ball | Manager, Marine Operations Group
>>>>>      Chair, JCOMM Ship Observations Team (SOT)
>>>>>      Chair, International Buoy Programme for the Indian Ocean (IBPIO)
>>>>>
>>>>> Bureau of Meteorology
>>>>> GPO Box 1289 Melbourne, VIC 3001, Australia
>>>>> Level 7, 700 Collins Street, Docklands, VIC 3008, Australia
>>>>> Tel: +61 3 9669 4203 | Fax: +61 3 9669 4168 |
>>>>> g.ball at bom.gov.au <mailto:g.ball at bom.gov.au><mailto:g.ball at bom.gov.au>
>>>>> www.bom.gov.au <http://www.bom.gov.au/><http://www.bom.gov.au 
>>>>> <http://www.bom.gov.au/>>
>>>>> Disclaimer: This email is sent by the Bureau of Meteorology (ABN 
>>>>> 92 637
>>>>> 533 532). The information in this email message may contain 
>>>>> confidential
>>>>> or legally privileged information. If you are not the intended 
>>>>> recipient
>>>>> and have received this email message in error, please delete all 
>>>>> copies
>>>>> and attachments and notify the Bureau immediately.
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: Kleta Henry [mailto:Henry.Kleta at dwd.de <http://dwd.de/>]
>>>>> Sent: Monday, 5 August 2013 18:23
>>>>> To: Graeme Ball; Etienne Charpentier
>>>>> (ECharpentier at wmo.int 
>>>>> <mailto:ECharpentier at wmo.int><mailto:ECharpentier at wmo.int>); 
>>>>> North, Sarah
>>>>> (sarah.north at metoffice.gov.uk 
>>>>> <mailto:sarah.north at metoffice.gov.uk><mailto:sarah.north at metoffice.gov.uk>);
>>>>> Rosenhagen Gudrun
>>>>> (Gudrun.Rosenhagen at dwd.de 
>>>>> <mailto:Gudrun.Rosenhagen at dwd.de><mailto:Gudrun.Rosenhagen at dwd.de>); 
>>>>> Berry,
>>>>> David I. (dyb at noc.ac.uk <mailto:dyb at noc.ac.uk><mailto:dyb at noc.ac.uk>);
>>>>> scott.d.woodruff at noaa.gov 
>>>>> <mailto:scott.d.woodruff at noaa.gov><mailto:scott.d.woodruff at noaa.gov>
>>>>> Subject: Request for guidance on dewpoint algorithm to be recommend
>>>>>
>>>>> Dear all,
>>>>>
>>>>> I am currently discussing a lot with the japanese colleagues 
>>>>> concerning
>>>>> the dewpoint algorithm to be recommended in the JCOMM TR 63.
>>>>>
>>>>> I have enclosed the discussion for you as input.
>>>>>
>>>>> Furthermore I have enclose the two proposed algortithms.
>>>>>
>>>>>
>>>>> In short:
>>>>>
>>>>> After some discussions concerning the dewpoint / frostpoint issue, I
>>>>> opted to delete the frostpoint bit from the algorithm, and only 
>>>>> use the
>>>>> dewpoint part.
>>>>>
>>>>> Reasons for that:
>>>>>
>>>>> Following WMO 8, Part I, Annex 4.B the dewpoint formulas are valid for
>>>>> the temperature range of -45°C to 60°C.
>>>>> The frostpoint formulas are valid for the range of -65°C to 0°C. Those
>>>>> ranges are different and in my opinion therefore can't be mixed.
>>>>> The PMOs I asked confirmed that the observer shall use the 
>>>>> psychrometer
>>>>> as long as it takes for the ice on the wet-bulb thermometer to 
>>>>> dissolve.
>>>>> Therefore there is no ice, therefore the dewpoint formulas have to be
>>>>> used.
>>>>> Gudrun checked the GCC data and found no frostpoint data.
>>>>>
>>>>>
>>>>> The japanese colleagues use another interpretation:
>>>>>
>>>>> In all cases the dewpoint shall be reported.
>>>>> When there is ice, the dewpoint shall be calculated with vapour
>>>>> pressures with regard to ice, but with the dewpoint, and not the
>>>>> frostpoint formula.
>>>>>
>>>>>
>>>>> Currently I see no quick way to solve this diffenrent interpretations.
>>>>> One way would be that someone accepted as "standard" gives guidance or
>>>>> someone shows a good compromise.
>>>>>
>>>>>
>>>>> I should be grateful for any guidance on this one.
>>>>> Maybe there is a clear recommendation within WMO?
>>>>> Or some scientific paper covering this topic?
>>>>>
>>>>>
>>>>> Thanks in advance and best regards,
>>>>>
>>>>> Henry
>>>>>
>>>>> --
>>>>> Deutscher Wetterdienst (DWD)
>>>>> TI 33, Maritimes Messnetz
>>>>> Frahmredder 95
>>>>> D-22393 Hamburg
>>>>> Tel: +49(69)8062-6635
>>>>> Fax: +49(69)8062-6699
>>>>>
>>>>>
>>>>> -----Ursprüngliche Nachricht-----
>>>>> Von: Tomoko Sakama [mailto:mcss at climar.kishou.go.jp 
>>>>> <http://climar.kishou.go.jp/>]
>>>>> Gesendet: Montag, 5. August 2013 08:42
>>>>> An: Kleta Henry
>>>>> Cc: vos-office;
>>>>> mcss at climar.kishou.go.jp 
>>>>> <mailto:mcss at climar.kishou.go.jp><mailto:mcss at climar.kishou.go.jp>
>>>>> Betreff: Re: AW: AW: AW: AW: AW: [SOT TT-IS] JCOMM TR 63, request for
>>>>> comments [SEC=UNCLASSIFIED]
>>>>>
>>>>> Dear Henry,
>>>>>
>>>>> Thank you for your reply.
>>>>> We cannot agree to current algorithm because it does not give the
>>>>> calculation of the dewpoint temperature when the wet-bulb 
>>>>> thermometer is
>>>>> iced.
>>>>> We should calculate and report the dewpoint temperature (Manual on
>>>>> Codes WMO no.306).
>>>>> Frostpoint temperature is not equal to dewpoint temperature when the
>>>>> wet-bulb thermometer is iced. So we should calculate the dewpoint
>>>>> temperature even when the wet-bulb thermometer is iced.
>>>>>
>>>>> We believe that the saturation vapour pressure with regard to ice
>>>>> should be used when the wet bulb is iced, and the dewpoint temperature
>>>>> should be calculated with the saturation vapour pressure with 
>>>>> regard to
>>>>> ice. This is clear from the WMO no.8 Part I, Annex 4.B, and I intended
>>>>> to add this point to the proposed algorithm for calculating dewpoint.
>>>>>
>>>>> For example, t = -3.0 degree C, t_wet = -5.0 degree C, P = 1013.25 hPa
>>>>> and iced.
>>>>> Td = -10.056 degree C
>>>>> Tf = -8.926 degree C
>>>>> We should report the Td = -10.0 degree C in the weather report and
>>>>> marine logbook.
>>>>>
>>>>>
>>>>> Best regards,
>>>>>
>>>>> Tomoko Sakama,
>>>>> Japan Meteorological Agency
>>>>>
>>>>> [...]
>>>>>
>>>>>
>>>>>
>>>>> _________________________________________________________________________
>>>>> ____
>>>>> On 12/23/13 7:08 AM, Eric Freeman wrote:
>>>>> Hi Scott,
>>>>> I've been discussing with our colleagues at NOC the Fram data set and
>>>>> calculating wet bulb temps from available fields.
>>>>> Liz has mentioned that this is likely not a good idea adding these to
>>>>> ICOADS, but we should rather look into calculating the dwpt. I'm 
>>>>> working
>>>>> with them on that, but Liz has also mentioned a lack of
>>>>> procedures/equations for calculating moisture variables in ICOADS 
>>>>> (e.g.
>>>>> lmrlib.f).
>>>>>
>>>>> Maybe we can look into this and possible providing some standardized
>>>>> equations to use. I know that changes to lmrlib.f would likely require
>>>>> larger changes elsewhere and may not be feasible immediately, but
>>>>> possibly worth considering for R3.0, even as a separate library from
>>>>> lmrlib (although having them all together in one place is nice).
>>>>>
>>>>> Thanks,
>>>>> Eric
>>>>>
>>>>>
>>>>> -------- Original Message --------
>>>>> Subject:        Re: wet bulb calculations
>>>>> Date:   Mon, 23 Dec 2013 13:28:41 +0000
>>>>> From:   Kent, Elizabeth C. <eck at noc.ac.uk 
>>>>> <mailto:eck at noc.ac.uk>><mailto:eck at noc.ac.uk>
>>>>> To:     Eric Freeman
>>>>> <eric.freeman at noaa.gov 
>>>>> <mailto:eric.freeman at noaa.gov>><mailto:eric.freeman at noaa.gov>
>>>>> CC:     Berry, David I. <dyb at noc.ac.uk 
>>>>> <mailto:dyb at noc.ac.uk>><mailto:dyb at noc.ac.uk>, Kent,
>>>>> Elizabeth C. <eck at noc.ac.uk 
>>>>> <mailto:eck at noc.ac.uk>><mailto:eck at noc.ac.uk>
>>>>>
>>>>>
>>>>>
>>>>> Hello again,
>>>>>
>>>>> I imagine that most of the equations that we've been exchanging 
>>>>> will be
>>>>> OK for testing purposes, however its important that whatever you 
>>>>> use to
>>>>> calculate any new parameters is consistent with ICOADS practice. I 
>>>>> had a
>>>>> look around the ICOADS website and found this:
>>>>>
>>>>> http://icoads.noaa.gov/software/other/profs_short
>>>>>
>>>>> Which is a subset of the code here:
>>>>> http://icoads.noaa.gov/software/other/profs
>>>>>
>>>>> The link that I followed to get to this was for Release 1, I couldn't
>>>>> find anything more modern.
>>>>>
>>>>> http://icoads.noaa.gov/Release_1/suppA.html
>>>>>
>>>>> Also at a higher level in the ICOADS software directory I found this
>>>>> which also does some humidity conversion:
>>>>>
>>>>> http://icoads.noaa.gov/software/qctrf.f
>>>>>
>>>>> I think you should talk to Scott on his return to work next year to
>>>>> find out exactly how the ICOADS humidity processing has been carried
>>>>> out. profs_short doesn't seem to include any ice bulb calculations but
>>>>> profs does. I'm not sure whether a review of humidity calculation is
>>>>> planned as part of release 3, but it would be good to try to 
>>>>> ensure that
>>>>> recommended practice is being used, especially as we are now hoping to
>>>>> include RH. Whether or not changes to the processing methodology are
>>>>> required or possible (in the R3.0 timeframe), it seems that the
>>>>> information on what was done could be a bit more accessible.
>>>>>
>>>>> I'll be back in the office on the 6th January,
>>>>>
>>>>> Happy Christmas,
>>>>>
>>>>> Liz
>>>>>
>>>>>
>>>>>
>>>>> From: Eric Freeman 
>>>>> <Eric.Freeman at noaa.gov<mailto:Eric.Freeman at noaa.gov>>
>>>>> Date: Monday, 23 December 2013 11:55
>>>>> To: "Berry, David I." <dyb at noc.ac.uk<mailto:dyb at noc.ac.uk>>, Elizabeth
>>>>> Kent <eck at noc.ac.uk<mailto:eck at noc.ac.uk>>
>>>>> Subject: Re: wet bulb calculations
>>>>>
>>>>> Hi Dave,
>>>>> Thanks for following up on this. Let me play around with it and I'll
>>>>> let you know if I have any questions (likely  ;-) ).
>>>>> Cheers,
>>>>> Eric
>>>>> On 12/23/2013 5:30 AM, Berry, David I. wrote:
>>>>> Hi Eric,
>>>>>
>>>>> One last thought crossed my mind ­ WMO No 8 contains the formulae you
>>>>> want ­ I've attached the relevant page. You should be able to back out
>>>>> the dew point and frost point temperatures from the vapour pressure.
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Dave.
>>>>>
>>>>> -------------------------------------------------------------------------
>>>>> -------------------------------------------
>>>>> Dr. David Berry,                                Tel (direct)    +44 23
>>>>> 8059 7740
>>>>> Marine Physics and Ocean Climate (254/24),      (Group Office)  +44 23
>>>>> 8059 6434
>>>>> National Oceanography Centre,                   Fax             +44 23
>>>>> 8059 6400
>>>>> University of Southampton Waterfront Campus,
>>>>> dyb at noc.ac.uk<mailto:dyb at noc.ac.uk>
>>>>> European Way,
>>>>> SOUTHAMPTON, SO14 3ZH, UK
>>>>>
>>>>> -------------------------------------------------------------------------
>>>>> -------------------------------------------
>>>>> This e-mail (and any attachment) is confidential and intended solely
>>>>> for the use of the individual or entity to whom it is addressed. Both
>>>>> the Natural Environment Research Council  (NERC) and the University of
>>>>> Southampton, who share the Southampton waterfront campus and email
>>>>> facilities, are subject to the Freedom of Information Act 2000. The
>>>>> information contained in this e-mail and any reply you make may be
>>>>> disclosed unless it is legally exempt from disclosure. Any material
>>>>> supplied to the National Oceanography Centre or the University of
>>>>> Southampton may be stored in the electronic records management 
>>>>> system of
>>>>> either party as appropriate.
>>>>>
>>>>> From: <Kent>, "Elizabeth C." <eck at noc.ac.uk<mailto:eck at noc.ac.uk>>
>>>>> Date: Friday, 20 December 2013 17:53
>>>>> To: Eric Freeman <eric.freeman at noaa.gov<mailto:eric.freeman at noaa.gov>>
>>>>> Cc: David Berry <dyb at noc.ac.uk<mailto:dyb at noc.ac.uk>>
>>>>> Subject: Re: wet bulb calculations
>>>>>
>>>>>
>>>>> At risk of crossing again I don't know anything really about ice bulbs
>>>>> - but we should be able to help out with that (but not now ... I'm off
>>>>> home).
>>>>>
>>>>> I have a copy of the Met Office hygrometric tables which has 
>>>>> values for
>>>>> dry bulbs below zero, so we should be able to do something with 
>>>>> those at
>>>>> the very least.
>>>>>
>>>>> I'm in on Monday, but last from me for a bit ... Liz
>>>>>
>>>>> From: Eric Freeman 
>>>>> <Eric.Freeman at noaa.gov<mailto:Eric.Freeman at noaa.gov>>
>>>>> Date: Friday, 20 December 2013 17:40
>>>>> To: Elizabeth Kent <eck at noc.ac.uk<mailto:eck at noc.ac.uk>>
>>>>> Cc: "Berry, David I." <dyb at noc.ac.uk<mailto:dyb at noc.ac.uk>>
>>>>> Subject: Re: wet bulb calculations
>>>>>
>>>>> Hi Liz,
>>>>> Thanks for looking into that. Since RH is already reported, I'm 
>>>>> putting
>>>>> that into the Immt attm.
>>>>> I will stay clear of the wet bulb and work on dwpt.
>>>>>
>>>>> If I can get the vp values, can you give me some guidance on adjusting
>>>>> for ice bulb?
>>>>> Cheers,
>>>>> Eric
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On 12/20/2013 12:30 PM, Kent, Elizabeth C. wrote:
>>>>>
>>>>> OK,
>>>>>
>>>>> Looking at the first spreadsheet (sea_1900) and taking the first
>>>>> positive air temperature we have:
>>>>>
>>>>> AT = 0.5 degC, RH = 90%, mm = 4.3
>>>>>
>>>>> Using the NOAA calculator:
>>>>> http://www.srh.noaa.gov/epz/?n=wxcalc_vaporpressure
>>>>>
>>>>> and entering 0.5 in the temperature field you get an svp of 4.75 mmHg.
>>>>> if you multiply that by 0.9 you get 4.3. So that makes sense at least,
>>>>> if I've got the columns right and understood things properly.
>>>>>
>>>>> Personally I don't think that calculated wetbulbs should go into
>>>>> ICOADS. If anything is calculated it should be Dewpoint or RH.
>>>>>
>>>>> As I said in my previous email I'd attack the +ve values first then
>>>>> worry about ice-bulb adjustments after that.
>>>>>
>>>>> Hope this helps,
>>>>>
>>>>> Liz
>>>>>
>>>>> From: Eric Freeman 
>>>>> <Eric.Freeman at noaa.gov<mailto:Eric.Freeman at noaa.gov>>
>>>>> Date: Friday, 20 December 2013 16:58
>>>>> To: "Berry, David I." <dyb at noc.ac.uk<mailto:dyb at noc.ac.uk>>
>>>>> Cc: Elizabeth Kent <eck at noc.ac.uk<mailto:eck at noc.ac.uk>>
>>>>> Subject: Re: wet bulb calculations
>>>>>
>>>>> Hi Dave (and Liz),
>>>>> I agree. Something is different, and I'm having trouble 
>>>>> identifying it.
>>>>> Adding the pressure into the equation gives me values much 
>>>>> different, so
>>>>> I think the observer used a formula closer to E = e - A(T-t).
>>>>>
>>>>> Attached are a few files (spreadsheets) that contain the vapor 
>>>>> pressure
>>>>> values in column K, plus the other fields mentioned. Some have better
>>>>> descriptive headers than others.
>>>>> For converting to IMMA1, I only have the wet bulb (if possible to
>>>>> backwards engineer) and converting date/time to UTC. Getting there!
>>>>> Cheers,
>>>>> Eric
>>>>>
>>>>>
>>>>> On 12/20/2013 11:46 AM, Berry, David I. wrote:
>>>>> Hi Eric
>>>>>
>>>>> One of vapour pressure, relative humidity or air temperature has to be
>>>>> wrong ­ or a formula that I'm not familiar with used to calculate 
>>>>> one of
>>>>> the quantities.
>>>>>
>>>>> I'm not familiar with with the Jelinek's tables or Ekholm's rules so
>>>>> I'm afraid I can't help you there. Liz (cc'd) may be able to help.
>>>>>
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Dave.
>>>>>
>>>>> -------------------------------------------------------------------------
>>>>> -------------------------------------------
>>>>> Dr. David Berry,                                Tel (direct)    +44 23
>>>>> 8059 7740
>>>>> Marine Physics and Ocean Climate (254/24),      (Group Office)  +44 23
>>>>> 8059 6434
>>>>> National Oceanography Centre,                   Fax             +44 23
>>>>> 8059 6400
>>>>> University of Southampton Waterfront Campus,
>>>>> dyb at noc.ac.uk<mailto:dyb at noc.ac.uk>
>>>>> European Way,
>>>>> SOUTHAMPTON, SO14 3ZH, UK
>>>>>
>>>>> -------------------------------------------------------------------------
>>>>> -------------------------------------------
>>>>> This e-mail (and any attachment) is confidential and intended solely
>>>>> for the use of the individual or entity to whom it is addressed. Both
>>>>> the Natural Environment Research Council  (NERC) and the University of
>>>>> Southampton, who share the Southampton waterfront campus and email
>>>>> facilities, are subject to the Freedom of Information Act 2000. The
>>>>> information contained in this e-mail and any reply you make may be
>>>>> disclosed unless it is legally exempt from disclosure. Any material
>>>>> supplied to the National Oceanography Centre or the University of
>>>>> Southampton may be stored in the electronic records management 
>>>>> system of
>>>>> either party as appropriate.
>>>>>
>>>>> From: Eric Freeman 
>>>>> <eric.freeman at noaa.gov<mailto:eric.freeman at noaa.gov>>
>>>>> Date: Friday, 20 December 2013 16:16
>>>>> To: David Berry <dyb at noc.ac.uk<mailto:dyb at noc.ac.uk>>
>>>>> Subject: Re: wet bulb calculations
>>>>>
>>>>> Hi Dave,
>>>>> Thanks for taking a look at this. If possible I want to salvage this
>>>>> info for the IMMA1 record, but I want to verify that I do it 
>>>>> correctly.
>>>>> However, if the AT or vapor pressure is incorrect that will cause me
>>>>> problems immediately and won't be able to reproduce without some 
>>>>> sort of
>>>>> correction. I'm not sure that I will be able to do that for this
>>>>> translation or it might fall more in the IVAD category.
>>>>>
>>>>> Thanks for letting me know about the pressure in the psychr. eq. That
>>>>> should help me out. I'll play around with it a bit more this 
>>>>> afternoon.
>>>>>
>>>>> I was able to dig some key information up on the moisture calculations
>>>>> that may help further. If familiar maybe you can point me to them:
>>>>> [cid:part1.03050502.08080509 at noaa.gov]
>>>>>
>>>>>
>>>>> I'm trying to find a good copy of Jelinek's tables. I've only been 
>>>>> able
>>>>> to use online copies and it hasn't worked out well, not to mention 
>>>>> that
>>>>> it's also in German! I have to use Google translator since I don't 
>>>>> know
>>>>> a bit of German! ;-)
>>>>>
>>>>> Thanks again for your help.
>>>>> Taking any time for the holidays?
>>>>> Cheers,
>>>>> Eric
>>>>>
>>>>>
>>>>> On 12/20/2013 10:50 AM, Berry, David I. wrote:
>>>>> Hey Eric,
>>>>>
>>>>> I've just been trying to puzzle out those numbers.
>>>>>
>>>>> Based on the RH = 100% the vapour pressure (5.866mb) should be 
>>>>> equal to
>>>>> the saturation vapour pressure at the dry bulb temperature (5.975 mb).
>>>>> This is not the case so there's an inconsistency in the values as
>>>>> reported ­ either the air temperature is wrong or the vapour 
>>>>> pressure is
>>>>> wrong ­ this is assuming that the vapour tension is measured in mm of
>>>>> mercury (I'm not familiar with the measurement).
>>>>>
>>>>> A is the psychrometric coefficient and should depend on the type of
>>>>> instrument being used and the whether the wet bulb is iced or not.
>>>>>
>>>>> If you could send me other examples I'll see if I can figure out what
>>>>> is going on. Also should the equation for vapour pressure be
>>>>>
>>>>> E = e ­ Ap(T-t)
>>>>>
>>>>> I.e. The pressure is used in the psychrometric equation.
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Dave.
>>>>>
>>>>> -------------------------------------------------------------------------
>>>>> -------------------------------------------
>>>>> Dr. David Berry,                                Tel (direct)    +44 23
>>>>> 8059 7740
>>>>> Marine Physics and Ocean Climate (254/24),      (Group Office)  +44 23
>>>>> 8059 6434
>>>>> National Oceanography Centre,                   Fax             +44 23
>>>>> 8059 6400
>>>>> University of Southampton Waterfront Campus,
>>>>> dyb at noc.ac.uk<mailto:dyb at noc.ac.uk>
>>>>> European Way,
>>>>> SOUTHAMPTON, SO14 3ZH, UK
>>>>>
>>>>> -------------------------------------------------------------------------
>>>>> -------------------------------------------
>>>>> This e-mail (and any attachment) is confidential and intended solely
>>>>> for the use of the individual or entity to whom it is addressed. Both
>>>>> the Natural Environment Research Council  (NERC) and the University of
>>>>> Southampton, who share the Southampton waterfront campus and email
>>>>> facilities, are subject to the Freedom of Information Act 2000. The
>>>>> information contained in this e-mail and any reply you make may be
>>>>> disclosed unless it is legally exempt from disclosure. Any material
>>>>> supplied to the National Oceanography Centre or the University of
>>>>> Southampton may be stored in the electronic records management 
>>>>> system of
>>>>> either party as appropriate.
>>>>>
>>>>> From: Eric Freeman 
>>>>> <eric.freeman at noaa.gov<mailto:eric.freeman at noaa.gov>>
>>>>> Date: Friday, 20 December 2013 15:02
>>>>> To: David Berry <dyb at noc.ac.uk<mailto:dyb at noc.ac.uk>>
>>>>> Subject: Re: wet bulb calculations
>>>>>
>>>>> Hi Dave,
>>>>> I was able to locate some information in the publication that may be
>>>>> useful. It's the standard equation for vapor pressure that I can 
>>>>> use to
>>>>> solve for wet bulb.
>>>>>
>>>>> Supposedly the equation used was: E = e - A(T-t) where
>>>>> E = Vapor pressure (or 'tension' as the observer reported) (mb)
>>>>> e = Sat. Vapor pressure (mb) Not available
>>>>> A = .8 (constant used ?)
>>>>> T = dry bulb (c)
>>>>> t = wet bulb (c) Not available
>>>>>
>>>>>
>>>>> I've been able to solve for e using e = E0 x 10^(7.5T / 237.7+T), and
>>>>> then solve for t.
>>>>> Thing is, the observer must have been doing something  a bit different
>>>>> as I can come close to the humidity values reported by the 
>>>>> observer, but
>>>>> off 2-3+%.
>>>>>
>>>>> Here's a sample from one of his reports, his values, and then my
>>>>> calculation:
>>>>> Observer:
>>>>> E=4.4mm=5.866mb
>>>>> A= Not provided, but found something that says .8 may have been used
>>>>> for a constant, but I've also seen multiple values for 0<T>0 and also
>>>>> according to calm, light, or high wind speeds. I can solve for this
>>>>> separately, but haven't.
>>>>> T = -0.3C
>>>>> Relative Humidity = 100%
>>>>> pressure = 750.7mm = 1000.85mb
>>>>>
>>>>> When I use the constants A=.8  and E0=6.11, I come up with e = 5.97mb,
>>>>> Tw= -0.4375, and RH = ~97%.
>>>>> This doesn't agree, so I'm worried about producing wet bulb temps that
>>>>> are obviously incorrect. The observer must have done something I can't
>>>>> figure out.
>>>>>
>>>>> Any advice you can give would be greatly appreciated.
>>>>> Cheers,
>>>>> Eric
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On 12/19/2013 12:45 PM, Eric Freeman wrote:
>>>>> Hi Dave,
>>>>> Hope all is well!
>>>>>
>>>>> I'm working on translating the Fram data set for ICOADS for years
>>>>> 1898-1902 and I'm wondering if it's possible to calculate the wet bulb
>>>>> temp using any of the following available fields:
>>>>> dry bulb (celsius)
>>>>> relative humidity (percent)
>>>>> slp (probably not useful unless the elevation was disclosed, but it's
>>>>> not; values corrected to sea level)
>>>>> vapor tension (mm)
>>>>>
>>>>> Let me know your opinion and if there is a way to use dry bulb, RH and
>>>>> vapor tension to calculate wet bulb.
>>>>> Thanks!
>>>>> Eric
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> ===========================================
>>>>> Eric Freeman
>>>>> Marine Observation Analyst
>>>>> Team STG, Inc./ERT - Government Contractor
>>>>>
>>>>> Ingest and Analysis Branch
>>>>> Global Climate Applications Division
>>>>> NOAA's National Climatic Data Center
>>>>> 151 Patton Avenue, Asheville, NC 28801-5001
>>>>> Phone: +1 828.271.4463
>>>>> Fax:   +1 828.271.4022
>>>>> Eric.Freeman at noaa.gov<mailto:Eric.Freeman at noaa.gov>
>>>>> ===========================================
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>>
>>> This message (and any attachments) is for the recipient only. NERC 
>>> is subject to the Freedom of Information Act 2000 and the contents 
>>> of this email and any reply you make may be disclosed by NERC unless 
>>> it is exempt from release under the Act. Any material supplied to 
>>> NERC may be stored in an electronic records management system.
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>>
>> ---
>> Steven Worley / NCAR
>> worley at ucar.edu <mailto:worley at ucar.edu>
>> rda.ucar.edu <http://rda.ucar.edu/>
>> Wrk: 303.497.1248
>> Mobile: 720.468.1961
>> ----
>>
>>
>>
>>
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