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

Shawn R. Smith smith at coaps.fsu.edu
Fri Feb 7 07:18:13 MST 2014


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> 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
>> 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> 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
>>>> [icoads_usa-bounces at mailman.ucar.edu] on behalf of Scott Woodruff
>>>> [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>
>>>> 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]
>>>> Sent: Monday, 5 August 2013 18:23
>>>> To: Graeme Ball; Etienne Charpentier
>>>> (ECharpentier at wmo.int<mailto:ECharpentier at wmo.int>); North, Sarah
>>>> (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>); Berry,
>>>> David I. (dyb at noc.ac.uk<mailto:dyb at noc.ac.uk>);
>>>> 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]
>>>> 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>
>>>> 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>
>>>> To:     Eric Freeman
>>>> <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>, Kent,
>>>> Elizabeth C. <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.
>> _______________________________________________
>> icoads_usa mailing list
>> icoads_usa at mailman.ucar.edu
>> http://mailman.ucar.edu/mailman/listinfo/icoads_usa
> 
> ---
> Steven Worley / NCAR
> worley at ucar.edu
> rda.ucar.edu
> Wrk: 303.497.1248
> Mobile: 720.468.1961
> ----
> 
> 
> 
> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/icoads_usa/attachments/20140207/c18d428a/attachment-0001.html 


More information about the icoads_usa mailing list