Hi Jonathan, Looks good to me! I'm happy that it's useful for your case as well as the ones I'm proposing.
Philip has suggested we switch from _at_origin to _at_start for the standard_names, arguing that it's less ambiguous. Any thoughts on that? Cheers, --Seth On Wed, 29 May 2013 11:06:28 -0400 Jonathan Wrotny <jwro...@aer.com> wrote: >Hi Seth, > >Finally getting back to you e-mail after a long weekend... > >You raise a good point about the two levels used for many of the stability >indices. You're right, it would be nice to have this information in the >definition for the these data products in case data users/modelers need it. I >think adding your two proposed standard names for the start and finish height >is a good idea. I've taken my proposed definition of lifted index and added >the sentence you suggested. Also, I added an additional sentence to discuss >the scenario where the parcel is not lifted "from the surface" but from >another pressure level. Here is my current proposal: > >Standard Name: > temperature_difference_between_ambient_air_and_air_lifted_adiabatically_from_the_surface > >Definition:This quantity is defined as the temperature difference between a >parcel of air lifted adiabatically from the surface to a given air pressure in >the troposphere and the ambient air temperature at a given air pressure in the >troposphere. It is often called the lifted index (LI) and provides a measure >of the instability of the atmosphere. The air parcel is "lifted" by moving the >air parcel from the surface to the Lifting Condensation Level (dry >adiabatically) and then from the Lifting Condensation Level to a given air >pressure (wet adiabatically). Air temperature is the bulk temperature of the >air, not the surface (skin) temperature. The term "surface" means the lower >boundary of the atmosphere. A coordinate variable of >air_pressure_of_lifted_parcel_at_finish can be specified to indicate the >specific air pressure that the temperature difference is calculated at.If the >start point of the lifted parcel is not the “surface,” then the phrase >“from_the_surface” is removed from the standard name and a coordinate variable >of air_pressure_of_lifted_parcel_at_start can be specified to indicate the >specific air pressure at which the parcel lifting starts. > >Canonical Units:K > > >And, just to include them in this e-mail, the standard names/definitions/units >for the two coordinate variables: > >Standard_names: > >air_pressure_of_lifted_parcel_at_origin >air_pressure_of_lifted_parcel_at_finish > >Definitions: > >Various stability and convective potential indices are calculated by >"lifting" a parcel of air: moving it dry adiabatically from a starting >height (often the surface) to the Lifting Condensation Level, and then >wet adiabatically from there to an ending height (often the top of >the data/model/atmosphere). air_pressure_of_lifted_parcel_at_origin >[finish] is the pressure height at the start [end] of lifting. > >Canonical units: Pa > > >I will also revise the definition of the total totals index that I recently >submitted and includes the coordinate variables in two other stability indices >that I will post this week. > >How does this look now? > >Thanks again. > >-Jonathan > >On 5/24/2013 7:17 PM, Seth McGinnis wrote: >> Hi Jonathan, >> >> I would like to suggest a small modification to your proposal for the >> lifted index (LI) standard_name. >> >> I'm working on proposals for standard_names for CAPE, CIN, LCL, and >> LFC, all of which, like LI, are based on lifting a parcel of air >> adiabatically from one height to another. >> >> The unusual thing about these variables is that they're not associated >> with a single vertical coordinate, but with two of them: the starting >> height and the ending height. So if you want to record both end >> points, you need to do it in some way that lets you distinguish them. >> >> I thought about trying to do it with cell_bounds, but that doesn't >> seem like a good fit, because these aren't fields that exists within >> the cell and are being summarized, but things that are only defined >> relative to those two endpoints. So I think a better approach is to >> use a scalar auxilliary coordinate, analogous to the way that >> forecast_reference_time is used in example 5.11 in the CF spec. >> >> >> For that, we need two new standard_names: >> >> air_pressure_of_lifted_parcel_at_origin >> air_pressure_of_lifted_parcel_at_finish >> >> Which would have the following definitions: >> >> Various stability and convective potential indices are calculated by >> "lifting" a parcel of air: moving it dry adiabatically from a starting >> height (often the surface) to the Lifting Condensation Level, and then >> wet adiabatically from there to an ending height (often the top of >> the data/model/atmosphere). air_pressure_of_lifted_parcel_at_origin >> [finish] is the pressure height at the start [end] of lifting. >> >> Both would have canonical units of Pa >> >> >> I would then like to modify the last sentence in the definition of your >> LI standard_name to say "A coordinate variable of >> air_pressure_of_lifted_parcel_at_finish can be specified to indicate >> the specific air pressure that the temperature difference is >> calculated at." >> >> >> Does that seem like a good way to handle this aspect of your LI >> variable? >> >> It would then be consistent with other lifted parcel variables (once >> they get defined), and if anyone ever wanted to calculate LI from some >> starting point other than the ground, they could just lop off the >> "_from_the_surface" suffix from the standard_name and add the starting >> coordinate. (The wikipedia article on LI talks about it being >> calculated from "the portion of the PBL that lies below the morning >> inversion", so it seems like a possibility.) >> >> Cheers, >> >> --Seth >> >> >> >> On Wed, 22 May 2013 12:40:20 -0400 >> Jonathan Wrotny <jwro...@aer.com> wrote: >>> Hi Jonathan, >>> >>> Thanks a lot for the background on the CF conventions. This helps me quite >a >>> bit to understand the ideas behind the process. >>> >>> Yes, you are right about the surface question. The GOES-R product is not >>> referenced to a standard 'surface temperature' quantity, but just the >surface, >>> in general. So, I think your proposal makes good sense. So, to summarize, >>> here the proposed standard name/definition/units for this product: >>> >>> Standard Name: >>> >>> >temperature_difference_between_ambient_air_and_air_lifted_adiabatically_from_the_surface >>> >>> Defintion: >>> >>> This quantity is defined as the temperature difference >>> between a parcel of air lifted adiabatically from the surface to a given >>> air pressure in the troposphere and the ambient air temperature at a >>> given air pressure in the troposphere. It is often called the lifted >>> index (LI) and provides a measure of the instability of the atmosphere. >>> The air parcel is "lifted" by moving the air parcel from the surface to >>> the Lifting Condensation Level (dry adiabatically) and then from the >>> Lifting Condensation Level to a given air pressure (wet adiabatically). >>> Air temperature is the bulk temperature of the air, not the surface >>> (skin) temperature. The term "surface" means the lower boundary of the >>> atmosphere. A coordinate variable of air_pressure can be specified to >>> indicate the specific air pressure that the temperature difference is >>> calculated at. >>> >>> Canonical Units: K >>> >>> Sincerely, >>> >>> Jonathan >>> >>> >>> On 5/22/2013 12:09 PM, Jonathan Gregory wrote: >>>> Dear Jonathan >>>> >>>> Thanks for your thoughts. Actually I agree with you. I would not try to >>> insist >>>> on a geophysical name in every case. It might be too contrived and it >would >>> not >>>> be helpful if there was very little chance that the generality would ever >be >>>> useful. I prefer geophysically orientated general-purpose names whenever >we >>>> can adopt them, because they are more self-explanatory and because they >>> limit >>>> the number of names we have to define. We have to be pragmatic, and the >>> result >>>> is that the standard name table reflects a mixture of approaches, some >>> general, >>>> some very specific to applications. That's life. >>>> >>>> If you really mean "the surface", not "surface air" in the meteorological >>> obs >>>> sense, perhaps it would be clearer as >>>> >>>> >>> >temperature_difference_between_ambient_air_and_air_lifted_adiabatically_from_the_surface >>>> That obviously avoids the need for a surface height coordinate. "The >>> surface" >>>> (the bottom of the atmosphere), being a named well-defined surface, does >not >>>> need a coordinate. It just has a name, and it appears in many standard >>> names. >>>> So you have a need for only one coordinate, to specify the level of the >>> ambient >>>> air. That could be a pressure coordinate or an altitude or anything you >like >>> - >>>> I think you could allow that flexibility in the definition. >>>> >>>> Best wishes >>>> >>>> Jonathan >>>> >>>> ----- Forwarded message from Jonathan Wrotny <jwro...@aer.com> ----- >>>> >>>>> Date: Wed, 22 May 2013 11:29:34 -0400 >>>>> From: Jonathan Wrotny <jwro...@aer.com> >>>>> User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130509 >>>>> Thunderbird/17.0.6 >>>>> To: Jonathan Gregory <j.m.greg...@reading.ac.uk> >>>>> CC: cf-metadata@cgd.ucar.edu >>>>> Subject: Re: [CF-metadata] new standard name: lifted_index >>>>> >>>>> Hello Jonathan, >>>>> >>>>> I still think the standard names for the stability indices are a bit >>>>> of a conundrum, but I do understand the desire to attempt to devise >>>>> a general sounding name for each product. I believe that most >>>>> physical quantities are general enough to easily fit into the CF >>>>> standard naming paradigm, i.e. attempt to phrase a name with general >>>>> atmospheric terms combined with ampersands into something that, as >>>>> you described it, is almost a description (vs. a name). To me, there >>>>> are always some very specific quantities (e.g. stability indices, >>>>> NDVI, etc.) which are by definition *not* general and are one-off >>>>> ad-hoc quantities. I could see a scenario where these types of >>>>> products are their own special category with the CF - and, thus, >>>>> have unique, non-generalized, names - while the large majority are >>>>> more general and are easily adaptable to the CF naming paradigm. My >>>>> take is that you think that this type of product delineation in the >>>>> CF is not ideal in order to have cross-discipline use and >>>>> consistency for all the standard names, and thus are suggesting to >>>>> attempt to generalize each quantity if at all possible. This seems >>>>> to work in general but can cause issues with products like the >>>>> stability indices. The confusing aspect of this approach is that >>>>> now some of the stability index products will have general sounding >>>>> names (e.g. the proposed name for the lifted index) versus the total >>>>> totals index which is too complex to generalize. I'm not sure if >>>>> this is really a problem or not for the data users/modelers, but it >>>>> is a little strange. Maybe it is the only way to handle this >>>>> somewhat unique situation. Bottom line, I'm OK with your proposed >>>>> names - the general one for the lifted index and the specific one >>>>> for the total totals index, but wanted to present some of my >>>>> thoughts as I've worked through this myself. Maybe you will have >>>>> some comments. >>>>> >>>>> Re: the surface air, question. Yes, I forgot to reply to this >>>>> question in my last reply to you. The level of the "surface air' is >>>>> not the screen height in the GOES-R product but is from the NWP >>>>> surface pressure interpolated to the time of the GOES-R product and >>>>> the horizontal spatial grid. This information is not in the >>>>> delivered product, however. But, including the pressure level that >>>>> the lifted index is calculated could occur with a coordinate >>>>> variable. It appears that the proposed definition mentions a >>>>> coordinate variable that would include this level. >>>>> >>>>> Sincerely, >>>>> >>>>> Jonathan >>>>> >>>>> >>>>> >>>>> On 5/21/2013 5:34 PM, Jonathan Gregory wrote: >>>>>> Dear Jon >>>>>> >>>>>> Thanks for considering my comments on this one >>>>>> >>>>>>> Standard Name: >>> >temperature_difference_between_ambient_air_and_surface_air_lifted_adiabatically >>>>>> I'm glad you're happy with a general name in this case. I am interested >in >>>>>> your response to Philip's question about how surface is defined here. It >>>>>> might mean "surface air" in the sense of "screen height", I suppose. In >>> the >>>>>> standard name table, we do not actually have "surface air", because we >>> expect >>>>>> the actual screen height to be explicitly given as a height coordinate >>> (1.5 m >>>>>> or whatever). If that is the case, maybe this standard name should >depend >>> on >>>>>> two vertical coordinates, and maybe it should be further generalised to >>>>>> ..._and_air_lifted_adiabatically. But that might be too general! What do >>>>>> you think? >>>>>> >>>>>> Best wishes >>>>>> >>>>>> Jonathan >>>>>> _______________________________________________ >>>>>> CF-metadata mailing list >>>>>> CF-metadata@cgd.ucar.edu >>>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>>> ----- End forwarded message ----- >>>> _______________________________________________ >>>> CF-metadata mailing list >>>> CF-metadata@cgd.ucar.edu >>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata