I wrote a small paper where such data were used: Pleijel, H. (2008). Concentration gradients of ozone and other trace gases in and above cereal canopies. Meteorologische Zeitschrift 17, 1-6. This was with barley. Concentration was measrued above and inside the canopy, meteorology only above the canopy. If the data would be useful I can probably find them.

Dear Ivan,

you are looking for a very complex dataset. "Concentration" (or mixing ratio) profiles above canopies are highly dynamic, strongly conditioned by air stability (hence, windspeed and sensible heat flux) and momentum exchange (also dependent on canopy roughness). The complexity of the regime increases approaching the canopy (the "roughness" layer), and becomes very difficult to predict and model inside the canopy space (in spite of the first approaches, like Uchijima, Z. and Wright, J.L., 1964. An experimental study of air flow in a corn plant-air layer. The Bulletin of the National Institute of Agricultural Sciences (Japan) Series A, 11: 19-65.). For a long time (until late 70's), however, the measurements and the interpretation of these "profiles" have been the cornestones of micrometeorology (for a final, beautiful summary of this era, see for instance Thom (1975), "Momentum, mass and heat exchange of plant communities", in the book "Vegetation and the Atmosphere" edited by John Monteith.). Soon after, this picture collapsed abruptly, especially in relation to the work of the Canberra school (Denmead, Raupach, Finnigan, and many others). Their work opened the way to a more modern understanding of canopy-atmosphere interactions (nice review are by Raupach & Thom (1981) "Turbulence in and above plant canopies", and, more recently, Finnigan (2000) "Turbulence in plant canopies", both published on the Annual Review of Fluid Mechanics.

Anyway, writing this short story, I remember some (old) papers reporting CO2 profiles (along with main meteorological parameters) above wheat:

Denmead, O.T., 1969. Comparative micrometeorology of a wheat field and a forest of Pinus radiata. Agricultural Meteorology, 6(5): 357-371.

Pearman, G.I. and Garratt, J.R., 1973. Carbon dioxide measurements above a wheat crop, 1. Observations of vertical gradients and concentrations. Agricultural Meteorology, 12: 13-25.

Baldocchi, D., 1994. A comparative study of mass and energy exchange rates over a closed C3 (wheat) and an open C4 (corn) crop: II. CO2 exchange and water use efficiency. Agricultural and Forest Meteorology, 67(3-4): 291-321.

I sincerely hope I have not be too boring and I wish you to find out what you need: for sure, the papers I reported relied exactly on the dataset you are looking for.

Kind regards, Andrea

Great thanks to both responsers - Håkan and Andrea for their answers and the proposed references. I will study all papers, especially the paper of Pleijel, H. (2008) and will come back with questions.

To Andrea: you are right about the complexity of the subject. It is extremely difficult to predict short-term averaged profiles, but if we need the long-averaged concentrations existing theories may be more or less suitable (see e.g. paper at my page Kovalets and Avila, 2012. Proc. of BIOPROTA Project Meeting )

Our research group (myself, Margaret Torn, Sebastien Biraud, and formerly Marc Fischer) has been measuring fluxes of CO2, H2O, and energy as well as precise mixing ratios of CO2 and other trace gases at the U.S. DOE-ARM Central Facility site in north-central Oklahoma for the last 10 or so years. Mostly the field we work at is planted in winter wheat. All of this data is freely available for download at the ARM archives and at the AmeriFlux archives.

Also, there are other agricultural cropping system data available at the AmeirFlux archives. I would caution you to contact the investigators before using the data as there may be some important caveats that you would need to be aware of such as the precision and accuracy of the reported mixing ratios.

Thanks, Dave, I will try to find the data that you mention. If not only concentrations but also fluxes are there this is great. Concerning caution note, I understand that experimental data may contain many caveats about which people who do simulations may be not fully aware. Therefore in my work I try to collaborate with experimentallists who actually did measurements, especially when working with raw data.

Glad this helps. Our data sets from southern U.S. Great Plains do contain fluxes and mixing ratios. The mixing ratio data include heights of 2.5, 4, 25, and 60 meters above the ground continuously at 30 minute intervals. In addition, we've been flying an aircraft-based system that samples much higher, but not as frequently. Again, this is all at the U.S. DOE-ARM site in north-central Oklahoma. This facility also makes a lot of other measurements that may be of use to you such as baloon sondes, SODAR, radar, and LiDAR to define the top of the boundary layer.

Unfortunately I need also at least 1 concentration measurement inside the canopy layer or at the top of it. Anyway, I will have a look at your data.

Hi all, and thanks, Ivan, for appreciating the hints I gave. As you were explicitly asking for profiles, in- and above-canopy, and *not* for fluxes, I tried to go back in time, when estimates of fluxes were obtained from gradients. This procedure just faded away, when the development of sonic anemometer pushed (almost) everybody towards the measurement of eddy fluxes *above* (and only) the canopy

This does not mean that canopy micrometeorologist do not measure profiles anymore, but that is done (I would say) *only* to estimate the "storage" of scalars in the canopy space. Thus, you will rarely find around today high temporal resolution datasets as the one you asked.

Again, regards.

Andrea

Andrea is correct. For short stature ecosystems, mixing ratio profiles are not needed to accurately estimate fluxes. In wheat, I know of no one who is doing sub-canopy measurements. I know of one site that does this in maze (corn), but mostly these measurements are done in forest ecosystems where storage is substantial.

Yes, the reference I gave of Uchijima and Wright is a good example of the vivid hope the canopy community had to connect *smoothly* in-canopy and lower atmosphere regimes. Japanese (and Russian) researchers were leading the game, at that time. But -say- 15 years later everything changed. Very seldom, today, people look at the same time to vertical gradients *and* fluxes (Wilson, J.D., 2013. Turbulent Schmidt Numbers Above a Wheat Crop. Boundary-Layer Meteorology, 148(2): 255-268.). Measuring fluxes had become so easy (?)... And, at the end, that is what interest people today.

Best, Andrea

Dear Andrea and Dave, thanks for clarifications, they are indeed very useful.

My interest is caused by the specific problem of estimation of C-14 accumulation in crops like wheat and barley following the routine releases (in the form of 14CO2 ) from the nuclear waste storage facilities and/or nuclear power plants. Therefore in the 'best' case I'd like to have both concentration and flux together with meteorological measurements, while in 'suboptimal' case I'd like to have concentration + meteorological measurements.

OK, I see. And I recognize the high scientific and practical value of your research.

You know, when somebody ask about CO2 concentration profiles above a crop canopy, today one immediately think (only!) about photosynthesis (and, thus, fluxes...). Your need, actually, could be closer to the community of "pollutant" fluxes (NH3... O3...), which are still forced to measure gradients and profiles, just because no fast analyzer is available yet, to do eddy covariance measurements!

By the way, I enjoyed the discussion, and again advice you to dig in old datasets to fulfill your aims.

Best, Andrea

Dear Ivan,

Try searching on the resource: http://www.wikience.org/

Regards, Vitalii