October 22, 2004
Raymond A. McCord, William W. Hargrove, Craig C. Brandt, and Henriette I. Jager
Environmental Sciences Divsion
Oak Ridge National Laboratory
Funds were established in FY 2000 for facilitation of carbon cycle
research within the
Atmospheric Research Measurement (ARM) Program. Two primary activities
were identified
for the "facilitation" of carbon cycle research:
The efforts to develop and use
data products for carbon cycle research from existing ARM data
are summarized in this report.
The processing required for the data products included concatenation, filtering, aggregation, QA screening, and gap filling. Each of these processes are summarized below. Additional details about data processing can be found at "Processing ARM Data For Carbon Modeling" (see this section of this reference).
The measurements collected by ARM are structured into data streams composed of daily files and aggregated by source instrument (or instrument group). The information needed for the ARM Carbon data products was distributed across several ARM data streams, intermingled with unneeded measurements (for carbon purposes), and distributed through 10,000's of daily data files. The first data processing step for these data products was to request the ARM data files from the Archive, concatenate the daily data files into yearly segments, and remove unneeded data fields.
The ARM measurements are also collected at differing time intervals. After the data files were reorganized, the data with higher temporal resolution were aggregated into useful time intervals (usually hourly or daily). The aggregations include the computation of appropriate statistics (mean, total, minimum, etc.).
The ARM measurements were also filtered for quality problems based on the following logic:
The data products used as "driver files" for carbon cycle models need to be complete (no missing time steps or missing input values within a time step). Observational data are always incomplete. We evaluated and implemented a statistical approach to fill in the data gaps. This approach includes searching for related values in both temporal and spatial contexts. More information about the gap filling methods and results
Part of the effort expended to ‚Ç£sell‚Ç¥ the usefulness of the data products to the carbon research community included using examples of the data products with carbon models. We conducted formal studies with widely used carbon models and compared the modeling results that would be obtained with regionally available measurements (e.g., weather station) vs. the more specific and intense ARM measurements. A daily aggregation of ARM data was used with the Biome-BGC model. The estimates of shortwave radiation based on ARM data were greater than regional estimates for this parameter. This difference was reflected by greater values of Net Ecosystem Production from this model when the ARM data were used as input. More information about the results of the study can be found at http://www.arm.gov/publications/proceedings/conf12/extended_abs/hargrove-ww.pdf .
Another study was started with the SiBD model with hourly data products extracted from ARM. Generating the hourly data files for the SiBD experiments forced us to address gap filling techniques. Results from the GAP filling for the SiBD model were presented in a poster at AGU in 2003 . The SiBD model is still being used to evaluate the usefulness of the soil water and temperature data collected by ARM. Access data products that are useful with SiBD
A final "evaluation exercise" included preliminary efforts to compare the soil water measurements contained in the SWATS data with the water profile estimated by simulation runs with the SIB-D model. This comparison is different type of use for ARM data. This experiment was in process when the project ended. Access SWATS data products and a few very preliminary results
Table 1 Professional meetings attended
on behalf of ARM Carbon Collaborations.
Meeting name |
2002 |
2003 |
2004 |
ARM Science Team Meeting |
X |
X |
X |
American Geophysical Union |
X |
X |
|
Ameriflux Meeting |
X |
X |
|
Ecological Society of America |
X |
||
MODIS Modland workshop |
X |
X |
|
North American Carbon Program
Meeting |
X |
X |
Table 2 Posters and presentations at professional meetings.
. |
Hargrove, W. W., C. C. Brandt, H. I. Jager, and R. A. McCord. 2002. A "Make-a-Difference" Experiment to Assess the Value of ARM Data in Carbon Cycle Models (poster and extended abstract; http://www.arm.gov/docs/documents/technical/conf_0204/hargrove-ww.pdf ). Twelfth ARM Science Team Meeting Proceedings, April 8-12, 2002, St. Petersburg, Florida |
. |
Hargrove, W. W., Brandt, C.
C., Jager, H. I., Hanan, N., and McCord, R.A. 2003. Characterizing
and Filling Temporal and Spatial Gaps in Time-Aggregated ARM
Measurements for Use in
Carbon Models. (abstract) Thirteenth ARM Science Team Meeting
Proceedings, March 31 -
April 4, 2003, Broomfield, Colorado. |
. |
Hargrove, W. W., C. C. Brandt, H. I. Jager, and R. A. McCord. 2002. A "Make-A-Difference" Experiment to Assess the Value of ARM Data in Carbon Cycle Models. Eos Trans., AGU, 83(47), Fall Meet. Suppl., Abstract A12A-0136. |
. |
McCord, R. A., W. W. Hargrove, H. I. Jager, C. C. Brandt, and N. Hanan. 2003. Characterizing and Filling Data Gaps in ARM Measurements for Carbon Models. Eos Trans. AGU, 84(46), Fall Meet. Suppl., Abstract B22A-0805 |
A professional mixer about ARM Carbon measurements and data products was collaboratively sponsored by ORNL and LBNL at the Fall 2004 AGU meeting. This event was attended by about 25 researchers. The workshop resulted in identification of potential future collaborations between ARM and NASA on space-based carbon observations. The proposed activities would use ARM data from SGP and TWP sites. More information on this proposed future collaboration can be found at these links: at SGP, at TWP
We established a small consulting subcontract with Dr. Niall Hanan at Colorado State University. The purpose of the contract was to get detailed advice on the design of data products and assistance with interacting with groups of carbon researchers. Dr. Hanan also provided assistance with our use of the SiB model. Future collaborations beyond this project and contract are expected to continue the evaluation of the SiB model with the ARM soil water data.
We prepared a review of the potential use of the ARM facilities for future North American Carbon Program activities. For several months, the potential of the ARM sites was included in the NACP planning documents. However, subsequent planning resulted in the interests of NACP being focused on other regions. Access the review
In addition to the presentations and evaluations described in the previous sections, we accumulated several data products and data plots. The section provides overview documentation for each of the data products resulting from this project.
Data files with hourly statistics derived from ARM measurements and suitable for "driving" the SiB carbon model were generated from most of the ARM SGP extended facilities from 1996 through 2000. These files contain results that are filtered based on QA information and have complete records from "gap filling." These files are documented and available
Data plots showing the SiB driver parameters were generated to confirm the reasonableness of the data products and evaluate the sufficiency of the gap filling estimates. These plots are being retained because the large scale (monthly) view of ARM data are not readily accessible from any other sources. These plots are documented and available
The preparation of the SIB driver files resulting in the merging of measurements from several ARM data streams. More extensive statistics (e.g., mean, min, max, standard deviation, etc.) were computed for each time interval and many related measurements (e.g., secondary radiation measurements). These extended statistics and measurements may be enable future use of ARM data with other carbon cycle models. These data files are available at: <<<< need to add reference after Craig gets the files generated and we have them stored >>>>>
The ARM program has collected a significant amount of soil water and temperature measurements (hourly data at 19 extended facility locations) since 1996. Data files that could be compared with the soil water estimates included in many carbon models are available. One version of these data is a "best estimate." These data products have been filtered to remove invalid or unreasonable values. The data products have also condensed to present the best single or averaged result from the redundant arrays of sensors at each location. A secondary version of the data product includes the "uestionable" data values with detailed QA flags. Additional documentation Access best estimate data files Access detailed data files
Data plots showing the soil water
and temperature "best estimate" data product were generated to
confirm the reasonableness of this data summary. These plots are useful
to observe the
systematic differences in soil moisture profiles and seasonal trends
between the many installations. The data plots also provide a long time
scale view of the measurements that is not readily
available from other sources. Access
plots.
There are many other applications of ARM data for carbon cycle research that could be pursued in the future. This section provides a brief description of future activities that we had planned to pursue.
The spatial spread and intensity of the ARM extended facilities is unusual for the combination of measurements being collected. We suggest that generating spatially interpolated estimates of the measurements and using them with a regional model (multiple points, or area logic) could have interesting results. The addition of routine measurement land surface conditions could result in data set that is not replicated in any other location.
Latent heat measurements are representative of evapotranspiration. This environmental parameter may have significant relationship to carbon flux. ARM has been collecting this measurement with the EBBR instrument at 9 locations for over 10 years. We considered preparing data products from the ARM EBBR data streams that could be compared to another portion of the carbon cycle models. However, an adjustment is needed to accommodate known spikes in the measurement process. A version of this adjustment was implemented in the ARM Value Added Product (VAP) for the EBBR. However, the implementation of this adjustment has some uncertainty and this VAP is currently not in production.
The soil water and temperature data are currently being considered for model validation. Another research project could be to use these measurements for input into the models. This would require significant (but possibly beneficial) revisions to most of the current carbon cycle models. Methods to fill data gaps for these types of measurements would also need development.
Measurements collected by the ARM Carbon project at LBNL include CO2 flux and high precision CO2 concentrations. These measurements should be combined with other ARM measurements. A data set similar to Ameriflux data products could be developed from this combined source of measurements. These measurements combined with the new ECOR data (discussed below) have the potential to provide a relatively dense (spatially) collection of this type of measurements. Most of the Ameriflux locations are wide distributed.
In the Fall of 2003, ARM upgraded all of its Eddy Correlation (ECOR) instruments to include CO2 Flux measurements. (Regrettably the ARM information still does not explain this change, but the CO2 are included in currently generated data files.) These instruments are distributed among 9 of the SGP extended facilities. As this data collection accumulates, these measurements should be useful for comparison with carbon cycle models of the ARM facilities. Because the facilities represent replicates of a few land use types (grassland / pasture, crops, and mixed), the replication and density of these measurements could provide some new research opportunities.
The results of this project are considered "mixed."
Some aspects of the project were positive: