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NDACC News and Highlights
NDACC News and Highlights
This section highlights significant items of interest within NDACC.
2016 marks 25 years of successful operations of NDACC for enabling and enhancing global atmospheric research. A comprehensive review article commemorating this anniversary appears in the September-October 2016 issue of NASA’s Earth Observer Newsletter. The newsletter is a bi-monthly publication that consolidates NASA Earth Science news and has a readership of more than 6000 internationally. The article “The Network for the Detection of Atmospheric Composition Change: 25 Years Old and Going Strong” can be accessed at http://eospso.nasa.gov/earthobserver/sep-oct-2016.
Following a general introduction to NDACC, the article includes information on the historical context for the formation of such a network leading to the initial establishment of the Network for the Detection of Stratospheric Change (NDSC). Details on the original organizational structure of NDSC, an assessment of the first 10 years of NDSC operations, and the transition of NDSC to NDACC follow. Additional information is provided on the continuing evolution of NDACC, its current measurement capabilities, and the role of NDACC Cooperating Networks. Examples of several significant contributions and results from 25 years of NDSC/NDACC operations are also highlighted. The article continues with a section on “The Path Forward” in which the network’s organizational flexibility, data access improvements, and data quality assurance activities are described. The concluding section emphasizes that NDACC stands as a shining example of what can be achieved through international cooperation and from the continuity and quality assurance in measurements and their analyses. Past issues of the Earth Observer Newsletter are available at http://eospso.nasa.gov/earth-observer-archive.
The annual meeting of the international Steering Committee (SC) for NDACC was held from October 17 to 21 in Bremen, Germany at the University of Bremen Guesthouse ‘Teerhof’. Justus Notholt of the University of Bremen hosted the meeting.
The meeting began with a detailed report from the NDACC Data Host Facility (DHF) on the status of data archiving and on data utilization. This was followed by reports from the NDACC Instrument Working Groups (IWGs). As in the past, these reports highlighted IWG activities and/or meetings during the past year, summarized NDACC measurement and analysis activities and recent accomplishments, reviewed the status of proposals (received and pending) seeking NDACC measurement affiliation, and outlined possible new sites for consideration. While there are some cases where data archiving is not up to date, these are becoming smaller in number due to the proactive involvement of the various IWG Co-Chairs and the DHF Manager in contacting the people responsible for data submission from the various sites and assisting them in resolving any issues associated with such submission. The IWG Co-Chairs will continue to work with the DHF representative to reduce even further the number of cases of delinquent data archiving.
The Satellite Working Group updated the current international satellite inventory for atmospheric observations and their current and future validation needs, and indicated how NDACC data could be made more valuable for such activities, especially in the light of upcoming geostationary satellites. The Theory and Analysis WG presentation included a summary of the data files recently generated using chemistry transport models and their use for bridging the irregular space and time sampling of ground-based measurements and the global perspective. In addition this WG described how NDACC column measurements could be used to assess the credibility of residual circulation trends in reanalysis products. The NDACC Cooperating Network (CN) presentations focused on new CN activities and initiatives pertinent to NDACC interests and to possible future inter-network collaborations. The Water Vapor Measurement Strategy Theme Group provided an update on the strategy document, which includes lidar, microwave, and FTIR measurement capabilities as well as frost point sondes. The strategy document will be augmented with an appendix referring to results on past intercomparisons between measurement techniques. In particular the presentation stressed the importance of establishing realistic uncertainties in frost point data, data from the other NDACC water vapor instruments, and water vapor data from other networks. The Theme Group for Combining Trace Gas Data from NDACC and its Cooperating Networks presented a status report on Group’s activity (its near term priorities and the scientists who will be participating).
Other presentations at the meeting included:
The SC was also treated to a number of excellent presentations on the research being conducted by local scientists and by SC members themselves. A complete list of these presentations can be accessed via the “Agenda” link provided above.
A number of miscellaneous discussions followed covering such items as changes and improvements to the NDACC web site, NDACC involvement in and data availability for various international projects, including ACTRIS and the Copernicus Services, and NDACC communications (including an introductory paper for the inter-journal Special Issue commemorating NDACC’s 25th year anniversary), future strategies and implementation, and updates to the various operational protocols for the network.
Possible venues for the 2017 and 2018 SC meetings were discussed and the decision was made to hold the 2017 meeting in Buenos Ares, Argentina coupled with a site visit to Rio Gallegos and the 2018 meeting in Boulder, CO. Consideration is being given to holding the 2019 meeting in Asia (possibly in China). Following the close of the meeting, many SC members visited the Alfred Wegener Institute in Bremerhaven where they were given an overview of polar research and sea exploration activities and a tour of the ice laboratory. While in Bremerhaven they also had the opportunity to visit the Klimahaus (Climate House) and German Maritime Museums.
A global network of stations using Dobson and Brewer spectrophotometer have been monitoring the status of the ozone layer during several decades. Corresponding calibration systems have been developed to ensure the good and constant data quality in this network, which enables the scientific society to detect the depletion of the ozone layer and the Antarctic ozone hole in the 80ties. One World Dobson Calibration Center (WDCC) at NOAA (Boulder) and five Regional Dobson Calibration Centers (RDCC) in the corresponding WMO Regional Associations use standard Dobsons for this purpose.
When EURAMET (European Association of National Metrology Institutes) started the project ATMOZ (Traceability for Atmospheric Total Ozone) within the EMRP (European Metrological Research Programme) in October 2014, particularly standard instruments should be characterised to improve their performance. WDCC and the European RDCC-E (Meteorological Observatory Hohenpeissenberg, Germany, and Solar and Ozone Observatory Hradec Kralove, Czech Republic) took the chance to join this project as collaborators. In the meanwhile the primary standard Dobson D083 and the two regional standards D064 and D074 have been optically characterised (wavelength settings, bandwidths) at the Physikalisch-Technische Bundesanstalt PTB (Braunschweig, Germany) and the Czech Metrology Institute CMI (Prag, Czech Republic).
A large field validation and intercomparison campaign for all participating groups and instruments (not only Dobson and Brewer) was held at the Izana Atmospheric Research Center on Tenerife from September 12 to 30, 2016. Main aims of this campaign were to apply the results of the laboratory investigations and to compare all participating instruments.
Glen McConville (NOAA), Martin Stanek (CHMI) and Ulf Köhler/Michael Heinen (DWD) came to this campaign with their Dobsons to:
Preliminary results look very promising and confirm the outcome of previous intercomparison campaigns (Figure 1). The agreement between all three Dobsons (AD observations) and the Canadian traveling standard Brewer No. 017 is within ± 1% over the whole range.
Figure 1: Comparison of standard Dobsons and Brewer on September 16, 2016
Figure 2 shows a first analysis of the Langley observations from September 14 to 20 for the Dobson No. 064. It reveals, that the derived ETC-corrections for the AD- (-0.03) and CD-data (0.16) are very small.
Figure 2: First results of the Langley Plot method for D064 to do an absolute calibration.
Final data processing will include the effective absorption coefficients (individual for each instrument according its bandwidths), derived during the ATMOZ laboratory measurements incl. consideration of the effective temperature in the ozone layer above Izana.
The outcome of these activities in the ATMOZ project (laboratory measurements and field campaign) will hopefully improve the function and data quality of the standard instruments. Subsequently the data quality in the global network will be improved too and these high quality data will facilitate the detection of the recovery of the ozone layer.
The three AMT companion papers can be found at:
Part 1 provides recommendations for the use of two standardized definitions of vertical resolution, and has a supplement reviewing several digital filters useful for lidar data processing. The recommended preferred vertical resolution definition uses the full-width-at-half-maximum of the response to a finite impulse, and must be reported in the NDACC data files written in HDF format. Another definition, based on the frequency cut-off of digital filters can optionally be reported in the NDACC HDF data files.
Parts 2 and 3 provide recommendations for a standardized approach for the computation of the ozone DIAL and temperature lidar uncertainty budgets respectively. Several variables in the NDACC data files written in HDF format are specifically reserved for the reporting of uncertainty following the recommended approach. Additional details related to material covered in all three companion papers can be found in the full ISSI Team Report located at http://www.issibern.ch/teams/ndacc/ .
The seventh SPARC science report on 'The Mystery of Carbon Tetrachloride' is now available! The full report helps to answer policy-relevant questions related to the global budget of carbon tetrachloride, an important ozone-depleting substance, closing the gap between emission reported to UNEP's Ozone Secretariat and those estimated from atmospheric observations.
Several members of the NDACC community were involved in the preparation of this report.
Report editors: Qing Liang, Paul A. Newman, and Stefan Reimann.
The 8th Implementation and Coordination Meeting (ICM-8) of the GCOS Reference Upper-Air Network (GRUAN) was held in Boulder, CO (25-29 April 2016). GRUAN and NDACC have had a long-standing collaboration (dating back to ICM-1 in 2009) that was further formalized by both GRUAN and NDACC becoming Cooperating Networks. NDACC scientists are playing increasingly important roles on the various GRUAN Task Teams and in the development of GRUAN Technical Documents for defining the needs and roles of ancillary measurements from other established networks such as NDACC.
The primary NDACC presentation at ICM-8 was given by Mike Kurylo who focused on recent implementations, activities, and scientific highlights (presented and discussed at the October 2015 meeting of the NDACC Steering Committee) that are pertinent to the growing partnership between the two networks. These included a summary of Data Host Facility issues facing a mature and growing network and the recent interactions between the Theory and Analysis Working Group and the Instrument Working Groups (IWGs) in an effort to provide a bridge between measurements obtained at individual NDACC stations and the global perspective. He pointed out that model simulations by the Theory and Analysis Working Group will help set priorities for network expansion and/or instrument relocation while building on GRUAN RP-4: Outcomes of the GRUAN Network Expansion Workshop. A preliminary work plan from the newly formed Combining Trace Gas Data Theme Group was also outlined.
Of particular interest to GRUAN, was the status of an NDACC-wide Water Vapor Measurement Strategy. Mike listed a number of strategic considerations that are being considered in this development and emphasized that cooperation with GRUAN is essential. While complete instrument duplication within NDACC and GRUAN is probably not necessary, overlap in the "climate critical" region of the atmosphere is essential.
His presentation also focused on the level to which centralized data processing might be achievable for the various NDACC instrument types (Dobson/Brewer, FTIR, Lidar, Microwave, Sondes, UV/Visible, and Spectral UV). This issue is a consideration within the NDACC IWGs, first taking into account unique instrument aspects and their maturities and the potential for algorithm harmonization. Mike discussed the need to balance the positive aspects of such centralization with a number of issues and concerns. He highlighted various activities within each of the IWGs in moving forward, including participation in several international projects focusing on data characterization and harmonization, data processing standardization, and documentation to ensure traceability and consistency. The path forward for a network like NDACC, which certifies many different PI-developed measurement capabilities, is complex. Initial efforts within each IWG continue to focus on the homogenization of data processing and reporting. GRUAN developments and decisions (particularly in the area of the certification of a water vapor data product) will be closely followed.
Complete details about GRUAN and its objective can be found on the GRUAN web site http://www.dwd.de/EN/research/international_programme/gruan/home.html where the full agenda for ICM8 can also be accessed. Numerous presentations were given by NDACC scientists or by scientists representing programs that are cooperative with NDACC. Of particular note were updates on the drafting of GRUAN Technical Documents for Lidar measurements (Thierry Leblanc – Lidar IWG), FTIR measurements (Jim Hannigan - FTIR IWG), and Ozonesonde measurements (Jacquie Witte – SHADOZ Representative). Herman Smit discussed progress on the homogenization of ozone records under WMO/GAW and the Ozone Sonde Data Quality Assessment (O3S-DQA) in which both NDACC and SHADOZ have played significant roles. Dale Hurst (NDACC Sonde IWG) spoke about new developments in controlled balloon ascents and descents for improved data acquisition and on the comparison of water vapor measurements from frost point hygrometers and from the Aura MLS satellite instrument. Summaries of field measurement activities at four joint NDACC and GRUAN sites were presented by Marion Maturilli (Ny Ålesund), Rigil Kivi (Sodankylä), Stephanie Evan (Reunion Island), and Richard Querel and Jordis Tradowsky (Lauder). The GRUAN Lead Center is preparing a comprehensive ICM-8 meeting report for future posting on the GRUAN web site. This report will include presentation summaries prepared by the speakers and rapporteurs.
Until recently, the abundance of atmospheric ethane (C2H6) has been declining, primarily due to reduced fugitive emissions from oil and gas activities and to the successful implementation of pollution abatement measures. However, a study published early 2015 in Journal of Quantitative Spectroscopy and Radiative Transfer (doi:10.1016/j.jqsrt.2015.03.017) reported a reversal in the long-term evolution of ethane and a sharp increase of its abundance after 2009 over central Europe, using the multi-decadal ethane time series from the high-altitude NDACC site of the Jungfraujoch (Swiss Alps). Large fugitive emissions associated with the massive hydraulic fracturing and shale gas operations in the U.S. were incriminated. Simultaneously, positive anomalies of hydrocarbons related to venting, flaring and leakage from oil and gas operations were detected at U.S. locations downwind from active wells, as well as large methane emissions by space-borne remote-sensing over U.S. regions with high drilling productivity.
In a new NDACC study coordinated at the University of Liège (Belgium) and recently published in Environmental Research Letters (doi:10.1088/1748-9326/11/4/044010), consistent retrievals of ethane total columns from ground-based Fourier Transform Infrared (FTIR) observations made at five NDACC sites are used to characterize the recent ethane evolution over North America. They reveal growth rates close to 5%/yr at mid-latitudes and 3%/yr at remote sites from 2009 onwards (see Figure), corroborating the increase observed over the Jungfraujoch.
Thanks to state-of-the-art 3-D model simulations, the study further reveals that the best inventories currently available for anthropogenic emissions significantly underestimate the ethane emissions prior to 2009 by no less than a factor two. It is also shown that the North American anthropogenic annual emissions of ethane have increased by 75%, from 1.6 Tg/yr in 2008 to 2.8 Tg/yr in 2014. These figures are corroborated by satellite-based emissions of ethane from North American oil and natural gas, biofuel consumption and biomass burning inferred from GOSAT observations of methane (CH4), when using C2H6/CH4 emission ratios accounting for the natural gas composition.
These independent results contribute to underscoring the large impact of the emissions associated with hydraulic fracturing and shale gas operations in North America on the air quality degradation. Moreover, the top-down approach offers the opportunity to allocate the ethane emissions on the basis of measurements, for a more accurate representation of recent atmospheric composition changes.
Finally, this study estimates that the annual emissions of methane – the second most important anthropogenic greenhouse gas – have increased from 20 to 35 Tg/yr over the period 2008-2014, because of the expansion of oil and natural gas extraction in North America.
Reference: Franco B, Mahieu E, Emmons L K, Tzompa-Sosa Z A, Fischer E V, Sudo K, Bovy B, Conway S, Griffin D, Hannigan J W, Strong K, and Walker K A (2016) Evaluating ethane and methane emissions associated with the development of oil and natural gas extraction in North America, Environ. Res. Lett., 11, 044010, doi:10.1088/1748-9326/11/4/044010
Tropospheric ozone is an important greenhouse gas and an air pollutant impacting human health and vegetation. Recent studies highlight the importance of increasing the number of tropospheric ozone profiling stations and long-term measurements to fully understand its sources and variability. The NDACC station of JPL-Table Mountain Facility (TMF, elev. 2285 m, California) has been operating a tropospheric ozone DIAL system since 1999, thus providing high vertical resolution profiles of ozone throughout the troposphere and lower stratosphere (3-24 km). Measurements are performed 3-5 days a week typically during two hours at nighttime. Surface ozone measurements complement the lidar profiles since 2013.
Results from the combined analysis of the surface and tropospheric ozone lidar profiles have been recently submitted to the NDACC 25th Anniversary Special Issue of Atmospheric Chemistry and Physics (doi:10.5194/acp-2016-70). The study reveals that ozone at the surface is typical of free tropospheric background conditions with small amplitude of the seasonal and diurnal cycles and high ozone values, compared to neighboring stations affected by the Los Angeles urban boundary layer conditions. The lidar observations show that the seasonal cycle observed at the surface, with maxima in spring and summer, extends throughout the free-troposphere.
Trend analysis of the lidar data reveals a statistically significant positive trend of 0.31 ppbv.year-1 in the free troposphere for the period 2000-2015. To identify the causes of this trend, a classification of the air parcels sampled by lidar was performed using backward trajectories. This classification reveals the dominant influence of the Eastern and Central Pacific Ocean, with air parcels of low ozone content (50-65 ppbv). In summer, enhanced ozone values (70 ppbv) are found in air parcels originating from Central America, which can be interpreted as local production by NOx due to enhanced thunderstorm activity during the North American Monsoon. Finally, in winter and spring, significant influence of the stratosphere leading to ozone values of 65-80 ppbv down to 8-9 km is also observed.
Due to the position of TMF with respect to the subtropical jet, stratospheric influence is easily identified during the frequent tropopause folds found in the vicinity of the site (27% of the time, mostly in winter and spring). A dual vertical structure in ozone is observed within the fold layer, with lower-than-averaged values in the top half of the fold (14-18 km), and higher-than-average values in the bottom half of the fold (12-14 km). This influence extends down to the lower troposphere, with an average ozone increase of 2 ppbv in cases of tropopause folds compared to non-tropopause fold days.
The study concludes that the quantitative impact of stratosphere-troposphere exchange cannot be ignored in tropospheric ozone studies, especially in view of the frequency of occurrence of tropopause folds. The current study will therefore be extended to quantify the impact of the tropopause folds in the observed tropospheric ozone interannual variability and trends.
Reference: Granados-Muñoz, M. J. and Leblanc, T.: Tropospheric Ozone Seasonal and Long-term Variability as seen by lidar and surface measurements at the JPL-Table Mountain Facility, California, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-70, in review, 2016.
Copyright 2016 Californina Institute of Technology. U.S. Government
Like carbon dioxide, methane is one of the most important greenhouse gases. After a period of stagnation around 2000, atmospheric methane concentrations started to rise again in 2007. So far, the causes have been unknown. According to the recent study of climate scientists of Karlsruhe Institute of Technology (KIT), at least 40% of this increase result from the growing production of oil and natural gas in the northern hemisphere. The results are now published in the “Atmospheric Chemistry and Physics” journal. (DOI:10.5194/acp-16-3227-2016)
“The attribution to thermogenic methane from the oil and natural gas industry is based on our vertical measurements of ethane and methane concentrations between the ground and the uppermost layers of the Earth’s atmosphere,” says the initiator of the study associate professor Ralf Sussmann of the Atmospheric Environmental Research Division of KIT’s Institute of Meteorology and Climate Research (IMK-IFU). Ethane is essential for quantifying the contribution of thermogenic methane. Like methane, it is a hydrocarbon compound and one of the main components of natural gas. In case of biogenic methane sources, no ethane is produced.
The study is based on long-term measurements by the KIT team at the NDACC site at the Zugspitze summit and by climate researchers of the National Institute of Water and Atmospheric Research at the NDACC site Lauder, New Zealand. The column measurements are representative of the background concentration of methane and ethane in both hemispheres of the Earth. While measurements at the Zugspitze show a significant correlation between ethane and methane, i.e. a sudden increase of the concentrations of both trace gases from 2007 onwards, the Lauder scientists have observed a similar renewed increase for methane only. From these measurement results, the scientists concluded that at least 40% of the worldwide methane concentration increase after 2007 have to be attributed to the oil and gas sector and that the emissions took place in the northern hemisphere.
Reference: Hausmann, Petra, Sussmann, Ralf, and Smale, Dan: Contribution of oil and natural gas production to renewed increase in atmospheric methane (2007–2014): top-down estimate from ethane and methane column observations, www.atmos-chem-phys.net/16/3227/2016/