The Total Carbon Column Observing Network (TCCON) is a global network of instruments that measure the amount of

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

nitrous oxide Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or factitious air, among others, is a chemical compound, an Nitrogen oxide, oxide of nitrogen with the Chemical formula, formula . At room te ...

and other

trace gas Trace gases are gases that are present in small amounts within an environment such as a planet's atmosphere. Trace gases in Earth's atmosphere are gases other than nitrogen (78.1%), oxygen (20.9%), and argon (0.934%) which, in combination, make u ...

es in the

Earth's atmosphere The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weathe ...

. The TCCON ( ) began in 2004 with the installation of the first instrument in

Park Falls, Wisconsin Park Falls is a city in Price County, Wisconsin, United States. The population was 2,410 at the 2020 United States census, 2020 census, down from 2,462 at 2010 United States census, 2010. Located in the woods of north central Wisconsin, primarily ...

, USA, and has since grown to 23 operational instruments worldwide, with 7 former sites. The TCCON is designed to investigate several things, including the flow (or

flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phe ...

) of carbon between the atmosphere, land, and ocean (the so-called carbon budget or

carbon cycle The carbon cycle is a part of the biogeochemical cycle where carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of Earth. Other major biogeochemical cycles include the nitrogen cycle and the water cycl ...

). This is achieved by measuring the atmospheric mass of carbon (the airborne fraction). The TCCON measurements have improved the scientific community's understanding of the

,Yang, Z., R. A. Washenfelder, G. Keppel-Aleks, N. Y. Krakauer, J. T. Randerson, P. P. Tans, C. Sweeney, and P. O. Wennberg (2007), New constraints on Northern Hemisphere growing season net flux, Geophysical Research Letters, 34(12), 1-6, . Available from: http://www.agu.org/pubs/crossref/2007/2007GL029742.shtmlChevallier, F. et al. (2011), Global CO 2 fluxes inferred from surface air-sample measurements and from TCCON retrievals of the CO2 total column, Geophysical Research Letters, 38(24), 1-5, . Available from: http://www.agu.org/pubs/crossref/201...GL049899.shtml and urban

greenhouse gas emissions Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning fossil fuels such as coal, petroleum, oil, and natural gas, is the main cause of climate chan ...

.Verifying Greenhouse Gas Emissions: Methods to Support International Climate Agreements, http://www.nap.edu/catalog/12883.html The TCCON supports several satellite instruments by providing an independent measurement to compare (or validate) the satellite measurements of the atmosphere over the TCCON site locations.Boland, S. et al. (2009), The Need for Atmospheric Carbon Dioxide Measurements from Space : Contributions from a Rapid Reflight of the Orbiting Carbon Observatory, http://www.nasa.gov/pdf/363474main_OCO_Reflight.pdf The TCCON provides the primary measurement validation dataset for the Orbiting Carbon Observatory (OCO-2) mission,NASA.gov
/ref> and has been used to validate other space-based measurements of carbon dioxide.

History

The TCCON was established partly because of modeling errors between mixing efficiency between the PBL and the free

troposphere The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the ...

. Because TCCON measurements are of the entire column of atmosphere above a site (PBL and free troposphere are simultaneously measured) the measurements are an improvement over the traditional

in situ is a Latin phrase meaning 'in place' or 'on site', derived from ' ('in') and ' ( ablative of ''situs'', ). The term typically refers to the examination or occurrence of a process within its original context, without relocation. The term is use ...

near surface measurements in this regard. TCCON has improved the CO₂ mass gradient measurements between the northern and southern hemispheres. The first annual TCCON meeting was in

San Francisco, California San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...

in 2005. Every year a meeting is held in a location that rotates between North America, the Western Pacific, and Europe hosted by a participating institution. In 2015 the meeting was held at the

University of Toronto The University of Toronto (UToronto or U of T) is a public university, public research university whose main campus is located on the grounds that surround Queen's Park (Toronto), Queen's Park in Toronto, Ontario, Canada. It was founded by ...

.TCCON Webpage, https://tccon-wiki.caltech.edu/Sites, accessed February 6, 2016

Measurement technique

The main instrument at each TCCON site is a

Bruker Bruker Corporation is an American manufacturer of scientific instruments for molecular and materials research, as well as for industrial and applied analysis. It is headquartered in Billerica, Massachusetts, and is the publicly traded parent comp ...

IFS 125HR (HR for high resolution, ~0.02 cm⁻¹) or occasionally 120HR Fourier transform spectrometer. Sunlight is directed into the spectrometer by solar tracking mirrors and other optics. The spectrometers measure the absorption of direct sunlight by atmospheric

trace gases Trace gases are gases that are present in small amounts within an environment such as a planet's atmosphere. Trace gases in Earth's atmosphere are gases other than nitrogen (78.1%), oxygen (20.9%), and argon (0.934%) which, in combination, make up ...

primarily in the near

infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

region. This

remote sensing Remote sensing is the acquisition of information about an physical object, object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring inform ...

technique produces a precise and accurate measurement of the total column abundance of the

. The main limitation to this technique is that measurements can not be recorded when it is not sunny (i.e. there are no measurements available at nighttime or when there is heavy cloud cover).Wunch, D., G. C. Toon, J.-F. L. Blavier, R. A. Washenfelder, J. Notholt, B. J. Connor, D. W. T. Griffith, V. Sherlock, and P. O. Wennberg (2011), The total carbon column observing network, Philosophical Transactions of the Royal Society - Series A: Mathematical, Physical and Engineering Sciences, 369(1943), 2087-2112, . Available from: http://rsta.royalsocietypublishing.o.../2087.full.pdf

Participating sites and Institutions

Current TCCON sites are located in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korea, Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and t ...

Réunion Réunion (; ; ; known as before 1848) is an island in the Indian Ocean that is an overseas departments and regions of France, overseas department and region of France. Part of the Mascarene Islands, it is located approximately east of the isl ...

, and

Ascension Island Ascension Island is an isolated volcanic island, 7°56′ south of the Equator in the Atlantic Ocean, South Atlantic Ocean. It is about from the coast of Africa and from the coast of South America. It is governed as part of the British Overs ...

. A former site was in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. Sites can change when an instrument needs to be moved to a new location. TCCON members collaborate from a variety of different institutions. In North America some of these include

Caltech The California Institute of Technology (branded as Caltech) is a private university, private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small g ...

, JPL,

Los Alamos National Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development Laboratory, laboratories of the United States Department of Energy National Laboratories, United States Department of Energy ...

, NASA Ames, and the

. In Europe some of these include

Karlsruhe Institute of Technology The Karlsruhe Institute of Technology (KIT; ) is both a German public research university in Karlsruhe, Baden-Württemberg, and a research center of the Helmholtz Association. KIT was created in 2009 when the University of Karlsruhe (), founde ...

, Max Planck Institute for Biogeochemistry,

University of Bremen The University of Bremen () is a public university in Bremen, Germany, with approximately 18,400 students from 117 countries. Its 12 faculties offer more than 100 degree programs. The University of Bremen has been among the top 50 European rese ...

, Agencia Estatal de Meteorología, Royal Belgian Institute for Space Aeronomy, Finnish Meteorological Institute, and Pierre and Marie Curie University. In the western Pacific some of these include

University of Wollongong The University of Wollongong (UOW) is an Australian public university, public research university located in the coastal city of Wollongong, New South Wales, approximately south of Sydney. , the university had an enrolment of more than 33,000 s ...

, National Institute of Water and Atmospheric Research, National Institute for Environmental Studies,

JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into o ...

, and National Institute of Meteorological Research of the Republic of Korea. New sites are admitted into the network when site investigators demonstrate required hardware, and data processing ability. Uniformity is maintained across the network by using the same FTS model and the same retrieval software. GGG is the software of the TCCON. It includes the I2S (interferogram to spectrum) FFT, and GFIT spectral fitting subroutines. GFIT is also the fitting algorithm that was used for ATMOS which flew on the

Space Shuttle The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...

, and is used for spectral fitting of spectra obtained by a balloon borne spectrometer.

Map

Highlights of Data Use

Data from each site is processed by the investigators that head that particular site. Atmospheric abundances of gases are uploaded and saved in uniform formats and data are hosted at

with the Caltech Library and are available from http://tccondata.org. Data are made publicly available provided the data license is followed. Data have been used for a variety of analyses. Some of these include * Emission estimates of methane and carbon monoxide were made for the South Coast Air Basin containing

Los Angeles Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...

using TCCON measurements and the CARB inventory.Wunch, D., P. O. Wennberg, G. C. Toon, G. Keppel-Aleks, and Y. G. Yavin (2009), Emissions of greenhouse gases from a North American megacity, Geophys. Res. Lett., 36, L15810, doi:10.1029/2009GL039825. * Characterization of biosphere fluxes in the Southern Hemisphere * Evaluation of the seasonal exchange of CO₂ between the biosphere and the atmosphere * Numerous satellite validation projects Wunch, D., et al.: A method for evaluating bias in global measurements of CO2 total columns from space, Atmos. Chem. Phys., 11, 12317-12337, doi:10.5194/acp-11-12317-2011, 2011. * Validation projects involving comparison of CO₂ and CH₄ measured by TCCON with that measured by lower-resolution instruments * Covariation between surface temperature and CO₂ in boreal regions * Distinguishing between which of two power plants (~2000 MW each) plumes of polluted air came from in conjunction with a Pandora NO₂ spectrometerRodica Lindenmaier, Manvendra K. Dubey, Bradley G. Henderson, Zachary T. Butterfield, Jay R. Herman, Thom Rahn, and Sang-Hyun Lee. Multiscale observations of CO2, 13CO2, and pollutants at Four Corners for emission verification and attribution. PNAS 2014 111 (23) 8386-8391; published ahead of print May 19, 2014, doi:10.1073/pnas.1321883111

Satellite support

The satellite missions supported by the TCCON include the Greenhouse Gases Observing Satellite (GOSAT),Crisp, D. et al.: The ACOS XCO2 retrieval algorithm, Part 2: Global XCO2 data characterization, Atmos. Meas. Tech. Discuss., 5, 1-60, , 2012, http://www.atmos-meas-tech-discuss.net/5/1/2012/amtd-5-1-2012.htmlButz, A. et al. (2011), Toward accurate CO2 and CH4 observations from GOSAT, Geophysical Research Letters, 38(14), 2-7, , http://www.agu.org/pubs/crossref/2011/2011GL047888.shtmlMorino, I. et al. (2011), Preliminary validation of column-averaged volume mixing ratios of carbon dioxide and methane retrieved from GOSAT short-wavelength infrared spectra, Atmospheric Measurement Techniques, 4(6), 1061-1076, , http://www.atmos-meas-tech.net/4/1061/2011/ SCIAMACHY,Buchwitz, M. et al. (2006), Atmospheric carbon gases retrieved from SCIAMACHY by WFM-DOAS: version 0.5 CO and CH4 and impact of calibration improvements on CO2 retrieval, Atmospheric Chemistry and Physics, 6(9), 2727-2751, , http://www.atmos-chem-phys.net/6/2727/2006/ and the Orbiting Carbon Observatory-2 (OCO-2).

References

External links

*{{Commons category-inline, TCCON Atmospheric chemistry Carbon dioxide