The Experts below are selected from a list of 112062 Experts worldwide ranked by ideXlab platform
Colm Sweeney - One of the best experts on this subject based on the ideXlab platform.
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frequency comb based remote sensing of Greenhouse Gases over kilometer air paths
Optica, 2014Co-Authors: Gregory B Rieker, Fabrizio R Giorgetta, William C Swann, J Kofler, Alexander M Zolot, Laura C Sinclair, Esther Baumann, Christopher L Cromer, G Petron, Colm SweeneyAbstract:Increasing our understanding of regional Greenhouse gas transport, sources, and sinks requires accurate, precise, continuous measurements of small gas enhancements over long ranges. We demonstrate a coherent dual frequency-comb spectroscopy technique capable of achieving these goals. Spectra are acquired spanning 5990 to 6260 cm−1 (1600–1670 nm) covering ∼700 absorption features from CO2, CH4, H2O, HDO, and CO213, across a 2 km path. The spectra have sub-1-kHz frequency accuracy, no instrument lineshape, and a 0.0033 cm−1 point spacing. They are fit with different absorption models to yield dry-air mole fractions of Greenhouse Gases. These results are compared with a point sensor under well-mixed conditions to evaluate the accuracy of models critical to global satellite-based trace gas monitoring. Under heterogeneous conditions, time-resolved data demonstrate tracking of small variations in mole fractions, with a precision <1 ppm for CO2 and <3 ppb for CH4 in 5 min. Portable systems could enable regional monitoring.
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frequency comb based remote sensing of Greenhouse Gases over kilometer air paths
arXiv: Optics, 2014Co-Authors: Gregory B Rieker, Fabrizio R Giorgetta, William C Swann, J Kofler, Alexander M Zolot, Laura C Sinclair, Esther Baumann, Christopher L Cromer, G Petron, Colm SweeneyAbstract:We demonstrate coherent dual frequency-comb spectroscopy for detecting variations in Greenhouse Gases. High signal-to-noise spectra are acquired spanning 5990 to 6260 cm^-1 (1600 to 1670 nm) covering ~700 absorption features from CO2, CH4, H2O, HDO, and 13CO2, across a 2-km open-air path. The transmission of each frequency comb tooth is resolved, leading to spectra with <1 kHz frequency accuracy, no instrument lineshape, and a 0.0033-cm^-1 point spacing. The fitted path-averaged concentrations and temperature yield dry-air mole fractions. These are compared with a point sensor under well-mixed conditions to evaluate current absorption models for real atmospheres. In heterogeneous conditions, time-resolved data demonstrate tracking of strong variations in mole fractions. A precision of <1 ppm for CO2 and <3 ppb for CH4 is achieved in 5 minutes in this initial demonstration. Future portable systems could support regional emissions monitoring and validation of the spectral databases critical to global satellite-based trace gas monitoring.
Mitch Goldberg - One of the best experts on this subject based on the ideXlab platform.
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airs improving weather forecasting and providing new data on Greenhouse Gases
Bulletin of the American Meteorological Society, 2006Co-Authors: Moustafa T Chahine, Eric J Fetzer, Hartmut H Aumann, Thomas S Pagano, Christopher D Barnet, John Blaisdell, Luke Chen, Murty Divakarla, Mitch GoldbergAbstract:Abstract The Atmospheric Infrared Sounder (AIRS) and its two companion microwave sounders, AMSU and HSB were launched into polar orbit onboard the NASA Aqua Satellite in May 2002. NASA required the sounding system to provide high-quality research data for climate studies and to meet NOAA's requirements for improving operational weather forecasting. The NOAA requirement translated into global retrieval of temperature and humidity profiles with accuracies approaching those of radiosondes. AIRS also provides new measurements of several Greenhouse Gases, such as CO2, CO, CH4, O3, SO2, and aerosols. The assimilation of AIRS data into operational weather forecasting has already demonstrated significant improvements in global forecast skill. At NOAA/NCEP, the improvement in the forecast skill achieved at 6 days is equivalent to gaining an extension of forecast capability of six hours. This improvement is quite significant when compared to other forecast improvements over the last decade. In addition to NCEP, ECM...
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airs improving weather forecasting and providing new data on Greenhouse Gases
Bulletin of the American Meteorological Society, 2006Co-Authors: Moustafa T Chahine, Eric J Fetzer, Hartmut H Aumann, Thomas S Pagano, Christopher D Barnet, John Blaisdell, Luke Chen, Murty Divakarla, Mitch GoldbergAbstract:SUMMARY AND CONCLUSIONS. The AIRS instrument has met its primary scientific objective to improve weather prediction and to retrieve tem-perature and precipitable water vapor profiles with accuracies approaching those of radiosondes. AIRS also has provided new information on the concen-tration of tropospheric mi-nor constituents, includ-ing several Greenhouse Gases essential for climate studies.The foundation of all AIRS data products is the physical retrieval algorithm (PRA) that is being main-tained and continuously upgraded by the AIRS Sci-ence Team. The results described in this paper are “work in progress,” and al-though significant accom-plishments have already been made, much more work remains in order to realize the full potential of this instrument. The AIRS Science Team is currently pursuing improvements to the retrieval algorithm, in particular 1) determina-tion of land surface emissivity, 2) modification of the radiative transfer algorithm (RTA) to account for nonlocal thermodynamic equilibrium (NLTE) effects on the shortwave channels, 3) development of a cloud-clearing algorithm based on AIRS spectra only, and 4) incorporation of variable atmospheric CO
J H Butler - One of the best experts on this subject based on the ideXlab platform.
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Non-CO2 Greenhouse Gases and climate change
Nature, 2011Co-Authors: Stephen A. Montzka, Edward J. Dlugokencky, J H ButlerAbstract:The influence of anthropogenic carbon dioxide emissions on climate is widely recognized, but there are plenty of Greenhouse Gases besides CO2 and they receive much less attention. In this Review, Stephen Montzka and co-authors summarize the current knowledge on non-CO2 Greenhouse Gases, including methane, nitrous oxide and halogenic compounds such as chlorofluorocarbons. Although the total warming effect of these Gases is less than that of CO2, a substantial reduction in their emissions would measurably reduce the impact of human activity on our climate. And as non-CO2 Greenhouse Gases tend to have a shorter atmospheric lifetime than CO2, the response of the climate system to emissions cuts in the former would be faster than the response through cuts in CO2 alone. Earth’s climate is warming as a result of anthropogenic emissions of Greenhouse Gases, particularly carbon dioxide (CO2) from fossil fuel combustion. Anthropogenic emissions of non-CO2 Greenhouse Gases, such as methane, nitrous oxide and ozone-depleting substances (largely from sources other than fossil fuels), also contribute significantly to warming. Some non-CO2 Greenhouse Gases have much shorter lifetimes than CO2, so reducing their emissions offers an additional opportunity to lessen future climate change. Although it is clear that sustainably reducing the warming influence of Greenhouse Gases will be possible only with substantial cuts in emissions of CO2, reducing non-CO2 Greenhouse gas emissions would be a relatively quick way of contributing to this goal.
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Non-CO2 Greenhouse Gases and climate change
Nature, 2011Co-Authors: Stephen A. Montzka, Edward J. Dlugokencky, J H ButlerAbstract:Earth's climate is warming as a result of anthropogenic emissions of Greenhouse Gases, particularly carbon dioxide (CO(2)) from fossil fuel combustion. Anthropogenic emissions of non-CO(2) Greenhouse Gases, such as methane, nitrous oxide and ozone-depleting substances (largely from sources other than fossil fuels), also contribute significantly to warming. Some non-CO(2) Greenhouse Gases have much shorter lifetimes than CO(2), so reducing their emissions offers an additional opportunity to lessen future climate change. Although it is clear that sustainably reducing the warming influence of Greenhouse Gases will be possible only with substantial cuts in emissions of CO(2), reducing non-CO(2) Greenhouse gas emissions would be a relatively quick way of contributing to this goal.
Gregory B Rieker - One of the best experts on this subject based on the ideXlab platform.
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frequency comb based remote sensing of Greenhouse Gases over kilometer air paths
Optica, 2014Co-Authors: Gregory B Rieker, Fabrizio R Giorgetta, William C Swann, J Kofler, Alexander M Zolot, Laura C Sinclair, Esther Baumann, Christopher L Cromer, G Petron, Colm SweeneyAbstract:Increasing our understanding of regional Greenhouse gas transport, sources, and sinks requires accurate, precise, continuous measurements of small gas enhancements over long ranges. We demonstrate a coherent dual frequency-comb spectroscopy technique capable of achieving these goals. Spectra are acquired spanning 5990 to 6260 cm−1 (1600–1670 nm) covering ∼700 absorption features from CO2, CH4, H2O, HDO, and CO213, across a 2 km path. The spectra have sub-1-kHz frequency accuracy, no instrument lineshape, and a 0.0033 cm−1 point spacing. They are fit with different absorption models to yield dry-air mole fractions of Greenhouse Gases. These results are compared with a point sensor under well-mixed conditions to evaluate the accuracy of models critical to global satellite-based trace gas monitoring. Under heterogeneous conditions, time-resolved data demonstrate tracking of small variations in mole fractions, with a precision <1 ppm for CO2 and <3 ppb for CH4 in 5 min. Portable systems could enable regional monitoring.
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frequency comb based remote sensing of Greenhouse Gases over kilometer air paths
arXiv: Optics, 2014Co-Authors: Gregory B Rieker, Fabrizio R Giorgetta, William C Swann, J Kofler, Alexander M Zolot, Laura C Sinclair, Esther Baumann, Christopher L Cromer, G Petron, Colm SweeneyAbstract:We demonstrate coherent dual frequency-comb spectroscopy for detecting variations in Greenhouse Gases. High signal-to-noise spectra are acquired spanning 5990 to 6260 cm^-1 (1600 to 1670 nm) covering ~700 absorption features from CO2, CH4, H2O, HDO, and 13CO2, across a 2-km open-air path. The transmission of each frequency comb tooth is resolved, leading to spectra with <1 kHz frequency accuracy, no instrument lineshape, and a 0.0033-cm^-1 point spacing. The fitted path-averaged concentrations and temperature yield dry-air mole fractions. These are compared with a point sensor under well-mixed conditions to evaluate current absorption models for real atmospheres. In heterogeneous conditions, time-resolved data demonstrate tracking of strong variations in mole fractions. A precision of <1 ppm for CO2 and <3 ppb for CH4 is achieved in 5 minutes in this initial demonstration. Future portable systems could support regional emissions monitoring and validation of the spectral databases critical to global satellite-based trace gas monitoring.
Keith P. Shine - One of the best experts on this subject based on the ideXlab platform.
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alternatives to the global warming potential for comparing climate impacts of emissions of Greenhouse Gases
Climatic Change, 2005Co-Authors: Keith P. Shine, Jan S Fuglestvedt, Kinfe Hailemariam, N StuberAbstract:The Global Warming Potential (GWP) is used within the Kyoto Protocol to the United Nations Framework Convention on Climate Change as a metric for weighting the climatic impact of emissions of different Greenhouse Gases. The GWP has been subjected to many criticisms because of its formulation, but nevertheless it has retained some favour because of the simplicity of its design and application, and its transparency compared to proposed alternatives. Here, two new metrics are proposed, which are based on a simple analytical climate model. The first metric is called the Global Temperature Change Potential and represents the temperature change at a given time due to a pulse emission of a gas (GTPP); the second is similar but represents the effect of a sustainedemission change (hence GTPS). Both GTPP and GTPS are presented as relative to the temperature change due to a similar emission change of a reference gas, here taken to be carbon dioxide. Both metrics are compared against an upwelling-diffusion energy balance model that resolves land and ocean and the hemispheres. The GTPP does not perform well, compared to the energy balance model, except for long-lived Gases. By contrast, the GTPS is shown to perform well relative to the energy balance model, for Gases with a wide variety of lifetimes. It is also shown that for time horizons in excess of about 100 years, the GTPS and GWP produce very similar results, indicating an alternative interpretation for the GWP. The GTPS retains the advantage of the GWP in terms of transparency, and the relatively small number of input parameters required for calculation. However, it has an enhanced relevance, as it is further down the cause–effect chain of the impacts of Greenhouse Gases emissions and has an unambiguous interpretation. It appears to be robust to key uncertainties and simplifications in its derivation and may be an attractive alternative to the GWP.
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new estimates of radiative forcing due to well mixed Greenhouse Gases
Geophysical Research Letters, 1998Co-Authors: Gunnar Myhre, Keith P. Shine, E J Highwood, Frode StordalAbstract:We have performed new calculations of the radiative forcing due to changes in the concentrations of the most important well mixed Greenhouse Gases (WMGG) since pre-industrial time. Three radiative transfer models are used. The radiative forcing due to CO2, including shortwave absorption, is 15% lower than the previous IPCC estimate. The radiative forcing due to all the WMGG is calculated to 2.25 Wm−2, which we estimate to be accurate to within about 5%. The importance of the CFCs is increased by about 20% relative to the total effect of all WMGG compared to previous estimates. We present updates to simple forcing-concentration relationships previously used by IPCC.
