Impacts of updated spectroscopy on thermal infrared retrievals of methane evaluated with HIPPO data

Alvarado, M. J.; Payne, Vivienne H.; Cady‐Pereira, Karen; Hegarty, J. D.; Kulawik, S. S.; Wecht, K.; Worden, J.; Pittman, J. V.; Wofsy, Steven C.

doi:10.5194/amt-8-965-2015

Cited by 20 publications

(17 citation statements)

References 64 publications

(80 reference statements)

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“…The dif- ferences are most pronounced in the troposphere at the lower boundary of the data product, where new spectroscopic data lead to values of up to 0.18 ppmv lower than the old ones. These findings agree with Alvarado et al (2015) who examined the influence of the HITRAN 2008 spectroscopy on the CH 4 profiles retrieved from the NASA AURA Tropospheric Emission Spectrometer (TES, Beer et al, 2001) and found the values to be lower with the new data set. The N 2 O profiles with the HITRAN 2008 spectroscopy show smaller values up to almost 35 km.…”

Section: Usage Of Hitran 2008supporting

confidence: 80%

Methane and nitrous oxide retrievals from MIPAS-ENVISAT

et al. 2015

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Abstract. We present the strongly revised IMK/IAA MIPAS-ENVISAT CH 4 and N 2 O data products for the MIPAS full-resolution (versions V5H_CH4_21 and V5H_N2O_21) and for the reduced-resolution period (versions V5R_CH4_224, V5R_CH4_225, V5R_N2O_224 and V5R_N2O_225). These data sets cover both MIPAS measurement periods from June 2002 until March 2004 and from January 2005 to April 2012. Differences with older retrieval versions which are known to have a high bias are discussed. The usage of the HITRAN 2008 spectroscopic data set leads to lower values for both gases in the lower part of the profile. The improved correction of additive radiance offsets and handling of background radiance continua allows for aerosol contributions at altitudes in the upper stratosphere and above. These changes lead to more plausible values, both in the radiance offset and in the profiles of the continuum absorption coefficients. They also increase the fraction of converged retrievals. Some minor changes were applied to the constraint of the inverse problem, causing small differences in the retrieved profiles, mostly due to the relaxation of off-diagonal regularisation matrix elements for the calculation of jointly retrieved absorption coefficient profiles. Spectral microwindows have been adjusted to avoid areas with saturated spectral signatures. Jointly retrieving profiles of water vapour and nitric acid serves to compensate spectroscopic inconsistencies. We discuss the averaging kernels of the profiles and their vertical resolution. The latter ranges from 2.5 to 7 km for CH 4 , and from 2.5 to 6 km for N 2 O in the reducedresolution period. For the full-resolution period, the vertical resolution is in the order of 3 to 6 km for both gases. We find the retrieval errors in the lower part of the profiles mostly to be around 15 % for CH 4 and below 10 % for N 2 O. The errors above 25 or 30 km increase to values between 10 and 20 %, except for CH 4 from the reduced-resolution period, where the estimated errors stay below 15 %.

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Section: Usage Of Hitran 2008supporting

confidence: 80%

Methane and nitrous oxide retrievals from MIPAS-ENVISAT

et al. 2015

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“…We therefore estimate that the accuracy is approximately 6 ppb for these measurements after the bias of 65 ppb is removed. This result is consistent in sign but not quite the magnitude with the positive bias in TES that is approximately 28 ± 5 ppb (Alvarado et al, 2015; note that the Alvarado et al, 2015, paper computes the RMS of TES minus aircraft data which is about 30 ppb, whereas the error on the mean is the error of the bias and is approximately 5 ppb) and the negative bias in GOSAT that is approximately −17 ± 0.2 ppb for the GOSAT proxy retrievals (e.g. Schepers et al, 2012).…”

Section: Comparison Of Surface Data To Geos-chem and Gosat/tessupporting

confidence: 71%

Quantifying lower tropospheric methane concentrations using GOSAT near-IR and TES thermal IR measurements

et al. 2015

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Abstract. Evaluating surface fluxes of CH 4 using total column data requires models to accurately account for the transport and chemistry of methane in the free troposphere and stratosphere, thus reducing sensitivity to the underlying fluxes. Vertical profiles of methane have increased sensitivity to surface fluxes because lower tropospheric methane is more sensitive to surface fluxes than a total column, and quantifying free-tropospheric CH 4 concentrations helps to evaluate the impact of transport and chemistry uncertainties on estimated surface fluxes. Here we demonstrate the potential for estimating lower tropospheric CH 4 concentrations through the combination of free-tropospheric methane measurements from the Aura Tropospheric Emission Spectrometer (TES) and XCH 4 (dry-mole air fraction of methane) from the Greenhouse gases Observing SATellite -Thermal And Near-infrared for carbon Observation (GOSAT TANSO, herein GOSAT for brevity). The calculated precision of these estimates ranges from 10 to 30 ppb for a monthly average on a 4 • × 5 • latitude/longitude grid making these data suitable for evaluating lower-tropospheric methane concentrations. Smoothing error is approximately 10 ppb or less. Comparisons between these data and the GEOS-Chem model demonstrate that these lower-tropospheric CH 4 estimates can resolve enhanced concentrations over flux regions that are challenging to resolve with total column measurements. We also use the GEOS-Chem model and surface measurements in background regions across a range of latitudes to determine that these lower-tropospheric estimates are biased low by approximately 65 ppb, with an accuracy of approximately 6 ppb (after removal of the bias) and an actual precision of approximately 30 ppb. This 6 ppb accuracy is consistent with the accuracy of TES and GOSAT methane retrievals.

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“…3) and aircraft vertical profiles provide the best resource for direct validation. and Alvarado et al (2015) evaluated successive versions of TES methane retrievals with data from the HIPPO pole-to-pole aircraft campaigns over the Pacific (Wofsy, 2011). Alvarado et al (2015) report that the latest Version 6 of the TES product has a bias of 4.8 ppb.…”

Section: Error Characterizationmentioning

confidence: 99%

“…and Alvarado et al (2015) evaluated successive versions of TES methane retrievals with data from the HIPPO pole-to-pole aircraft campaigns over the Pacific (Wofsy, 2011). Alvarado et al (2015) report that the latest Version 6 of the TES product has a bias of 4.8 ppb. Crevoisier et al (2013) find that IASI observations are consistent with aircraft observations to within 5 ppb.…”

Section: Error Characterizationmentioning

confidence: 99%

Satellite observations of atmospheric methane and their value for quantifying methane emissions

et al. 2016

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Abstract. Methane is a greenhouse gas emitted by a range of natural and anthropogenic sources. Atmospheric methane has been measured continuously from space since 2003, and new instruments are planned for launch in the near future that will greatly expand the capabilities of space-based observations. We review the value of current, future, and proposed satellite observations to better quantify and understand methane emissions through inverse analyses, from the global scale down to the scale of point sources and in combination with suborbital (surface and aircraft) data. Current global observations from Greenhouse Gases Observing Satellite (GOSAT) are of high quality but have sparse spatial coverage. They can quantify methane emissions on a regional scale (100-1000 km) through multiyear averaging. The Tropospheric Monitoring Instrument (TROPOMI), to be launched in 2017, is expected to quantify daily emissions on the regional scale and will also effectively detect large point sources. A different observing strategy by GHGSat (launched in June 2016) is to target limited viewing domains with very fine pixel resolution in order to detect a wide range of methane point sources. Geostationary observation of methane, still in the proposal stage, will have the unique capability of mapping source regions with high resolution, detecting transient "super-emitter" point sources and resolving diurnal variation of emissions from sources such as wetlands and manure. Exploiting these rapidly expanding satellite measurement capabilities to quantify methane emissions requires a parallel effort to construct high-quality spatially and sectorally resolved emission inventories. Partnership between top-down inverse analyses of atmospheric data and bottom-up construction of emission inventories is crucial to better understanding methane emission processes and subsequently informing climate policy.

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Impacts of updated spectroscopy on thermal infrared retrievals of methane evaluated with HIPPO data

Cited by 20 publications

References 64 publications

Methane and nitrous oxide retrievals from MIPAS-ENVISAT

Methane and nitrous oxide retrievals from MIPAS-ENVISAT

Quantifying lower tropospheric methane concentrations using GOSAT near-IR and TES thermal IR measurements

Satellite observations of atmospheric methane and their value for quantifying methane emissions

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