Accurately quantifying the timing and magnitude of respiration and photosynthesis by high‐latitude ecosystems is important for understanding how a warming climate influences global carbon cycling. ...Data‐driven estimates of photosynthesis across Arctic regions often rely on satellite‐derived enhanced vegetation index (EVI); we find that satellite observations of solar‐induced chlorophyll fluorescence (SIF) provide a more direct proxy for photosynthesis. We model Alaskan tundra CO2 cycling (2012–2014) according to temperature and shortwave radiation and alternately input EVI or SIF to prescribe the annual seasonal cycle of photosynthesis. We find that EVI‐based seasonality indicates spring “green‐up” to occur 9 days prior to SIF‐based estimates, and that SIF‐based estimates agree with aircraft and tower measurements of CO2. Adopting SIF, instead of EVI, for modeling the seasonal cycle of tundra photosynthesis can result in more accurate estimates of growing season duration and net carbon uptake by arctic vegetation.
Key Points
Alaskan tundra has a shorter growing season and less net carbon uptake than estimated using satellite‐derived vegetation indices
Comparisons against site and aircraft CO2 observations indicate that solar‐induced fluorescence (SIF) captures tundra photosynthesis
SIF‐driven modeling of tundra photosynthesis enables improved accuracy and understanding of the carbon‐climate system
The causes of renewed growth in the atmospheric CH4 burden since 2007 are still poorly understood and subject of intensive scientific discussion. We present a reanalysis of global CH4 emissions ...during the 2000s, based on the TM5‐4DVAR inverse modeling system. The model is optimized using high‐accuracy surface observations from NOAA ESRL's global air sampling network for 2000–2010 combined with retrievals of column‐averaged CH4 mole fractions from SCIAMACHY onboard ENVISAT (starting 2003). Using climatological OH fields, derived global total emissions for 2007–2010 are 16–20 Tg CH4/yr higher compared to 2003–2005. Most of the inferred emission increase was located in the tropics (9–14 Tg CH4/yr) and mid‐latitudes of the northern hemisphere (6–8 Tg CH4/yr), while no significant trend was derived for Arctic latitudes. The atmospheric increase can be attributed mainly to increased anthropogenic emissions, but the derived trend is significantly smaller than estimated in the EDGARv4.2 emission inventory. Superimposed on the increasing trend in anthropogenic CH4 emissions are significant inter‐annual variations (IAV) of emissions from wetlands (up to ±10 Tg CH4/yr), and biomass burning (up to ±7 Tg CH4/yr). Sensitivity experiments, which investigated the impact of the SCIAMACHY observations (versus inversions using only surface observations), of the OH fields used, and of a priori emission inventories, resulted in differences in the detailed latitudinal attribution of CH4 emissions, but the IAV and trends aggregated over larger latitude bands were reasonably robust. All sensitivity experiments show similar performance against independent shipboard and airborne observations used for validation, except over Amazonia where satellite retrievals improved agreement with observations in the free troposphere.
Key Points
A reanalysis of global CH4 emissions during the 2000s is presented
derived global total emissions 2007‐2010 16‐20 Tg CH4/yr higher than 2003‐2005
increase mainly in the tropics and NH mid‐latitudes
The column‐average dry air mole fractions of atmospheric carbon dioxide and methane and are inferred from observations of backscattered sunlight conducted by the Greenhouse gases Observing SATellite ...(GOSAT). Comparing the first year of GOSAT retrievals over land with colocated ground‐based observations of the Total Carbon Column Observing Network (TCCON), we find an average difference (bias) of −0.05% and −0.30% for and with a station‐to‐station variability (standard deviation of the bias) of 0.37% and 0.26% among the 6 considered TCCON sites. The root‐mean square deviation of the bias‐corrected satellite retrievals from colocated TCCON observations amounts to 2.8 ppm for and 0.015 ppm for Without any data averaging, the GOSAT records reproduce general source/sink patterns such as the seasonal cycle of suggesting the use of the satellite retrievals for constraining surface fluxes.
Key Points
Improved quality of XCO2 and XCH4 satellite retrievals due to refined methods
Source/sink patterns are dentifiable in the data record without averaging
Constrained surface flux modeling is the logical next step
The performance of electroplating in the removal of chromium ions from crude tannery wastewater and from a synthetic wastewater solution was investigated. Brazil is a major producer of leather, and ...such industries generate large environmental impacts. A novel batch reactor setup was developed for tannery wastewater treatment, employing graphite and aluminum as anode and cathode, respectively. Crude wastewater from a tannery was characterized and presented an acidic pH, elevated biochemical oxygen demand and chemical oxygen demand, and a total chromium concentration of 544 mg/L, a value that is one thousand times higher than permitted by local legislation. Electroplating was able to remove 90.0% of chromium content from a synthetic trivalent chromium solution. Moreover, 96.5% of total chromium content was removed when electroplating was applied in untreated tannery wastewater. Additionally, antifoam addition inhibited foam generation during the electroplating process without interfering in chromium removal. The results showed that the electroplating technique is a viable wastewater treatment alternative and/or a complement for tannery industries that use chromium as a tanning agent.
Chlorophyll fluorescence measurements provide valuable information on phytoplankton abundance and physiology. High spectral resolution measurements from the aircraft‐mounted Portable Remote Imaging ...SpectroMeter (PRISM) allow for a more robust and informative fluorescence measurement than previous methods. An increase in radiation in the fluorescence wavelength range is approximated by a skew‐normal distribution. Positive skew suggests the influence of water attenuation and motivates the use of an inverse retrieval model to solve for the most likely vertical distribution of fluorescence quantum yield. This approach is tested with theoretical fluorescence profiles and applied to a PRISM flightline located in southern Drake Passage, Southern Ocean during austral summer. The resulting profiles suggest vertical structure in fluorescence quantum yield in the upper 10 m, which matches expectations from in situ studies. The framework developed in this paper can be applied to current and future satellite missions, providing more information on phytoplankton concentrations, vertical profiles, and physiology.
Plain Language Summary
When chlorophyll molecules absorb light in the visible wavelengths, part of the energy is released in the form of light (fluorescence) in far‐red and near‐infrared wavelengths. Measurements of this fluorescence provide an independent estimate of the amount of photosynthesis occurring in the water, compared with other methods related to measuring the absorption of light by chlorophyll. Importantly, the theoretical “spectral shape,” or the amount of light released at each wavelength, of fluorescence is well known. Here we report measurements of the spectral shape of fluorescence in the ocean from aircraft measurements. The actual spectral shape is different from theoretical expectations. However, fluorescence emanating from chlorophyll at shallow depths (less than 10 m) is modified by interactions with the water column above it, leading to differences in the spectral shape observed by aircraft. We use an algorithm that finds the vertical profile of fluorescence in the ocean that best matches the observations. This best match corresponds to a subsurface maximum in fluorescence, consistent with common profiles measured in situ.
Key Points
Aircraft‐mounted high spectral resolution spectrometer data allows for a full fluorescence retrieval
Variations in fluorescence shape provide constraints on the vertical distribution of fluorescence quantum yield
Retrieved profiles show features similar to in situ retrievals of fluorescence quantum yield
Emissions estimates of anthropogenic methane (CH4) sources are highly uncertain and many sources related to energy production are localized yet difficult to quantify. Airborne imaging spectrometers ...like the next generation Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-NG) are well suited for locating CH4 point sources due to their ability to map concentrations over large regions with the high spatial resolution necessary to resolve localized emissions. AVIRIS-NG was deployed during a field campaign to measure controlled CH4 releases at the Rocky Mountain Oilfield Testing Center (RMOTC) in Wyoming, U.S. for multiple flux rates and flight altitudes. Two algorithms were applied to AVIRIS-NG scenes, a matched filter detection algorithm and a hybrid retrieval approach using the Iterative Maximum a Posteriori Differential Optical Absorption Spectroscopy (IMAP-DOAS) algorithm and Singular Value Decomposition. Plumes for releases as low as 14.16m3/h (0.09kt/year) were consistently observed by AVIRIS-NG at multiple flight altitudes and images of plumes were in agreement with wind directions measured at ground stations. In some cases plumes as low as 3.40m3/h (0.02kt/year) were detected, indicating that AVIRIS-NG has the capability of detecting a wide range of fugitive CH4 source categories for natural gas fields. This controlled release experiment is the first of its kind using AVIRIS-NG and demonstrates the utility of imaging spectrometers for direct attribution of emissions to individual point source locations. This is particularly useful given the large uncertainties associated with anthropogenic CH4 emissions, including those from industry, gas transmission lines, and the oil and gas sectors.
•AVIRIS-NG detected CH4 plumes for fluxes as low as 3.4m3/h (0.02kt/year).•Plumes observed for flights between 0.43 and 3.80km above ground level.•Plume shape and orientation consistent with observed wind speed and direction•AVIRIS-NG capable of detecting emission sources in existing gas fields
We have analyzed the column-averaged CH4 concentration (xCH4) using scanning imaging absorption spectrometer for atmospheric chartography (SCIAMACHY) and compared the data with the bottom–up emission ...inventory data sets and other satellite-derived indices such as the land-surface water coverage (LSWC) and the normalized difference vegetation index (NDVI). The geographical distribution of high CH4 values corresponds to strong emissions from regions where rice is cultivated, as indicated in the inventory maps. The Pearson's correlation coefficients (r) between xCH4 and the rice emission inventory data are observed to be greater than ~0.6 over typical rice fields, with outstanding r-values of ~0.8 in the Ganges Basin, Myanmar, and Thailand. This suggests that the emission of CH4 from rice cultivation mainly controls the seasonality of the CH4 concentration over such regions. The correlation between xCH4 and LSWC and NDVI is also as large as 0.6. In Southeast Asia, the r-values of xCH4 with bottom–up inventory data that includes all categories are not as high as those with the emission, as estimated from the rice category only. This is indicative of the relative importance of rice emissions among all other emission categories in Southeast Asia.
•SCIAMACHY revealed seasonal variation of CH4 over Monsoon Asia.•The CH4 concentration over Monsoon Asia enhances in wet season.•Enhancement of the methane correlates to the land-surface water coverage.•Strong CH4 emission from rice paddies is suggested in wet season.
Thermal infrared (IR) radiances measured near 8 microns contain information about the vertical distribution of water vapor (H2 O), the water isotopologue HDO, and methane (CH4 ), key gases in the ...water and carbon cycles. Previous versions (Version 4 or less) of the TES profile retrieval algorithm used a "spectral-window" approach to minimize uncertainty from interfering species at the expense of reduced vertical resolution and sensitivity. In this manuscript we document changes to the vertical resolution and uncertainties of the TES version 5 retrieval algorithm. In this version (Version 5), joint estimates of H2 O, HDO, CH4 and nitrous oxide (N2 O) are made using radiances from almost the entire spectral region between 1100 cm-1 and 1330 cm-1 . The TES retrieval constraints are also modified in order to better use this information. The new H2 O estimates show improved vertical resolution in the lower troposphere and boundary layer, while the new HDO/H2 O estimates can now profile the HDO/H2 O ratio between 925 hPa and 450 hPa in the tropics and during summertime at high latitudes. The new retrievals are now sensitive to methane in the free troposphere between 800 and 150 mb with peak sensitivity near 500 hPa; whereas in previous versions the sensitivity peaked at 200 hPa. However, the upper troposphere methane concentrations are biased high relative to the lower troposphere by approximately 4% on average. This bias is likely related to temperature, calibration, and/or methane spectroscopy errors. This bias can be mitigated by normalizing the CH4 estimate by the ratio of the N2 O estimate relative to the N2 O prior, under the assumption that the same systematic error affects both the N2 O and CH4 estimates. We demonstrate that applying this ratio theoretically reduces the CH4 estimate for non-retrieved parameters that jointly affect both the N2 O and CH4 estimates. The relative upper troposphere to lower troposphere bias is approximately 2.8% after this bias correction. Quality flags based upon the vertical variability of the methane and N2 O estimates can be used to reduce this bias further. While these new CH4 , HDO/H2 O, and H2 O estimates are consistent with previous TES retrievals in the altitude regions where the sensitivities overlap, future comparisons with independent profile measurement will be required to characterize the biases of these new retrievals and determine if the calculated uncertainties using the new constraints are consistent with actual uncertainties.
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