Eastern Boundary Upwelling Systems (EBUSs) are coastal hotspots of the potent greenhouse gas nitrous oxide (N2O). However, estimates of their emissions suffer from large uncertainties due to their significant spatial and temporal heterogeneity. Here, we derive the first multiyear, monthly resolution N2O emissions from three of the four major EBUSs using high-frequency coastal atmospheric measurements and an inverse method. We find average combined N2O emissions from the northern California, Benguela, and southern Canary upwelling systems to be 57.7 (51.4–63.9) Gg-N yr−1. We also find an offshore region near the Benguela EBUS that exhibits large pulses of emissions with emissions that reach 677 Gg-N yr−1 in 1 month. Our findings highlight that atmospheric measurements coupled with inverse modeling can capture the large variability in EBUS emissions by quantifying emissions over large spatial distances and over long time periods compared to previous methods using traditional oceanographic measurements.

We estimated the CH4 budget in Finland for 2004–2014 using the CTE-CH4 data assimilation system with an extended atmospheric CH4 observation network of seven sites from Finland to surrounding regions (Hyytiälä, Kjølnes, Kumpula, Pallas, Puijo, Sodankylä, and Utö). The estimated average annual total emission for Finland is 0.6 ± 0.5 Tg CH4 yr−1. Sensitivity experiments show that the posterior biospheric emission estimates for Finland are between 0.3 and 0.9 Tg CH4 yr−1, which lies between the LPX-Bern-DYPTOP (0.2 Tg CH4 yr−1) and LPJG-WHyMe (2.2 Tg CH4 yr−1) process-based model estimates. For anthropogenic emissions, we found that the EDGAR v4.2 FT2010 inventory (0.4 Tg CH4 yr−1) is likely to overestimate emissions in southernmost Finland, but the extent of overestimation and possible relocation of emissions are difficult to derive from the current observation network. The posterior emission estimates were especially reliant on prior information in central Finland. However, based on analysis of posterior atmospheric CH4, we found that the anthropogenic emission distribution based on a national inventory is more reliable than the one based on EDGAR v4.2 FT2010. The contribution of total emissions in Finland to global total emissions is only about 0.13%, and the derived total emissions in Finland showed no trend during 2004–2014. The model using optimized emissions was able to reproduce observed atmospheric CH4 at the sites in Finland and surrounding regions fairly well (correlation >0.75, bias (Formula presented.) ppb), supporting adequacy of the observations to be used in atmospheric inversion studies. In addition to global budget estimates, we found that CTE-CH4 is also applicable for regional budget estimates, where small scale (1º × 1º in this case) optimization is possible with a dense observation network.

Until recently, atmospheric carbon dioxide (CO2) and methane (CH4) measurements were made almost exclusively using nondispersive infrared (NDIR) absorption and gas chromatography with flame ionisation detection (GC/FID) techniques, respectively. Recently, commercially available instruments based on spectroscopic techniques such as cavity ring-down spectroscopy (CRDS), off-axis integrated cavity output spectroscopy (OA-ICOS) and Fourier transform infrared (FTIR) spectroscopy have become more widely available and affordable. This resulted in a widespread use of these techniques at many measurement stations. This paper is focused on the comparison between a CRDS "travelling instrument" that has been used during performance audits within the Global Atmosphere Watch (GAW) programme of the World Meteorological Organization (WMO) with instruments incorporating other, more traditional techniques for measuring CO2 and CH4 (NDIR and GC/FID). We demonstrate that CRDS instruments and likely other spectroscopic techniques are suitable for WMO/GAW stations and allow a smooth continuation of historic CO2 and CH4 time series. Moreover, the analysis of the audit results indicates that the spectroscopic techniques have a number of advantages over the traditional methods which will lead to the improved accuracy of atmospheric CO2 and CH4 measurements.

In recent years several commercialised closed-path cavity-based spectroscopic instruments designed for eddy covariance flux measurements of carbon dioxide (CO2), methane (CH4), and water vapour (H2O) have become available. Here we compare the performance of two leading models - the Picarro G2311-f and the Los Gatos Research (LGR) Fast Greenhouse Gas Analyzer (FGGA) at a coastal site. Both instruments can compute dry mixing ratios of CO2 and CH4 based on concurrently measured H2O, temperature, and pressure. Additionally, we used a high throughput Nafion dryer to physically remove H2O from the Picarro airstream. Observed air-sea CO2 and CH4 fluxes from these two analysers, averaging about 12 and 0.12 mmol m-2 day-1 respectively, agree within the measurement uncertainties. For the purpose of quantifying dry CO2 and CH4 fluxes downstream of a long inlet, the numerical H2O corrections appear to be reasonably effective and lead to results that are comparable to physical removal of H2O with a Nafion dryer in the mean. We estimate the high-frequency attenuation of fluxes in our closed-path set-up, which was relatively small (≤ 10 %) for CO2 and CH4 but very large for the more polar H2O. The Picarro showed significantly lower noise and flux detection limits than the LGR. The hourly flux detection limit for the Picarro was about 2 mmol m-2 day-1 for CO2 and 0.02 mmol m-2 day-1 for CH4. For the LGR these detection limits were about 8 and 0.05 mmol m-2 day-1. Using global maps of monthly mean air-sea CO2 flux as reference, we estimate that the Picarro and LGR can resolve hourly CO2 fluxes from roughly 40 and 4 % of the world's oceans respectively. Averaging over longer timescales would be required in regions with smaller fluxes. Hourly flux detection limits of CH4 from both instruments are generally higher than the expected emissions from the open ocean, though the signal to noise of this measurement may improve closer to the coast.

Measurements of formaldehyde (HCHO) were made at the Cape Verde Atmospheric Observatory between November 2006 and June 2007 using the Long-Path Differential Optical Absorption Spectroscopy (LP-DOAS) technique. Observations show that typical HCHO mixing ratios ranged between 350 and 550 pptv (with typical 2-σ uncertainties of ∼110 pptv), with several events of high HCHO, the maximum being 1, 885± 149 pptv. The observations indicate a lack of strong seasonal or diurnal variations, within the uncertainty of the measurements. A box model is employed to test whether the observations can be explained using known hydrocarbon photochemistry; the model replicates well the typical diurnal profile and monthly mean values. The model results indicate that on average 20% of HO2 production and 10% of OH destruction can be attributed to the mean HCHO levels, suggesting that even at these low average mixing ratios HCHO plays an important role in determining the HOx (HO2+OH) balance of the remote marine boundary layer. © Springer Science+Business Media B.V. 2011.

We present an integrated system for measuring atmospheric concentrations of CO2, O2, CH4, CO, and N2O in central Siberia. Our project aims to demonstrate the feasibility of establishing long-term, continuous, high precision atmospheric measurements to elucidate greenhouse gas processes from a very remote, mid-continental boreal environment. Air is sampled from five heights on a custom-built 300-m tower. Common features to all species' measurements include air intakes, an air drying system, flushing procedures, and data processing methods. Calibration standards are shared among all five measured species by extending and optimising a proven methodology for long-term O2 calibration. Our system achieves the precision and accuracy requirements specified by the European Union's "CarboEurope" and "ICOS" (Integrated Carbon Observing System) programmes in the case of CO2, O2, and CH 4, while CO and N2O require some further improvements. It was found that it is not possible to achieve these high precision measurements without skilled technical assistance on-site, primarily because of 2-3 month delays in access to data and diagnostic information. We present results on the stability of reference standards in high pressure cylinders. It was also found that some previous methods do not mitigate fractionation of O2 in a sample airstream to a satisfactory level.

We present first results from 19 months of semicontinuous concentration measurements of biogeochemical trace gases (CO2, CO, and CH 4) and O2, measured at the Zotino Tall Tower Observatory (ZOTTO) in the boreal forest of central Siberia. We estimated CO2 and O2 seasonal cycle amplitudes of 26.6 ppm and 134 per meg, respectively. An observed west-east gradient of about -7 ppm (in July 2006) between Shetland Islands, Scotland, and ZOTTO reflects summertime continental uptake of CO2 and is consistent with regional modeling studies. We found the oceanic component of the O2 seasonal amplitude (Atmospheric Potential Oxygen, or APO) to be 51 per meg, significantly smaller than the 95 per meg observed at Shetlands, illustrating a strong attenuation of the oceanic O2 signal in the continental interior. Comparison with the Tracer Model 3 (TM3) atmospheric transport model showed good agreement with the observed phasing and seasonal amplitude in CO2; however, the model exhibited greater O2 (43 per meg, 32%) and smaller APO (9 per meg, 18%) amplitudes. This seeming inconsistency in model comparisons between O 2 and APO appears to be the result of phasing differences in land and ocean signals observed at ZOTTO, where ocean signals have a significant lag. In the first 2 months of measurements on the fully constructed tower (November and December 2006), we observed several events with clear vertical concentration gradients in all measured species except CO. During "cold events" (below -30°C) in November 2006, we observed large vertical gradients in CO2 (up to 22 ppm), suggesting a strong local source. The same pattern was observed in CH4 concentrations for the same events. Diurnal vertical CO2 gradients in April to May 2007 gave estimates for average nighttime respiration fluxes of 0.04 ± 0.02 mol C m -2 d-1, consistent with earlier eddy covariance measurements in 1999-2000 in the vicinity of the tower. Copyright 2008 by the American Geophysical Union.