Airborne MAX-DOAS Measurements Over California: Testing the NASA OMI Tropospheric NO2 Product

Airborne Multi-AXis Differential Optical Absorption Spectroscopy (AMAX-DOAS) measurements of NO2 tropospheric vertical columns were performed over California for two months in summer 2010. The observations are compared to the NASA Ozone Monitoring Instrument (OMI) tropospheric vertical columns (data product v2.1) in two ways: (1) Median data were compared for the whole time period for selected boxes, and the agreement was found to be fair (R = 0.97, slope = 1.4 +/- 0.1, N= 10). (2) A comparison was performed on the mean of coincident AMAX-DOAS measurements within the area of the corresponding OMI pixels with the tropospheric NASA OMI NO2 assigned to that pixel. The effects of different data filters were assessed. Excellent agreement and a strong correlation (R = 0.85, slope = 1.05 +/- 0.09, N= 56) was found for (2) when the data were filtered to eliminate large pixels near the edge of the OMI orbit, the cloud radiance fraction was2 km, and a representative sample of the footprint was taken by the AMAX-DOAS instrument. The AMAX-DOAS and OMI data sets both show a reduction of NO2 tropospheric columns on weekends by 38 +/- 24% and 33 +/- 11%, respectively. The assumptions in the tropospheric satellite air mass factor simulations were tested using independent measurements of surface albedo, aerosol extinction, and NO2 profiles for Los Angeles for July 2010 indicating an uncertainty of 12%

Combining Active and Passive Airborne Remote Sensing to Quantify NO2 and Ox Production near Bakersfield, CA

Aims: The objective of this study is to demonstrate the integrated use of passive and active remote sensing instruments to quantify the rate of NOx emissions, and investigate the Ox production rates from an urban area.Place and Duration of Study: A research flight on June 15, 2010 was conducted over Bakersfield, CA and nearby areas with oil and natural gas production. Methodology: Three remote sensing instruments, namely the University of Colorado AMAX-DOAS, NOAA TOPAZ lidar, and NCAS Doppler lidar were deployed aboard the NOAA Twin Otter during summer 2010. Production rates of nitrogen dioxide (NO2) and Ox&lsquo;(background corrected O3 + NO2) were quantified using the horizontal flux divergence approach by flying closed loops near Bakersfield, CA. By making concurrent measurements of the trace gases as well as the wind fields, we have reduced the uncertainty due to wind field in production rates.Results: We find that the entire region is a source for both NO2 and Ox&rsquo;. NO2 production is highest over the city (1.35 kg hr-1 km-2 NO2), and about 30 times lower at background sites (0.04 kg hr-1 km-2 NO2). NOx emissions as represented in the CARB 2010 emission inventory agreewell with our measurements over Bakersfield city (within 30%). However, emissions upwind of the city are significantly underestimated. The Ox&rsquo; production is less variable, found ubiquitous, and accounts for 7.4 kg hr-1 km-2 Ox&rsquo; at background sites. Interestingly, the maximum of 17.1 kg hr-1 km-2 Ox&rsquo;production was observed upwind of the city. A plausible explanation for the efficient Ox&rsquo; production upwind of Bakersfield, CA are favorable volatile organic compound (VOC) to NOx ratios for Ox&rsquo; production, that are affected by emissions from large oil and natural gas operations in that area. Conclusion: The NO2 and O3 source fluxes vary significantly, and allow us to separate and map NOx emissions and Ox production rates in the Central Valley. The data is probed over spatial scales that link closely with those predicted by atmospheric models, and provide innovative means to test and improve atmospheric models that are used to manage air resources. Emissions from oil and natural gas operations are a source for O3 air pollution, and deserve further study to better characterize effects on public health.</p

Corrigendum to "Overview: oxidant and particle photochemical processes above a south-east Asian tropical rainforest (the OP3 project): introduction, rationale, location characteristics and tools" published in Atmos. Chem. Phys., 10, 169–199, 2010

Author(s): Hewitt, CN; Lee, JD; MacKenzie, AR; Barkley, MP; Carslaw, N; Carver, GD; Chappell, NA; Coe, H; Collier, C; Commane, R; Davies, F; Davison, B; DiCarlo, P; Di Marco, CF; Dorsey, JR; Edwards, PM; Evans, MJ; Fowler, D; Furneaux, KL; Gallagher, M; Guenther, A; Heard, DE; Helfter, C; Hopkins, J; Ingham, T; Irwin, M; Jones, C; Karunaharan, A; Langford, B; Lewis, AC; Lim, SF; MacDonald, SM; Mahajan, AS; Malpass, S; McFiggans, G; Mills, G; Misztal, P; Moller, S; Monks, PS; Nemitz, E; Nicolas-Perea, V; Oetjen, H; Oram, DE; Palmer, PI; Phillips, GJ; Pike, R; Plane, JMC; Pugh, T; Pyle, JA; Reeves, CE; Robinson, NH; Stewart, D; Stone, D; Whalley, LK; Yang,

Messungen von Halogenoxiden mit differentieller optischer Absorptionsspektroskopie von gestreutem Sonnenlicht

This work describes measurements of the tropospheric halogen species iodine monoxide (IO) and bromine monoxide (BrO) with multi-axis differential optical absorption spectroscopy (MAX-DOAS) at various locations: Svalbard (79 deg N), Andoya (69 deg N), List (55 deg N), Crete (35 deg N), and Maldives (5 deg N). Furthermore, the radiative transfer model SCIATRAN was used to investigate the sensitivity of the MAX-DOAS technique towards tropospheric absorbers as well as to estimate concentrations of IO and upper limits only for BrO. IO was detected at Svalbard, List, and Maldives with concentrations of 0.4 ppt, 2.2 ppt, and 2.8 ppt, respectively, but was below the average detection limits of 0.6 ppt and 1.3 ppt for Andoya and Crete, respectively. Uncertainties are estimated to be in the range of 2-3 ppt. These concentrations are averaged horizontally as well as vertically assuming a well-mixed surface layer of 500 m thickness or in the case of Svalbard and List 200 m. On a local scale, higher concentrations can occur. Tropospheric BrO could not be measured at any location outside the polar spring. Minimum detection limits for BrO were 2.2 ppt. Ground-based zenith-sky DOAS measurements of stratospheric chlorine dioxide have been performed at the Arctic sites Svalbard and Summit (73 deg N) as well as at the mid-latitudinal site Bremen (53 deg N) and used to validate SCIAMACHY OClO data for the exceptionally cold stratospheric spring 2005. OClO was also derived with a chemical stacked box model. The agreement of all three data sets is excellent for the time of overpass of the satellite instrument, i.e. 10 AM. However, the ground-based measurements could not be reproduced with the model simulations for large solar zenith angles as well as for large concentrations. Sensitivity studies have been performed with the chemistry model and this exercise demonstrated that the measured OClO columns cannot be explained within the known uncertainties of the model parameters including the involved photochemical data

Measurements of halogen oxides by scattered sunlight differential optical absorption spectroscopy

This work describes measurements of the tropospheric halogen species iodine monoxide (IO) and bromine monoxide (BrO) with multi-axis differential optical absorption spectroscopy (MAX-DOAS) at various locations: Svalbard (79 deg N), Andoya (69 deg N), List (55 deg N), Crete (35 deg N), and Maldives (5 deg N). Furthermore, the radiative transfer model SCIATRAN was used to investigate the sensitivity of the MAX-DOAS technique towards tropospheric absorbers as well as to estimate concentrations of IO and upper limits only for BrO. IO was detected at Svalbard, List, and Maldives with concentrations of 0.4 ppt, 2.2 ppt, and 2.8 ppt, respectively, but was below the average detection limits of 0.6 ppt and 1.3 ppt for Andoya and Crete, respectively. Uncertainties are estimated to be in the range of 2-3 ppt. These concentrations are averaged horizontally as well as vertically assuming a well-mixed surface layer of 500 m thickness or in the case of Svalbard and List 200 m. On a local scale, higher concentrations can occur. Tropospheric BrO could not be measured at any location outside the polar spring. Minimum detection limits for BrO were 2.2 ppt. Ground-based zenith-sky DOAS measurements of stratospheric chlorine dioxide have been performed at the Arctic sites Svalbard and Summit (73 deg N) as well as at the mid-latitudinal site Bremen (53 deg N) and used to validate SCIAMACHY OClO data for the exceptionally cold stratospheric spring 2005. OClO was also derived with a chemical stacked box model. The agreement of all three data sets is excellent for the time of overpass of the satellite instrument, i.e. 10 AM. However, the ground-based measurements could not be reproduced with the model simulations for large solar zenith angles as well as for large concentrations. Sensitivity studies have been performed with the chemistry model and this exercise demonstrated that the measured OClO columns cannot be explained within the known uncertainties of the model parameters including the involved photochemical data

Universität Bremen Measurements of halogen oxides

by scattered sunlight differential optical absorption spectroscop

Creating a Satellite-Based Record of Tropospheric Ozone

The TES retrieval algorithm has been applied to IASI radiances. We compare the retrieved ozone profiles with ozone sonde profiles for mid-latitudes for the year 2008. We find a positive bias in the IASI ozone profiles in the UTLS region of up to 22 %. The spatial coverage of the IASI instrument allows sampling of effectively the same air mass with several IASI scenes simultaneously. Comparisons of the root-mean-square of an ensemble of IASI profiles to theoretical errors indicate that the measurement noise and the interference of temperature and water vapour on the retrieval together mostly explain the empirically derived random errors. The total degrees of freedom for signal of the retrieval for ozone are 3.1 +/- 0.2 and the tropospheric degrees of freedom are 1.0 +/- 0.2 for the described cases. IASI ozone profiles agree within the error bars with coincident ozone profiles derived from a TES stare sequence for the ozone sonde station at Bratt's Lake (50.2 deg N, 104.7 deg W)