Figure 8 - uploaded by J.-F. Müller
Content may be subject to copyright.
H 2 CO vertical columns retrieved from GOME-2/MetOp- A (first panel, EUMETSAT level-1 data), OMI/Aura (second panel, NASA level-1 data), and their absolute differences (third panel) between 2007 and 2013.
Source publication
We present the new version (v14) of the BIRA-IASB algorithm for the retrieval
of formaldehyde (H2CO) columns from spaceborne UV–visible sensors.
Applied to OMI measurements from Aura and to GOME-2 measurements from MetOp-A
and MetOp-B, this algorithm is used to produce global distributions of
H2CO representative of mid-morning and early afternoon c...
Contexts in source publication
Context 1
... largest H 2 CO columns worldwide are observed in those regions, with very large variations between the dry and the wet season (see Table 2). Figure 18 shows the H 2 CO columns in Rondônia between 2003 and 2014, the MODIS (on Terra and Aqua satellites) Collection 5 Active Fire Prod- uct (ftp://fuoco.geog.umd.edu/modis/C5/cmg, Giglio, 2013), and the yearly deforestation rates reported by the Brazilian INPE (http://www.obt.inpe.br/prodes/index.php), in selected Amazonian states. ...
Context 2
... area between 1988 and 2013. This is the highest surface ratio among all Brazilian states. The years showing the highest deforestation rates are 1995 and 2004. In Rondônia, a strong decrease of the deforestation rate has been observed between 2005 and 2010, and a slight in- crease is again observed since 2011. As illustrated by the middle panel of Fig. 18, we find high correlation coeffi- cients between the SCIAMACHY/GOME-2 and OMI H 2 CO columns and the MODIS fire product, of respectively 0.8 and 0.9 (see also Barkley et al., 2013). We have also com- pared the H 2 CO vertical columns with GISS surface tem- perature anomalies (Gridded Monthly Maps of Temperature Anomaly Data, ...
Citations
... The CO mixing ratio vertical profiles are obtained from the spaceborne MOPITT instrument (Measurements Of Pollution In The Troposphere v9 TIR-NIR product; (Deeter et al 2022)). The daily tropospheric NO 2 vertical column density and tropospheric HCHO column density are acquired from the QA4ECV (Quality Assurance for Essential Climate Variables) OMI (Ozone Monitoring Instrument) retrieval (Boersma et al 2011, 2018, De Smedt et al 2015. Previous studies have validated the trends of Ω TNO2 , Ω THCHO and Ω TCO from these satellite observations by comparing them against surface observations and other satellite products (e.g. ...
The hydroxyl radical (OH) lies at the nexus of climate and air quality as the primary oxidant for both reactive greenhouse gases and many hazardous air pollutants. To better understand the role of climate variability on spatiotemporal patterns of OH, we utilize a 13-member ensemble of the Community Earth System Model version 2-Whole Atmosphere Community Climate Model version 6 (CESM2-WACCM6), a fully coupled chemistry-climate model, spanning the years 1950–2014. Ensemble members vary only in their initial conditions of the climate state in 1950. We focus on the final decade of the simulation, 2005–2014, when prior studies disagree on the signs of the global OH trends. The ensemble mean global airmass-weighted mean tropospheric column OH ( ΩTOH ), which is an estimate of the forced signal, increases by 0.06%/year between 2005 and 2014 while regional ΩTOH trends range from −0.56%/year over Southern Europe to +0.64%/year over South America. We show that ten-year ΩTOH trends are strongly affected by internal climate variability, as the spread of ΩTOH trends across the ensemble varies between 0.23%/year in Asia and 1.53%/year in South America. We train a fully connected neural network to emulate the ΩTOH simulated by the CESM2-WACCM6 model and combine it with satellite observations to interpret the role of OH chemical proxies. While the OH chemical proxies are subject to internal variability, the impact of internal variability on ΩTOH trends is primarily due to the meteorological parameters except for South America. Forced trends in global mean ΩTOH do not unambiguously emerge from trends driven by internal variability over the 2005–2014 period. The observation-constrained ΩTOH presents opposite trends due to climate variability, resulting in varying conclusions on the attribution of OH to CH4 trends.
... Decreases in MOPITT (Measurement of Pollution in the Troposphere) CO, Quick Fire Emissions Dataset CO emissions, OMI NO 2 , and MODIS (Moderate Resolution Imaging Spectrometer) AOD ( Figure S2 in Supporting Information S1) over the Brazilian Amazon during this period suggest that a decline in South American biomass burning is the underlying cause of these CO changes, in agreement with Buchholz et al. (2021) and Y. Chen et al. (2023). The HCHO trend downwind of the biomass burning region (Figure 3b and Figure S2b in Supporting Information S1) is consistent with this idea as a decrease in fires would lead to decreases in emissions of HCHO and its precursors (e.g., De Smedt et al., 2015). This decrease in HCHO and likely its VOC precursors partially offset the increasing TCOH trend in the region (Figure 3b). ...
Plain Language Summary
Hydroxyl is a chemical that removes many gases from the atmosphere, including methane, an important greenhouse gas. To understand recent trends in methane, we must also understand recent trends in hydroxyl. Because of various limitations, we unfortunately do not have long‐term, direct observations of hydroxyl. To address this problem, we have developed a machine learning model that uses satellite observations of variables relevant to hydroxyl chemistry and variability to calculate hydroxyl. We demonstrate that this product can be used to understand trends and variability of hydroxyl over the tropical oceans. While, on average, hydroxyl increases from 2005–2019, we show that this is not a universal trend and that hydroxyl actually decreases in multiple regions over the same time period. Using satellite observations of various chemicals, we demonstrate that changes in emissions due to human activity and increases in temperature cause many of these trends. This product is potentially a significant advance in understanding changes in hydroxyl and could be a useful complement to more traditional methods in understanding atmospheric methane.
... Subsequent LEO satellites, including the Ozone Monitoring Instrument (OMI), TROPOspheric Monitoring Instrument (TROPOMI), Global Ozone Monitoring Experiment 2A (GOME-2A), and Ozone Mapping and Profiler Suite (OMPS) nadir mapper, have substantially finer spatial resolutions (approximately 5.5 km × 3.5 km to 80 km × 40 km), enabling the observation of local pollution plumes and the provision of observational constraints for biogenic and anthropogenic sources globally (Veefkind et al., 2012;De Smedt et al., 2015Li et al., 2015;González Abad et al., 2016;Levelt et al., 2018;Nowlan et al., 2023;Kwon et al., 2023). Moreover, De Smedt et al. (2015) examined the diurnal characteristics of global HCHO VCDs from GOME-2 and OMI with different overpass times (GOME-2 09:30 and OMI 13:30, local time), showing that afternoon HCHO VCDs are higher than in the morning over most regions, with exceptions in the tropical rainforest. ...
... Figure 12 shows the diurnal variations in the GEMS and MAX-DOAS HCHO VCDs. De Smedt et al. (2015) showed the diurnal variation in HCHO from the MAX-DOAS at Xianghe from 2010 to 2013, with two peaks occurring in the morning (06:00-08:00 LT) and afternoon (14:00-16:00 LT) due to anthropogenic emissions during peak traffic and high insolation with increasing temperature, respectively. The diurnal variation in VCDs from GEMS is consistent with pre- Figure S10 shows the same analysis from FTIR, which presents a diurnal variation consistent with that of GEMS. ...
The Geostationary Environment Monitoring Spectrometer (GEMS) on board GEO-KOMPSAT-2B was launched in February 2020 and has been monitoring atmospheric chemical compositions over Asia. We present the first evaluation of the operational GEMS formaldehyde (HCHO) vertical column densities (VCDs) during and after the in-orbit test (IOT) period (August–October 2020) by comparing them with the products from the TROPOspheric Monitoring Instrument (TROPOMI) and Fourier-transform infrared (FTIR) and multi-axis differential optical absorption spectroscopy (MAX-DOAS) instruments. During the IOT, the GEMS HCHO VCDs reproduced the observed spatial pattern of TROPOMI VCDs over the entire domain (r= 0.62) with high biases (10 %–16 %). We found that the agreement between GEMS and TROPOMI was substantially higher in Northeast Asia (r= 0.90), encompassing the Korean Peninsula and east China. GEMS HCHO VCDs captured the seasonal variation in HCHO, primarily driven by biogenic emissions and photochemical activities, but showed larger variations than those of TROPOMI over coastal regions (Kuala Lumpur, Singapore, Shanghai, and Busan). In addition, GEMS HCHO VCDs showed consistent hourly variations with MAX-DOAS (r= 0.77) and FTIR (r= 0.86) but were 30–40 % lower than ground-based observations. Different vertical sensitivities of GEMS and ground-based instruments caused these biases. Utilizing the averaging kernel smoothing method reduces the low biases by approximately 10 % to 15 % (normalized mean bias (NMB): −47.4 % to −31.5 % and −38.6 % to −26.7 % for MAX-DOAS and FTIR, respectively). The remaining discrepancies are due to multiple factors, including spatial collocation and different instrumental sensitivities, requiring further investigation using inter-comparable datasets.
... For HCHO TVCDs, we utilized the QA4ECV HCHO v1.2 product by the European consortium (BIRA, IUP, MPIC, KNMI, WUR) (De Smedt et al., 2015Smedt et al., , 2017 and OMHCHO v3 product from NASA (Chance, 2007). As the TROPOMI L2 HCHO product is not available for our study period, we obtained 0.05° × 0.05° L3 daily data processed by the BIRA team (De Smedt et al., 2021). ...
Nitrogen dioxide (NO2) and formaldehyde (HCHO) play vital roles in atmospheric photochemical processes. Their tropospheric vertical column density (TVCD) distributions have been monitored by satellite instruments. Evaluation of these observations is essential for applying these observations to study photochemistry. Assessing satellite products using observations at rural sites, where local emissions are minimal, is particularly useful due in part to the spatial homogeneity of trace gases. In this study, we evaluate OMI and TROPOMI NO2 and HCHO TVCDs using multi‐axis differential optical absorption spectroscopy (MAX‐DOAS) measurements at a rural site in the east coast of the Shandong province, China in spring 2018 during the Ozone Photochemistry and Export from China Experiment (OPECE) measurement campaign. On days not affected by local burning, we found generally good agreement of NO2 data after using consistent a priori profiles in satellite and MAX‐DOAS retrievals and accounting for low biases in scattering weights in one of the OMI products. In comparison, satellite HCHO products exhibited weaker correlations with MAX‐DOAS data, in contrast to satellite NO2 products. However, TROPOMI HCHO products showed significantly better agreement with MAX‐DOAS measurements compared to OMI data. Furthermore, case studies of the vertical profiles measured by MAX‐DOAS on burning days revealed large enhancements of nitrous acid (HONO), NO2, and HCHO in the upper boundary layer, accompanied with considerable variability, particularly in HONO enhancements.
... We found a good correlation (slope = 0.97, correlation coefficient = 0.9358), so it is reasonable to analyze the formaldehyde surface observation of GJ together with other species measured at EP in this study. Site-specific local characteristics can be important for finer-scale temporal variation such as diurnal profiles owing to the short lifetime of formaldehyde, but not critical for monthly variation (De Smedt et al., 2015). Table S1 lists the ground observation of formaldehyde concentrations reported in previous studies by season. ...
... The HCHO value of the NJ site increased from 10:00 to approximately 14:00, remained constant until 17:00, and then began to decline. The daily pattern of formaldehyde in Nanjing was similar to that in Shanghai in the YRD and Beijing, which should be attributed to vehicle biogenic emissions, and the secondary formation from the photolysis of volatile organic compounds (VOCs) [5,48]. ...
Due to the difference of industrialization degree and meteorological conditions, there are obvious differences in the composition of air pollution between islands and inland areas. With Zhoushan (ZS) and Nanjing (NJ) representing islands and inland cities in the Yangtze River Delta, the differences in vertical distribution of atmospheric components were investigated. A combination of multi-axial differential optical absorption spectroscopy (MAX-DOAS), weather research and forecasting (WRF), and potential source contribution function (PSCF) models were used to obtain vertical distribution data for aerosols, nitrogen dioxide (NO2) and formaldehyde (HCHO), meteorological factors, and pollution sources in summer 2019. The findings indicate that, except for the aerosol extinction coefficient (AE), the atmospheric composition at the ZS site was not significantly stratified. However, the AE, NO2, and HCHO at NJ all displayed a decreasing trend with altitude. Here is the interesting finding that the ZS site has a higher AE value than the NJ site, while NJ displays higher NO2 and HCHO columns than the ZS site. This discrepancy was primarily attributable to Zhoushan City’s extremely low traffic emissions when compared to inland cities. In addition, HCHO in the YRD region was significantly affected by human activities. Analysis of potential pollution sources found that regional transport contributed to differences in atmospheric composition at different altitudes in different regions. Aerosols, NO2, and HCHO in Nanjing were significantly affected by transport in inland areas. Aerosols in Zhoushan were easily affected by transport in the Yellow Sea and East China Sea, and NO2 and HCHO were significantly affected by transport contributions from surrounding areas in inland areas. The study strongly suggests that land and sea breezes play an important role in the vertical distribution of aerosols over island regions.
... Offline satellite data with a quality assurance value (QA_value) above 0.5 (no error flag, cloud radiance fraction (CRF) at 340 nm < 0.5, solar zenith angles ≤ 70 • , surface albedo ≤ 0.2, no snow/ice warning, air mass factor > 0.1) were selected in order to avoid misinterpretation of the data quality. According to past research, early afternoon overpass time corresponds to the daily peak of HCHO [55,83]. Hence, in our study, HCHO gg in the afternoon when a high AOC was forecasted was mainly selected for comparison with HCHO sd . ...
Formaldehyde (HCHO) plays an important role in atmospheric photochemical reactions. Comparative studies between ground-based and satellite observations are necessary to assess and promote the potential use of column HCHO as a proxy for surface HCHO and volatile organic compound (VOC) oxidation. Previous studies have only validated temporal and vertical profile variations at one point, with limited studies comparing horizontal spatial variations due to sparse monitoring sites. The photochemistry-active Chinese Greater Bay Area (GBA) is a typical megacity cluster as well as a large hotspot of HCHO globally, which recorded a high incidence of ozone (O3) pollution. Here, we conducted the first comparative study of ground-gridded (HCHOgg) and satellite-derived (HCHOsd) HCHO during typical O3 episodes in the GBA. Our results revealed a good correlation between HCHOgg and HCHOsd, with a correlation coefficient higher than 0.5. Cloud coverage and ground pixel sizes were found to be the dominant factors affecting the quality of HCHOsd and contributing to the varying satellite pixel density. Daily averages of HCHOsd effectively improved the HCHOsd accuracy, except in areas with low satellite pixel density. Furthermore, a new quality control procedure was established to improve HCHOsd from Level 2 to Level 3, which demonstrated good application performance in O3 sensitivity analysis. Our findings indicate that the correlation between satellite observations and surface air quality can be optimized by spatiotemporal averaging of hourly HCHOsd, given the advent of geostationary satellites. Considering the representative range of sampling sites in this comparative study, we recommend establishing VOC monitoring stations within a 50 km radius in the GBA to further analyze and control photochemical pollution.
... OMI also has systematically biased retrievals in a striped pattern running in 60 cross-track fields of view. A "destriping" correction is applied to NO 2 data (Boersma et al., 2011), and the reference sector method corrects this artifact in HCHO data (De Smedt et al., 2015;González Abad et al., 2015;Zara et al., 2018). ...
Satellite retrievals of tropospheric-column formaldehyde (HCHO) and nitrogen dioxide (NO2) are frequently used to investigate the sensitivity of ozone (O3) production to emissions of nitrogen oxides and volatile organic carbon compounds. This study inter-compared the systematic biases and uncertainties in retrievals of NO2 and HCHO, as well as resulting HCHO–NO2 ratios (FNRs), from two commonly applied satellite sensors to investigate O3 production sensitivities (Ozone Monitoring Instrument, OMI, and TROPOspheric Monitoring Instrument, TROPOMI) using airborne remote-sensing data taken during the Long Island Sound Tropospheric Ozone Study 2018 between 25 June and 6 September 2018. Compared to aircraft-based HCHO and NO2 observations, the accuracy of OMI and TROPOMI were magnitude-dependent with high biases in clean environments and a tendency towards more accurate comparisons to even low biases in moderately polluted to polluted regions. OMI and TROPOMI NO2 systematic biases were similar in magnitude (normalized median bias, NMB = 5 %–6 %; linear regression slope ≈ 0.5–0.6), with OMI having a high median bias and TROPOMI resulting in small low biases. Campaign-averaged uncertainties in the three satellite retrievals (NASA OMI; Quality Assurance for Essential Climate Variables, QA4ECV OMI; and TROPOMI) of NO2 were generally similar, with TROPOMI retrievals having slightly less spread in the data compared to OMI. The three satellite products differed more when evaluating HCHO retrievals. Campaign-averaged tropospheric HCHO retrievals all had linear regression slopes ∼0.5 and NMBs of 39 %, 17 %, 13 %, and 23 % for NASA OMI, QA4ECV OMI, and TROPOMI at finer (0.05∘×0.05∘) and coarser (0.15∘×0.15∘) spatial resolution, respectively. Campaign-averaged uncertainty values (root mean square error, RMSE) in NASA and QA4ECV OMI HCHO retrievals were ∼9.0×1015 molecules cm−2 (∼ 50 %–55 % of mean column abundance), and the higher-spatial-resolution retrievals from TROPOMI resulted in RMSE values ∼30 % lower. Spatially averaging TROPOMI tropospheric-column HCHO, along with NO2 and FNRs, to resolutions similar to the OMI reduced the uncertainty in these retrievals. Systematic biases in OMI and TROPOMI NO2 and HCHO retrievals tended to cancel out, resulting in all three satellite products comparing well to observed FNRs. However, while satellite-derived FNRs had minimal campaign-averaged median biases, unresolved errors in the indicator species did not cancel out in FNR calculations, resulting in large RMSE values compared to observations. Uncertainties in HCHO retrievals were determined to drive the unresolved biases in FNR retrievals.
... MAX-DOAS observations show very good sensitivity in the troposphere, where most of the HCHO resides. Therefore, it has long been used for satellite validation (Vigouroux et al., 2009;Li et al., 2013;De Smedt et al., 2015bWang et al., 2017;Chan et al., , 2020bKumar et al., 2020). The retrievals of HCHO columns from MAX-DOAS observations are performed within a wavelength range similar to the GOME-2 retrieval, i.e. 328-359 nm. ...
... Mexico City (Mexico) and Xianghe (China). The underestimation is related to the difference in sensitivity, and this effect has been reported in previous level-2 validation studies for GOME-2 (De Smedt et al., 2015b;Pinardi et al., 2020b) as well as for other satellites (Chan et al., 2020b;De Smedt et al., 2021). ...
We introduce the new Global Ozone Monitoring Experiment-2 (GOME-2) daily and monthly level-3 product of total column ozone (O3), total and tropospheric column nitrogen dioxide (NO2), total column water vapour, total column bromine oxide (BrO), total column formaldehyde (HCHO), and total column sulfur dioxide (SO2) (daily products https://doi.org/10.15770/EUM_SAF_AC_0048, AC SAF, 2023a; monthly products https://doi.org/10.15770/EUM_SAF_AC_0049, AC SAF, 2023b). The GOME-2 level-3 products aim to provide easily translatable and user-friendly data sets to the scientific community for scientific progress as well as to satisfy public interest. The purpose of this paper is to present the theoretical basis as well as the verification and validation of the GOME-2 daily and monthly level-3 products. The GOME-2 level-3 products are produced using the overlapping area-weighting method. Details of the gridding algorithm are presented. The spatial resolution of the GOME-2 level-3 products is selected based on the sensitivity study. The consistency of the resulting level-3 products among three GOME-2 sensors is investigated through time series of global averages, zonal averages, and bias. The accuracy of the products is validated by comparison to ground-based observations. The verification and validation results show that the GOME-2 level-3 products are consistent with the level-2 data. Small discrepancies are found among three GOME-2 sensors, which are mainly caused by the differences in the instrument characteristic and level-2 processor. The comparison of GOME-2 level-3 products to ground-based observations in general shows very good agreement, indicating that the products are consistent and fulfil the requirements to serve the scientific community and general public.
... 32 OMI provides daily global measurements whereas GOME-2B has a default swath width of 1920 km, allowing for global coverage within 1.5-3 days at the Equator. 33 The OMI NO 2 measurements are made in 3 channels between 264 and 504 nm and GOME-2B in 4 bands between 240 and 790 nm. 34 We have merged OMI (2004-2014) and GOME-2B (2013-2021) data using a modied bias correction method by nding the cumulative distribution of data for the overlapping period (Fig. S1 †) to minimize bias in the older instrument using measurements from the new instrument, as described by Bai et al., 35 to get long-term continuous data from 2004 to 2021. ...
The Third Pole, Hindu Kush Himalaya (HKH) and Tien Shan mountains, has been closely monitored for the past few decades because of its deteriorating environmental condition. Here, we analyse the spatio-temporal changes in tropospheric NO2 over TP using satellite observations from 2005 to 2020. The highest NO¬2 concentrations (i.e. ≥ 1 × 1015 molec. cm-2) are found in the boundaries close to Indo-Gangetic Plain (IGP), and Yellow and Yangtze River basins (YYRB). The analysis of Emissions Database for Global Atmospheric Research (EDGAR v6.1) shows that the main contribution to NO2 in the region is from the road transport (81%) and then power sector (7%). The Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) analyses illustrate that the major regions from which air mass reach TP is from IGP, Southeast Asia, YYRB, Central Asia and Middle East. Our analysis reveals a positive trend in NO2 over most regions of TP (up to 0.05 ± 0.01 × 1015 molec. cm-2 year-1) in the yearly averaged data for the period 2005–2020, which suggest that the pollution is spreading even to the inner regions of TP. Therefore, this study reveals that the inner TP, one of the most pristine regions on the earth, is getting polluted because of high anthropogenic activities within and nearby areas/cities; indicating the impact of regional development activities and socioeconomic changes in recent years.
