Abstract
This work demonstrates for the first time the capability of routine Tropospheric Monitoring Instrument (TROPOMI) operations to quantify CO emission rates down to industrial point sources. We ...have quantified the CO emission rates of four industrial point sources in Asia, namely Qianlishan Industrial Park (39.9° N, 106.9° E), Jiuyuan Industrial Park (40.7° N, 109.7° E) and Botian Industrial Park (42.2° N, 125.2° E) in China and the Jindal factory (15.2° N, 76.7° E) in India, with TROPOMI CO observations from 2017 to 2020. Qianlishan Industrial Park is a missing source in the emission inventory and we quantify it to be ∼14.0 kg s
−1
. Our estimates for the other three sources vary between 14.4 and 34.3 kg s
−1
, within 37%–69% of the inventory values. The plume inversion methods are presented in a manner that can be easily used with other fine-scale emission plumes observed from space. Although only a small number of CO plumes per year for any given industrial point source can be observed under conditions suitable for estimation of emission rates, there are many industrial point sources that can be captured by a good TROPOMI footprint. This work affirms that a constellation of future CO satellites could monitor individual CO point source emissions to support environmental policies.
The seasonal evolution of O3 and its photochemical
production regime in a polluted region of eastern China between 2014 and 2017
has been investigated using observations. We used tropospheric ozone
...(O3), carbon monoxide (CO), and formaldehyde (HCHO, a marker of VOCs
(volatile organic compounds)) partial columns derived from high-resolution
Fourier transform spectrometry (FTS); tropospheric nitrogen dioxide
(NO2, a marker of NOx (nitrogen oxides)) partial
column deduced from the Ozone Monitoring Instrument (OMI); surface meteorological
data; and a back trajectory cluster analysis technique. A broad O3
maximum during both spring and summer (MAM/JJA) is observed; the day-to-day
variations in MAM/JJA are generally larger than those in autumn and winter
(SON/DJF). Tropospheric O3 columns in June are 1.55×1018 molecules cm−2 (56 DU (Dobson units)), and in December they are
1.05×1018 molecules cm−2 (39 DU). Tropospheric O3
columns in June were ∼50 % higher than those in December. Compared
with the SON/DJF season, the observed tropospheric O3 levels in MAM/JJA
are more influenced by the transport of air masses from densely populated and
industrialized areas, and the high O3 level and variability in
MAM/JJA is determined by the photochemical O3 production. The
tropospheric-column HCHO∕NO2 ratio is used as a proxy to
investigate the photochemical O3 production rate (PO3).
The results show that the PO3 is mainly nitrogen oxide (NOx) limited in MAM/JJA, while it is mainly VOC or mixed VOC–NOx limited in SON/DJF. Statistics show that
NOx-limited, mixed VOC–NOx-limited, and VOC-limited PO3 accounts for 60.1 %, 28.7 %, and 11 % of days,
respectively. Considering most of PO3 is NOx
limited or mixed VOC–NOx limited, reductions in
NOx would reduce O3 pollution in eastern China.
We for the first time demonstrate ground-based remote sensing of Nitrous Oxide (N
2
O) over Hefei in eastern China from high resolution Fourier Transform Infra-Red (FTIR) solar spectra. We have ...retrieved Column-averaged Abundance of N
2
O (
) from both Near-Infrared (NIR, 4000 to 11,000 cm
−1
) and Mid-Infrared (MIR, 2400 to 3200 cm
−1
) solar spectra and inspected their agreement. Generally, NIR and MIR measurements agree well with a correlation coefficient of 0.86 and an average difference of (1.33 ± 4.05) ppbv (NIR - MIR). By correcting the bias of the two datasets, we combine the NIR and MIR measurements to investigate seasonality and inter-annual trend of
over Hefei. The observed monthly mean time series of
minimize in June and maximize in September, with values of (316.55 ± 12.22) ppbv and (322.05 ± 12.93) ppbv, respectively. The
time series from 2015 to 2020 showed an inter-annual trend of (0.53 ± 0.10) %/year over Hefei, China. We also compared the FTIR
observations with GEOS-Chem model
simulations. They are in reasonable agreement with a correlation coefficient (R) of 0.71, but GEOS-Chem model underestimated the seasonality of the observations. This study can enhance current knowledge of ground-based high-resolution FTIR remote sensing of N
2
O in the atmosphere and contribute to generating a new reliable N
2
O dataset for climate change research.
Since its launch on 13 October 2017, the TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel-5 Precursor (S5P) mission has been measuring the solar radiation backscattered by Earth’s ...atmosphere and surface. In this study, we evaluate the TROPOMI operational methane (CH4) and carbon monoxide (CO) products’ performance results covering about 3 years using the only two global Total Carbon Column Observing Network (TCCON) sites in China, i.e., the Hefei site and the Xianghe site. These two sites have recently joined the TCCON, and this study uses the both sites simultaneously to validate the TROPOMI products over China for the first time. We found that the systematic bias with rescaling between the TROPOMI CO products and the Hefei site is on average 1.78 ± 6.35 ppb or 1.18 ± 5.35%. The systematic bias with rescaling between the TROPOMI CO products and the Xianghe site is on average 5.33 ± 14.24 ppb or 3.85 ± 10.30%. Both the stations show a correlation above 0.9. The TROPOMI CO data are systematically higher than the two TCCON sites measurements in China. We found that the systematic bias with rescaling between the TROPOMI CH4 products and the Hefei site is on average −4.13 ± 11.65 ppb or −0.22 ± 0.62%. The systematic bias between the TROPOMI CH4 products and Xianghe site is on average −7.25 ± 10.72 ppb or −0.39 ± 0.57%. Both the stations show a correlation above 0.9. The TROPOMI CH4 data are systematically lower than the two TCCON sites measurements in China. We found that the bias between the TROPOMI and the two sites’ data as a function of the coincident radius around the two sites is mostly affected by localized emissions for both CO and CH4. We also observe a CO decreasing trend and a CH4 increasing trend in the year-to-year relative changes from 2019 to 2021. Validating against reference from Hefei and Xianghe TCCON site demonstrates the high quality of TROPOMI CO and CH4 data over China.
In a 3.5-year long study, the long-term
performance of a mobile, solar absorption Bruker EM27/SUN spectrometer, used
for greenhouse gas observations, is checked with respect to a co-located
reference ...Bruker IFS 125HR spectrometer, which is part of the Total Carbon
Column Observing Network (TCCON). We find that the EM27/SUN is stable on
timescales of several years; the drift per year between the EM27/SUN and the
official TCCON product is 0.02 ppmv for XCO2 and 0.9 ppbv for
XCH4, which is within the 1σ precision of the comparison,
0.6 ppmv for XCO2 and 4.3 ppbv for XCH4. The bias between
the two data sets is 3.9 ppmv for XCO2 and 13.0 ppbv for
XCH4. In order to avoid sensitivity-dependent artifacts, the EM27/SUN
is also compared to a truncated IFS 125HR data set derived from
full-resolution TCCON interferograms. The drift is 0.02 ppmv for
XCO2 and 0.2 ppbv for XCH4 per year, with 1σ
precisions of 0.4 ppmv for XCO2 and 1.4 ppbv for XCH4,
respectively. The bias between the two data sets is 0.6 ppmv for
XCO2 and 0.5 ppbv for XCH4. With the presented long-term
stability, the EM27/SUN qualifies as an useful supplement to the existing
TCCON network in remote areas. To achieve consistent performance, such an
extension requires careful testing of any spectrometers involved by
application of common quality assurance measures. One major aim of the
COllaborative Carbon Column Observing Network (COCCON) infrastructure is to
provide these services to all EM27/SUN operators. In the framework of COCCON
development, the performance of an ensemble of 30 EM27/SUN spectrometers was
tested and found to be very uniform, enhanced by the centralized inspection
performed at the Karlsruhe Institute of Technology prior to deployment.
Taking into account measured instrumental line shape parameters for each
spectrometer, the resulting average bias across the ensemble with respect to
the reference EM27/SUN used in the long-term study in XCO2 is
0.20 ppmv, while it is 0.8 ppbv for XCH4. The average standard
deviation of the ensemble is 0.13 ppmv for XCO2 and 0.6 ppbv for
XCH4. In addition to the robust metric based on absolute differences,
we calculate the standard deviation among the empirical calibration factors.
The resulting 2σ uncertainty is 0.6 ppmv for XCO2 and
2.2 ppbv for XCH4. As indicated by the executed long-term study on
one device presented here, the remaining empirical calibration factor deduced
for each individual instrument can be assumed constant over time. Therefore
the application of these empirical factors is expected to further improve the
EM27/SUN network conformity beyond the scatter among the empirical
calibration factors reported above.
Because of the unique geographical, climate, and anthropogenic emission characteristics, it is meaningful to explore the air pollution in the Harbin-Changchun (HC) metropolitan area. In this study, ...the Air Quality Index (AQI) and the corresponding major pollutant were investigated for the HC cities, based on the air quality data derived from the China National Environmental Monitoring Center. The number of days with the air quality level of "good" gradually increased during recent years, pointing to an improvement of the air quality in HC. It was also found that ozone, a typical secondary pollutant, exhibited stronger inter-city correlations compared to typical primary pollutants such as carbon monoxide and nitrogen dioxide. In addition, for nearly all the HC cities, the concentrations of fine particulate matter (PM
) decreased substantially in 2020 compared to 2015. However, this was not the case for ozone, with the most significant increase of ozone observed for HC's central city, Harbin. This study highlights the importance of ozone reduction for further improving HC's air quality, and the importance of agricultural fire control for eliminating heavily-polluted and even off-the-charts PM
episodes.
Long-term observations of the volume mixing ratio (VMR) profiles and total columns of key atmospheric constituents are significant for understanding climate change and the impact of the carbon budget ...in China. This study provides an overview of the first ground-based high-resolution Fourier-transform spectrometry (FTS) observation station in China, which is located in Hefei, east China. The FTS observation station can observe the total columns and VMR profiles of more than 30 atmospheric constituents. Time series of some key atmospheric constituents observed at the Hefei station since 2014 have been released to the public. The major scientific achievements obtained to date at this station include spectral retrieval characterization and harmonization, investigation of the overall characteristics of key atmospheric constituents, emission estimates, satellite and chemical transport model (CTM) evaluations, and a summary of pollutant sources and transport patterns. An outlook is also presented of the envisaged plan for observations, scientific studies, and data usage at the Hefei station. China has explicitly proposed reaching a peak in its CO2 emissions by 2030 and realizing carbon neutrality by 2060. The Hefei station will provide scientific assistance to the Chinese Government for developing green economy policies and achieving carbon neutrality and the goals of the Paris Agreement.
High resolution Fourier transform infrared (FTIR) measurement of direct sunlight does not only provide information of trace gas total columns, but also vertical distribution. Measured O3, CO, CH4, ...and N2O can be separated into multiple partial columns using the optimal estimation method (OEM). The retrieval of trace gas profiles is sensitive to the instrument line shape (ILS) of the FTIR spectrometer. In this paper, we present an investigation of the influence of ILS degradation on the partial column retrieval of O3, CO, CH4, and N2O. Sensitivities of the partial column, error, and degrees of freedom (DOFs) of each layer to different levels of ILS degradation for O3, CO, CH4, and N2O are estimated. We then evaluate the impact of ILS degradation on the long-term measurements. In addition, we derive the range of ILS degradation corresponding to the acceptable uncertainties of O3, CO, CH4, and N2O results. The results show that the uncertainties induced by the ILS degradation on the absolute value, error, and the DOFs of the partial column are altitude and gas species dependent. The uncertainties of the partial columns of O3 and CO are larger than those on CH4 and N2O. The stratospheric partial columns are more sensitive to the ILS degradation compared to the tropospheric part. Our result improves the understanding of the ILS degradation on the FTIR measurements, which is important for the quantification of the measurement uncertainties and minimizes the bias of the inter-comparison between different measurement platforms. This is especially useful for the validation of satellite observations, the data assimilation of chemical model simulations, and the quantification of the source/sink/trend from the FTIR measurements.
We analyzed seasonality and interannual variability of tropospheric hydrogen cyanide (HCN)
columns in densely populated eastern China for the first time. The results
were derived from solar ...absorption spectra recorded with a ground-based high-spectral-resolution Fourier transform infrared (FTIR) spectrometer in Hefei
(31∘54′ N, 117∘10′ E) between 2015 and
2018. The tropospheric HCN columns over Hefei, China, showed significant
seasonal variations with three monthly mean peaks throughout the year. The
magnitude of the tropospheric HCN column peaked in May, September, and December. The tropospheric HCN column reached a maximum monthly
mean of (9.8±0.78)×1015 molecules cm−2 in May
and a minimum monthly mean of (7.16±0.75)×1015 molecules cm−2 in November. In most cases, the tropospheric HCN columns
in Hefei (32∘ N) are higher than the FTIR observations in Ny-Ålesund (79∘ N), Kiruna (68∘ N), Bremen (53∘ N), Jungfraujoch (47∘ N), Toronto (44∘ N), Rikubetsu
(43∘ N), Izana (28∘ N), Mauna Loa (20∘ N), La
Reunion Maido (21∘ S), Lauder (45∘ S), and Arrival
Heights (78∘ S) that are affiliated with the Network for Detection
of Atmospheric Composition Change (NDACC). Enhancements of tropospheric HCN
column were observed between September 2015 and July 2016 compared to the
same period of measurements in other years. The magnitude of the enhancement
ranges from 5 % to 46 % with an average of 22 %. Enhancement of
tropospheric HCN (ΔHCN) is correlated with the concurrent
enhancement of tropospheric CO (ΔCO), indicating that enhancements
of tropospheric CO and HCN were due to the same sources. The GEOS-Chem tagged CO simulation, the global fire maps, and the potential source
contribution function (PSCF) values calculated using back trajectories
revealed that the seasonal maxima in May are largely due to the influence of
biomass burning in Southeast Asia (SEAS) (41±13.1 %), Europe
and boreal Asia (EUBA) (21±9.3 %), and Africa (AF) (22±4.7 %). The seasonal maxima in September are largely due to the influence
of biomass burnings in EUBA (38±11.3 %), AF (26±6.7 %),
SEAS (14±3.3 %), and North America (NA) (13.8±8.4 %).
For the seasonal maxima in December, dominant contributions are from AF (36±7.1 %), EUBA (21±5.2 %), and NA (18.7±5.2 %). The tropospheric HCN enhancement between September 2015 and July
2016 at Hefei (32∘ N) was attributed to an elevated influence of
biomass burnings in SEAS, EUBA, and Oceania (OCE) in this period. In
particular, an elevated number of fires in OCE in the second half of 2015
dominated the tropospheric HCN enhancement between September and December 2015. An
elevated number of fires in SEAS in the first half of 2016 dominated the
tropospheric HCN enhancement between January and July 2016.
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