scholarly journals Review of “FTIR time series of tropospheric HCN in eastern China: seasonality, interannual variability and source attribution” by Sun et al.

2020 ◽  
Author(s):  
Anonymous
Keyword(s):  
Time Series ◽  
Interannual Variability ◽  
Eastern China ◽  
Source Attribution

scholarly journals Fourier transform infrared time series of tropospheric HCN in eastern China: seasonality, interannual variability, and source attribution

2020 ◽  
Vol 20 (9) ◽  
pp. 5437-5456
Author(s):  
Youwen Sun ◽  
Cheng Liu ◽  
Lin Zhang ◽  
Mathias Palm ◽  
Justus Notholt ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Interannual Variability ◽  
Eastern China ◽  
Fourier Transform Infrared ◽  
Atmospheric Composition ◽  
High Spectral Resolution ◽  
Source Attribution ◽  
Solar Absorption ◽  
Back Trajectories ◽  
Mauna Loa

Abstract. 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.

scholarly journals FTIR time series of tropospheric HCN in eastern China: seasonality, interannual variability and source attribution

2020 ◽  
Author(s):  
Youwen Sun ◽  
Cheng Liu ◽  
Lin Zhang ◽  
Mathias Palm ◽  
Justus Notholt ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Eastern China ◽  
Atmospheric Composition ◽  
High Spectral Resolution ◽  
Source Attribution ◽  
Solar Absorption ◽  
Back Trajectories ◽  
Mauna Loa ◽  
Ftir Spectrometer ◽  
First Time

Abstract. We analyzed seasonality and interannual variability of tropospheric HCN column amounts in densely populated eastern China for the first time. The results were derived from solar absorption spectra recorded with ground-based high spectral resolution Fourier transform infrared (FTIR) spectrometer at Hefei (117°10′ E, 31°54′ N) 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 peak in May > September > December. The tropospheric HCN column reached a maximum of (9.8 ± 0.78) × 1015 molecules/cm2 in May and a minimum of (7.16 ± 0.75) × 1015 molecules/cm2 in November. In most cases, the tropospheric HCN columns at Hefei (32° N) are higher than the FTIR observations at Ny Alesund (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 the tropospheric HCN columns were observed between September 2015 and July 2016 compared to the counterpart 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 coincident 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 PSCFs (Potential Source Contribution Function) calculated using back trajectories revealed that the seasonal maxima in May is largely due to the influence of biomass burning in South Eastern Asia (SEAS) (41 ± 13.1 %), Europe and Boreal Asia (EUBA) (21 ± 9.3 %) and Africa (AF) (22 ± 4.7 %). The seasonal maxima in September is largely due to the influence of biomass burnings in EUBA (38 ± 11.3 %), AF (26 ± 6.7 %), SEAS (14 ± 3.3 %), and Northern 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) were attributed to an elevated influence of biomass burnings in SEAS, EUBA, and Oceania (OCE) in this period. Particularly, an elevated fire number in OCE in the second half of 2015 dominated the tropospheric HCN enhancement in September–December 2015. An elevated fire number in SEAS in the first half of 2016 dominated the tropospheric HCN enhancement in January–July 2016.

scholarly journals Stratospheric ozone interannual variability (1995–2011) as observed by Lidar and Satellite at Mauna Loa Observatory, HI and Table Mountain Facility, CA

2012 ◽  
Vol 12 (11) ◽  
pp. 30825-30867
Author(s):  
G. Kirgis ◽  
T. Leblanc ◽  
I. S. McDermid ◽  
T. D. Walsh
Keyword(s):  
Time Series ◽  
Solar Cycle ◽  
Interannual Variability ◽  
Southern Oscillation ◽  
Stratospheric Ozone ◽  
Montreal Protocol ◽  
Quasi Biennial Oscillation ◽  
Mauna Loa ◽  
Table Mountain ◽  
Biennial Oscillation

Abstract. The Jet Propulsion Laboratory (JPL) lidars, at the Mauna Loa Observatory, Hawaii (MLO, 19.5° N, 155.6° W) and the JPL Table Mountain Facility (TMF, California, 34.5° N, 117.7° W), have been measuring vertical profiles of stratospheric ozone routinely since the early 1990's and late-1980s respectively. Interannual variability of ozone above these two sites was investigated using a multi-linear regression analysis on the deseasonalized monthly mean lidar and satellite time-series at 1 km intervals between 20 and 45 km from January 1995 to April 2011, a period of low volcanic aerosol loading. Explanatory variables representing the 11-yr solar cycle, the El Niño Southern Oscillation, the Quasi-Biennial Oscillation, the Eliassen–Palm flux, and horizontal and vertical transport were used. A new proxy, the mid-latitude ozone depleting gas index, which shows a decrease with time as an outcome of the Montreal Protocol, was introduced and compared to the more commonly used linear trend method. The analysis also compares the lidar time-series and a merged time-series obtained from the space-borne stratospheric aerosol and gas experiment II, halogen occultation experiment, and Aura-microwave limb sounder instruments. The results from both lidar and satellite measurements are consistent with recent model simulations which propose changes in tropical upwelling. Additionally, at TMF the ozone depleting gas index explains as much variance as the Quasi-Biennial Oscillation in the upper stratosphere. Over the past 17 yr a diminishing downward trend in ozone was observed before 2000 and a net increase, and sign of ozone recovery, is observed after 2005. Our results which include dynamical proxies suggest possible coupling between horizontal transport and the 11-yr solar cycle response, although a dataset spanning a period longer than one solar cycle is needed to confirm this result.

scholarly journals Trends in Stratospheric Ozone: Lessons Learned from a 3D Chemical Transport Model

2006 ◽  
Vol 63 (3) ◽  
pp. 1028-1041 ◽  
Author(s):  
Richard S. Stolarski ◽  
Anne R. Douglass ◽  
Stephen Steenrod ◽  
Steven Pawson
Keyword(s):  
Time Series ◽  
Solar Cycle ◽  
Ultraviolet Radiation ◽  
Boundary Conditions ◽  
Interannual Variability ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Chemical Transport ◽  
Chemical Transport Model ◽  
The Past

Abstract Stratospheric ozone is affected by external factors such as chlorofluorcarbons (CFCs), volcanoes, and the 11-yr solar cycle variation of ultraviolet radiation. Dynamical variability due to the quasi-biennial oscillation and other factors also contribute to stratospheric ozone variability. A research focus during the past two decades has been to quantify the downward trend in ozone due to the increase in industrially produced CFCs. During the coming decades research will focus on detection and attribution of the expected recovery of ozone as the CFCs are slowly removed from the atmosphere. A chemical transport model (CTM) has been used to simulate stratospheric composition for the past 30 yr and the next 20 yr using 50 yr of winds and temperatures from a general circulation model (GCM). The simulation includes the solar cycle in ultraviolet radiation, a representation of aerosol surface areas based on observations including volcanic perturbations from El Chichon in 1982 and Pinatubo in 1991, and time-dependent mixing ratio boundary conditions for CFCs, halons, and other source gases such as N2O and CH4. A second CTM simulation was carried out for identical solar flux and boundary conditions but with constant “background” aerosol conditions. The GCM integration included an online ozonelike tracer with specified production and loss that was used to evaluate the effects of interannual variability in dynamics. Statistical time series analysis was applied to both observed and simulated ozone to examine the capability of the analyses for the determination of trends in ozone due to CFCs and to separate these trends from the solar cycle and volcanic effects in the atmosphere. The results point out several difficulties associated with the interpretation of time series analyses of atmospheric ozone data. In particular, it is shown that lengthening the dataset reduces the uncertainty in derived trend due to interannual dynamic variability. It is further shown that interannual variability can make it difficult to accurately assess the impact of a volcanic eruption, such as Pinatubo, on ozone. Such uncertainties make it difficult to obtain an early proof of ozone recovery in response to decreasing chlorine.

n-Alkanes and compound carbon isotope records from Lake Yiheshariwusu in the Hulun Buir sandy land, northeastern China

The Holocene ◽  
2020 ◽  
Vol 30 (10) ◽  
pp. 1451-1461
Author(s):  
Manman Xie ◽  
Qing Sun ◽  
Haowei Dong ◽  
Siwen Liu ◽  
Wenyu Shang ◽  
...  
Keyword(s):  
Time Series ◽  
Carbon Isotope ◽  
Summer Monsoon ◽  
Monsoon Rainfall ◽  
Eastern China ◽  
Carbon Number ◽  
C3 Plants ◽  
Sandy Land ◽  
The Holocene ◽  
Effective Precipitation

The Hulun Buir sandy land in northern China is located at the northern limit region of the East Asian summer monsoon (EASM) and is therefore sensitive to the extension of the front of the rainfall belt. Here we report an n-alkane and compound-specific carbon isotope record from the Holocene sediments of Lake Yiheshariwusu in the middle of the Hulun Buir sandy land. The sediments contain a suite of n-alkanes with a strong odd over even carbon number predominance, with the maximum contribution from nC31, which is a typical distribution in grassland regions. The low temperatures in this cold region greatly limit the growth of C4 plants and thus the long-chain n-alkanes in lake sediments are mainly derived from leaf wax lipids of C3 plants growing within the sandy land. In this C3-vegetation-dominated region, the δ13C27–33 value (weighted carbon isotope values of nC27– nC33) are regulated mainly by the physiological and biochemical responses of plants to water stress and are therefore interpreted as a proxy of effective precipitation or humidity. The δ13C27–33 time series shows a trend of gradually decreasing values that suggests an increase in effective precipitation since 8.5 ka (1 ka = 1000 cal yr BP). Relative droughts occurred during the intervals of 6.3–5.5, 4.1–3.6 ka, and during the last 200 years. In addition, the δ13C27–33 time series and comparable paleoenvironmental records from neighboring sites suggest opposite trends of summer monsoon rainfall between northeastern and southeastern China. We suggest that a coupled process between low and high latitudes (the western Pacific Subtropical High and the Okhotsk High) may have played a fundamental role in regulating the shift of the frontal rainfall belt and monsoon rainfall distribution in eastern China during the Holocene.

scholarly journals Variability in the speed of the Brewer–Dobson circulation as observed by Aura/MLS

2013 ◽  
Vol 13 (9) ◽  
pp. 4563-4575 ◽  
Author(s):  
T. Flury ◽  
D. L. Wu ◽  
W. G. Read
Keyword(s):  
Time Series ◽  
Interannual Variability ◽  
Lower Stratosphere ◽  
Meridional Circulation ◽  
Time Lag ◽  
Quasi Biennial Oscillation ◽  
One Year ◽  
The Tropics ◽  
Biennial Oscillation ◽  
Stratospheric Water Vapour

Abstract. We use Aura/MLS stratospheric water vapour (H2O) measurements as tracer for dynamics and infer interannual variations in the speed of the Brewer–Dobson circulation (BDC) from 2004 to 2011. We correlate one-year time series of H2O in the lower stratosphere at two subsequent pressure levels (68 hPa, ~18.8 km and 56 hPa, ~19.9 km at the Equator) and determine the time lag for best correlation. The same calculation is made on the horizontal on the 100 hPa (~16.6 km) level by correlating the H2O time series at the Equator with the ones at 40° N and 40° S. From these lag coefficients we derive the vertical and horizontal speeds of the BDC in the tropics and extra-tropics, respectively. We observe a clear interannual variability of the vertical and horizontal branch. The variability reflects signatures of the Quasi Biennial Oscillation (QBO). Our measurements confirm the QBO meridional circulation anomalies and show that the speed variations in the two branches of the BDC are out of phase and fairly well anti-correlated. Maximum ascent rates are found during the QBO easterly phase. We also find that transport of H2O towards the Northern Hemisphere (NH) is on the average two times faster than to the Southern Hemisphere (SH) with a mean speed of 1.15 m s−1 at 100 hPa. Furthermore, the speed towards the NH shows much more interannual variability with an amplitude of about 21% whilst the speed towards the SH varies by only 10%. An amplitude of 21% is also observed in the variability of the ascent rate at the Equator which is on the average 0.2 mm s−1.

scholarly journals Detecting Land Degradation in Eastern China Grasslands with Time Series Segmentation and Residual Trend analysis (TSS-RESTREND) and GIMMS NDVI3g Data

2019 ◽  
Vol 11 (9) ◽  
pp. 1014 ◽  
Author(s):  
Caixia Liu ◽  
John Melack ◽  
Ye Tian ◽  
Huabing Huang ◽  
Jinxiong Jiang ◽  
...  
Keyword(s):  
Time Series ◽  
Trend Analysis ◽  
Eastern China ◽  
Vegetation Changes ◽  
Natural Processes ◽  
Grassland Ecosystems ◽  
Time Series Segmentation ◽  
Breakpoint Detection ◽  
Ecosystem Changes ◽  
Gimms Ndvi3g

Grassland ecosystems in China have experienced degradation caused by natural processes and human activities. Time series segmentation and residual trend analysis (TSS-RESTREND) was applied to grasslands in eastern China. TSS-RESTREND is an extended version of the residual trend (RESTREND) methodology. It considers breakpoint detection to identify pixels with abrupt ecosystem changes which violate the assumptions of RESTREND. With TSS-RESTREND, in Xilingol (111°59′–120°00′E and 42°32′–46°41′E) and Hulunbuir (115°30′–122°E and 47°10′–51°23′N) grassland, 5.5% and 3.3% of the area experienced a decrease in greenness between 1984 and 2009, 80.2% and 73.2% had no significant change, 4.9% and 2.6% increased in greenness, and 9.4% and 20.9% were undetermined, respectively. RESTREND may underestimate the greening trend in Xilingol, but both TSS-RESTREND and RESTREND revealed no significant differences in Hulunbuir. The proposed TSS-RESTREND methodology captured both the time and magnitude of vegetation changes.

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