Long-term variations of TN and TP in four lakes fed by Yangtze River at various timescales

2015 ◽  
Vol 74 (5) ◽  
pp. 3993-4009 ◽  
Author(s):  
Jian Huang ◽  
Xixi Wang ◽  
Beidou Xi ◽  
Qiujin Xu ◽  
Yan Tang ◽  
...  
Keyword(s):  
Yangtze River ◽  
Long Term Variations

scholarly journals Measurement report: Long-term variations in carbon monoxide at a background station in China's Yangtze River Delta region

2020 ◽  
Author(s):  
Yijing Chen ◽  
Qianli Ma ◽  
Weili Lin ◽  
Xiaobin Xu ◽  
Jie Yao ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Yangtze River ◽  
Yangtze River Delta ◽  
River Delta ◽  
Control Measures ◽  
Mixing Ratios ◽  
Significant Downward Trend ◽  
The Yrd ◽  
Long Term Variations

Abstract. This study analyzed the long-term variations in carbon monoxide (CO) mixing ratios from January 2006 to December 2017 at the Lin'an regional atmospheric background station (LAN; 30.3° N, 119.73° E, 138 m a.s.l.) in China's Yangtze River Delta (YRD) region. The CO mixing ratios were at their highest (0.69 ± 0.08 ppm) and lowest (0.54 ± 0.06 ppm) in winter and summer, respectively. The average daily variation of CO exhibited a double-peaked pattern, with peaks in the morning and evening and a valley in the afternoon. A significant downward trend of −11.3 ppb/yr of CO was observed from 2006 to 2017 at the LAN station, which was in accordance with the negative trend of the average CO mixing ratios and total column retrieved from the satellite data (the Measurements Of Pollution In The Troposphere, MOPITT) over the YRD region during the same period. The average annual CO mixing ratio at the LAN station in 2017 was 0.51 ± 0.04 ppm, which was significantly lower than that (0.71 ± 0.12 ppm) in 2006. The decrease in CO levels was largest in autumn (−15.7 ppb/yr), followed by summer (−11.1 ppb/yr), spring (−10.8 ppb/yr), and winter (−9.7 ppb/yr). Moreover, the CO levels under relatively polluted conditions (the annually 95th percentiles) declined even more rapidly (−22.4 ppb/yr, α = 0.05, r = −0.68) from 2006 (0.91 ppm) to 2017 (0.58 ppm) and the CO levels under clean conditions (the annually 5th percentiles) were relatively stable throughout the years. The long-term decline and short-term variations in the CO mixing ratios at the LAN station were mainly attributed to the implementation of the anthropogenic pollution control measures in the YRD region and to the events like Shanghai Expo in 2020 and Hangzhou G20 in 2016. The decreased CO level may influence atmospheric chemistry over the region. The average OH reactivity of CO at the LAN station is estimated to significantly drop from 4.1 ± 0.7 s-1 in 2006 to 3.0 ± 0.3 s-1 in 2017.

scholarly journals Measurement report: Long-term variations in carbon monoxide at a background station in China's Yangtze River Delta region

2020 ◽  
Vol 20 (24) ◽  
pp. 15969-15982
Author(s):  
Yijing Chen ◽  
Qianli Ma ◽  
Weili Lin ◽  
Xiaobin Xu ◽  
Jie Yao ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Yangtze River ◽  
Yangtze River Delta ◽  
River Delta ◽  
Control Measures ◽  
Mixing Ratios ◽  
Significant Downward Trend ◽  
The Yrd ◽  
Long Term Variations

Abstract. This study analyzed the long-term variations in carbon monoxide (CO) mixing ratios from January 2006 to December 2017 at the Lin'an regional atmospheric background station (LAN; 30.3∘ N, 119.73∘ E, 138 m a.s.l.) in China's Yangtze River Delta (YRD) region. The CO mixing ratios were at their highest (0.69 ± 0.08 ppm) and lowest (0.54 ± 0.06 ppm) in winter and summer, respectively. The average daily variation in CO exhibited a double-peaked pattern, with peaks in the morning and evening and a valley in the afternoon. A significant downward trend of −11.3 ppb yr−1 of CO was observed from 2006 to 2017 at the LAN station, which was in accordance with the negative trends of the average CO mixing ratios and total column retrieved from the satellite data (Measurements of Pollution in the Troposphere, MOPITT) over the YRD region during the same period. The average annual CO mixing ratio at the LAN station in 2017 was 0.51 ± 0.04 ppm, which was significantly lower than that (0.71 ± 0.12 ppm) in 2006. The decrease in CO levels was largest in autumn (−15.7 ppb yr−1), followed by summer (−11.1 ppb yr−1), spring (−10.8 ppb yr−1), and winter (−9.7 ppb yr−1). Moreover, the CO levels under relatively polluted conditions (the annual 95th percentiles) declined even more rapidly (−22.4 ppb yr−1, r=-0.68, p<0.05) from 2006 (0.91 ppm) to 2017 (0.58 ppm), and the CO levels under clean conditions (the annual 5th percentiles) showed decreasing evidence but not statistically significant (r=-0.41, p=0.19) throughout the years. The long-term decline and short-term variations in the CO mixing ratios at the LAN station were mainly attributed to the implementation of the anthropogenic pollution control measures in the YRD region and to events like the Shanghai Expo in 2010 and Hangzhou G20 in 2016. The decreased CO level may influence atmospheric chemistry over the region. The average OH reactivity of CO at the LAN station is estimated to significantly drop from 4.1 ± 0.7 s−1 in 2006 to 3.0 ± 0.3 s−1 in 2017.

scholarly journals Measurement report: Long-term variations in surface NO<sub>x</sub> and SO<sub>2</sub> from 2006 to 2016 at a background site in the Yangtze River Delta region, China

2021 ◽  
Author(s):  
Qingqing Yin ◽  
Qianli Ma ◽  
Weili Lin ◽  
Xiaobin Xu ◽  
Jie Yao
Keyword(s):  
Yangtze River ◽  
Yangtze River Delta ◽  
Mixing Ratio ◽  
So2 Emissions ◽  
Annual Average ◽  
Mixing Ratios ◽  
The Yrd ◽  
The Yangtze River Delta ◽  
Long Term Variations

Abstract. China has been experiencing rapid changes in emissions of air pollutants in recent decades. Increased emissions of primary particulates and reactive gases caused severe haze in several polluted regions including the Yangtze River Delta (YRD). Measures implemented in recent years for improving air quality have reduced the emissions of NOX, SO2, etc. The emission changes of these gases are reflected by tropospheric columns from satellite observations and surface measurements of surface concentrations from urban sites. However, little is known about the long-term variations in regional background NOX and SO2. In this study, we present NOX and SO2 measurements from the Lin'an station (LAN, 119°44' E,30°18' N,138.6 m a.s.l.), one of the Global Atmosphere Watch (GAW) stations in China. We characterize the seasonal and diurnal variations and study the long-term trends of NOX and SO2 mixing ratios observed at LAN from 2006 to 2016. We also interpret the observed variations and trends in term of changes in meteorological conditions as well as emission of these gases. The overall average mixing ratios of NOX and SO2 during 2006–2016 were 13.6 ± 1.2 ppb and 7.0 ± 4.2 ppb, respectively. The averaged seasonal variations showed maximum values of NOx and SO2 in December (23.5 ± 4.4 ppb) and January (11.9 ± 6.2 ppb), respectively, and minimum values of 7.1 ± 0.8 ppb and 2.8 ± 2.3 ppb (both in July), respectively. The average diurnal variation characteristics of NOX and SO2 differed considerably from each other though the daily average mixing ratios of both gases were significantly correlated (R2 = 0.29, P < 0.001). The annual average mixing ratio of NOX increased during 2006–2011 and then decreased significantly at 0.78 ppb/yr (−5.16 %/yr, P < 0.01). The annual 95 % and 5 % percentiles of hourly NOX mixing ratios showed upward trends until 2012 and 2014, respectively, before a clear decline. The annual average mixing ratio of SO2 decreased significantly at 0.99 ppb/yr (−8.27 %/yr, P < 0.01) from 2006–2016. The annual 95 % and 5 % percentiles of hourly SO2 mixing ratios all exhibited significant (P < 0.001) downward trends at 3.18 ppb/yr and 0.19 ppb/yr, respectively. Changes in the total NOX and SO2 emissions as well as the industrial emissions in the YRD region were significantly correlated with the changes in annual NOX and SO2 mixing ratios. The significant decreases in NOX from 2011 to 2016 and SO2 from 2006 to 2016 highlight the effectiveness of relevant control measures on the reduction in NOX and SO2 emissions in the YRD region. A decrease of annual S / N ratio was found, suggesting a better efficacy in the emission reduction of SO2 than NOX. We found gradual changes in average diurnal patterns of NOX and SO2, which could be attributed to increasing contributions of vehicle emissions to NOX and weakening impacts of large sources on the SO2 concentration. This study reaffirms China's success in controlling both NOX and SO2 in the YRD but indicate at the same time a necessity to strengthen the NOX emission control.

Fluvial magnetic susceptibility as a proxy for long‐term variations of mountain permafrost development in the Alp‐Carpathian region

Boreas ◽  
2021 ◽  
Author(s):  
Zoltán Püspöki ◽  
Philip Leonard Gibbard ◽  
Annamária Nádor ◽  
Edit Thamó‐Bozsó ◽  
Pál Sümegi ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Carpathian Region ◽  
Mountain Permafrost ◽  
Long Term Variations

Long-term variations of surface solar radiation in China from routine meteorological observations

2021 ◽  
pp. 105715
Author(s):  
Xuefang Yang ◽  
Wenmin Qin ◽  
Lunche Wang ◽  
Ming Zhang ◽  
Zigeng Niu
Keyword(s):  
Solar Radiation ◽  
Surface Solar Radiation ◽  
Meteorological Observations ◽  
Long Term Variations

Long-term variations of C1–C5 alkyl nitrates and their sources in Hong Kong

2021 ◽  
Vol 270 ◽  
pp. 116285
Author(s):  
Lewei Zeng ◽  
Hai Guo ◽  
Xiaopu Lyu ◽  
Beining Zhou ◽  
Zhenhao Ling ◽  
...  
Keyword(s):  
Hong Kong ◽  
Alkyl Nitrates ◽  
Long Term Variations

Application of singular spectrum analysis in reconstruction of the annual signal from GRACE

2020 ◽  
Vol 14 (3) ◽  
pp. 295-302
Author(s):  
Chuandong Zhu ◽  
Wei Zhan ◽  
Jinzhao Liu ◽  
Ming Chen
Keyword(s):  
Time Series ◽  
Spectrum Analysis ◽  
Singular Spectrum Analysis ◽  
Mixture Effect ◽  
Singular Spectrum ◽  
Grace Data ◽  
Terrestrial Water ◽  
Annual Signal ◽  
Long Term Variations

AbstractThe mixture effect of the long-term variations is a main challenge in single channel singular spectrum analysis (SSA) for the reconstruction of the annual signal from GRACE data. In this paper, a nonlinear long-term variations deduction method is used to improve the accuracy of annual signal reconstructed from GRACE data using SSA. Our method can identify and eliminate the nonlinear long-term variations of the equivalent water height time series recovered from GRACE. Therefore the mixture effect of the long-term variations can be avoided in the annual modes of SSA. For the global terrestrial water recovered from GRACE, the peak to peak value of the annual signal is between 1.4 cm and 126.9 cm, with an average of 11.7 cm. After the long-term and the annual term have been deducted, the standard deviation of residual time series is between 0.9 cm and 9.9 cm, with an average of 2.1 cm. Compared with the traditional least squares fitting method, our method can reflect the dynamic change of the annual signal in global terrestrial water, more accurately with an uncertainty of between 0.3 cm and 2.9 cm.

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