scholarly journals Impacts of climate and reclamation on temporal variations in CH<sub>4</sub> emissions from different wetlands in China: from 1950 to 2010

2015 ◽  
Vol 12 (23) ◽  
pp. 6853-6868 ◽  
Author(s):  
T. Li ◽  
W. Zhang ◽  
Q. Zhang ◽  
Y. Lu ◽  
G. Wang ◽  
...  
Keyword(s):  
Climate Warming ◽  
Coastal Wetlands ◽  
Temporal Variations ◽  
Tibet Plateau ◽  
Atmospheric Methane ◽  
Temporal And Spatial Variations ◽  
Ch4 Emissions ◽  
Natural Wetlands ◽  
Temporal And Spatial ◽  
Qinghai Tibet Plateau

Abstract. Natural wetlands are among the most important sources of atmospheric methane and thus important for better understanding the long-term temporal variations in the atmospheric methane concentration. During the last 60 years, wetlands have experienced extensive conversion and impacts from climate warming which might result in complicated temporal and spatial variations in the changes of the wetland methane emissions. In this paper, we present a modeling framework, integrating CH4MODwetland, TOPMODEL, and TEM models, to analyze the temporal and spatial variations in CH4 emissions from natural wetlands (including inland marshes/swamps, coastal wetlands, lakes, and rivers) in China. Our analysis revealed a total increase of 25.5 %, averaging 0.52 g m−2 per decade, in the national CH4 fluxes from 1950 to 2010, which was mainly induced by climate warming. Larger CH4 flux increases occurred in northeastern, northern, and northwestern China, where there have been higher temperature rises. However, decreases in precipitation due to climate warming offset the increment of CH4 fluxes in these regions. The CH4 fluxes from the wetland on the Qinghai–Tibet Plateau exhibited the lowest CH4 increase (0.17 g m−2 per decade). Although climate warming has accelerated CH4 fluxes, the total amount of national CH4 emissions decreased by approximately 2.35 Tg (1.91–2.81 Tg), i.e., from 4.50 Tg in the early 1950s to 2.15 Tg in the late 2000s, due to the wetland loss totalling 17.0 million ha. Of this reduction, 0.26 Tg (0.24–0.28 Tg) was derived from lakes and rivers, 0.16 Tg (0.13–0.20 Tg) from coastal wetlands, and 1.92 Tg (1.54–2.33 Tg) from inland wetlands. Spatially, northeastern China contributed the most to the total reduction, with a loss of 1.68 Tg. The wetland CH4 emissions reduced by more than half in most regions in China except for the Qinghai–Tibet Plateau, where the CH4 decrease was only 23.3 %.

scholarly journals Impacts of climate and reclamation on temporal variations in CH<sub>4</sub> emissions from different wetlands in China: from 1950 to 2010

2015 ◽  
Vol 12 (9) ◽  
pp. 7055-7091 ◽  
Author(s):  
T. Li ◽  
W. Zhang ◽  
Q. Zhang ◽  
Y. Lu ◽  
G. Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Climate Warming ◽  
Coastal Wetlands ◽  
Temporal Variations ◽  
Northeastern China ◽  
Large Temperature ◽  
Modeling Framework ◽  
Ch4 Emissions ◽  
Inland Wetlands ◽  
Natural Wetlands

Abstract. Natural wetlands are among the most important sources of methane; thus, these areas are important for better understanding long-term temporal variations in atmospheric methane concentration. During the last 60 years, wetlands have experienced extensive conversion and global impacts from climate warming, which makes the estimation of methane emission from wetlands highly uncertain. In this paper, we present a modeling framework, integrating CH4MODwetland, TOPMODEL and TEM models, to analyze the temporal and spatial variations in CH4 emissions from natural wetlands (including inland wetlands, coastal wetlands, lakes and rivers) in China. Our analysis revealed an increase of 25.5%, averaging 0.52 g m−2 per decade, in national CH4 fluxes from 1950 to 2010, which was mainly induced by climate warming. Higher rates of increasing CH4 fluxes occurred in northeastern, northern and northwestern China, associated with large temperature increases. However, decreases in precipitation due to climate warming offset the increase in CH4 fluxes in these regions. The CH4 fluxes from the wetland on the Qinghai Tibetan Plateau exhibited a lower rate of increase, which was approximately 25% of that simulated in northeastern China. Although climate warming has accelerated CH4 fluxes, the total amount of national CH4 emissions decreased by approximately 2.35 Tg (1.91–2.81 Tg), i.e., from 4.50 Tg in the early 1950s to 2.15 Tg in the late 2000s, due to a large wetland loss of 17.0 million ha. Of this reduction, 0.26 Tg (0.24–0.28 Tg) was derived from lakes and rivers, 0.16 Tg (0.13–0.20 Tg) from coastal wetlands, and 1.92 Tg (1.54–2.33 Tg) from inland wetlands. Northeastern China had the largest contribution to this reduction, with a loss of 1.68 Tg. The CH4 emissions were reduced by more than half in most regions in China except for the Qinghai Tibetan Plateau, where only a 23.3% decrease in CH4 was observed.

scholarly journals Methane emissions by alpine plant communities in the Qinghai–Tibet Plateau

2008 ◽  
Vol 4 (6) ◽  
pp. 681-684 ◽  
Author(s):  
Guangmin Cao ◽  
Xingliang Xu ◽  
Ruijun Long ◽  
Qilan Wang ◽  
Changting Wang ◽  
...  
Keyword(s):  
Plant Communities ◽  
Methane Emissions ◽  
Tibet Plateau ◽  
The Tibetan Plateau ◽  
Atmospheric Methane ◽  
Closed Chamber ◽  
Methane Budget ◽  
Alpine Plant Communities ◽  
Regional Basis ◽  
Qinghai Tibet Plateau

For the first time to our knowledge, we report here methane emissions by plant communities in alpine ecosystems in the Qinghai–Tibet Plateau. This has been achieved through long-term field observations from June 2003 to July 2006 using a closed chamber technique. Strong methane emission at the rate of 26.2±1.2 and 7.8±1.1 μg CH 4 m −2  h −1 was observed for a grass community in a Kobresia humilis meadow and a Potentilla fruticosa meadow, respectively. A shrub community in the Potentilla meadow consumed atmospheric methane at the rate of 5.8±1.3 μg CH 4 m −2  h −1 on a regional basis; plants from alpine meadows contribute at least 0.13 Tg CH 4 yr −1 in the Tibetan Plateau. This finding has important implications with regard to the regional methane budget and species-level difference should be considered when assessing methane emissions by plants.

scholarly journals Temporal and Spatial Variations of Atmospheric Radiocarbon in the Mexico City Metropolitan Area

Radiocarbon ◽  
2015 ◽  
Vol 57 (3) ◽  
pp. 363-375 ◽  
Author(s):  
Laura Beramendi-Orosco ◽  
Galia Gonzalez-Hernandez ◽  
Adriana Martinez-Jurado ◽  
Angeles Martinez-Reyes ◽  
Alfonso Garcia-Samano ◽  
...  
Keyword(s):  
Mexico City ◽  
Metropolitan Area ◽  
Forest Fires ◽  
Fossil Fuels ◽  
Complex Mixture ◽  
Temporal Variations ◽  
Spatial Variations ◽  
Temporal And Spatial Variations ◽  
C Cycle ◽  
Temporal And Spatial

The Mexico City Metropolitan Area (MCMA) produces a complex mixture of gases and aerosols from diverse sources, including burning of fossil fuels, biomass, and wastes, with a significant biogenic contribution. We present the first results of ongoing projects to study temporal and spatial variations of 14CO2 in the area. Temporal variations reconstructed from tree rings of Taxodium mucronatum indicate a considerable radiocarbon depletion, in accordance to the vast amount of fossil fuels burnt inside Mexico Valley, with values between 62 and 246‰ lower than background values for the 1962–1968 period, and lower by 51–88‰ for the 1983–2010 period. The lower dilution found for the last decades might indicate an increase in enriched 14CO2 sources. Results from the spatial distribution, as revealed from integrated CO2 samples and grasses from six points within the MCMA collected during the 2013 dry season, show variations between sites and sample types. For integrated CO2 samples, values range from 35.6‰ to 54.0‰, and for grasses between −86.8‰ and 40.7‰. For three of the sampling points, the grasses are significantly depleted, by up to ∼133‰, as compared to the corresponding integrated CO2 sample. This may result from differences in the carbon assimilation period and exposure to different CO2 sources. Higher-than-background Δ14C values were found for all integrated CO2 samples, presumably resulting from 14C-enriched CO2 derived from forest fires in the mountains during the sampling period. Results obtained so far confirm the complexity of the 14C cycle in the MCMA.

scholarly journals Analysis on the Temporal and Spatial Characteristics of the Shallow Soil Temperature of the Qinghai-Tibet Plateau

2021 ◽  
Author(s):  
Yujie Li ◽  
Cunjie Zhang ◽  
Zhenchao Li ◽  
Liwei Yang ◽  
Xiao Jin ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Observational Data ◽  
Temperature Increase ◽  
Soil Layer ◽  
Tibet Plateau ◽  
Shallow Soil ◽  
Increasing Trend ◽  
Temporal And Spatial ◽  
Region 10 ◽  
Qinghai Tibet Plateau

Abstract Shallow soil refers to the soil layer within 50 cm underground. Shallow soil temperature (ST) affects many processes that occur in the soil. Therefore, the study of shallow ST is of great significance in understanding energy, hydrological cycles and climate change. This work collected the observational data from 141 meteorological stations on the Qinghai-Tibet Plateau from 1981 to 2020, analyzed the ST as well as its temporal and spatial change characteristics at different levels. The results show that: 1) The shallow ST has a gradually increasing trend from north to south, from west to east. From the perspective of time characteristics, the increasing trend is obvious. The temperature increase of 0–20 cm (the surface layer of the shallow soil) is roughly the same. The average annual is 9.15–9.57 ℃, the interdecadal variabilities are 0.49–0.53 K/10a. The average annual of 40 cm (the bottom layer) is 8.69 ℃, the interdecadal variability reaches by 0.98 K/10a; 2) Judging from the 12 regions of 20 cm, the temperature increase trend is obvious, but there are certain regional differences. The average value ranges from 4.3 ℃ (region 4, Qaidam Plateau) to 18.1 ℃ (region 10, Southeast Qinghai-Tibet Plateau), the difference is nearly 14 K. The standard deviation ranges from 0.38 K (region 10) to 0.82 K (region 11, Northern Qiangtang Plateau); 3) The results of the reanalysis data are lower than the observational data. This work is significant for understanding the characteristics of the ST evolution and the land-atmosphere interaction on the Qinghai-Tibet Plateau.

scholarly journals Evaluation of SMAP, SMOS-IC, FY3B, JAXA, and LPRM Soil Moisture Products over the Qinghai-Tibet Plateau and Its Surrounding Areas

2019 ◽  
Vol 11 (7) ◽  
pp. 792 ◽  
Author(s):  
Jin Liu ◽  
Linna Chai ◽  
Zheng Lu ◽  
Shaomin Liu ◽  
Yuquan Qu ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Regional Scale ◽  
Temporal Variations ◽  
Comparison Method ◽  
Tibet Plateau ◽  
Quantitative Evidence ◽  
Retrieval Algorithms ◽  
Qinghai Tibet Plateau

High-quality and long time-series soil moisture (SM) data are increasingly required for the Qinghai-Tibet Plateau (QTP) to more accurately and effectively assess climate change. In this study, to evaluate the accuracy and effectiveness of SM data, five passive microwave remotely sensed SM products are collected over the QTP, including those from the soil moisture active passive (SMAP), soil moisture and ocean salinity INRA-CESBIO (SMOS-IC), Fengyun-3B microwave radiation image (FY3B), and two SM products derived from the advanced microwave scanning radiometer 2 (AMSR2). The two AMSR2 products are generated by the land parameter retrieval model (LPRM) and the Japan Aerospace Exploration Agency (JAXA) algorithm, respectively. The SM products are evaluated through a two-stage data comparison method. The first stage is direct validation at the grid scale. Five SM products are compared with corresponding in situ measurements at five in situ networks, including Heihe, Naqu, Pali, Maqu, and Ngari. Another stage is indirect validation at the regional scale, where the uncertainties of the data are quantified by using a three-cornered hat (TCH) method. The results at the regional scale indicate that soil moisture is underestimated by JAXA and overestimated by LPRM, some noise is contained in temporal variations in SMOS-IC, and FY3B has relatively low absolute accuracy. The uncertainty of SMAP is the lowest among the five products over the entire QTP. In the SM map composed by five SM products with the lowest pixel-level uncertainty, 66.64% of the area is covered by SMAP (JAXA: 19.39%, FY3B: 10.83%, LPRM: 2.11%, and SMOS-IC: 1.03%). This study reveals some of the reasons for the different performances of these five SM products, mainly from the perspective of the parameterization schemes of their corresponding retrieval algorithms. Specifically, the parameterization configurations and corresponding input datasets, including the land-surface temperature, the vegetation optical depth, and the soil dielectric mixing model are analyzed and discussed. This study provides quantitative evidence to better understand the uncertainties of SM products and explain errors that originate from the retrieval algorithms.

scholarly journals Spatial and Temporal Variations in the Rainy Season Onset over the Qinghai–Tibet Plateau

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1960 ◽  
Author(s):  
Hu ◽  
Xu ◽  
Huang ◽  
Zhou ◽  
Pang ◽  
...  
Keyword(s):  
Rainy Season ◽  
Asian Monsoon ◽  
East Asian Monsoon ◽  
Regional Climate ◽  
Kendall Test ◽  
Temporal Variations ◽  
Spatial And Temporal Variations ◽  
Tibet Plateau ◽  
Transport Channel ◽  
Qinghai Tibet Plateau

Precipitation on the Qinghai–Tibet Plateau (TP) in southwestern China is subject to interactions between the complex and variable terrain and the sensitive climate. The regional climate is mainly affected by three circulations: westerlies, the South Asian monsoon, and the East Asian monsoon. Spatial and temporal variations in the rainy season onset were characterised based on daily precipitation from 106 meteorological stations on the TP from 1971 to 2015. Using the Theil–Sen Median trend analysis, Mann–Kendall test and mutation detection, the characteristics and reasons for the variations during the rainy season over the plateau over the past 45 years were investigated. The following results were obtained from the analysis: (1) There were obvious regional differences in the rainy season onset over the TP, and the rainy season began on the southeastern plateau and moved northwestward. (2) The TP rainy season underwent a significant mutation in approximately 1997, and following this mutation, the area affected by the delayed rainy season increased. (3) Against the background of global warming, the rainy season trend over the TP was advanced; however, there were still several multiple contiguous concentrated areas on the plateau. (4) Before the rainy season mutation, there were two centres of delayed precipitation on the plateau, which existed primarily due to their location at the end of the plateau water vapour transport channel. After the mutation, the number of delayed precipitation centres on the plateau increased to three and presented a spatially expanding trend, which may be related to the weakening trend in atmospheric circulation.

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