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Hefei, China

Li T.,CAS Institute of Atmospheric Physics | Zhang W.,CAS Institute of Atmospheric Physics | Zhang Q.,CAS Institute of Atmospheric Physics | Lu Y.,Anhui Climate Center | And 4 more authors.
Biogeosciences | Year: 2015

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 mg'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 mg'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 %. © Author(s) 2015. Source

Deng X.,Anhui Institute of Meteorology | Shi C.,Anhui Institute of Meteorology | Wu B.,Anhui Institute of Meteorology | Chen Z.,Guangxi University | And 3 more authors.
Atmospheric Research | Year: 2012

The characteristics of Aerosol Optical Depth (AOD) and Ångström exponent are analyzed and AODs are compared with CE318 measurements from 2001 to 2009 over Anhui province in China, with an evaluation of potential contributing factors, including regional burning emissions and meteorology. The result indicates that MODIS AODs (Collection 5, C005) are in good agreement with those from CE318 with correlation coefficient of above 0.80 and RMS of below 0.21 in Anhui. Most of MODIS cases fall in the range of Δτ. =. ±. 0.05. ±. 0.20τ at four AERONET sites. Aerosol optical properties show a notable spatial-temporal distribution feature in Anhui. The values of lower AOD and higher Ångström exponent both appear at southern mountain area. We document seasonal variations in patterns of AOD and Ångström exponent in Anhui, for which peak values respectively occur in June and August. Time series plots for AOD and fire pixel counts are produced to provide a better understanding of influence of burning emission for aerosol. Agricultural residue burning occurs seriously in June, which leads to appearance of AOD peak values. The results between AODs and meteorological parameters show good relationships at Fuyang. Wind speed and wind direction can strongly influence aerosol optical depth and its size, meanwhile, relative humidity and visibility respectively have positive and negative correlation with AODs. Mixed layer depths and AODs have similar monthly variation trend. We use HYSPLIT model for trajectory analysis to reveal the origins of air masses for different levels AODs and Ångström exponent, with the aim of discriminating contributions of different sources. © 2012 Elsevier B.V.. Source

Cao W.,Anhui Meteorological Institute | Cao W.,Anhui Province Atmospheric Science and Satellite Remote Sensing Key Laboratory | Duan C.F.,Anhui Climate Center | Shen S.H.,Nanjing University of Information Science and Technology
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2015

In the context of global warming, the impact of climate change on water resources is becoming increasingly significant and is thus drawing more attention. As a main component of the hydrological cycle, potential evapotranspiration (ET0) represents the maximum possible evaporation and is the rate of evaporation that would occur under given meteorological conditions from a continuously saturated surface. ET0 is essential for scheduling of irrigation system running times, preparing input data for hydrological models used in water balance studies, and assessing the hydrological impacts of the changing climate. Therefore, the trends of the changes in ET0 and its dominant factors across different regions of the world have been studied by many researchers in recent decades. Despite the global warming, decreasing trends in ET0have been detected in several countries, including the United States, Russia, India, China, Australia, and New Zealand. Decreasing sunshine hours, declining wind speed, and increasing relative humidity have been considered to be the main causes of the decreasing ET0.Analysis of the linear trend of the time series is frequently used in climate change research. The linear trend can reflect the overall trend of climate change over a time period, but it cannot describe the undulating character of climate change over a long time period. Thus, the characteristics of interdecadal turning of climatic factors, including air temperature, precipitation, and solar radiation, have become a topic of concern for many researchers worldwide.Thorough exploration of the interdecadal turning of ET0 trends can lead to a better understanding of the evolution and abrupt changes of ET0 related to climate change. Based on the FAO56 Penman-Monteith equation, interdecadal breakpoints in ET0 trends were studied using Tom- and Miranda’s climate-trend turning discriminatory model for 580 meteorological stations across China during 1971—2010. Differences in the trends and determining factors between the before and after breakpoint periods were also analyzed. The results showed that annual average ET0 decreased significantly (-2.46 mm/ a) before the 1990s but increased significantly (1.57 mm/ a) after the 1990s across China. This phenomenon was closely related to the interdecadal breakpoints in the trends of four meteorological factors affecting ET0 variations. The decrease in ET0 that occurred before the 1990s was attributed to a larger absolute value of the negative contributions caused by decreasing wind speed and sunshine duration compared to that of the positive contribution caused by increasing air temperature. After the 1990s, positive contribution from the air temperature and relative humidity increased due to the more intensive warming and climatic aridity across most of the areas in China and exceeded the smaller absolute value of the negative contribution from the wind speed and sunshine duration, causing the increasing trend in ET0. The interdecadal breakpoints existed at more than 80% of the meteorological stations across China, and there were differences between the pre-and post-breakpoint distribution patterns. Before the 1990s, wind speed and sunshine duration were the determining factors for most stations in North China and South China, respectively. After the 1990s, the number of stations with air temperature or relative humidity as a determining factor increased, especially in Northwest China, the Tibetan Plateau, and some parts of the southeastern coastal area. © 2015 Ecological Society of China. All rights reserved. Source

Li T.,CAS Institute of Atmospheric Physics | Zhang Q.,CAS Institute of Atmospheric Physics | Zhang W.,CAS Institute of Atmospheric Physics | Wang G.,CAS Institute of Atmospheric Physics | And 3 more authors.
PLoS ONE | Year: 2016

The Sanjiang Plain has been experienced significant wetland loss due to expanded agricultural activities, and will be potentially restored by the China National Wetland Conservation Action Plan (NWCP) in future. The objective of this study is to evaluate the impact of future climate warming and wetland restoration on wetland CH4 emissions in northeast China. We used an atmosphere-vegetation interaction model (AVIM2) to drive a modified biogeophysical model (CH4MODwetland ), and projected CH4 flux variations from the Sanjiang Plain wetlands under different Representative Concentration Pathway scenarios throughout the 21st century. Model validation showed that the regressions between the observed and simulated CH4 fluxes by the modified model produced an R2 of 0.49 with a slope of 0.87 (p<0.001, n = 237). According to the AVIM2 simulation, the net primary productivity of the Sanjiang Plain wetlands will increase by 38.2 g m-2 yr-1 , 116.6 g m-2 yr-1 and 250.4 g m-2 yr-1 under RCP 2.6, RCP 4.5 and RCP 8.5, respectively, by the end of this century. For RCP 2.6, 4.5 and 8.5 scenarios, the CH4 fluxes will increase by 5.7 g m-2 yr-1 , 57.5 g m-2 yr-1 and 112.2 gm-2 yr-1 . Combined with the wetland restoration, the regional emissions will increase by 0.18?1.52 Tg. The CH4 emissions will be stimulated by climate change and wetland restoration. Regional wetland restoration planning should be directed against different climate scenarios in order to suppress methane emissions.: © 2016 Li et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Duan C.,Nanjing University of Information Science and Technology | Duan C.,Anhui Climate Center | Miao Q.,Nanjing University of Information Science and Technology | Cao W.,Nanjing University of Information Science and Technology | Wang Y.,Nanjing University of Information Science and Technology
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2012

Reference crop evapotranspiration (ET ref) is a fundamental variable in the hydrological cycle. Accurate estimation of ET ref is essential to water resources project planning and farm irrigation scheduling. Based on the daily meteorological data from 123 climatic stations across Northwest China in the period of 1971-2000 and the reference crop evapotranspiration calculated by Penman-Monteith equation served as a standard, the 20 cm pan coefficient K p was estimated by relative humidity and wind speed. And K p model was respectively built and verified at different levels of single station, sub-region, and the whole study region. Results showed that there was a strong linear correlation between pan evaporation and reference crop evapotranspiration in Northwest China, and the correlation coefficients were 0.967. K p model for sub-region was more accuracy than that for the whole study region, and was more suitable than that for single station. Thus K p model for sub-region was recommend for estimating ET ref in large area. Source

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