| 1. |
- An, Dong, et al.
(författare)
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Evidence of climate shift for temperature and precipitation extremes across Gansu Province in China
- 2020
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Ingår i: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 1434-4483 .- 0177-798X. ; 139:3-4, s. 1137-1149
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Tidskriftsartikel (refereegranskat)abstract
- Temperature and precipitation extremes are the dominant causes of natural disasters. In this study, seven indices of extreme temperature and precipitation events in Gansu Province, China, were analysed for the period 1961–2017. An abrupt climate shift was recorded during 1980–1981. Thus, the study period was divided into a preshift (before the climate shift) period 1961–1980 and an aftshift (after the climate shift) period 1981–2017. Comparison of mean extreme indices for preshift and aftshift periods was performed for the purpose of exploring possible increasing/decreasing patterns. Generalized extreme value (GEV) distribution was applied spatially to fit the extreme indices with return periods up to 100 years for preshift/aftshift periods. Singular value decomposition (SVD) was adopted to investigate possible correlation between the extreme climate events and indices of large-scale atmospheric circulation. The results indicate that changes in mean and return levels between the preshift and aftshift periods vary significantly in time and space for different extreme indices. Increase in extreme temperature regarding magnitude and frequency for the aftshift period as compared with the preshift period suggests a change to a warmer and more extreme climate during recent years. Changes in precipitation extremes were different in southern and northern parts of Gansu. The precipitation extremes in the north have increased that can result in more serious floods and droughts in the future. SVD analyses revealed a complex pattern of correlation between climate extremes and indices of large-scale atmospheric circulation. Strengthening of westerlies and weakening of the south summer monsoon contribute to the complex changing patterns of precipitation extremes. Results in this study will contribute to disaster risk prevention and better water management in this area.
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| 2. |
- du, Yiheng, et al.
(författare)
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Integrated large‐scale circulation impact on rainy season precipitation in the source region of the Yangtze River
- 2020
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Ingår i: International Journal of Climatology. - : Wiley. - 1097-0088 .- 0899-8418. ; 40:4, s. 2285-2295
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Tidskriftsartikel (refereegranskat)abstract
- Monthly precipitation data at regular grids of 0.5° × 0.5° derived from observations during June–August 1961–2016 were used to reveal characteristics of large‐scale circulations associated with rainy season precipitation over the source region of the Yangtze River (SRYR). The integrated impact of major influencing circulation patterns was examined by principal component analysis and composites. Results showed that the first rainy season precipitation mode associates with the Southern Oscillation Index (SOI) and the Pacific Decadal Oscillation (PDO), explaining 64% of spatial and temporal rainy season precipitation variance in the region. Composites of precipitation pattern under different phases of SOI and PDO revealed that the effect of PDO on precipitation varies with the SOI phase. When out of phase with the SOI, PDO‐induced precipitation anomalies are magnified. When they are in phase, anomalies weaken or even disappear. Composites of moisture flux patterns show that large‐scale atmospheric circulation affects the strength of westerlies that transport moisture to the study area and formation of convergence. In coming decades, the PDO is likely to continue in a negative phase with La Niña (positive SOI) events, implying more precipitation during the rainy season. Consequently, this knowledge can be used to improve decision making regarding water supply and flood risk management in the SRYR.
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| 3. |
- Zhu, Siyu, et al.
(författare)
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Water level fluctuation induced variation of sulfamethazine biogeochemical behavior and expression of resistance genes in the hyporheic zone: A case study of Chaobai river, China
- 2023
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Konferensbidrag (refereegranskat)abstract
- It is well known that the intensive biogeochemical activity in hyporheic zone of groundwater and antibiotic contaminated river water induced the pollution diffusion and variation of biogeochemical transformation. However, the complex interaction process caused by water level fluctuation is difficult to accurately depict on a larger, catchment scale. Therefore, a loosely coupled HYDRUS-3D/GMS was established in Chaobai river basin to simulate the sulfamethazine (SMZ) pollution interaction process caused by river and groundwater level fluctuation. The upward fluctuation of river water level increased the migration of SMZ from surface water to the hyporheic zone soil and groundwater with the rate of 3.04 m/(y·m), which accelerated the pollution diffusion. Moreover, the rise of river water level reduced DO and ORP in hyporheic zone, which induced the biochemical transformation of SMZ from aerobic to anoxic and anaerobic, thus reduced 25% decomposition rate and increasing 7 times expression of resistance genes. The expression of ARGs sul1, sul2, sul3 were positively correlated with the SMZ concentration with coefficient of 0.9954, 0.9856, 0.9689. The biogeochemical behavior of SMZ was completely opposite when the river water level fell back in the dry season compared with that of water level rising, which contributed to the decomposition of accumulative antibiotics in the hyporheic zone. However, the upward fluctuation of groundwater table led to the secondary release of 20% SMZ accumulated in hyporheic zone soil and the reverse interaction of river water pollution, which induced increase in the abundance of resistant bacteria, thereby enhancing the expression intensity of ARGs. In addition, the accumulation and diffusion of SMZ were also closely related to soil physicochemical properties (P<0.01 to BET; P<0.001 to TOC) and microbial community structure during the interaction between groundwater and surface water in hyporheic zone. The accumulation of SMZ increased the ecological risk and induced the variation of microbial community structure and relative abundance. The enrichment of these antibiotic degrading genera, Hyphomicrobium, Thermomonas and Comamondaceae, improve the degradation of antibiotics and enhanced the expression of resistance genes sul1 and sul2, which increased the risk of drug resistance of superbacteria. This study provided a new approach to predict the variation of SMZ biogeochemical behavior and expression of resistance genes in the hyporheic zone due to water level fluctuation, which can effectively improve removal technologies and the drinking safety of groundwater.
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