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Qu X.,CAS Institute of Atmospheric Physics | Qu X.,Plateau Atmosphere and Environment Key Laboratory of Sichuan Province | Huang G.,Chinese Academy of Sciences | Huang G.,Nanjing University of Information Science and Technology | And 7 more authors.
Theoretical and Applied Climatology | Year: 2014

The South Asian high (SAH) is a huge anticyclone in the upper troposphere. It influences the climate and the distribution of trace constituents and pollutants. The present study documents the change in the SAH and precipitation under global warming, as well as the possible link between the changes, based on 17 Coupled Model Intercomparison Project Phase 5 (CMIP5) model simulations. The CMIP5 historical simulation reproduces reasonably the tropospheric circulation (including the SAH), precipitation, and moisture. Under global warming, more than 75 % of the CMIP5 models project a southward shift of the SAH. The southward shift is more significant in the models with stronger anticyclonic circulation in the south part of the climatological SAH. The precipitation response displays a contrasting feature: negative over the southeastern equatorial Indian Ocean (IO) and positive over the tropical northern IO, the Bay of Bengal, and the equatorial western Pacific. The results of a linear baroclinic model (LBM) show that the regional rainfall changes over the Bay of Bengal and the equatorial western Pacific have a main contribution to the southward shift of the SAH. In addition, the precipitation and the surface wind responses over the Indo-Pacific region are well coupled. On one hand, the surface wind anomaly affects the rainfall response through altering the SST and moisture. On the other hand, the condensational heating released by regional rainfall changes sustains the surface wind response. © 2014 Springer-Verlag Wien. Source


Qu X.,CAS Institute of Atmospheric Physics | Qu X.,Plateau Atmosphere and Environment Key Laboratory of Sichuan Province | Huang G.,CAS Institute of Atmospheric Physics | Huang G.,Nanjing University of Information Science and Technology | Zhou W.,City University of Hong Kong
Theoretical and Applied Climatology | Year: 2014

East Asia summer rainfall is of great social-economic importance. Based on observations, reanalysis and simulations of 16 Coupled Models Intercomparison Project phase 5 (CMIP5) models, the responses of East Asia summer precipitation, as well as some relevant features, to global warming are investigated. The CMIP5 historical simulation reasonably reproduces the climatology of summer rainfall, the associated circulation, the moisture and its transportation, and the mid-troposphere horizontal advection of temperature as well. Under global warming, the rainfall enhancement is robustly projected in the state-of-the-art models over North China, Northeast China, northern coast of Japan and the Kuroshio. As well, the total summer rainfall over East Asia is consistently increased in the models. For the consistent responses, the moisture budget analysis based on the simulations shows that two factors are responsible: one is increased moisture. As East Asia is a climatological ascent region in northern summer, increased moisture induced by global warming leads to more moisture transported upward and thus the rainfall rise. The other is enhanced evaporation, which may be caused by surface warming and provides more precipitable water to the atmosphere column. Furthermore, the results may provide some implications to the long-term variability of East Asia summer rainfall over the last several decades. © Springer-Verlag Wien 2013. Source


Qu X.,CAS Institute of Atmospheric Physics | Qu X.,Plateau Atmosphere and Environment Key Laboratory of Sichuan Province | Huang G.,Chinese Academy of Sciences | Huang G.,Nanjing University of Information Science and Technology | Zhou W.,City University of Hong Kong
Theoretical and Applied Climatology | Year: 2013

East Asia summer rainfall is of great social-economic importance. Based on observations, reanalysis and simulations of 16 Coupled Models Intercomparison Project phase 5 (CMIP5) models, the responses of East Asia summer precipitation, as well as some relevant features, to global warming are investigated. The CMIP5 historical simulation reasonably reproduces the climatology of summer rainfall, the associated circulation, the moisture and its transportation, and the mid-troposphere horizontal advection of temperature as well. Under global warming, the rainfall enhancement is robustly projected in the state-of-the-art models over North China, Northeast China, northern coast of Japan and the Kuroshio. As well, the total summer rainfall over East Asia is consistently increased in the models. For the consistent responses, the moisture budget analysis based on the simulations shows that two factors are responsible: one is increased moisture. As East Asia is a climatological ascent region in northern summer, increased moisture induced by global warming leads to more moisture transported upward and thus the rainfall rise. The other is enhanced evaporation, which may be caused by surface warming and provides more precipitable water to the atmosphere column. Furthermore, the results may provide some implications to the long-term variability of East Asia summer rainfall over the last several decades. © 2013 Springer-Verlag Wien. Source


Lu X.,Chengdu University of Information Technology | Lu X.,Plateau Atmosphere and Environment Key Laboratory of Sichuan Province | Lu X.,Chengdu University of Technology | Zhang J.,Chengdu University of Information Technology | And 5 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2016

As one of the most active regions in the world, the Yellow River Delta has a large-area wetland which plays a significant role in balancing the regional eco-environment. However, in the past decades, increasingly severe natural and human environment have formed great threat to the Yellow River Delta wetland. Researches are urged to make clear what exactly has changed and which factors exactly result in it in order to put forward the measures of instructions on regional wetland protection. Therefore, a wetland landscape database that contained 9 land use maps of the Yellow River Delta in the year 1973, 1979, 1985, 1992, 1995, 2000, 2005, 2010 and 2013 was constructed with artificial visual interpretation as method and Landsat-MSS/TM/ETM/OLI satellite images as data source. Combined with the Yellow River runoff and sediment data, socioeconomic data, the Yellow River Delta wetland evolution and its driving factors were analyzed. Researches showed that: 1) Natural wetland was the primary wetland of the Yellow River Delta, among which saltwater wetlands accounted for the larger proportion. However, different natural wetland types had different distribution feature: saltwater wetlands had an evolution sequence from sea to land, while freshwater wetland had an evolution sequence by the distance to the Yellow River. Active and widely distributed, the tidal creek played good corridor function, and dominated the landscape distribution and evolution. 2) The wetland area of the Yellow River Delta experienced an overall decline during 1973-2013, and showed an overall fragmentation trend, accompanied with large scale natural wetland converting to artificial wetland and non-wetland. 3) Changes of wetland area of the Yellow River Delta also presented stage characteristics, mainly due to the superimposed effect of the significant periodic changes of the Yellow River runoff and sediment and the increasingly severe human influence. 4) There was a function relationship between the change of wetland area and the Yellow River runoff and sediment, which was especially close between saltwater wetlands and sediment, and between freshwater wetlands and runoff. However, more improvement should be made in further study as follows: 1) Main driving factors were discussed just based on qualitative analysis, and a more quantitative method needs to be used to quantify the driving factors in the process of wetland landscape evolution, which will provide the better guidance for regional wetland protection and restoration. 2) Only Lijin hydrometric station data were used in this study, which failed to quantify the distribution of water and sediment in space, and thus, the relationship between wetland landscape evolution and water-sediment change needs to be studied more clearly. At the same time, ocean and land interaction is another important factor which should be taken into account in the future. 3) Besides, as a typical coastal wetland landscape, tidal creek plays a significant role in regional wetland evolution, but due to space limitation, its effects were not presented in this article. © 2016, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved. Source


Hong J.,Chengdu University of Information Technology | Hong J.,Plateau Atmosphere and Environment Key Laboratory of Sichuan Province | Lu X.,Chengdu University of Information Technology | Lu X.,Plateau Atmosphere and Environment Key Laboratory of Sichuan Province | And 3 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2016

The Yellow River delta is one of the most active regions in the world, where wetlands play a significant role in balancing the regional eco-environment. However, in past decades, it has been subjected to severe disturbance by nature and by humans. Thus, it is critical to figure out what changes have occurred during this period and what could be done in this region now to protect the local wetland system. Therefore, in this study, we took Landsat satellite imagery from 9 years (1973, 1979, 1985, 1992, 1995, 2000, 2005, 2010, and 2013) as data sources to build wetland thematic databases using the method of visual interpretation. Based on these databases, a Surface Wetland and Construction State Index (SWCSI) was constructed to indicate the state of the land cover. These were combined with Yellow River runoff and sediment data, regional precipitation, local GDP, aquatic product output, and crude salt output. Then, the driving forces and corresponding spatial heterogeneity of wetland variations in the past 40 years in regions of the Yellow River delta were quantitatively analyzed at regional and pixel scales. From this research, we concluded that the area of wetland in the Yellow River Delta declined during the years 1973-2013, accompanied by large-scale conversion of natural wetlands to artificial wetlands and non-wetland. In the past 40 years, the area of natural wetlands decreased by 42.67% (annual reduction of 30.58 km2). In contrast, the area of artificial wetlands increased by 490.52% (annual increase of 24.47 km2). As a result, the total wetland area was reduced by 7.99% (annual reduction of 6.13 km2). The variations of wetland in the Yellow River delta showed high spatial heterogeneities. Wetlands in coastal regions experienced artificial enhancement or wetland degradation, while those in estuarine regions experienced wetland construction and development; however, there were no changes in the western and southwestern traditional farming districts. On the regional scale, GDP was the dominant driving force for wetland variation in the Yellow River Delta. In the past 40 years, intensifying human activities and decreasing Yellow River runoff and sediment made a number of important changes (decreases in natural wetlands, increase in artificial wetlands, and degradation of regional wetlands) more serious. In contrast, a large area of natural wetland was constructed and developed in the estuary of the Yellow River because of the continuous runoff and sediment supply, although there has been an overall decline in these factors during the past 40 years. Therefore, the Yellow River runoff and sediment still played an important role in the evolution of wetlands in the Yellow River Delta, but this role was not very significant because these influences were regionally limited. The influence of regional precipitation on wetland evolution was extremely limited. This was perhaps due to the severe dependence of the regional wetlands on runoff. At the pixel scale, the driving factors of evolution of the Yellow River delta wetlands showed obvious spatial heterogeneity. This was mainly due to the spatial heterogeneity of driving force factors themselves. © 2016, Ecological Society of China. All rights reserved. Source

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