Li X.,CAS Institute of Atmospheric Physics |
Li X.,Institute of Desert Meteorology |
Xia X.,CAS Institute of Atmospheric Physics |
Wang S.,Xinjiang Climate Center |
And 2 more authors.
Particuology | Year: 2012
The global aerosol optical depth (AOD or τ) has been retrieved using the Dark Target algorithm (the C004 and C005 products) and the Deep Blue algorithm (DB product). Few validations have thus far been performed in arid/semi-arid regions, especially in northwest China. The ground-based remote sensing of AOD from sun photometers at four sites in Xinjiang during the years 2002-2003 is used to validate aerosol products, including C004, C005 and DB of the Moderate Resolution Imaging Spectroradiometer (MODIS). The results show substantial improvement in the C005 aerosol product over the C004 product. The average correlation coefficient of regression with ground measurements increased from 0.59 to 0.69, and the average offset decreased from 0.28 to 0.13. The slopes of the linear regressions tended to be close to unity. The percentage of AODs falling within the retrieval errors of 30% (or τ = ±0.1 ± 0.2τ) increased from 16.1% to 45.6%. The best retrievals are obtained over an oasis region, whereas the worst are obtained over urban areas. Both the MODIS C004 and C005 products overestimate AOD, which is likely related to improper assumptions of the aerosol model and of the estimation of surface reflectance. An encouraging result has been derived with regard to validation of the DB AOD. Overall, the average offset, slope and correlation coefficient of regression with sun-photometer measurements are -0.04, 0.88 and 0.85, respectively. Approximately 73% of the DB AOD retrievals fall within the expected error of 30%. Underestimation of the AOD by the DB products is observed. The aerosol model and estimations of surface reflectance in this region require further improvements. © 2011 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.
Hao X.-M.,Xinjiang Institute of Ecology and Geography |
Li C.,Xinjiang Climate Center |
Guo B.,Xinjiang Institute of Ecology and Geography |
Ma J.-X.,Xinjiang Institute of Ecology and Geography |
And 2 more authors.
Journal of Hydrology | Year: 2012
Dewfall can be a substantial water resource crucial for maintaining water balance in desert ecosystems such as the hyper-arid zone of the Taklimakan Desert in China. However, little is known about the formation, quantitative characteristics, and factors influencing dewfall in this region. This study elucidates dew formation and its long-term trend in this region using observational data, including flux, meteorological, and soil water content data obtained using the Eddy covariance system and those recorded by a weather station in the area. The results are as follows: (1) Dew forms in the Populus forest, with nighttime dewfall duration being about 2. h. The average daily dewfall amount during the observation period (June 4-October 24, 2011) was 0.12. mm. The number of dewfall days was 104. days (73% of total days), and the cumulative dewfall amount was 12.87. mm. (2) The dewfall days and amounts on the canopy and soil surfaces were 86. days and 8.64. mm, and 38. days and 4.23. mm, respectively. The top soil can absorb more water vapor than condensed dew. (3) At different time scales (half-hour, day, and half-year), obvious variations in dewfall duration, dewfall amounts, and meteorological factors occurred. (4) Over the past 51. years, changes in the number of dewfall days during the summer (June-October) exhibited a trend similar to that of changes in total dewfall amount during the same period. The average dewfall amount during the summer half-year was 17.2. mm, which is about 64% of the summer half-year rainfall and 50% of the annual rainfall. In particular, the total dewfall amount was higher than the annual rainfall amount during the one-fifth of the past 51. years. The study proved dewfall is one of important water resources in the arid Taklimakan Desert region, and it also significantly influenced the water balance. © 2012 Elsevier B.V..
Tao H.,CAS Nanjing Institute of Geography and Limnology |
Mao W.,Xinjiang Climate Center |
Huang J.,Nanjing University of Information Science and Technology |
Zhai J.,National Climate Center
Shuikexue Jinzhan/Advances in Water Science | Year: 2014
Drought and wetness indices are important elements since they closely associated with water and energy balance over a geographical area and extending along a certain period of time. Studying of possible cause of drought and wetness variability is of great importance to understand the hydrological cycle and disaster reduction. Based on daily observations of 39 meteorological stations in the Tarim River basin, the spatial and temporal variability of drought and wetness has been analyzed using the standardized precipitation evapotranspiration index (SPEI). The result shows an increasing trend in annual mean SPEI with a significant change point in 1986. Although the frequency of moderate and severe drought decreased after 1986, the frequency of extreme drought events increased slightly. But different categories of wetness show a consistent increase in frequency. Furthermore, we also investigated the corresponding atmospheric circulation anomalies of drought and wetness changes over the Tarim River Basin using NCEP-NCAR reanalysis datasets. Composition analysis of geopotential height and wind field at 500 hPa are performed for typical extreme dry and wetness month as well as for the warm seasons (MJJASO)of the periods 1961 to 1986 and 1987 to 2010, the result shows obvious difference in large scale circulation pattern can be found in typical wet and dry months, the intensified water vapor transportation and unstable atmospheric stratification are the main reasons of the wetter condition in warm seasons after the 1980s.
Deng M.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute |
Zhang H.,China Meteorological Administration |
Mao W.,Xinjiang Climate Center |
Wang Y.,Yunnan Provincial Meteorological Bureau
Advances in Climate Change Research | Year: 2011
This study focuses on the characters of public perceptions on climate and cryosphere change, which are based on a questionnaire survey in the Ürümqi River Basin. In comparison with scientific observation results of climate and cryosphere change, this paper analyzes the possible impact of the change on water resources and agriculture production in the area. Perceptions of most respondents on climate and cryosphere changes confirm the main objective facts. For the selection of adaptation measures addressing the shortage of water resource, the results are as follows: most people preferred to choose the measures like "policy change" and "basic facility construction" which are mostly implemented by the government and the policy-making department; some people showed more preference to the measures of avoiding unfavorable natural environment, such as finding job in or migrating to other places. The urgency of personal participation in the adaptation measures is still inadequate. Some adaptation measures should be implemented in line with local conditions and require the organic combination of "resource-development" with "water-saving".
Li H.J.,Institute of Desert Meteorology |
Mao W.Y.,Xinjiang Climate Center |
Zhao Y.,Institute of Desert Meteorology |
Wang M.Z.,Institute of Desert Meteorology |
Huo W.,Institute of Desert Meteorology
Journal of Arid Land | Year: 2012
The surface vapor content has a close correlation with the generation of precipitation. Based on the atmospheric circulation data and surface vapor content data from 37 weather stations across the Tarim Basin during 1961-2010, the paper analyzed the vapor variation trend, period, abrupt changes and their causes. The results show that the increase trend of surface vapor content over the Tarim Basin mostly conforms with the average trend coefficient of 0.48. There were 3 centers displaying a trend of high vapor increase and 3 centers displaying a low vapor increase. These centers were distributed in strips and blocks across the basin from northeast to southwest. Notable inter-decadal variations in annual and seasonal vapor contents occurred in the Tarim Basin during the 50 years of the study period, with more vapor after the mid-1980s and less vapor in the 1960s and the 1970s. The significant increase in vapor content in the 50 year period occurred mostly in the 1980s and the 1990s. The increasing trend across the four seasons was strongest in summer, reaching 0.43, and weakest in spring. Great variations existed between the spring trend and the annual, summer, autumn and winter trends. During the 50-year study period, there are distinguishable periods of 4-6 years and 8-10 years in which the annual and seasonal vapor contents varied alternately between low and high concentrations. The annual vapor content and that of the four individual seasons all changed abruptly in about the mid-1980s (α<0.05). The west wind circulation, Tibetan Plateau circulation and the annual mean temperatures of the Tarim Basin are the main factors that influenced the surface vapor content over the study area, of which the Tibetan Plateau circulation may be the most important one.
Zuo M.,Xinjiang University |
Chen H.,Xinjiang University |
Chen H.,Xinjiang Climate Center |
Wang H.,Xinjiang University |
Feng Z.,Xinjiang University
Lecture Notes in Electrical Engineering | Year: 2012
By using visual interpretation combined with supervised classification in ENVI 4.5 and with the functions of localization, measurement, and layer overlay of ArcGIS 9.2, the summer season overflowing status in middle and lower reaches of Hotan River had been monitored and analyzed, the results of which shows that: firstly, the overflowing status in middle and lower reaches of Hotan River is fairly serious, at the same time, overflowing status of irrigation areas in oasis area has drawn much attention too. Secondly, compared with other reaches the amount of overflowing water of oasis edge in the middle reach is less, the area of which is below 35 km 2 in monitoring date with the percentage of 94.4%, and the overflowing trace is unavailable in 45% of the monitoring date; From Keshen Mishen on where 2 rivers join together to the crossroad of old river channel and Hotan River, the overflowing areas are all over 35 km 2 in 45% of the monitoring date except 5 August 2004 and 29 July 2008 with the monitoring area being 0; The overflowing status of the reach from the crossroad of the old river channel to Xiaota is heaviest, most of which is over 70km 2 with the maximum of 111km 2. Thirdly, on the whole basin 10 overflowing sites have been observed, among which 4 distribute on the left and right sides of the head reach areas of Hotan River respectively, coupling with a new floodplain on each side, and also a overflowing site on the left of Karakash River has been observed. It can also be found that, on the whole, the overflowing sites mainly distribute on the head reach of Hotan River. © 2012 Springer-Verlag.
Tao H.,CAS Nanjing Institute of Geography and Limnology |
Gemmer M.,National Climate Center |
Bai Y.,Xinjiang Academy of Water Resource and Hydropower |
Su B.,National Climate Center |
Mao W.,Xinjiang Climate Center
Journal of Hydrology | Year: 2011
The characteristics of hydro-climatic changes in the Tarim River Basin were analysed based on data collected at 39 weather stations and 29hydrological stations for the period 1961-2008 and 1952-2008, respectively. A non-parametric trend test on basin scale for annual data shows an increasing trend of precipitation, relative humidity, vapour pressure, and the aridity index since 1986. Surface temperature started increasing in 1996. A decreasing trend of sunshine started in 1990. The potential evapotranspiration (ET) is calculated by the Penman-Monteith equation, and points out decreasing trend of potential evapotranspiration since 1985. This negative trend can also be detected for wind speed in both the same time scale and spatial extent. The stations with significant increasing trends in annual streamflow are mainly distributed at the southern slope of Tianshan Mountain, which can only be explained by climatic changes. The detected negative runoff trend of the main stream of the Tarim River can be explained by anthropogenic activities (such as irrigation and domestic water use) and climatic changes. A quantitative assessment reveals that local human activities since the 1970s led to a decrease of the water volume diverted into the main stream of the Tarim River Basin, which has been aggravated in the 2000s. © 2011 Elsevier B.V.
Hu L.,Urumqi Meteorological Satellite Ground Station |
Huang W.,Urumqi Meteorological Satellite Ground Station |
Huang W.,Xinjiang Climate Center |
Yin K.,Urumqi Meteorological Satellite Ground Station |
And 2 more authors.
Shuikexue Jinzhan/Advances in Water Science | Year: 2013
In Xinjiang, snow constitutes a major water resource important to crop production, ranching, water supply, and other user needs. The snow water equivalent is estimated and its spatial-temporal distribution is analyzed using the MODIS (Moderate Resolution Imaging Spectroradiometer) EOS (Earth Observing System) remote sensing data collected during 2004-2010, and a 50-year dataset of snow depths and densities from 89 meteorological stations in Xinjiang. The result shows that the maximum value of annual snow water equivalent in Xinjiang during 2004-2010 was about 36.883 billion m3, which occurred in the winter of 2009-2010; while the minimum value was only 9.391 billion m3, which occurred in the winter of 2006-2007. The difference between maximum and minimum is about four times, and the difference in the earliest and latest dates for the peak occurrence can be 50 days long. Snow water resources in Xinjiang is mainly distributed in four regions, which are South Xinjiang, eastern Xinjiang, Yili and Bozhou, northeast of North Xinjiang. The time of peak occurrence of snow water equivalent varies from region to region around Xinjiang. The peak value of snow water equivalent is the sum of peak values in the four regions. The snow water equivalent has fluctuated dramatically in past 50 years in Xinjiang. An upward trend with a slope of 0.0832 in the snow water equivalent variation has been detected, which indicates that the snow water resource in Xinjiang has increased annually. A gradually increased fluctuation range indicates there may be years with less snow water resources.
Mannig B.,University of Würzburg |
Muller M.,University of Würzburg |
Starke E.,Leibniz University of Hanover |
Merkenschlager C.,University of Würzburg |
And 5 more authors.
Global and Planetary Change | Year: 2013
The high-resolution regional climate model (RCM) REMO has been implemented over the region of Central Asia, including western China. A model run forced by reanalysis data (1/2° resolution), and two runs forced by a GCM (one run with 1/2° and one run with 1/6° resolution) have been realized. The model has been evaluated regarding its ability to simulate the mean climate of the period 1971-2000. It has been found that the spatial pattern of mean temperature and precipitation is simulated well by REMO. The REMO simulations are often closer to observational data than reanalysis data are, and show considerably higher spatial detail. The GCM-forced simulations extend to the year 2100 under the A1B scenario. The climate change signal of temperature is largest in winter in the northern part of the study area and over mountainous terrain. A warming up to 7. °C is projected until the end of the 21st century. In summer, warming is strongest over the southern part of Central Asia. Changes in precipitation are spatially more heterogeneous. © 2013 Elsevier B.V.
Yao J.-Q.,Xinjiang University |
Yao J.-Q.,Xinjiang Climate Center |
Yao J.-Q.,Institute of Desert Meteorology |
Zhao Q.-D.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute |
Liu Z.-H.,Xinjiang University
Journal of Mountain Science | Year: 2015
Much attention has recently been focused on the effects of climate variability and human activities on the runoff. In this study, we analyzed 56-yr (1957–2012) runoff change and patterns in the Jinghe River Basin (JRB) in the arid region of northwest China. The nonparametric Mann-Kendall test and the precipitation-runoff double cumulative curve (PRDCC) were used to identify change trend and abrupt change points in the annual runoff. It was found that the runoff in the JRB has periodically fluctuated in the past 56 yr. Abrupt change point in annual runoff was identified in the JRB, which occurred in the years around 1964 and 1996 dividing the long-term hydrologic series into a natural period (1957–1964) and a climate and man-induced period (1965–1996 and 1997–2012). In the 1965–1996 period, human activities were the main factor that decreased runoff with contribution of 88.9%, while climate variability only accounted for 11.1%. However, the impact of climate variability has been increased from 11.1% to 47.5% during 1997–2012, showing that runoff in JRB is more sensitive to climate variability during global warming. This study distinguishes the effect of climate variability from human activities on runoff, which can do duty for a reference for regional water resources assessment and management. © 2015, Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg.