Climate change, water resources and sustainable development in the arid and semi-arid lands of Central Asia in the past 30 years

The countries of Central Asia are collectively known as the five "-stans": Uzbekistan, Kyrgyzstan, Turkmenistan, Tajikistan and Kazakhstan. In recent times, the Central Asian region has been affected by the shrinkage of the Aral Sea, widespread desertification, soil salinization, biodiversity loss, frequent sand storms, and many other ecological disasters. This paper is a review article based upon the collection, identification and collation of previous studies of environmental changes and regional developments in Central Asia in the past 30 years. Most recent studies have reached a consensus that the temperature rise in Central Asia is occurring faster than the global average. This warming trend will not only result in a higher evaporation in the basin oases, but also to a significant retreat of glaciers in the mountainous areas. Water is the key to sustainable development in the arid and semi-arid regions in Central Asia. The uneven distribution, over consumption, and pollution of water resources in Central Asia have caused severe water supply problems, which have been affecting regional harmony and development for the past 30 years. The widespread and significant land use changes in the 1990 s could be used to improve our understanding of natural variability and human interaction in the region. There has been a positive trend of trans-border cooperation among the Central Asian countries in recent years. International attention has grown and research projects have been initiated to provide water and ecosystem protection in Central Asia. However, the agreements that have been reached might not be able to deliver practical action in time to prevent severe ecological disasters. Water management should be based on hydrographic borders and ministries should be able to make timely decisions without political intervention. Fully integrated management of water resources, land use and industrial development is essential in Central Asia. The ecological crisis should provide sufficient motivation to reach a consensus on unified water management throughout the region.

Seasonal Responses of Net Primary Productivity of Vegetation to Phenological Dynamics in the Loess Plateau, China

With global warming, the great changes in the patterns of plant growth have occurred. The conditions in early spring and late autumn have changed the process of vegetation photosynthesis, which are expected to have a significant impact on net primary productivity(NPP) and affect the global carbon cycle. Currently, the seasonal response characteristics of NPP to phenological changes in dryland ecosystems are still not well defined. This article calibrated and analyzed the normalized difference vegetation index(NDVI)time series of Advanced Very-High-Resolution Radiometer(AVHRR) data from 1982 to 2015 in the Loess Plateau, China. The spatial and temporal distributions of vegetation phenology and NPP in the Loess Plateau under semihumid and semiarid conditions were investigated. The seasonal variation in the NPP response to vegetation phenology under the climate change was also analyzed. The results showed that, different from the northern forest, there was distinct spatial heterogeneity in the effect of climate change on the dynamic change in vegetation growth in the Loess Plateau: 1) an advance of the start of the growing season(SOS) and a delay of the end of the growing season(EOS) significantly increased the NPP in spring and autumn, respectively, in the humid southeast;2) in the arid northwest, the NPP did not significantly increase in spring and autumn but significantly decreased in summer.

基于CMIP5模式的2006—2017年中亚降水预估误差分析

利用第5次耦合模式计划(CMIP5)的24个模式模拟数据,与英国East Anglia大学气候研究中心提供的2006—2017年的月降水格点数据进行比较,通过误差空间分布、误差百分率、标准差以及误差趋势分析,对多模式集合下的中亚降水预估误差进行评估。结果表明:模式集合对中亚大部分地区的年均降水预估偏多,尤其是东南部帕米尔高原与西天山的少数区域,误差偏大明显;夏半年(6—11月)在中亚东南及南部部分地区降水预估明显偏多,对中亚东北大部分区域降水预估偏少但不明显;冬半年(12及1—5月)中亚大部分区域降水量预估偏多,帕米尔高原西部部分区域以及巴尔喀什湖东部降水预估偏少,预估偏多与偏少均不明显。同时发现,中亚西部与西北部年、夏半年、冬半年模式间标准差均小于中亚东部及东南部;中亚大部分地区尤其中部的年、夏半年与冬半年降水预估误差均呈现减小趋势;厄尔尼诺年以及拉尼娜年的降水预估误差的空间分布决定多年平均预估误差分布特征。各种误差分析表明,直接使用CMIP5模式预估未来降水存在较大的不确定性,可能多来自模式本身存在的问题,如分辨率及地形处理、积云对流参数化方案、降水物理过程等描述不完善。

吐鲁番地区参考作物蒸散发模型适用性评价

吐鲁番地区干旱少雨,蒸发量远大于降水量,是中国水资源严重匮乏的地区之一。准确估算参考作物蒸散发量(ET0)是吐鲁番地区农田灌溉系统设计和发展节水农业的基础。利用吐鲁番站2000—2015年作物生长季(4—10月)的气象资料,基于线性回归、均方根误差(RMSE)、平均绝对误差(MAE)和平均相对误差(MRE)评价指标,以FAO-56 Penman-Monteith(FAO-56 PM)模型为标准,评价Priestley-Taylor(P-T)、Hargreaves-Samani(H-S)、Jensen-Haise(J-H)、Turc、Makkink-Allen(M-A)、Trajkovic(Traj)、Makkink-Hansen(M-H)和Berti-Hargreaves(B-H)模型在吐鲁番地区的适用性,并分析各模型偏差原因。结果如下:1)所有模型在生长季期间均呈单峰型变化趋势;H-S、Traj和B-H模型高估月ET0,其他模型均在不同程度上表现出低估现象。2)Traj温度模型模拟精度最高,其RMSE、MAE和MRE分别为6.38 mm、5.69 mm和4.29%;M-H辐射模型模拟精度次之,Turc辐射模型模拟精度最差。3)Rn和VPD是影响温度和辐射模型计算值偏差的主要气象因子。同时分析FAO-56 PM模型计算的ET0和蒸发皿蒸发量之间的关系,为利用蒸发皿水面蒸发量估算吐鲁番地区ET0提供参考。

Spatiotemporal changes in water,land use,and ecosystem services in Central Asia considering climate changes and human activities

Central Asia is located in the hinterland of Eurasia,comprising Kazakhstan,Uzbekistan,Kyrgyzstan,Turkmenistan,and Tajikistan;over 93.00%of the total area is dryland.Temperature rise and human activities have severe impacts on the fragile ecosystems.Since the 1970s,nearly half the great lakes in Central Asia have shrunk and rivers are drying rapidly owing to climate changes and human activities.Water shortage and ecological crisis have attracted extensive international attention.In general,ecosystem services in Central Asia are declining,particularly with respect to biodiversity,water,and soil conservation.Furthermore,the annual average temperature and annual precipitation in Central Asia increased by 0.30℃/decade and 6.9 mm/decade in recent decades,respectively.Temperature rise significantly affected glacier retreat in the Tianshan Mountains and Pamir Mountains,which may intensify water shortage in the 21st century.The increase in precipitation cannot counterbalance the aggravation of water shortage caused by the temperature rise and human activities in Central Asia.The population of Central Asia is growing gradually,and its economy is increasing steadily.Moreover,the agricultural land has not been expended in the last two decades.Thus,water and ecological crises,such as the Aral Sea shrinkage in the 21st century,cannot be attributed to agriculture extension any longer.Unbalanced regional development and water interception/transfer have led to the irrational exploitation of water resources in some watersheds,inducing downstream water shortage and ecological degradation.In addition,accelerated industrialization and urbanization have intensified this process.Therefore,all Central Asian countries must urgently reach a consensus and adopt common measures for water and ecological protection.