近60年青藏高原东北缘极端气温事件与气温日较差分析--以西宁地区为例

根据1955-2015年西宁气象站逐日气温资料,通过线性倾向估计等分析方法,选取14个极端气温指数,分析西宁地区近60年极端气温事件与气温日较差的时间变化趋势及二者的相关性,并与全国其他区域进行对比。结果表明:(1)近60年来,西宁地区的14个极端气温指数都呈现不同程度的变化,热指数夏日日数、暖夜日数、暖昼日数、作物生长期和热持续指数等分别以2. 07,0. 72,1. 49,2. 57和0. 87 d·(10a)^(-1)的趋势增加,而冷指数冰冻日数、霜日日数、冷夜日数、冷昼日数和冷持续指数分别以-2. 42,-0. 29,-0. 33,-1. 3和-0. 31 d·(10a)^(-1)的趋势减小。极端气温极值指数中,日最高气温的极低值、日最低气温的极低值、日最高气温的极高值、日最低气温的极高值分别为0. 51,0. 17,0. 35和0. 15℃·(10a)^(-1)的趋势增加。(2)在变化趋势中,日最高气温的极低值、日最高气温的极高值、冰冻日数、夏日日数、冷昼日数、暖昼日数、作物生长期和热持续日数的变化趋势为达到0. 01或0. 05的显著性水平。(3)表征极端气温事件热指数与冷指数、昼指数与夜指数的变化幅度均显示出明显的非对称性。(4)过去60年西宁地区平均全年与春夏秋冬四季的气温日较差都呈现增加趋势,增长率分别为0. 25,0. 27,0. 21,0. 15和0. 36℃·(10a)^(-1),该地区的14个极端气温指数的变化均不同程度影响到平均全年与四季气温日较差,其中,极端气温绝对指数和相对指数与气温日较差的相关性最强,对气温日较差影响显著。(5)青藏高原东北缘极端气温事件与气温日较差具有特殊性,可能受多气候系统控制和特殊地形等因素影响。

Comprehensive Evaluation of the Suitability of Agricultural Land in Myanmar

Myanmar is a country with an economy based on agriculture.It has rich agricultural resources and great potential for development.The development of agriculture in Myanmar is becoming increasingly important to international food security.Assessments of agricultural land resources in Myanmar are the basis for the country's agricultural development and for food security evaluations.In this paper we used the MaxEnt model to analyze the relationship between the suitability of land for agricultural reclamation and the main environmental variables in Myanmar,and then constructed a model to comprehensively evaluate the suitability of land for agriculture in Myanmar.The results show that:1)the overall accuracy of the MaxEnt model is high (AUC>0.8),which means there is a high correlation between the database of selected environmental indicators and the true distribution of cultivated land in Myanmar.2)Soil depth is the most important factor affecting the suitability of land for agriculture in Myanmar When the thickness of soil layer is less than 100 cm,the suitability of land for agriculture is low.With respect to topographic conditions,slope is the main factor affecting suitability.When the slope is greater than 20 degrees,the suitability of land for agriculture is low.With respect to climate conditions,precipitation is the main influencing factor. There is a positive correlation between river network density and land suitability.3)Currently,400000 km^2 of the land resources in Myanmar are suitable for agriculture,and of this amount 290000km^2 are highly suitable,accounting for nearly 40% of the country's land area.The highly suitable land is distributed mainly in Magway,Sagaing,Ayeyarwady and Yangon provinces.The provinces are also important grain production areas in Myanmar,and this serves to validate the effectiveness of the method used in this paper.

Satellite Image-based Monitoring of Urban Land Use Change and Assessing the Driving Factors in Pokhara and Bharatpur Metropolitan Cities, Gandaki Basin, Nepal

Urban growth is a key indicator of economic development.At the same time,haphazard urban growth creates serious socioeconomic,environmental and urban land management problems.In this context,understanding the process of urban landscape change is important for guiding the sustainable growth of urban areas.This study analyzes the urban land changes during 1990–2018 in two metropolitan cities of Gandaki basin:Pokhara and Bharatpur.Landsat satellite images were analyzed using supervised classification methods.The results revealed that the built-up area has increased significantly by 300%in Pokhara and by nearly 500%in the Bharatpur during the past 28 years.Population growth,migration from surrounding areas due to urban facilities and the easy lifestyle in cities were found to be major determinants of urban growth within the study area.In addition,the changing urban definition and expansion of municipal boundaries are key factors for rapid urban growth.Both cities are likely to grow in the future as they are both located in areas that encompass the high levels of commercial activity and modern service facilities.The haphazard urban growth should be minimized through planning and policies for sustainable urban development.

Fundamental Strategic Shift Required by the Expensive Ecological Policy in Chinese Grasslands

Grasslands have critically important ecological and economic values while most of them have been suffering from various degrees of degradation in China due to overgrazing. The “Forage-Livestock Balance”(FLB)policy has been implemented for more than a decade, aims to balance the relationship between forage productivity and grazing consumption of grasslands by livestock. According to the review of statistical data and literatures on policy evaluation, FLB-dominated subsidies for grassland ecological conservation policies are ineffective on grassland restoration, livestock reduction in some overloaded areas and improvement on herdsmen livelihood. To deal with the dilemma, we suggest a fundamental shift of strategy from controlling livestock numbers to maintaining and improving grassland health(MIGH) based on ecological theories, and promote the sustainable development of grassland in China. The results show that, FLB policy failed to obtain expected benefits mainly because it interfered with the herders’ autonomous use of contracted grasslands along with the defects of its underlying theory and methodologies. Implementing reward and punishment based on ecosystem health will not only motivate herders to manage their grassland autonomously, but also be more scientific and feasible than FLB.