Precipitation trends and variability from 1950 to 2000 in arid lands of Central Asia

Climate warming will cause differences in precipitation distribution and changes in hydrological cycle both at regional and global scales. Arid lands of Central Asia （ALCA）, one of the largest arid regions at the middle latitudes in the world, is likely to be strongly influenced by climate warming. Understanding the precipitation varia- tions in the past is an important prerequisite for predicting future precipitation trends and thus managing regional water resources in such an arid region. In this study, we used run theory, displacement, extreme deviation theory, precipitation concentration index （PCI）, Mann-Kendall rank correlation and climatic trend coefficient methods to analyze the precipitation in wet and dry years, changes in precipitation over multiple-time scales, variability of precipitation and its rate of change based on the monthly precipitation data during 1950-2000 from 344 meteorological stations in the ALCA. The occurrence probability of a single year with abundant precipitation was higher than that of a single year with less precipitation. The average duration of extreme drought in the entire area was 5 years, with an average annual water deficit of 34.6 mm （accounting for 11.2% of the average annual precipitation over the duration）. The occurrence probability of a single wet year was slightly higher than that of a single dry year. The occurrence probability of more than 5 consecutive wet years was 5.8%, while the occurrence probability of more than 5 consecutive dry years was 6.2%. In the center of the study area, the distribution of precipitation was stable at an intra-annual timescale, with small changes at an inter-annual timescale. In the western part of the study area, the monthly variation of precipitation was high at an inter-annual timescale. There were clear seasonal changes in precipitation （PC1=12-36） in the ALCA. Precipitation in spring and winter accounted for 37.7% and 24.4% of the annual precipitation, respectively There was a significant inter-annual change in precipitation in the arid Northwest China （PC1=24-34）. Annual precipitation increased significantly （P=0.05） in 17.4% of all the meteorological stations over the study period. The probability of an increase in annual precipitation was 75.6%, with this increase being significant （P=-0.05） at 34.0% of all the meteorological stations. The average increasing rate in annual precipitation was 3.9 mm/10a （P=0.01） in the ALCA. There were significant increasing trends （P=0.01） in precipitation in Kazakhstan, Kyrgyzstan and Tajikistan, with rates of 2.6, 3.1 and 3.7 mm/10a, respectively.

Effects of Land Use Change on Eco-environment in Hilly Area of Central Sichuan Basin——A Case Study of Yanting County, Sichuan Province

With the artificial alder and cypress mixed forest being planted, there has been a marked land use change since 1970s' in Hilly Area of Central Sichuan Basin, China. Data from meteorological observations or posts operated over long time, measurement and calculation of NPP (net primary production) and biomass of biological community, and analysis of soil organic matter content show that the artificial alder and cypress mixed forest has outstanding eco-environmental effect: adjusting local climate, raising soil fertility, alleviating menace of drought, and raising NPP and biomass of biological community. It is very beneficial for improving ecological environment to afforest artificial alder and cypress mixed forest in populous Hilly Area of Central Sichuan Basin, China. Key Words: land use/land cover change (LUCC); eco-environmental effect; Hilly Area of Central Sichuan Basin; the artificial alder and cypress mixed forest

休闲绿地活动空间设计

从"以人为本"的理念出发,通过对居住区中心绿地的道路、广场、植物、建筑的空间分析,提出活动空间设计方法和有关对策。

CPC Central Committee and State Council Release Several Opinions Concerning Establishing National Land and Spatial Planning System and Related Implementation Supervision

On May 9,2019,the CPC Central Committee and the State Council released Several Opinions Concerning Establishing National Land and Spatial Planning System and Related Implementation Supervision(shortened into the Opinions in the following part).National land and spatial planning is considered as a guidance for national spatial development,a spatial blueprint for sustainable development,as well as a fundamental basis for various development,protection,and construction activities.

Application for developing countries:Estimating trip attraction in urban zones based on centrality

This paper introduced a network centrality-based method to estimate the volume of trip attraction in traffic analysis zones. Usually trip attraction volumes are estimated based on land use characteristics. However, executing of land use-based trip attraction models are severely constrained by the lack of updated land use data in developing countries. The proposed method used network centrality-based explanatory variables as ＂connectivity＂, ＂local integration＂ and ＂global integration＂. Space syntax tools were used to compute the centrality of road segments. GIS-based kernel density estimation method was used to transform computed road segrnent-based centrality values into traffic analysis zone. Trip attraction values exhibited significant high correlation with connectivity, global and local integration values. The study developed and validated model to estimate trip attraction by using connectivity, local integration and global integration values as endogenous variables with an accepted level of accuracy （R2 〉 0.75）. The proposed approach required minimal data, and it was easily executed using a geographic information system. The study rec- ommended the proposed method as a practical tool for transport planners and engineers, especially who work in developing countries and where updated land use data is unavailable.