In this paper, the latest relevant data of Uzbekistan were obtained from the databases of the Food and Agriculture Organization of the United Nations and the United Nations data retrieval system. The development history of irrigated agriculture was investigated by analyzing the data on irrigated areas and the population and economic development in the country, and a series of environmental problems caused by unreasonable irrigation and their impact on the social economy were discussed. The results demonstrated that as Uzbekistan is a typical agricultural country, its irrigated agriculture has been developing steadily, supporting the food security and employment of the entire country. The agricultural irrigation area of Uzbekistan increased to 4.2×10⁶ hm² in the 1990s and remained basically unchanged over the following 30 years. The main water sources for agricultural irrigation are the Amu Darya and Syr Darya rivers, and most irrigation methods are based on flood irrigation. Because of the dry climate with limited rainfall, long-term irrigation has led to a continuous decline of river flow and water storage in the Aral Sea. To cope with sluggish economic growth and food demand, increasing amounts of farmland were shifted from producing cotton to wheat in the 1990s, as wheat requires less water. However, the gradual phase-out of cotton exports in Uzbekistan and the conversion of its farmland from food to fruits and vegetables, done to transform its economic structure from over-reliance on agricultural production to a more economically rewarding system within the limited land, led to a sharp decline in wheat and cotton production in 2016. Additionally, the long-term use of relatively backward water supply systems and irrigation technology has caused a serious waste of water resources and a series of environmental problems. The flooding irrigation method coupled with strong evaporation and declining irrigation water quality along with the higher groundwater level has caused large-scale salinization of soil and made Uzbekistan the sixth largest country in terms of soil salinization, with a total of 2.1×10⁶ hm² of salinized soil. The area of the Aral Sea also shrunk from 4.7×10⁶-4.8×10⁶ to 1.2×10⁶ hm² over the past 40 years, and the sea could vanish within the next 40 years, resulting in a significant reduction in water storage and a three-fold increase in salinity compared with 20 years ago. The drying up of the Aral Sea also exposed a large area of salty sediments and finally formed a new desert (the Aralkum) in 2000, causing frequent salt dust storms, which pose a serious threat to human respiratory health and the hydrological cycle. Agricultural production is economically important in Uzbekistan. It has a significant positive impact on gross domestic product and can effectively the effects of small fluctuations in the industrial and service sectors. Still, the problem of soil salinization in Uzbekistan is extremely complex. To effectively address the issue, it is necessary to fundamentally optimize the irrigation mode and drainage technology and implement advanced and efficient irrigation and drainage schemes, such as drip irrigation, sprinkler irrigation, and subsurface pipe network salt drainage. This study offers support for agricultural development and water resource management in arid areas.

The Qinghai-Tibet Plateau, China is a sensitive area for global climate change. The spatial distribution and change trend of temperature and precipitation are the core and foundation of climate change research and provide basic data for developing ecological environment change assessment. This paper is based on the observation data of meteorological stations in the Qinghai Lake Basin and its surroundings during 2000—2018 using elevation as a covariate combined with the professional meteorological interpolation software ANUSPLIN to perform spatial interpolation of temperature and precipitation. The linear regression method was used to analyze the variation in the temperature and precipitation in the Qinghai Lake Basin. Furthermore, bivariate spatial autocorrelation analysis was used to analyze the spatial coupling relationship of temperature and precipitation in the basin. The research results show the following: (1) The temperature in the Qinghai Lake Basin from 2000 to 2018 showed an increasing, with an average growth rate of 0.30 ℃·(10a)^-1, and increased significantly in spring. (2) Precipitation showed a significant increasing trend, with an average growth rate of 73.20 mm·(10a)^-1; the growth rate is significant in spring and summer, the change is not obvious in autumn, and the winter tends to become dry. (3) The spatial matching of temperature and precipitation in the Qinghai Lake Basin is significantly different. On the interannual scale, the Moran’s I of temperature and precipitation is -0.66, showing a significantly negative correlation, with an area ratio of 67.56% and poor spatial matching of water and heat combinations. On a seasonal scale, the Moran’s I of temperature and precipitation in the Qinghai Lake Basin in spring, summer, autumn, and winter are -0.49, -0.80, -0.32, and -0.14, respectively, which are all negatively correlated in space. In spring and summer, the temperature in the low-altitude areas of the basin gradually increases, the precipitation in the high-altitude areas gradually increases, the area of negative correlation between temperature and precipitation gradually increases, and the spatial matching of water and heat is poor. Notably, the large water body of Qinghai Lake has an obvious regulating effect on the local temperature in the area surrounding the lake and serves as the climate regulator of the Qinghai Lake Basin.

Desertification is known to be the “cancer of the earth”. Mongolia is a country with the most serious desertification in the world. The desertified land in Mongolia is still expanding, and the central region is an important new expansion area. The frequent dust storms have caused serious harm and are a great threat to infrastructure connectivity, energy and resource base construction, ecological security, and environmental health and have become a major hurdle limiting Mongolia’s socio-economic development and ecological security. Choir City, the capital of Gobi Sumber Province, is located in the central part of Mongolia. It is an important section of the Mongolian Plateau of the China-Mongolia-Russia economic corridor. It belongs to the mixed zone of grassland, dry grassland, and desert grassland. It is sensitive to natural and human disturbance and has serious wind erosion desertification. In this study, the wind dynamic conditions for the occurrence of local wind erosion desertification were examined using observations from the self-built automatic meteorological observatory (May 2019—July 2020) and the meteorological station of Choir City (1990—2018) and the sand collector (August 2019—August 2020). The results showed that (1) there were strong wind dynamic conditions for the occurrence of wind erosion desertification in the region. The annual sand drift potential was 735.96 VU, the resultant sand drift potential was 428.76 VU, and the resultant drift direction was SSW (195.06°). The wind direction variability index was 0.58, which belonged to the high wind energy environment with a moderate rate of variation-blunted double-peak wind conditions. (2) The critical wind speed was affected by soil moisture and vegetation coverage, which varied with seasons: it was the highest in summer and the lowest in winter, and spring and autumn are in the middle. (3) Because of the strong wind dynamic conditions and degraded surface, the sediment transport flux of aeolian sand flow was very high (2.135 t·m^-1·a^-1) in Choir City. The maximum sediment transport rate model developed by Owen was suitable for the simulation of aeolian sand flow in this area. This study presented a detailed analysis of wind dynamic conditions in Choir City, located in the central desert steppe region of Mongolia. The characteristics of critical starting winds in Choir City were analyzed in each season by combining soil moisture and particle size, vegetation conditions, and other factors to identify the wind dynamic basis and related influencing factors in the central steppe region of Mongolia and provide basic data for local wind and sand disaster control. The research results could provide an important reference for desertification control, ecological restoration, and local engineering construction in the desert steppe area of central Mongolia.

ERA5 is the latest generation of ECMWF reanalysis product. Its precipitation data can be used to analyze the spatial and temporal characteristics of precipitation, extracting rainstorm and flood events, driving crop models, hydrological models, and land surface models. Studies on the effects of using reanalysis data to drive various models to simulate climate change are becoming more common in the context of climate change. However, as atmospheric reanalysis data, the data quality of ERA5 precipitation data will be affected by the errors of forecast products, observation data, and assimilation methods. The precision of reanalysis data will influence the uncertainty of related study results. As a result, verifying and evaluating the accuracy of reanalysis data is both necessary and urgent. To investigate the applicability of ERA5 precipitation data in China, daily precipitation data from 728 Chinese sites were used as a reference to examine the accuracy of ERA5 reanalysis precipitation data at various time scales (month, quarter), different climate zones and different elevation gradients using the Pearson correlation coefficient (r), root mean square error (RMSE), mean absolute error (MAE), probability of detection (POD), false alarm rate, and equitable threat score. Furthermore, the capability of ERA5 to depict heavy rain and drought events was investigated. The results demonstrate that there are spatial and temporal differences in the ability of ERA5 precipitation data to identify daily precipitation events. Among the eight climatic zones, the north temperate zone has the highest accuracy. The r, RMSE, and MAE of ERA5 daily precipitation and station observation are 0.587, 4.040 mm·d^-1, and 1.472 mm·d^-1, respectively, in the north temperate zone. Precipitation data from the ERA5 are less accurate in the summer and autumn than in the winter and spring. The accuracy of ERA5 precipitation data in areas with elevations greater than >500 m is lower than in areas with elevations of less than ≤500 m. When the ERA5 data is used to identify the heavy rain, there is a large deviation from observations of the stations, and the larger the threshold (i.e., the stronger the heave rain), the larger the deviation is. The accuracy of standardized drought index (SPI) of different time scales calculated using ERA5 is different, varies with SPI on a three-month time scale having the highest accuracy. When using ERA5 data to identify drought events, the lower the threshold (that is, the greater the severity of the drought), the greater the error. Generally speaking, the drought capture ability of the north temperate zone, south temperate zone, and north subtropical zone is better. This research broadens the scope of validation of climate data sets and serves as a model for future research. These findings serve as a reference for related studies considering whether to use ERA5 data, as well as a tool for analyzing the uncertainties of related studies.

Uzbekistan is a double landlocked country located in the hinterland of Central Asia and an important country on the ancient Silk Road. Within the framework of implementing the Belt and Road initiative, China and Uzbekistan have broad prospects for cooperation in the field of renewable energy. Currently, a knowledge gap exist regarding the latest state of Uzbekistan’s renewable energy development, particularly the national development plan and preferential policies for Uzbekistan’s renewable energy, Uzbekistan’s green economy strategy and carbon emission reduction (climate change) measures, and renewable energy. This article uses literature analysis, case study, data analysis, and other research methods to analyze the development status of Uzbekistan’s renewable energy, such as solar energy, hydropower, wind energy, geothermal energy, biogas energy, national development plans, and a series of preferential incentive measures and green economy strategies. The overall situation of Uzbekistan’s renewable energy development is analyzed from various dimensions, such as carbon reduction measures and market competitiveness. Analysis results show that Uzbekistan has favorable natural conditions for renewable resources, and active policies have been adopted nationally to promote innovative development in the field of renewable energy. In the future, Uzbekistan will gradually increase its proportion of renewable energy and continue to increase financing in this field. Recently, the government of Uzbekistan has been attaching great importance to the development of renewable energy and has successively issued relevant policies to vigorously promote the construction of renewable energy power generation projects to achieve energy diversification. Broad prospects for China-Uzbekistan cooperation are available in the field of renewable energy utilization. Both countries have a considerable cooperation space in talent, technology, capital, and equipment, and are expected to make great achievements in improving the utilization efficiency of renewable energy, developing a green economy, and conducting low-carbon energy cooperation.

Located in the hinterland of Eurasia, Tianshan Mountains are the main water source in the middle part of the Silk Road Economic Belt. The water circulations of the Tianshan Mountains are distinguished by large spatiotemporal variations, complex water generation mechanisms, multiple runoff composition, and a fragile water system. The runoff processes are extremely sensitive to even minor changes in hydrological elements caused by climate change. It is difficult to describe the internal hydrological mechanism using the current hydrological model. Based on the literature review, the paper systematically analyzes the key hydrological elements under climate change, including identification of the water vapor source and its transport, changes in water cycle elements and their impact on precipitation, the impacts of climate change on precipitation, runoff generation, glacier accumulation/melting, snow and water resources in the Tianshan Mountains. The hot issues on the water cycle in the Tianshan Mountains are presented to provide a scientific basis for understanding the water cycle mechanism of the mountainous areas and ensuring the safety of water resources in the middle parts of the Silk Road Economic Belt.

Lake Aksayqin, a typical large high-altitude lake located in the arid area of the northwestern Tibetan Plateau in China, is ideal for studying the changes in the Westerlies and Indian Summer Monsoon and the interplay between them. To reconstruct the paleoclimate changes of the lake, a 5.31 m long lake sediment core (AKLC15-1) was obtained at a water depth of 16.40 m. The grain size characteristics of the lake core were analyzed to investigate the hydrodynamics and lake-level changes. Based on the changes of multiple indicators, such as grain size results, total inorganic carbon, total organic carbon, total nitrogen, and magnetic susceptibility, we primarily discuss the changes in the lake environment, such as hydrodynamic transport conditions, lake surface changes, and cold and warm changes in the lake area under different sedimentary depths. The results show that the Lake Aksayqin area experiences a high rate of evaporation; the lake water is mainly supplied by glacier meltwater; and the organic matter content in lake sediments is low and mainly comes from endogenous aquatic organisms. The sediments of Lake Aksayqin are mainly composed of silt (70.48%), clay (27.64%), and sand (1.88%). The environmental change can be roughly divided into four stages. The first stage (531-480 cm) has a relatively warm climate, weakening evaporation in the basin, low aquatic productivity of the lake, and a deep-water environment with weak hydrodynamic transport conditions. In the second stage (480-380 cm), the climate is cold and dry, the evaporation in the basin is extremely strong, and the aquatic productivity of the lake is relatively high, which is a shallow water environment with strong hydrodynamic transport conditions. In the third stage (380-160 cm), the climate gradually warms. The amount of water entering the lake increases, the lake surface expands, and the hydrodynamic transport conditions of the lake gradually weaken. The fourth stage (160-0 cm) has a cold and dry climate with enhanced evaporation of the basin. The productivity of the lake is low; it has a deep-water environment with weak hydrodynamic transport conditions. This study will provide basic scientific data and theoretical support for reconstructing climatic changes and the relationship between the Westerlies and Indian Summer Monsoon in the northwestern Tibetan Plateau.

The Tianshan Mountains receive more precipitation than the rest of the Xinjiang arid zone. Previous studies investigated the precipitation variation in Tianshan Mountains of Xinjiang, China, by using daily and monthly precipitation data, but they did not focus on the diurnal variation of summer precipitation. Summer (June to August) hourly precipitation data covering 11 meteorological stations in Tianshan Mountains during 2012—2018 revealed the characteristics of diurnal variation, including the amount, occurrence, and intensity of precipitation. The relationship between terrain height and precipitation is investigated. The main conclusions are as follows: The peak values of total precipitation and total precipitation frequency occur from 20:00 to 22:00 Beijing time, and the valley values occur from 12:00 to 13:00. Precipitation mainly occurs at night (21:00—08:00), and the total precipitation is mainly contributed by long-term precipitation. The intensity of total precipitation shows an increasing trend during the day (09:00—20:00) and an opposite variation at night. The precipitation is related to terrain height and light rain frequently occurs at high altitudes. The maximum rainy belt is found at an altitude of about 2000 m.

The Aral Sea, which was once the largest inland lake in Central Asia, is located far from oceans, and thus, a vulnerable hydrological system. The water balance in the lake has changed in recent decades under the combined impacts of climate change and anthropological activities, and problems related to limited water resources and ecological environment have attracted wide attention. Analysis of the variation trend and influencing factors of terrestrial water storage (TWS), one of the most important parameters of land water variation, can provide a scientific basis for the sustainable utilization of water resources in the Aral Sea Basin. In this paper, the spatiotemporal variations of terrestrial water storage change (TWSC) in the Aral Sea Basin are evaluated using the JPL-RL06M data collected by the GRACE gravity satellite from 2002 to 2016. CRU TS4.03 meteorological data, GLDAS-Noah surface evapotranspiration data, and high-precision land use data are combined to assess time-series changes in TWSC, precipitation, temperature, and water evaporation via the linear trend method. Using a resolution of 1°×1° pixel, we calculated the correlation coefficients of various parameters, including TWSC, precipitation, and surface temperature, to explore the effects of climate change and anthropological activities on TWS in the Aral Sea Basin. Several interesting results were obtained. (1) The TWS of the Aral Sea Basin declined at a rate of -3.20 mm·a^-1 in 2002—2016. A water surplus in spring and summer and a water deficit in autumn and winter were observed. Moreover, the TWSC of the Aral Sea Basin was characterized by a surplus in the central and eastern regions and deficits in peripheral areas. (2) Precipitation in the Aral Sea Basin in 2002—2016 decreased at a rate of -1.14 mm·a^-1, and the surface temperature increased at a rate of 0.11 °C·a^-1. Precipitation and TWSC were positively correlated in most areas of the Aral Sea Basin but negatively correlated in the middle and lower reaches of the Amu Darya Basin and the lower reaches of the Syr Darya Basin. The surface temperature was negatively correlated with TWSC in most areas, but a positive correlation between these parameters was observed in some areas in the lower reaches of the Amu Darya and Syr Darya River Basins. TWSC was more strongly correlated with precipitation than with surface temperature. (3) In 2000—2015, the cultivated land area in the Aral Sea Basin increased slightly by 1.65×10⁴km², but the grassland and water areas decreased. Increases in water for crop management and irrigation intensified water expenditures from the Aral Sea Basin. Under the joint influence of climate change and anthropological activities, evapotranspiration in the Aral Sea Basin increased at a rate of 21.63×10⁸ m³·a^-1. The correlation coefficient between evapotranspiration and TWSC was as high as 0.74, which means this parameter may be a main factor affecting TWSC.

Habitat quality is an important foundation for human well-being and sustainable development. It is of great significance for regional ecological conservation and sustainable land resource use. Therefore, this paper explores the changes in the spatial patterns of habitat quality in the Weihe River Basin, northwest China from the perspective of land-use change by analyzing three periods of land use data from 2000 to 2020 and coupling the PLUS and InVEST models to predict and evaluate future land use and habitat quality. In our analysis, we found that from 2000 to 2020, the areas of construction land and grassland in the Weihe River Basin increased year by year, the area of forest land rose slightly, and the area of cultivated land continuously decreased. However, we predict that the drastic land-use changes in the Weihe River Basin will decrease significantly and land-use changes will stabilize from 2020 to 2050. In addition, we further explored the spatial distribution and changes in habitat quality in the basin on the basis of the analysis of land-use changes. We found that the overall level of habitat quality in the basin was moderately high from 2000 to 2020, with a clear trend of habitat quality polarization, gradually increasing areas of low and high habitat quality, and gradually decreasing areas of moderate habitat quality. However, the overall level of habitat quality in the basin gradually increased, consistent with the increasing ecological improvement in the Weihe River Basin in recent years. From 2020 to 2050, the overall habitat quality in the basin will continue to increase, but the growth rate will slow down and the intensity of habitat quality changes will decrease. After analyzing land use and habitat quality, we explored the main reasons for their change. We found that regional ecological compensation policies and socioeconomic development were the main reasons for land-use changes. Meanwhile, habitat quality was closely related to the spatial pattern of land use, with higher and more stable habitat quality levels in areas with high concentrations of forested land and low disturbance of human activities, whereas the habitat quality tended to be poorer in plain areas where human activities are more intensive and urban development is more concentrated. However, it is worth acknowledging that the management and restoration of the ecologically fragile areas of the Loess Plateau in the watershed have led to a gradual improvement in habitat management, which is also an important reason for the overall improvement in the habitat quality in the watershed as a whole.

National Forest Parks are important tourist destinations in China and are the main positions for the development of ecological, mountain, health, and leisure tourism in China. This study takes National Forest Parks in 1994, 2004, and 2019 as the research object. It employs the vector data of National Forest Parks and national precipitation, raster data of the national elevation, national A-level scenic spots, and national spatial administrative boundary vector data from 1994 to 2019 as the research data. Various GIS analysis and SPSS analysis methods are adopted, such as grid fractal method, kernel density method, exploratory spatial analysis, buffer analysis, and correlation analysis. The research results are as follows. (1) National Forest Parks are mainly distributed in east of Hu Huanyong Line, roughly forming high-density distribution areas centered on the Beijing-Tianjin-Hebei, Yangtze River Delta, Sichuan-Chongqing junction, and Hunan-Jiangxi junction. It shows a distribution pattern of “large agglomeration and small scattered”. (2) The fractal characteristics of the National Forest Parks system are obvious, and the fractal structure is more complicated. (3) The distribution of National Forest Parks varies significantly among provinces. The three major zones show a “convex pattern” differentiation law with less in the east and west and more in the middle. The eight regions show that “the distribution of National Forest Parks decreases from the middle and lower reaches of the Yangtze River, the southwest to the northeast and the middle reaches of the Yellow River”. (4) The hot spots of National Forest Parks show a certain degree of instability, where Heilongjiang, Jiangsu, and Zhejiang are more active in the development and keep in hot spots, whereas Xinjiang, Tibet, and Sichuan are in cold spots, and the development of forest parks is relatively slow. (5) Topography, precipitation, tourist source market, and tourism resource endowment are the main factors affecting the spatial distribution pattern of National Forest Parks. Therefore, it is proposed that: (1) Increase the number of locations of National Forest Parks in the east and west. (2) The spatial relevance of National Forest Parks is obvious, and the Matthew effect of space is significant. In the future, all regions, provinces, and National Forest Parks should strengthen cooperation to form a community of destiny for developing forest park tourism. This will contribute to the better and faster development of national parks in China. (3) According to the four major influencing factors of National Forest Parks, the development model of National Forest Parks can be divided into scenic-reliant development, natural geographic element utilization development, and market-driven development models. This research will further expand and deepen the research content and direction of China’s forest parks. It will also provide references for rational layout and healthy development of China’s National Forest Parks to form a community of common destiny of forest park tourism in China and promote the better and faster development of China’s national parks.

The Minqin County, Gansu Province is located between two large deserts (the Badain Jaran Desert and Tengger Desert) of northern China. In recent decades, the groundwater level in Minqin has continued to decline, and water resources are severely in short supply. Accordingly, analyzing the process of groundwater development and utilization over the years, as well as the dynamic characteristics of groundwater changes, is particularly important in correctly guiding the rational development and utilization of local groundwater and ecological restoration. Based on the collection and analysis of 138 water level data, this study delineated the groundwater dynamic types of Minqin County and used the Kriging interpolation method to plot year-by-year the groundwater flow field and the water level changes in the Minqin Basin from 1985 to 2016. The grid method was utilized to calculate the multi-year storage variables of groundwater. The influencing factors of the groundwater level in the Minqin Basin were explored; a regression equation was obtained; and the recoverable amount of groundwater was estimated. The results are presented herein. First, the groundwater level in Minqin can be divided into four dynamic types, that is, mining, irrigation infiltration-exploitation, river infiltration-exploitation, and runoff. Second, the overall groundwater level dropped over the years. The irrigation area significantly dropped, with a maximum drop of 22 m. The desert area also slightly dropped. The groundwater suffered a cumulative loss of 24.45×10⁸ m³ over the years. Third, after the comprehensive treatment of the Shiyang River, the water level decline significantly slowed down, and a partial rise was observed. The storage variables were positive in some years. Fourth, the main influencing factors of the groundwater dynamics are extraction volume and surface water diversion volume. The groundwater volume change process is divided into a rapid decline period (1985-2000), a stable decline period (2001-2006), a treatment period (2007-2009), and a steady/increasing period (2010-2016). Lastly, under the current surface water supply, the groundwater recoverable volume in Hongyashan Irrigation District is approximately 0.61×10⁸ m·a^-1.

The hilly-gully region of the Loess Plateau is a great challenge in the practice of new urbanization in western China. Without clarifying its regional characteristics, the intervention of modern urban planning and design has impacted the local environment and the native culture considerably. With the destruction caused by human settlements to the natural environment and the impact of modern towns on traditional settlements in the Loess Plateau of northern Shaanxi, an urgent task is to make rational use of the land in hilly-gully regions and explore the construction mode of settlements on the basis of the wisdom and experience of local people from the perspective of urban-rural integration and harmony between human beings and nature. Three-dimensional spatial characteristics in the long-term evolution of human settlements in hilly-gully regions are becoming increasingly obvious. To improve the utilization efficiency of hilly-gully land in urban construction, three-dimensional fractal analysis for organic growth of settlements has become one of the important contents of urban morphological study. With Donggou, Mizhi County, in northern Shaanxi taken as an example, this article revealed the topographical changes in Donggou and the spatial features of its settlement distribution by using the mesh method on the basis of satellite remote sensing images and digital elevation model altitude data. This work also analyzed and evaluated the coordination relationship between Donggou’s topographical complexity and settlement density through four-quadrant classification, and then measured and compared the spatial efficiency of various settlement patterns by using 3D grid fractal dimension models. This work proposes that settlement samples with high grid fractal dimensions and fit into the landscape are important references in dealing with the urban spatial development problems in the hilly-gully region of the Loess Plateau. The results are as follows: (1) The settlements in Donggou exhibit obvious spatial variation from the outside to the inside; the building density and the floor area ratio first decrease then increase and decrease again as the settlements move farther away from riverbanks. (2) Overlay analysis of Donggou’s topographical complexity and settlement agglomeration degree shows that the concentrated settlements on smooth terrain and the scattered settlements on complex terrain reflect a harmonious man-land relationship, and these two settlement types account for about 70.5% of the total land area of all settlements. (3) The 3D grid fractal dimension value of the settlements in Donggou is obviously segmented, while terrace parallel and free parallel settlements have the highest 3D fractal dimension value of 2.35-2.55. (4) Among the five typical spatial patterns of settlements, three efficient and appropriate patterns, terrace parallel, free parallel, and block mass types, are characterized by a harmonious man-land relationship and efficient space utilization, and can thus be used as a reference in creating settlement spaces in hilly-gully regions.

In recent years, the issue of climate change in northwest China has aroused widespread concern from many walks of life. Shi Yafeng proposed in 2002 that the climate in northwest China may be changing from warm and dry to warm and wet. Since then, scholars have gradually paid more attention to the phenomenon of “warmer and wetter” in the northwest climate. From the beginning of the 21^st century, a trend of increasing temperatures has become more pronounced, and changes in precipitation have diverged from the predictions of previous studies. Against this background, what recent changes have taken place in temperature and precipitation in northwest China? In particular, has the climate undergone a dry-wet transition in the past 20 years due to rising temperatures and increased precipitation? Has the region itself changed in response? This contribution analyzed average temperature and precipitation data for northwest China from 1960 to 2019. From this, temporal and spatial characteristics of climate change were assessed, revealing more about the possible transformation to warm, humid conditions. Such changes are significant to the ecological environment, social and economic development, human production, and life practices in northwest China, and their understanding provides a basis for responding to climate change and disaster prevention or mitigation across northwest China. The study found that: (1) Average temperature and precipitation both showed an upward trend in northwest China from 1960 to 2019, with a significant warming trend and a weaker humidification trend. (2) Since 1997, both temperature and precipitation have risen rapidly, especially in the eastern part of northwest China, where the rate of increase in precipitation has exceeded that of the western part over the same period. Moreover, this research suggests that, since 1997, northwest China has indeed experienced a warm and humid climatic transition; the onset of this transition was earlier than previously recognized. (3) Compared with previous studies, the geographic character of the climate transition has also changed: east Gansu Province has changed from a non-transition area to an area of significant climatic transition; and the eastern and western areas of Qinghai Province have changed from mild transition areas to areas of significant transition.

Among aeolian landforms, studies on yardang are still lacking, with the amount of quantitative research being particularly inadequate. This lack of research data prevents a better understanding of the evolutionary process of yardang landforms. In order to quantify the morphological characteristics of Bailongdui Yardang in Lop Nur, northwest China, the length, width, and length/width ratio (R value) of 1000 yardangs in four subregions of Bailongdui Yardang were measured and analyzed using data based on a series of remote sensing images. The results show that the characteristics of length, width, and R value are similar in the four subregions. The average length of yardangs is 63.42 m, of which approximately 65% are in the length range from 25.00 m to 75.00 m; their average width is 13.97 m, with approximately 80% existing in the range from 5.00 m to 20.00 m. The average R value is 4.37, with 80% existing in the range between 2.00 and 6.00. Yardangs with similar R value are developed under specific wind field conditions; in the case of those yardangs with an R value of 4.00, the Bailongdui Yardangs were eroded to a stable shape, and this shape is similar for all yardangs developed under specific wind field conditions. Besides the wind, other factors, in particular the stratigraphic lithology, surface salt crust, and extreme arid climate, are also important determining factors in the yardang’s formation.

In this work, based on daily cloudless remote sensing of snow cover and meteorological observation data, the horizontal and vertical distribution characteristics of and variations in snow cover days in the Sanjiangyuan (Three Rivers Headwaters) area of Qinghai, China from 2001 to 2020 are analyzed; the correlation between snow cover days and temperature and precipitation are also analyzed using the same data source. The results showed that: (1) From 2001 to 2020, the number of snow cover days in Sanjiangyuan area was higher in the west and lower in the east; the number of snow cover days is higher in the high-altitude mountain regions than in the basin plain. The average snow cover days in high-altitude mountains was generally greater than 200 d. The number of snow cover days in 85.48% of the areas showed an increasing tendency (with fluctuations), increasing by 16.59%, and the average rate of increase was 0.98 d·a^-1. (2) There were clear differences in the number of snow cover days and their variation over the study period based on the altitude and aspectality of the study region. The number of snow cover days increases exponentially with increasing altitude: at low altitude (<3.0 km) the snow covered area was found to be small and shows a decreasing trend. At low altitudes the number of snow cover days rate of reduction accelerates with increasing altitude. At high-altitude areas the number of snow cover days is larger and shows an increasing tendency, but the increase rate in the number of snow cover days at heights of more than 4.4 km decreases as the altitude increases. In the elevation range 5.5-6.0 km, the number of snow covered days showed a tendency to decrease. The number of snow cover days onnorth-facing slopes is greater than that on south-facing slopes; west-facing slopes show a larger number of snow cover days than east-facing slopes. Northwest-facing slopes have the largest number of snow cover days with 78.30 d. The rate at which the number of snow covered days increases was found to be greatest for west-facing slopes (1.04 d·a^-1). (3) The warm and humid climatic characteristics of the Sanjiangyuan area over the past 20 years were the main causes of the change in the number of snow cover days; precipitation was also a primary driving factor, and the increase of snow cover days was closely related to the increase in precipitation; snow cover days at high altitudes are more dependent on precipitation.

In recent years, drought disasters have occurred frequently in Inner Mongolia, northern China, and losses caused by drought have increased year by year. Understanding the spatial and temporal characteristics of drought, and associated disaster-causing factors, are crucial for early-warning, prevention, and mitigation of future regional drought disasters. This study utilized the comprehensive SPEIbase v.2.6 dataset of precipitation and evapotranspiration from 1949 to 2018 for Inner Mongolia. The spatiotemporal characteristics of drought-related meteorological data were analyzed statistically using Theil-Sen trend analysis and the Mann-Kendall method. Based on the multi-year average intensity of droughts, a weighted comprehensive evaluation model was used to assess the drought hazard at annual and seasonal timescales. Results from Inner Mongolia show a significant downward trend in SPEI-12 (i.e., the SPE index calculated on a 12-month timescale), indicating that the climate of the study area experienced an increasing risk of drought with time. This trend of increasing frequency and degree of drought became particularly pronounced from the start of the 21^st century. For the three seasons of spring, summer, and autumn, the climate of the whole of Inner Mongolia shows a significant trend of increasing drought frequency. Data for winter do not show a significant drought trend on an interannual timescale. Spatially, winter data show increasing humidity in the east and a subtle trend of increasing drought in the west. In general, Inner Mongolia can be considered extremely prone to drought disasters: areas ranked with a drought hazard grade of medium and above account for 71% of the total area of the province. The principal areas of high and extremely high drought risk are located in the east of Hulun Buir City and Xilin Gol League. For spring and summer, the spatial distribution of drought hazards in Inner Mongolia shows a pattern of “high in the north and low in the south”. The high-grade hazards lie mainly in the Xilin Gol grassland and the Alxa League. In autumn and winter, the areas of high-grade hazard shrink significantly in size. In winter particularly, low- and extremely low-grade hazards of drought disaster are found in the northeast part of the study area, consistent with the spatial characteristics of the evolving drought trend. In summary, the results of this study can provide a scientific reference for drought disaster risk management in Inner Mongolia. The SPEI index, which integrates the sensitivity of demand for evapotranspiration, is shown to have good applicability in the study area. The SPEIbase v.2.6 dataset used in this study can remove the need for data collection and SPEI calculation, which improves efficiency. In the future, we will consider drought duration and other factors to optimize the model and enhance its predictive capabilities.

Drought is one of the most serious natural disasters that human society is facing, which substantially affects agriculture and animal husbandry. China is a region with high incidents of drought disasters globally. For drought monitoring, early warning and ecological environment protection in China, analyzing the characteristics of drought and assessing its occurrence probability is crucial. The standardized precipitation-evapotranspiration index (SPEI) series at 1-, 3-, 6-, and 12-month timescales were calculated using the daily surface climate data set of the National Meteorological Data Center from 1980 to 2019. After comparing and analyzing the fluctuations in the SPEI series at different timescales, the 3-month-timescale SPEI (SPEI-3) was selected to identify historical drought events and extract three characteristic variables (drought duration, drought severity, and intensity peak) based on the theory of runs. SPEI-3 can fully reflect the seasonal dryness and humidity and is commonly used in agricultural drought monitoring. Then, using two- and three-dimensional Copula models, the joint distribution between two- and three-dimensional drought characteristic variables was constructed to estimate the occurrence probabilities of drought events under different combinations of drought duration and drought severity and those under different combinations of drought duration, drought severity, and intensity peak, respectively. Finally, the return periods of a single drought characteristic variable and the joint return periods of different types of “high-intensity-peak drought” were calculated. The results show that “mild drought” and “moderate drought” are most likely to occur in China from the perspective of drought severity. In terms of drought duration, “cross-season drought” is most likely to occur in China, and “drought over half a year” is most likely to occur in the northern arid region compared with other agricultural regions. The occurrence probability of “high-intensity-peak drought” is much less than that of “low-intensity-peak drought”, and its probability increases with increasing drought duration. The joint return periods of “high-intensity-peak drought” in the North China Plain, middle and lower Yangtze River Plain, and southern China are generally shorter than those in other regions. Short duration (“monthly drought”, “intra-season drought”, and “cross-season drought”) and low severity (“mild drought” and “moderate drought”) are the dominant factors for the joint return periods of various drought events in China. In this study, multidimensional drought characteristic analysis and hazard assessment were conducted nationwide, which are conducive for macroscopic understanding of the overall drought risk pattern in China and provide reference for drought control and prevention.

Using conventional ground and upper-air observations, NCEP 1°×1° reanalysis data, and FY satellite data, this study focuses on three common types of snowstorm weather systems in Urumqi, Xinjiang, China from 1990 to the present, and considers snowstorms with high and low altitude circulation and weather system configuration, unstable conditions, water vapor, dynamic mechanisms, and black body temperature (TBB). The results show: (1) Three snowstorms occurred during the southeast recession of the European high-pressure ridge, which pushed the West Siberian trough eastward and southward and, combined with the mid-latitude short-wave trough, the weather system at high and low altitude showed a “backward trough” structure. Urumqi was in the area where the northwest jet, at 925-600 hPa, and the strong southwest jet, at 600-200 hPa, overlapped. Forced elevation uplift caused by the Tianshan Mountains contributed to maintaining and strengthening the snowstorm. (2) There are southeasterly winds from 850 hPa to 700 hPa before the snowstorm. The slight advection was beneficial to the generation and strengthening of advective inversion, and this led to a continuous accumulation of energy. In the later stage, cold air entered, a cold front was generated, and stratification developed unstably, resulting in heat conditions for the snowstorm. The longer southeasterly wind and advective inversions are maintained, the more energy is stored and, as a result, the stronger the snowfall. (3) There are two water vapor transport channels in the snowstorm area: the southwest and the west paths. Water vapor transport in the middle layer is very important for snowstorms in Urumqi. There is a strong water vapor convergence at 850-600 hPa, with 700 hPa being the strongest. Together, water vapor transport, convergence intensity and duration determine the intensity of the snowstorm. (4) There is a correlation between TBB and snowfall intensity. The lower the TBB, the higher the cloud top height, and the more vigorous the development of mesoscale cloud clusters, the stronger the snowfall. The first rapid decrease (increase) of TBB (cloud top height) before a snowfall begins indicates the start of the snowfall. The decrease of TBB during the snowfall corresponds to the increase in snowfall intensity, and the greater the TBB drop, the longer the maintenance time of the low TBB value and, as a result, the stronger the snowfall.

On the basis of the ERA-Interim monthly reanalysis data provided by the European Center for Medium-Range Weather Forecasts from 1979 to 2019 and Climatic Research Unit monthly precipitation data, the relationships between the North Africa subtropical high and the summer precipitation over Central Asia are analyzed. The results show that the variations of the ridge line index and eastern extension ridge index of the North Africa subtropical high are closely related to those of the summer precipitation over Central Asia. The effects of single and concurrent variations of the North Africa subtropical high on summer precipitation and circulations over Central Asia are significantly different. The ridge line of the subtropical high mainly affects the precipitation anomalies in the south and north parts of Central Asia, whereas the eastern extension ridge of the subtropical high plays an important role in modulating summer precipitation in the central and southern regions of Central Asia. Furthermore, we analyze the anomalous distribution of summer precipitation and atmospheric circulations under the concurrent variations of two indices. When the subtropical high shifts southeastward, there is an anomalous cyclone over the Caspian Sea and Aral Sea, corresponding to more summer precipitation over most areas of Kazakhstan. Meanwhile, Xinjiang is controlled by an anomalous anticyclone over the Mongolian Plateau, corresponding to less summer precipitation. When the subtropical high shifts southwestward, Central Asia is mainly controlled by an anomalous anticyclone, but there is an anomalous cyclonic shear in its northeast parts. Thus, more rainfall occurs in the northeast of Central Asia and less precipitation in other regions. When the subtropical high shifts northwestward, Central Asia is controlled by an anomalous anticyclone, corresponding to less summer precipitation. When the subtropical high shifts southeastward, Central Asia is controlled by an anomalous cyclone, and tropical Indian Ocean water vapor can enter Central Asia via two-step transportation, forming favorable dynamic and water vapor conditions; thus, Central Asia receives more summer precipitation.