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Southwest China (SC) has suffered a series of super extreme droughts in the last decade. This study analyzed the temporal and spatial variations of drought in SC from 1961 to 2012. Based on precipitation anomaly index (PAI) that was derived from 1 km gridded precipitation data, three time scales (month, year and decade) for the drought frequency (DF) and drought area were applied to estimate the spatio-temporal structure of droughts. A time-series analysis showed that winter droughts and spring droughts occurred frequently for almost half of the year from November to March. Summer droughts occasionally occurred in severe drought decades: the 1960s, 1980s and 2000s. During the period of observation, the percent of drought area in SC increased from the 1960s (<5%) to the 2000s (>25%). A total of 57% of the area was affected by drought in 2011, when the area experienced its most severe drought both in terms of area and severity. The spatial analysis, which benefitted from the gridded data, detailed that all of SC is at drought risk except for the central Sichuan Basin. The area at high risk for severe and extreme droughts was localized in the mountains of the junction of Sichuan and Yunnan. The temporal and spatial variability can be prerequisites for drought resistance planning and drought risk management of SC.

Pakistan’s economy is significantly reliant on agriculture. However, Pakistan is included in the most water-stressed countries in the world, and its water resources are considerably vulnerable to climate variability and climate change. Therefore, in the present study, the water resources of the Jhelum River basin, which provides water to 6 million hectares of land of Pakistan and hydropower production, were assessed under the scenarios A2 and B2 of HadCM3. A hydrological model, Hydrologic Modeling System (HEC-HMS), was set up, calibrated, and validated for the Jhelum basin, and then streamflow was simulated for three future periods: 2011–2040, 2041–2070, and 2071–2099. The simulated streamflow of each period was compared with the simulated streamflow of the baseline period (1971–2000) to find the changes in the following indicators: mean flow, low flow, median flow, high flow, and center-of-volume dates (CVDs). The results of the study showed an increase of 10%–15% in the mean annual flow as compared to the baseline flow at the end of this century. Winter, spring, and autumn showed an increase in streamflow at most of the sites in all three periods. However, summer (the monsoon season in the basin) showed decreased streamflow at most of the sites. Maximum increase at Azad Pattan was projected in winter in the 2080s, with about 37%–39% increase in flow under both scenarios. Low and median flows were projected to increase, but a decline in high flow was detected in the future under both scenarios. It was also concluded that half of the annual flow in the basin will pass by the Azad Pattan site one week earlier than it does now. On the whole, the Jhelum basin would face more temporal and magnitudinal variations in high, low, and mean flows relative to present conditions. This shows that without a consideration of climate change impacts, proper utilization and management of water resources in the basin will be more difficult.

Abstract The water bodies existing along highways in the high altitude areas of the Qinghai–Tibet Plateau (QTP) will aggravate subgrade settlement and road damage, and affect the long-term stability of road networks. Based on remote sensing and geographic information system (GIS) techniques, this study analyzed the changes in the number and area of water bodies along the G109 and G219 highways in the QTP in the past 20 years. The results showed that between 2000 and 2019, the number of water bodies along the two highways increased by 24 and 19%, respectively, and their area increased by 26 and 19%, respectively. The area and the number of water bodies &gt;1 km2 in the permafrost area and those &lt;1 km2 in the seasonal permafrost area both changed significantly. The change in the number of water bodies in the permafrost area was positively correlated with annual average temperature, while that in the seasonal permafrost area was significantly positively correlated with annual precipitation. This study provided basic data that could be used in studies on the interrelationship between engineering and water bodies within the context of climate change and will contribute to revealing the mechanisms through which engineering projects affect frozen soils.

Deforestation is currently a widespread phenomenon and a growing environmentalconcern in the era of rapid climate change. In temperate regions, it is challenging toquantify the impacts of deforestation on the catchment dynamics and downstreamaquatic ecosystems such as reservoirs and disentangle these from direct climatechange impacts, let alone project future changes to inform management. Here, wetackled this issue by investigating a unique catchment-reservoir system with tworeservoirs in distinct trophic states (meso- and eutrophic), both of which drain into thelargest drinking water reservoir in Germany. Due to the prolonged droughts in 2015-2018, the catchment of the mesotrophic reservoir lost an unprecedented area of forest(exponential increase since 2015 and ca. 17.1% loss in 2020 alone). We coupledcatchment nutrient exports (HYPE) and reservoir ecosystem dynamics (GOTM-WET)models using a process-based modelling approach. The coupled model was validatedwith datasets spanning periods of rapid deforestation, which makes our futureprojections highly robust. Results show that in a short-term time scale (by 2035),increasing nutrient flux from the catchment due to vast deforestation (80% loss) canturn the mesotrophic reservoir into a eutrophic state as its counterpart. Our resultsemphasize the more prominent impacts of deforestation than the direct impact ofclimate warming in impairment of water quality and ecological services to downstreamaquatic ecosystems. Therefore, we propose to evaluate the impact of climate changeon temperate reservoirs by incorporating a time scale-dependent context, highlightingthe indirect impact of deforestation in the short-term scale. In the long-term scale (e.g.to 2100), a guiding hypothesis for future research may be that indirect effects (e.g., asmediated by catchment dynamics) are as important as the direct effects of climatewarming on aquatic ecosystems.

The Greater and Lesser Khingan Mountains (GKM and LKM), together form one of the main resources of the terrestrial natural ecosystem in northeast Asia and play a crucial role in climate regulation and soil and water conservation due to their distinctive geographical features and abundant vegetation cover. Nonetheless, the morphology and distribution of gullies in the two study areas remain unclear. This study focused on an investigation area of approximately 100 km2 within the forest areas of the GKM and LKM, where field measurements were conducted to record and analyze the morphological characteristics of the gullies. The study also explored the impact of slope and the aspects of gully development and established a gully volume estimation model in the study area. The findings indicate the following. Firstly, that the proportions of gullies with a length of 200–1000 m, a width of 2–6 m and a depth of 1–2 is 59.4%, 51.3% and 45.9%, respectively in the GKM, and 42.5%, 75.7% and 56%, respectively in the LKM. The measured gully density in the GKM was 0.3 gullies per km2, with an average length, width, and depth of 524.4 m, 2.4 m, and 1.0 m, respectively. In contrast, the measured gully density in the LKM was 0.45 gullies per km2, with an average length, width, and depth of 560.1 m, 3.9 m, and 1.8 m, respectively. Secondly, as the slope increased, the density of gullies and the degree of surface fragmentation gradually decreased. In the measured area of the GKM, gullies developed faster on the semi-sunny slope. However, in the measured area of the LKM, gullies were more evenly distributed across different slopes. A significant power function relationship between the volume and area (V-A) of gullies in the measured areas of the GKM (V = 0.37 A1.11, R2 = 0.94) and LKM (V = 0.32 A1.17, R2 = 0.94) was observed. These findings have important implications for soil conversation in forested areas of the black soil region in Northeast China.

The relationship between the interannual changes in streamflow, precipitation and temperature of the Murray-Darling basin is investigated by using a two-parameter climate elasticity of streamflow approach. The non-linear relationship between streamflow and both precipitation and temperature indicates a greater streamflow sensitivity to precipitation than to temperature but a more significant impact of temperature change on streamflow than previously reported. The physical mechanisms producing high streamflow sensitivity to temperature change are not well understood, but may relate to concurrent changes in sub-annual precipitation characteristics such as seasonality, spatial distribution and intensity. Thus these characteristics need to be assessed and accounted for when attempting to project how streamflow, and hence water availability, may change in a future warmer world.

Both central-eastern U.S. and China are prone to increasing flooding from Mississippi River and Yangtze River basins respectively. This paper contrasts historical and projected spatialtemporal distribution of extreme precipitation in these two large river basins using 31 CMIP5 (coupled model intercomparison project phase 5) models’ historical and RCP8.5 (representative concentration pathway) experiments. Results show that (1) over both river basins, the heaviest rainfall events have increased in recent decades while the lightest precipitation reduced in frequency. Over Mississippi River Basin, both the lightest precipitation ( 50 mm/day) would decrease in frequency notably after mid-2020s while intermediate events occur more frequently in future; whereas over the Yangtze River Basin, all categories of precipitation are projected to increase in frequency over the coming decades. (2) Although the consensus of CMIP5 models was able to reproduce well domain-time mean and even time-averaged spatial distribution of precipitation, they failed to simulate precipitation trends both in spatial distribution and time means. In a similar fashion, models captured well statistics of precipitation but they had difficulty in representing temporal variations of different precipitation intensity categories. (3) The well-documented 2nd half of the 20th century surface summer cooling over the two river basins showed different associations with precipitation trends with higher anti-correlation between them over the U.S. region, implying different processes contributing to the cooling mechanisms of the two river basins.

With the impacts of climate disruption becoming more evident there has been an increase in the uptake of climate change adaptation "toolkits" to assist local governments build community resilience and adapt to the impacts of climate change. There is increasing attention and call for practitioners to adopt proactive and participatory approaches to help in the adaptive response planning process. One such toolkit is the International Council for Local Environmental Initiatives (ICLEI) Asian Cities Climate Change Resilience Network (ACCRN) Process (IAP). This is a simple but rigorous toolkit developed to help local governments in Asian cities build resilience to the impacts of climate change. This paper outlines the application of the toolkit to determine its versatility in the rural context and was trialled in the Himalayan rural enclave of Ramgad in the Indian state of Uttarakhand. Given the differences between urban and rural environments, the outcomes highlighted the need for further investigation and analysis into the process to ensure that the methodology truly reflects the nature of rural systems and their level of vulnerability and adaptive capacity. Overall, the toolkit proved to be a simple but versatile toolkit to assess the vulnerability and adaptive capacity of communities in rural Himalaya. Over 40 resilience intervention strategies were developed for the Ramgad enclave and these were prioritized according to their technical, political, social and economic feasibility.

Precision irrigation is a promising method to mitigate the impacts of drought stress on crop production with the optimal use of water resources. However, the reliable assessment of plant water status has not been adequately demonstrated, and unmanned aerial systems (UAS) offer great potential for spatiotemporal improvements. This study utilized UAS equipped with multispectral and thermal sensors to detect and quantify drought stress in winter wheat (Triticum aestivum L.) using the Water Deficit Index (WDI). Biennial field experiments were conducted on coarse sand soil in Denmark and analyses were performed at both diurnal and seasonal timescales. The WDI was significantly correlated with leaf stomatal conductance (R2 = 0.61–0.73), and the correlation was weaker with leaf water potential (R2 = 0.39–0.56) and topsoil water status (the highest R2 of 0.68). A semi-physical model depicting the relationship between WDI and fraction of transpirable soil water (FTSW) in the root zone was derived with R2 = 0.74. Moreover, WDI estimates were improved using an energy balance model with an iterative scheme to estimate the net radiation and land surface temperature, as well as the dual crop coefficient. The diurnal variation in WDI revealed a pattern of the ratio of actual to potential evapotranspiration, being higher in the morning, decreasing at noon hours and ‘recovering’ in the afternoon. Future work should investigate the temporal upscaling of evapotranspiration, which may be used to develop methods for site-specific irrigation recommendations.

The Indo-Pacific Convergence Zone (IPCZ) has a complex ocean dynamical system. All scale processes are active and interplay from small-scale turbulent mixing to basin-scale circulation. The IPCZ acts as an “oceanic bridge” for the inter-basin mass transports and basin-scale planetary waves, closely linking basin-scale circulations in the Pacific and Indian Oceans. Numerous straits in the Indonesian Seas provide oceanic channels for planetary waves propagating between the tropical Pacific and the southeast Indian Ocean. On a large scale, the inter-basin mass transports and planetary waves change the ocean thermal structure, triggering strong air-sea interactions, and further regulating the variability of Walker and Hadley Circulations. The latter form an “atmospheric bridge”, which significantly affects the Asian and Australian monsoon systems and a series of global climate events like El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole, and Indian Ocean Basinwide warming. On meso- and small- scales, eddy, submesoscale processes, and turbulent motions mix the water mass from different sources, dramatically stirring the upper ocean in the IPCZ. Ocean dynamics have essential impacts on the ecological system in the IPCZ. On the one hand, these processes directly affect biodiversity by controlling the genetic exchanges and species dispersals between basins. On the other hand, the ocean dynamical processes influence biogeochemical cycling by controlling the trophic transfer, which further impacts primary productivity. With the intensified climate variations under global warming, e.g., marine heatwaves and extreme events, the ocean dynamical processes turn more active and enhance the influence on the ecosystem. This work overviews a series of studies focusing on the multi-scale ocean dynamical and environmental processes in the IPCZ, including the climatic signatures in coral records and the ecological response. © 2023