Disaster effects of climate change in High Mountain Asia:State of art and scientific challengesDisaster effects of climate change in High Mountain Asia:State of art and scientific challenges

High Mountain Asia(HMA)shows a remarkable warming tendency and divergent trend of regional precipitation with enhanced meteorological extremes.The rapid thawing of the HMA cryosphere may alter the magnitude and frequency of nature hazards.We reviewed the influence of climate change on various types of nature hazards in HMA region,including their phenomena,mechanisms and impacts.It reveals that:1)the occurrences of extreme rainfall,heavy snowfall,and drifting snow hazards are escalating;accelerated ice and snow melting have advanced the onset and increased the magnitude of snowmelt floods;2)due to elevating trigger factors,such as glacier debuttressing and the rapid shift of thermal and hydrological regime of bedrock/snow/ice interface or subsurface,the mass flow hazards including bedrock landslide,snow avalanche,ice-rock avalanches or glacier detachment,and debris flow will become more severe;3)increased active-layer detachment and retrogressive thaw slumps slope failures,thaw settlement and thermokarst lake will damage many important engineering structures and infrastructure in permafrost region;4)multi-hazards cascading hazard in HMA,such as the glacial lake outburst flood(GLOF)and avalanche-induced mass flow may greatly enlarge the destructive power of the primary hazard by amplifying its volume,mobility,and impact force;and 5)enhanced slope instability and sediment supply in the highland areas could impose remote catastrophic impacts upon lowland regions,and threat hydropower security and future water shortage.In future,ongoing thawing of HMA will profoundly weaken the multiple-phase material of bedrock,ice,water,and soil,and enhance activities of nature hazards.Compounding and cascading hazards of high magnitude will prevail in HMA.As the glacier runoff overpasses the peak water,low flow or droughts in lowland areas downstream of glacierized mountain regions will became more frequent and severe.Addressing escalating hazards in the HMA region requires tackling scientific challenges,including understanding multiscale evolution and formation mechanism of HMA hazard-prone systems,coupling thermo‒hydro‒mechanical processes in multi-phase flows,predicting catastrophes arising from extreme weather and climate events,and comprehending how highland hazards propagate to lowlands due to climate change.

Disastrous effects of climate change on High Mountain Asia

High Mountain Asia(HMA),encompassing the Tibetan Plateau and the surrounding high mountain ranges of the Hindu Kush and Tianshan,is a region characterised by large terrain,complex topography and the interplay of various climatic systems,includinggunique westerly-monsoon-terrain interactions.

Extreme precipitation detection ability of four high-resolution precipitation product datasets in hilly area:a case study in Nepal

Given Nepal's vulnerability to extreme precipitation(EP),it is imperative to conduct a comprehensive analysis to comprehend the historical trends of such events.However,acquiring precise precipitation data for EP remains challenging in mountainous countries like Nepal owing to the scarcity of densely gauged networks.This limitation impedes the dissemination of knowledge pertaining to EP variability events in Nepal.The current research on this topic is deficient for two main reasons:1)there is a lack of studies leveraging recently released high-resolution precipitation products to identify their EP detection capabilities,which further hinders the usability of those products in data-scarce regions like Nepal,and 2)most studies have focused on the characterisation of EP events in Nepal rather than their spatial and temporal variability.To address these issues,this study evaluated the EP detection capabilities of four high-resolution precipitation product datasets(PPDs)across Nepal from 1985 to 2020.These datasets include the ERA5 Land reanalysis data,satellite-based precipitation data(PERSIANN_CCS_CDR and CHIRPS_V2.0)and a merged dataset(TPHiPr).We used various statistical and categorical indices to assess their ability to capture the spatial and temporal variability of EP events.The annual EP events were characterised by 11 indices divided into frequency and intensity categories.The TPHiPr merged dataset offered a robust depiction of monthly precipitation estimates,achieving the highest critical success index,accuracy,probability of detection and a low false alarm ratio for daily precipitation detection of 0.1 mm in Nepal.Conversely,the PERSIANN_CCS_CDR dataset exhibited poor performance.Most PPDs showed increasing trends in EP indices.However,the TPHiPr dataset showcased those trends with fewer errors and stronger correlations for many frequency(R10mm,R20mm and R25mm)and intensity(RX1day,RX5day,PRCPTOT and R99p)indices.The results indicate that TPHiPr outperformed other PPDs in accurately representing the spatial distribution of EP trends in Nepal from 1985 to 2020,particularly noting an exacerbation of EP events mostly in the eastern region of Nepal throughout the study period.While TPHiPr demonstrated superior performance in detecting various EP indices across Nepal,individual products like the ERA5 Land reanalysis dataset showed enhanced performance in the western region of Nepal.Conversely,PERSIANN_CCS_CDR and CHIRPS_V2.0 performed well in the eastern region compared to other PPDs.

Links between winter dust over the Tibetan Plateau and preceding autumn sea ice variability in the Barents and Kara Seas

The Tibetan Plateau(TP)is characterized by heavily local dust activities,however,the mechanism of interannual variations of winter dust frequency over the TP remain poorly understood.Previous studies showed the autumn Arctic sea ice could significantly influence the winter climate over Eurasia.Whether autumn sea ice affects winter dust activity over the TP or not?Here,we used an integrated surface database to investigate possible mechanisms for interannual variability in the frequency of winter dust events above the TP.This variability,which is thought to be mainly caused by local dust emissions,shows significant correlations with sea ice concentration(SIC)in the Barents and Kara Seas during the preceding autumn.Low Barents-Kara SIC is accompanied by reduced snow depth over northern Eurasia between autumn and winter,which can enhance the Eurasian mid-latitude westerly jet stream.This strengthening increases the cyclogenesis and occurrence of strong surface wind speeds in winter,especially over the TP.In addition,a lower SIC is closely associated with reduced precipitation and snow cover in late autumn and winter over the TP,which in turn enhances warming of the land surface and reduces the area of frozen ground.These anomalies in atmospheric circulation patterns and local surface conditions promote dust events above the TP during winter.The ensemble means of Atmospheric Model Intercomparison Project experiments from Phase 6 of the Coupled Model Inter-comparison Project and the Community Atmosphere Model version 4 can generally reproduce the atmospheric circulation anomalies associated with decreased Barents-Kara SIC.This study reveals the crucial effect that SIC anomalies in the Barents and Kara Seas have on winter dust activities over the TP.