Evolution of drought and flood events on the Qinghai-Tibet Plateau and key issues for response

The Qinghai-Tibet Plateau is a climate-sensitive region.The characteristics of drought and flood events in this region are significantly different as compared to other areas in the country,which could potentially induce a series of water security,ecological and environmental problems.It is urgent that innovative theories and methods for estimation of drought and flood disasters as well as their adaptive regulations are required.Based on extensive literature review,this paper identifies new situations of the evolution of drought and flood events on the Qinghai-Tibet Plateau,and analyzes the research progress in terms of monitoring and simulation,forecasting and early warning,risk prevention and emergency response.The study found that there were problems such as insufficient integration of multi-source data,low accuracy of forecasting and early warning,unclear driving mechanisms of drought and flood disaster chains,and lack of targeted risk prevention and regulation measures.On this basis,future research priorities are proposed,and the possible research and development paths are elaborated,including the evolution law of drought and flood on the Qinghai-Tibet Plateau,the coincidence characteristics of drought and flood from the perspective of a water resources system,prediction and early warning of drought and flood coupled with numerical simulation and knowledge mining,identification of risk blocking points of drought and flood disaster chain and the adaptive regulations.Hopefully,the paper will provide technical support for preventing flood and drought disasters,water resources protection,ecological restoration and climate change adaptation on the Qinghai-Tibet Plateau.

Response of vegetation phenology to climate factors in the source region of the Yangtze and Yellow Rivers

Exploring the impact of climate factors on vegetation phenology is crucial to understanding climate–vegetation interactions as well as carbon and water cycles in ecosystems in the context of climate change.In this article,we extracted the vegetation phenology data from 2002 to 2021 based on the dynamic threshold method in the source region of the Yangtze and Yellow Rivers.Trend and correlation analyses were used to investigate the relationship between vegetation phenology and temperature,precipitation and their spatial evolution characteristics.The results showed that:(i)From 2002 to 2021,the multi-year average start of growing season(SOS),end of growing season(EOS)and length of growing season(LOS)for plants were concentrated in May,October and 4–6 months,with a trend of 4.9 days(earlier),1.5 days(later),6.3 days/10 a(longer),respectively.(ii)For every 100 m increase in elevation,SOS,EOS and LOS were correspondingly delayed by 1.8 days,advanced by 0.8 days and shortened by 2.6 days,respectively.(iii)The impacts of temperature and precipitation on vegetation phenology varied at different stages of vegetation growth.Influencing factors of spring phenology experienced a shift from temperature to precipitation,while autumn phenology experienced precipitation followed by temperature.(iv)The climate factors in the previous period significantly affected the vegetation phenology in the study area and the spatial variability was obvious.Specifically,the temperature in April significantly affected the spring phenology and precipitation in August widely affected the autumn phenology.

High-operating-temperature mid-infrared photodetectors via quantum dot gradient homojunction

Due to thermal carriers generated by a narrow mid-infrared energy gap,cooling is always necessary to achieve ideal photodetection.In quantum dot(QD),the electron thermal generation should be reduced with quantum confinement in all three dimensions.As a result,there would be a great potential to realize high-operating-temperature(HOT)QD mid-IR photodetectors,though not yet achieved.Taking the advantages of colloidal nanocrystals’solution processability and precise doping control by surface dipoles,this work demonstrates a HOT mid-infrared photodetector with a QD gradient homojunction.The detector achieves background-limited performance with D^(*)=2.7×1011 Jones on 4.2μm at 80 K,above 10^(11) Jones until 200 K,above 10^(10 )Jones until 280 K,and 7.6×10^(9) Jones on 3.5μm at 300 K.The external quantum efficiency also achieves more than 77%with responsivity 2.7 A/W at zero bias.The applications such as spectrometers,chemical sensors,and thermal cameras,are also approved,which motivate interest in low-cost,solution-processed and high-performance mid-infrared photodetection beyond epitaxial growth bulk photodetectors.