Response Analysis Of Climate Change In Northern China Under 1.5°C And 2°C Global Warming

With rapid global warming and intensified human activities,the response of regional-scale climate change is sensitive and complicated.Northern China,a region with shortage of water resources and fragile ecological environment,is urgently needed high-precision and highconfidence regional climate change information to provide reference ideas for addressing and alleviating future climate change.This paper predicts regional climate change in Northern China under global warming 1.5? and 2 ? thresholds and scenarios based on Nanjing University Information Science and Technology Earth System Model(NESM)driven regional model WRF(Weather Research and Forecast),and clarifies the characteristics of impact of different warming thresholds and scenarios on regional climate change in China.Focusing on differences in the responses of climate fields,water and energy budget to global warming thresholds and scenarios in arid,semi-arid and semi-humid sub-regions of Northern China.Drywet change characteristics and its dominant contribution in Northern China is analyzed through moisture budget diagnosis.The main results are as follows:(1)The ability of NESM model and its dynamic downscaling results to simulate climate in China and its northern area is assessed by observation and reanalysis datasets and shows that,compared with NESM,WRF describes the local features of temperature and precipitation better in Northern China,and has greater correlation coefficient and root mean squared error with observation.Besides,WRF can capture spatial distribution of evaporation and runoff,and improve seasonal change of water and energy budget components simulated by NESM.In general,the performance of WRF model for China and its northern region is reliable.(2)The response of climate in China and its northern area under 1.5? and 2? global warming is analyzed through WRF dynamic downscaling simulations.It is found that compared with climate in 1985-2014,the summer temperature rise decreases from north to south,which exceeds 1.6? in the most parts of Northern China,surface net radiation increases 0.6% under stabilized 1.5? warming scenario.Precipitation basically increases throughout China,with a significant rise of more than 20% in arid area,which generally lower than 10% in semi-arid and semi-humid areas.Precipitation and water budget components have consistently spatial distribution of variation,and former dominates the form that transfer of heat from surface to atmosphere changes from sensible heat flux in arid area to latent heat flux in semi-humid area.Under an additional 0.5? warming,the Tarim Basin,the southern Qinghai-Tibet Plateau and Jianghuai region appear warming centers over 0.7?.The increase of water vapor is conducive to further addition of 10% in precipitation.In the most parts of region,net radiation and sensible heat flux would decrease and latent heat flux increase.When reached 2? threshold by transient warming scenario,temperature marked rises in Northeast China and slightly reduces in other areas compared to stabilized warming scenario.Precipitation increase varies inhomogeneously in space,southward shift and weakening of westerly jet might be one of reasons of discrepancy of precipitation change between different warming scenarios.(3)The research further analyzes the response mechanism of summer dry-wet changes in arid to semi-humid area of Northern China under stabilized 1.5? and 2? warming scenario.Spatial distribution of dry-wet climate change in Northern China is influenced by precipitation.The increase of precipitation minus evaporation rises with warming threshold,and decreases from west to east in space.Results of moisture diagnosis illustrate that,under stabilized 1.5?warming scenario,thermodynamic term dominates increase of precipitation minus evaporation in arid area,and semi-arid area led by dynamic term.Dry-wet change in semi-humid mainly comes from reduce of precipitation and enhancement of evaporation,corresponding decrease of dynamic term.While warming threshold up to 2?,the rise of precipitation minus evaporation in Northern China is mainly contributed by thermodynamic term,corresponding to increase of water vapor under warmer climate.In the warming future,increase of soil moisture strengthens evaporation,leading water vapor in lower troposphere increase,which is conducive to the climate change to a wetter state.Heightened local land-atmosphere coupling could also increase atmospheric water vapor content.The changes of meridional position of East Asian jet stream and intensity of monsoons would affect westerly and divergence of wind field in lower troposphere on water vapor transport and dynamic condition of precipitation in Northern China,further influence precipitation and dry-wet climate change.