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Statistical Downscaling Based on Dynamically Downscaled Predictors: Application to Monthly Precipitation in Sweden

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Advances in Atmospheric Sciences 2003年第6期20卷 951-958页

作者： Cecilia HELLSTROM deliang chen EarthSciencesCentre GothenburgUniversityGothenburgSweden NationalClimateCenter ChinaMeteorologicalAdministrationBeijingChina

A prerequisite of a successful statistical downscaling is that large-scale predictors simulated by the General Circulation Model (GCM) must be realistic. It is assumed here that features smaller than the GCM resolution are important in determining the realism of the large-scale predictors. It is tested whether a three-step method can improve conventional one-step statistical downscaling. The method uses predictors that are upscaled from a dynamical downscaling instead of predictors taken directly from a GCM simulation. The method is applied to downscaling of monthly precipitation in Sweden. The statistical model used is a multiple regression model that uses indices of large-scale atmospheric circulation and 850-hPa specific humidity as predictors. Data from two GCMs (HadCM2 and ECHAM4) and two RCM experiments of the Rossby Centre model (RCA1) driven by the GCMs are used. It is found that upscaled RCA1 predictors capture the seasonal cycle better than those from the GCMs, and hence increase the reliability of the downscaled precipitation. However, there are only slight improvements in the simulation of the seasonal cycle of downscaled precipitation. Due to the cost of the method and the limited improvements in the downscaling results, the three-step method is not justified to replace the one-step method for downscaling of Swedish precipitation.

关键词： downscaling multiple regression atmospheric circulation indices monthly precipitation Sweden

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保持土壤湿度对减缓气候变化重要性

Science Bulletin 2024年第9期69卷 1332-1341页

作者：左志燕乔梁张人禾陈德亮朴世龙肖栋张楷文 Key Laboratory of Polar Atmosphere-ocean-ice System for Weather and Climate of Ministry of Education/Shanghai Key Laboratory of Ocean-Land-Atmosphere Boundary Dynamics and Climate Change Department of Atmospheric and Oceanic Sciences/Institute of Atmospheric SciencesFudan UniversityShanghai 200438China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and TechnologyNanjing 210044China Department of Earth Sciences University of GothenburgGothenburg 40530Sweden Sino-French Institute for Earth System Science College of Urban and Environmental SciencesPeking UniversityBeijing 100091China Key Laboratory of Cites’Mitigation and Adaptation to Climate Change in Shanghai China Meteorological AdministrationShanghai 200030China

A troubling feedback loop, where drier soil contributes to hotter climates, has been widely *** study, drawing on climate model simulations, reveals that maintaining current global soil moisture levels could significantly alleviate 32.9% of land warming under low-emission scenarios. This action could also postpone reaching critical warming thresholds of 1.5 °C and 2.0 °C by at least a decade. Crucially,preserving soil moisture at current levels could prevent noticeable climate change impacts across 42%of the Earth's land, a stark deviation from projections suggesting widespread impacts before the *** combat soil drying, afforestation in mid-to-low latitude regions within the next three decades is proposed as an effective strategy to increase surface water availability. This underscores the substantial potential of nature-based solutions for managing soil moisture, benefiting both climate change mitigation and ecological enhancement.

关键词： Global warming Soil moisture Climate change signal Nature-based solutions

Climate-Induced Variability of Sea Level in Stockholm: Influence of Air Temperature and Atmospheric Circulation

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Advances in Atmospheric Sciences 2005年第5期22卷 655-664页

作者： deliang chen Anders OMSTEDT Earth Sciences Centre Goteborg University Sweden Laboratory for Climate Studies/National Climate Center China Meteorological Administration Beijing 100081

This study is focused on climate-induced variation of sea level in Stockholm during 1873-1995. After the effect of the land uplift, is removed, the residual is characterized and related to large-scale temperature and atmospheric circulation. The residual shows an overall upward trend, although this result depends on the uplift rate used. However, the seasonal distribution of the trend is uneven. There are even two months （June and August） that show a negative trend. The significant trend in August may be linked to fresh water input that is controlled by precipitation. The influence of the atmospheric conditions on the sea level is mainly manifested through zonal winds, vorticity and temperature. While the wind is important in the period January-May, the vorticity plays a main role during June and December. A successful linear multiple-regression model linking the climatic variables （zonal winds, vorticity and mean air temperature during the previous two months） and the sea level is established for each month. An independent verification of the model shows that it has considerable skill in simulating the variability.

关键词： sea level Baltic sea atmospheric circulation temperature Stockholm

Co-varying temperatures at 200 hPa over the Earth’s three poles

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Science China Earth Sciences 2021年第2期64卷 340-350页

作者： Keyan FANG Peng ZHANG Jingming chen deliang chen Key Laboratory of Humid Subtropical Eco-geographical Process(Ministry of Education) College of Geographical SciencesFujian Normal UniversityFuzhou 350007China Regional Climate Group Department of Earth SciencesUniversity of GothenburgBox 460S-40530 GothenburgSweden Department of Geography and Program in Planning University of Toronto100 St.George St.TorontoOntarioCanada

The Earth’s three poles,the North Pole,South Pole,and Third Pole(i.e.,the Tibetan Plateau and its surroundings),hold the largest amount of fresh water on Earth as glaciers,sea ice,and *** are sensitive to climate ***,the linkages between climate variations of the three poles,particularly between the South Pole and Third Pole,remain largely *** temperatures at 200 hPa over the three poles are the highest in the summer and are less affected by surface conditions,which could reflect large-scale dynamic *** at 200 hPa peak the three poles during their respective hemispheric summer and exhibit in-phase variations on interdecadal timescales(10–100 years).The 200 hPa temperatures over the North Pole and South Pole were significantly correlated with the Brewer-Dobson circulation(BDC),which transports stratospheric ozone poleward,heating the air at 200 *** warming over the Third Pole was found to enhance the poleward BDC,particularly to the South Pole,linking the Third Pole’s climate to the other two ***,the Interdecadal Pacific Oscillation(IPO)also exhibits links with the 200 hPa temperatures of the three poles.

关键词： Three poles Tibetan Plateau Brewer-Dobson circulation Interdecadal Pacific Oscillation Climate teleconnection

Climate change and its impact on the Third Pole and beyond

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Advances in Climate Change Research 2021年第3期12卷 297-298页

作者： deliang chen YAO Tan-Dong Department of Earth Sciences University of GothenburgGothenburg40530Sweden Institute of Tibetan Plateau Research Chinese Academy of SciencesBeijing100101China

After the North and South Poles,the Third Pole is the highland core of Asia and includes the Hindu-Kush,Karakorum,Himalayas,Tibetan Plateau,and all the mountain ranges that surround *** region provides water resources and ecosystem services to billions of people in *** is well accepted that the region has undergone climate warming that is larger than the means of the Northern Hemisphere and other regions at similar latitudes over the last *** resulted in some environmental changes,having huge implications for millions of people living in the Third Pole region and downstream areas.

关键词： Pole latitude Tibetan

Trends in Graded Precipitation in China from 1961 to 2000

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Advances in Atmospheric Sciences 2008年第2期25卷 267-278页

作者：符娇兰钱维宏林祥 deliang chen Monsoon and Environment Research Group School of Physics Peking University Beijing 100871 Earth Sciences Centre Gothenburg University Box 460 405 30 Gothenburg Sweden Laboratory for Climate Studies/National Climate Center China Meteorological Administration No. 46 Zhongguancun Nandajie Beijing 100081

Daily precipitation rates observed at 576 stations in China from 1961 to 2000 were classified into six grades of intensity, including trace （no amount）, slight （≤ 1 mm d^-1）, small, large, heavy, and very heavy. The last four grades together constitute the so called effective precipitation （〉 1 mm d^-1）. The spatial distribution and temporal trend of the graded precipitation days are examined. A decreasing trend in trace precipitation days is observed for the whole of China, except at several sites in the south of the middle section of the Yangtze River, while a decreasing trend in slight precipitation days only appears in eastern China. The decreasing trend and interannual variability of trace precipitation days is consistent with the warming trend and corresponding temperature variability in China for the same period, indicating a possible role played by increased surface air temperature in cloud formation processes. For the effective precipitation days, a decreasing trend is observed along the Yellow River valley and for the middle reaches of the Yangtze River and Southwest China, while an increasing trend is found for Xinjiang, the eastern Tibetan Plateau, Northeast China and Southeast China. The decreasing trend of effective precipitation days for the middle- lower Yellow River valley and the increasing trend for the lower Yangtze River valley are most likely linked to anomalous monsoon circulation in East China. The most important contributor to the trend in effective precipitation depends upon the region concerned.

关键词： trends graded precipitation days intensity effective precipitation warming China

Statistical Downscaling of Summer Temperature Extremes in Northern China

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Advances in Atmospheric Sciences 2013年第4期30卷 1085-1095页

作者：范丽军 deliang chen 符淙斌严中伟 Key Laboratory of Regional Climate-Environment Research for Temperate East Asia Institute of Atmospheric Physics Chinese Academy of Science Department of Earth Sciences University of Gothenburg

Two approaches of statistical downscaling were applied to indices of temperature extremes based on percentiles of daily maximum and minimum temperature observations at Beijing station in summer during 1960-2008. One was to downscale daily maximum and minimum temperatures by using EOF analysis and stepwise linear regression at first, then to calculate the indices of extremes; the other was to directly downseale the percentile-based indices by using seasonal large-scale temperature and geo-potential height records. The cross-validation results showed that the latter approach has a better performance than the former. Then, the latter approach was applied to 48 meteorological stations in northern China. The cross- validation results for all 48 stations showed close correlation between the percentile-based indices and the seasonal large-scale variables. Finally, future scenarios of indices of temperature extremes in northern China were projected by applying the statistical downsealing to Hadley Centre Coupled Model Version 3 （HadCM3） simulations under the Representative Concentration Pathways 4.5 （RCP 4.5） scenario of the Fifth Coupled Model Inter-comparison Project （CMIP5）. The results showed that the 90th percentile of daily maximum temperatures will increase by about 1.5℃, and the 10th of daily minimum temperatures will increase by about 2℃ during the period 2011- 35 relative to 1980-99.

关键词： indices of temperature extremes percentiles statistical downscaling future scenarios projection. northern China

Surface energy budget diagnosis reveals possible mechanism for the different warming rate among Earth’s three poles in recent decades

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Science Bulletin 2019年第16期64卷 1140-1143页

作者： Kailun Gao Anmin Duan deliang chen Guoxiong Wu State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Regional Climate Group Department of Earth SciencesUniversity of GothenburgGothenburg 40530Sweden

With the introduction of the‘‘Third Pole'[1],the Arctic,Antarctic,and Tibetan Plateau(TP)can be collectively referred to as the‘‘three poles of the Earth'.The cryosphere is an important component of the climate system because of its effect on Earth’s surface albedo and its role in reducing the amount of heat exchanged between the atmosphere and ocean or land(2)As the dominant parts of the cryosphere,the Arctic,Antarctic,and TP are pivotal and sensitive areas of global climate *** warming will weaken the inherent stability of the cryosphere,such as its ice shelves,glaciers and permafrost[3,4].

关键词： energy budget warming Earth’s three poles

Towards climate resilient urban energy systems: a review

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National Science Review 2021年第3期8卷 159-176页

作者： Vahid M.Nik A.T.D.Perera deliang chen Division of Building Physics Department of Building and Environmental Technology Lund University Institute for Future Environments(IFE) Queensland University of Technology(QUT) Regional Climate Group Department of Earth SciencesUniversity of Gothenburg Division of Building Technology Department of Architecture and Civil Engineering Chalmers University of Technology Solar Energy and Building Physics Laboratory(LESO-PB) Ecole Polytechnique Federale de Lausanne(EPFL) Urban Energy Systems Laboratory

Climate change and increased urban population are two major concerns for *** towards more sustainable energy solutions in the urban context by integrating renewable energy technologies supports decarbonizing the energy sector and climate change mitigation.A successful transition also needs adequate consideration of climate change including extreme events to ensure the reliable performance of energy systems in the long *** review provides an overview of and insight into the progress achieved in the energy sector to adapt to climate change,focusing on the climate resilience of urban energy *** state-of-the-art methodology to assess impacts of climate change including extreme events and uncertainties on the design and performance of energy systems is described and *** resilience is an emerging concept that is increasingly used to represent the durability and stable performance of energy systems against extreme climate ***,it has not yet been adequately explored and widely used,as its definition has not been clearly articulated and assessment is mostly based on qualitative *** study reveals that a major limitation in the state-of-the-art is the inadequacy of climate change adaptation approaches in designing and preparing urban energy systems to satisfactorily address plausible extreme climate ***,the complexity of the climate and energy models and the mismatch between their temporal and spatial resolutions are the major limitations in linking these ***,few studies have focused on the design and operation of urban energy infrastructure in terms of climate *** the occurrence of extreme climate events and increasing demand for implementing climate adaptation strategies,the study highlights the importance of improving energy system models to consider future climate variations including extreme events to identify climate resilient energy transition pathways.

关键词： climate resilience climate change adaptation urban energy systems renewable energy extreme events decentralized generation