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Physical mechanism of the rapid increase in intense and long-lived extreme heatwaves in the Northern Hemisphere since 1980

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Science China Earth Sciences 2024年第7期67卷 2103-2121页

作者： Yuqing WANG Wen ZHOU Chunzai WANG Key Laboratory of Polar Atmosphere-ocean-ice System for Weather and Climate of the MOE Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric SciencesFudan UniversityShanghai 200438China Key Laboratory for Polar Science of the MNR Polar Research Institute of ChinaShanghai 201209China State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Global Ocean and Climate Research Center South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China

Since 1980,both the intensity and duration of summer heatwaves in the middle and high latitudes of the Northern Hemisphere have significantly increased,leading this region to become a critical area for a significant increase in the frequency of intense and long-lived extreme heatwaves.We found that stronger and more persistent high-pressure systems and lower soil moisture before the events were the main drivers of intense and long-lived extreme heatwaves in western Europe and the middle and high latitudes of North America.However,in eastern Europe and Siberia,lower cloud cover before events is also a main driver of this type of extreme heatwave,in addition to the above drivers.These factors are coupled with each other and can change heatwave intensity and duration by influencing surface radiation processes during events.Using the self-organizing map classification method,we found that 6 weather patterns with increased frequency,intensity,and duration were the main dynamic reasons leading to the increase in intense and long-lived extreme heatwaves after 1980.In addition,the decrease in summer average soil moisture in most areas of the mid-high latitudes of the Northern Hemisphere and the decrease in average cloud cover in eastern Europe and Siberia are found to be the main thermodynamic reasons leading to the increase in these extreme heatwaves.

关键词： High intensity Long duration Extreme heatwaves High pressure system Soil moisture cloud cover

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Temporal and spatial variation of cloud cover in arid regions of Central Asia in the last 40 years

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Research in Cold and Arid Regions 2023年第2期15卷 66-72页

作者： KaiLiang Zhao GuoFeng Zhu LiYuan Sang JiaWei Liu Lei Wang YuWei Liu YuanXiao Xu XinRui Lin WenHao Zhang LinLin Ye College of Geography and Environmental Science Northwest Normal UniversityLanzhouGansu 730070China Shiyang River Ecological Environment Observation Station Northwest Normal UniversityLanzhouGansu 730070China Lanzhou Sub-Center Remote Sensing Application CenterMinistry of AgricultureLanzhouGansu 730000China

Water resources are one of the key factors restricting the development of arid areas,and cloud water resources is an important part of water resources.The arid region of central Asia is the core region of the current national green silk road construction,and is the largest arid region in the world.Based on cloud cover data of ECMWF,the current study analyzed temporal and spatial characteristics of cloud properties in arid regions of Central Asia between 1980 and 2019.Our findings show that:(1)From the point of view of spatial distribution,total cloudiness in arid regions of Central Asia was low in the south and high in the north.The distribution of high cloud frequency and medium cloud frequency was higher in the south and lower in the north,while low cloud frequency distribution was low in the south and high in the north.(2)In terms of time,the variation of cloud cover and cloud type frequency had obvious seasonal characteristics.From winter to spring,cloud cover increased,and the change of cloud type frequency increased.From spring to summer,cloud cover continued to increase and the change of cloud type frequency increased further.cloud cover began to decrease from summer to autumn,and the change of cloud type frequency also decreased.(3)Generally,average total cloud cover decreased in most of central Asia,and high and medium cloud cover increased while low cloud cover decreased.This study provides a reference for the rational development of cloud resources in the region.

关键词： Central Asia cloud cover Temporal and spatial changes cloud type frequency

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Comparison between MODIS-derived Day and Night cloud cover and Surface Observations over the North China Plain

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Advances in Atmospheric Sciences 2018年第2期35卷 146-157页

作者： Xiao ZHANG Saichun TAN Guangyu SHI State Key Laboratory of Numerical Modeling of Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and Technology Nanjing 210044 China University of Chinese Academy of Sciences Beijing 100049 China

Satellite and human visual observation are two of the most important observation approaches for cloud cover. In this study, the total cloud cover （TCC） observed by MODIS onboard the Terra and Aqua satellites was compared with Synop meteorological station observations over the North China Plain and its surrounding regions for 11 years during daytime and 7 years during nighttime. The Synop data were recorded eight times a day at 3-h intervals. Linear interpolation was used to interpolate the Synop data to the MODIS overpass time in order to reduce the temporal deviation between the satellite and Synop observations. Results showed that MODIS-derived TCC had good consistency with the Synop observations; the correlation coefficients ranged from 0.56 in winter to 0.73 in summer for Terra MODIS, and from 0.55 in winter to 0.71 in summer for Aqua MODIS. However, they also had certain differences. On average, the MODIS-derived TCC was 15.16% higher than the Synop data, and this value was higher at nighttime （15.58%-16.64%） than daytime （12.74%-14.14%）. The deviation between the MODIS and Synop TCC had large seasonal variation, being largest in winter （29.53%-31.07%） and smallest in summer （4.46%-6.07%）. Analysis indicated that cloud with low cloud-top height and small cloud optical thickness was more likely to cause observation bias. Besides, an increase in the satellite view zenith angle, aerosol optical depth, or snow cover could lead to positively biased MODIS results, and this affect differed among different cloud types.

关键词： cloud cover MODIS cloud-top height cloud optical thickness aerosol optical depth view zenith angle

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Decomposition of Fast and Slow cloud Responses to Quadrupled CO_(2)Forcing in BCC–AGCM2.0 over East Asia

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Advances in Atmospheric Sciences 2022年第12期39卷 2188-2202页

作者： Xixun ZHOU Bing XIE Hua ZHANG Jingyi HE Qi CHEN State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081China University of Chinese Academy of Sciences Beijing 100049China Laboratory for Climate Studies of China Meteorological Administration National Climate CenterBeijing 100081China

In this study,the decomposed fast and slow responses of clouds to an abruptly quadrupled CO_(2)concentration(approximately 1139 ppmv)in East Asia(EA)are obtained quantitatively by using a general circulation model,BCC–AGCM2.0.Our results show that in the total response,the total cloud cover(TCC),low cloud cover(LCC),and high cloud cover(HCC)all increased north of 40°N and decreased south of 40°N except in the Tibetan Plateau(TP).The mean changes of the TCC,LCC,and HCC in EA were–0.74%,0.38%,and–0.38%in the total response,respectively;1.05%,–0.03%,and 1.63%in the fast response,respectively;and–1.79%,0.41%,and–2.01%in the slow response,respectively.By comparison,we found that changes in cloud cover were dominated by the slow response in most areas in EA due to the changes in atmospheric temperature,circulation,and water vapor supply together.Overall,the changes in the cloud forcing over EA related to the fast and slow responses were opposite to each other,and the final cloud forcing was dominated by the slow response.The mean net cloud forcing(NCF)in the total response over EA was–1.80 W m^(–2),indicating a cooling effect which partially offset the warming effect caused by the quadrupled CO_(2).The total responses of NCF in the TP,south China(SC),and northeast China(NE)were–6.74 W m^(–2),6.11 W m^(–2),and–7.49 W m^(–2),respectively.Thus,the local effects of offsetting or amplifying warming were particularly obvious.

关键词： cloud cover cloud forcing quadrupled CO_(2) fast and slow responses

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Absence of the Impact of the Flux of Cosmic Rays and the cloud cover on the Energy Balance of the Earth

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Journal of Atmospheric Science Research 2020年第3期3卷 1-7页

作者： H.I.Abdussamatov Pulkovo Observatory of the RAS St.Petersburg196140Russia

The energy of solar radiation absorbed by the Earth,as well as the thermal radiation of the Earth’s surface,which is released to the space through the atmospheric transparency window,depends on variations of the area of the cloud cover.Svensmark et al.suggest that the increase in the area of the cloud cover in the lower atmosphere,presumably caused by an increase in the flux of galactic cosmic rays during the quasi-bicentennial minimum of solar activity,results only in an increase in the fraction of the solar radiation reflected back to the space and weakens the flux of the solar radiation that reached the Earth surface.It is suggested,without any corresponding calculations of the variations of the average annual energy balance of the EarthЕ,that the consequences will include only a deficit of the solar energy absorbed by the Earth and a cooling of the climate up to the onset of the Little Ice Age.These suggestions ignore simultaneous impact of the opposite aspects of the increase in the area of the cloud cover on the climate warming.The latter will result from a decrease in the power of thermal radiation of the Earth’s surface released to the space,and also in the power of the solar radiation reflected from the Earth’s surface,due to the increase in their absorption and reflection back to the surface.A substantial strengthening in the greenhouse effect and the narrowing of the atmospheric transparency window will also occur.Here,we estimate the impact of all aspects of possible long-term 2%growth of the cloud cover area in the lower atmosphere byЕ.We found that an increase in the cloud cover area in the lower atmosphere will result simultaneously both in the decrease and in the increase in the temperature,which will virtually compensate each other,while the energy balance of the Earth E before and after the increase in the cloud cover area by 2%will stay essentially the same:E1-E0≈0.

关键词： Climate Cosmic rays cloud cover Energy Balance Little Ice Age Solar Irradiance Greenhouse Effect Atmospheric Transparency Window

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Development of cloud Movement Prediction Method for Solar Photovoltaic System

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Journal of Harbin Institute of Technology(New Series) 2022年第1期29卷 64-69页

作者： Fei Lu Siaw Yaw Yoong Sia Mallikarachchi Dilshani Center for Advanced Electrical and Electronic Systems(CAEES) Faculty of EngineeringBuilt Environment and Information TechnologySEGi UniversityKota DamansaraPetaling Jaya 47810Malaysia

Variability of power generation due to the prevalence of cloud cover over solar photovoltaics(PV)power plants is a challenge faced by grid operators and independent system operators(ISOs)in the integration of solar energy into the grid.Solar forecasts generated through ground⁃based sky imaging systems are useful for short⁃term cloud motion predictions.However,the cost of sky imaging systems currently available in industries is relatively high.Hence,a ground⁃based camera system utilizing a simple webcam is proposed in this study.The proposed method can produce predictions with high levels of accuracy.Forecasts were generated through video analysis using MATLAB for the computation of cloud motion predictions.The image processing involved in the implementation of the proposed system is based on the detection of cloud regions in the form of a cluster of white pixels within individual frames and tracking their motion through comparison of subsequent frames.This study describes the techniques and processes used in the development of the proposed method,along with the evaluation of performance through analysis of the results.The predictions were carried out over multiple time horizons.The time horizons selected include 5,10,15,20,25,and 30 s.The overall results computed showed promising accuracy levels above 94.60%,which makes it adequate for generating reliable forecasts.

关键词： forecast solar photovoltaic cloud cover MATLAB

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Variations and Influence of cloud cover in Heze Region in Recent 52 Years

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Meteorological and Environmental Research 2015年第11期6卷 6-8,15页

作者： Dou Kun Heze Meteorological Bureau of Shandong Province

Based on the data of cloud cover, precipitation, temperature, sunshine hours and relative humidity from nine ground meteorological stations in Heze region in the southwest of Shandong Province from 1961 to 2012, changes of total and low cloud cover and its relationship with climatic factors associated in the southwest of Shandong Province in recent 52 years were analyzed. The results showed that average total cloud cover in- creased by 0.89%/10 a, but average low cloud cover decreased by 1.1%/10 a in Heze region in recent 52 years. The positive correlation between the average total cloud cover and temperature in autumn and winter was obvious, that is, when cloud cover increased by 10%, the average temper- ature increased by 0.48 ~C in autumn and increased by 0.83~（3 in winter. The average low. cloud cover negatively correlated with the average tam- perature in each season, and the negative correlation was very significant in spring. When cloud cover increased by 10%, the average temperature decreased by 1.49 ~C. The positive correlation between the average cloud cover and average precipitation was significant. The annual precipitation increased by 148.1 mm when annual mean total cloud cover increased by 10%. When seasonal mean cloud cover increased by 10%, the precipita- tion increased by 48.4, 107.1,55.4 and 12.2 mm in spring, summer, autumn and winter respectively. The annual average total cloud cover and low cloud cover had significantly positive correlation with 〉~0.1, ~〉1.0, ~〉10 and ~〉25 mm precipitation days respectively. The sunshine hours were seriously influenced by cloud cover, and when cloud cover increased by 10%, the sunshine hours decreased by 54.5 h in spring, 134.2 h in sum- mer, 154.3 h in autumn and 60.6 h in winter. The total cloud cover significantly positively correlated with relative humidity in summer and autumn, and when cloud cover increased by 10%, the relative humidity increased by 3.3% in summer and 4.1% in autumn.

关键词： cloud cover Variation features Climatic factors Correlation analysis Heze region China

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Separation of Atmospheric Circulation Patterns Governing Regional Variability of Arctic Sea Ice in Summer

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Advances in Atmospheric Sciences 2023年第12期40卷 2344-2361页

作者： Shaoyin WANG Jiping LIU Xiao CHENG Richard JGREATBATCH Zixin WEI Zhuoqi CHEN Hua LI School of Geospatial Engineering and Science Sun Yat-sen Universityand Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Zhuhai 519000China Department of Atmospheric and Environmental Sciences State University of New York at AlbanyAlbany NY 12222USA GEOMAR Helmholtz Centre for Ocean Research Kiel Kiel 24105Germany Joint International Research Laboratory of Climate and Environment Change Nanjing University of Information Science&TechnologyNanjing 210044China Faculty of Mathematics and Natural Sciences Christian Albrechts University of KielKiel 24118Germany University Corporation for Polar Research Zhuhai 519000China

In recent decades,Arctic summer sea ice extent(SIE)has shown a rapid decline overlaid with large interannual variations,both of which are influenced by geopotential height anomalies over Greenland(GL-high)and the central Arctic(CA-high).In this study,SIE along coastal Siberia(Sib-SIE)and Alaska(Ala-SIE)is found to account for about 65%and 21%of the Arctic SIE interannual variability,respectively.Variability in Ala-SIE is related to the GL-high,whereas variability in Sib-SIE is related to the CA-high.A decreased Ala-SIE is associated with decreased cloud cover and increased easterly winds along the Alaskan coast,promoting ice-albedo feedback.A decreased Sib-SIE is associated with a significant increase in water vapor and downward longwave radiation(DLR)along the Siberian coast.The years 2012 and 2020 with minimum recorded ASIE are used as examples.Compared to climatology,summer 2012 is characterized by a significantly enhanced GL-high with major sea ice loss along the Alaskan coast,while summer 2020 is characterized by an enhanced CA-high with sea ice loss focused along the Siberian coast.In 2012,the lack of cloud cover along the Alaskan coast contributed to an increase in incoming solar radiation,amplifying ice-albedo feedback there;while in 2020,the opposite occurs with an increase in cloud cover along the Alaskan coast,resulting in a slight increase in sea ice there.Along the Siberian coast,increased DLR in 2020 plays a dominant role in sea ice loss,and increased cloud cover and water vapor both contribute to the increased DLR.

关键词： Arctic sea ice Arctic circulation patterns shortwave and longwave radiation cloud cover water vapor

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Impacts of environmental factors on urban heating

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Journal of Environmental Sciences 2010年第12期22卷 1903-1909页

作者： Rizwan Ahmed Memon Dennis Y.C.Leung Department of Mechanical Engineering Mehran University of Engineering & Technology Department of Mechanical Engineering The University of Hong Kong School of Energy and Environment City University of Hong Kong

This study investigated the impact of important environmental variables （i.e., wind speed, solar radiation and cloud cover） on urban heating. Meteorological parameters for fifteen years （from 1990 to 2005）, collected at a well developed and densely populated commercial area （Tsim Sha Tsui, Hong Kong）, were analyzed in details. Urban heat island intensity （UHII）, a well known indicator of urban heating, has been determined as the spatially averaged air-temperature difference between Tsim Sha Tsui and Ta Kwu Ling （a thinly populated rural area with lush vegetation）. Results showed that the UHII and cloud cover have increased by around 9.3% and 4%, respectively, whereas the wind speed and solar radiation have decreased by around 24% and 8.5%, respectively. The month of December experienced the highest UHII （10.2℃） but the lowest wind speed （2.6 m/sec） and cloud cover （3.8 oktas）. Conversely, the month of April observed the highest increases in the UHII （over 100%） and the highest decreases in wind speed （over 40 %） over fifteen years. Notably, the increases in the UHII and reductions in the wind speed were the highest during the night-time and early morning. Conversely, the intensity of solar radiation reduced while the intensity of urban cool island （UCII） increased during solar noon-time. Results demonstrated strong negative correlation between the UHII and wind speed （coefficient of determination, R^2 = 0.8） but no negative correlation between UCII and solar radiation attenuation. A possible negative correlation between UHII and cloud cover was investigated but could not be substantiated.

关键词： urban heat island urban cool island wind speed cloud cover

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Assessing global Sentinel-2 coverage dynamics and data availability for operational Earth observation(EO)applications using the EO-Compass

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International Journal of Digital Earth 2020年第7期13卷 768-784页

作者： Martin Sudmanns Dirk Tiede Hannah Augustin Stefan Lang Department of Geoinformatics University of SalzburgSalzburgAustria

Sentinel-2 scenes are increasingly being used in operational Earth observation(EO)applications at regional,continental and global scales,in near-real time applications,and with multi-temporal approaches.On a broader scale,they are therefore one of the most important facilitators of the Digital Earth.However,the data quality and availability are not spatially and temporally homogeneous due to effects related to cloudiness,the position on the Earth or the acquisition plan.The spatiotemporal inhomogeneity of the underlying data may therefore affect any big remote sensing analysis and is important to consider.This study presents an assessment of the metadata for all accessible Sentinel-2 Level-1C scenes acquired in 2017,enabling the spatio-temporal coverage and availability to be quantified,including scene availability and cloudiness.Spatial exploratory analysis of the global,multi-temporal metadata also reveals that higher acquisition frequencies do not necessarily yield more cloud-free scenes and exposes metadata quality issues,e.***.systematically incorrect cloud cover estimation in high,nonvegetated altitudes.The continuously updated datasets and analysis results are accessible as a Web application called EO-Compass.It contributes to a better understanding and selection of Sentinel-2 scenes,and improves the planning and interpretation of remote sensing analyses.

关键词： Sentinel-2 metadata cloud cover scene coverage global analysis big Earth data digital earth

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