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Satellite Observations of Reflectivity Maxima above the Freezing Level Induced by Terrain

Advances in Atmospheric Sciences 2021年第4期38卷 627-640页

作者： Aoqi ZHANG Weibiao LI Shumin CHEN Yilun CHEN yunfei fu Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies School of Atmospheric SciencesSun Yat-sen UniversityGuangzhou 510275China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519082China School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China

Previous studies have recognized reflectivity maxima above the freezing level(RMAF) within stratiform precipitation over mountain slopes, however, quantitative studies are limited due to the lack of adequate identification criteria. Here, we establish an identification method for RMAF precipitation and apply it to the Tropical Rainfall Measuring Mission(TRMM) Precipitation Radar(PR) observations. Using the TRMM 2A25 product from 1998 to 2013, we show that the RMAF structure in reflectivity profiles can be effectively identified. RMAF exists not only in stratiform precipitation but also in convective precipitation. RMAF frequency is positively correlated with elevation, which is thought to be caused by enhanced updrafts in the middle layers of stratiform precipitation, or in the low to middle layers of convective precipitation over mountains. The average RMAF heights in stratiform and convective precipitation were 1.35 and 2.01 km above the freezing level, respectively, which is lower than previous results. In addition, our results indicate that the RMAF structure increased the echo top height and enhanced precipitation processes above the RMAF height, but it suppressed the downward propagation of ice particles and the near-surface rain rate. future studies of orographic precipitation should take into account the impact of the RMAF structure and its relevant dynamic triggers.

关键词： orographic precipitation reflectivity maxima above the freezing level precipitation structure TRMM PR

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Analysis of the Relationship between the Cloud Water Path and Precipitation Intensity of Mature Typhoons in the Northwest Pacific Ocean

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Advances in Atmospheric Sciences 2020年第4期37卷 359-376页

作者： Shuang LUO yunfei fu Shengnan ZHOU Xiaofeng WANG Dongyong WANG School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China Shanghai Ecological Forecasting and Remote Sensing Center Shanghai 200030China Anhui Meteorological Observatory Hefei 230026China

The relationship between precipitation intensity and cloud water in typhoon systems remains *** study combined time-and space-synchronized precipitation and spectral data obtained by the Precipitation Radar(PR)as well as the Visible and Infrared Scanner(VIRS)onboard the TRMM satellite,to overcome the limitations of precipitation properties and cloud parameters not being synchronized in previous studies.A merged dataset of near-surface rain rate(RR)and corresponding cloud water path(CWP)was established and used to analyze the potential correlation between cloud microphysical properties and precipitation,to deepen our understanding of the evolution of cloud to *** addition,25 collocated satellite overpasses of mature typhoon cases in the Northwest Pacific Ocean from 1998 to 2012 were obtained,and the relationships between the CWP and RR of 144515 pixels were analyzed in *** results show that the CWP and RR of mature typhoon systems with different precipitation types,precipitation cloud phases,and vertical depths of precipitation can be fitted by a notable sigmoid function,which may be useful for estimating CWP and parameterizing precipitation in ***,the relationship was applied and tested with an independent sample to show that RR is a significant indicator of CWP.

关键词： cloud water path convective precipitation stratiform precipitation TRMM tropical cyclone

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Morphological Characteristics of Precipitation Areas over the Tibetan Plateau Measured by TRMM PR

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Advances in Atmospheric Sciences 2021年第4期38卷 677-689页

作者： Yilun CHEN Aoqi ZHANG yunfei fu Shumin CHEN Weibiao LI Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies School of Atmospheric SciencesSun Yat-sen UniversityZhuhai 519000China School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519000China

The multidimensional morphological characteristics(including scale, horizontal shape and 3 D morphology) of precipitation areas over the Tibetan Plateau in summer were studied using 15 years(1998–2012) of observational data from the precipitation radar onboard the Tropical Rainfall Measuring Mission satellite. As the scale of the precipitation area increased from 20 to 150 km, the near-surface rain rate(RRav) of the precipitation area increased by up to 78%(from ~1.12 to ~2 mm h~(-1)). Linear precipitation areas had the lowest median RRav(~1 mm h~(-1) over the eastern Tibetan Plateau),whereas square-shaped precipitation areas had the highest median RRav(~1.58 mm h~(-1) over the eastern Tibetan Plateau).The 3D morphology was defined as the ratio of the average vertical scale to the average horizontal scale, where a large value corresponds to thin and tall, and a small value corresponds to plump and short. Thin-and-tall precipitation areas and plump-and-short precipitation areas had a greater median RRav, whereas the precipitation areas with a moderate 3D morphology had the lowest median RRav. The vertical structure of the precipitation-area reflectivity was sensitive to both size and 3D morphology, but was not sensitive to the horizontal shape. The relationship between RRav and the morphological characteristics was most significant over the southern slopes of the Tanggula Mountains and the Tibetan Plateau east of 100°E. The morphological characteristics of precipitation areas are therefore closely related to the intensity of precipitation and could potentially be used to forecast precipitation and verify numerical models.

关键词： precipitation areas morphological characteristics Tibetan Plateau TRMM PR

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Optical Properties of Cirrus Transition Zones over China Detected by CALIOP

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Journal of Meteorological Research 2017年第3期31卷 576-585页

作者： Hongke CAI yunfei fu Quanliang CHEN Xiao FENG Xin TIE Ranting TAO Kepiao XU School of Atmospheric Science Chengdu University of Information Technology/Plateau Atmospheric and Environment Laboratory of Sichuan Province School of Earth and Space Sciences University of Science and Technology of China

A transition zone near cirrus lateral boundaries can be detected by CALIOP （cloud-aerosol lidar with orthogonal polarization）. In the present study, for such transition zones over China, a number of optical properties, such as the backscatter coefficient and depolarization ratio, showed transitional characteristics between cirrus and clear sky. The stepped horizontal profile showed sharp changes in particle number and morphology between cirrus clouds and clear sky. The color ratio, however, was unable to show cirrus transition features because of the low signal-to-noise ratio. Typical ice particles presented a color ratio of 0.55-1.25 and a depolarization ratio of greater than 0.12, which were significantly higher than those of clear sky. Therefore, optical properties in transition took the form of stepwise hori- zontal profiles. The proportion of typical-featured particles also demonstrated a stepped horizontal profile similar to the optical characteristics, but the relationship between the proportion and the optical characteristics was not uniform in the cirrus clouds, transition zone, and clear sky. Therefore, the optical changes in the transition zone were caused by not only the change in particle concentration, but also the change in the particles themselves. The probability dens- ity distribution of the transition-zone widths showed a positive skewness distribution, and transition zones with widths of 3-5 km occurred most frequently. Overall, transition-zone width decreased with increasing temperature and increased with increasing vertical and horizontal wind speeds. This trend demonstrated independence with the direc- tion of the vertical and horizontal winds. These observations implied that the transitional features were caused by ma- terial exchange, such as entrainment and turbulent transport, near the cirrus lateral boundaries, and by the phase trans- formation of particles, such as sublimation.

关键词： cirrus transition zone lidar temperature wind speed

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Grid-cell Aerosol Direct Shortwave Radiative Forcing Calculated Using the SBDART Model with MODIS and AERONET Observations：An Application in Winter and Summer in Eastern China

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Advances in Atmospheric Sciences 2017年第8期34卷 952-964页

作者： yunfei fu Jiachen ZHU Yuanjian YANG Renmin YUAN Guosheng LIU Tao XIAN Peng LIU School of Earth and Space Sciences University of Science and Technology of China Hefei 230026 China Key Laboratory of Atmospheric Sciences and Satellite Remote Sensing of Anhui Province Anhui Institute of Meteorological Sciences Hefei 230031 China Anhui Academy for Environmental Science Research Hefei 230071 China Department of Earth Ocean and Atmospheric Science Florida State University Tallahassee Florida FL 32306-4520 USA

Taking winter and summer in eastern China as an example application, a grid-cell method of aerosol direct radiative forcing（ADRF） calculation is examined using the Santa Barbara DISORT Atmospheric Radiative Transfer（SBDART） model with inputs from MODIS and AERONET observations and reanalysis data. Results show that there are significant seasonal and regional differences in climatological mean aerosol optical parameters and ADRF. Higher aerosol optical depth（AOD）occurs in summer and two prominent high aerosol loading centers are observed. Higher single scattering albedo（SSA） in summer is likely associated with the weak absorbing secondary aerosols. SSA is higher in North China during summer but higher in South China during winter. Aerosols induce negative forcing at the top of the atmosphere（TOA） and surface during both winter and summer, which may be responsible for the decrease in temperature and the increase in relative *** of ADRF at the surface are four times stronger than those at the TOA. Both AOD and ADRF present strong interannual variations; however, their amplitudes are larger in summer. Moreover, patterns and trends of ADRF do not always correspond well to those of AOD. Differences in the spatial distributions of ADRF between strong and weak monsoon years are captured effectively. Generally, the present results justify that to calculate grid-cell ADRF at a large scale using the SBDART model with observational aerosol optical properties and reanalysis data is an effective approach.

关键词： aerosol direct radiative forcing AERONET MODIS SBDART model

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Untangling the contributions of meteorological conditions and human mobility to tropospheric NO2 in Chinese mainland during the COVID-19 pandemic in early 2020

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National Science Review 2021年第11期8卷 121-132页

作者： Yuxiang Zhang Haixu Bo Zhe Jiang Yu Wang yunfei fu Bingwei Cao Xuewen Wang Jiaqi Chen Rui Li School of Earth and Space Sciences University of Science and Technology of China Comparative Planetary Excellence Innovation Center Frontiers Science Center for Planetary Exploration and Emerging Technologies Chinese Academy of Sciences State Key Laboratory of Fire Science University of Science and Technology of China Jiangxi Ecological Environment Monitoring Center Green Earth Science and Education Service

In early 2020,unprecedented lockdowns and travel bans were implemented in Chinese mainland to fight COVID-19,which led to a large reduction in anthropogenic *** provided a unique opportunity to isolate the effects from emission and meteorology on tropospheric nitrogen dioxide(NO2).Comparing the atmospheric NO2in 2020 with that in 2017,we found the changes of emission have led to a49.3±23.5% reduction,which was～12% more than satellite-observed reduction of 37.8±16.3%.The discrepancy was mainly a result of changes of meteorology,which have contributed to an 8.1±14.2%increase of *** also revealed that the emission-induced reduction of NO2has significantly negative correlations to human mobility,particularly that inside the *** intra-city migration index derived from Baidu Location-Based-Service can explain 40.4%±17.7% variance of the emission-induced reduction of NO2in 29 megacities,each of which has a population of over 8 million in Chinese mainland.

关键词： atmospheric nitrogen dioxide anthropogenic emissions meteorology conditions human mobility COVID-19 quarantine

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Estimations of Land Surface Characteristic Parameters and Turbulent Heat Fluxes over the Tibetan Plateau Based on FY-4A/AGRI Data

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Advances in Atmospheric Sciences 2021年第8期38卷 1299-1314页

作者： Nan GE Lei ZHONG Yaoming MA yunfei fu Mijun ZOU Meilin CHENG Xian WANG Ziyu HUANG School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in Comparative Planetology Hefei 230026China Jiangsu Collaborative Innovation Center for Climate Change Nanjing 210023China Key Laboratory of Tibetan Environment Changes and Land Surface Processes Institute of Tibetan Plateau ResearchChinese Academy of ScienceBeijing 100101China CAS Center for Excellence in Tibetan Plateau Earth Sciences Beijing 100101China College of Earth and Planetary Sciences University of Chinese Academy of ScienceBeijing 100049China

Accurate estimates of land surface characteristic parameters and turbulent heat fluxes play an important role in the understanding of land-atmosphere interaction. In this study, Fengyun-4A (FY-4A) Advanced Geostationary Radiation Imager (AGRI) satellite data and the China Land Data Assimilation System (CLDAS) meteorological forcing dataset CLDAS-V2.0 were applied for the retrieval of broadband albedo, land surface temperature (LST), radiation flux components, and turbulent heat fluxes over the Tibetan Plateau (TP). The FY-4A/AGRI and CLDAS-V2.0 data from 12 March 2018 to 30 April 2018 were first used to estimate the hourly turbulent heat fluxes over the TP. The time series data of in-situ measurements from the Tibetan Observation and Research Platform were divided into two halves-one for developing retrieval algorithms for broadband albedo and LST based on FY-4A, and the other for the cross validation. Results show the root-mean-square errors (RMSEs) of the FY-4A retrieved broadband albedo and LST were 0.0309 and 3.85 K, respectively, which verifies the applicability of the retrieval method. The RMSEs of the downwelling/upwelling shortwave radiation flux and downwelling/upwelling longwave radiation flux were 138.87/32.78 W m^(−2) and 51.55/17.92 W m^(−2), respectively, and the RMSEs of net radiation flux, sensible heat flux, and latent heat flux were 58.88 W m^(−2), 82.56 W m^(−2) and 72.46 W m^(−2), respectively. The spatial distributions and diurnal variations of LST and turbulent heat fluxes were further analyzed in detail.

关键词： FY-4A/AGRI land surface characteristic parameters turbulent heat fluxes Surface Energy Balance System model Tibetan Plateau

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Aerosol properties over an urban site in central East China derived from ground sun-photometer measurements

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Science China Earth Sciences 2017年第2期60卷 297-314页

作者： LIU Qi DING WeiDong XIE Lei ZHANG JinQiang ZHU Jun XIA XiangAo LIU DongYang YUAN RenMin fu yunfei School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China Anhui Meteorological Observatory Hefei 230001China Key Laboratory of Middle Atmosphere and Global Environment Observation Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science&TechnologyNanjing 210044China

Sun-photometer measurements at Hefei,an urban site located in central East China,were examined to investigate the variations of aerosol loading and optical *** is found that aerosol optical thickness(AOT)keeps higher in winter/spring and gets relatively lower in summer/*** large AOT in winter is caused by anthropogenic sulfate/nitrate aerosols,while in spring dust particles elevate the background aerosol loading and the excessive fine-mode particles eventually lead to severe *** is a dramatic decline of AOT during summer,with monthly averaged AOT reaching the maximum in June and soon the minimum in ***,aerosol size decreases consistently and single scattering albedo(SSA)reaches its minimum in *** summertime large-sized particles play a key role to change the air from clean to mild-pollution situation,while the presence of massive small-sized particles makes the air being even more *** complicated summer patterns are possibly related to the three key processes that are active in the high temperature/humidity environment concentrating on sulfate/nitrate aerosols,i.e.,gas-to-particle transformation,hygroscopic growth,and wet *** of season,the increase of SSA with increasing AOT occurs across the visible and near-infrared bands,suggesting the dominant negative/cooling effect with the elevated aerosol *** SSA spectra under varying AOT monotonically decrease with *** relatively large slope arises in summer,reinforcing the dominance of sulfate/nitrate aerosols that induce severe pollution in summer season around this city.

关键词：气溶胶光学厚度太阳光度计华东地区光学特性城市网站测量颗粒物污染

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fundamental Characteristics of Tropical Rain Cell Structures as Measured by TRMM PR

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Journal of Meteorological Research 2020年第6期34卷 1129-1150页

作者： yunfei fu Yilun CHEN Xiangdong ZHANG Yu WANG Rui LI Qi LIU Lei ZHONG Qiong ZHANG Aoqi ZHANG School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China International Arctic Research Center and Department of Atmospheric Sciences University of Alaska FairbanksFairbanksAK 99775USA Department of Physical Geography and Bolin Center for Climate Research Stockholm UniversityStockholm 10691Sweden

Rain cells are the most elementary unit of precipitation system in *** this study,fundamental geometric and physical characteristics of rain cells over tropical land and ocean areas are investigated by using 15-yr measurements of the Tropical Rainfall Measuring Mission(TRMM)Precipitation Radar(PR).The rain cells are identified with a minimum bounding rectangle(MBR)*** results indicate that about 50%of rain cells occur at length of about 20 km and width of 15 *** proportion of rain cells with length>200 km and width>100 km is less than1%.There is a a log-linear relationship between the mean length and width of rain ***,for the same horizontal geometric parameters,rain cells tend to be square horizontally and lanky vertically over land,while vertically squatty over *** rainfall intensity of rain cells varies from 0.4 to 10 mm h-1 over land to 0.4–8 mm h-1 over *** results indicate that the occurrence frequency of rain cells decreases as the areal fraction of convective precipitation in rain cells increases,while such frequency remains almost invariant when the areal fraction of stratiform precipitation varies from 10%to 80%.The relationship between physical and geometric parameters of rain cells shows that the mean rain rate of rain cells is more frequently associated with the increase of their area,with the increasing rate over land greater than that over *** results also illustrate that heavy convective rain rate prefers to occur in larger rain cells over land while heavy stratiform rain rate tends to appear in larger rain cells over *** the same size of rain cells,the areal fraction and the contribution of convective precipitation are about10%–15%higher over land than over ocean.

关键词： rain cell occurrence frequency geometric parameters physical parameters Tropical Rainfall Measuring Mission(TRMM)Precipitation Radar(PR)

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Aerosol characteristics and impacts on weather and climate over the Tibetan Plateau

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National Science Review 2020年第3期7卷 492-495页

作者： Chuanfeng Zhao Yikun Yang Hao Fan Jianping Huang yunfei fu Xiaoye Zhang Shichang Kang Zhiyuan Cong Husi Letu Massimo Menenti State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science Beijing Normal University Collaborative Innovation Center for Western Ecological Safety College of Atmospheric Sciences Lanzhou University School of Earth and Space Sciences University of Science and Technology of China Institute of Atmospheric Composition Chinese Academy of Meteorological Sciences State Key Laboratory of Cryospheric Sciences Northwest Institute of Eco-Environment and Resources Chinese Academy of Sciences Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences

With the most massive snow and ice globally between 60°S and 60°N, the Tibetan Plateau (TP), also called the third pole of the world, plays significant roles in the weather, climate and lives in South Asia and East Asia and even the world [1–3].Investigating the variation of weather and the climate system over the TP has long been carried out, which is signif-

关键词： Aerosol characteristics and impacts on weather and climate over the Tibetan Plateau

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