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Analysis of Pressure Forcings for the Vertical Turbulent Fluxes in the Convective Boundary Layer at Gray Zone Resolutions

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Journal of Meteorological Research 2023年第6期37卷 841-854页

作者： Yahua WANG Xiaoping CHENG jianfang fei Bowen ZHOU College of Meteorology and Oceanography National University of Defense TechnologyChangsha410005China Key Laboratory of Electro-Optical Countermeasures Test and Evaluation Technology Luoyang471000China Key Laboratory for Mesoscale Severe Weather Ministry of EducationSchool of Atmospheric SciencesNanjing UniversityNanjing210000China

At kilometer and sub-kilometer resolutions,known as the numerical gray zone for boundary layer turbulence,the atmospheric boundary layer turbulence becomes partially resolved and partially subgrid-scale(SGS) in a numerical model,thus requiring scale-adaptive turbulence schemes.Such schemes are often built by modifying the existing parameterizations,either the planetary boundary layer(PBL) schemes or the large-eddy simulation(LES) closures,to produce the right SGS turbulent fluxes at gray zone resolutions.However,the underlying forcings responsible for the changes in the vertical turbulent fluxes are largely ignored in these approaches.This study follows the original approach of Wyngaard(2004) and analyzes the turbulent buoyancy and momentum flux budgets,to gain a better understanding of the variations of flux forcings at gray zone resolutions.The investigation focuses on the pressure covariance term,which is one of the most dominant terms in the budget equations.By using the coarse-grained LES of a dry convective boundary layer(CBL) case as reference,two widely-used pressure covariance models are evaluated and optimized across the gray zone resolution range.The optimized linear model is further evaluated a priori against another dry CBL case with a different bulk stability,and a shallow-cumulus-topped boundary layer case.The model applies well to both cases,and notably shows good performance for the cloud layer.Based on the analysis of the flux forcings and the optimized pressure model,a scale-adaptive turbulence model for the gray zone is derived from the steady-state flux budgets.

关键词： convective boundary layer gray zone flux budget pressure covariance turbulence parameterization

Research of Super Typhoon Lekima: forecast, observation, numerical simulation and disaster survey

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Frontiers of Earth Science 2022年第1期16卷 1-4页

作者： Jie TANG jianfang fei Hui YU Shanghai Typhoon Institute CMAShanghai 200030China College of Meteorology and Oceanography National University of Defense TechnologyChangsha 410073China

Tropical cyclones(TCs)are among the most destructive natural disasters in the world,and the TCs in the North-west Pacific(NWP)are most frequent among all ocean basins.The TCs that induce disastrous weather such as destructive winds,heavy precipitation,tornadoes,lightning and storm surges sometimes cause significant economic losses and heavy casualties to human beings,which are also called high-impact TCs due to their influences on human society.Generally,TCs in the NWP generate in tropical oceans and move northwestward,which then strike the south-eastern coastal regions of Asia continent,densely populated areas with developed economy.

关键词： disaster lightning northwest

Analysis of the Winter Cloud-to-Ground Lightning Activity and Its Synoptic Background in China during 2010-20

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Advances in Atmospheric Sciences 2022年第6期39卷 985-998页

作者： Manman MA Xiaogang HUANG jianfang fei Chi ZHANG Chao LI Xiaoping CHENG College of Meteorology and Oceanography National University of Defense TechnologyChangsha 410073China Unit 94116 of PLA Hetian 848000China Jiangsu Meteorological Observatory Nanjing 210008China

Cloud-to-ground(CG)lightning data and the ECMWF ERA-Interim reanalysis dataset are analyzed to gain insight into the spatiotemporal distribution and synoptic background of winter-season CG flashes between December 2010 and February 2020 in China.We identify three Winter Lightning Frequent Areas(WLAs):the southwest side of the Yunnan-Guizhou Plateau(WLA1),the east side of the Yunnan-Guizhou Plateau(WLA2),and the Poyang Lake Plain(WLA3).The CG lightning flashes most frequently occur at local midnight and have a monthly peak in February.The CG lightning in WLA1 is mostly generated in non-frontal weather;however,the lightning in WLA2 and WLA3 mostly occurs in frontal systems.The frontal circulation situation is divided into four typical types:transversal trough after high pressure,low vortex,confrontational convergence,and asymptotic convergence.In all typical weather patterns,the lightning occurs downstream of a 500 hPa trough and is accompanied by a southwesterly low-level jet.The convective parameters of winter thunderstorms differ greatly from those of summer thunderstorms.The maximum convective available potential energy(MCAPE)and K-index(KI)are more useful metrics than convective available potential energy(CAPE)and Showalter index(SI)during winter.This study further deepens the understanding of the distribution characteristics of winter CG lightning in China,which motivates further research to improve the ability of winter thunderstorm prediction.

关键词： winter thunderstorms CG lightning spatiotemporal characteristics ADTD

Direct/indirect effects of aerosols and their separate contributions to Typhoon Lupit(2009):Eyewall versus peripheral rainbands

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Science China Earth Sciences 2021年第12期64卷 2113-2128页

作者： Zhichao LIANG Juli DING jianfang fei Xiaoping CHENG Xiaogang HUANG College of Meteorology and Oceanography National University of Defense TechnologyNanjing211101China PLA Troop 96746 Korla841000China

As a typhoon approaches the continent,the position where anthropogenic aerosols penetrate,the convection competition between the eyewall and peripheral rainbands,and the separate contributions of direct aerosol-radiation interactions(ARI)and indirect aerosol-cloud interactions(ACI),yield uncertainties in the convection intensification area and hence the typhoon intensity.Typhoon Lupit(2009)was simulated using the Weather Research and Forecasting Model with Chemistry(WRF-Chem)to investigate and isolate the direct and indirect effects of aerosols on the intensity,convection,and precipitation of the typhoon.Three simulations(CTL,CLEAN,and CTLARIOFF)were designed,representing a polluted case(CTL,considering the ingestion of anthropogenic aerosols with ARI and ACI),a clean maritime case(CLEAN,mainly with sea salt aerosols),and a polluted case without aerosol radiative forcing(CTLARIOFF,as per CTL but without ARI).The results showed that anthropogenic aerosols could penetrate into both the peripheral rainbands and the eyewall when the typhoon was approaching the Asian continent.Owing to the representation of the real aerosol scenario,the simulated typhoon intensity weakened and was closer to observed values in the CTL experiment.The ARI dominated over ACI with the opposite effects.Specifically,the ACI mainly enhanced the formation of ice-phase hydrometeors within the upper level of the eyewall with more freezing latent heat releases,leading to an invigoration of eyewall convection.These excess ice-phase particles melted after they descended into the warm layer below the 0°C level,which accelerated the accretion of cloud droplets by raindrops(Pcacr)and hence the mixed phase precipitation process in the eyewall.The dynamic feedback induced by the ACI enhanced the boundary layer inflow and the upper layer outflow,supporting the maintenance of strong eyewall convection and intensification of the typhoon.Inversely,the ARI heated the distant periphery low-level atmosphere at an altitude of 1-2 km by the absorbing polluted ae

关键词： Aerosol Tropical cyclone Eyewall Peripheral rainbands WRF-Chem

Maintenance and Sudden Change of a Strong Elevated Ducting Event Associated with High Pressure and Marine Low-Level Jet

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Journal of Meteorological Research 2020年第6期34卷 1287-1298页

作者： Zhichao LIANG Juli DING jianfang fei Xiaoping CHENG Xiaogang HUANG College of Meteorology and Oceanography National University of Defense TechnologyNanjing 211101 296746 Troops of PLA Korla 841000

Capture of a strong elevated ducting event,especially its maintenance and sudden change,is of great value to airborne radar to achieve its beyond-the-line-of-sight detection.However,the knowledge is not easily accessible over the open ocean and hence very rare.During the Air–Sea Interaction Survey(ASIS)over the western North Pacific(WNP)in May 2016,a strong elevated ducting event with a long-life period and sudden change in its evolution was observed.Measurements from the ASIS,images from the Himawari-8 satellite,reanalysis data from the ECMWF,and Weather Research and Forecasting(WRF)model,were used to analyze the maintenance and sudden change of this strong ducting event,together with the model performance on simulating it.The results showed that the maintenance of strong elevated ducts,with their tops ranging from 750 to 1050 m and average strength of approximately 38 M units,was caused by a strong dry air mass capping over the wet marine atmospheric boundary layer(MABL),together with the subsidence inversion associated with high pressure.The WRF model performs well in simulating them.However,a sudden increase in duct height with a slight decrease of strength was recorded by the subsequent GPS radiosonde,which was finally contributed to the mechanical turbulent inversion and hydrolapse associated with the marine low-level jet(MLLJ).The height of the maximum horizontal wind speed(Umh)of the MLLJ corresponds well with the bottom of the trapping layer.However,these jet-relevant ducts are generally weak and it is difficult to accurately simulate them by using the mesoscale numerical model,since the wind-shear produced eddies are too small to be properly parameterized.

关键词： atmospheric ducts elevated ducts marine atmospheric boundary layer(MABL) low-level jet numerical simulation

Estimating the Correlated Observation-Error Characteristics of the Chinese FengYun Microwave Temperature Sounder and Microwave Humidity Sounder

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Advances in Atmospheric Sciences 2018年第11期35卷 1428-1441页

作者： Ting WANG jianfang fei Xiaoping CHENG Xiaogang HUANG Jian ZHONG College of Meteorology and Oceanography National University of Defense TechnologyNanjing 211101China China Satellite Maritime Tracking and Control Department Jiangyin 214431China

In operational data assimilation systems, observation-error covariance matrices are commonly assumed to be diagonal.However, inter-channel and spatial observation-error correlations are inevitable for satellite radiances. The observation errors of the Microwave Temperature Sounder(MWTS) and Microwave Humidity Sounder(MWHS) onboard the FengYun-3A(FY-3A) and FY-3B satellites are empirically assigned and considered to be uncorrelated when they are assimilated into the WRF model's Community Variational Data Assimilation System(WRFDA). To assimilate MWTS and MWHS measurements optimally, a good characterization of their observation errors is necessary. In this study, background and analysis residuals were used to diagnose the correlated observation-error characteristics of the MWTS and MWHS. It was found that the error standard deviations of the MWTS and MWHS were less than the values used in the WRFDA. MWTS had small inter-channel errors, while MWHS had significant inter-channel errors. The horizontal correlation length scales of MWTS and MWHS were about 120 and 60 km, respectively. A comparison between the diagnosis for instruments onboard the two satellites showed that the observation-error characteristics of the MWTS or MWHS were different when they were onboard different satellites. In addition, it was found that the error statistics were dependent on latitude and scan positions.The forecast experiments showed that using a modified thinning scheme based on diagnosed statistics can improve forecast accuracy.

关键词： data assimilation correlated observation errors MWTS(Microwave Temperature Sounder) MWHS(Microwave Humidity Sounder)

Evaluation of the Impact of Observations on Blended Sea Surface Winds in a Two-Dimensional Variational Scheme Using Degrees of Freedom

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Journal of Meteorological Research 2017年第6期31卷 1123-1132页

作者： Ting WANG Jie XIANG jianfang fei Yi WANG Chunxia LIU Yuanxiang LI Institute of Meteorology and Oceanography National University of Defense TechnologyNanjing 211101 Key Laboratory of Mesoscale Severe Weather of Ministry of Education Nanjing UniversityNanjing 210093 Guangdong Institute of Tropical and Marine Meteorology of China Meteorological Administration Guangzhou 510080 School of Aeronautics andAstronautics Shanghai Jiao Tong UniversityShanghai 200240

This paper presents an evaluation of the observational impacts on blended sea surface winds from a two- dimensional variational data assimilation （2D-Var） scheme. We begin by briefly introducing the analysis sensitivity with respect to observations in variational data assimilation systems and its relationship with the degrees of freedom for signal （DFS）, and then the DFS concept is applied to the 2D-Var sea surface wind blending scheme. Two meth- ods, a priori and a posteriori, are used to estimate the DFS of the zonal （u） and meridional （v） components of winds in the 2D-Var blending scheme. The a posteriori method can obtain almost the same results as the a priori method. Because only by-products of the blending scheme are used for the a posteriori method, the computation time is re- duced significantly. The magnitude of the DFS is critically related to the observational and background error statistics. Changing the observational and background error variances can affect the DFS value. Because the observation error variances are assumed to be uniform, the observational influence at each observational location is related to the background error variance, and the observations located at the place where there are larger background error variances have larger influences. The average observational influence of u and v with respect to the analysis is about 40%, implying that the background influence with respect to the analysis is about 60%.

关键词： sea surface wind blending sensitivity observational influence degrees of freedom for signal

Asymmetric Distribution of Convection in Tropical Cyclones over the Western North Pacific Ocean

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Advances in Atmospheric Sciences 2016年第11期33卷 1306-1321页

作者： Lu YANG jianfang fei Xiaogang HUANG Xiaoping CHENG Xiangrong YANG Juli DING Wenli SHI Institute of Meteorology and Oceanography PLA University of Science and Technology

Forecasts of the intensity and quantitative precipitation of tropical cyclones（TCs） are generally inaccurate, because the strength and structure of a TC show a complicated spatiotemporal pattern and are affected by various factors. Among these, asymmetric convection plays an important role. This study investigates the asymmetric distribution of convection in TCs over the western North Pacific during the period 2005–2012, based on data obtained from the Feng Yun 2（FY2）geostationary satellite. The asymmetric distributions of the incidence, intensity and morphology of convections are analyzed.Results show that the PDFs of the convection occurrence curve to the azimuth are sinusoidal. The rear-left quadrant relative to TC motion shows the highest occurrence rate of convection, while the front-right quadrant has the lowest. In terms of intensity, weak convections are favored in the front-left of a TC at large distances, whereas strong convections are more likely to appear to the rear-right of a TC within a 300 km range. More than 70% of all MCSs examined here are elongated systems, and meso-β enlongated convective systems（MβECSs） are the most dominant type observed in the outer region of a TC. Smaller MCSs tend to be more concentrated near the center of a TC. While semi-circular MCSs [MβCCSs, MCCs（mesoscale convective complexes）] show a high incidence rate to the rear of a TC, elongated MCSs [MβECSs, PECSs（persistent elongated convective systems）] are more likely to appear in the rear-right quadrant of a TC within a range of 400 km.

关键词： convection Tropical convective asymmetric tropical mesoscale elongated typhoon likely storm

Roles of Multisourced Fluids in the Formation of Sandstone-Hosted Uranium Deposits in the SW Songliao Basin, NE China

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Journal of Earth Science 2023年第1期34卷 54-69页

作者： Zhibing Feng Fengjun Nie Li Jiang fei Xia jianfang Cai Bocheng Zhang Yayun Lu Liangliang Zhang State Key Laboratory of Nuclear Resources and Environment East China University of TechnologyNanchang330013China Jiangxi Engineering Laboratory on Radioactive Geoscience and Big Data Technology East China University of TechnologyNanchang330013China Radioactive Geology and Exploration Technology Laboratory East China University of TechnologyNanchang330013China No.243 Geological Party China National Nuclear CorporationChifeng024000China Airborne Survey and Remote Sensing Center of Nuclear Industry China National Nuclear CorporationShijiazhuang050002China

The sandstone-hosted uranium deposits in the SW Songliao Basin differ from typical sandstone-hosted uranium deposits in terms of the geological features of the ore-deposits,including the geometry of the orebodies,mineral assemblage and petrography.Detailed drill core and microscopic observations,scanning electron microscopy(SEM),electron microprobe analysis(EMPA),heavy mineral concentrates,and fluid inclusion studies of the Upper Cretaceous Yaojia Formation,i.e.,the uranium-bearing layer,were integrated to investigate the roles of hydrothermal fluids in the formation of these uranium deposits.We found that the kaolinite alteration is developed in the mineralized zones,but it is less common in the peripheral areas.The fluid inclusions are hydrothermal fluids with a medium-low temperature(67 to 179 ℃) and a high salinity(5.9 wt.% to 20.1 wt.%).According to the analyses,three kinds of hydrothermal fluids,i.e.,the acid fluid,the groundwater heated by the mafic magma,and the alkaline fluid rich in Ca^(2+) and CO_(3)^(2-),were identified.The fluids might have low U content,but they have participated in the formation of the uranium deposits successively.Kaolinite formed by the acid-hydrothermal fluid absorbed large amounts of uranium.Subsequently,the thermal energy from the hydrothermal fluids changed the intrastratal redox environment and increased the solubility of the uranium minerals in the fluid.The alkaline-hydrothermal fluid rich in Ca^(2+) and C0_(3)^(2-) facilitated the formation of stable Ca-U(Ⅵ)-CO_(3) complex,which led to the enrichment of soluble uranium in solution,and final precipitation as pitchblende,brannerite and Ti-bearing uranium minerals in the uranium ores.

关键词： sandstone-hosted uranium deposit hydrothermal fluid uranium mineralization Songliao Basin kaolinite carbonate minerals