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An atmospheric Dry Intrusion Parameter and Its Application

Acta meteorologica Sinica 2010年第4期24卷 492-500页

作者：王东海杨帅 state key laboratory of severe weather(lasw) Chinese Academy of Meteorological Sciences laboratory of Cloud-Precipitation Physics and severe Storms(LACS) Institute of Atmospheric PhysicsChinese Academy of Sciences

Dry intrusion plays an important role in the explosive development of cyclones and the evolution of cold fronts. Characteristics of dry intrusion during a rainfall event that occurred in northern China are analyzed in detail in this paper. The IM （ingredients-based methodology） developed by Doswell et al. in 1996 and Wetzel and Martin in 2001 is utilized. All the physical representations of dry intrusion defined in the past studies, such as low relative humidity, cold advection, and high potential vorticity （on either isobaric or isentropic surfaces）, are combined into a simple and convenient physical parameter to characterize dry intrusion. This is a new attempt to extend the IM that was primarily applied to research on heavy rainfall to the study of dry intrusion. The new dry intrusion parameter is used to analyze the isentropic evolution of dry intrusion during the rainfall event. The results show that this parameter can better quantify the intensity of dry intrusion and diagnose its evolution shown in satellite infrared and water vapor imageries. It is found that dry intrusion maintains during the rainfall period. The intensity of precipitation increases with the increasing dry intrusion, which has pushed the rainy region southeastward. From the results on the isentropic surface and the corresponding isobaric surface, it is inferred that the analyses of dry intrusion on both surfaces are consistent with each other. The isentropic analysis of dry intrusion reveals that cold and dry air at the upper level overruns that in the lower troposphere where moist and warm air is located. Thus, potential instability is built up in the vertical direction, which favors the occurrence of precipitation. In practice, we may identify dry intrusion regions by tracking strong signals of the dry intrusion parameter, and further identify the instability near the dry intrusion regions. This will aid in improving the accuracy of precipitation forecast.

关键词： dry intrusion parameter isentropic analysis

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The Dipole Mode of the Summer Rainfall over East China during 1958–2001

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Advances in atmospheric Sciences 2009年第4期26卷 727-735页

作者：韩晋平张人禾 state key laboratory of severe weather(lasw) Chinese Academy of Meteorological Sciences Nansen-Zhu International Research Centre Institute of Atmospheric Physics Chinese Academy of Sciences

By examining the second leading mode （EOF2） of the summer rainfall in China during 1958 2001 and associated circulations, the authors found that this prominent mode was a dipole pattern with rainfall decreasing to the north of the Yangtze River and increasing to the south. This reverse relationship of the rainfalls to the north and to the south of the Yangtze River was related with the meridional circulations within East Asia and the neighboring region, excited by SST in the South China Sea-northwestern Pacific. When the SST was warmer, the geopotential heights at 500 hPa were positive in the low and high latitudes and negative in the middle latitudes. The anticyclone in the low latitudes favored the subtropical high over the northwestern Pacific （SHNP） shifting southwestward, leading to additional moisture transport over southern China. The anomalous atmospheric circulations along the East Asian coast tends to enhance upward movement over the region. Subsequently, rainfall in southern China is enhanced.

关键词： second leading mode rainfall dipole pattern sea surface temperature

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A Comparison Study of the Methods of Conditional Nonlinear Optimal Perturbations and Singular Vectors in Ensemble Prediction

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Advances in atmospheric Sciences 2009年第3期26卷 465-470页

作者：姜智娜穆穆 state key laboratory of severe weather (lasw) Chinese Academy of Meteorological SciencesBeijing 100081 state key laboratory of Numerical Modeling for atmospheric Sciences and Geophysical Fluid Dynamics (LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029

The authors apply the technique of conditional nonlinear optimal perturbations （CNOPs） as a means of providing initial perturbations for ensemble forecasting by using a barotropic quasi-geostrophic （QG） model in a perfect-model scenario. Ensemble forecasts for the medium range （14 days） are made from the initial states perturbed by CNOPs and singular vectors （SVs）. 13 different cases have been chosen when analysis error is a kind of fast growing error. Our experiments show that the introduction of CNOP provides better forecast skill than the SV method. Moreover, the spread-skill relationship reveals that the ensemble samples in which the first SV is replaced by CNOP appear superior to those obtained by SVs from day 6 to day 14. Rank diagrams are adopted to compare the new method with the SV approach. The results illustrate that the introduction of CNOP has higher reliability for medium-range ensemble forecasts.

关键词： ensemble prediction medium-range forecasts forecast skill spread Talagrand diagram

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Another look at the moist baroclinic Ertel–Rossby invariant with mass forcing

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Chinese Physics B 2018年第2期27卷 655-663页

作者：杨帅高守亭陈斌 laboratory of Cloud-Precipitation Physics and severe Storms (LACS) Institute of Atmospheric PhysicsChinese Academy of Sciences state key laboratory of severe weather Chinese Academy of Meteorological Sciences

Due to the importance of the mass forcing induced by precipitation and condensation in moist processes, the La- grangian continuity equation without a source/sink term utilized to prove the Ertel-Rossby invariant （ERI） and its con- servation property is re-derived considering the mass forcing. By introducing moist enthalpy and moisture entropy, the baroclinic ERI could be adapted to moist flow. After another look at the moist ERI, it is deployed as the dot product be- tween the generalized velocity and the generalized vorticity in moist flow, which constitutes a kind of generalized helicity. Thus, the baroclinic ERI is further extended to the moist case. Moreover, the derived moist ERI forumla remains formally consistent with the dry version, no matter whether mass forcing is present. By using the Weber transformation and the Lagrangian continuity equation with a source/sink effect, the conservation property of the baroclinic ERI in moist flow is revisited. The presence or absence of mass forcing in the Lagrangian continuity equation determines whether or not the baroclinic ERI in moist flow is materially conserved. In other words, it would be qualified as a quasi-invariant but only being dependent on the circumstances. By another look at the moist baroclinic ERI, it is surely a neat formalism with a simple physical explanation, and the usefulness of its anomaly in diagnosing atmospheric flow is demonstrated by case study.

关键词： quasi-Ertel-Rossby invariant generalized helicity mass forcing adapting

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Image of local energy anomaly during a heavy rainfall event

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Chinese Physics B 2017年第11期26卷 565-573页

作者：杨帅左群杰高守亭 laboratory of Cloud-Precipitation Physics and severe Storms (LACS) Institute of Atmospheric PhysicsChinese Academy of Sciences state key laboratory of severe weather Chinese Academy of Meteorological Sciences

A clear and interesting image of local total energy anomaly(EA) is depicted for a heavy rainfall event in this *** the convection development, it exhibits a positive local EA, implying local total energy(TE) experiences heaping up to prepare for the future system development. As the convection grows, it transforms into an opposite spatial modality with negative EA dominant, which means that the local TE is consumed to feed the convection growth in the middle and lower levels. The local total EA has consistent variation regular in intensity with severe weather system evolution. By utilizing the local TE budget equation in variable density fluid, the flux divergence of energy and its components are investigated, which could account for the local TE variation better. To relax the restriction and complexity introduced by identifying sporadic and alternative positive/negative signals of EA, the method taking the absolute-value operator on energy flux divergence is used to further simplify analyses. The derived characteristic signal of absolute EA is clearer and cleaner than ***, the EA could be illustrated based on the active degree of energy supply/consumption in a generalized sense whatever positive or negative anomaly should be it, which could be used easily to identify and even predict the system development for operational application. Note that, although two sets of methodologies are used to define EA herein, they play absolutely different roles in nature throughout the whole context. For example, the taking-perturbation method provides a diagnostic tool to portray a preliminary sketch and to give sufficient necessity of this research, while tendency equation of local TE illuminates more predictive sense and accounts for future local EA related to following system evolution. Therefore, the latter could be a more effective tool to routine usage.

关键词： local energy anomaly energy budget equation heavy rainfall

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The Impacts of Optical Properties on Radiative Forcing Due to Dust Aerosol

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Advances in atmospheric Sciences 2006年第3期23卷 431-441页

作者：王宏石广玉李书严李伟王标黄彦彬 state key laboratory of severe weather/Center for Numerical Prediction Research state key laboratory of atmospheric and Quaternary Geology Hainan Meteorology and Ecology institute

There are large uncertainties in the quantitative assessment of radiative effects due to atmospheric dust aerosol. The optical properties contribute much to those uncertainties. The authors perform several sensitivity experiments to estimate the impacts of optical characteristics on regional radiative forcing in this paper. The experiments involve in refractive indices, single scattering aibedo, asymmetry factor and optical depth. An updated dataset of refractive indices representing East Asian dust and the one recommended by the World Meteorology Organization （WMO） are contrastively analyzed and used. A radiative transfer code for solar and thermal infrared radiation with detailed aerosol parameterization is employed. The strongest emphasis is on the refractive indices since other optical parameters strongly depend on it, and the authors found a strong sensitivity of radiative forcing on refractive indices. Studies show stronger scattering, weaker absorption and forward scattering of the East Asian dust particles at solar wavelengths, which leads to higher negative forcing, lower positive forcing and bigger net forcing at the top of the atmosphere （TOA） than that of the WMO dust model. It is also found that the TOA forcings resulting from these two dust models have opposite signs in certain regions, which implies the importance of accurate measurements of optical properties in the quantitative estimation of radiative forcing.

关键词： optical properties dust aerosol radiative forcing

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Spatial and temporal distribution of the cloud optical depth over China based on MODIS satellite data during 2003–2016

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Journal of Environmental Sciences 2019年第6期31卷 66-81页

作者： Xiaopan Li Huizheng Che Hong Wang Xiang'ao Xia Quanliang Chen Ke Gui Hujia Zhao Linchang An Yu Zheng Tianze Sun Zhizhong Sheng Chao Liu Xiaoye Zhang Plateau atmospheric and Environment laboratory of Sichuan Province College of Atmospheric Science Chengdu University of Information Technology state key laboratory of severe weather lasw and institute of atmospheric composition Chinese Academy of Meteorological SciencesCMA laboratory for Middle Atmosphere and Global Environment Observation LAGEO Institute of Atmospheric Physics Chinese Academy of Sciences School of Geoscience University of Chinese Academy of Science School of Surveying and Land Information Engineering Henan Polytechnic University

The cloud optical depth(COD) is one of the important parameters used to characterize atmospheric clouds. We analyzed the seasonal variations in the COD over East Asia in 2011 using cloud mode data from the AERONET(Aerosol Robotic Network) ground-based observational network. The applicability of the MODIS(Moderate Resolution Imaging Spectroradiometer) COD product was verified and compared with the AERONET cloud mode dataset. There was a good correlation between the AERONET and the MODIS. The spatial and temporal distribution and trends in the COD over China were then analyzed using MODIS satellite data from 2003 to 2016. The seasonal changes in the AERONET data and the time sequence variation of the satellite data suggest that the seasonal variations in the COD are significant. The result shows that the COD first decreases and then increases with the season in northern China, and reaches the maximum in summer and minimum in ***, the spatial distribution change is just the opposite in southern China. The spatial variation trend shows the COD in China decreases first with time and gradually increases after 2014. And the trend of COD in the western and central China is consistent with that in China. While the trend of COD shows a continuously increasing over time in northeast China and the Pearl River Delta.

关键词： Sun photometer MODIS COD Verification

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The Impact of Deformation on Vortex Development in a Baroclinic Moist Atmosphere

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Advances in atmospheric Sciences 2016年第2期33卷 233-246页

作者： Na LI Lingkun RAN Shouting GAO key laboratory of Cloud-Precipitation Physics and severe Storms Institute of Atmospheric PhysicsChinese Academy of Sciences state key laboratory of severe weather Chinese Academy of Meteorological Sciences

A mathematical relation between deformation and vertical vorticity tendency is built by introducing the frontogenesis function and the complete vertical vorticity equation, which is derived by virtue of moist potential vorticity. From the mathematical relation, it is shown that properly configured atmospheric conditions can make deformation exert a positive contribution to vortex development at rates comparable to other favorable factors. The effect of deformation on vortex development is not only related to the deformation itself, but also depends on the current thermodynamic and dynamic structures of the atmosphere, such as the convective stability, moist baroclinicity and vertical wind shear （or horizontal vorticity）. A diagnostic study of a heavy-rainfall case that occurred during 20-22 July 2012 shows that deformation has the most remarkable effect on the increase in vertical vorticity during the rapid development stage of the low vortex during its whole life cycle. This feature is mainly due to the existence of an approximate neutral layer （about 700 hPa） in the atmosphere where the convective stability tends to be zero. The neutral layer makes the effect of deformation on the vertical vorticity increase significantly during the vortex development stage, and thus drives the vertical vorticity to increase.

关键词： deformation low vortex vorticity frontogenesis function

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Study on a Mesoscale Convective Vortex Causing Heavy Rainfall during the Mei-yu Season in 2003

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Advances in atmospheric Sciences 2010年第5期27卷 1193-1209页

作者：孙建华赵思雄徐广阔孟庆涛 institute of atmospheric Physics Chinese Academy of Sciences state key laboratory of severe weather Chinese Academy of Meteorological Sciences

The strong heavy rainfall on 3–5 July 2003 causing the severe flooding in Huaihe River basin （HRB）, China is studied. It is noted that there are sometimes mesoscale convective vortex （MCV） in East Asia during the mei-yu season. Simulation results from the ARPS （Advanced Regional Prediction） data analysis system （ADAS） and WRF model were used to study the development of the mesoscale convective system （MCS） and mesoscale convective vortex （MCV）. It is confirmed that the MCV formed during the development of a previous severe MCS. A closed vortex circulation can be found below 600 hPa with a vorticity maximum in the middle troposphere. The evolution process of the MCV can be divided into three stages： initiation, maturation, and dissipation. During the mature stage of the MCV, a downdraft occurred in the center of the MCV and new convection developed in southeast of the MCV. The convergence and the tilting in the lower troposphere convergence and vertical advection in the middle troposphere were the main vorticity sources in the MCV initiation stage. Finally, a conceptual model between the mei-yu front and the embedded MCS and MCV is proposed. The mei-yu front was the background condition for the development of the MCS and MCV. A low level jet （LLJ） transported moisture and the weak cold air invasion via a trough aloft in the middle troposphere and triggering the severe convection. Furthermore, the intensified jet was able to result in the initiation of new ＂secondary＂ areas of convection in the eastern part of the MCV.

关键词： mesoscale convective system mesoscale convective vortex doppler radar WRF model

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A Modeling Study of Surface Rainfall Processes Associated with a Torrential Rainfall Event over Hubei,China,during July 2007

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Advances in atmospheric Sciences 2011年第6期28卷 1459-1470页

作者：周玉淑崔春光 laboratory of Cloud-Precipitation Physics and severe Storms Institute of Atmospheric Physics Chinese Academy of Sciences state key laboratory of severe weather institute of Heavy Rain China Meteorological Administration

The surface rainfall processes associated with the torrential rainfall event over Hubei,China,during July 2007 were investigated using a two-dimensional cloud-resolving *** model integrated the large-scale vertical velocity and zonal wind data from National Centers for Environmental Prediction（NCEP）/Global Data Assimilation System（GDAS） for 5 *** time and model domain mean surface rain rate was used to identify the onset,mature,and decay periods of *** the onset period,the descending motion data imposed in the lower troposphere led to a large contribution of stratiform rainfall to the model domain mean surface *** local atmospheric drying and transport of rain from convective regions mainly contributes to the stratiform *** the mature periods,the ascending motion data integrated into the model was so strong that water vapor convergence was the dominant process for both convective and stratiform *** convective and stratiform rainfalls made important contributions to the model domain mean surface *** the decay period,descending motion data input into the model prevailed,making stratiform rainfall *** rainfall was mainly caused by the water vapor convergence over raining stratiform regions.

关键词： surface rainfall processes torrential rainfall cloud-resolving model

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