Abstract:Atmospheric sounding is one of the most indispensable branch of atmospheric discipline.Since its inauguration in 1972 at Nanjing Institute of Meteorology(the former Nanjing University of Information Science and Technology),atmospheric sounding in NUIST had an experience of 48 years journey which owned the trials and hardship.In the consideration of the efforts and persistence of duo generations,reorganization and adjustment,the subject had always focused on the development goal of the school.This discipline is closely linked with construction subdivision which managed the national buildings demand,continuously explored and strengthened the individuals training.The establishment of qualified faculty and higher-level scientific research,made this systematic discipline a an established distinctive system,which has made a distinctive contribution in the development of the University and the meteorological department of China.This paper briefly introduces the connotation of atmospheric sounding,the overall situation of this discipline in NUIST and its development stages from its origin to establishment stage.In addition to this perception,different stages of the reforms development,the development and promotion stages in view of the discipline evolution and expansion,faculty development progression and practice and experimental equipments.Furthermore,the curriculum and teaching materials development,basic theory and technology research,meteorological system development,discipline construction and achievements were discussed in detail,and the prospects outlook of this discipline in the consideration of batter future.

Abstract:This paper reviews the advances on selected subjects of atmospheric physics in Nanjing University of Information Science and Technology (NUIST) during her 60 years of development,including the physical and chemical properties and microphysical structure of cloud and fog,the microphysical mechanisms of hail formation,the mechanisms of wire icing,the theory and practice of weather modification,the physical and chemical properties of atmospheric aerosols and their influence on cloud and precipitation,the atmospheric boundary layer physics,and the atmospheric electrical processes.

Abstract:The established precipitation skill scores are influenced by the conventional duplex retribution problem which is induced by slight spatial and temporal contradiction between forecasts and observations.The FSS (Fraction Skill Score) is considered an approved scientific and problem-solving spatial technique that has been proposed in many articles for deterministic validation.In addition,this technique disclosed significant advantages in the directive of solving duplex retribution problem.In the consideration of high-resolution ensemble forecast,the ensemble precipitation forecasts also owned the corresponding problems with deterministic forecasts.In this research article,a novel ensemble precipitation verification skill score with spatial technique EFSS (Ensemble Fraction Skill Score) is developed based on extending FSS and deterministic ensemble forecasts.By using daily ensemble forecast obtained from ECMWF (European Centre for Medium-Range Weather Forecasts),QP and National Meteorological Information Center (NMIC) during June and August of 2018,the scoring consistency and the difference of traditional skill score in operational application have been analyzed.The consequences of this research indicated that EFSS is not affected by the ensemble members and the consistent evaluation can be obtained.The EETS (Ensemble Equitable Threat Score) was extended from deterministic traditional skill score that is suitable for ensemble forecasting.The comparison of EFSS and EETS indicates that the traditional skill scoring owned the \soutis limited skills in the directive to effective assessment of different characteristics of heavy precipitation processes.It can be concluded that,the EFSS technique can effectively improve the identification of heavy precipitation forecast verification.

Abstract:In this study,based on ERA-Interim reanalysis data taken four times a day and daily precipitation data from 753 stations throughout China,the characteristics of summer precipitation in the Yangtze-Huaihe River Basin from 1980 to 2013 are analyzed.The forecast signal of summer low-frequency precipitation in the Yangtze-Huaihe River Basin is explored.The results show the following:1) The 10—30 days low frequency precipitation,which occupies a large proportion in the summer precipitation,can influence the summer precipitation over the Yangtze-Huaihe River Basin.2) At 200 hPa,there is a low-frequency anticyclone moving from the northeast of the Tibetan Plateau to eastern China 9—6 days before the low-frequency precipitation process occurs.At 500 hPa,the Western Pacific Subtropical High moves from east to west,reaching the eastern coastal areas of China 9 days before the occurrence of the low-frequency precipitation events.The center of negative low frequency OLR in the tropics moves northward and reaches the strongest point when its northern most tip reaches the Yangtze-Huaihe River Basin.The above circulation distribution will promote the occurrence of the low-frequency precipitation in the Yangtze-Huaihe River Basin,or vice versa.3) The Tibetan Plateau prediction signal can effectively supplement the deficiency of the West Pacific Subtropical High and the Tropical OLR Signal.The accuracy of precipitation process prediction relying only on the low latitude signals can be improved by using the Tibetan Plateau Signal,the Western Pacific Subtropical High Signal and the Tropical OLR Signal as the comprehensive predictors.

Abstract:In this study,based on the quality-controlled S-band dual-polarization radar gridded observation data,a hydrometeors classification recognition algorithm is established,so as to analyze the spatial distribution and evolution of hydrometeors in the precipitation process by using the fuzzy logic algorithm,as well as the characteristics of hydrometeors scattering and spatial orientation.This algorithm can classify hydrometeors into different types such as liquid,ice,and mixed states,which is helpful in finding the key structures of cloud microphysics which affect the precipitation.First,the membership function is obtained according to the radar echo characteristics of hydrometeors.Second,according to the different contributions of radar observation variables in identifying hydrometeor types,the weight of the membership function value corresponding to each observation value is determined,and,after the weighted average of each function value is obtained,then the logical value corresponding to hydrometeors types is obtained as well.Finally,the integration and defuzzification processing is performed,and the maximum value of the logical value in each grid point is selected,after which the hydrometeor type represented by the value is considered to be the particle type represented by the grid point.When determining the weight of the membership function corresponding to the observed value,the horizontal reflectance factor and ambient temperature are taken as the direct influence factors for calculating the hydrometeor types,and,instead of the weighted average calculation,an algorithm for hydrometeor types recognition based on the parameters of S-band dual polarization radar and the ambient temperature is proposed.Next,the rationality of the algorithm is verified by means of a precipitation process in the pre-flood period of South China using radar and precipitation data.The study results show that the distribution characteristics of the rain-type obtained by the inversion are basically consistent with the distribution characteristics of the actual observed precipitation,which proves that the algorithm is able to reflect the hydrometeor types in the precipitation area,and that the recognition results are basically reasonable.Further research shows that there are a large number of drizzle-type particles present in the air before the occurrence of precipitation,and that there is a negative correlation between the changes of drizzle and rain particles during the process of precipitation,thereby indicating that this precipitation is mainly caused by the collision of drizzle and rain particles.

Abstract:The relationship between soil moisture and precipitation has became a research focus,because soil moisture has the “memory”.Using the data of soil moisture from CPC (Climate Prediction Center) and the SVD (Singular Value Decomposition) method,the influence of soil moisture on summer precipitation in Tibetan Plateau (TP) in spring was discussed.The results showed that the cumulative covariance percentages of the first two modes reached 59.15%,and the time correlation coefficients of the two field expansion sequences were 0.78,reflecting the main characteristics of the two field relations.The soil moisture field shows the consistency of the north and south phases;however,the consistency of the precipitation field was weak.The first mode indicated that when the soil moisture in the northern part of the TP in spring was higher than that of other areas,the precipitation in the northern and southeastern part of the TP in summer was lower than that of other areas.The second mode indicated that when the soil moisture was higher than that of other areas in most areas of the TP in spring,the precipitation in the northern and central parts of the plateau was higher than that of other areas in summer,and the precipitation in the southern part was low.The 500 hPa circulation and precipitable water field match well.When the soil moisture was relatively high in spring,negative anomalies were controlled in the northern part of the TP,and the corresponding high-level precipitation was relatively large.The configuration was conducive to more precipitation in the southwest of the TP.

Abstract:Based on the observations and the regional climate model (RegCM4.6),this paper analyzes the possible effects of synoptic scale disturbances at mid-high latitudes and low latitude on the precipitation of Meiyu period in 2020.The observation analysis shows that in June and July of 2020,the precipitation in the middle and lower reaches of the Yangtze River shows a synoptic scale disturbance of less than 10 d in the period,and there are many times of synoptic scale disturbances in middle and high latitudes (low latitude) propagating southward (northward).On this basis,the side boundary sensitivity experiments are designed to change the input of synoptic scale disturbances (<10 d) at different latitudes.Numerical simulation results show that from the perspective of average circulation,when the synoptic scale disturbances on the northwest boundary of middle and high latitudes weaken,the conversion position from the kinetic energy of atmospheric average circulation to the kinetic energy of synoptic scale disturbance moves northward,which affects the northward movement of the westerly belt on the north side of the subtropical high,and makes the precipitation center move northward from the middle and lower reaches of the Yangtze River to the Huaihe River Basin during the Meiyu period.From the perspective of time evolution,when the synoptic scale disturbances on the northwest boundary of middle and high latitudes is removed,the southward propagation of E vector divergence at 850 hPa weakens,and the low latitude zonal wind anomaly can propagate to the north.The vorticity change caused by zonal wind anomaly is beneficial to the northward uplift of subtropical high,which makes the rain belt move northward to the north of 34°N earlier,marking the end of Meiyu season in Jianghuai region.However,when the synoptic scale disturbances on the south boundary of low latitude weaken,the precipitation increases lightly,but there is little influence on the advance and retreat of rain belt during the Meiyu period.It can be seen that the intensity of precipitation and the maintenance of rain belt during the Meiyu period in the summer of 2020 are closely related to the synoptic scale disturbance anomalies in the middle and high latitudes.The strong synoptic scale disturbances in northern China,especially from Northwest China to Lake Balkhash,and its southward propagation are the important reasons for the strong intensity of the Meiyu precipitation and the maintenance of the rain belt.

Abstract:In this study,targeted at the uncertainty in the parameterization process of the planetary boundary layer in the WRF model,a Stochastic Perturbation on Planetary Boundary Layer Parameterization Tendency scheme (SPPBLPT) was developed.This scheme perturbs the temperature,wind and water vapor tendencies.A comparative experiment was conducted in July 2014 using the SPPBLPT scheme,multi-planet boundary layer parameterization scheme,multi-parameter perturbation scheme,and Stochastic Physical Process Perturbation (SPPT) scheme.It was observed that the SPPBLPT scheme with a large grid-point variance can effectively reduce the error of 2 m temperature and wind field,and it can also reduce precipitation error,while other schemes do not improve the forecast significantly.The BS scores for the 2 m temperature and wind field show that the SPPBLPT scheme significantly improves the possibility of ensemble forecasting for temperature and wind field,by reducing the reliability score,thereby increasing performance.At the same time,the scheme can significantly improve the GSS score of the precipitation.In all experiments,the SPPBLPT scheme with the larger grid-point variance had a superior performance.Although the SPPBLPT scheme reduced the FSS score,the reduction was not significant.It is thus shown that the SPPBLPT scheme can significantly improve the performance of ensemble forecasting systems,yet the setting of perturbation parameters for this scheme requires further investigation.

Abstract:Based on the daily 6 h 850 hPa geopotential height field data from ERA-Interim reanalysis data during 1979—2013,the two-dimensional cyclones affecting the Yangtze-Huaihe River valley (YHV) in spring are extracted by using the automatic identification method of outermost closed contour of cyclones.The relationship between interannual anomaly of subsynoptic-scale cyclone activity and precipitation anomaly in YHV is studied.Results show that the subsynoptic-scale cyclone activity has an obvious effect on spring precipitation in most areas of YHV,with a contribution rate of more than 25%.The subsynoptic-scale cyclone activity has corresponding significant regional cyclonic vortex and convergence motion in the lower troposphere,which provides favorable dynamic conditions for the local precipitation enhancement.The interannual variation of subsynoptic-scale cyclone intensity has a significant positive correlation with the precipitation anomaly and the occurrence frequency of heavy precipitation in the southeast of YHV in spring.When the subsynoptic-scale cyclone intensifies in YHR,an anomalous inverted trough circulation appears from the Qinghai-Tibet Plateau to the lower-middle reaches of the Yangtze River in China,which is conducive to the formation of cyclonic circulation anomaly in YHV.Simultaneously,the atmospheric baroclinicity increases in the lower troposphere when the southwest warm and moist air flow in southern China strengthens,which promotes the enhancement of subsynoptic-scale cyclone in YHV.The anomalous heating of air column over the Qinghai-Tibet Plateau in spring,which leads to the decrease of potential height in the lower troposphere and the strengthening of southwest flow in southern China,may be the main reason for the enhancement of subsynoptic-scale cyclone activity in YHV.

Abstract:Based on the surface ozone observation data from 222 cities of 20 provinces in eastern China and the global reanalysis wind data from 2015 and 2019,this paper investigated the spatial-temporal distribution characteristics of ozone in eastern China and evaluated the influence of ozone photochemical transport in the upwind on seasonal variation of ozone mass concentration in the downwind under the background of Asian summer monsoon (ASM).Results show that the ozone mass concentration in eastern China is higher in summer and lower in winter,and increases in the order of Southeast,East,Northeast and North China.The ozone mass concentration in North China and Northeast China at middle and high latitudes is significantly higher than that in East China and South China at middle and low latitudes.Diurnal variations of ozone mass concentration exhibit similar single-period patterns that remain low at night,gradually increasing in the morning and reaching peak during afternoon and twilight in different cities and seasons,showing typical photochemical controlling characteristics.In spring,ASM starts to influence eastern China and causes a large area of high ozone mass concentration in East,North and Northeast China.In summer,ASM continuously transports and accumulates ozone and its precursors from South China and East China with lower latitude to North China and Northeast China with higher latitude,and photochemical reaction occurs under the action of summer strong ultraviolet radiation,leading to summer ozone pollution in North China and Northeast China.

Abstract:In this article,the time series of haze days were constructed on the basis of past 64 years data which was collected from the national meteorological observatory of Wuhan and 130 climate system indexes of the National Climate Center during the time spread from 1955 to 2018.The linear trend analysis and Mann-Kendall were validated to analyze the climatic characteristics of haze days in Wuhan during this specific period.In the next stage of this research method,the stepwise multiple regression analysis was adopted in order to develop the prediction equations and quantitative monthly forecast scale of haze days.While in this piece of research,climate system index and haze days were considered as independent and dependent variables accordingly.The consequences of this research indicated that the reconstructed time series of haze days contemplated the actual long-term variations in haze days characteristics of Wuhan.During the selected span of time,the climatic characteristics in terms of annual haze days expanded significantly while the unanticipated variations were observed around the 1980s.It can also be observed that the span of seasonal haze days in winter and autumn comparatively more expanded than the summer.The number of seasonal haze days significantly increased in winter and autumn and in contrast decreased spring and summer seasons.The aggregate of monthly haze days in November,December,and January significantly increased while on other side declined in July and August.In the consideration of serious climatic conditions of haze days significantly increased and owned the gradient feature in winter and less effective in summer.The aggregate of moderate or more serious monthly haze days in November,December,and January significantly increased while on the other side declined in May,June,and August.Based on the outcome it can be concluded that discrete monthly haze days and harsh haze days owned a significant correlation with many monthly climate system indexes.The results showed that this prediction method had a great effect in Wuhu and wealth simplifying broadly in similar areas.

Abstract:By considering the aircraft observational data of the stratocumulus obtained during the Routine AAF (Atmospheric Radiation Measurement(ARM) Aerial Facility) Clouds with Low Optical Water Depths(CLOWD) Optical Radiative Observations(RACORO) field operation that was accomplished in April and May 2009,two approaches were adopted in order to estimate the aerosol incidental effects.The first effect was estimated by considering the cloud drop concentration(AIE_n),while the second effect was estimated by considering the effective radius(AIE_s).It was observed that the AIE_n always owned the higher value in comparison with AIE_s,and this alteration was more projecting especially at moderate liquid water content.Theoretical derivation established on the base of deviation between AIE_n and AIE_s indicated that the dispersion of cloud droplet spectrum influentially related to the effect of aerosol in the consideration of the dispersion effect.It was observed that when the dispersion effect increased the value of evaluated AIE_n come closer to the evaluated value of AIE_s,and the happening of this corresponds authenticated the theoretical expectations.The contribution of the dispersion effect in the consideration of the aerosol indirect effect was the leading offset effect,which owned the largest value at moderate liquid water content,and it was observed that when liquid water content is 0.24 g/m³ then its corresponding percentage was about 37%.The consequences of this research enhance the theoretical understanding of the aerosol-cloud interaction and it can be concluded that it could be helpful asset to improve the accurate assessment of the aerosol indirect effect in models and observations.

Abstract:In recent years with the development of social economy,the Yangtze River Delta has experienced serious haze pollution,which has brought great harm to traffic safety,ecosystem and human health.Taking the interannual increment of haze days as the prediction object and the external forcing factors in the early stage as the independent variables,the prediction models of winter haze days in the Yangtze River Delta are established by using the multiple linear regression method and the generalized additive model.By comprehensively investigating the results of “one-year-out” cross validation and cyclic independent sample prediction test,this paper selects the optimal modeling method applicable to each model and compares the Yangtze River Delta winter haze days prediction model (MODEL1) and the Yangtze River Delta haze days prediction model in different winter months (MODEL2).Root mean square errors (explained variances) of MODEL1 and MODEL2 are 2.69 (80.01%) and 2.76 (79.04%),respectively.Both models can successfully capture the interannual and interdecadal trends and extreme values of haze days.The percentage of the same sign (meaning mathematical signs of fitted and observed haze days anomalies are same) predicted by MODEL2 (97.3%) is better than that predicted by MODEL1 (86.49%),showing that MODEL2 has better ability to capture the anomalous signs.By selecting external forcing factors before November,MODEL1 can predict winter haze days one quarter in advance.MODEL2 can constantly predict monthly haze pollution by selecting newer external forcing factors.By combining the two models,it can more accurately predict winter haze days in the Yangtze River Delta,which provides reliable scientific and technological support for the haze pollution control.

Abstract:From 1979 to 2016,Northeast China experienced 259 summer extreme high temperature (EHT) events.This study uses the hierarchical clustering method to classify the 500 hPa geopotential height anomalies of those EHT events and investigates the circulation evolution characteristics of different types of EHT events and their relationships with sea surface temperature (SST) anomalies in the North Atlantic.Results show that summer EHT events in Northeast China can be divided into three types,namely the westerly-type,blocking-type and wave-train-type with the occurrences of 113,89 and 57,respectively.The main feature of atmospheric circulation in the westerly-type EHT events is that there is a stronger polar vortex than normal and a shallow ridge moving eastward along the westerlies.Under the guidance of westerly wind,when the anticyclone anomaly controls over Northeast China,an EHT event is formed.When the blocking-type EHT event occurs,its corresponding atmospheric circulation shows that the blocking high over the Ural Mountain is stronger,and the northwest airflow subsides and heats Northeast China locating in the front of the high ridge,thus leading to the extreme high temperature event in Northeast China.The main circulation characteristics of wave-train-type EHT events are “+-+” wave-train-type circulation anomalies over Eurasia in the troposphere,and Northeast China is controlled by an anticyclone anomaly,resulting in an EHT event.Due to the maintenance of upstream wave energy,the duration,influence range and intensity of the wave-train-type EHT events are greater than those of the first two types.Based on the composites of SST anomalies 10—20 days before the occurrence of three types of EHT events,it is found that there are no significant SST anomalies in the North Atlantic before the occurrence of westerly-type and blocking-type EHT events.Before the occurrence of the wave-train-type EHT event,significant positive SST anomalies in the tropical North Atlantic are observed.There is a significant positive correlation between the SST anomalies in the North Atlantic and the intensity of the wave-train-type EHT event.Results of regression analysis show that the positive SST anomalies in the North Atlantic are conducive to the maintenance of zonal wave-train-type circulation anomaly over Eurasia in summer,which provides favorable conditions for the occurrence of wave-train-type EHT events.

Abstract:The ensemble transform Kalman filter (ETKF) is an effective ensemble prediction initial perturbation scheme and is widely used.However,the finite ensemble sample size,the same ensemble member setting in ETKF and the forecast model error may make the two remote state variables have higher spurious correlation,thus affecting the quality of ETKF ensemble perturbation.The reason why ETKF generates spurious correlation is that each ensemble member is an estimate of the atmospheric state,while the degree of atmospheric freedom is too high,and the limited ensemble members are difficult to fully express.On the other hand,due to the effect of the forecast model error,the same size of members may lead to convergence of different ensemble members in the prediction process,resulting in spurious correlation.In order to solve this problem,the localization of ETKF,called LETKF,is proposed.By means of localization,the spurious correlation of error variance can be truncated in the localized radius,thus improving the quality of error variance.That is to say,only the observation data in the local radius are absorbed and aimed at a grid point,and the observation outside the radius is not taken into account so as to avoid the spurious correlation at a distance.Based on the GRAPES regional ensemble prediction system (GRAPES REPS),the localization scheme of ETKF initial perturbation is developed on the basis of the ETKF initial perturbation scheme,in order to solve the problem of the range spurious perturbation and the divergence of the filter in the regional ensemble prediction.Through the continuous experiments for 7 days,this paper analyzes the ensemble prediction quality of LETKF initial perturbation scheme from the case of rainstorm and multiple scoring methods of ensemble prediction.Results show that the localization scheme of ensemble transform Kalman filter initial perturbation in regional ensemble prediction can more reasonably capture the physical structure of the rapidly growing analysis error,and more accurately reproduce the linear and nonlinear propagation and evolution characteristics of the forecast error in the numerical model.The localization scheme can improve the quality of forecast and increase the accuracy of precipitation forecast,especially for the forecast of magnitude of light rain,moderate rain and rainstorm.Compared with the existing regional ensemble prediction business system GRAPES REPS,the regional ensemble prediction produced by LETKF initial perturbation scheme has obvious advantages.In general,the LETKF initial perturbation scheme can improve the quality of regional ensemble prediction.