Abstract:It is of great importance to study winter precipitation because it can directly affect agricultural production and public travel,and even threaten human safety.For lack of researches on winter precipitation,especially in North China,this paper mainly focuses the distribution and evolution of winter precipitation in North China.Based on the winter precipitation data at 160 stations in China,the NCEP/NCAR reanalysis data and the NOAA ERSST data during 1951/1952-2012/2013,the characteristics of winter precipitation anomaly in North China and its relationship to atmospheric circulation and sea surface temperature(SST) are studied.Common statistical methods including EOF reanalysis,synthesis analysis and correlation analysis are effectively used.The overall characteristics of winter precipitation indicates that although the total amount of precipitation is small,the precipitation variability is large in North China.EOF analysis results show that there are characteristics of uniform change of the whole area for winter precipitation in North China,and the interannual variability is large,with 2-4 years period.Based on the winter precipitation index defined by the data of 19 representative stations in North China,the more and less winter precipitation years are obtained.During the more(less) precipitation years,Siberian high is weaker(stronger),Aleutian low is weaker(stronger),and the northwest cold air is also weaker(stronger).At 850 hPa,the prevalent northwest wind in North China is weaker(stronger),East Asian winter monsoon dominating North China is weaker(stronger) simultaneously,and the southerly(northerly) wind anomaly also exists in North China.At 500 hPa,East Asian trough and Ural ridge are both weaker(stronger),the blocking system in mid-latitudes is weaker(stronger),and the flat westerly current(strong northwest wind) anterior the ridge takes control.Furthermore,two dominating water vapor transport channels that affect North China winter precipitation are found:one from South China Sea,and the other from the western Pacific to the east of South China Sea.The relationship between North China winter precipitation anomaly and sea surface temperature is also studied.The significant positive correlation between North China winter precipitation and previous summer(contemporaneous winter) SST locates in the westerly drift region to east of Japan(the Yellow Sea and Bohai Sea region).

Abstract:Cold surge is one of main features of East Asian winter monsoon,and can lead to high influence weather,for example,low temperature and chilling injury.The cold surge over the northern South China Sea(SCS) is closely associated with the outbreaks of cold air influencing most part of China,and results from the interaction between the mid-high latitudes circulation and the lower latitude circulation.Southward movement of cold surge shows two kinds of gravity wave,which are influenced by dynamical effects of large-scale topography significantly.The high-frequency inertia-gravity and Kelvin waves are correspondence to the front of cold surge events and the maximum northerly center of cold surge,respectively.In this paper,based on the atmospheric circulation model NCAR CAM3,the influences of altitude changes of the Tibetan Plateau on the cold surge over the northern South China Sea and circulations have been investigated by comparing the results between the sensitivity experiments and the control experiment.The results show that the flow around topography is closely associated with the formation of the Aleutian low and East Asian trough,and when the large scale topography does not exist,the Aleutian low and East Asian trough disappear.The changes of topography altitude does not influence the formation of cold high over the continent,but it can influence its intensity,showing that the intensity of continental cold high decreases with the decrease of topography altitude of Tibetan Plateau.The large scale topography plays an important role on the planetary mean trough and ridge over mid-high latitudes.The decrease of topography altitude leads to the decrease of meridionality of circulation over mid-high latitudes,which is not conducive to cold air southward and further influences the intensity and frequency of cold surge events.When the topography altitude is halved,due to the eastern part of the continent is relatively flat,the intensity of the northerly over the northern SCS increases,leading to the increase of occurrence frequency of cold surge over the northern SCS.When there are not topography,the meridionality of circulation over mid-high latitudes in East Asia decreases significantly,and the southward movement of cold air decreases obviously.Meanwhile,the southward movement of Kelvin wave triggered by the Tibetan Plateau disappears,inducing the decrease of northerly over the northern SCS and the significant decrease of occurrence frequency of cold surge over the northern SCS.

Abstract:Based on the monthly Standardized Precipitation Evapotranspiration Index(SPEI),ocean temperature data from ORA-S4,and National Center for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR) reanalysis data during 1961-2014,this study investigates the decadal shift of autumn drought in South China and its possible relationship with Heat Content(HC) in the tropical Indian Ocean.Results show that the main spatial distribution of autumn SPEI change in South China is in the same phase,with an obvious interdecadal change from wet to dry around 1988.It is further noted that there exists a significant positive relationship between SPEI in South China and HC in tropical western Indian Ocean in autumn,indicating that autumn drought in South China will be corresponded to a lower HC in tropical western Indian Ocean.The lower HC in the tropical western Indian Ocean plays an important role in the decadal drought in South China in autumn.There is an obvious zonal dipole pattern of HC anomalies shown as "<" type in the tropical Indian Ocean in autumn.The positive HC anomalies in the tropical eastern Indian Ocean,which are possibly affected by the negative HC anomalies in the tropical western Indian Ocean,are closely related to the less OLR,more precipitation and higher sea surface temperature(SST) in the tropical eastern Indian Ocean and western Pacific(TEIWP) region.These changes will give rise to an enhanced East Asian Hadley cell,and then a subsidence motion anomaly over South China,resulting in a decadal drought in this region.In addition,the positive SST anomalies over TEIWP will make the northwestern Pacific subtropical high get larger than usual,and extend westward.It also induces cyclonic circulation anomaly around the northwestern Pacific.In such cases,South China is controlled by northerly wind anomaly,reducing the amount of water vapor transported to South China.As the interdecadal change of SST in TEIWP is an important physical process for the HC anomalies in tropical western Indian Ocean,which influences the decadal shift of autumn drought in South China,a series of numerical experiments using NCAR CAM5.1 verify that the decadal warming of SST in the TEIWP region plays an important role in causing the decadal autumn drought in South China.

Abstract:Based on the observation data and the ECMWF reanalysis data,the forecast products made by STI-THRAPS (Shanghai Tropical cyclone High resolution Analysis and Prediction System) and other four models,ECMWF/EC(European Centre For Medium Range Weather Forecasts),GFS(The Global Forecast System),JMA(Japan Meteorological Agency) and T639(TL639L60 Global Model),are verified and assessed by statistic method for typhoon Fitow.The results show that the STI-THRAPS has significant advantages for the prediction of torrential rain and severe rain.The score of STI-THRAPS is better than other models.There is little difference between each two models of the prediction from light rain to heavy rain.GFS and STI-THRAPS have made a good prediction for the wind area.The special related degree of wind filed between STI-THRAPS and observation is the most optimal.Besides that,STI-THRAPS has significant advantages in false alarm ratio and false negative ratio.The STI-THRAPS model is the best at the prediction of the track after 24 h,but the center pressure and the maximum wind speed are higher than observation.

Abstract:A new PJ index is introduced by using the singular value decomposition(SVD) method at the 500 hPa height field in summer in East Asia as well as in precipitation field near the Philippines.This time series/index can clearly reflect the PJ interannual and interdecadal variations,which were demonstrated by the 500 hPa height switching from "cyclone,anticyclone,cyclone" to "anticyclone,cyclone,anticyclone" in the late 1970s.This study also shows that the interannual variation of the PJ index is closely related to the El Niño Southern Oscillation(ENSO) event.El Niño teleconnection makes the Sea surface temperature(SST) in tropical Indian Ocean(TIO) increase like a battery charging a capacitor,and the increased temperature leads to the formation of abnormal anticyclones near the Philippine Sea.In addition,ENSO events also stimulate the PJ teleconnection pattern along the coast of East Asia.Moreover,the interdecadal variation of PJ patterns is related to the continuous increasing TIO SST.Many researchers have proposed that SST anomalies near the Philippine Sea result in anomalous convection and stimulate the PJ teleconnection pattern along the coast of East Asia.However,we have concluded that variations of SST in this area are not the reason for the interannual and interdecadal variations of the PJ pattern.Instead,these variations result from the TIO SST anomalies.The SST anomalies over the Philippine Sea are caused by the NW Pacific anticyclone,thus the radiation increases(decreases),the evaporation decreases(increases),the thermocline deepens(shoals) and the SST becomes warmer(colder).The increased SST in this area corresponds to weakened convection.Furthermore,numerical simulations by using the atmospheric circulation model ECHAM5.4(European Centre Hamburg Model5.4) show that when the TIO SST increases,anticyclones are produced near the Philippine Sea and stimulate the "anticyclone,cyclone,anticyclone" PJ teleconnection pattern along the coast of East Asia.

Abstract:Based on high spatial and temporal resolution surface observational data,sounding data,NCEP reanalysis data,Doppler radar data,and high resolution data produced by WRF model,the severe squall line event that occurred over Guangxi and Guangdong Provinces on 15 May 2013 is analyzed.The paper mainly focuses on the transition process and mechanisms of mesoscale convective system(MCS) mode from PS mode to TS mode.
The facts of observation showed that the squall line formed in the region which was under the divergence area at 200 hPa,ahead of the eastward trough at 500 hPa,between the northwestern shear line and the southeastern low-level jet at 850 hPa,near the surface cold front and in the area of surface inverted trough.The initial convection was triggered in the north of the surface inverted trough.The western convection was organized into PS mode owing to the surface cold pool and strong divergence,but no thunderstorm high was seen in the mature stage.The eastern weakening convection strengthened again when moving to Guangdong Province,and then combined the western PS MCS to convert to typical TS mode with thunderstorm high,wake low,and cold pool.
In order to analyze the mechanisms of the transition,WRF model was used.The results of simulation were almost in accordance with the observation facts in the isochrones of the squall line,the 12 h simulated cumulative precipitation,and the transition process from PS mode to TS mode.The main results could be summarized as follows:
(1)The initial convection was triggered in the center of Guangxi Province.There were two convections in the beginning.One of them was the line convection in the northeast of Laibinand the other was the convection in the west of Laibin.The latter developed to northwest-southeast PS mode later.The former developed again when moving eastward to combine with the western PS MCS to typical TS mode with bow echo and stratiform cloud in the north.
(2)In the northwest-southeast PS mode,the pressure perturbation was negative in the convective regions.The pressure perturbation was positive in the southwest of the convective regions,which resulted in line-perpendicular pressure gradient force.So that the line-perpendicular pressure gradient force also resulted in line-perpendicular acceleration and stream.But in the southeast of the convective region,the pressure perturbation was positive,which resulted in great line-parallel pressure gradient force,acceleration and relative line-parallel stream.The result that PS mode had deep line-parallel stream which matches with the conclusion of Parker(2007a,2007b).
(3)When the squall line developed into TS mode,the pressure perturbation in the convective regions was still negative,while the pressure perturbation in the southwest of the line was still positive,thus there was still great line-perpendicular pressure gradient force,acceleration and relative line-perpendicular stream as PS mode.However,the positive pressure perturbation in the southeast of convective regions in the PS mode was converted to be negative,which made the line-parallel pressure gradient force,acceleration and relative line-parallel stream disappear.
Generally speaking,in PS mode there was strong line-parallel stream for line-parallel pressure gradient force and acceleration.But the stream was converted to be line-perpendicular in TS mode for the disappearance of line-parallel pressure gradient force and acceleration.It was this change which led PS mode to TS mode.

Abstract:This paper defines a group of seasonal and monthly mean new circulation indices of Aleutian low(AL) at 1 000 hPa in winter,including intensity(P),area(S) and central position(λ_c,φ_c).The circulation indices are calculated by using the NCEP/NCAR monthly mean height field at 1 000 hPa during 60 winters from 1948/1949 to 2007/2008.The climatological and anomalous characteristics of AL are analyzed by the circulation indices,focused on analyzing the correlation relationships between circulation indices(P and λ_c) with sea surface temperature(SST) in Pacific,temperatures and precipitation in the Northern Hemisphere during the corresponding period,respectively.Results show that:1)AL is the strongest with the center lying to the south and west of the normal position in January,the weakest with the center lying to the north and east in December,and the middle in February.2)There is a negative correlation between P and λ_c,with the center lying to the east of the normal(λ'>0) in the AL strong years(P'<0) and to the west in the weak years.On the interdecadal scale,AL has continued to be strong and eastward since 1970s,but there are reversing signs in recent years.3)AL is stronger and lies to the east of the normal in the strong El Niño years,and it is opposite in the strong La Niña years,which is particularly evident after 1975.There is a significant positive correlation between AL and SST in the mid-latitude Pacific,with AL strengthening and moving eastward in the SST negative anomaly years.4)The significant correlation zones distribute as the great circle wave train of "+-+" signs between AL index(P) and temperature,precipitation over the mid-and high-latitudes in the Northern Hemisphere during the same period,respectively.The correlation centers locate in the mid-latitude North Pacific,northwest and south of North America,close to the PNA(Pacific-North America) teleconnection pattern,whereas there are obvious differences between them in the tropical regions of the Northern Hemisphere.AL and Mongolian high are two adjacent atmosphere activity centers over the mid-and high-latitudes in the Northern Hemisphere in winter,but their correlation relationships with the El Niño/La Niña events,temperature and precipitation in the Northern Hemisphere during the same period are significantly different,which are questions worthy of further study.

Abstract:The numerical simulation and diagnostic analysis of a double rainbands storm process from 1800 UTC 12 June 2008 to 0000 UTC 14 June 2008 in south China are conducted by using real time data and mesoscale numerical model WRF.The results show that:as the front moves towards south,a vortex is generated in Guangxi coastal area,which is located in the southwest of the front.As a source of potential vorticity,this vortex performs stably in the mid-high levels,providing positive potential vorticity for frontal rainband and warm sector rainband respectively.The main effects from southern to northern rainbands are mainly at middle levels,near 112-114°E.Large-value potential vorticity in southern rainband tranports towards north,leading to the connection of these two rainbands here,but in the east of 115°E,southern rainband has no obvious transport processes.At the same time,northern upper-level trough also transports large-value potential vorticity to the northern rain belt to maintain it.This study also finds that significant structure differences between warm area rainstorm and frontal rainstorm,and the structure is identified with frontal rainband and traditional rainband.The pattern in favor of warm area rainfall is mainly at mid-high levels,warm area rainband has the structure of three-layers with different properties.This structure is conducive to the maintenance and increase of the precipitation.RIP particle trajectory model also demonstrates that the potential vorticity transmission source in the particle movements is the vortex located in Guangxi coastal area,showing that this potential vorticity source plays an important role in the formation of these two rainbands.

Abstract:The Tianshan Mountains are the largest set of mountain range in middle Asia.As such,as a result of their extended zonal topography,they partially determine the distribution of the water resources in Xinjiang during the summer months,due to their capability of stimulating precipitation events.The precipitation events which are induced by the Tianshan Mountains' topography have significant benefits for the arid and sub-arid regions near Xinjiang.In this research,the aim was to explore the dynamical structures,transportation of water vapor,and microphysical mechanisms which are affected by the Tianshan Mountains' topography.A severe convective rainfall event which occurred during the summer of 2011 over the middle section of the eastern Tianshan Mountains was analyzed using the available data from ordinary observations,and automatic weather stations,along with Fengyun-2D (FY-2D) Temperature of Black Body (TBB) measurements.A Weather Research and Forecast (WRF) model with a nested domain setting was also employed in this study.When compared with the observational and satellite data,the WRF output was found to be nested in three sub-domains which had different spatial resolutions,and together,these data were found to reasonably recapture this particular precipitation event.Therefore,a more detailed analysis of the large-scale dynamics and microphysics was conducted in this study,in order to retrieve the features of this topographical-induced precipitation event over the middle section of the eastern Tianshan Mountains.The results showed that the eastern Tianshan Mountains had blocked one airflow moving towards the east,and split the flow going around the eastern Tianshan Mountains from the northern and southern slopes.On the level of 900 to 800 hPa,a northern jet stream converged following the Yili Valley,and then turned toward the southwest,before climbing Mount Poluokenu,which has a relatively low altitude in the west section of the northern Tianshan Mountains.Therefore,the northern sub-flow was determined to have originated from a clockwise turning of the northern jet stream at the right exit of the jet flow before it was forced topographically by the northern slope of the middle section of the eastern Tianshan Mountains.On the level of 750 to 650 hPa,a southwestern jet stream developed after the southern jet stream climbed the southern Tianshan Mountains to reach the Talimu Basin,and then turned to the north due to being affected by an anti-cyclonic system over the Tulufan region.It then formed a southern sub-flow which climbed up the southern slope of the northern Tianshan Mountains after reaching the Yanzhe Basin.These two sub-flows eventually merged at the top of the middle section of the eastern Tianshan Mountains,and together dynamically favored the development of local convections in which the northern sub-flow became the main source of the water vapor,which potentially caused the severe rainfall event.As can be seen from the large-scale dynamics,the high level southwestern airflow led to ice-phase cloud bodies with depths of 5 to 6 km on the northern slope of the middle section of the eastern Tianshan Mountains.These merged with the low level deep convections which have already been formed there.Then,the cloud particles in the form of super cooled water were able to be uplifted to a higher level,and co-existed with the ice particles in the ice-phase clouds.This co-existence enabled a much stronger Bergeron process,and a riming process was determined to have occurred,which accelerated the growth of the cloud particles.This in turn caused heavy rain fall processes to occur in the area.Therefore,based on both the observations and numerical simulations,this study was able to present a better understanding of the topographical effects of the Tianshan Mountain regions on heavy rainfall events.The results of this study may also potentially act as a reference for future weather forecasts and modifications in the mountainous areas of Xinjiang.

Abstract:The water vapor in the lower stratosphere may play an important role in atmospheric radiative processes and chemistry.One source of water vapor in the lower stratosphere is the transport of water vapor from the troposphere via deep convection penetration.The aim of this study was to uncover the physical mechanism for transporting water vapor into the lower stratosphere by deep convection penetration.During the development of a supercell in Montana(US),it was observed that the CCOPE(Cooperative Convective Precipitation Experiment) could be simulated using a WRF-SUPERCELL model performing under idealized conditions,and initialized with soundings obtained from the CCOPE.Simulation tests were conducted,in which a Thompson bulk microphysics scheme with a series of initial cloud droplet number concentration(N_c) was set.The results showed that the test in which N_c=175 cm^-3exhibited the closest maximum in-cloud updraft to the observations.On the other hand,the simulation results where N_c=175 cm^-3displayed characteristics which were similar in structure to a supercell,such as the bounded weak echo,overhang echo,and mesocyclone.Also,the supercell's penetration into the lower stratosphere could consequently be used to analyze the physical mechanism of the water vapor transportation into the stratosphere via a supercell penetration.It was determined that the dehydrating effect of the overshooting could be effectively simulated.However,dehydration did not occur on the tropopause and lower stratosphere.This was due to the fact that the supercell consumed so much water vapor in the levels of the lower and middle troposphere that there was not enough remaining water vapor to cause the air to become saturated.This led to no vapor being available to be consumed during the deposition process when the air reached the tropopause and lower stratosphere.Therefore,the freezing dehydration mechanism was found to have no relationship with the water vapor changes in the stratosphere in this modeling process.Furthermore,due to the fact that the ice particle sublimation mass(rate) was much less than the mass(rate) of water vapor change in the lower stratosphere,the sublimation hydration mechanism was determined to be minor.The reason for these finding was that the majority of the ice crystals had been converted into snowflakes in the upper portion of the supercell.Therefore,the majority of the ice particles which had been transported into the stratosphere were in the form of snowflakes.Since snowflakes have greater terminal velocity than ice crystals,the snowflakes ascended to the stratosphere from the troposphere with more difficulty than the ice crystals.Also,the snowflakes tended to descend faster than the ice crystals,which led to fewer ice particles,as well shorter existing times of the ice particles in the lower stratosphere.As a result,the subsequent sublimation processes in the lower stratosphere generated much less water vapor.Nevertheless,there was an obvious stratosphere-troposphere exchange of water vapor observed in the region where the translational kinetic energy was larger than in the surrounding area.On the other hand,the gravity wave break was not observed in the one-minute interval output,and therefore the possibility existed of no transportation of water vapor into the lower stratosphere.It was also considered to be possible that the turbulent transportation mechanism played a primary role in the transportation of the water vapor into the stratosphere via the supercell,and the magnitude of the turbulent transportation water vapor flux density was determined to be approximately 10^-9 kg·m^-2·s^-1 in this simulation.

Abstract:In this research study,the microphysical responses of stratiform clouds on April 18,2009 were studied by analyzing the observational data of three aircrafts.On the basis of distinguishing between the natural and seeded clouds,the observations from radar,satellite,and ground-based sites,together with MICAPS reanalysis,were used.The results indicated that the upper part of the cloud at approximately 4,800 m(1,700 m under the cloud top,and 3,000 m above the cloud base) was the strongest part,with the majority of the subcooled water accumulated within this section.It was observed that the embedded cumulus section maintained a temperature measuring 2℃ lower than that of the stratus cloud at the same altitude.Even though the liquid water concentration in the cumulus section were observed to vary greatly,the maximum value of the liquid water concentration was determined to be 1.5 g/m³,with a standard deviation of 0.4 g/m³.The maximum liquid water concentration,and its standard deviation in the stratus area,were 0.6 and 0.15 g/m³,respectively.The peak diameters of the cloud droplet spectra in the cumulus and stratus sections were determined to be 25 and 15 μm,respectively.Also,differences existed in the cloud drop concentrations,with 10² cm^-3 in the cumulus section,and 10¹ cm^-3 in the stratus section.
In regard to the seeded clouds,the observations revealed a response in the cumulus section at 4,800 m.The artificial AgI which was released in the cloud caused a dissipation in the top portion of the cloud,which resulted in a decrease in the proportion of the cloud's area from 71% to 13%.The liquid water in the cloud was consumed,and tended to fit an equal distribution.Then,at 10 and 20 minutes after the AgI release,the maximum cloud liquid water concentrations were observed to drop to 1.0 and 1.5 g/m³,respectively,and their corresponding standard deviationswere 0.3 and 0.15 g/m³,respectively.Also,the riming and cohering effects were found to be the major microphysics processes in the ice phase.The cloud droplet spectrum was first narrowed,and then widened,due to the H-M ice crystal proliferation mechanism.It was found that the cloud became vigorous below the top section due to the catalytic process which occurred in that region.Furthermore,within 10 minutes,it was observed that the cloud's range increased significantly from top to bottom,with the cloud droplets and ice crystals enlarging horizontally to double their original size.

Abstract:The previous studies regarding types of temperature changes have been mainly related to the concept of the coefficient of similarity.During the computing of the coefficients of similarity in the past,the area weight of all the sites was thought to be equal,and the information obtained from the sites was believed to be uniformly distributed in the space domain.The grid and site climate data were found to generally meet the requirements of temporal uniformity.However,the data were notable to strictly meet the requirements of spatial uniformity (for example,the area represented by a single grid or site was different),which may have led to distortions in the statistical results involving the spatial regions.Therefore,in order to analyze the temperature variation similarities,the key was to process the network density in homogeneity.In this study,based on a scheme of network homogeneity correction proposed by Wang Panxing,a new calculation method for the coefficient of similarity was presented.This new method considered the weight of each area of a site.Therefore,the coefficients of similarity were determined to be more accurate.
Two schemes were used in this study to choose similar cases.The first scheme was as follows:1)Two fields were found to be similar before the correction.However,they were observed to be not similar or reversed after the correction.Alternatively,two fields were not similar or opposite before the correction,but were found to be similar after the correction;2)The absolute values of the differences between the coefficients of similarity before and after the correction tended to be the maximum.
The second scheme used in this study was as follows:1)The first condition was the same as 1)in the first scheme;2)The coefficients of similarity before and after the correction tended to be the maximum.
Also,according to the aforementioned two schemes for selecting similar cases which were utilized in this study,the inter-annual similarity features of the air temperature anomalies at 160 stations in China during the four seasons ranging from 1951 to 2010 were examined.The results showed the following:1)According to the first scheme,if a pair of air temperature anomalous fields were more similar in the eastern region,and less similar in the western part,then the adjusted national similarity coefficient was observed to be significantly reduced.Otherwise,if a pair of air temperature anomaly deviation fields were less similar in the eastern region,and more similar in the western part,then the adjusted national similarity coefficient was found to be significantly increased;2)According to the second scheme,if the coefficient of similarity of a pair of air temperature anomalous fields was significantly larger before the correction,then the pair of fields were observed to be very similar in the eastern region,and the adjusted national coefficient of similarity was significantly reduced.Otherwise,if the coefficient of similarity of a pair of air temperature anomalous fields was significantly larger after the correction,then these two anomalous fields were definitely very similar in the western region,and the adjusted national similarity coefficient was observed to be significantly increased.The two schemes showed that the network homogeneity adjustments led to the weight of the eastern region becoming reduced,and the weight of the western region increasing in the national average,which more objectively reflected the similarity degree of the inter-annual air temperature anomaly.

Abstract:A total solar radiation model based on the support vector machine(SVM) method is studied for calculating solar radiation in Nanjing.With a solid the oretical foundation,the SVM method is a kind of novel small sample learning method,which can be employed to deal with the problems of highly nonlinear classification and regression.Based on the daily total solar radiation and sunshine duration data in Nanjing in 1981,1996 and 2001,a model of total solar radiation estimation is established by using the SVM method,which is used to forecast total solar radiation in 1982,1997 and 2002.The prediction accuracy of total solar radiation using the SVM method is compared with that obtained by the linear climatological method.Furthermore,the above results are compared with the observed values.According to the simulated results of total solar radiation in Nanjing by using the linear and SVM methods,it can be clearly seen that the errors of total solar radiation predicted by the linear method is relatively larger,and the simulation accuracy changes significantly with different seasons.Nevertheless,the observed values of total solar radiation and the simulated values by the SVM method in Nanjing are basically consistent,and the simulation accuracy of total solar radiation by the SVM method is higher all the year round.Scatter plots of observed and simulated total solar radiation based on the linear method in 1982,1997 and 2002 indicate that when total solar radiation is less than 10 MJ·m^-2·d^-1,the scattered points of prediction values are dispersed.Especially,when the observed values of total solar radiation are less than 5 MJ·m^-2·d^-1,the scattered points on both sides of the fitted line are uneven and the errors are larger.The determination coefficients(R²)between simulated and observed values based on the 1:1 line for total solar radiation based on the linear method in 1982,1997 and 2002 are 0.800,0.859 and 0.838,respectively,and there is significant correlation.On the other hand,the scatter plots of observed and simulated total solar radiation in 1982,1997 and 2002 based on the SVM method show that the scattered points of prediction values are relatively concentrated.The R² between simulated and observed values based on the 1:1 line for total solar radiation based on the SVM method in 1982,1997 and 2002 are 0.894,0.938 and 0.936,respectively,and the correlation is more significant than that obtained by the linear method.The root mean squared error(RMSE) between the simulated and observed values for total solar radiation based on the linear method in 1982,1997 and 2002 are 3.250,2.649,2.925 MJ·m^-2·d^-1,respectively.Based on the SVM method,RMSE of total solar radiation in 1982,1997 and 2002 are 2.353,1.726 and 1.804 MJ·m^-2·d^-1,respectively,which are less than those obtained by the linear method.Total solar radiation calculated by the SVM method can accurately reflect variation of solar radiation in Nanjing,so the method is more suitable for the calculation of actual solar radiation

Abstract:When the dual polarization radar detects the small spheroids,it transmits single polarized waves and receives the horizontal and vertical polarization.If the rotary axes of the particles are assumed in a certain orientation,the radar meteorological equations of Z_vh and Z_hv must be established firstly,and these corresponding radar reflectivity factors are redefined.This paper derives the equations of Z_vh,Z_hv and R_{LD_vh} or R_{LD_hv}.The changes of LDR are simulated when the small spheroids have the size distribution of Gamma and their rotary axes are uniformly oriented in space.