Abstract:Wind shear in the atmosphere is a serious threat to the safety of aircraft,especially the low-level wind shear which is an important factor affecting the aircraft taking off and landing.By using the Doppler radar velocity data to calculate the one-dimension tangential,one-dimensional radial and two-dimension composite shear,accurately judging the dangerous area of wind shear could provide timely warning for flight,taking off and landing.In this study,as the wind shear automatic identification product on the principal user processor(PUP) for Doppler radar applications has the shortcomings such as weak edge recognition and larger location errors,according to Doppler radar velocity distributions and taking advantage of least square fitting method,"fitting window" suitable for airborne radar parameters are chosen,and the several cases have been identified and analyzed.For the performance in wind shear's identification,location and edge discerning,the least square method could provide better reference of wind shear and warnings than PUP's identification products.

Abstract:Based on the data of two anemometer towers located on Jiangsu coastal land and one on Fujian sea surface,the daily variation and profile features of wind velocity and turbulence intensity are analyzed,and the differences of wind features resulted by two different underlying surfaces are discussed.Results show that the daily maximum wind speed in coastal land occurrs later than that in inland,but the minimum wind occurrs nearly at the same time.The phase of daily variation of wind velocity delays along with altitude and the daily swing grows down.Wind speed of 70 m-height at night is bigger than that in daytime in winter,which is opposite to that of 10 m-height,showing that the height of transition layer in winter is lower than that in summer.The differences of daily variation phase of wind velocity are tiny among different altitudes over sea.Both exponential law and logarithm law can fit wind profiles of two different underlying surfaces.The law of wind profile exponent over coastal land shows that the exponent of group of wind from coast is greater than that of group of wind toward coast,and the exponent in winter is bigger than that in summer.The law of wind profile exponent over sea shows that the exponent of group of wind toward coast is bigger than that of group of wind from coast,and the exponent in summer is bigger than that in winter.

Abstract:The spatial and temporal variations of urban heat islands(UHI) over the Yangtze River Delta region have been analyzed by using MODIS(MODerate-resolution Imaging Spectroradiometer) daytime land surface temperature(T_s),MODIS land cover types and DMSP/OLS nighttime light imagery.Results indicate that the UHI effect over the Yangtze River Delta has strong seasonal variations.The UHI effect observed from the daytime T_s is the most significant in spring and summer,weaker in autumn,and the weakest in winter.Since 2001,the summer heat island areas over the Yangtze River Delta region have increased rapidly,among them growth rate of strong heat island area is the largest,leading to significant decreases of the transition region.The area of strong heat island index has been increased dramatically,especially over the Suzhou—Wuxi—Changzhou city clusters,which is connecting the UHI over Shanghai.This expanding UHI is extended along the costal line to Hangzhou and nearby cities,which is forming a giant heat island.Further studies show that the T_s has the largest increase over suburban region where the nightlight has increased most in the past decade.Over the centers of cities,the nightlight has small changes and the T_s has small change as well.There is a good spatial correlation between the T_s and the nightligh.This suggests that the human activity(urbanization) is highly responsible for the local climate change.

Abstract:Using the observational sea surface temperature(SST) data,the interannual variation of winter North Pacific Oscillation(NPO) is simulated by the National Center for Atmospheric Research(NCAR) Community Atmosphere Model Version 5(CAM5) with or without the inclusion of wind gustiness effect in the parameterization scheme of air-sea turbulent heat fluxes.Results show that,with the inclusion of wind gustiness effect,the interannaul variation of winter NPO can be reasonably reproduced by the model,and the correlation coefficient between 1979—1999 observed and simulated NPO is increased from 0.09 to 0.57.The SST anomaly in the eastern tropical Pacific plays an important role on the interannual variation of winter NPO,by influencing the air-sea turbulent heat fluxes.By considering the wind gustiness effect in the parameterization scheme of air-sea turbulent heat fluxes in CAM5,the simulating capability of interannual variation of sea surface turbulent heat fluxes in the eastern tropical Pacific is significantly improved,leading to the simulations of interannual variation of winter NPO be improved significantly.

Abstract:Threshold value of extreme precipitation of each station was confirmed through the percentile method based on the daily precipitation in Shandong Province from 1971 to 1999.Based on the threshold value,the 39 extreme precipitation events in Shandong Province from 2000 to 2009 were classified to five conceptual models,including upper trough,subtropical high periphery,shear line,cyclone and tropical cyclone types.Results show that the heavy rain area of the shear line,cyclone and tropical cyclone types is often larger,and that of the upper trough and subtropical high periphery types is generally scattered.There is low level jet in all five types,and the heavy rain area generally lies between 700 hPa and 850 hPa shear lines(or trough lines),at the wind speed convergence on the left side of low level jet.There is cold air in the upper trough type,the subtropical peripheral type and the shear line type 1,and the heavy rain area is located in front of 850 hPa cold temperature trough.For the five types,the mechanisms of extreme precipitation are different,and the configurations between heavy rain area and θ_se are not same.

Abstract:Based on the NCEP/NCAR reanalysis data,using the methods of 31-point band-pass digital filter,linear correlation and composite analysis,this paper studies interannual variations of the western and eastern intensity index(WI and EI) of North Pacific storm track in winter from 1961/1962 to 2010/2011,defines interannual typical patterns of the storm track,and further discusses their relationships with 500 hPa geopotential height and sea level pressure(SLP) fields over Northern Hemisphere.Results show that:(1)Winter North Pacific storm track is characterized by a single maximum region in the climatological mean and two maximum regions of both mean square error distribution and climatological frequency concentration areas of maximum point at each year.(2)Interannual variations of WI and EI are partially independent,and winter North Pacific storm track can be further defined as two typical patterns(single-center pattern and double-center pattern).(3)The correlation distribution of WI(EI) with 500 hPa geopotential height field is analogous to WP(PNA) teleconnection pattern.When the single-center pattern storm track is strong,the polar vortex expands southward and the three average troughs deepen.When the double-center pattern storm track exists,the polar vortex is significantly westward.(4)The correlation distribution of WI(EI) with SLP field is analogous to NPO(NAO) teleconnection pattern.When the single-center pattern storm track is strong(week),SLP anomaly field presents a positive (negative) phase of AO teleconnection pattern.

Abstract:Based on NCEP/NCAR daily reanalysis data and the northeast cold vortex(NECV) calendar from Meteorological Research Institute of Jilin province,this paper analyzes the influence of NECV on North Pacific storm track in winter of 1951/1952—2008/2009.Results show that:1)There is a significantly negative relationship between the change in days of NECV and the intensity of North Pacific storm track in winter,i.e.,the more(less) days of NECV appearance,the weaker(stronger) the storm track over North Pacific will be.2)The wavelet cross spectrum analysis shows that the above relationship is most prominent on the quasi-three-year period.3)In the winter of more NECV years,the low level temperature is falling from East Asia to North Pacific,and the major lower level cooling is located in the upper-stream of both subtropical jet and storm track,and between them latitudinally,which may induce a reverse effect on the jet and track,i.e.,a more southward,stronger and narrower jet because of the enhanced baroclinicity there,but a weaker storm track since the reduced baroclinicity and the lower level cooling in northwestern Pacific may weaken the wave seeding responsible for the eddy generation from East Asia to North Pacific;and vice versa.

Abstract:Based on the Barnes interpolation method and the hourly AWS(automatic weather station) temperature data from 00:00 BST 1 July 2011 to 23:00 BST 30 June 2012,this paper studies the space consistency quality control by Barnes interpolation method which has some applicability in Shanghai and East China.Analysis of the characteristic of representative areas shows that,on the day without precipitation,the temperature of land stations and seaside stations has significant diurnal variation characteristics and the temperature difference is minimum between 09:00 BST and 18:00 BST.In the daytime(nighttime),the temperature of land(seaside) stations is higher than that of seaside(land)stations,and the highest(lowest) temperature difference is about 0.74 ℃(0.79 ℃).Besides,the temperature difference is striking at most moment,and owes to the sunlight,wind speed and direction.Further,the AWS data are sensitive to variations of meteorological elements during weather processes and can reflect urban heat island effect.

Abstract:Based on the observational data at Zhanjiang from 31 March to 2 April 2010,microphysical characteristics and evolution of aerosol particle size distribution for a sea fog which was influenced by cold front were analyzed.The results showed that the formation and dissipation of sea fogs was closely related to wind field.The formation and development of sea fogs usually occurred in east southeast wind,while weak northeast wind was the main factor to dissipate the persistent sea fog.The variation range of fog droplet number concentration and liquid water content were 10⁰—10² cm^-3 and 0.001—0.232 g·m^-3,respectively.The mean radius was less than 10 μm and the peak radius was mostly near 1.4 μm.The fog droplet size distribution of the sea fog events was mainly of a monotonically decreasing type with the spectrum width larger than 20 μm.The fog droplet spectrum width presented abrupt broadening and rapid reducing phases during the sea fog events whereas the change in fog droplet number concentration was mainly caused by the number density variation of fog droplets with radiuses of less than 5 μm.Sea fogs exerted insignificant wet scavenging effect on aerosols.The number density of aerosol particles with diameters of less than 0.1 μm or more than 4 μm decreased dramatically during sea fogs,but quickly returned to their normal levels before the formation of sea fogs.

Abstract:By using the data observed by a laser raindrop spectrometer from August 2009 to October 2010,the microphysical characteristics and raindrop size distributions varying with time in three kinds of precipitation in Shandong were analyzed.According to different precipitation clouds,the values of microphysical characteristics were compared.The results show that the values in convective cloud precipitation,mixed-cloud precipitation and stratiform cloud present a decreasing trend.The precipitation intensity is consistent with the density of raindrops and the maximum diameter in all three kinds of precipitation.The raindrops of diameter at less than 2 mm play the most important role in precipitation brought by stratiform cloud and mixed-cloud,while those of diameters between 1 mm and 3 mm contribute the most to the rain intensity in cumulus precipitation.The distribution of raindrop size in stratiform precipitation is very narrow,which is mainly of single-peak or double-peak;for cumulus precipitation,it has a wide spectrum with a multi-peak structure in great drops;the spectral width in mixed-cloud precipitation is between the aformentioned two.In addition,the Z-I relation formulas in the three different precipitation clouds is analyzed,which can be used in the quantitative measurement of rainfall.

Abstract:An Elman recurrent neural network model(ENN) is constructed and applied to the daily runoff forecast in the Linyi sub-catchment of upper Yishu river basin in this paper.In order to further evaluate the performance of ENN,land surface hydrological model TOPX is applied as a comparison at the same time in the study region.Based on analysis indexes such as Nash-Sutcliffe coefficient,correlation coefficient,mean relative error and root mean relative square error,the results of daily runoff and flooding processes indicated that ENN presents high accuracy in hydrological simulations on the rainfall-runoff dynamic process,the peak flow and peak occurrence time.It is feasible to take it as a promising and efficient method to simulate the daily runoff.

Abstract:The general linear model(GLM) is a statistical model of hydrological forecast post-processing.It can reduce biases in raw simulations,preserve skills of raw forecasts,and produce reliable hydrologic ensemble forecasts.In this paper,GLM is used to adjust the daily hydrograph simulations,which are taken from the international model parameter estimation experiment database,and the adjusted results are compared with the observations in order to test GLM's capability of reducing biases.Results show that the continuous ranked probability scores of the hydrological ensemble forecasts are all below 0.5,proving that the ensemble forecasts are reliable.The experimental indexes of the adjusted simulations,such as mean,standard deviation,root-mean-square error,are more approximate to the observations than those of the raw simulations.Even to the simulations which contain fewer biases,GLM still can improve them.

Abstract:Combination of remote sensing data with crop model is one of important contents and development trends of agricultural information technology study,which can be used to solve some problems that cannot be solved individually by using remote sensing data or crop model.In order to develop the crop growth process simulation and the yield prediction in a large scope,the WOFOST crop model is revised and verified based on the field test data,in such a way that the revised model can be used to simulate winter wheat growth in Xinxiang County of Henan Province.Based on the actual wheat growth,the winter wheat growth in Xinxiang County during 2002—2003 is divided three cases and simulated by the model.The growth of winter wheat in each pixel is determined by contrasting two kinds of LAI(leaf area index), i.e. one retrieved from the Landsat-7 ETM⁺ data in the whole growth period,another simulated by the WOFOST model,so that the winter wheat growth can be simulated in the pixel level by the WOFOST model.Comparison is made between the results of the method used in this paper and the statistic data of Xinxiang County.The similar outcome verifies the technical feasibility of the method.

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Abstract:Based on the chaotic characteristics of the atmosphere,it has become a tendency that the deterministic forecast gradually turns to be the probabilistic forecast with uncertainty.This paper systematically reviews the development background of probabilistic weather forecast,and introduces the concept,and advances of the probabilistic forecast research at home and abroad.Reviews are primarily focused on two kinds of multimodel ensemble probabilistic forecast methods,namely the Bayesian model averaging(BMA) and the multivariate Gaussian ensemble kernel dressing(GEKD).Cases of the BMA and GEKD probabilistic forecasts are shown.The deviation of the BMA probabilistic forecast becomes smaller,and it reduces the uncertainty of the forecast.Hence,the forecast is close to the real value of the atmosphere.As another multimodel ensemble probabilistic forecast approach,the GEKD probabilistic hindcast of the mean value of surface temperature anomaly and its trend basically coincides with the observed data.By using the GEKD approach,a multimodel ensemble probabilistic prediction model is established to predict the interdecadal variability of surface air temperature and to extract interdecadal climate variation features.It is of important application value for the interdecadal variability prediction over the East Asian monsoon region.