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31 August 2018, Volume 34 Issue 4 Previous Issue    Next Issue

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Mesoscale characteristics of a short-time heavy rainfall under the background of the Central Asian Vortex in the middle Tianshan of Xinjiang province WAN Yu;CAO Xing;YANG Lian-mei 2018, 34 (4):  1-10.  doi: 10.3969/j.issn.1673-503X.2018.04.001 Abstract ( 206 )   PDF (5407KB) ( 321 )   Save Using the data from conventional and automatic weather stations, Doppler radar, satellite and wind-profiler radar as well as the associated NCEP (National Centers for Environmental Prediction) reanalysis , we analyzed the convectie conditions and mesoscale characteristics of a short-time heavy rainfall in the middle Tianshan of Xinjiang province on June 27-28, 2015. The mesoscale diagnostic analysis under the background of the central Asian vortex was carried out to provide a reference for the forecasters. The results indicate that this strong convective weather process is caused by the interaction of the northeast to southwest anticyclonic shear in front of the central Asian vortex and the deep warm-wet flow coming from southwest. The direct impact systems to this process are convective instability, including the dynamic lifting condition, shear line in the lower troposphere, surface mesoscale convergence line and the cyclone type convergence center. The convergence of water vapor at the bottom of the central Asian vortex along west and that in front of the central Asian vortex along southwest attributes a favorable vapor condition to this process. Analysis shows that the abrupt variation of GPS-PWV (Global Position System, Precipitable water vapor) and vertical variation of  wind from wind-profiler radar have a good correspondence to the beginning, strengthening and ending of the precipitation. Satellite IR imagery shows that the short-time strong rainfall occurs at the maximum gradient area of the  brightness temperature of convective clouds and is identified by the low centroid and the high-efficiency precipitation echoes. The precipitation intensity is positively correlated with the height of echo top. This study provides a quantitative index for improving the forecast accuracy of short-time strong rainfall. Related Articles | Metrics

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Application of Frequency-Matching method to ECMWF ensemble statistic fusing prediction products in the Haihe River basin XU Shu;WEI Ying-hua;XIONG Ming-ming;WEI Lin 2018, 34 (4):  11-17.  doi: 10.3969/j.issn.1673-503X.2018.04.002 Abstract ( 194 )   PDF (1317KB) ( 299 )   Save Based on the bias characteristics of the ECMWF (European Centre for Medium-range Weather Forecasts) ensemble statistic fusing prediction products in the Haihe River basin, the frequency matching method was used to correct the precipitation bias. The performance before and after the correction was examined. Using the results from four months（May-August, 2016）experiment, we demonstrate t that the positive biases in the precipitation level and range from the original products can  be significantly improved using the improved fusion products. The average intensity of the modified precipitation forecasts is closer to observations. The longer the valid forecast time, the greater the precipitation level, and the bigger the prediction bias , the better the improvement effect. To some extent, the scores of TS (threat score) and Bias of the improved fusion products are improved, especially for the light rain, rainstorm and the heavy rain cases. It eliminates the large false areas and reduces  the false-alarm  rates  significantly.  However, the missing- rates are slightly increased. Related Articles | Metrics

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Quantitative precipitation inversion algorithm based on the multi-radar mosaic I: dynamic Z-I relationships JI Yong-ming1 JIANG Da-kai2 CHEN Chuan-lei;REN Zhi-jie;MENG Ying;CAI Kui-zhi; HU Peng-yu;ZHANG Shuo 2018, 34 (4):  18-25.  doi: 10.3969/j.issn.1673-503X.2018.04.003 Abstract ( 196 )   PDF (1522KB) ( 498 )   Save Using the Doppler multi-radar mosaic data and surface precipitation data of encryption automatic stations in Liaoning province, the local dynamic Z-I relationships were established based on the optimization method to get the quantitative precipitation retrieval data with a real-time high spatiotemporal resolution. The method is used to retrieve the precipitation fields produced by typhoon " Meari" in 2011 and "Damrey" in 2012. The results show that the quantitative precipitation retrieval method can reproduce the main spatial distribution characteristics of the precipitation. . However, there is a large bias  in the strong precipitation center. In general, the retrieval  ability of quantitative precipitation for the local dynamic Z-I method is better than the fixed Z-I method. There is still systematic bias in the inversion data, i.e., overestimating the light rain and underestimating the heavy rain. For the heavy precipitation above 20.0 mm•h-1, the average error is greater than -10.0 mm and the average relative error is greater than 70.0%. Further analysis shows that the differences in the proportion of different magnitudes of precipitation and the differences in the regional climate conditions are the two main reasons for the precipitation inversion error. This knowledge provides a way for the improvement of radar quantitative precipitation inversion in the future. Related Articles | Metrics

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Adaptability evaluation of the CLIGEN model generated precipitation in Shenyang region SONG Xiao-wei; LI Lin-lin;ZHANG Lin; LIU Qing;LI Shi; MU Chen-ying;ZHANG Jing 2018, 34 (4):  26-35.  doi: 10.3969/j.issn.1673-503X.2018.04.004 Abstract ( 174 )   PDF (1684KB) ( 220 )   Save The CLIGEN (Climate GENerator) weather generator is a part of the WEPP (Water Erosion Prediction Project) soil erosion model. It is mainly used to provide the daily meteorological data for a long sequence, thus to solve the problems of the shortage of actual metrological sequence or missing values. However, the adaptation of the CLIGEN model in Shenyang region of Northeast China needs to  be tested. In this paper, using daily station weather data in Shenyang from 1981 to 2001, the daily precipitation data were generated by the CLIGEN model. The daily, monthly, annual, and annual maximum daily precipitation of simulated and measured values were compared. The applicability of the model was evaluated using mean, standard deviation, skewness and kurtosis statistic data. The results show that the CLIGEN model generates  better simulation results for daily, monthly and annual precipitation amounts, The MARE (Mean Absolute Relative Error) is 2.1%,1.3%, and 3.3%, respectively. However, the simulation accuracy of annual maximum precipitation amount is slightly worse. As for the extreme values in precipitation, the simulation results of daily and annual maximum precipitation amounts are not good. The maximum error of daily and annual maximum precipitation amounts reaches to -27.2% and 18.3%, respectively. The CLIGEN model can better simulate the monthly and annual precipitation. Based on t, F and K-S tests, it indicates that only Kangping station reaches the very significant level in the daily and annual maximum daily precipitation amounts. In general, the CLIGEN model can better simulate the statistical characteristics of precipitation in Shenyang region. Related Articles | Metrics

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Staged spatial consistency check method in hourly station pressure YAN Qiao-qiao;WANG Hai-jun ;YAN Jing 2018, 34 (4):  36-44.  doi: 10.3969/j.issn.1673-503X.2018.04.005 Abstract ( 211 )   PDF (1375KB) ( 322 )   Save Based on the correlative relationship between  pressure and altitude, the station pressure is corrected to the median height of pressure altitudes, and then a staged spatial consistency check method for hourly station pressure was proposed, including the coarse grain quality and fine grain quality controls. Taking sea level pressure as a reference element, the rationality and applicability were discussed. The median pressure was applied to the station pressure spatial consistency check by analyzing the spatial variability of pressure. The artificial implantation error was introduced to make a quantitative analysis for the error detecting ability. This method was evaluated using the data from 2420 national automatic weather stations in China in 2015. The results show that the median pressure can be used to carry out the station pressure spatial consistency check. It is more stable and its spatial variability is less than the sea level pressure, especially in high altitude areas. However, it is more sensitive to the small error. The error detection rate of median pressure is greater than that of the sea level pressure when the different implantation errors are applied in different seasons. The smaller the error is, the higher the growth rate is. When the error detection rate is above 90%, the implantation error is 2.5 hPa in different seasons. The maximum value appears in summer with 98%. The staged quality control strategy effectively reduces the time complexity of the algorithm. The execution time meets the requirements of real-time operation. Meanwhile, this method can effectively detect the error data. The detection rate is about 0.01%. Related Articles | Metrics

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Characteristic and formation analysis of a persistent high temperature and drought event in Hunan province during 2013 summer ZHANG Jian-ming;DUAN Li-jie 2018, 34 (4):  45-51.  doi: 10.3969/j.issn.1673-503X.2018.04.006 Abstract ( 236 )   PDF (2858KB) ( 235 )   Save Based on observational data of daily temperature and precipitation at 97 meteorological stations in Hunan province and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, the characteristics and formation of a persistent high temperature and drought events during summer season in 2013 in Hunan province were analyzed. The results showed that the mean number of days with high temperature in Hunan province is 44 d, and these high temperature days occur mostly in the periods of June 15-25, from June 29 to August 18, and August 21-30. The numbers of days with high temperature at 32 stations in 2013 are larger than the historical records in the same period. The large-scale meteorological drought in Hunan province begins in the mid-June of 2013, and the area of severe and even heavier drought is over half area of the province from July 28 to August 20. The Subtropical High over the western Pacific that is abnormally and persistently strong and locates westward controls the Jiangnan region, which is the most important and direct influencing factor  of this high temperature and drought event in Hunan province. In the upper troposphere, the South Asian High is persistently strong and moves eastward or northward, which is favorable to the maintenance of the western Pacific Subtropical High. This leads to the continuous subsidence motions of air flows over the Jiangnan region and the significant suppression of convective activity. Meanwhile, the divergence center of water vapor flux is located at the western of Jiangnan region and the northern part of South China, which is unfavorable to the accumulation of water vapor. Related Articles | Metrics

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Climate characteristic and prediction evaluation of precipitation in main flood season in Heilongjiang province Wang Bo; Li Yong-sheng;Wang Ying;Ban Jin 2018, 34 (4):  52-58.  doi: 10.3969/j.issn.1673-503X.2018.04.007 Abstract ( 231 )   PDF (1627KB) ( 249 )   Save Base on daily precipitation observational data at 62 meteorological stations in Heilongjiang province during 1961-2016 and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, the characteristics of precipitation climate and atmospheric circulation from late July to early August in main flood seasons were analyzed. Precipitation and circulation in Heilongjiang province during main flood seasons were evaluated using the simulated results with different starting time from the Dynamic Extended Range Forecast Operational System 2.0 (DERF2.0) model. The results showed that the precipitation during the main flood season accounts for 25%-35% of the cumulative precipitation in summer, which is the major period of summer precipitation in Heilongjiang province. In the years with large precipitation, a wave train with the “+ - +” pattern in the east-west direction exists at 500 hPa and its center is located at the western region of the Northeast China. Meanwhile, cyclones are observed in the wind field at 850 hPa. The annual mean Ps score for the precipitation in the main flood season is about 60 when the starting time of the DERF2.0 simulation is 10 d and 5 d ahead, and the score reaches 70 for 1 d ahead. When the starting time of the DERF2.0 simulation is 1 d ahead, the annual mean anomaly correlation coefficient (ACC) for circulation salient region at 500 hPa is 0.58, and that for zonal wind at 850 hPa in the southern region and in the northern region of Heilongjiang province are 0.48 and 0.52, respectively. The DERF2.0 model can predict precipitation and circulation during the main flood season in Heilongjiang province to some extent, and the prediction skills improves  significantly as approaching the starting time. Related Articles | Metrics

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Effect of meteorological parameters on ozone and its precursors in the southwest urban area of Xi’an LI Shun-ji;LI Hong;CHEN Miao;CAO Ze-lei;HUANG Yu-guang; LI Shu 2018, 34 (4):  59-67.  doi: 10.3969/j.issn.1673-503X.2018.04.008 Abstract ( 198 )   PDF (839KB) ( 424 )   Save  Based on the observational mass concentrations of surface ozone and its precursors (NO, NO2, and CO) in Xi’an, the temporal variation of ozone pollution was analyzed, and the correlation analysis and fitting equations between ozone and some meteorological parameters were carried out. The results showed that the highest ozone concentration occurs in summer due to the effect of local photochemical reaction of ozone, and the number of pollution days caused by O3-8h accounts for 1/3 of the total number of pollution days. In winter, the photochemical reaction of ozone becomes weak, but the emissions of its precursors increase, which results to the largest NO, NO2, and CO concentrations. Diurnal variation of ozone concentrations is characterized by one peak around 16:00 and a low level at night, while the concentrations of NO, NO2, and CO are lower at daytime and higher at  the night, showing two peaks for their diurnal variations. Ozone has a positive correlation with temperature and wind speed and a negative correlation with relative humidity. The concentrations of NO, NO2, and CO have a negative correlation with wind speed. Under the control of the northeasterly, northerly, and easterly flows, ozone concentration usually increase due to the pollutant transport from the upwind direction. The fitting degree of ozone mass concentration and meteorological parameters in summer is high, which means the routine meteorological parameters can be used to predict the evolution of ozone concentration.  Related Articles | Metrics

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Study on forecast method of air quality in Shenyang based on meteorological conditions LU Zhong-yan; WANG Yang-feng;JIANG Da-kai;TENG Fang-da;DING Zhao-min;TIAN Li 2018, 34 (4):  68-74.  doi: 10.3969/j.issn.1673-503X.2018.04.009 Abstract ( 215 )   PDF (1701KB) ( 242 )   Save Air quality is affected by the emission of pollutant sources and meteorological conditions. In order to quantitatively evaluate the effects of meteorological conditions on air quality, a stable weather index is established using 872 groups of meteorological and environmental data in the heating seasons of 2014-2016 in Shenyang, which involved different physical parameters such as relative humidity, wind speed, inversion temperature intensity, and mixing boundary layer height, and the relationship between the index and air quality was analyzed in this study. The threshold of stable weather index (= 9.1) can identify two major causes of severe air pollution events in Shenyang. One reason is stable weather situation, and the other is pollutant transport from other regions under unstable weather conditions. The stable weather index is proved as a good indicator for air quality through analyzing the relationship between it and PM2.5 concentrations at different pollution levels. On the whole, when the stable weather index is larger than 10.4, air pollution event usually occur. With the increase in the stable weather index, air pollution tends to be heavier. Therefore, the stable weather index can be used to predict air quality from the view of meteorology. Related Articles | Metrics

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Characteristics of sand-dust events and their relationship with atmospheric circulation in spring in Northeast China YANG Xue-yan; ZHANG Li; XI Zhu-xiang; LIU Yu-xi; XU Shi-qi;ZHANG Chen-chen 2018, 34 (4):  75-83.  doi: 10.3969/j.issn.1673-503X.2018.04.010 Abstract ( 199 )   PDF (1876KB) ( 203 )   Save Based on the observational data of sand-dust events at 72 meteorological stations and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data in Northeast China from 1961 to 2016, the spatiotemporal characteristics, climatic trends and abrupt change characteristics of sand-dust events in spring over Northeast China were analyzed, and the effect of atmospheric circulation on frequency of sand-dust events was investigated. The results showed that the number of  sand-dust events is greater  in the western region of northeast China than the eastern region and in plain areas than  mountainous area. The sand- dust events, blowing sand events, sandstorm events, and floating dust events in springs from 1961 to 2016 in Northeast China decrease obviously. The number of sand-dust days change abruptly around 1985. After 1985, the mean number of sand-dust days  is 3 d less than before. Sand-dust events in the Northeast China occur more frequently for the following conditions: firstly, when the geopotential height anomalies at 500 hPa abovwe the Baikal Lake and most parts of Northeast China are negative and those nearby the Balkhash Lake are positive, secondly, the occupation  area of Siberian High is larger and its location shifts eastward, and thirdly, the air pressure in the Northwest China and North China is lower than the normal conditions. However, sand-dust events in the Northeast China occur less frequently when the geopotential height anomalies at the Baikal Lake and in most parts of mainland in China are positive with the center of positive anomaly area near the Baikal Lake, the surface area of the Siberian High is smaller and its location shits  westward, and the air pressure in the most northern regions of China is higher than normal. The reduction of the polar vortex area in the northern hemisphere and in Asia and the decrease in polar vortex intensity in the past 56 years is one of the reasons for the decrease in sand-dust events during spring in Northeast China. Related Articles | Metrics

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Study on surface solar radiation over Xinjiang Uygur Autonomous Region based on surface observations and the GEWEX-SRB retrieved from satellite ZHOU Dai-yi; YANG Hong-hai;QIN Rong;CHEN Yong-hang; XIN Yu 2018, 34 (4):  84-91.  doi: 10.3969/j.issn.1673-503X.2018.04.011 Abstract ( 194 )   PDF (1736KB) ( 185 )   Save Based on the long-term data products of Global Energy and Water Exchanges-Surface Radiation Budget (GEWEX-SRB) released by the National Aeronautics and Space Administration/World Climate Research Program (NASA/WCRP) and the surface radiation dataset obtained from China Meteorological Administration (CMA), the surface downward solar radiation irradiance and the surface downward daily radiant exposure over the Xingjiang Uygur Autonomous Region from 1984 to 2007 were obtained to examine  the accuracy of the satellite dataand further investigate the spatiotemporal characteristics of the surface solar radiation in this region. It showed that the solar radiation retrieved by the GEWEX-SRB program is about 10%-30% larger than the observational values, but the satellite results and the observations of solar radiation show similar spatiotemporal characteristics. For the spatial distribution, the surface solar radiation in Xiangjiang Uygur Autonomous Region exhibits meridional and zonal  distribution, which means that the solar radiation decreases gradually from the northwest to the southeast. In terms of the temporal variation, the solar radiation is the highest in summer, followed subsequently by spring, autumn, and winter. The meridional distribution of the solar radiation in spring turns to a zonal distribution in winter. The change range of the solar radiation is the largest in summer. The  variation of  time slope of solar radiation for many years is the largest in spring and the least in winter. The monthly variation of solar radiation shows a normal distribution. Related Articles | Metrics

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Spatio-temporal change characteristics of heat resources in the southwest of Shandong province during 1961-2015 LI Rui-ying;REN chong-yong ;Zhang-ting 2018, 34 (4):  92-97.  doi: 10.3969/j.issn.1673-503X.2018.04.012 Abstract ( 180 )   PDF (1475KB) ( 213 )   Save ased on the temperature and measured meteorological data during the frost-free period at the 9 meteorological stations in southwestern Shandong from 1961 to 2015, the spatio-temporal change characteristics of heat resources during the period Ι (1961-1990）and the period Π（1991-2015）were analyzed using a linear regression method, Mann-Kendall break detector and independent research drawing software (Eqlds 2015). The results show that the active accumulated temperature ≥0 ℃,≥5 ℃ and ≥10 ℃ all show significant increasing trend（p<0.01）with the climate tendency rate of 66.4 ℃•d /10 a, 54.3 ℃•d /10 a and 88.6 ℃•d /10 a from 1961 to 2015, respectively. The duration of the frost-free period is between 286 d and 304 d and shows an increasing trend with a rate of 1.0 d /10 a. The annual average temperature and accumulated temperature all decrease with increase of latitude  and are higher in southeastern counties such as Caoxian, Chengwu and Shanxian county and are lower in northern counties like Juancheng and Yuncheng county. The frost-free period has no significant linear relationship with altitude and its change shows a certain regional characteristic. The heat resources occur abrupt climatic change in the 1990s and then significantly increase. In addition, the active accumulated temperature and the frost-free period during the period Π are 169.4-301.2 ℃•d higher and 3 d longer than those during the period Ι, respectively. As a result, the heat resources of period Π are higher than those of period Ι. Related Articles | Metrics

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Research on the tempo-spatial characteristics of road damage induced by precipitation WANG Zhi;TIAN Hua;DI Jing-yue;XU Feng-wen 2018, 34 (4):  98-104.  doi: 10.3969/j.issn.1673-503X.2018.04.013 Abstract ( 163 )   PDF (1113KB) ( 186 )   Save Based on the national trunk road disaster data, the tempo-spatial distribution characteristics of road damages induced by precipitation were analyzed. According to the information value method, the environmental factors (elevation, slope, relief, fault density, and lithology) and the precipitation factors (maximum hourly rain intensity, intensive rainfall frequency, and intensive rainfall duration) were analyzed and compared. The results show that the factors such as slope, intensive rainfall duration, relief, fault density and intensive rainfall frequency have the greatest effect on road damage. According to the comprehensive information value of the national trunk, road damage disaster risk is divided into five grades. It is tested that the risk classification can express the potential spatial distribution of the disaster. The study can supply a reference to road damage prevention, risk forecasting and road construction. Related Articles | Metrics

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Spatial and temporal variation characteristics of the four seasons in  Jilin province during 1961-2016 YU Xiu-jing; HU Jing-biao;ZHANG Chen-chen;LI Dong-liang 2018, 34 (4):  105-111.  doi: 10.3969/j.issn.1673-503X.2018.04.014 Abstract ( 320 )   PDF (1731KB) ( 292 )   Save  Based on the daily average temperature data from the 46 representative meteorological stations in Jilin province during 1961-2016, the start dates and durations of four seasons and their main properties and change trends were calculated according to climatic division method of seasons and analyzed, respectively. The results show that the regionally averaged values for beginning dates of each season are April 27, July 8, August 16 and October 8, respectively.   The durations for each season are 72.0 d for spring, 39.0 d for summer, 53.0 d for autmn, and 201.0 d for winter. In addition, the spatial distribution characteristics of the above-mentioned factors are obvious. The averaged beginning dates of the first half year are earlier in the west than in the east; however, those in the second half year are earlier in the east than in the west. The average duration of summer is longer in the west than in the east and vice versa for those of spring and winter, while that of autumn has little variation throughout Jilin province. Besides, there is no summer in the east of Jilin province. In the recent 56 years, the regionally averaged beginning dates of spring and summer are ahead of time for 0.7 d and 1.3 d per decade, respectively, and those of autumn and winter are postponed for 1.3 d and 1.1 d per decade. More specifically, the beginning dates of spring in the east and of winter in most parts of Jilin province change significantly. Moreover, the regionally averaged durations for spring and winter decrease with the rates of 1.0 d and 1.8 d per decade, inversely, that for summer increases with a rate of 2.8 d per decade. The duration of autumn in the west of Jilin province is shortened with a ratio of 1.3 d per decade, while that of east Jilin is prolonged with a ratio of 1.0 d per decade. It is obvious that the summer is prolonged in the western and central parts of Jilin province and east Yanbian state, and the winter in the most parts of Jilin province is shortened especially in east Jilin. Related Articles | Metrics

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Relationship between fractional vegetation and climate factors in spring over the mid-west of DPR Korea WU Gang-zhe;YAN Jin-zhe; REN Guo-yu; SUONAN Kan-zhuo 2018, 34 (4):  112-118.  doi: 10.3969/j.issn.1673-503X.2018.04.015 Abstract ( 178 )   PDF (1396KB) ( 145 )   Save  Based on the Landsat5 satellite data in 1992, 2003 and 2007 as well as temperature and precipitation data from the 13 weather stations in the mid-west of DPR Korea during 1992-2007, the variation characteristics of fractional vegetation (FV) in spring and their relationships with climate abnormality were investigated. The results show that the regionally averaged FV in the studied area increases significantly with a rate of about 17.5%. More specifically, the increasing magnitude of FV in plain area is about 20.0% higher than that in mountain area. In addition, FV has a negative correlation with the spring mean surface temperature (correlation coefficient: r = -0.43) and a positive correlation with the spring precipitation (r = 0.43). Moreover, there is a negative and positive correlation between the variations of the spring mean temperature, precipitation and FV (correlation coefficient: r = -0.53 and r = 0.79), respectively, with a very significant level (p<0.05). So, the variation of spring FV in the mid-west of DPR Korea may be mainly affected by spring mean temperature and precipitation. Related Articles | Metrics

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Spatial and temporal distribution characteristics and impact factors of the frost over Jilin province from 1961 to 2015 REN Jing-quan; GUO Chun-ming; WANG Li-wei; LI Jian-ping; LIU Yu-xi; LI Qi 2018, 34 (4):  119-125.  doi: 10.3969/j.issn.1673-503X.2018.04.016 Abstract ( 246 )   PDF (2087KB) ( 201 )   Save  Based on the frost observation data of 50 meteorological stations over Jilin Province from 1961 to 2015, the spatial and temporal distributions of the beginningfirst and ending last frost date, frost-free period and their relationships with climate change and geographical factors were analyzed using the methods of linear trend estimation, Mann-Kendall test and Morlet wavelet analysis. The results show that the beginning first and last frost date is postponed, the ending frost date occurs earlier. as well as  The frost-free period becomes are significantly longer. postponed, ahead of time and prolonged with the The climatic trend rates for the beginning and ending frost date and frost-free period are of 1.4 , -2.2 and 3.6 days per decade, respectively.  and the corresponding The number amounts of stations with delayed beginning frost date accounts for occupy 58% of the total stations, that of ahead of ending frost daya is 60% and that with longer frost-free period is 72%  percent of the total stations., respectively, in Jilin Province from 1961 to 2015. The earliest beginning frost date occurs in 1960s. The latest ending frost date is in 1970s. (latest) first (last) frost date occurs in the 1960s (1970s) and tThe shortest frost-free period  and longest frost-free periods appears in the 1970s and the the longest frost-free period happens stage during 2011-2015., respectively. In terms of the spatial distribution, the first (last) frost date and the frost-free period are gradually ahead of time (postponed) and shortened from the west to the east of Jilin. The time series of the ending last frost date and the frost-free period show occur the climatice abrupt changes in 2009 and 2000, respectively. The main cycles of the beginningfirst and the ending last frost date and the frost-free period are all about 3 years. In addition, the beginning first and ending last frost date and the frost-free period are ahead of time, postponed (ahead of time) and shortened (prolonged) with the increasing longitude and altitude (latitude), respectively. The first (last) frost date and the frost-free period is mainly affected by the climatic factors in September (May), respectively. Related Articles | Metrics

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Comparison of various meteorological statistical forecasting models-Taking causing- stroke weather forecasting as an example LIU Bo; DANG Bing; ZHANG Nan;WANG Shi-gong; YIN Ling; ZHANG Xiao-yun; LI Tan-shi;LU Zhen-hua 2018, 34 (4):  126-133.  doi: 10.3969/j.issn.1673-503X.2018.04.017 Abstract ( 177 )   PDF (480KB) ( 220 )   Save  Based on the data of stroke emergency visits from four hospitals in Beijing during 2008 to 2012, as well as the observed daily meteorological and environmental factors, meteorological and environmental predictors were selected. All the data were divided into two groups, that is, calibration set (2008-2011) and validation set (2012) . Causing-stroke weather forecasting model was constructed using four methods including Stepwise Regression Model (SRM), BP Neural Network Model, Decision Tree Model (DTM) and Generalized Additive Model (GAM). The best model for forecasting the number of stroke patients was determined by comparing the goodness of fit and forecasting accuracy of different models. The results show that the selected predictors vary are varied along with different seasons and models.  and The time series factor is the most important factorindispensable. GAM produces , SRM, and DTM methods give the best performance in at forecasting number of the high-level-stoke., SRM gives the best result for the prediction of the medium-level-stroke.  andDTM provides the best estimate for the low-level-stroke patients, respectively.. The sequence of averaged forecasting accuracy over the four seasons from of the three different models is as follows: GAM＞BP Neural Network Model＞SRM＞DTM. GAM has the highest forecasting accuracy for the number of averaged and high–level-stroke patients . For, the cerebral hemorrhagic stroke (CHS), the forecasting accuracy is 68.3% if the forecasted grade is exactly correct. For the bias grade  ≤±1difference between forecasted grade and actual grade no more than 1, the forecasting accuracy is 98%. The result indicates  reveals that GAM can basically meet the demand for medical meteorological forecasting of CHS. Related Articles | Metrics

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Responses of main physiological parameters to drought stress during the period from jointing to filling of spring maize in Northeast China ZHANG De-lai;CAI Fu;SHI Kui-qiao; YANG Yang;ZHANG Hui;ZHANG Bing-bing;YANG Lu; GAO Quan;LV Xiao 2018, 34 (4):  134-138.  doi: 10.3969/j.issn.1673-503X.2018.04.018 Abstract ( 175 )   PDF (645KB) ( 213 )   Save In order to understand the mechanism of drought stress affecting on spring maize, a field experiment was conducted by withholding water for 30 days during the period from jointing to filling. Main variables associated with photosynthesis including net photosynthetic rate(Pn), transpiration rate (Tr), stomatal conductance（Gs）, intercellular CO2 concentration(Ci) and stem flow rate (SF) as well as leaf and root water potential were observed and their response characteristics to drought were investigated. The results indicate that Gs、Pn and Ci  respond slowly to mild drought and decrease quickly when drought aggravates and reaches moderate level .except for Tr responding quickly to mild drought. Further, with drought stress aggravating, the determination factors of photosynthesis rate is changed from stomatal factor to stomatal and non-stomatal factors. After rewatering, the above mentioned parameters recover to normal level and Gs、Pn and Tr show fast compensatory increases, while Tr dose not respond sensitively to increased soil moisture. In addition, daily amount of stem flow is not affected by mild and moderate drought stress but shows a compensatory rising after rewatering. Leaf water potential responds to drought stress slower than that of root water potential which restoration ability is better than leaf water potential. Related Articles | Metrics

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Research on the method of forecasting ultraviolet intensity in China GAO Jing-jing;WU Hao;DAI Zhi-xiu;CHEN Zhong-yu;LI Wan-yu 2018, 34 (4):  139-144.  doi: 10.3969/j.issn.1673-503X.2018.04.019 Abstract ( 213 )   PDF (988KB) ( 256 )   Save  The study estimated the solar ultraviolet (UV) irradiance at noon for clear sky based on the physical mechanism of atmospheric radiation transmission. Then UV irradiance of clear sky was corrected revised using factors such as cloudiness, aerosol and etc.. Finally, daily maximum UV irradiance under of non-clear all-sky conditions was obtained and UV intensity forecasting model was constructed. Compared with the original national UV intensity grade forecasting model, forecasting accuracy of the new model is greatly improved, which makes the new model can be applied to the national operation of UV intensity forecasting. The results indicate the improved model works better under for clear- sky than under for cloudy- sky. Related Articles | Metrics