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28 February 2023, Volume 39 Issue 1 Previous Issue    Next Issue

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Analyses of atmospheric circulations and severe weather events during 2021/2022 boreal winter Wei ZHAO,Ning-fang ZHOU,Shu-nan YANG,Chun-yi XIANG 2023, 39 (1):  1-9.  doi: 10.3969/j.issn.1673-503X.2023.01.001 Abstract ( 373 )   HTML ( 32 )   PDF (5342KB) ( 121 )   Save In this paper, the main characteristics of general atmospheric circulation and severe weather events during 2021/2022 boreal winter were analyzed using China's First Generation Global Atmosphere and Land Reanalysis Search data (CMA-RA).The results show that the mean precipitation and temperature over land during 2021/2022 boreal winter are higher, and extreme and severe weather occurs frequently.The upper high atmosphere circulation in the Northern hemisphere mainly presents characteristics of "three troughs and three ridges".Negative phase of Pacific-North America (PNA) teleconnection becomes the strongest circulation in early time, then late the North Atlantic oscillation (NAO) positive phase is the most significant circulation.The change of strength and position of troughs and ridges in high-middle latitude is the immediate cause for the severe weather, such as snowstorms and tornadoes hitting many places including Europe, Western Asia, and North America.The polar vortex in the southern hemisphere is uni-polar and located towards the southern Pacific.The subtropical high is strong and stable, which causes Australia and Argentina to suffer from persistent heat waves.The tropical cyclones are abnormally active over the south Indian Ocean.In February of 2022, four tropical cyclones are made landfall and causing severe flooding and other disasters in Madagascar. Figures and Tables | References | Related Articles | Metrics

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Verification for precipitation forecasted by NWP models in Liaoning province during the summer of 2020 Zheng-hua TAN,Zhong-yan LU,Hai-feng LIN,An-qi NIE,Fang-da TENG 2023, 39 (1):  10-16.  doi: 10.3969/j.issn.1673-503X.2023.01.002 Abstract ( 233 )   HTML ( 21 )   PDF (1988KB) ( 108 )   Save Based on seven kinds of numerical weather prediction (NWP) products, the binary test and frequency distribution test methods were used to test and evaluate the 24 h precipitation forecast and the 3 h heavy precipitation forecast with more than 20 mm precipitation in Liaoning province from May to September of 2020.The results show that most NWP models have the error characteristic of excessive precipitation forecast frequency, especially the global model, which is more obvious for the excessive forecast of the weak precipitation process.The prediction effect of the numerical model is generally good for the 24 h moderate rainfall, while the global model is poor for heavy rainfall.The forecast intensity of extreme precipitation in the SHANGHAI mesoscale model is higher than the observations.The ECMWF (European Centre for Medium-Range Weather Forecasts) model has the balanced performance of different grades precipitation forecasting.It also has some ability to forecast heavy precipitation.The mesoscale model has a good forecast effect on heavy precipitation during the daytime, but the forecast effect becomes worse at 6-9 h after the initial time.The NWP models have a good forecasting effect on the large-scale heavy precipitation process and the small-scale stable heavy precipitation process, but a poor forecasting effect on the small-scale heavy precipitation process behind the subtropical high. Figures and Tables | References | Related Articles | Metrics

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Verification on the summertime Eurasian middle-high latitude ensemble forecasting circulation system Xue-yi XUN,Bao-cheng YANG,Ying-hua HU,Min ZHANG 2023, 39 (1):  17-25.  doi: 10.3969/j.issn.1673-503X.2023.01.003 Abstract ( 158 )   HTML ( 10 )   PDF (4086KB) ( 42 )   Save The European Centre for Medium-Range Weather Forecasts (ECMWF), National Center for Environmental Predictions (NCEP), and Canadian Meteorological Centre (CMC) ensemble forecasts and ERA-Interim reanalysis data were analyzed to understand the skill of the circulation system in Eurasian middle-high latitude in summer based on the anomaly correlation coefficient, root mean square error, and relative operating characteristic curve method.The results show that it captures the observed features of the best applicability for the ECMWF ensemble forecast and the worst applicability for the CMC ensemble forecast, but underestimates applicability showing a decreasing trend with increasing forecast lead time.A skillful forecast can be obtained up to 192 h for the ECMWF ensemble forecast, 180 h for the NCEP ensemble forecast, and 168 h for the CMC ensemble forecast.The ensemble-averaged forecast is more reliable than the control forecast, and the control forecast is slightly higher than the other members.For available predictive timeliness, the ensemble-averaged forecast is 12 h longer than the control forecast and 36 h longer than other members.There are obvious differences in available predictive timeliness and accuracy of the same numerical forecast model at different starting times.Although the predictive effects of the blocking high and the West Pacific subtropical high are periodic in the study period, the rate of deterioration in forecast ability slows down after 240 h in the blocking high areas, there is even an increasing trend in the Ural blocking high and the prediction effect is the best near the 300 h.The available predictive timeliness of the West Pacific subtropical high is lower than that of the blocking high, but its accuracy is obviously higher than that of the blocking high. Figures and Tables | References | Related Articles | Metrics

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Simulation and prediction of future extreme precipitation in Fujian province under SSPs scenarios Zhen-fei TANG,Ting YANG,Xiao-chen CHEN,Xin-xin LI,Xin LIN,Fen HE,Zhen-zhi WEN 2023, 39 (1):  26-36.  doi: 10.3969/j.issn.1673-503X.2023.01.004 Abstract ( 453 )   HTML ( 14 )   PDF (6400KB) ( 113 )   Save Based on the daily precipitation data under the SSPs (Shared Socioeconomic Pathways) emission scenarios from the latest generation CMIP6 (Coupled Model Intercomparison Project Phase 6) global climate models and high-resolution daily grid observation data, the performance of the models was evaluated using the Taylor diagrams and Quantile-Mapping method.Eight extreme precipitation indices for the near (2021-2040), middle (2051-2070), and late (2081-2100) periods of the 21st century were calculated and analyzed under the SSP2-4.5 and SSP5-8.5 scenarios.The results show that in the reference period (1991-2010), after the Quantile-Mapping method correction, the simulation of each extreme precipitation index is closer to the observation, and the spatial correlation coefficient, root mean square error, and standard deviation are greatly improved.For each stage of the 21st century, both the annual cumulative precipitation (Prcptot) and the number of extreme rainstorm days (R50mm) in Fujian province are higher than those during the reference period (1991-2010), and larger the increase in the later stage under the high emission scenario.The number of precipitation days larger than 10mm (R10mm) and the number of extremely heavy rain days (R20mm) increases and decreases in different ways.R10mm shows a decreasing trend in the northeastern part of Fujian province and an increasing trend in most other areas.R20mm shows a decreasing trend in the northwestern part of Fujian province in the recent 21st century under SSP2-4.5 scenarios, but an increasing trend in other scenarios and time periods.The maximum 1 d precipitation (Rx1day), maximum consecutive 5 d precipitation (Rx5day) and daily precipitation intensity index (SDII), which represent the precipitation intensity, will all increase in the future, and the increase rate in coastal areas is higher than that in inland areas.The continuous dryness index (CDD) increases in most areas, which indicates that the extreme precipitation and continuous dryness will increase together in Fujian province in the future, and the probability of extreme drought and flood events will increase significantly. Figures and Tables | References | Related Articles | Metrics

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Temporal and spatial distribution and characteristics of microphysical structure of fog in Liupan Mountain area Zhang-li DANG,Jian-ren SANG,Xu ZHOU,Zhuo-lin CHANG,Yan-qiao SUN 2023, 39 (1):  37-43.  doi: 10.3969/j.issn.1673-503X.2023.01.005 Abstract ( 160 )   HTML ( 16 )   PDF (1326KB) ( 179 )   Save Based on visibility information of the weather stations in Yuanzhouqu, Xiji, Liupan Mountain, Longde, and Jingyuan from 1989 to 2018 and in Pengyang from 1999 to 2018, as well as the data measured with fog droplet spectrometer at orographical cloud observation site and the conventional surface meteorological observation in Liupan Mountain from November 1, 2019 to October 31, 2020, the annual, seasonal, monthly and daily changes characteristics of fog and the droplet spectrum feature of typical fog in Liupan Mountain area were analyzed.The results showed that the fog has obviously temporal change characteristics and the number of fog days is an average of 118.5 d and the largest in autumn especially in September, and the largest frequency is at 08:00 in the daytime.Freezing fog mainly occurs from November 8 to April 22 of the next year and warm fog mainly occurs from May 5 to October 11.In addition, freezing fog and warm fog have a long maturity stage and short development and dissipating stage.During the maturity stage, the fog droplet spectrum is broadened, the average droplet number concentration is 4.58-107.57 per cm3, the average liquid water content is 0.001-0.049 g·m-3, and the average droplet diameters is 3.75-12.22 μm.The values of the above-mentioned variables in Liupan Mountain all are smaller than those in Nanjing and Zhanjiang and Maoming.The droplet number concentration from the development to dissipation stage for freezing fog are larger than those for warm fog, the liquid water content and droplet diameters of freezing fog are larger from maturity to dissipation stage, but are smaller at the development stage than those of warm fog.The droplet size of freezing fog features single peak with a maximum at 6 μm where the maximum of dN/dD is 26.19 cm-3·μm-1, while the droplet size of warm fog features double peaks with the first and second peak values at 7 μm and 11 μm, respectively, which is the same as the situation of fog droplet spectrum in Lushan.However, the peak value of droplet diameters is larger than those in Nanjing and Zhanjiang. Figures and Tables | References | Related Articles | Metrics

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Study on hourly PM2.5 concentration forecast based on XGBoost method in Xi'an city Xu-ting ZHANG,Hui LIU,Rui-fang LIU,Fei JU,Jia-hui-min LIU,Xing-xing GAO,Shao-ni HUANG,Nan WANG 2023, 39 (1):  44-54.  doi: 10.3969/j.issn.1673-503X.2023.01.006 Abstract ( 154 )   HTML ( 17 )   PDF (2312KB) ( 220 )   Save Based on the eXtreme Gradient Boosting (XGBoost) machine learning algorithm model, using hourly PM2.5 concentration monitoring data and meteorological observation data in Xi'an from 2016 to 2021, the forecast test of hourly PM2.5 concentration was carried out by selecting meteorological and time factors as the input features.The results showed that PM2.5 concentration has a significant negative correlation with average temperature and visibility, and relative humidity and dew point temperature are significantly positively correlated with PM2.5 concentration in winter.Easterly wind is more likely to produce heavily polluted weather.Generally, air pollution occurs frequently from the end of December to the beginning of January, but the PM2.5 concentration is decreasing year by year.The PM2.5 concentration in winter shows the most obvious bimodal diurnal variation with the highest values appearing in the early morning and around 11:00.Meanwhile, there is a "weekend effect" in the change of PM2.5 concentration.The forecast model can truly reflect the changes of PM2.5 concentration magnitude and trend with the determination coefficient of 0.77, the mean absolute error of 12.79 μg·m-3 and the root mean square error of 18.68 μg·m-3 between forecasted and observed values.The model has a relatively stable performance and better effect in forecasting PM2.5 concentration in autumn and winter than in spring and summer but underestimates the extreme peaks.Besides, the forecast model has good interpretability and is clearly influenced by the visibility feature variables and the importance of feature variable such as dew point temperature, relative humidity, average temperature, and sea level pressure decrease in turn.Meanwhile, the time factors have a certain impact on the model.In addition, the forecast accuracy and efficiency of this model are higher than those of other statistical and machine-learning models. Figures and Tables | References | Related Articles | Metrics

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Influence of the change of visibility observation method on the statistics and identification of fog and haze in the Beijing-Tianjin-Hebei region Gang ZHU,Jiang-bo LI,Zhuo SUN,Shuo-fei WANG 2023, 39 (1):  55-64.  doi: 10.3969/j.issn.1673-503X.2023.01.007 Abstract ( 119 )   HTML ( 10 )   PDF (4280KB) ( 90 )   Save Based on the visibility and conventional ground observation data of 177 stations in the Beijing-Tianjin-Hebei region during the period from 2000 to 2018 which is divided into three stages of 2000-2013, 2014, and 2015-2020 when the human visual measurement (HM), the instrumental derived measurement (IM) and the joint observation of HM and IM are adopted, respectively, the visibilities measured by HM and IM were compared and analyzed.The cold and the warm season were respectively defined as the period from November to April of the following year and from May to October.The results show that the annual average visibilities measured by IM at 08:00 and 14:00 are lower than those measured by HM.In the cold season, the measured monthly average visibility at 08:00 by IM is lower than that by HM, and the difference between two methods at 14:00 is significantly smaller than at 08:00.In the warm season, the visibility at 08:00 measured by IM is lower than that by HM, but the difference is generally lower than that in the cold season and is the smallest in May.In 2014, fog and haze occur frequently from January to April.The visibilities at 08:00 and 14:00 measured by IM are obviously less than those by HM.From May to December when there is less haze, the visibilities of more than half stations measured by IM are greater than those by HM.When the visibility is below 12 km, the measured values by IM are less than those by HM, and when the visibility is above the 12 km, the measured values by IM are greater than those by HM.When the visibility is less than 1 km, the measured values by IM are close to those by HM.There is an inverse correlation between visibility and relative humidity.When the visibility is less than 0.5 km, the relative humidities measured by IM and HM range from 93% to 96%, but with the increase of visibility, the relative humidity measured by IM is more scattered than that by HM.After the observation is changed from HM to IM, the occurrence frequencies of fog and haze increase obviously, especially for haze.The high incidence area of fog measured by IM and HM both are distributed along the Beijing-Guangzhou railway in the Beijing-Tianjin-Hebei region, but the haze high incidence area moves eastward from the shallow mountain area of the south-central Taihang Mountain to the plain to the line of Beijing-Guangzhou Railway. Figures and Tables | References | Related Articles | Metrics

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Characteristics and variation trend of ski meteorological conditions in Liaoning province Yu-tong JIANG,Li-yong XIE,Shi-bo GAO,Li-jie YU 2023, 39 (1):  65-72.  doi: 10.3969/j.issn.1673-503X.2023.01.008 Abstract ( 222 )   HTML ( 14 )   PDF (2369KB) ( 204 )   Save Based on the data of 61 national surface meteorological observation stations in Liaoning province from 1961 to 2020, the characteristics and long-term trend of meteorological conditions suitable for ski resort construction and ski sports were analyzed.The results showed that the annual number of freezing days (with a daily maximum air temperature of less than 0 ℃) in the central, northern and eastern parts of Liaoning province is more than 60 d, which meets the temperature standard for the construction of high-level ski resorts.The annual average snowfall in the central and eastern parts of Liaoning province exceeds 20 mm, and the snow depth exceeds 10 cm, which is the most suitable area for the construction of ski resorts in Liaoning province.Through comprehensive analysis of meteorological factors that have the most significant impacts on skiing, such as wind force, temperature, and snowfall days, it is found that the number of days with a ski meteorological index above level 2 is the highest in the central and eastern regions of Liaoning province, exceeding 120 d.These areas are the most suitable areas for skiing sports in Liaoning province.Among them, the Fushun area has great advantages in the development of skiing events, which is conducive to hosting the snow events of the National Winter Games.The long-term trends of skiing meteorological conditions show that the number of freezing days has decreased significantly, the annual snowfall and annual maximum snow depth have slightly decreased, and the most suitable areas for ski resorts have decreased.While the number of days with a skiing meteorological index above level 2 has increased 12.2 d, the area suitable for skiing is expanding westward, and the meteorological conditions are more conducive to the development of skiing.Meteorological indicators related to temperature and wind speed are the main factors for the long-term trend of skiing meteorological conditions.Meanwhile, the central and eastern regions of Liaoning province have favorable meteorological conditions and have advantages in terrain, economy, transportation, etc., which will provide a good foundation for the development of high-quality ice and snow sports, and cultural tourism industries. Figures and Tables | References | Related Articles | Metrics

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Research on soil moisture retrieval model based on optical remote sensing and microwave remote sensing Jing-li WANG,Tian-jiao GAO,Rong-ping LI,Peng-cheng YU,Yun-tao MA,Na MI,Ri-hong WEN,Kai ZHANG 2023, 39 (1):  73-82.  doi: 10.3969/j.issn.1673-503X.2023.01.009 Abstract ( 223 )   HTML ( 18 )   PDF (2087KB) ( 266 )   Save Based on the Sentinel-1 and Landsat 8 image data on May 17, 2020, and in combination with the field manual moisture measurement data, taking Chaoyang of Liaoning province as an example, the soil moisture was retrieved using the vegetation temperature index method and the optical collaborative microwave remote sensing inversion algorithm, respectively, and a high-precision soil moisture forecasting model was built.The results showed that the Vegetation Temperature Index (TVDI) based on optical remote sensing cannot well retrieve farmland soil moisture.Microwave reflection could be better feedback on the spatial variation of soil moisture, and the fitting accuracy of VV polarization of Sentinel-1 radar data for soil moisture (R2=0.71) is better than VH polarization (R2=0.27).The improved water cloud model (WCM) based on Global Vegetation Moisture Index (GVMI) has the best performance (R2=0.80).Using collaborative inversion of microwave and optical remote sensing can retrieve high-spatial-resolution and high-precision farmland soil moisture data, which is helpful for agricultural drought monitoring. Figures and Tables | References | Related Articles | Metrics

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Characteristics of the tropospheric wind field in Jiyuan based on second-level sounding data Yu-feng TUO,Ming SHAO,Ya-hua WANG,Qiang LU,Kai-feng ZHANG 2023, 39 (1):  83-91.  doi: 10.3969/j.issn.1673-503X.2023.01.010 Abstract ( 134 )   HTML ( 7 )   PDF (2778KB) ( 245 )   Save Using the data measured by a new-generation L-band upper-air meteorological radar in Jiyuan, He'nan province from January of 2007 to December of 2020, the characteristics of the tropospheric wind field in Jiyuan were analyzed.The results showed that the average wind speed below 10000 m in Jiyuan has a single increase trend with height, which is relatively severe in winter and relatively gentle in summer.From January, the horizontal wind speed of each layer in Jiyuan, especially the troposphere above 1000 m, gradually decreases, that is, the height of the strong wind area continues to rise.From June to September, the wind speed of each layer is relatively small, and then it gradually increases from October and the height of the strong wind area keeps dropping.The proportion of wind speed below 10 m·s-1 in the troposphere shows a single decreasing trend with height, and the proportion of 10 m·s-1＜ wind speed ≤ 20 m·s-1 exhibits a fusiform pattern characterized by first increasing and then decreasing with height.The altitude where the largest proportion is located changes as being rising in spring, reaching the highest in summer, decreasing in autumn, and droping the lowest in winter.The proportion of strong winds above 30 m ·s-1 shows a single increasing trend with height, however, its height, increasing rate, and proportion at each layer are different in different seasons, with the highesty height, and the lowest proportion of each layer in summer, followed by spring and autumn, and with the lowest height, the fastest increasing rate and the largest proportion of each layer in winter.The characteristics of the continental monsoon climate in Jiyuan throughout the year and the northwesterly winds are dominant in the lower layer in January.The dominant wind direction has been varied clockwise from the low layers to the high layers since February.From June to July, the easterly wind occupies, and the deflection height reaches the highest.In August, the dominant wind direction turns counterclockwise from high to low.In November, northwesterly winds are dominant in the entire layer and turn back again, which maintains until January of the following year. Figures and Tables | References | Related Articles | Metrics

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Spatial and temporal distribution of drought and flood in the growing season of soybean in Heilongjiang province Mo ZHAI,Xiu-fen LI,Dan LIU,Lan YU,Hui-hui QU 2023, 39 (1):  92-99.  doi: 10.3969/j.issn.1673-503X.2023.01.011 Abstract ( 201 )   HTML ( 13 )   PDF (2214KB) ( 116 )   Save Based on the daily meteorological data from 62 meteorological stations in Heilongjiang province from 1961 to 2019, the water requirement of soybean was calculated using the method recommended by FAO, and the effective precipitation was calculated using the method recommended by Soil Conservation Service of the United States Department of Agriculture.M-K test and GIS inverse distance weighted interpolation methods were used to analyze the crop water surplus deficit index (CWSDI) and the evolution characteristics of drought and flood at different growth stages of soybean in Heilongjiang province.The results showed that the effective precipitation in the growing season of soybean in Heilongjiang province mainly increased before flowering and decreased after flowering.The water requirement of soybean mainly increased before the third true leaf stage, but decreased after the third true leaf stage, and decreased significantly at pod-grain filling stage and drum-mature stage.The CWSDI of soybean in the growing season was the highest in the eastern central region and the northernmost region, and the eastern region was higher than the western region.The CWSDI was the lowest in flowering-pod and pod-drum stages, and the highest in the drum-grain stage.The flood occurred more frequently in the northern region, more in the east than in the west, and the number of flood stations was the most in the emerging and third true leaf stage.The frequency of drought was higher than that of a flood, higher in the west or southwest than in the east, and lowest in the central and north.Drought often occured in flowering-grain stage. Figures and Tables | References | Related Articles | Metrics

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Variation of ecosystem quality and its response to climatic factors in Erhai Basin Yu-qin HE,Hong XU,Jin-xin CHENG,Li-zhang FAN 2023, 39 (1):  100-106.  doi: 10.3969/j.issn.1673-503X.2023.01.012 Abstract ( 106 )   HTML ( 8 )   PDF (1729KB) ( 127 )   Save Using the multi-source remote sensing data and meteorological observation data, a comprehensive evaluation model of remote sensing was constructed based on the ecosystem productivity index (EPI), stability index (ESI), and bearing capacity index (EBCI).The ecosystem quality of the Erhai Basin from 2005 to 2020 was quantitatively studied, and the correlation between its changes and climatic factors was analyzed.The results indicated that the mean value of the ecosystem quality comprehensive index (EQCI) in Erhai Basin was 56.49 (total score was 100), and the mean value of EPI, ESI, and EBCI was 49.05, 74.16, and 56.97, respectively.It could be seen that the ecosystem stability of the Erhai basin was good, and the EPI, ESI, EBCI, and EQCI all showed an increasing trend in the past 16 years.Among different ecosystems, the level of environmental quality in descending order was forest>grassland>farmland>town>wetland>water body.The transformation of local classes into urban types would have a negative impact on ecosystem quality.There was a positive correlation between air temperature, precipitation, and EQCI in grassland, forest, and farmland ecosystems, and a negative correlation between air temperature and EQCI in urban ecosystems. Figures and Tables | References | Related Articles | Metrics

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Characteristics of wind speed at different heights of wind mast in Tianjin coastal areas Rui MIAO,Ling GUO,Xi-fan ZHANG,Mei-ling SUN,Xue-jiao WANG 2023, 39 (1):  107-112.  doi: 10.3969/j.issn.1673-503X.2023.01.013 Abstract ( 219 )   HTML ( 11 )   PDF (1121KB) ( 273 )   Save Based on the observation data from wind masts in Hangu and Dagang at the eastern coastal area of Tianjin from 2017 to 2019, the temporal variation characteristics of wind speed at different heights of wind masts were analyzed statistically, and the relationship between wind speed at 30~100 m and 10 m as well as the variation of wind shear index, were discussed.The results showed that the wind speed at each height had obvious seasonal variation characteristics.In spring, the wind speed was the highest, and the most prone to gales.The average wind speed, the number of gales days, and the intensity of gales were the highest.The wind speed was minimum during the transition period of summer and autumn.In addition, the wind speed had obvious diurnal variation characteristics, and the wind speed at each height reached the maximum in the afternoon.Correlation analysis showed that the wind speed at 30~100 m was positively correlated with that at 10 m.The difference in wind speed and wind shear index at each height and 10 m height showed similar diurnal variation characteristics, that is, they were both minima in the afternoon when sea breeze prevail.Comparing the characteristics of two wind masts, it was found that the mean wind speed in Hangu was larger, the frequency of gale weather was more frequent, the intensity of gale was more, and the diurnal variation of wind speed and sea and land wind was more obvious. Figures and Tables | References | Related Articles | Metrics