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30 December 2021, Volume 37 Issue 6 Previous Issue    Next Issue

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Diagnostic analysis of potential vortex of a severe squall line weather process in South China Wen-juan LI, Xiao-ding YU, Dai-gao TENG, Xia-yun PENG, Han-hua LIU 2021, 37 (6):  1-10.  doi: 10.3969/j.issn.1673-503X.2021.06.001 Abstract ( 256 )   HTML ( 149 )   PDF (5158KB) ( 273 )   Save Based on the data of FY-4A satellite infrared and water vapor cloud image, the NCEP (National Centers for Environmental Prediction) analysis field, variable pressure, variable temperature, gale, and precipitation from the ground automatic weather stations, the occurrence, and development mechanism of a strong squall line in South China occurring on March 4, 2018, and the main causes of the persistent gale were analyzed by calculating the vortex of the isentropic surface.The results show that the convective cell is triggered by a low-level convergence system.A thunderstorm sinking airflow forms a ground convergence line with the southwest airflow in front of it, and the water vapor, static instability, and vertical wind shear conditions in the moving area are favorable to the development of severe convective storms and cause a convective storm to occur.The area of the extreme gale is mainly distributed at the top of the bow structure in the squall line.The falling area corresponds to the gradients of the brightness temperature and the variable pressure, which increases the variable pressure wind.The moving direction of the squall line is consistent with that of the guiding airflow and almost perpendicular to that of the low-level Southwest jet.The speed of the squall line is significantly accelerated, and the momentum downward effect is enhanced, which may be the important cause of an extreme gale on the ground.The potential vortex (PV) distribution indicates that the intrusion of high PV has a certain correlation with the formation of bow-shaped in the low PV region.The dry intrusion zone has a good correspondence with the high PV region on the isentropic layer.The dark zone at the back of the squall line is the front of dry intrusion.The downward propagation of the high potential vortex at the upper level is the cause of the continuous development of the squall line. Figures and Tables | References | Related Articles | Metrics

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Local dust weather process caused by a mesoscale convective storm in Inner Mongolia Autonomous Region Xue-qiang WANG,Hui-jie DONG 2021, 37 (6):  11-19.  doi: 10.3969/j.issn.1673-503X.2021.06.002 Abstract ( 194 )   HTML ( 121 )   PDF (3830KB) ( 176 )   Save In this paper, a typical local dust weather process in Xilingol League in the early summer of 2018 was analyzed using the analysis data from MICAPS (Meteorological Information Combine Analysis and Process System) and NCEP (National Centers for Environmental Prediction), data from the automatic weather stations, Satellite infrared cloud map, weather radar, etc.The dust weather is mainly caused by the strong convective storm triggered by the low-level shear under the background of the upper air cold vortex circulation and occurs in the downdraft of the strong convective storm.The observation data of the automatic weather stations in every five minutes interval show that when the dust occurs, the air pressure on the ground jumps from 995.2 hPa to 1000.4 hPa, the air temperature drops, the wind direction changes from the northeast (31°) to the northwest (343°), and the wind speed increases instantaneously.According to the weather situation, in the warm and unstable atmosphere, the convective cloud cluster is developing vigorously, and the strong downdraft at the outer boundary causes a strong wind near the ground, which provides a better dynamic condition for the short-term dust weather.Before the occurrence of local dust, the dynamic and thermal conditions are conducive to the occurrence and development of severe convective weather.The main causes of local dust weather are convergence at the lower level, divergence at a high level, strong upward motion, and dryness at the middle level and underlying surface. Figures and Tables | References | Related Articles | Metrics

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Cause analysis of enhanced precipitation anomaly in December of 2019 in Jilin province Tian-yu LI, Li ZHANG, Dong-xue FU, Xiao-fan LI, Ning LIU 2021, 37 (6):  20-26.  doi: 10.3969/j.issn.1673-503X.2021.06.003 Abstract ( 205 )   HTML ( 124 )   PDF (2452KB) ( 88 )   Save The characteristics of precipitation anomalies in December of 2019 in Jilin province were analyzed based on atmospheric circulation and sea surface temperature (SST) anomaly.The possible influence mechanism of SST anomaly in key areas near Japan in the early autumn on this precipitation anomaly was studied.The results show that since 1981, the precipitation in December in Jilin province has increased significantly.Under the climate background of more inter-decadal precipitation, the precipitation in December of 2019 in Jilin province is 227.5% of that in the same period of the history year, ranking the fourth place with more rain and snow in the same period since 1981.The anomalous warm SST in key areas near Japan in the early autumn is one of the driving conditions for the anomalous heavy precipitation in Jilin province in December.In the anomalous warm SST years in the early autumn, on the one hand, there is an abnormal anticyclone from the Sea of Okhotsk to Japan, and the blocking high is active.There is a negative height anomaly over the area around Lake Baikal, and the East Asian winter monsoon system is weakened.The abnormal increase of local SST increases the water vapor content in the East Asian winter monsoon season, which brings sufficient water vapor over Jilin province.On the other hand, due to the west wind anomaly near the mid-latitude 45°N, cold air is brought to Northeast China.Under the action of positive vorticity advection in front of the trough, there is upward movement, which provides dynamic conditions for precipitation.In the early SST abnormally cold years, there are zonal circulation in middle and high latitudes, prevailing westerly winds in Northeast China, strong winter winds in East Asia, abnormal northerly winds in East China, and strong Siberian high.Insufficient water vapor and dynamic conditions of precipitation in Jilin province result in less precipitation anomaly. Figures and Tables | References | Related Articles | Metrics

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Characteristics of ozone pollution and synoptic classifications in Hainan province from 2015 to 2018 Chuan-bo FU, Li DAN, Wen-shuai XU, Li-jun LIU 2021, 37 (6):  27-35.  doi: 10.3969/j.issn.1673-503X.2021.06.004 Abstract ( 327 )   HTML ( 18 )   PDF (3269KB) ( 316 )   Save Based on the O3 concentration data at 32 air quality monitoring stations in 18 cities and counties in Hainan province from 2015 to 2018, the spatio-temporal variation characteristics of regional O3 pollution (defined as ≥ 3 cities and counties with O3 concentration during eight hours exceeding the standard) were analyzed, and the subjective classification of synoptic weather systems causing O3 pollution was conducted.The results show that 40 days are occurring regional O3 pollution in Hainan province from 2015 to 2018, with an occurrence probability of 2.73%.In 2015 and 2017, it reaches 13 days, with a probability of 3.56%, the following is 11 days in 2018 (3.01%), and the minimum is only 3 days in 2016 (0.82%).The synoptic systems affecting regional O3 pollution are classified into four patterns, including cold air westward circulation pattern, cold air eastward circulation pattern, warming high-pressure ridge pattern, and tropical system pattern.The cold air westward circulation pattern is the predominant regional O3 pollution pattern, occurring for 14 days, accounting for 35% of all days, with heavy pollution.Different synoptic system patterns show different distributed characteristics of regional O3 pollution.The conditions with downdraft at 500 hPa, northeast wind at a lower level, low relative humidity area extending from eastern China to Hainan province, Hainan locating at the bottom of cold high pressure or locating at the northwest side of the tropical cyclone, temperature dew point difference above 5℃ are helpful to occur the regional O3 pollution in Hainan province. Figures and Tables | References | Related Articles | Metrics

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Evaluation of air quality improvement in Taiyuan during Second National Youth Games Wei GUO, Ling-yun ZHU, Wen-ya WANG, Xing-ai GAO, Peng-wei CHENG, Yue-jun ZHANG 2021, 37 (6):  36-43.  doi: 10.3969/j.issn.1673-503X.2021.06.005 Abstract ( 154 )   HTML ( 10 )   PDF (1482KB) ( 160 )   Save To evaluate the impact of air pollution control measures on air quality improvement during the Second National Youth Games held in Taiyuan, we analyzed the evolution of concentrations of six pollutants and the vertical variation of aerosols in three periods (before the games, during the games, and after the games).The results show that compared with the period before the games, the concentrations of PM10, PM2.5, CO, NO2, and O3 during the games decrease by 30.5%, 37.3%, 20.2%, 18.0%, and 18.6%, respectively in Taiyuan, while the reduction of SO2 is not obvious.In terms of the vertical variation, the peak value of aerosol extinction coefficient decreases by 24.6% during the games on average, decreasing by 46% under low relative humidity (RH < 60%) conditions and 21.6% under high RH (>60%) conditions, respectively.The ratio of PM2.5 to PM10 decreases during the game and the hygroscopic growth effect of aerosols in the vertical atmosphere is enhanced.Compared with the same period in 2017 and 2018, all the concentrations of PM10, PM2.5, CO, and NO2 decrease significantly, while the O3 concentration exhibits small variation.In conclusion, control measures during the Youth Games can effectively reduce the local particulate matter concentrations. Figures and Tables | References | Related Articles | Metrics

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Simulation of thermal environment and analysis of thermal comfort variation in wintertime in Fuzhou University campus using ENVI-met Li-juan ZHUANG,Yuan-bin CAI,Juan-juan QI 2021, 37 (6):  44-52.  doi: 10.3969/j.issn.1673-503X.2021.06.006 Abstract ( 175 )   HTML ( 4 )   PDF (2258KB) ( 329 )   Save In this study, we simulated and analyzed the variation of thermal environment and its thermal comfort response on typical winter days in the research area (teaching area in Fuzhou University) using a three-dimensional non-static microclimate model ENVI-met.We also calibrated and verified the ENVI-met model based on a field survey.The results show that the ENVI-met model can well represent the outdoor thermal environment and accurately predict the diurnal variation of air temperature and relative humidity.The daily mean air temperature at the pedestrian's height over concrete pavement and gray brick pavement is 0.1℃ and 0.3℃ higher than that on grassland, and their maximum hourly temperature difference reaches 0.68℃ and 0.65℃, respectively.Building and tree shadows can reduce air temperature at the pedestrian's height by 1.1-1.9℃.The difference of mean radiant temperature (Tmrt) in the same cluster with and without shade can reach up to 30℃.The value of physiological equivalent temperature (PET) near trees and inside building clusters is 2-3 grades lower than that over the hard pavement.In the vegetation-free scheme, the areas with high temperature and low humidity are expanded, and the warming effect in the vertical direction can extend to 10.5 m.Meanwhile, wind speed increases by 1.23 m·s-1 at the most, the areas with higher mean radiant temperature increase by 69.25%, and the thermal comfort zone and thermal discomfort zone increase by 19.78% and 2.03%, respectively.The research results can favor the urban planning and landscape design for better space construction and greening improvement and can provide some guidance and reference for the optimization of the layout of various underlying surfaces and the selection of vegetation types. Figures and Tables | References | Related Articles | Metrics

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Characteristics of extratropical cyclones affecting Dalian and causes of outbreak cyclones in spring during 2010 to 2019 Yan LI,Han SAI,Ting HUANG,Yan GAO 2021, 37 (6):  53-61.  doi: 10.3969/j.issn.1673-503X.2021.06.007 Abstract ( 196 )   HTML ( 8 )   PDF (4513KB) ( 77 )   Save We analyzed the characteristics of spring extratropical cyclones affecting Dalian and the physical mechanism of extreme weather caused by outbreak cyclones using conventional and intensive meteorological observation data from 2010 to 2019, the National Centers for Environmental Prediction (NCEP) reanalysis data, satellite cloud images, etc.The results show that the number of extratropical cyclones entering the Bohai and the northern Yellow Sea is 2.4 per month.Cyclones usually enter the Yellow Sea at first, and 84.5% of the extratropical cyclones (including entering the Yellow Sea directly or through the Bohai Sea) can enter the northern Yellow Sea.In spring, 73% of the cyclones entering the Bohai and the Yellow Sea can cause strong winds or precipitation in Dalian, and their effect probability on the eastern coast of Dalian is much higher than on the other areas.The outbreak cyclones causing severe disastrous weather occur most frequently in spring, with the paths moving from the southwest to the northeast.The occurrence of outbreak cyclones is mainly due to the quick decline of extratropical cyclones pressure in a short period after cyclones passing the Bohai and the Yellow Sea and their explosive development in the land of Dalian.The extratropical cyclones usually develop from the lower levels with significant frontogenesis and baroclinity.The outbreak development of the cyclones occurs in exit areas of the upper-level jets with the strongest positive vorticity advection and corresponds to the left front convergence of the low-level jets at lower altitudes.Strong cold and warm temperature advection are major reasons for extreme precipitation and strong winds.The formation of a rainstorm is mainly due to the continuous transport of warm and wet air brought by extratropical cyclones.Vertical transport of water vapor driven by strong ascending motion moistens a whole layer.When low-level jets develop and cold and warm air masses intersect, strong precipitation occurs at the moist baroclinic front with high humidity and temperature.Strong cold air from the north and the extratropical cyclones on the Bohai and the Yellow Sea contribute extremely strong air pressure gradient, which is the main reason for extremely strong winds. Figures and Tables | References | Related Articles | Metrics

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Variation assessment of ecological carrying capacity using three-dimensional ecological footprint model in Guilin from 2000 to 2018 Xiao-ying WANG,Hui ZHANG,Wen-quan ZHU,Ri-hong WEN,Rong-ping LI,Jiang-ming MA 2021, 37 (6):  62-70.  doi: 10.3969/j.issn.1673-503X.2021.06.008 Abstract ( 161 )   HTML ( 10 )   PDF (1996KB) ( 82 )   Save In this paper, we introduced the evaluation method of balance indicator and production indicator based on satellite retrieved net primarily production of vegetation that is implemented into a three-dimensional ecological footprint model.Using this model, we further calculated and analyzed the ecological carrying capacity and sustainable development ability of resources and environment in 2000, 2005, 2010, 2015, and 2018 in Guilin from the perspectives of space and time, using footprint breadth and footprint depth as the measurement unit and "national hectare".In addition, the utilization efficiency of natural resources in Guilin was quantitatively evaluated using the economic evaluation index (Gross Domestic Product, GDP) and ecological footprint index.The results showed that the ecological carrying capacity in Guilin increases slightly from 2000 to 2018, while the ecological footprint and ecological deficit both increase at first with the peak values appearing in 2010 and then decrease.Contribution rates of various land-use types to the per capita ecological footprint and ecological carrying capacity are quite different, and the demand and supply levels of all kinds of land in social and economic construction are unequal.The footprint breadth increases in all years except for 2005, and the footprint depth increases first and then decreases.The excessive consumption of natural resources is an important factor affecting the sustainable development of the ecological environment in Guilin.The ecological efficiency of natural resources in Guilin increases significantly from 2000 to 2018.After 2010, the tertiary industry gradually plays a major role in economic construction, with great economic development potential. Figures and Tables | References | Related Articles | Metrics

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Remote sensing estimation of reed NPP in Yuehai Wetland and characteristic analysis of its temporal and spatial changes Yu-feng ZHONG, Tao NIU, Wen-xian JIA, Yun-lei CUI, Hong-li LIU, Bo-wen DENG, Yang CUI, Men-xin WU 2021, 37 (6):  71-78.  doi: 10.3969/j.issn.1673-503X.2021.06.009 Abstract ( 145 )   HTML ( 4 )   PDF (1754KB) ( 209 )   Save Using Landsat 5 data from 1987 to 2012, and Landsat 8 data from 2013 to 2017, the spatio-temporal characteristics and changing trends of net primary productivity (NPP) in Yuehai Wetland from 1987 to 2017 were analyzed.At the same time, based on high-resolution (Gaofen) data (GF2), the spatio-temporal changes of NPP with 4 m resolution from 2015 to 2017 were estimated and compared with Landsat results.The results show that the NPP in 2002 was the lowest with a value of 691.11 g·C·m-2, and the average NPP increased firstly and then decreased from 2003 to 2007.After 2008, the average NPP tended to be stable.Reeds are distributed widely in the central and surrounding areas in Yuehai Wetland from the 1980s to the 1990s.And then reeds are concentrated in the northeastern region of the wetland from the 2000s to the 2010s.NPP of Yuehai Wetland changed significantly from 1987 to 2017.The area in the northeastern region of Yuehai Wetland is a decreasing trend.Comparing the average NPP retrieved by GF2 and Landsat in Yuehai Wetland from 2016 to 2017, it can be found that there is no significant difference between them and their changing trends are consistent. Figures and Tables | References | Related Articles | Metrics

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The distribution characteristics of ground flash and classification of lightning intensity in Hubei province from 2007 to 2019 Tian-ye YU,Xue-liang WANG,Ke-jie ZHANG,Tao ZHAO,Xiao-fei WANG 2021, 37 (6):  79-85.  doi: 10.3969/j.issn.1673-503X.2021.06.010 Abstract ( 530 )   HTML ( 17 )   PDF (1286KB) ( 353 )   Save To provide evidence for lightning protection engineering design and lightning disaster protection work, further study was carried out on lightning activity regularity in Hubei province.According to the monitored data of ground flash from 2007 to 2019, temporal and spatial distribution characteristics of lightning activity were analyzed using the mathematical statistics method.Combining two parameters, ground flash density, and lightning current intensity, the concept of lightning intensity was proposed, and the classification of lightning intensity levels in Hubei province was completed.The results show that the lightning activity in Hubei province is mainly negative lightning, which accounts for 94.7%.The average intensity for positive, negative ground flash and the whole lightning are 50.2 kA, 36.0 kA, and 37.0 kA, respectively.The lightning activities mainly occur between March and September in a year and between 14:00 and 20:00 pm in a day.The positive ground flash has a high proportion in the low incidence months and periods of lightning.The monthly variation of positive ground flash intensity appears to be a V-shaped form, while total ground flash and negative ground flash fluctuate from month to month.The daily variation of lightning current intensity shows a single-peak and single-valley type.The peak value of positive ground flash intensity appears at 09:00 and the valley value appears at 15:00.The peak value of ground flash and negative lightning intensity appears at 05:00 and the valley value appears from 13:00 to 14:00.There are regional differences in ground flash density and lightning current intensity, and the overall distribution is high in the east and low in the west.The lightning intensity in Hubei province can be divided into three levels: high, medium, and low.The high-value areas are mainly located in the confluence zone of Dabieshan Mountains, Mufushan Mountains, Jianghan Plain, and the transition zone from the western mountainous area to Jianghan Plain, while the low-value areas are mainly distributed in the southwest, northwest, and some individual edge areas of Hubei province.The median areas are mainly distributed in the central plain areas of Hubei province. Figures and Tables | References | Related Articles | Metrics

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Characteristics of ground flash and its relationship with altitude in Hangzhou from 2010 to 2019 Xue-wen BIAN,Wen-jia ZHENG,Qiang LI,Wei SUN 2021, 37 (6):  86-92.  doi: 10.3969/j.issn.1673-503X.2021.06.011 Abstract ( 150 )   HTML ( 2 )   PDF (1374KB) ( 88 )   Save Based on lightning location data from 2010 to 2019 in Hangzhou, the characteristics of ground flash and its relationship with altitude were analyzed using mathematical statistics and linear regression methods.The results show that the number of ground flashes in the east is greater than that in the west of Hangzhou and the number of ground flashes in the south is greater than that in the north.The region with a high density of ground flash is southwest of Hangzhou and the frequency of ground flash in the low altitude area is higher than that in the high altitude areas.The season with the highest frequency of ground flash is summer and ground flash mainly occurs in July and August.The frequencies of ground flashes in spring and autumn are similar, while the frequency in winter is one order of magnitude less than that in the other three seasons.In summer and autumn, the ground flash usually occurs from mid-afternoon to late-afternoon, while in spring, it occurs frequently in the early morning, which may be related to the long duration of nocturnal medium size convective system.The absolute value of ground flash intensity mainly concentrates from 10 to 60 kA.The average value of the positive ground flash increases with the altitude, and the average value of the negative ground flash and the total lightning current show a "V" shape along with the elevation.The proportions of positive, negative and the total ground flash current ≤ 16 kA and ≥ 100 kA decrease with the increase of altitude.The shielding failure rate is higher for hills' elevation from 100 to 200 meters and small mountains' elevation from 200 to 500 meters.The shielding failure risk caused by lightning current ≤ 16 kA and mountains' elevation higher than 1500 meters is low.The probability of shielding failure caused by lightning current ≥ 100 kA and mountains' elevation less than 400 meters is high.There are virtually no counterattacks at mountains' elevation above 1600 meters. Figures and Tables | References | Related Articles | Metrics

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Applicability analysis of linear calculation for missing data of wind tower on typical terrain in Liaoning province Zheng-qiang GU,Qiang GONG,Li-du SHEN,Hong XU,Dong-lei MA,Ling ZHU,Hua CHAO,Dong-lei FENG 2021, 37 (6):  93-99.  doi: 10.3969/j.issn.1673-503X.2021.06.012 Abstract ( 117 )   HTML ( 5 )   PDF (931KB) ( 75 )   Save Using the hourly measured wind speed data from 26 wind towers and 6 weather stations at the same period in Liaoning province, the linear fitting at different time scales (month, season, and year), together with wind sheer index, were used to develop 7 schemes to reconstruct the missing wind speed data of the wind towers, and the error test of each proposed reconstruction scheme was conducted.Results show that the linear fitting on monthly data, with corresponding wind sheer indexes (schemes 3 and 7), is the optimal scheme for the data reconstruction of wind towers on typical terrain in Liaoning province.And the spatial distribution of the above two schemes has regional characteristics.Among them, scheme 7 works for the towers on plains and hills in northern Liaoning province and also for towers on coastal plains and hills in southeastern Liaoning province.Scheme 3 is chosen for those on hills and mountains in western Liaoning province, schemes 1 and 4 are only applicable to the towers on the remaining areas.The seasonal wind speed variation and inherent topographical characteristics in temperate continental monsoon climate zone and their influence on wind shear index are the main causes of the spatial distribution characteristics of the optimal scheme for the reconstruction of missing data of wind towers on typical terrain in Liaoning province. Figures and Tables | References | Related Articles | Metrics

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Definition and characteristics analysis of the intensity of Northeast Cold Vortex Peng-yu HU, Chuan-lei CHEN, Hai-feng LIN, Shuang XU, Ling-jun KONG, Qing LIU, Yong-ming JI, Zi-qi ZHAO 2021, 37 (6):  100-105.  doi: 10.3969/j.issn.1673-503X.2021.06.013 Abstract ( 286 )   HTML ( 9 )   PDF (1946KB) ( 513 )   Save Using the NCEP 1°×1° grid reanalysis data, according to the characteristics of temperature field having a cold center and the height field being a closed annular circulation of the Northeast Cold Vortex, two indexes of geopotential height difference and temperature difference were selected to formulate the definition method of the daily intensity of Northeast Cold Vortex and analyze the change characteristics of the Northeast Cold Vortex with different intensities divided by this definition.The results show that the occurrence frequency of medium-strength cold vortices is the highest, accounting for more than 50% of the annual number of days of cold vortices, followed by weak cold vortices, and the number of days of super-strong cold vortices is the least.The life history of weak cold vortices is about 3 days.During the super cold vortex activity, the center displacement changes greatly, and the life history is long, and the range of influence is wider. Figures and Tables | References | Related Articles | Metrics

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Evaluation of climate suitability for summer tourism in mountain land of Lishui Hao-min WU, Yan-min JIANG, Bo SI, Yun-xia BAI 2021, 37 (6):  106-112.  doi: 10.3969/j.issn.1673-503X.2021.06.014 Abstract ( 173 )   HTML ( 13 )   PDF (1928KB) ( 173 )   Save This study provided the classifications of the climate suitability of summer tourism in Lishui.The procedures include three parts, i.e.the temporal and spatial distribution of climate suitability for summer tourism was analyzed based on the industry standard of evaluation method of climate suitability for summer tourism designed by the China Meteorological Administration and the daily and hourly data from 283 meteorological observation stations in Lishui during 2015 to 2019;using GIS platform established a geographic estimation model for climate suitability for summer tourism under different terrain conditions; the climatic suitability of summer tourism in Lishui was divided using this geographic estimation model.The results show that the climate suitability grade for summer tourism in Lishui is very suitable, accounting for absolute proportion in the area.In June, the suitability of stations in Lishui is very suitable.At the altitude of 800 m, the suitability first increases and then decreases as the altitude increases.In July and August, the climate suitability for summer tourism increases with the increase in altitude.The stations above 300 m are in more suitable grade or above.The result from geographic estimation model shows that the climate suitability for summer tourism in Lishui is closely related to altitude.The proportion of areas with suitable grade and above in Qingyuan is the highest where the weather conditions for summer tourism are particularly excellent.Jingning, Suichang, and Longquan are followed in turn. Figures and Tables | References | Related Articles | Metrics