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30 October 2021, Volume 37 Issue 5 Previous Issue    Next Issue

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Characteristics and cause analysis of a local explosive fog in north Tibet Zhuo-ma DANZENG, Jie-bu WANGDUI, Qiu-lu SANG, Ze-ren DAWA, Dol-ma DAN 2021, 37 (5):  1-7.  doi: 10.3969/j.issn.1673-503X.2021.05.001 Abstract ( 259 )   HTML ( 13 )   PDF (2243KB) ( 130 )   Save Based on the conventional meteorological observation data in Seni district of Nagqu, combined with the NCEP (National Center for Environmental Prediction, 1°×1°) and Era5 (0.25°×0.25°) reanalysis data, the formation mechanism, physical structure characteristics, and the cause of local occurrence of thick fog in north Tibet on April 10, 2019, were diagnosed and analyzed from the perspective of synopology. The results show that the fog is characterized by local outbreaks. The evaporation of water vapor from the melting snow in the early stage cooperated with the wind field is helpful to the formation of the fog. The 500 hPa circulation background configured with warm advection on the upper layer and cold advection on the lower layer in the boundary layer are involved in the formation of the fog so that the fog can be developed and maintained. There are fewer clouds at night, and the net radiation on the surface is strengthened. Strong net radiation on the ground, and a cooling effect leading to the saturation of water vapor, which is conducive to condense water vapor and form countless small droplets suspended in the air. The low wind speed, inverse temperature, and sinking motion in near formation make water vapor difficult to diffuse into the upper air, so large number of water vapor converges in a relatively limited space, leading to the explosive development of fog. The locality of fog is closely related to the special terrain. Figures and Tables | References | Related Articles | Metrics

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Analysis of the characteristics and influencing factors of a persistent fog and haze weather process in Dongli District, Tianjin Jun SHI, Yu-jie ZHAO 2021, 37 (5):  8-12.  doi: 10.3969/j.issn.1673-503X.2021.05.002 Abstract ( 243 )   HTML ( 13 )   PDF (1636KB) ( 151 )   Save Based on conventional meteorological observation data and PM2.5 concentration data, the characteristics and causes of persistent fog and haze weather occurring from January 10 to 14, 2019, in Dongli District of Tianjin were analyzed. The results show that the fog and haze weather has obvious phase characteristics. The general circulation, including upper-level straight stable westerly circulation, middle-level warm ridge, and weakened surface pressure, provides favorable synoptic conditions for the fog and haze weather. Visibility is more susceptible to relative humidity during light fog and haze stages, while at the fog stage, it is more susceptible to wind speed. PM2.5 concentration and surface meteorological elements are closely related. PM2.5 concentration is negatively correlated with visibility and wind speed and positively correlated with relative humidity. When other meteorological conditions are stable and the concentration of pollutants is high in the surrounding areas, the change of wind direction near the ground plays a key role in the occurrence of fog and haze in this regiony. Figures and Tables | References | Related Articles | Metrics

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Analysis of aerosol concentration variation and weather characteristics of heavy pollution events in northeast China Yan-jun MA, Hu-jia ZHAO, Yu-fei LIU, Xiao-lan LI, Yang-feng WANG, Yun-hai ZHANG, Ye HONG 2021, 37 (5):  13-19.  doi: 10.3969/j.issn.1673-503X.2021.05.003 Abstract ( 250 )   HTML ( 6 )   PDF (2061KB) ( 152 )   Save Based on the data of air quality in cities in northeast China and the weather situation from 2014 to 2017, the changes in air pollution in Northeast China and the distribution characteristics of heavy pollution weather situation were analyzed. The results show that from 2015 to 2017, the annual average mass concentrations of PM2.5 and PM10 in Northeast China demonstrate a decreasing trend, and the annual average mass concentration of PM2.5 decreases faster. The maximum value of PM2.5 is about 90-100 μg·m-3 in central Liaoning and Jilin provinces. The average annual mass concentration of SO2 is about 50 μg·m-3 in the western Liaoning province, while the maximum value of NO2 is about 45 μg·m-3 in the Shenyang-Changchun-Harbin area, and the maximum value of CO mass concentration is about 1.6 mg·m-3 in the northeast coastal area. On the other hand, the average annual mass concentration of O3 in Northeast China is increasing. The maximum value is about 100 μg·m-3 in Dalian and Yingkou cities. The maximum values of PM2.5, PM10, and AQI in different areas all appear in winter. The maximum values of SO2 mass concentration in winter appear in Shenyang city with 180 μg·m-3. The maximum values of NO2 and CO in winter appear in Harbin city with 80 μg·m-3 and 1.8 mg·m-3, respectively. The maximum value of O3 is about 140-150 μg·m-3 in summer in Shenyang city. The air quality with severe (200 μg·m-3 ≤ PM2.5 < 300μg·m-3) and more severe (PM2.5>300 μg·m-3) pollution levels show the characteristics of a rapid decrease around Harbin city, and a slight increase in the central Liaoning province. The cities with moderate pollution (150 μg·m-3 ≤ PM2.5 < 200 μg·m-3) days in descending order are Shenyang, Harbin, and Changchun, and with light pollution (100 μg·m-3 ≤ PM2.5 < 150 μg·m-3) in descending order days are Shenyang, Changchun, and Harbin. The weather conditions causing heavy pollution in Northeast China can be divided into three types: high-pressure type, low-pressure type, and high in the north and low in the south type, with the proportion of 62%, 27%, and 11%, respectively. For the high-pressure type, the high-pressure ridge at 850 hPa moves east over Northeast China, and the near ground is in the south or weak high-pressure center. Sometimes in the north of Heilongjiang province or southwest of Liaoning province, a weak low pressure is continuously generated and rapidly moved eastward. For the low-pressure type, the low-pressure system at 850 hPa develops and moves eastward through Northeast China, and the near ground is in a weak high pressure after a low pressure. For the high in north and low in south type, the Northeast region is influenced by both North high pressure and South low pressure at 850 hPa and the near ground. Figures and Tables | References | Related Articles | Metrics

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Analysis of PM2.5 concentration changes and transmission characteristics in Huzhou city Hao YIN, Jun-ling TAN, Ju-yong WANG, Hong-quan LI, Lei XI, Bin WU, Ji-dong QIU 2021, 37 (5):  20-26.  doi: 10.3969/j.issn.1673-503X.2021.05.004 Abstract ( 205 )   HTML ( 7 )   PDF (2125KB) ( 159 )   Save Based on the National Air Quality Index (AQI), PM2.5 mass concentration data, Global Data Assimilation System (GDAS) meteorological data from 2014 to 2018, and the backward trajectory model, the characteristics of PM2.5 concentration changes in Huzhou city were analyzed. Eight heavy pollution processes that occurred in 5 years were screened out for transportation characteristics and potential source analysis. The results show that the frequency distribution of the daily average concentration of PM2.5 in Huzhou city changes exponentially, and the high-frequency area corresponds mainly concentrations between 20-40 μg·m-3. The pollutant mainly occurs in winter, with low concentration values in summer and early autumn. The diurnal variation of the hourly average concentration presents a bimodal distribution, in which the main peak appears at 10 o'clock, the auxiliary peak appears at 2 o'clock, and the valley is at 18 o'clock. The concentration is related to the change of NO2 and SO2. PM2.5 in Huzhou city is mainly transported along the northwest and east path over a medium and long-distance. Among them, the northwest path transportation has a greater impact on the Huzhou area. The air mass in the eastward path passes over the sea surface, and it is fully mixed with the water vapor, which will aggravate the second generation and aging process of the particulate matter. The southwest-by-west and southerly paths also contribute to Huzhou's air pollution, but uncertainty remains, the southerly path appears as a clean passage in individual cases. The urban agglomeration along the northwest route is the main potential source area, and the high-value area is mainly concentrated in the central and western parts of Anhui province. Figures and Tables | References | Related Articles | Metrics

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Ozone pollution and the related effects of meteorological factors in Liaoning province, China Ning-wei LIU, Wei-jun QUAN, Wan-hui REN, Xiao-lan LI, Li-guang LI, Di WANG 2021, 37 (5):  27-33.  doi: 10.3969/j.issn.1673-503X.2021.05.005 Abstract ( 209 )   HTML ( 5 )   PDF (2750KB) ( 231 )   Save We investigated ozone pollution and related meteorological factors in Liaoning province, China using hourly surface ozone concentrations and meteorological observations for the period 2015-2019. The ozone concentrations in Liaoning province appeared to be increasing significantly in all cities, except for several cities around Liaodong Bay. Ozone has taken over PM2.5 as the main pollutant in Liaoning province. Ozone concentrations were high in summer, but low in winter; and high in the afternoon, but low in the morning. In addition to air pollution emissions, high temperature and humidity, intense radiation, low wind speed, and air pressure were the significant meteorological factors influencing the local ozone production. With the influence of the Asian Summer Monsoon, polluted air masses from upwind direction (e. g. North China Plain) under the southwestern wind influenced the air quality over Liaoning province. Figures and Tables | References | Related Articles | Metrics

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Characteristics of dust weather in southern Xinjiang based on hourly data Tulinisha,Da-wei AN,Chao ZHANG,Bi-xin YU,Chun-yan CHEN 2021, 37 (5):  34-40.  doi: 10.3969/j.issn.1673-503X.2021.05.006 Abstract ( 185 )   HTML ( 4 )   PDF (1500KB) ( 162 )   Save Based on the daily observation and hourly automatic station data at 55 national stations in southern Xinjiang from 2006 to 2019, the fine characteristics of dust weather and the threshold velocity on sandstorms were studied. The results indicate that the sand center in southern Xinjiang was located from the central part to the southern edge of Tarim Basin, showing the higher distributions in the central part whereas lower in the eastern and western part. The center of floating dust and sandstorm was in Minfeng whereas that of blowing sand was in Tazhong station. Dust weather had significant seasonal variation. It appeared lest in autumn and winter with floating dust being the main contributor. Whereas it appeared more in spring and summer with floating dust and blowing sand being the main contributor. Seasonal variations in a sandstorm and blowing sand were more significant than those in floating dust. Dust weather appeared more frequently in the daytime, especially in the afternoon, compared with nighttime, during which sandstorms and blowing sand appeared dominantly from 18:00 to 20:00 over southern Xinjiang. Blowing sand and sandstorm lasted shorter with a duration of less than 3 hours and the longest duration appeared in the southeast of Bazhou. The minimum wind velocity triggering dust varied significantly among various areas of southern Xinjiang, while the maximum wind speed appeared higher in the eastern part than in the western part, and higher in the northern part than in the southern part with the lowest values appeared in the central of Tarim Basin. Mean maximum wind speed was higher in spring than in summer with a lower speed difference appeared in the Hetian area. Moreover, the dispersion of the maximum wind speed was higher in spring as well, with the minimum value at each station varying from 1.6 m·s-1 to 9.8 m·s-1. Figures and Tables | References | Related Articles | Metrics

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Comparison of classification methods on atmospheric stability over the coastal areas of Fujian province Xin-qian ZHANG,Long-quan CHEN,Jun-fang ZHANG 2021, 37 (5):  41-48.  doi: 10.3969/j.issn.1673-503X.2021.05.007 Abstract ( 137 )   HTML ( 3 )   PDF (771KB) ( 303 )   Save Meteorological data were obtained by a 100-meter observation tower built in a plant site along with the coastal areas of Fujian province. Using observation data from the tower including wind direction, wind speed, and temperature, along with the total radiation and net radiation from ground observation, atmospheric stability was investigated via solar radiation method, temperature gradient method, temperature gradient-wind speed method, and Richardson number method. The differences in atmospheric stability classification results using the four methods were evaluated considering seasonal variations of stability, diurnal variation for each stability frequency, and stability in various incoming flows. Due to the significant radiation and low wind speed at near-surface levels, the temperature gradient method and Richardson number method appeared more suitable for the atmospheric stability classification in the coastal areas of Fujian province. Figures and Tables | References | Related Articles | Metrics

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Comparison of two filter collection methods in ice nucleus observation De-ping ZHOU, Jin-guang ZHANG, Gang CHEN, Cheng-long LI, Ye HONG, Hang SU, Yang-feng WANG 2021, 37 (5):  49-55.  doi: 10.3969/j.issn.1673-503X.2021.05.008 Abstract ( 116 )   HTML ( 2 )   PDF (711KB) ( 318 )   Save Atmospheric ice nucleus observation is a basic work for studying natural cold cloud precipitation and artificial weather modification, and the filter-diffusion cloud chamber method is one of the main methods for observing ice nucleus concentration. To evaluate the influence of the two filter collection methods on the observation results of ice nuclei, a parallel sampling experiment was carried out from 2011 to 2015 with a self-made atmospheric particulate sampler and an FA-3 impact 9-stage sampler. The results show that despite the ice nucleus concentration observed by the self-made sampler was several times or even tens of times higher than that of the 9-level sampler, they varied simultaneously in various seasons and meteorological conditions. The self-made sampler was suitable for the study on the total ice nucleus concentration distribution and physical/chemical characteristics in the atmosphere, while the 9-level sampler was suitable for the study on the atmospheric ice nucleus concentration, scale distribution, and physical/chemical characteristics of the various particle diameter sections of PM10. The underestimation of the number of ice nuclei by the filter method was proportional to the sampling volume. Changing the pumping flow of the sampler's air pump and controlling the sampling volume had a significant influence on improving the "volume effect". Figures and Tables | References | Related Articles | Metrics

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Calculation of zero plane displacement and dynamic roughness length in Poyang lake area Zhi-juan RAO,Bin ZHU,Ru-liang WANG,Xi-ming LIU 2021, 37 (5):  56-62.  doi: 10.3969/j.issn.1673-503X.2021.05.009 Abstract ( 149 )   HTML ( 3 )   PDF (1132KB) ( 257 )   Save Based on the eddy correlation observation data of the 70-m tower on the east bank of Poyang lake from July 1, 2013 to June 30, 2014, the surface zero plane displacement and roughness length were calculated with the Martano method and TVM method (Temperature Variance Method). The friction velocity calculated by substituting the wind profile relation based on Monin-Obukhov similarity theory was compared with the observation for verifying their consistency. The results show that the normalized fitted curves of velocity and temperature standard deviations show a similar trend with the theoretical curves given by Panosky et al. and Tillman. The results calculated with the Martano method vary greatly with the season, and the roughness in spring and summer is 6.3 times larger than that in autumn and winter. The zero plane displacement and roughness for land surface are 2 times and 10 times larger than those for lake surface, respectively. Martano method is more sensitive to the season and direction relative to the TVM method. The friction velocity estimated with the Martano method causes about 9.9% overestimation for the friction velocity, while that with the TVM method results in an overestimation of about 32.8%. On the whole, it can be seen that the friction velocity calculated by the Martano method is better consistent with the observed value. Figures and Tables | References | Related Articles | Metrics

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Analysis of spatio-temporal variation characteristics and atmospheric circulation factors of precipitation in early and mid-summer in Northeast China Yi-tong LIN, Chun-yu ZHAO, Yi-he FANG, Qian LI, Xiao FANG, Xuan LI, Lin-lin SUN, Rong LIN 2021, 37 (5):  63-71.  doi: 10.3969/j.issn.1673-503X.2021.05.010 Abstract ( 276 )   HTML ( 5 )   PDF (4378KB) ( 215 )   Save Based on the daily precipitation data of 245 weather stations in Northeast China from 1961 to 2019, the temporal and spatial characteristics of precipitation in early summer (June) and mid-summer (July and August) in Northeast China were analyzed using EOF, cumulative anomaly, moving t-test, Wavelet analysis, and correlation analysis methods. The results show that precipitation in mid-summer in Northeast China are mainly concentrated in the southeast, and more precipitation is distributed in the north and northeast in early summer. The first and fourth modes of EOF in early and mid-summer are consistent across the whole area and feature a change of negative-positive-negative (positive-negative-positive) from north to south, respectively. There are two abrupt changes of precipitation in early summer in 1972 and 1995 and three abrupt changes in mid-summer precipitation in 1966, 1983, and 1998, respectively. There are prominent quasi-6-year and quasi-3-year oscillation periods in mid-summer precipitation in northeast China from the 1980s to 1990s and late 1990s, respectively. The main oscillation period of midsummer precipitation is about 12 years, and the interannual scale oscillation period for 3-4 years appears after the 1990s. With investigating the characteristics of circulation field related to precipitation on time division, it is found that the influence of Northeast Cold Vortex on the precipitation in early summer is enhanced, and the impact factors of precipitation in mid-summer transforms from the Western Pacific subtropical high to the mid-latitude westerlies system, indicating a new characteristic. Figures and Tables | References | Related Articles | Metrics

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Change of Qixiangco lake area and its reasons in Naqu city from 1988 to 2018 Ba LA,Duo BIAN,Duo-ji DUNYU,Mei YANG,Wei-hua ZHANG,Ren-zeng BAIMA 2021, 37 (5):  72-77.  doi: 10.3969/j.issn.1673-503X.2021.05.011 Abstract ( 189 )   HTML ( 4 )   PDF (3559KB) ( 132 )   Save Based on Landsat satellite remote sensing data, the water body index and correlation analysis methods were used to analyze the water area change of Qixiangco lake in Shuanghu county of Naqu city from 1988 to 2018. The results showed that the water area of the lake increased significantly by 33.37 km2 in the recent 31 years (R=0.88, P < 0.001) with a rate of 18.03%. In terms of space, the lake area expanded continuously around in the past 31 years, especially in the east, the west, and the north. In addition, the annual average temperature in the region where the lake is located increased, the evaporation capacity significantly reduced, and the frozen soil depth was also significantly reduced. Under the combined action of the above factors, the increase of lake water supply source and lake water volume lead to the continuous increase of lake area. Figures and Tables | References | Related Articles | Metrics

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Intensity formula and design hyetograph for long-duration storm in Xiong'an New District Chang-wen YU,Qi-hui XU,Yi-chang YANG,Gui-dong MA,Xu-xu GAO 2021, 37 (5):  78-85.  doi: 10.3969/j.issn.1673-503X.2021.05.012 Abstract ( 983 )   HTML ( 13 )   PDF (1672KB) ( 194 )   Save Design rainstorm research is an important foundation for urban drainage and waterlogging prevention engineering construction. The temporal variation characteristics of the number of precipitation and rainstorm days were analyzed based on the precipitation data of meteorological stations in Xiong'an New District from 1981 to 2020. Taking Xiong county as an example, using its minute-level rainfall data, through the annual maximum value method, the theoretical frequency analysis of rainfall data was carried out using P-III curve in order to consider the fitting goodness of long and short duration rainfall data. The parameters of formula were solved by Gauss-Newton method and the long-duration comprehensive storm intensity formula that suitable for 5-1440 min was obtained. On this basis, the design hyetograph for 1440 min in Xiong county was deduced using homogenous frequency analysis method. The results show that multi-year averaged rainfall in Xiong'an New District is 490.4 mm; the number of storm days is 4.4 d; the number of storm days shows an increasing trend from 2000 to 2020, especially for the number of torrential rain days. In recent 10 years, the proportion of the number of torrential rain days to storm days was the largest (20.8%) in the new district, which was nearly 7 times larger than that at the beginning of the 21st century. The obtained long-duration comprehensive storm intensity formula of Xiong county could be used to calculate the design storm of whatever duration (5-1440 min) and whatever recurrence period (2-100 years). The 1440 min' design hyetograph with an interval of 5 min in Xiong county shows a single peak with the peak value is 0.806. Combined the design hyetograph with the obtained long-duration comprehensive storm intensity formula, the designed rain patttern of 1440 min under different specified recurrence period could be deduced. Figures and Tables | References | Related Articles | Metrics

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Impact of soil water stress from pod filling to maturity on seed setting and yield of spring soybean Xiu-fen LI,Shu-qing MA,Hai YU,Li-ping XU,Feng-tao CHEN,Li-juan GONG 2021, 37 (5):  86-92.  doi: 10.3969/j.issn.1673-503X.2021.05.013 Abstract ( 127 )   HTML ( 1 )   PDF (1296KB) ( 180 )   Save In order to clarify the effect of drought in late growth on yield formation of spring soybean, and to provide the scientific basis for summer-autumn drought assessment and drought control irrigation, soil moisture control experiments consisting of seven soil moisture levels and one natural rain-fed treatment from pod filling to maturity were carried out in central Jilin province in 2017 and 2018, and soil moisture, pod bearing rate, empty-chaff pod rate, grain weight and yield were observed. The effects of soil moisture on soybean yield were analyzed by the regression method. The results showed that under the field capacity, the grain weight and yield of soybean are linearly positively correlated with the soil moisture during the period of pod filling to maturity, and the number of soybean pod bearing and the relative empty-chaff pod rate and the soil moisture are related in quadratic function. If the soil moisture during pod filling to maturity in 0-30 cm soil depth decreases by 1 percentage point, the number of soybean pods and the number of effective pods decrease by 3.1 and 3.7 percentage points respectively, and the relative 100-kernel weight and relative yield per unit area decrease by 0.8 and 1.5 percentage points respectively, and the empty pod rate increases by 9.3 percentage points. In this period, soybean likes water but has strong drought tolerance. Soil moisture between 22% and 23% is beneficial to reducing empty-chaff pod rate, and increasing pod number, grain weight, and yield. The soil relative humidity indexes for light, moderate, severe drought and extreme drought are 66%-75%, 57%-65%, 50%-56% and below 50%, respectively, and the corresponding yield reduction rates are 5%-10%, 11%-15%, 16%-20% and more than 20% respectively. Compared with the previous indexes, the indexes of severe and extreme drought in this experiment are significantly higher than wilting humidity, which is more in line with the physiological law of soybean water demand and can be used for quantitative assessment of drought effects on spring soybean during the period of filling and ripening. Figures and Tables | References | Related Articles | Metrics

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MCI-based climatic characteristics of drought in Fujian province Yao ZHUANG, Rui-juan BAO, Rong-yan ZHANG, Jin-hai HE, Lan WANG 2021, 37 (5):  93-99.  doi: 10.3969/j.issn.1673-503X.2021.05.014 Abstract ( 235 )   HTML ( 8 )   PDF (1917KB) ( 487 )   Save Based on the meteorological drought composite index (MCI) that was implemented in the national drought monitoring operation system currently, the characteristics of dry and wet conditions and variations of a drought of 66 meteorological stations in Fujian province in the past 59 years were analyzed using Morlet wavelet and empirical orthogonal function (EOF) methods. The results show that Fujian has obvious climatic characteristics of wet and dry seasons with significant periodic oscillations of 6-8 years and 22 years. The variation of wet and dry seasons' period in mountainous inland areas is longer than that in coastal areas. At seasonal scale, each season is featured by multiple time scales and regional differences. The spatial variation has three typical modes, which reflect the differences in monsoon rainfall amount and topography. The spatial and temporal distribution of drought processes expressed by MCI is consistent with historical drought events. Autumn and winter (spring and summer) are the seasons with the highest drought frequency (strongest drought intensity) in Fujian province. The occurrence probability of drought processes in coastal areas at the south of Minjiang River Estuary is significantly higher than that in inland areas, and the occurrence probability of synchronous drought in the whole province is relatively less (12%). Figures and Tables | References | Related Articles | Metrics

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Quantitative assessment on climate carrying capacity of a mountainous city from 2000 to 2017: a case study of Baise city Yan-jun LI,Jie-lin HE,Chuan QIN,Wei-hua MO,Jian-fei MO 2021, 37 (5):  100-106.  doi: 10.3969/j.issn.1673-503X.2021.05.015 Abstract ( 120 )   HTML ( 7 )   PDF (818KB) ( 318 )   Save Based on the meteorological and urban socio-economic data from 2000 to 2017, a comprehensive function of urban climate carrying capacity was constructed to evaluate objectively and quantitatively the variation of climate carrying capacity of Baise city, a mountainous city in Western Guangxi. The function consists of four evaluation indexes, namely, climate natural capacity, extreme climate event, urban climate pressure, and urban coordinated ability. The results show that since the 21st century, the overall climate carrying capacity of Baise city has shown an increasing trend with fluctuation, which reflecting an enhanced coordination ability between urban construction and climate, and there is still a large climate carrying space for urban construction. Climate carrying capacity is sensitive to extreme climate events, especially extreme drought. Human impact factors have important influences on climate carrying capacity. Improving climate carrying capacity and coping with climate change should improve the ability to defend against natural disasters and the ability of urban coordinated development, as well as reducing urban climate pressure so that a sustainable urban climate ecosystem in Baise city can be built. Figures and Tables | References | Related Articles | Metrics

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Temporal and spatial evolution of NPP and its responses to terrain factors in Liaoning province Yu-hong LI,Su-lin TAO,Rong-ping LI,Ting WANG,Bin ZHOU,Jing LI,Dong-ming LIU 2021, 37 (5):  107-112.  doi: 10.3969/j.issn.1673-503X.2021.05.016 Abstract ( 134 )   HTML ( 2 )   PDF (1805KB) ( 106 )   Save Vegetation net primary productivity (NPP) is one of the most important indicators for assessing the quality of the ecological environment. In order to detect the changes of the ecological environment in Liaoning province, the MODIS-NDVI data and CASA model were used to estimate the NPP in Liaoning province from 2000 to 2018. Based on the estimated NPP, the temporal and spatial characteristics of NPP in Liaoning province and the relationships between NPP and topographic factors in the past 19 years were analyzed. The results show that vegetation NPP has a fluctuating upward trend in Liaoning province from 2000 to 2018, and the spatial distribution characteristics show that NPP in the east is higher than that in the west. The trend rate of NPP is 2.89 g C·m-2·a-1. The statistic shows that 87.4% of the areas have an increasing trend in NPP, and the fluctuations in northwestern Liaoning province are the most obvious. Elevation and slope have a more obvious impact than slope direction on the change of NPP. With the increase of elevation, NPP shows an increasing trend at first and then keeps stable, and the maximum NPP is at an elevation of 500 m. As the slope increases, NPP shows an increasing trend first and then decreasing slightly with the highest value was obtained in the lands of slope at 35°. The NPP value is the largest when the elevation is above 500 m and the slope is within the range of 15° to 35°. Figures and Tables | References | Related Articles | Metrics