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15 November 2018, Volume 35 Issue 6 Previous Issue    Next Issue

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Effect of ecological water conveyance on vegetation coverage in surrounding area of the Qingtu Lake ZHAO Jun, YANG Jian-xia, ZHU Guo-feng 2018, 35 (6):  1251-1261.  doi: 10.13866/j.azr.2018.06.01 Abstract ( 778 )   PDF (4143KB) ( 587 )   Ecological water conveyance is an effective way to alleviate ecological problems in the form of human intervention to regenerate the degenerated ecology, and it is applied in the surrounding area of the Qingtu Lake, the tail-end lake of the Shiyang River in Minqin County, Gansu Province. The effect of ecological water conveyance on the ecology and environment in the region has attracted much attention. In this paper, the inversion of vegetation coverage (FVC) was reconstructed using the Landsat images in the surrounding area of the Qingtu Lake during the period from 1987 to 2016. The characteristics of the overall dynamic change of FVC were firstly explored, and then the relationship between such change and the ecological water conveyance was analyzed. The results showed that the average vegetation coverage in the surrounding area of the Qingtu Lake was increased from about 10% to 20% in the past 30 years. The change trend of vegetation coverage before and after 2010 was obviously different. The trend analysis was used to compare the characteristics of vegetation cover before and after the ecological water conveyance in September 2010, and the results showed that the effect of climate change on the vegetation coverage in the study area was slight although climate change was the main factor affecting the large-scale vegetation coverage. The vegetation coverage was mainly increased in the area near the lake, and the ecological water conveyance was the main factor affecting its increase. The change of annual vegetation coverage before the ecological water conveyance in 2010 was not obvious, but after that it was in a significant increase trend. References | Related Articles | Metrics

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Health Assessment of the Yarkant River Based on Harmonious Development Degree Model HE Bing, GAO Fan, TANG Xiao-yu, QIN Shan 2018, 35 (6):  1262-1270.  doi: 10.13866/j.azr.2018.06.02 Abstract ( 763 )   PDF (1628KB) ( 417 )   It is very important for the ecological hydrological conservation and river adaptability management in arid inland river basins to determine and evaluate the factors affecting the river health and its change. The river section from Kaqung to Ayriktam of the Yarkant River was considered to be typical, the river health evaluation index system was set up with 23 indexes based on the pressure state response model, and the river health evaluation standards were put forward. On which the theory of coordinated development degree was introduced for assessing the river health, the river health evaluation model was established based on the coordinated development degree, the standard level of the coordinated development evaluation was established and divided, and the river health in 2015 was evaluated and analyzed. The results revealed that the coordinated development index along the river section Dtotal=0.495, the comprehensive evaluation index Ttotal=0.537, the type of coordinated development belonged to the “slightly uncoordinated type”, and the health status belonged to the “sub-health” level. These revealed that the health of the river was threatened. At the aspect of comprehensive river management in the future, the coordinated development level of stress-state-response factors should be improved, and the corresponding index level under restoration response factors should be dominant. References | Related Articles | Metrics

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Energy Balance During Three Snow Cover Processes at Maqu in the Headwaters of the Yellow River LI Dan-hua, WEN Li-juan, LONG Xiao, CHEN Shi-qiang, LIU Wei-ping, LU Guo-yang 2018, 35 (6):  1327-1335.  doi: 10.13866/j.azr.2018.06.09 Abstract ( 663 )   PDF (2162KB) ( 488 )   In this study, the meteorological data observed at Maqu Station for Climate and Environment Integrated Research, Chinese Academy of Sciences during the period from December 2011 to March 2012 were used. The purposes of the study were to compare and analyze the surface radiation and energy balance in three snow cover processes under the different conditions of soil freezing and thawing as well meteorological conditions in the headwaters of the Yellow River. The results showed that the net radiation was decreased significantly after snowfall, and the net radiations before and after snowfall were 154, 200 and 210 W·m-2 and 93, 129 and 130 W·m-2 respectively. After three times of snowfall and snowmelt, the ground-air energy exchange was strongly affected by weather conditions and soil freezing and thawing: after the first snowfall, the low temperature and land surface temperature did not affect the weak evaporation capacity of frozen soil, the latent heat flux and its difference before and after snowfall and snowmelt were low. On February 18 after second snowfall, the high wind speed (≥ 4 m·s-1) and strong solar radiation accelerated the sublimation of snow cover, the latent heat flux was high with a daily average of 118 W·m-2, the wind speed and latent heat flux changed synchronously, and their peak values of 15m·s-1 and 300 W·m-2 occurred simultaneously. The sublimation energy consumption of snow cover reduced the surface temperature and was lower than the air temperature, and a negative sensible heat flux occurred with a daily average of -8 W·m-2 and a peak value of -40 W·m-2. After snowmelt, the latent heat flux and sensible heat flux reached their levels before snowfall. During the period from February 29 to March 3 after the third time of snowfall, the shallow soil temperature was gradually increased from -1 ℃ and maintained at -0.18 ℃, the frozen soil absorbed heat, the increase of latent heat flux was not significant compared with that before snowfall. March 4 was the last day of snowmelt, latent heat was released from damp soil and snowmelt water evaporation, the latent heat flux was increased significantly compared with that on March 3. After snowmelt, the effect of shallow soil evaporation capacity on the latent heat flux was increased significantly compared with that before snowfall. References | Related Articles | Metrics

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Correlation Between Sunspot Activity and Precipitation in the Ankang Region in Recent 63 Years ZHANG Bei-bei, WANG Peng, ZHANG Hui, WU Yue-xuan, WANG Miao-miao 2018, 35 (6):  1336-1343.  doi: 10.13866/j.azr.2018.06.10 Abstract ( 581 )   PDF (2684KB) ( 581 )   In this study, the Mann-Kendall test and Morlet wavelet analysis were used to lucubrate the variation of precipitation and its relationship with the relative number of sunspots in the Ankang region in recent 63 years based on the data of relative annual number of sunspots and daily precipitation observed by Ankang Meteorological Station, Ankang Meteorological Bureau during the period of 1953-2015. The results showed that, in the Ankang region, the annual and summer precipitations were significantly increased with increments of 0.99 mm·a-1 and 1.65 mm·a-1 respectively. The spring, autumn and winter precipitations were decreased slightly with reductions of 0.26 mm·a-1, 0.35 mm·a-1 and 0.06 mm·a-1 respectively. Precipitation occurred mainly in summer and autumn. There was  0-3 a time lag of the anomaly of extreme precipitation than the occurrence of peak-valley value of relative sunspot number. There were the significant 3 a and 28a variation periods of annual precipitation in the Ankang region, which was different from the 9 year variation period of relative sunspot number. References | Related Articles | Metrics

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Air Pollution in a Strong Sandstorm in North China JIANG Yu-he1, WANG Shi-gong1, JIN Shuang-long2, FAN Jin1 2018, 35 (6):  1344-1351.  doi: 10.13866/j.azr.2018.06.11 Abstract ( 755 )   PDF (3137KB) ( 653 )   In this study, the routine environmental monitoring of pollutant concentration data, NCEP/NCAR 0.5°×0.5° reanalysis data and conventional meteorological observation data were used. The purpose of the study was to lucubrate the air pollution process of a strong sandstorm in 13 provinces (including autonomous regions and municipalities directly under the central government) in China from May 3 to 6, 2017. The results showed that the average daily concentration of PM10 in the main cities suffering from the sandstorm was increased by 2-10 times relative to the monthly average. The average daily concentration of PM2.5 was increased by 5~8 times relative to the monthly average concentration. During the intense sandstorm, the concentration of particulate matter was in a clear upward trend, and the increase of PM10 concentration was more obvious than that of PM2.5, which indicated that the sandstorm carried a large amount of coarse particle pollutants. On the contrary, during the occurrence of sandstorm, the average daily concentrations of SO2, CO and NO2 were in a decrease trend, which revealed that the sandstorm had a certain effect of diffusing O3. In addition, the locations of the regions with low visibility, high PM10 concentration and 3 h positive pressure were basically accorded with and located in the rear of ground cold front, which could provide a synoptic basis for predicting and preventing sandstorm and its pollution. References | Related Articles | Metrics

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Variation of NDVI and its response to climate change in Hoh Xil during the period of 1982-2015 CHEN Deng-kui, MA Chao, WANG Xia-bing, LIU Chang 2018, 35 (6):  1410-1417.  doi: 10.13866/j.azr.2018.06.18 Abstract ( 709 )   PDF (2128KB) ( 687 )   (1. College of Surveying ＆ Land Information Engineering, Henan Polytechnic University, Jiaozuo 454000, Henan, China; 2. Key Laboratory of State Bureau of Surveying and Mapping of Mine Spatial Information Technology, School of Surveying and Mapping Land Information Engineering, Henan Polytechnic University, Jiaozuo 454000, Henan, China) References | Related Articles | Metrics

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Effect of Barchan Dune on Surface Wind Erosion over Lacustrine Plain CAI Dong-xu, LI Sheng-yu, LEI Jia-qiang, WANG Hai-feng, MENG Xiao-yu 2018, 35 (6):  1496-1504.  doi: 10.13866/j.azr.2018.06.28 Abstract ( 1412 )   PDF (2087KB) ( 587 )   Barchan dune is an important type of aeolian landform and forms during the process of desertification. In the previous researches, more researchers focused mainly on the surface dynamic process of barchan dune but less on the influence of barchan dune on surface wind erosion during desertification process. In this paper, the plugging-brazing method was used to measure the distribution pattern of wind erosion/deposition on the surface around barchan dunes at the Taitema playa. The wind tunnel was used to simulate the distribution pattern of airflow over the typical barchan dune. The mechanism of barchan dune affecting surface wind erosion around dune was analyzed. The results showed that the airflow structure changed with the varying geometry shapes of barchan dunes, and it affected significantly the intensity of wind erosion/deposition over the surface. Although the wind erosion depth and sedimentary thickness were slightly greater than those on flat sand, the average volume of net wind erosion per unit area was close to an equilibrium in the frontal region of windward slope and on both sides of dunes. Deposition was dominant in the frontal region on leeward slope of barchan dune, but wind erosion was dominant on the surface of flank wake zone of leeward slope. The average volume of net wind erosion per unit area was slightly increased with the increase of dune size. In a word, the barchan dunes affect the intensity of surface wind erosion and deposition during the process of desertification in playa. References | Related Articles | Metrics

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CO2 Carbon Flux over Moraine Area of the Koxkar Glacier in the Tianshan Mountains WANG Jian, DING Yong-jian, XU Min, XU Jun-li 2018, 35 (6):  1512-1520.  doi: 10.13866/j.azr.2018.06.30 Abstract ( 530 )   PDF (1892KB) ( 455 )   At some flux sites, the alpine zone surrounding the measuring tower is affected by complex topography and strong wind, which results in the distortion of atmospheric CO2 flux. The goal of this study was to carry out a numerical experiment with the eddy covariance system in moraine area of the Koxkar Glacier in the Tianshan Mountains, and to evaluate the integral of footprint function over the considered domain and distance of the corresponding farthest point from the sensor with the ART (Agroscope Reckenholz Tanikon) Footprint Tool base on the Kormann Meixner method. Results are as follows: ①The prevailing wind direction in snow accumulation period was NW, and its frequency accounted for 53.31%. NW wind evolved gradually into NNW one in snow melting season and early ice-glacial ablation season; ② Atmospheric CO2 sank during the majorly typical period and even snow accumulation period, because soluble substances reacted chemically under snow-ice melting; ③ Temporally, the proportion of more than 80% 0.5h CO2 flux data of footprint function in each period was in an order of > snow accumulation period (95.96%) > snow melting period (93.75%) > intense glacial ablation season (86.30%) > early glacial ablation season (82.35%). The footprint distance to the farthest point was almost in reverse order, which meant that the major areas of CO2 flux contribution were relatively concentrated, and the effect of CO2 flux change at the glacial terminal and on the ridges could be ignored; ④ Under the stable atmosphere in the daytime, the CO2 flux (78.55±2.08)% was slightly higher than that under the unstable atmosphere (77.72±1.41)% at night, but they were significantly lower than the interpretated ones. References | Related Articles | Metrics