KEYWORDS: Humidity, Temperature metrology, Climatology, Environmental sensing, Climate change, Lithium, Meteorology, Information science, Information technology, Analytical research
According to the analysis to the climatic data of Xiao Tang in desert, Lun Tai in oasis during 1992 to 1997, the following viewpoints were noted: (1)The air temperature of desert is lower than the one of oasis in winter, the air temperature rise gradually from oasis to desert in summer. The diurnal range and annual range of air temperature in desert is wide than the one in oasis. (2)The precipitation of oasis is more than the precipitation of desert. The difference of seasonal precipitation is great in desert, the most of precipitation is in warm period, it is basic characteristics that mean-square diviations of precipitation are big in desert. Not only large-scale weather system affects the precipitation in desert, but also violent local thermal circulation can form the local unstable precipitation in desert. (3)The Humidity of desert is lower than humidity of oasis and the evaporation amount of desert is bigger than evaporation amount of oasis. The evaporation capableness of desert is mighty, the difference of seasonal evaporation amount is great in desert and the 77% of annual mean evaporation amount is in summer and spring.(4)The days of sand blown by wind weather in desert are more than the one of oasis. The wind speed in desert is faster than the one of oasis. These indicate that the difference is apparent between desert and oasis. This is caused by differences of Landscape and water amount. The exploitation and utilization on oasis enlarge this difference.
To sum up, the conclusions about the characteristics of the sand-surface reflectivities of visible light channel and near infrared channel in the Tazhong region in the hinterland of the Taklimakan Desert in winter are as following:(1) On fine days, the sand-surface average reflectivities of visible light channel and near infrared channel in the Tazhong region are 25.8% and 28.6% respectively. It is roughly estimated that the atmosphere can reduce the reflectivities of these two channels for 5.2% and 7.5% respectively comparing with the RS data of NOAA satellite in the corresponding period.(2) On fine days, the reflectivities of visible light channel and near infrared channel have the following characteristics: 1. At all the positions of a dune, the reflectivity of near infrared channel is higher than that of visible light channel, and 4.3% higher in maximum on the sand-falling slope and the left wing of dune; 2. Among the different positions of a dune, the reflectivity change of visible light channel is low but that of near infrared channel is high, and the latter is about 5 times of the former: 3. The reflectivities of both visible light channel and near infrared channel on the south-facing slopes are slightly higher than that on the north-facing slopes.(3) The reflectivities of visible light channel and near infrared channel are the highest on cloudy days comparing with that on fine days and thin-cloudy days; from the fine days to the thin-cloudy days and cloudy days, the green values, reflectivity difference between the near infrared channel and visible light channel of dunes, and the maximum reflectivity difference of near infrared channel between the different dune positions are successively reduced; but the maximum reflectivity difference of visible light channel between the different dune positions are gradually increased.(4) On fine days, the dune reflectivities of visible light channel and near infrared channel are reduced with the increase of sun's altitude, but the negative correlation between the reflectivity of visible light channel and the sun's altitude is higher than that between the reflectivity of near infrared channel and the sun's altitude.(5) Frost on sand surface can increase the reflectivities of visible light channel and near infrared channel, and increase for 2.6% and 3.5% respectively compared with that without frost.
In this paper, the characteristics of climate change in the west Tianshan Mountains for last 40 years are discussed. The trend of climate change and its effect combined with the oasis climate effect in the irrigated areas are analyzed. The regional characteristics of climate change and the temporal and spatial distribution characteristics of sand-dust storms, floating dusts and strong winds are compared and analyzed based on the observed data collected from 14 meteorological stations in the source stream area of Aksu River, Aksu Irrigated Area and Yarkant River Irrigated Area during the period of 1961-2000. We concluded that both temperature and precipitation have increased in these regions since 1990’s. It is observed with higher precipitation in the area of Aksu River there are fewer days when sand-dust storms, floating dusts and strong winds happened. The interaction between the climate change and the oasis development is also discussed.
Using the observations from 8 weather stations in northern Xinjiang, eight weather stations in southern Xinjiang and 8 weather stations in Tianshan Mountains area, we analyzed changing features of sandstorm, floating dust, blowing-sand. The observations were collected from 1961-2000 in Xinjiang, China. The results show that southern Xinjiang was the area where sandstorm and blowing-sand occurred more often, and the occurrence was 3-5 times higher than those in northern Xinjiang. Days of floating-dust appearing in southern Xinjiang were 50 times more than those in northern Xinjiang; in Tianshan Mountains area sand-dust weather appeared less. In the last 40 years, the long-term change trend of these sand-dust weather in southern Xinjiang was similar to those in northern Xinjiang, that had been obviously decreasing since the 1990’s; the total days of sand-dust weather in southern Xinjiang in spring had a linear relationship with air temperature and precipitation of the same period, respectively.
Fractional vegetation cover data (FVC) based on the annual maximum NOAA/AVHRR NDVI (Advanced Very High Resolution Radiometer normalized difference vegetation index) data and the ground meteorological data have been used to analyze the relationship between the temporal and spatial evolution of ecological landscape pattern and climate change in Xinjiang autonomous region, China from 1982 to 1993. It is found that during this period, the averaged oasis cropland or low-damp forest-shrub meadow occupies 7.50% of the whole region, desert dune/barren desert 25.70%; temperate semi-arbor desert 21.70%; temperate shrub and semi-shrub desert 8.36%; alpine subalpine desert steppe 7.71%; temperature gramineous and ruderal steppe 7.63%; mountain forest steppe 2.13%; high-cold barren 8.93%; high-cold low semi-shrub desert 9.08%; water/ice 1.26%. Compared with the 30-year (1961-1990) climatology, the 12-year averaged annual surface air temperature and precipitation does not incur over the mountain region; instead it occurs over the region with a concentrated distribution of oases, suggesting the positive role of oases in adjusting regional climate. The area of temporal steppe also increases with the increase of precipitation and temperature. Together, these results demonstrate that, during the 12-year period, the condition of vegetation cover has been improved and large-scale desertification does not occur in Xinjiang.
The water area of the Ebinur, Bosten and Aydingkol lakes, the main lakes in Xinjiang, China, during the period of 1999~2002 is dynamically monitored by using the data of American NOAA and EOS global observation satellites and Chinese FY-1C meteorological satellite. The monthly water areas of the lakes during the period from March to October are calculated, the change characteristics of the water areas of the lakes in the watery and dry seasons and the intermonthly change characteristics are preliminarily understood. The results show that the watery seasons of the Ebinur, Bosten and Aydingkol lakes are the periods from November to April, from December to March, and from January to April, and their dry seasons are the periods from May to October, from April to October and from May to November, respectively. The factors influencing the water area of Ebinur Lake are analyzed by combining the climatic factors. The results show that, except the artificial water consumption, the factors directly influencing the water area of Ebinur Lake are mainly the depth of snow cover on the riparian areas in winter, seasonal precipitation, evaporation and sunshine duration. The strong winds from Alataw Mountain Pass impact seriously the ecological environment in the Ebinur Lake region and its basin. Some practical and effective measures should be taken for controlling the sand drift and for protecting the environment of the lacustrine wetlands in the arid areas.
After analyzing the heat conditions in the years of serious reduction of cotton yield in the main cotton-growing areas of Xinjiang, it is found that the cold disasters, especially the delaying cold disasters, are the most serious meteorological disasters to the cotton production in Xinjiang.
In the paper, the three outstanding features of climate change in Xinjiang for the recent 40 years are identified. Their causes are discussed primarily from two aspects of natural change and factitious influence. Results are as follows: (1)The warming trend of winter mean temperature in northern and southern Xinjiang are resulted from the controlling of macroclimate regularities of winter warming in The Northern Hemisphere and the local influence of factitious factors, the former is more important than the latter. (2)The increasing trend of summer precipitation in southern Xinjiang may have little to do with the change of macroclimate background, but mainly have to do with human activities, especially with increasing of real evaporation in oasis area, which are result from both the area under cultivation (or oasis) enlarging continually in southern Xinjiang between the south foot of Tianshan Mountains and the north foot of Kunlun Mountains and the amount of drawing water from Tarim River increasing continually. Furthermore, the warming trend of summer in southern Xinjiang for the recent 40 years coinciding with The Northern Hemisphere also helps to increase evaporation intensity, to form the increasing trend of real evaporation amount, and results in the increase of summer precipitation. But this is less important than the increase of available evaporation water amount and evaporation area that result from the acreage under cultivation (or oasis) enlarging. (3)The variability of annual mean temperature in Tianshan Mountainous area is the greatest, which maybe have to do with that the annul difference of early or later of forming or smelting, thick or thin and cover extent of seasonal stable snow is largely in the area.
The relationship between the change of stream flow and the human activities in the Tarim River watershed is investigated based on the observed data collected by 13 meteorological stations from 1961 to 2000 and 8 hydrologic stations in the watershed. It is preliminarily attempted to quantify the impact intensity of the human activities. The influence index of water consumption is put forward, and the impact trend of human activities to the mainstream of Tarim River is analyzed. It is considered that the increase amplitude of the impact of human activities was the highest during the period from the 1970s to the mid-1980s, and the increase amplitude of human activities has been slowed down to some extent during the recent 10 years. Moreover, the temporal and spatial distribution characteristics of the climate change, sand-dust storms, floating dusts and strong winds in all the areas of the source streams and the mainstream of Tarim River are compared and analyzed. It is pointed out that the precipitation in the Tarim River watershed has increased since the 1990s, especially in the areas of its main source streams, and the occurring days of sand-dust storms, floating dusts and strong winds have obviously reduced. The possible relationship between the climate change and the human activities is also discussed.
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