基于MODIS影像的四川西部积雪的时空变化特征分析
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Citation: Yang C J, Zhao Z J, Ni J, et al. Temporal and spatial analysis of changes in snow cover in western Sichuan based on MODIS images. Sci China Earth Sci, 2012, 55: 13291335, doi: 10.1007/s11430-011-4336-5
Snow cover has a significant influence on the environment and is also influenced by the environment [1]. The volume of snowfall and the area under snow cover (ASC) is a function of atmospheric circulation, rainfall, and water resources [2, 3]. The relative partitioning of precipitation affects both human and natural processes, including agriculture, forestry, horticulture, traffic, communication, soil, and river flows. Depending on the total volume of snowfall, its effects can be both beneficial and detrimental to the environment [4–8]. The western region of Sichuan Province is located on the east side of the Tibetan Plateau. This area includes Garzê,
© Science China Press and Springer-Verlag Berlin Heidelberg 2012
1330
Yang C J, et al.
Sci China Earth Sci
August (2012) Vol.55 No.8
ference between B4 and B6 bands divided by the sum of the two bands. The accuracy of snow cover estimates was lower in forested areas when using MODIS snow products (85%) than that for NDSI [18]. Thus, NDSI is typically regarded as the best method for extracting information about snow cover from remote sensing images [19]. For example, in cloud free areas, MODIS snow products yielded an accuracy of 87.5% [20] whereas NDSI yielded an accuracy of 95% [21]. We evaluated changes in snow pack in the western region of Sichuan using multi-temporal MODIS images acquired between 2002 and 2008. These data provide insights into the stability of the water supply for this region.
SCIENCE CHINA
Earth Sciences
• RESEARCH PAPER •
August 2012 Vol.55 No.8: 1329–1335 doi: 10.1007/s11430-011-4336-5
Temporal and spatial analysis of changes in snow cover in western Sichuan based on MODIS images
We developed a method for analyzing the change in snow cover using MODIS imagery. The method was applied to images of western Sichuan Province, China taken between 2002 and 2008. The model for extracting data on snow cover from MODIS images was created by spectral analysis. The multi-temporal snow layers were used to evaluate the temporal and spatial change in the area under snow cover between 2002 and 2008 using overlay and statistical analysis in ARCGIS. The majority (60.4%) of western Sichuan was rarely covered by snow and only 0.3% was covered by perennial snow in 2002. Snow cover was primarily distributed in Garzê and Aba. The area under snow cover was significantly and negatively correlated with the average monthly temperature and rainfall in 2002. The largest area under snow cover was measured in 2006 and the smallest was in 2007. Similarly, the area of snowmelt was the highest in 2006 and lowest in 2007. In general, the elevation of the snow line increased throughout the period 2002–2008; however, the elevation decreased in some years. Our results provide an important insight into the distribution of snow in this region, and may be useful for climate modeling and predicting the availability of water resources and the occurrence of floods and droughts. MODIS, western Sichuan, snow extraction, snow change
YANG CunJian1,2*, ZHAO ZiJian2, NI Jing1, REN XiaoLan1 & WANG Qin1
1
Research Center of Remote Sensing and Geographic Information Systems, Key Laboratory of Land Resources Evaluation and Monitoring in Southwest under Ministry of Education, Sichuan Normal University, Chengdu 610068, China; 2 Institute of Geo-Spatial Information Science and Technology, University of Electronic Science and Technology of China, Chengdu 610054, China Received November 29, 2010; accepted June 8, 2011; published online January 2, 2012
1
1.1
Study area and data
Study area
The study area in western Sichuan includes Garzê, Aba, and Liangshan prefectures and Panzhihua, an area of 30.54×104 km2 (63% of the total area of Sichuan). The area includes the southwestern mountain region of Sichuan and the western Sichuan Plateau. To study the relationship between temperature, rainfall and snow, we collected temperature and rainfall data from meteorological observation stations throughout the region (Figure 1). The western Sichuan Plateau is an extension of the Tibetan Plateau to the southeast and forms a transitional zone between the first and second steps. The elevation ranges from 4000–4500 m and the
Snow cover has a significant influence on the environment and is also influenced by the environment [1]. The volume of snowfall and the area under snow cover (ASC) is a function of atmospheric circulation, rainfall, and water resources [2, 3]. The relative partitioning of precipitation affects both human and natural processes, including agriculture, forestry, horticulture, traffic, communication, soil, and river flows. Depending on the total volume of snowfall, its effects can be both beneficial and detrimental to the environment [4–8]. The western region of Sichuan Province is located on the east side of the Tibetan Plateau. This area includes Garzê,
© Science China Press and Springer-Verlag Berlin Heidelberg 2012
1330
Yang C J, et al.
Sci China Earth Sci
August (2012) Vol.55 No.8
ference between B4 and B6 bands divided by the sum of the two bands. The accuracy of snow cover estimates was lower in forested areas when using MODIS snow products (85%) than that for NDSI [18]. Thus, NDSI is typically regarded as the best method for extracting information about snow cover from remote sensing images [19]. For example, in cloud free areas, MODIS snow products yielded an accuracy of 87.5% [20] whereas NDSI yielded an accuracy of 95% [21]. We evaluated changes in snow pack in the western region of Sichuan using multi-temporal MODIS images acquired between 2002 and 2008. These data provide insights into the stability of the water supply for this region.
SCIENCE CHINA
Earth Sciences
• RESEARCH PAPER •
August 2012 Vol.55 No.8: 1329–1335 doi: 10.1007/s11430-011-4336-5
Temporal and spatial analysis of changes in snow cover in western Sichuan based on MODIS images
We developed a method for analyzing the change in snow cover using MODIS imagery. The method was applied to images of western Sichuan Province, China taken between 2002 and 2008. The model for extracting data on snow cover from MODIS images was created by spectral analysis. The multi-temporal snow layers were used to evaluate the temporal and spatial change in the area under snow cover between 2002 and 2008 using overlay and statistical analysis in ARCGIS. The majority (60.4%) of western Sichuan was rarely covered by snow and only 0.3% was covered by perennial snow in 2002. Snow cover was primarily distributed in Garzê and Aba. The area under snow cover was significantly and negatively correlated with the average monthly temperature and rainfall in 2002. The largest area under snow cover was measured in 2006 and the smallest was in 2007. Similarly, the area of snowmelt was the highest in 2006 and lowest in 2007. In general, the elevation of the snow line increased throughout the period 2002–2008; however, the elevation decreased in some years. Our results provide an important insight into the distribution of snow in this region, and may be useful for climate modeling and predicting the availability of water resources and the occurrence of floods and droughts. MODIS, western Sichuan, snow extraction, snow change
YANG CunJian1,2*, ZHAO ZiJian2, NI Jing1, REN XiaoLan1 & WANG Qin1
1
Research Center of Remote Sensing and Geographic Information Systems, Key Laboratory of Land Resources Evaluation and Monitoring in Southwest under Ministry of Education, Sichuan Normal University, Chengdu 610068, China; 2 Institute of Geo-Spatial Information Science and Technology, University of Electronic Science and Technology of China, Chengdu 610054, China Received November 29, 2010; accepted June 8, 2011; published online January 2, 2012
1
1.1
Study area and data
Study area
The study area in western Sichuan includes Garzê, Aba, and Liangshan prefectures and Panzhihua, an area of 30.54×104 km2 (63% of the total area of Sichuan). The area includes the southwestern mountain region of Sichuan and the western Sichuan Plateau. To study the relationship between temperature, rainfall and snow, we collected temperature and rainfall data from meteorological observation stations throughout the region (Figure 1). The western Sichuan Plateau is an extension of the Tibetan Plateau to the southeast and forms a transitional zone between the first and second steps. The elevation ranges from 4000–4500 m and the
