极地地区是地球系统中的特殊单元,是全球气候变化最显著、响应最敏感的区域。历史和现代的观测结果都表明, 极地地区对全球气候变化有“放大器”的作用。极地气候变化的幅度是中/低纬度地区的两倍,这说明在极地更易于监测到在中、低纬区不易察觉到的细微变化。南极冰雪区是地球系统的最大冷源和全球水气环流热力发动机的主要冷极之一。南极冰雪范围、表面特征(主要是反射率)的年际变化对全球水气环流的强度、全球热平衡和气候变化如温度、降水分布等都有明显的影响。

 本文利用MODIS(Moderate Resolution Imaging Spectroradiometer)遥感资料采用NDSI(归一化差分雪盖指数)法作冰雪覆盖制图，并监测了2003-2006年南极地区冰雪覆盖面积变化情况。文中探讨了大气校正、大范围图像镶嵌等MODIS数据处理方法和NDSI阈值法雪盖填图，并得出如下主要结论：

    1、使用MODIS遥感资料采用NDSI作冰雪覆盖制图，因南极地区缺乏实测验证数据，故将所得结果与美国冰雪数据中心提供的冰雪产品数据比较。两者相比，总体精度为99.27%，kappa系数为0.99；

2、2003-2006年间，南极地区2月份与10月份的冰雪覆盖面积都处于波动下降的态势，且2月份（暖季）冰雪覆盖面积波动幅度要大，平均每年的波动幅度为：18928平方千米  ，而10月份4年内的平均波动幅度为每年6405平方千米 ； 

    3、南极地区冰雪覆盖面积变化趋势有明显区域差异：东南极地区表现出显著的波动趋势，即2003年、2005年为较高值，2004和2006年为两个较低值；而西南极地区，除南极半岛以外，则是从2003年至2004年急剧下降，2005年、2006年再缓慢抬升的趋势；

    4、西南极的冰雪面积变化比东南极显著，平均年际递增量大于东南极。

The Polar Region is a special unit in Earth system and it is the most sensitive to global climate change. According to historical and modern observations, the Polar Region is like an “amplifier” on global climate change, with the variation range two times than that in low/Mid-latitude areas. Thus it is easier to monitoring subtle change.  The Antarctic snow and ice zone is the biggest cold source in Earth system. The annual change of Antarctic ice-snow cover scale and surface features has significant affect on the intensity of global water circulation, heat balance and climate change.

   The paper studies on ice-snow cover mapping using MODIS data by NDSI and monitors the change of ice-snow cover in Antarctica area during 2003-2006.It introduces the processing method of MODIS data, such as atmospheric correction, mosaic of images, and so on. Meanwhile, the paper concerns with ice-snow-cover mapping by NDSI. Finally, the paper reaches the following conclusions:

1. The paper maps ice-snow cover with MODIS data in test area. As lack of experimental veridical data in Antarctica, it compares the results with snow products provided by NSIDC (National Snow and Ice Data Center).  The overall accuracy is 99.27%, and Kappa coefficient is 0.99.

2. The ice-snow-covered area declined both in February and October during 2003-2006.This situation was more obvious in February, and average annual fluctuations rate was 18928 square kilometers  , compared with 6405 square kilometers in October.

3. Change trend of ice-snow-covered area is markedly different between East and West Antarctica. It shows significant fluctuations in East Antarctica, that is, higher value in 2003 and 2005, lower value in 2004 and 2006.While in west Antarctic, the ice-snow-covered area declined sharply from 2003 to 2004, and then climbed slowly in the following 2 years, with the exception of the Antarctic Peninsula.

4. The change trend of ice-snow-covered area is more obvious in West Antarctic than in East Antarctic, with a bigger annual incensement.