关键词: 积雪, 土库曼斯坦, MODIS, 监测

Abstract: Snowcover is very important for the climatic change. So it is of great significance to exactly and timely extract snowcover information for dynamic change monitor. The arid areas are very sensitive in response to global climate change，the snowcover and glaciers are particularly prominent for climate change of the arid areas. Turkmenistan is one of typically dry continental climate countries. Therefore, it is important to understand the snowcover spatial and temporal variation in the Turkmenistan mountains. On the one hand, this study can provide decision-making basis for local agricultural development，on the other hand, can provide reliable information for local water resource management and ecological environment development. The application of MODIS to Turkmenistan snowcover monitoring and extracting snow information are still a less research field in this country.  The MODIS data were collected covering the study area during November 2011 to April 2012. The MODIS L1B 500 m resolution data were preprocessed by geometric correction，eliminating cloud effects，dealing with the effect of“Bow-tie” and radiometric calibration. Then according to normalized difference snow index （NDSI）algorithm and comprehensive threshold discriminance, the snowcover area and snowcover information were extracted in the Turkmenistan Mountains region between November 2011 to April 2012，and the snowcover spatial and temporal characteristics were revealed during the monitoring period in the Turkmenistan mountains. The core area of snowcover distribution is in Kopet Mountains in the southern of Turkmenistan. Its total snowcover areas show the fluctuation characteristics with two peaks and one valley，one peak in January and another in March 2012，respectively and one valley in February 2012. The minimum sonwcover area happened in November 2011，the  snowcover area reached to 39 km²，mainly due to the weather keeping steady “high” temperature state and a little snowfall.  In the beginning of December 2011，the temperature plummeted, resulting in a wide range of snowfall in the mountains, snowcover area sharply reached to 4 027.75 km2 only through one-month period.  The maximum snowcover area reached in January 2012 with the total area of 14 340.5 km²，compared to December the growth rate of January 2012 was 71.6%，snowcover area increasesd with elevation increases. Snowcover area reached its maximum in January 2012. Subsequently, the snowcover area reduced with temperature increasing. Monthly snowcover areas have a significant correlation between the average monthly temperature and monthly rainfall during the monitoring period. The correlation coefficients were 0.742 9 and 0.568 4，respectively. The results indicate that the snowcover areas have an increasing trend from the north to the south during heavy snowfall period.  The snowcover areas gradually reduce from the southeast to the northwest during the ablation period. The minimum sonwcover area was mainly in the north of the study area, and the stable seasonal snowcover reached maximum in the middle of the south. And the snowcover area reduced with temperature increase and rainfall decrease during the study period.

Key words: snow cover, Turkmenistan, MODIS, monitor