摘要
针对2008年初浙江省遭受的持续性大范围低温雨雪冰冻天气,利用MODIS数据,综合运用遥感和地理信息系统技术对积雪的发生、发展和消融特征进行深入研究,在探讨云和积雪区分关键技术的基础上,建立积雪指数模型提取积雪专题信息,对积雪覆盖进行动态监测,同时利用DEM分地区分析各海拔高度带的积雪覆盖情况,探讨其消融变化特征,最后用雪灾前后△NDVI的方法结合地面实地调查,对林区进行灾情初步评估。研究结果表明,积雪的消融大致呈负指数减少趋势,起初各海拔高度带积雪覆盖比例呈中间多两头少的特征,即海拔300～900 m的中等海拔高度上积雪覆盖率较高,达70%以上,在300 m以下及900 m以上海拔高度带积雪覆盖率为50%左右,随着积雪的慢慢消融,各高程带间的积雪面积差逐渐减小,消融速度较之前明显减缓,表现出较稳定的下降趋势后再继续融化的特点,至2月16日,积雪覆盖比例与高程带呈正向一致性,即海拔越高,积雪覆盖越大,2月17日海拔500 m以下积雪已基本消融,20日700 m以下积雪基本消融,至2月29,全省基本无积雪。林区受灾的严重程度主要与积雪覆盖时间及林区海拔高度有关。利用遥感和地理信息系统技术在南方开展雪情分析、动态监测及灾后评估工作,对地方防灾减灾具有重要的指导意义。
At the beginning of 2008, persistent large-scale of ice and snow weather hit Zhejiang Province. With the support of remote sensing and geographical information system （GIS） technology, a deep study on the genesis, developing and melting of snow was carried out. First, snow and cloud were distinguished well using MODIS data, and a snow model （normalized difference snow index） was established to extract the snow information. Then, spatial and quantitative analyses on the distribution of snow cover were conducted, and the melt character was studied through the snow cover depletion curve. Finally, a preliminary assessment of the disaster of forests was discussed using the method of ANDVI. The results show that snow melt has a decreasing trend of minus exponent. Originally, the snow cover ratio at the middle altitude （300--900 m） could reach over 70% and was more than that at altitudes higher than 900 m or lower than 300 m. Meanwhile, the disparities in the different elevation zones became narrower along with the snow melting. The speed of snow melt slowed down significantly as before. On Feb. 16, snow cover was consistent with the terrain character, that is, the higher the elevation is, the greater the snow cover is. When most snow is distributed in the high mountainous area, the speed of snow melt is much slower as before. Until Feb. 29, there was no snow at the study area. The degree of disaster is related to the time of snow cover and the elevation of the forest area. Working at real time monitoring, dynamic analysis and disaster assessment of snow cover in South China is very important to the disaster prevention and reduction of local government.
出处
《气象》
CSCD
北大核心
2010年第4期85-89,共5页
Meteorological Monthly
基金
浙江省气象局轨道项目(编号:TG200707)资助
