结合被动微波和光学遥感的“超级寒潮”广东地表温度特征及其对马铃薯生长的影响

利用被动微波可穿透云层的优势，基于GCOM-W1/AMSR2（Global Change Observation Mission-Water/ Advanced Microwave Scanning Radiometer 2）星载被动微波传感器的多通道亮度温度数据，反演了2016年1月下旬“超级寒潮”过程的广东省每日地表温度，分析了寒潮过程中广东省地表温度的时空变化特征。结果表明：在寒潮前后，广东省地表温度呈现出明显的先下降而后上升的趋势，寒潮过程带来的地表最低温度在广东北部大部分地区达到了277 K（4℃），西南大部分地区为280~282 K（7~9℃），其余大部分地区278~279 K（5~6℃）；降温幅度在广东南部地区达到了8~12 K（8~12℃），北部大部分地区为5~7 K（5~7℃）。此外，利用归一化植被指数（NDVI）对植被生长的指示作用，基于HJ-1 A/B卫星的CCD传感器的多通道反射率数据，计算了近3年冬季广东省典型马铃薯种植区域马铃薯叶片的NDVI值，结果表明：马铃薯叶片的NDVI值在此次寒潮过程后出现了明显的下降，大部分地区（55.4%）马铃薯NDVI降低了0.1~0.2，部分地区（17.2%）马铃薯NDVI下降了0.2~0.3；进一步对比此次“超级寒潮”后同时段的前2年数据，发现寒潮后马铃薯叶片NDVI相对于正常年份也低了0.2，表明马铃薯叶片NDVI下降的主要原因是寒潮带来的低温，而不只是马铃薯的正常老化现象。NDVI的降低表明大部分地区马铃薯生长受到了抑制，马铃薯生长状况的这一变化也通过现场调查得到了证实。

Land Surface Temperature Characteristic in Guangdong during a Super Cold Wave and Its Impact on Potato Growth Combining Microwave and Optical Remote Sensing

Under the background of climate warming, the frequency and intensity of cold wave that invaded Guangdong Province in South China were gradually decreasing in recent years. However, in late January of 2016, a named “super cold wave” invaded Guangdong and caused serious influence on agriculture production. Compared to traditional observation and investigation approaches, remote sensing has the feature of “large area, total coverage, high efficiency” in earth observation. In this paper, by the advantage of microwave at penetrating cloud, the data of multi-channel brightness temperature (TB) from the GCOM-W1/AMSR2 (Global Change Observation Mission-Water/Advanced Microwave Scanning Radiometer 2) were used to inverse satellite-derived land surface temperature (LST). Based on the satellite-derived LST, Guangdong Province’s ground temperature spatio-temporal characteristic was analyzed. Results showed that ground temperature in Guangdong Province apparently decreased and then increased during the whole “super cold wave” process: the minimum LST reached low value under 277 K(4℃) in most of northern province, 280~282 K(7~9℃) in most of southwest and 278~279 K(5~6℃) in rest of the province; the temperature drop range reached 8~12 K(8~12℃) in most of southern Guangdong and 5~7 K(5~7℃) in most northern areas. Moreover, by using NDVI (Normalized Difference Vegetation Index)’s capability of indicating plant growth condition, based on multi-channel’s reflectance from HJ-1 A/B satellite’s CCD sensors, potato leaves’ NDVI in typical planted area of Guangdong in recent 3 years was calculated. Results showed that obvious declination of potato leaves’ NDVI after the “super cold wave” could be seen: NDVI decreased by 0.1~0.2 in most study areas (55.4% of planted area); NDVI decreased by 0.2~0.3 in most central areas (17.2% of planted area). NDVI value at the same period of the past two year was further analyzed; the result showed that NDVI after the “super cold wave” was lower than that of the “normal” year, indicating that the declination of potato leaves’ NDVI was mainly caused by low temperature of the cold wave, not only the result of aging phenomenon. The declination of NDVI indicated that the growth of the potato was restricted, that was confirmed by in situ investigation. In general, the capability of passive microwave remote sensing in retrieving continuous daily LST in frequent-cloudy area, such as South China, was shown in this study, indicating its potential value in monitoring cold disasters. On the other hand, based on optical remote sensing, NDVI’s potential in indicating plant growing condition was also further confirmed in this study. Combining both, this study realized the cold wave low temperature monitoring and plants’ cold injury evaluation. This study was a case firstly combining microwave and optical remote sensing on cold process monitoring and crop disaster assessment in recent years. It may have important reference value to related studies. In future work, early warning of cold disaster will also be realized by remote sensing if near-surface air temperature is retrieved and cold disaster modeling introduced.