关键词: 寒潮, 光学遥感, 被动微波, 可见光, 马铃薯, 地表温度, NDVI, 广东

Abstract: 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.

Key words: cold wave, optical remote sensing, passive microwave, potato, land surface temperature NDVI, AMSR2, HJ-1 CCD, Guangdong