Abstract:  Rice is an important cereal crop in the world and the most important food resource in China. Under the background of global warming, the degree and frequency of extreme high temperature heat waves are also increasing. From July to August every year, continuous high temperature weather with daily maximum temperature exceeding 35.0℃ often occurs in the middle and lower reaches of the Yangtze River affected by subtropical high. At this time, rice is in a sensitive period of growth and development, and continuous high temperature will seriously influences the physiological development of rice. Consequently, scientific and reasonable monitoring of the occurrence and development process of high temperature stress to rice is of great scientific significance and practical value for impact assessment of rice yield variation and agricultural production decisions in the context of global warming. At present, crop growth monitoring methods mainly rely on field investigation and satellite remote sensing. However, the traditional field investigation methods are time-consuming and labor-intensive, and the accuracy is also influenced by the subjective consciousness of investigators. In addition, satellite remote sensing also has some shortcomings, such as low spatial resolution, long transit period, cloud pollution and so on. So, the application technology research of real-time monitoring of crop growth using multi-spectral sensors carried by portable drones is an important supplement and improvement to the existing monitoring and investigation methods for high temperature stress to rice. In this paper, a remote sensing monitoring system for rice growth and data post-processing analysis and application methods were designed based on consumer-grade drones and portable multi-spectral sensors, and then Wuhu super rice production base in the middle and lower reaches of the Yangtze river was selected as the experimental area, and the continuous high temperature days from July 20 to August 9, 2019 was taken as the experimental period. Experimental results showed that there was a significant exponential relationship between the rice vegetation index and the leaf area index, with the correlation coefficient of 0.918, and then the inversion model of rice leaf area index was established. Finally, the discrimination conditions of leaf area index of rice under high temperature stress were further determined. The inversion model and discrimination conditions of leaf area index were used to extract and to analyze the spectral characteristics of rice under high temperature stress in the experimental area. During this continuous high temperature period, 15.3% of rice in the experimental area was damaged by the continuous high temperature stress, which is coincided with the reality from the field investigation conducted by agricultural department (i.e., the grain filling rate of rice was 82.2% in the experimental area). Compared with the traditional field survey and satellite remote sensing monitoring methods, the portable UAV multispectral remote sensing monitoring technology developed in this paper has advantages of high spatial resolution, real-time and large-scale monitoring and application of low cost, which is conducive to the popularization and promotion. It has a certain application prospect in the remote sensing monitoring of crop natural disasters.

Key words:  , UAV, Portable multispectral sensor, Rice, High temperature stress, Remote sensing monitoring, LAI