MODIS亮温与气温及地温的相关性分析
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摘要
对MODIS卫星遥感亮温与气温、地温进行了不同时间尺度的大量的计算比对和相关性分析,以期得到直接采用实时MODIS亮温相对变化,结合地面实测地温来研究地震活动热异常的短临变化信息的具有统计意义的依据。结果表明:1)亮温与气温、地温从较长周期的时间尺度(月均值)上看,其相关性很好。而短周期(日均值)尽管明显低于较长周期,但仍然有着较好的相关性。2)通过大量计算比对发现,亮温均值与地温和气温的相关性随着像元面积的增大而逐渐升高。这表明,大气和环境的影响对单一像元而言较为明显。而这种影响可以由一定区域像元的亮温均值得到一些削弱,即一定区域的亮温均值与地温(0cm)的相关性优于单个探测像元的亮温。基于此,在研究亮温相对变化时,应尽量避免采用单一像元的亮温值,利用一定区域的像元均值可能会达到一些排除干扰的效果;3)鉴于热红外亮温数据与地表实际测到的地表温度(0cm)有着显著的相关性,将实时探测到的大面积均匀分布的亮温相对变化与地表实际测到的地表温度结合起来进行热异常变化信息研究,可望提升其可信度和有效性。
Through numerous comparison experiments and the correlation analysis at different time scales,the present study tried to get the important basis of statistic significance in aspect of the use of real-time relative changes of MODIS BT combined with field ST measurements from thermal infrared anomalies for directly investigating the short and imminent earthquake-related phenomena.Results of correlation analysis show that:1)Significant correlation exists between brightness temperature,air temperature and ground temperature in the view of the longer cycle time scale(monthly mean),even in the case of short cycle(daily means),where the correlation is significantly lower than that of longer cycle,they still have good correlations;2)The correlation between the mean brightness temperature and the surface temperature increases gradually with the increased pixel size involved.This indicates that the atmospheric and environmental effect on brightness temperature is more obvious for single pixel.This effect can be reduced by using mean brightness temperature of pixels in a certain region.In other words,the correlation between mean brightness temperature of pixels in a region and the surface temperature(0cm)is better than that of a single pixel.Consequently,when studying the relative changes in brightness temperature,it is suggested that we should try to avoid using the brightness temperature values of a single pixel;3)The combination of the MODIS brightness temperature at large coverage with surface temperature in field might improve the feasibility and reliability of detection of the thermal IR anomalous change;it has been demonstrated by the significant correlation between the retrieved MODIS BT products and field ST measurements(0cm).In general,this study implies the statistical significance of investigating short and extemporaneous activities of earthquake phenomenon by means of analyzing temporal changes of the retrieved near real-time MODIS brightness temperature products coupled with the measurements of surface temperatures.It should be noted that the specific geographic environments which depend on the changing weather process and the complex geological setting could hamper the extraction of information of the short-term and impending abnormal seismic thermal changes.Therefore,we need to take fully into account the above-mentioned impacts when applying satellite thermal infrared data to earthquake prediction research and designing data processing methods.
Through numerous comparison experiments and the correlation analysis at different time scales,the present study tried to get the important basis of statistic significance in aspect of the use of real-time relative changes of MODIS BT combined with field ST measurements from thermal infrared anomalies for directly investigating the short and imminent earthquake-related phenomena.Results of correlation analysis show that:1)Significant correlation exists between brightness temperature,air temperature and ground temperature in the view of the longer cycle time scale(monthly mean),even in the case of short cycle(daily means),where the correlation is significantly lower than that of longer cycle,they still have good correlations;2)The correlation between the mean brightness temperature and the surface temperature increases gradually with the increased pixel size involved.This indicates that the atmospheric and environmental effect on brightness temperature is more obvious for single pixel.This effect can be reduced by using mean brightness temperature of pixels in a certain region.In other words,the correlation between mean brightness temperature of pixels in a region and the surface temperature(0cm)is better than that of a single pixel.Consequently,when studying the relative changes in brightness temperature,it is suggested that we should try to avoid using the brightness temperature values of a single pixel;3)The combination of the MODIS brightness temperature at large coverage with surface temperature in field might improve the feasibility and reliability of detection of the thermal IR anomalous change;it has been demonstrated by the significant correlation between the retrieved MODIS BT products and field ST measurements(0cm).In general,this study implies the statistical significance of investigating short and extemporaneous activities of earthquake phenomenon by means of analyzing temporal changes of the retrieved near real-time MODIS brightness temperature products coupled with the measurements of surface temperatures.It should be noted that the specific geographic environments which depend on the changing weather process and the complex geological setting could hamper the extraction of information of the short-term and impending abnormal seismic thermal changes.Therefore,we need to take fully into account the above-mentioned impacts when applying satellite thermal infrared data to earthquake prediction research and designing data processing methods.
引文
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黄广思.1993.地温遥感预报地震的原理和方法[J].地壳形变与地震,13(1):23—29.HUANG Guang-si.1993.Principle and methods of earthquake prediction by temperature remotely sensed[J].CrustalDeformation and Earthquake,13(1):23—29(in Chinese).
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刘玉洁,杨忠东,等.2001.MODIS遥感信息处理原理与算法[M].北京:科学出版社.LIU Yu-jie,YANG Zhong-dong,et al.2001.Principle and Algorithm for Processing MODIS Remote Sensing Data[M].Science Press,Beijing(in Chinese).
廖顺宝,马琳,岳燕珍,等.2004.NOAA—AVHRR资料反演地温与地面实测值的对比分析[J].国土资源遥感,59(1):19—22.LIAO Shun-bao,MA Lin,YUE Yan-zhen,et al.2004.A comparison and analysis of land surface temperatures from re-mote sensing and observation stations[J].Remote Sensing for Land&Resources,59(1):19—22(in Chinese).
马瑾,刘力强,刘培洵,等.2007.断层失稳错动热场前兆模式:雁列断层的试验研究[J].地球物理学报,50(4):1141—1149.MA Jin,LIU Li-qing,LIU Pei-xun,et al.2007.Thermal precursory pattern of fault unstable sliding:An experimentalstudy of en echelon faults[J].Chinese Journal of Geophysics,50(4):1141—1149(in Chinese).
屈春燕,马瑾,单新建.2006.一次卫星热红外地震前兆现象的证伪[J].地球物理学报,49(2):490—495.QU Chun-yan,MA Jin,SHAN Xin-jian.2006.Counterevidence for an earthquake precursor of satellite thermal infraredanomalies[J].Chinese Journal of Geophysics,49(2):490—495(in Chinese).
邓明德,耿乃光,崔承禹.1997.岩石应力状态改变引起岩石热状态改变的研究[J].中国地震,13(2):179—185.DENG Ming-de,GENG Nai-guang,CUI Cheng-yu.1997.The study on the variation of thermal state of rocks caused byvariation of stress state of rocks[J].Earthquake Research in China,13(2):179—185(in Chinese).
范新岗,汤懋苍.1994.大地震前后地温、降水及浅层热流通量场的结构特征[J].地球物理学报,37(1):192—203.FAN Xin-gang,TANG Mao-cang.1994.A preliminary study on structural feature of soil temperature,precipitation andsoil heat flux fields before and after strong earthquakes[J].Chinese Journal of Geophysics,37(1):192—203(inChinese).
黄广思.1993.地温遥感预报地震的原理和方法[J].地壳形变与地震,13(1):23—29.HUANG Guang-si.1993.Principle and methods of earthquake prediction by temperature remotely sensed[J].CrustalDeformation and Earthquake,13(1):23—29(in Chinese).
刘培洵,刘力强,陈顺云,等.2004.地表岩石变形引起热红外异常的试验研究[J].地震地质,26(3):502—511.LIU Pei-xun,LIU Li-qiang,CHEN Shun-yun,et al.2004.An experiment on the infrared radiation of surficial rocksduring deformation[J].Seismology and Geology,26(3),502—511(in Chinese).
刘玉洁,杨忠东,等.2001.MODIS遥感信息处理原理与算法[M].北京:科学出版社.LIU Yu-jie,YANG Zhong-dong,et al.2001.Principle and Algorithm for Processing MODIS Remote Sensing Data[M].Science Press,Beijing(in Chinese).
廖顺宝,马琳,岳燕珍,等.2004.NOAA—AVHRR资料反演地温与地面实测值的对比分析[J].国土资源遥感,59(1):19—22.LIAO Shun-bao,MA Lin,YUE Yan-zhen,et al.2004.A comparison and analysis of land surface temperatures from re-mote sensing and observation stations[J].Remote Sensing for Land&Resources,59(1):19—22(in Chinese).
马瑾,刘力强,刘培洵,等.2007.断层失稳错动热场前兆模式:雁列断层的试验研究[J].地球物理学报,50(4):1141—1149.MA Jin,LIU Li-qing,LIU Pei-xun,et al.2007.Thermal precursory pattern of fault unstable sliding:An experimentalstudy of en echelon faults[J].Chinese Journal of Geophysics,50(4):1141—1149(in Chinese).
屈春燕,马瑾,单新建.2006.一次卫星热红外地震前兆现象的证伪[J].地球物理学报,49(2):490—495.QU Chun-yan,MA Jin,SHAN Xin-jian.2006.Counterevidence for an earthquake precursor of satellite thermal infraredanomalies[J].Chinese Journal of Geophysics,49(2):490—495(in Chinese).
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