基于AVIRIS高光谱数据的海表甲烷异常识别

Research on Detection of Marine Methane based on AVIRIS Hyperspectral Data

研究海洋表面烃类富集状况在监测海洋环境和探测海底油气资源中具有重要意义,海表渗漏烃中,甲烷是气态烃中最具代表性的组分。为了精准识别海表甲烷异常,研究设计了相应光谱实验,以海水为背景测定甲烷光谱反射率,基于实测数据分析甲烷的光谱特征,运用比值导数光谱法削弱海水背景组分的光谱干扰,提取出甲烷光谱吸收特征波段。研究发现甲烷在1642—1672 nm和2169—2378 nm波长范围存在光谱吸收,通过比值导数处理后显著增强了其中1642—1672 nm和2169—2208 nm区间的甲烷吸收特征,在Rebecca等提出的CH_(4)I甲烷反演指数的基础上加入比值导数参数,建立了基于AVIRIS数据的海表甲烷含量指数MI,与甲烷含量的相关系数R^(2)=0.9942,将其应用于美国加利福利亚州圣芭芭拉海峡Coal Oil Point(COP)烃渗漏区甲烷异常识别,并与CH_(4)I指数和Bradley等提出的AVIRIS CH4指数ζ(L2298/L2058)进行反演效果对比。结果表明:运用MI指数可以有效识别海表甲烷浓度异常,与ζ、CH_(4)I指数反演结果相比,MI指示的甲烷浓度异常分布与ζ指数反演结果更为吻合,效果显著优于CH_(4)I指数反演结果。

Methane is the most representative component of the gaseous hydrocarbon in the marine hydrocarbon seepage.In order to detect the marine methane anomalies accurately,a methane spectra experiment was designed to obtain hyperspectral data of different methane content in seawater background.Based on the measured data,the spectral characteristics of methane are analyzed.The ratio derivative spectrum method is used to weaken the spectral interference of seawater background components for extracting the absorption characteristic band of methane.The results show that methane has spectral absorption in the wavelength range of 1642-1672 nm and 2169-2378 nm,and the absorption characteristics of methane in the range of 1642-1672 nm and2169-2208 nm are significantly enhanced by ratio derivative treatment.Based on the methane index CH_(4)I,the ratio derivative parameter is added to establish the marine CH_(4) content index MI for AVIRIS data.The correlation coefficient R^(2) between MI and methane content is 0.9942.MI index is applied to the identification of methane anomalies in the hydrocarbon seepage area of the Santa Barbara Channel Coal Oil Point(COP),California,USA.Compared with the inversion results of CH_(4)I index and CH_(4) indexζ(L2298/L2058).The abnormal distribution of methane concentration indicated by MI is more consistent with the hydrocarbon leakage area,and the results is better than the inversion results of CH_(4)I index.