CALIPSO激光雷达水下信号反演大洋叶绿素浓度的探索
发布时间：2018-12-21 21:34
【摘要】：云-气溶胶激光雷达和红外探测卫星CALIPSO的主要载荷CALIOP能同时发射波长为532nm和1064nm的激光脉冲，研究表明主动探测器CALIOP在获取大气云层和气溶胶层参数的同时，532nm激光脉冲能穿透海表，获取海洋水体中颗粒物的后向散射信息。由于1064nm波长的光大部分表层海水吸收，因此本文旨在利用CALIPSO提供的532nm通道一级数据产品，计算CALIOP接收系统光电倍增管的瞬态响应函数，对水下原始数据进行校正，获得校正后的颗粒物后向散射系数，并研究其与MODIS大洋叶绿素浓度之间的关系。 利用CALIOP2008年532nm地表后向散射信号，结合胡永祥提出的拖尾峰值比方法计算地表引起的峰值信号以及其相邻信号之间的关系。结果表明北半球冬季和夏季样本数据特征呈现明显的差异性，并且北半球春季、秋季样本数据特征和冬季相同。并且北半球冬季数据中有43.6%的数据和夏季样本数据特性一致，56.4%的数据特性和南极大陆以及格陵兰岛相一致，由于南极大陆以及格陵兰岛常年被冰雪覆盖，因此判定北半球冬季和夏季CALIOP瞬态响应的差异主要是由于冰雪因素引起。提取陆地表面后向散射信号以及该信号前一个采样单元（bin）和紧邻其后的10个采样单元，利用Li提出方法可以计算得到CALIOP离散瞬态响应函数，使用最小二乘法进而求得瞬态响应的分段连续函数。不考虑冰雪因素的影响，则不同地球表面CALIOP瞬态响应函数是一致的。 由于CALIOP拖尾现象的存在，当系统接收到来自海表的信号时，使得该信号能量延伸到之后相邻的几个采样单元当中，，造成测量的海洋次表层水体的后向散射信号偏大，因此为了获得真实的后向散射信号，需使用瞬态响应函数进行校正。在广阔的大洋海域，合理假设大洋海水中颗粒物的后向散射主要由浮游植物引起。本文利用2008年CALIPSO提供的第三版本一级数据产品和AMSR-E提供的海面风速产品以及MODIS提供的叶绿素浓度和漫射衰减系数的年平均值，分别计算得到CALIPSO532nm波长水下信号和经瞬态响应校正后的信号，结果表明在在全球海域范围，直接提取信号和校正后信号与MODIS叶绿素浓度的相关系数分别为0.54和0.58，在60°S-40°N范围内的广阔海域，相关系数分别为0.72和0.79。
[Abstract]:The main payloads of cloud-aerosol lidar and infrared detection satellite CALIPSO CALIOP can simultaneously emit laser pulses with the wavelength of 532nm and 1064nm. It is shown that the active detector CALIOP can obtain the parameters of atmospheric clouds and aerosol layers at the same time. 532nm laser pulses can penetrate the sea surface to obtain the backward scattering information of particles in the ocean water. Because most of the light of 1064nm wavelength is absorbed by surface seawater, the purpose of this paper is to calculate the transient response function of photomultiplier tube of CALIOP receiving system by using the first-order data product of 532nm channel provided by CALIPSO, and to correct the original underwater data. The corrected backscatter coefficient of particulate matter was obtained and the relationship between the backscattering coefficient and chlorophyll concentration in MODIS ocean was studied. Based on the CALIOP2008 annual 532nm backscattering signal and Hu Yongxiang's trailing peak ratio method, the relationship between the surface peak signal and its adjacent signal is calculated. The results show that the characteristics of sample data in winter and summer of Northern Hemisphere are obviously different, and the characteristics of sample data in Spring and Autumn of Northern Hemisphere are the same as those in winter. In addition, 43.6% of the winter data in the Northern Hemisphere are consistent with the summer sample data, and 56.4% of the data are consistent with the Antarctic continent and Greenland, because the Antarctic continent and Greenland are covered with ice and snow all the year round. Therefore, the difference between winter and summer CALIOP transient responses in the Northern Hemisphere is mainly caused by ice and snow. The backscatter signal of the land surface and the former sampling unit (bin) and the next 10 sampling units are extracted. The discrete transient response function of CALIOP can be calculated by using the method proposed by Li. The piecewise continuous function of transient response is obtained by using the least square method. The CALIOP transient response function of different earth surface is consistent without considering the influence of ice and snow factors. Because of the existence of CALIOP trailing phenomenon, when the system receives the signal from the sea surface, the energy of the signal extends to several adjacent sampling units, which results in the large backscatter signal of the measured ocean subsurface water body. Therefore, in order to obtain the true backscattering signal, the transient response function should be used to correct it. In the vast ocean area, it is reasonable to assume that the backscattering of particulate matter in ocean water is mainly caused by phytoplankton. In this paper, the annual mean values of the third version of the first class data product provided by CALIPSO in 2008, the sea surface wind speed product provided by AMSR-E and the chlorophyll concentration and diffuse attenuation coefficient provided by MODIS are used. The underwater signals of CALIPSO532nm wavelength and the signals corrected by transient response were calculated respectively. The results show that the correlation coefficients between the extracted signals and the chlorophyll concentration of MODIS are 0.54 and 0.58 respectively in the global sea area. In the wide sea area of 60 掳S-40 掳N, the correlation coefficients are 0.72 and 0.79, respectively.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P714.4
[Abstract]:The main payloads of cloud-aerosol lidar and infrared detection satellite CALIPSO CALIOP can simultaneously emit laser pulses with the wavelength of 532nm and 1064nm. It is shown that the active detector CALIOP can obtain the parameters of atmospheric clouds and aerosol layers at the same time. 532nm laser pulses can penetrate the sea surface to obtain the backward scattering information of particles in the ocean water. Because most of the light of 1064nm wavelength is absorbed by surface seawater, the purpose of this paper is to calculate the transient response function of photomultiplier tube of CALIOP receiving system by using the first-order data product of 532nm channel provided by CALIPSO, and to correct the original underwater data. The corrected backscatter coefficient of particulate matter was obtained and the relationship between the backscattering coefficient and chlorophyll concentration in MODIS ocean was studied. Based on the CALIOP2008 annual 532nm backscattering signal and Hu Yongxiang's trailing peak ratio method, the relationship between the surface peak signal and its adjacent signal is calculated. The results show that the characteristics of sample data in winter and summer of Northern Hemisphere are obviously different, and the characteristics of sample data in Spring and Autumn of Northern Hemisphere are the same as those in winter. In addition, 43.6% of the winter data in the Northern Hemisphere are consistent with the summer sample data, and 56.4% of the data are consistent with the Antarctic continent and Greenland, because the Antarctic continent and Greenland are covered with ice and snow all the year round. Therefore, the difference between winter and summer CALIOP transient responses in the Northern Hemisphere is mainly caused by ice and snow. The backscatter signal of the land surface and the former sampling unit (bin) and the next 10 sampling units are extracted. The discrete transient response function of CALIOP can be calculated by using the method proposed by Li. The piecewise continuous function of transient response is obtained by using the least square method. The CALIOP transient response function of different earth surface is consistent without considering the influence of ice and snow factors. Because of the existence of CALIOP trailing phenomenon, when the system receives the signal from the sea surface, the energy of the signal extends to several adjacent sampling units, which results in the large backscatter signal of the measured ocean subsurface water body. Therefore, in order to obtain the true backscattering signal, the transient response function should be used to correct it. In the vast ocean area, it is reasonable to assume that the backscattering of particulate matter in ocean water is mainly caused by phytoplankton. In this paper, the annual mean values of the third version of the first class data product provided by CALIPSO in 2008, the sea surface wind speed product provided by AMSR-E and the chlorophyll concentration and diffuse attenuation coefficient provided by MODIS are used. The underwater signals of CALIPSO532nm wavelength and the signals corrected by transient response were calculated respectively. The results show that the correlation coefficients between the extracted signals and the chlorophyll concentration of MODIS are 0.54 and 0.58 respectively in the global sea area. In the wide sea area of 60 掳S-40 掳N, the correlation coefficients are 0.72 and 0.79, respectively.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P714.4
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