高精度海表皮温红外辐射测量系统研究

Global climate change has significant effect on the environment of the earth. Sea surface temperature (SST) is an important indicator of the climate change. For monitoring the climate change, it requires consistent and accurate SST with uncertainties less than 0.3 K. The accuracy of the satellite SST data has been validated against in-situ SST data. The main in-situ data sources are bulk temperature measurements at the depth of 1 to 10 meter by the temperature sensor based on the ships and buoys. However, the satellite infrared sensors measure the radiance emitted from the surface layer of 10 micron thickness and microwave sensors measure the radiance from the surface layer of 1 mm. The vertical variations of the temperature in the surface layer caused by solar radiantion, the skin effect and etc., contribute to the uncertainty of the validation results using the in-situ bulk temperature data. It is necessary to collect in-situ sea surface skin temperature to validate the accuracy of satellite SST products. An radiometry system for accurate measurements of sea surface skin temperature will be investigated. The system should be meet the requirements for the validation of SST data from satellite observations. The key issues of the infrared radiometry system will be addressed. The atmosphric correction of the radiation will be studied. Model simulation and field measurements will be used to analyse the variations of the emissivity of the sea water in the infrared band with view angles and wind speed. The effective emissivity of the blackbody will be studied for the real-time internal calibration of the system. The optical-electronic rain gauge sensor and air purging technique will be tested for autonomous operation. The objective of this research is to solve the key issues of the infrared radiometry system mentioned above so the system is capable to be operated on-board ships or oil platforms autonomously for 3 months with an accuracy of 0.1K.

海表温度是气候变化的关键指征参数，气候变化监测要求海表温度长时间序列数据的一致性并且误差小于0.3K，卫星海表温度数据的精度需要现场海上测量数据验证，红外、微波传感器观测的是深度分别为微米、毫米级的表皮海水辐射，目前现场海表温度的来源主要由船载或者浮标上温度传感器测量深度约1-10米的体温，由于太阳辐射、表皮效应等造成海表温度垂直分布的差异是验证误差的重要来源之一。本项目拟研究海上现场高精度海表皮温红外辐射测量系统用于验证卫星数据的精度，基于红外辐射传输理论，研究大气辐射校正,通过模拟计算和海上观测数据分析海水比辐射率随观测角度、风速等的变化，提高黑体辐射源的有效发射率用于测量系统的实时内部标定，研究基于光电雨量传感器和吹扫技术实现自主工作，本项目的目标解决红外辐射测量系统的关键科学问题，使得系统可搭载于船只或安装于海上平台无人值守连续测量海表皮温，精度达0.1K。

海表温度是气候变化的关键指征参数，卫星海表温度的业务化观测已经有将近40年，气候变化监测要求海表温度长时间序列数据的一致性并且误差小于0.3 K，卫星海表温度数据的精度需要现场海上测量数据印证，红外、微波星载传感器观测的是分别为微米、毫米级的表皮海水辐射，常规现场海表温度主要由船载或者浮标上温度传感器测量深度约0.5米以下的体温，由于太阳辐射、风速等造成海表温度垂直分布的差异是验证误差的重要来源之一，利用非接触式的红外辐射计进行现场测量是印证红外卫星海表温度观测精度的有效手段。本项目基于红外辐射传递理论，研发了一套无人值守连续自动工作高精度海表温度测量系统，系统主要包括辐射测量传感器，内部校正用黑体模块、机电模块及控制器、降雨监测模块、姿态采集模块、卫星定位模块、无线收发模块等，系统可搭载于科考船或海上平台，连续测量海表皮温，通过降雨监测模块控制仪器开关实现无人值守连续自动工作，通过内部黑体完成实时定标，同时对天空辐射进行校正，以达到高精度海表皮温测量目标，进行了分模块测试和总装测试，并采用高精度外部黑体进行了测试，结果表明，可以达到优于0.1 K的测温精度；针对科考船海上实验，搭建完成供电、通讯、干燥气吹扫等现场实验条件，进行了6个航次海上测试，并将测量的数据与英国南安普顿大学研制的红外海表测温辐射计所测量的数据进行了对比分析，根据海试结果，改进完善系统，所研发的系统的指标达到预期目标；本测量系统参加了在国际标准计量机构之一英国国家物理实验室进行的用于海表皮温测量的红外辐射计国际对比实验，该实验目的是对建立和维持卫星反演海表温度产品验证的国际单位制可溯源性进行全球基准参考测量，共分为实验室与水库实验两个部分，实验室部分本项目测量系统标准与黑体进行标，测量结果表明本系统达到设计目标，在水库测量部分，本系统测量结果最接近均值，对比试验表明本系统达到国际先进水平。