| The emissivity is an important parameter in radiation transmission and infrared remote sensing.It is a physical quantity that represents the physical surface radiation ability.The emissivity is an intrinsic property of the object itself,which is widely used in research fields such as weather forecasting,forecasting of sudden meteorological disasters,global circulation models,and regional climate models.Based on the MOD02 1km satellite remote sensing image data,ENVI5.5 software was used to invert the surface emissivity of Bohai sea.Firstly,geometric correction and calibration are performed with MCTK extension tool.Secondly,the storage types of the data need to be converted to meet the requirements of the atmospheric correction module.Then,the FLASSH atmospheric correction tool was used to invert the data and obtain the sea surface reflectivity data with a default enlargement of 10,000 times.In addition,data need to be clipped to obtain the sea surface reflectivity data of Bohai sea.Finally,according to the measurement principle of the reflection method,the sea surface emissivity is the complement of the sea surface reflectivity,and the data of the sea surface emissivity is obtained through the band calculation.The results show that the peaks of the minimum values occurred in the vicinity of the center wavelength of 0.8695 ?m in four regions and the peak value of the maximum appeared at the center wavelength of 0.94 ?m in the 12 months of the year of 2018.The sea surface emissivity of the Bohai Sea in spring is undulating with wavelength,the sea surface emissivity of the IV area is the largest,and the sea surface emissivity of the III area is the smallest.The sea surface emissivity of the Bohai Sea in summer is wavy with the wavelength.The sea surface emissivity of Zone III is the smallest and the values of I and II are almost the same and larger than those of the other two regions.The sea surface emissivity of the autumn seas has a single peak distribution with wavelength,and the sea surface emissivity values of the four regions are very close.The sea surface emissivity of the I zone is too large,and the sea surface emissivity of the IV zone is small.The sea surface emissivity in winter seas has a single peak distribution with wavelength,the sea surface emissivity in zone I is large,and the sea surface emissivity in zone III is small.The optical characteristics of surface emissivity were studied by means of the variation of the emissivity rate of typical surface in different seasons with wavelength and temperature.Typical surfaces included grass,sand,loess,river,ice and snow.By reading the relevant literature and analyzing the measurement method of emissivity,a method to obtain surface emissivity and surface temperature was proposed based on the data of MOD11B1.The emissivity rates of 6 thermal infrared bands in different regions and seasons were inverted under the ENVI Classic software environment from December 2015 to August 2016.The line charts of 11 340 indicator samples were drawn to analyze the variation trend of surface emissivity with wavelength.Using the HDF plug-in to read the typical surface temperature parameters,the data points of the surface temperature of 1 890 were obtained according to the missing data of the linear fitting supplement.The relationship between emissivity and temperature was analyzed by using Origin to make the surface emissivity curves with temperature.The results showed that the typical surface emissivity parameters of winter were the highest and the range of variation was small.The emissivity rates of the lawn,loess and river water were between 0.910 and 0.990,and the range of the sand was between 0.87 and0.99.The emissivities of ice and snow were between 0.965 and 0.985.The trend of surface emissivity of grass,sand,loess,river,ice surface and snow with temperature was wavy form within the range of 3~5 ?m.But the surface emissivity of the lawn,water,snow and ice surface did not change with temperature in the range of 8~12 ?m. |
PDF Full Text Request