Abstract
The thermal infrared (TIR) data from the Medium Resolution Spectral Imager II (MERSI-2) on the Chinese meteorological satellite FY-3D have high spatiotemporal resolution. Although the MERSI-2 land surface temperature (LST) products have good application prospects, there are some deviations in the TIR band radiance from MERSI-2. To accurately retrieve LSTs from MERSI-2, a method based on a cross-calibration model and split window (SW) algorithm is proposed. The method is divided into two parts: cross-calibration and LST retrieval. First, the MODTRAN program is used to simulate the radiation transfer process to obtain MERSI-2 and Moderate Resolution Imaging Spectroradiometer (MODIS) simulation data, establish a cross-calibration model, and then calculate the actual brightness temperature (BT) of the MERSI-2 image. Second, according to the characteristics of the near-infrared (NIR) bands, the atmospheric water vapor content (WVC) is retrieved, and the atmospheric transmittance is calculated. The land surface emissivity is estimated by the NDVI-based threshold method, which ensures that both parameters (transmittance and emissivity) can be acquired simultaneously. The validation shows the following: 1) The average accuracy of our algorithm is 0.42 K when using simulation data; 2) the relative error of our algorithm is 1.37 K when compared with the MODIS LST product (MYD11A1); 3) when compared with ground-measured data, the accuracy of our algorithm is 1.23 K. Sensitivity analysis shows that the SW algorithm is not sensitive to the two main parameters (WVC and emissivity), which also proves that the estimation of LST from MERSI-2 data is feasible. In general, our algorithm exhibits good accuracy and applicability, but it still requires further improvement.
Highlights
Temperature is one of the key physical parameters that characterize the energy transfer between various Earth layers
Thermal infrared (TIR) spectra are greatly affected by the atmosphere, but this spectral region can detect most of the energy directly emitted by the land surface, while passive microwaves can penetrate the cloud layer, which is affected very little by the atmosphere; studies on the mechanisms of microwave radiation from the surface are not yet mature [3]
TIR data have been the main data source for land surface temperature (LST) retrievals provided by spaceborne remote sensors, such as MODIS [6] and ASTER [7] on Terra/Aqua, AVHRR [8] on NOAA, TIRS [9] on Landsat 8, Visible Infrared Imaging Radiometer Suite (VIIRS) [10] on Suomi NPP, VIIRS [11] on FY-3, IRS [12] on HJ-1B and IRMSS [13] on GBERS-02
Summary
Temperature is one of the key physical parameters that characterize the energy transfer between various Earth layers. When the satellite data have two or more TIR channels with different transmittances and emissivities, at least two equations can be established to describe the heat radiation transfer process at the land surface At this stage, the unknown parameter, which is the average temperature of upward radiance of atmosphere, is eliminated, and the radiation transfer equation is simplified to retrieve the LST. The LST retrieval method proposed in this paper will promote the production of more accurate LST products from MERSI-2 data These products can be well applied in climate change, ecological environment, agriculture, and other fields and promote better data sharing services and international project cooperation
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