Spatiotemporal Analysis of MODIS Land Surface Temperature With In Situ Meteorological Observation and ERA-Interim Reanalysis: The Option of Model Calibration

Abstract

The land surface temperature ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> ) is an important parameter in land surface and atmosphere studies. A set of synchronously observed “ground-truth” temperature as training data is required for some empirical/semiempirical statistical and neural network methods for retrieving <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> from passive microwave (PMW) remote sensing data. To provide information for the choice of the most suitable dataset in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts </i> retrieval of PMW remote sensing, the spatiotemporal comparison between the moderate-resolution imaging spectroradiometer <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> (MODIS <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> ), the meteorologically observed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ Ts</i> ), the meteorologically observed near-surface air temperature ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ Ta</i> ), and European Center for Medium-Range Weather Forecast reanalysis products, the ERA-Interim <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> (ERA <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> ), in South China for each season's daytime and nighttime is conducted in this paper. Results show that a large discrepancy between the MODIS <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ Ts</i> exists, whereas the discrepancies between the MODIS <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> , the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ Ta</i> and the ERA <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Ts</i> are relatively smaller in daytime. For nighttime period, the differences between each dataset are relatively much smaller. Because the MODIS <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> is representative at the satellite pixel scale, it has a smaller spatial-scale mismatch with PMW data compared to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> meteorological observation. The MODIS <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> is suitable for both the daytime and the nighttime PMW <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> model calibration if it is synchronously observed under almost clear-sky condition. By contrast, for the PMW <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> model calibration within the daytime period, the synchronously obtained <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ Ts</i> is not suitable to be used as training data. If the ground temperature of daytime period derived from PMW is required, but the MODIS <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Ts</i> is unavailable, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ Ta</i> should be selected as the “ground truth” for the model calibration. However, it should be noticed that the inversion results are the near-surface air temperature rather than the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> . Remarkably, reanalysis products such as the ERA <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> presents an alternative choice for both the daytime and the nighttime <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> model calibration if there are no MODIS <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> products or <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> temperature available. After the comparison, an example of PMW <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> retrieval for nighttime period was given, showing a promising performance on deriving an applicable PMW <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ts</i> inversion model based on the selection of an appropriate training dataset.