Estimating clear-sky land surface longwave upwelling radiation from MODIS data using a hybrid method

ABSTRACT

Surface longwave upwelling radiation (LWUP) is one of the four components for calculating the earth’s surface radiation budget. Under the general framework of the hybrid method, we developed linear models for estimating the global 1-km instantaneous clear-sky LWUP from the top-of-atmosphere (TOA) radiance of the Moderate Resolution Imaging Spectroradiometer (MODIS) thermal infrared channels 29, 31, and 32. Extensive radiative transfer simulations were conducted to produce a large number of representative samples, from which the linear model was derived. The derived hybrid model was first evaluated using ground measurements collected at 15 sites from two networks (SURFRAD and ASRCOP). According to the validation results, the average bias and root mean square error (RMSE) of −0.55 and 15.76 W m⁻², respectively, were obtained by averaging the mean bias and RMSE for the two networks. Compared to a hybrid method developed by a previous study and the temperature-emissivity method, our linear model had a superior performance.

Acknowledgements

The MODIS data were obtained from https://wist.echo.nasa.gov/api/. The in situ data were obtained from SURFRAD (http://www.srrb.noaa.gov/surfrad) and ASRCOP (http://observation.tea.ac.cn/). This work was partly supported by the National Natural Science Foundation of China [grant 41371323], the Beijing Higher Education Young Elite Teacher Project [grant YETP0233], and the International S&T Cooperation Programme of China [grant 2012DFG21710].

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was partly supported by the National Natural Science Foundation of China [grant 41371323], the Beijing Higher Education Young Elite Teacher Project [grant YETP0233], and the International S&T Cooperation Programme of China [grant 2012DFG21710].