Evaluating the Estimation of Net Radiation Based on MODIS Data and CoLM: A Case Study in the Tibetan Plateau

Estimation of net radiation is essential for characterization of the land-atmosphere energy and water exchange processes of the Tibetan Plateau. Two methods are commonly used to estimate the net radiation. Method 1 relies on ground measurements and earth satellite observations, and method 2 relies on the use of a land surface model. Currently, there is no consensus on regarding which of these two methods is the most accurate. In this study, we evaluated net radiation calculated by MODIS land surface temperature products, combined with ground-based incoming shortwave and longwave radiation and albedo measurements, and compare this to performance of the common land model for modeling surface net radiation for the Muztaga site located in the northwest of the Tibetan Plateau at three timescales (half-hourly, hourly, and daily). The results show that the two methods provide similar results, and both methods provide estimates that are notably higher than ground-measured net radiation validations at three different timescales. Estimates of net radiation obtained at half-hourly and hourly timescales closely match the fluctuations in the reference data. However, the daily timescale is too coarse to capture the short-term fluctuations. Thus, this study demonstrates that the shorter timescales are preferred in determining surface net radiation. In addition, compared with method 2, method 1 is more accurate for each of the different timescales.