Abstract
The ground surface soil heat flux (G0) quantifies the energy transfer between the atmosphere and the ground through the land surface. However; it is difficult to obtain the spatial distribution of G0 in permafrost regions because of the limitation of in situ observation and complication of ground surface conditions. This study aims at developing an improved G0 parameterization scheme applicable to permafrost regions of the Qinghai-Tibet Plateau under clear-sky conditions. We validated several existing remote sensing-based models to estimate G0 by analyzing in situ measurement data. Based on the validation of previous models on G0; we added the solar time angle to the G0 parameterization scheme; which considered the phase difference problem. The maximum values of RMSE and MAE between “measured G0” and simulated G0 using the improved parameterization scheme and in situ data were calculated to be 6.102 W/m2 and 5.382 W/m2; respectively. When the error of the remotely sensed land surface temperature is less than 1 K and the surface albedo measured is less than 0.02; the accuracy of estimates based on remote sensing data for G0 will be less than 5%. MODIS data (surface reflectance; land surface temperature; and emissivity) were used to calculate G0 in a 10 x 10 km region around Tanggula site; which is located in the continuous permafrost region with long-term records of meteorological and permafrost parameters. The results obtained by the improved scheme and MODIS data were consistent with the observation. This study enhances our understanding of the impacts of climate change on the ground thermal regime of permafrost and the land surface processes between atmosphere and ground surface in cold regions.
Highlights
The total area of the Qinghai-Tibet Plateau (QTP) is approximately 2.57 million km2 and it has an average elevation of over 4000 m [1]
It is estimated that 54.3% of the QTP is located in permafrost regions, which is vulnerable to thawing due to ongoing climate change [2]
From the mathematical forms of the SEBALadj and Maadj parameterization schemes (Table 4), it can be seen that the simulated G0 of the two schemes will always be less than 0 in the daytime when the vegetation index (NDVI or MSAVI) is high and land surface temperature Ts is higher than 0, which is inconsistent with the actual situation., which is inconsistent with the actual situation
Summary
The total area of the Qinghai-Tibet Plateau (QTP) is approximately 2.57 million km and it has an average elevation of over 4000 m [1]. G0 manifests the energy exchange between the active layer and the atmosphere and it affects the energy budget of the active layer and permafrost, so it is important to understand the freeze-thaw process that takes place within the ground surface in the QTP region, as well as degradation or development of permafrost through time [11]. This type of analysis requires the effective parameterization of ground surface soil heat flux [12]
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