Estimation of the surface heat transfer coefficient over the east-central Tibetan Plateau using satellite remote sensing and field observation data

The bulk transfer method is commonly used to calculate the surface sensible heat (SSH) flux in climatology and in the numerical model, but in the calculation, the value of the bulk transfer coefficient for heat (Ch) is generally regarded as a fixed value (e.g., 0.004 in the Tibetan Plateau), without considering its seasonal variations and regional differences. In this study, a new method for upscaling data from the local to regional scale is proposed and tested to estimate Ch over the east-central Tibetan Plateau (TP) using the latest version Global Inventory Modeling and Mapping Studies (GIMMS), Normalized Difference Vegetation Index (NDVI) dataset, and micrometeorological observations collected at four field sites. Results suggest that the proposed method is capable of reflecting the variations in Ch at the regional scale in a climatic context. It is a relatively reliable way of estimating the value of Ch using satellite remote sensing data and field observations. Then, the monthly values of Ch and the SSH flux at 70 China Meteorological Administration (CMA) stations on the east-central TP during the period 1982–2012 are estimated. Results show that the value of Ch ranges from 0.0025–0.0050, with obvious seasonal variations and spatial differences. Because the surface vegetation coverage in the southeastern part of the TP is better than that in the north-central part, the values of Ch are higher than that in the north-central part of the TP throughout the year. The SSH flux also shows obvious seasonal variations and spatial differences, which is strongest in spring, followed by summer and autumn, and smallest in winter. Furthermore, the seasonal mean SSH has undergone a significant interdecadal transition in the early 2000s, from the previous weakening trend to the strengthening trend. Based on the results of this study, the values of Ch obtained from a limited number of local field observations on the plateau can be applied to more CMA stations at the regional scale. Such a method can improve the calculation accuracy of the SSH flux over the TP and aid studies of plateau meteorology and climatology.