Weakening sensible heat source over the Tibetan Plateau revisited: effects of the land–atmosphere thermal coupling
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The bulk heat transfer coefficient (C H ) indicates the land–atmosphere thermal coupling strength. We seek to detect its variability and changes on the Tibetan Plateau (TP) during 1981–2006, particularly concerned with its effects on the sensible heat source. C H is parameterized by Monin–Obukhov similarity theory combining routine meteorological measurements. The South Asian monsoon period is characterized by weak sensible heat flux (H), but strong thermal coupling (C H ). Winter sees the greatest diurnal C H range, roughly 0.001–0.008. On average, C H exhibits a notable nighttime increase (10% decade−1) and a weak daytime decrease (−5% decade−1). The strengthening thermal coupling at selected sites alleviates the weakening of H, because it enhances nighttime H increase and reduces daytime H decrease. Moreover, we confirm the finding in earlier studies that sensible heating is weakening on the TP, but find its trend less notable than empirically estimated using C H = 0.004.
KeywordsTibetan Plateau Climate Sensitivity Physical Approach Thermal Coupling China Meteorological Administration
Critical comments by two anonymous referees greatly benefited our presentation and revisions in general. The authors are indebted to the China Meteorological Administration for providing the long-term dataset (http://cdc.cma.gov.cn/ ). Our colleague Lin Zhang offered a Java-based applet that facilitated our preparation of the multi-panel figures; Jie He helpfully prepared a DEM topography dataset. This study is jointly funded by the Chinese Academy of Sciences (CAS Innovation Project KZCX2-YW-145), China Postdoctoral Science Foundation (Grant 20090450056), and National Natural Science Foundation of China (Grant 40810059006). Xiaofeng Guo gratefully acknowledges the support of K. C. Wong Education Foundation, Hong Kong.
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