资源环境科技发展态势分析平台

Near-surface temperature difference (i.e., the difference between land surface skin and 2-m air temperatures-Delta T) drives numerous ecological and biophysical processes on Earth, constituting an essential parameter in process-based Earth System Modeling. Delta T is known to be governed by factors like incoming solar radiation and wind, which vary according to synoptic-scale circulation via horizontal pressure gradient and cloud cover. Delta T is also affected by land surface characteristics and vegetation dynamics. Here we assess the role of seasonality, synoptic-scale circulation, and vegetation dynamics, using satellite normalized difference vegetation index (NDVI) and latent heat estimates, on the Delta T in the Eastern Mediterranean (EM). Delta T was calculated using land surface temperatures derived from the Moderate Resolution Imaging Spectroradiometer and air temperatures measured at 94 meteorological stations in the EM for 2006-2010. The effect of circulation on Delta T is demonstrated for four synoptic categories covering all seasons, showing that the influence of synoptic-scale circulation may be sometimes stronger than that of the seasonal signal in this region. Delta T showed negative relationships with NDVI indicating that vegetation is attenuating the near ground temperature difference, with a gradual effect increasing from southern drylands to the more humid northern vegetated areas in the EM. The relationship between Delta T and NDVI was stronger for specific synoptic classes than for seasonal division, implying the combined role of vegetation cover dynamics and synoptic-scale conditions on Delta T. Findings from this study show promise for continuous spatiotemporal estimations of Delta T from land surface temperature and NDVI satellite data.