Near-surface temperature difference (i.e., the difference between land surface skin and 2-m air temperatures—ΔT) drives numerous ecological and biophysical processes on Earth, constituting an essential parameter in process-based Earth System Modeling. ΔT 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. ΔT 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 ΔT in the Eastern Mediterranean (EM). ΔT 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 ΔT 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. ΔT 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 ΔT 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 ΔT. Findings from this study show promise for continuous spatiotemporal estimations of ΔT from land surface temperature and NDVI satellite data.
Bibliographical noteFunding Information:
The authors are grateful to the Israel Meteorological Service (https://ims.data.gov.il/) and the Israel Ministry of Agriculture (http://www.meteo.co.il/) for the surface meteorological data, to NASA (NASA LP DAAC at the USGS EROS Center) for the satellite data, and to Google Earth Engine (GEE) for the platform to retrieve the satellite (https://earthexplorer.usgs.gov/) and model data (https://rda.ucar.edu/datasets/ds094.0/). The authors are grateful to Shilo Shiff for providing the GEE code.
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- air temperature
- land surface temperature
- synoptic-scale circulation