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Diurnal emissivity dynamics in bare versus biocrusted sand dunes
Offer Rozenstein1, Nurit Agam1, Carmine Serio2
1Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boker Campus, 84990, Israel.
The Science of the Total Environment
|December 2, 2014
Summary
Diurnal changes in land surface emissivity (LSE) are larger for biocrust-covered dunes than bare sand dunes. This finding, linked to moisture adsorption, impacts LSE estimations in global deserts.
Area of Science:
- Earth and Environmental Sciences
- Remote Sensing
- Geophysics
Background:
- Land surface emissivity (LSE) is crucial for geophysical models, influencing land surface temperature predictions.
- Accurate LSE derivation is essential, as it depends on ground cover and soil moisture.
- Biocrusts, common in deserts, differ from bare sand in their interaction with atmospheric moisture.
Purpose of the Study:
- To test if diurnal emissivity changes are greater over biocrust-covered areas compared to bare sand.
- To investigate the role of soil moisture and water vapor adsorption in LSE dynamics.
- To assess the global implications of biocrusts on LSE estimations.
Main Methods:
- Monitoring LSE dynamics using the Spinning Enhanced Visible and Infrared Imager (SEVIRI) from geostationary orbit.
- Comparing LSE fluctuations over biocrusted dunes (Israel) and bare sand dunes (Egypt).
- Analyzing LSE in the 8.7 μm channel for diurnal variations.
Main Results:
- Diurnal fluctuations in LSE were significantly larger for biocrusted dunes than for bare sand dunes.
- The increased LSE variation is attributed to water vapor adsorption by biocrusts and sand particles.
- LSE demonstrates sensitivity to minor soil water content changes, making it a quantifiable indicator.
Conclusions:
- Biocrusts enhance diurnal LSE variations due to moisture adsorption, impacting geophysical model accuracy.
- The findings have global repercussions for LSE estimations in desert environments.
- LSE variations due to biocrusts can significantly affect geophysical models at local to regional scales.
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