High-Resolution Image

A "Neil Armstrong" footprint in the middle of somewhere - Moon? Desert? Does this have anything to do with Climate and Radiation research? Indeed, it does... The photograph and measurements were taken in an aged-desert area (The Great Gobi) surrounding the Dunhuang Oasis, China, during the ACE-Asia field experiment in 2001. In this particular case the undisturbed surface is covered by small dark-colored gravel that acts as a shield suppressing external forcing of wind blowing. However, if the surface is disturbed by footprints, the fine sand from underneath is exposed freely, and consequently can be blown by the wind and transported long distances. An example of such long-range transport was documented by TOMS' aerosol measurements (Hsu et al. 2004) and also displayed in the "Planet Earth" calendar - May 2004. In turn, our innocent actions of footprinting, rather than natural forcing of topographic lifting, dynamic overturning, etc, may contribute extra "Kosa" (yellow sand - Japanese) to the Asian dust storms. In addition, the fine sand area is spectrally brighter than the surrounding coarse gravel. The implication is that the solar radiation energy is reflected back to space more from the surface of young deserts (fine-grain sands) than from the aged deserts (coarse-size gravel). This affects the distribution of diabatic heating in the atmosphere-surface system and may cause regional-to-global impact on weather and climate.

We, the Goddard ACE-Asia team, feel sorry to have left footprints in the desert; but hey, the wolf pack wandering around our measurement site also left tracks... a complex story of an ecosystem. - by Q. Jack Ji and Si-Chee Tsay.

*Hsu, N.C., S.-C. Tsay, M. D. King, J. R. Herman, Q. Ji, and J.-J. Liu, 2004, Inferring Asian Dust Properties over deserts from Satellites: A New Approach, in submission to Journal of Geophysical Research.