Preliminary Calculations for High-Resolution Regional Mapping of Cloud Water Deposition and Water Sustainability for Vegetation

The mapping of the degree of dryness (aridity) is the most critical information to define arid areas. A new methodology to evaluate an index of Water Sustainability for Vegetation (WSV) is proposed in the present study. WSV is proposed using a combination of meteorological and land surface model considering surface runoff and cloud water (fog) deposition on vegetation. WSV is defined as the ratio of water supply to demand by vegetation, where water supply is estimated considering rainfall, surface runoff and fog deposition on vegetation, and water demand is evapo-transpiration on the assumption that vegetation is activated. Simulations using a three-dimensional mesoscale meteorological model (MM5) were employed to make the current meteorological fields. At each simulation grid, fog deposition on vegetation and WSV were quantified by a detailed land surface model (SOLVEG) for several vegetation species, such as glasslands, shrublands, and woodlands. This method was applied to develop the high spatial resolution (6 km) maps of fog deposition on vegetation and WSV at arid areas in West Asia. At the coastal areas with high altitudes along the Red Sea, tall trees captured a large amount of fog water (more than 60 mm yr- 1, corresponding to 30 % of precipitation). Results showed that water supply from fog has an important role in tall trees surviving. The spatial distribution of WSV corresponded to the current vegetative areas without anthropogenic effects. WSV calculated by a combination of the meteorological model and land surface model including fog deposition is effective to evaluate water availability for plants surviving under arid and semi-arid environments.