Adventures in Weather Modification Using Intelligent Land-Use Change

Manipulation of microphysical processes, e.g. with cloud seeding, remains the predominant focus of regional weather modification research. However, scenarios involving land-surface perturbations, such as land-use change and various technology-based methods are increasingly being considered, especially within water-scarce regions. Purpose-designed vegetated or artificial surfaces can be used to induce moist convection through modified land-atmosphere feedbacks - a method termed here as land-use weather modification. Previous simulations suggest that these methods could be extremely effective, but also that only certain atmospheric conditions are likely to be suitable for land-use weather modification. Until now, a reliable method for identifying and categorizing suitable regions had not been devised.

Through high-resolution seasonal simulations, validated with measurements, we demonstrate that purpose-designed land use changes can enhance convective rainfall, and we describe the underlying process chain. We discover that even modest-sized areas of land-use change (down to ~10 km²) are sufficient to induce significant rainfall impacts – an exciting prospect regarding implementation feasibility. We conduct a seasonal statistical analysis of simulated impacts in seemingly similar arid regions and found, somewhat counter intuitively, that there are regions with very high and very low potential, even assuming identical land perturbations. By quantifying why this is so, we derive a global-feedback index for predicting regional impacts based on atmospheric conditions. Then, through monthly mapping we find that some hot deserts are more suitable than others, with the highest potential usually occurring during hemispheric-summer. Only a few regions have high potential, year-round – the central Sahara Desert and the southern Arabian Peninsula. Other desert zones become conducive only in summer or monsoon seasons, including the Sonoran Desert, Pakistan, north-western Australia, and the Namibia region.

Thus, land-use weather modification methods at feasible scales could be a predictable method for intensifying convection, although only real-world implementation can confirm their efficacy. Through this new global-feedback index we can focus further research and eventual implementation in regions where the strongest convective impacts will occur. Through these results, we are convinced that land-use based rainfall enhancement should be made a high research priority within the weather modification science community.