Wednesday, 10 January 2018: 3:30 PM
Room 16AB (ACC) (Austin, Texas)
Irrigated plantations and modified terrain can provide a sustainable means of enhancing convective rainfall in arid regions like the United Arab Emirates, or UAE, and can be used to aid ongoing cloud seeding operations through the geographic-localization of seedable cloud formation. The first method, the planting of vast irrigated plantations of hardy desert shrubs increases roughness and modifies radiative balances. When efficient deficit irrigation methods are used, a heat-low can develop over the canopy, leading to surface wind convergence, as well as strong vertical mixing through increased thermal and mechanical turbulence. When upper-air atmospheric instability is present, these phenomena can together initiate convection. The second method, increasing the elevation of moderate-sized mountains, is based on the correlation between elevation and the number of summertime convection initiation events observed in the mountains of the UAE and Oman. This augmentation of existing terrain features should therefore increase the likelihood and geographic range of convection initiation events, through modified orographic flows and greater forced ascent. High-resolution simulations provide a powerful means of assessing the likely impacts of these land surface modifications. Previous convection-permitting simulations have yielded some evidential support for these hypotheses, but higher resolutions down to 1 km provide more detail regarding convective processes and land surface representation.
Using seasonal simulations with the WRF-NOAHMP land-atmosphere model at a 2.5 km resolution, we identify frequent zones of convergence and atmospheric instability in the UAE and select interesting cases. Using these results, as well as an agricultural feasibility study, we identify optimal plantation positions within the UAE. We then run realistic plantation scenarios for single case studies at 1 km resolution. Using the same cases, we simulate the impact of augmenting mountain elevations on convective processes, with the augmentation being achieved through GIS-based modification of the terrain data. For both methods, we assess the impacts quantitatively and qualitatively, and assess key processes and dependencies.
By demonstrating that convective rainfall would be enhanced through feasible agricultural and engineering methods, then land surface-based weather modification deserves serious consideration as a solution for water scarcity and anthropogenic climate change.
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