干旱区生态环境知识资源中心

Recent advances in technology permit the irrigation of dry, coastal areas, avoiding the use of fossil water and conflicts with other land use (e.g., for food production). Consequently, it becomes reasonable to consider large-scale plantations for mitigating increases in atmospheric concentrations by carbon sequestration and to study local modifications of weather and climate. This work investigates the impact of plantations in Oman and the Sonora Desert in Mexico assuming an area of about 100 km x 100 km. For this purpose, an advanced land surface-atmosphere model was adapted to the local changes of land cover and operated on the convection-permitting scale. Explicit simulations of the impact of the plantation on soil-vegetation-atmosphere feedback were performed for a duration of 1 yr. A strong modification of diurnal cycles of variables such as surface fluxes, temperature, and boundary layer depth was found. Over the plantations, the mean temperature decreased as a result of nonlinear changes of the diurnal cycle caused by less warming during the day than cooling during the night. Moreover, the plantations caused an increase in vertical instability and a modification of the horizontal flow leading to the development of convergence zones. During several isolated cases in summer, this process led to convection initiation and precipitation with an enhancement of about 30 mm in both areas, respectively. These convection-permitting simulations lend confidence that an increase in precipitation could be induced at the mesoscale by the introduction of vegetation in desert regions. Furthermore, this effect should be included in a quantitative assessment of climate engineering by afforestation.