Reduction of tropical land region precipitation variability 2 via transpiration

7 [1] Tropical rainforests are known to exhibit low intrasea8 sonal precipitation variability compared with oceanic areas 9 with similar mean precipitation in observations and models. 10 In the present study, the potential role of transpiration for 11 this difference in precipitation variability is investigated 12 using the National Center for Atmospheric Research 13 (NCAR) atmospheric general circulation model. Comparing 14 model results with and without transpiration shows that in 15 the absence of transpiration, mean precipitation decreases as 16 may be expected. However the incidence of both higher 17 daily total column water and more intense precipitation 18 increases without transpiration; consequently the variability 19 of precipitation increases substantially. These results can be 20 understood in terms of the complex interplay of local near21 surface and remote moist dynamical processes with both 22 local positive (boundary-layer drying) and large-scale neg23 ative (increased large-scale convergence) feedbacks when 24 transpiration is disabled in the model. It is also shown that 25 surface turbulent fluxes over tropical rainforests are highly 26 correlated with incoming solar energy but only weakly cor27 related with wind speed, possibly decoupling land precipi28 tation from large-scale disturbances like Madden-Julian 29 Oscillation. Citation: Lee, J.-E., et al. (2012), Reduction of trop30 ical land region precipitation variability via transpiration, Geophys. 31 Res. Lett., 39, LXXXXX, doi:10.1029/2012GL053417.