Sensitivity of cloud‐resolving precipitation simulations to uncertainty of radiation calculation: Effects of large‐scale forcing

Abstract

AbstractThe sensitivity of precipitation simulations to the uncertainty of radiation calculation is examined through the analysis of two sets of sensitivity experiments imposed by large‐scale forcing from weak tropical rainfall (weak forcing) and pre‐summer heavy rainfall events (strong forcing). Several simulations with perturbed solar and infrared radiative heating in different vertical layers are compared to a control simulation. In the weak‐forcing case, the precipitation simulation is more sensitive to the uncertainties of solar radiation calculation and less sensitive to the uncertainties of infrared radiation calculation in the lower troposphere than in the upper troposphere. In the strong‐forcing case, precipitation simulation is insensitive to the uncertainty of solar radiation calculation, but is more sensitive to the uncertainty of infrared radiation calculation in the lower troposphere than in the upper troposphere. The precipitation simulation is more sensitive to the uncertainty of radiation calculations in the weak‐forcing case than in the strong‐forcing case. Simulated precipitation sensitivity to perturbations in lower‐tropospheric radiative heating is associated with changes in water vapour convergence and condensation. The analysis of root‐mean‐squared difference and standard deviation shows that the root‐mean‐squared differences are similar in the two cases, but the increased magnitude in upward motion significantly causes a large rainfall fluctuation and also causes a larger standard deviation in the strong‐forcing case than in the weak‐forcing case. As a result, the increase in magnitude of upward motions leads to a decrease in the sensitivity of the precipitation simulation to the uncertainty of radiation calculation.