An Analysis of the Moisture and Moist Static Energy Budgets in AMIP Simulations
An analysis of the second phase of the Atmospheric Model Intercomparison Project (AMIP) simulations has been conducted to understand the physical processes that control precipitation in the tropics. This is achieved primarily through the analysis of the moisture and moist static energy budgets. Overall, there is broad agreement between the simulated and observed precipitation, although specific tropical regions such as the Maritime Continent poses challenges to these simulations. The models in general capture the latitudinal distribution of precipitation and key precipitating regions including the Inter-Tropical Convergence Zone (ITCZ) and the Asian Monsoon. The simulations portrayed the global patterns of evaporation and precipitation relatively accurately, confirming that the ocean was the primary source of evaporation. The ensemble of simulations proved to be the most reliable simulation of the moisture budget globally, within the tropics, and the Maritime Continent. A strong relationship between precipitation and vertical advection, or horizontal convergence, is seen among the observations and simulations. Some simulations were more successful than others in reproducing the largest amount of rainfall over the islands in the Maritime Continent. The moist static energy budget proved difficult to simulate without large residual values, both in the tropics and the Maritime Continent. The total radiation and surface heat flux displayed lesser values of outgoing radiation and incoming surface heat, respectively, across major precipitation and convergence regions such as the ITCZ and the Indian Monsoon. The residual values were often smaller over areas of larger precipitation, such as the ITCZ, but spiked in value elsewhere. This resulted in a larger overall residual value for the tropical region, but a slightly smaller residual over the Maritime Continent as larger residual spikes fell further afield. However, considering the overall size of the residual values, the observations and simulations are not successful at demonstrating the moist static energy budget.