Influence of Topography on the Precipitation and its Diurnal Cycle in the Maritime Continent

Understanding the multi-scale interactions between the diurnal cycle in the Maritime Continent (MC) and large-scale circulations remain a challenge to the atmospheric community. The problem is further exacerbated by the fact that most models have difficulty in simulating the precipitation over the MC, presumably due to error from model physics and resolution that has to deal with the complex topography of the MC. The goal of this study is to understand the role of topography on the precipitation and its diurnal cycle in the MC using a series of sensitivity experiments using the WRF model.

In the control simulation, we integrate the model over the MC (20°S to 20°N, 80°E to 170°E) at 12km horizontal grid spacing for the month of April, 2009 which falls within the Year of Tropical Convection (YOTC). During this time, an MJO event crossed the MC. The model was able to capture the precipitation when compared with observations (TRMM). In the first set of sensitivity experiment, we remove the topography above 2m, 1000m, and 2000m respectively to demonstrate the role of topography in the MC. In second set of experiments, we remove one major island at a time (Sumatra, Borneo, and New Guinea) and all the islands inside the model domain to demonstrate the influence of individual islands in the MC. In the third set of experiments, we use different topographic data sets with different resolutions to show the sensitivity of our results on the accuracy of representation of topography in the model. The results from these three sets of experiments and their implications will be discussed in the meeting.