Exploring the physical mechanisms of the role of soil moisture, topography, and diurnal cycle of insolation on S2S precipitation in the Maritime Continent

Despite its significant role in the global climate, the Maritime Continent (MC) remains somewhat of an enigma due to a lack of physical understanding and model performance. The MC connects the Indian and Pacific Oceans, and tropics and extratropics through teleconnections. It also acts as a predictability barrier for subseasonal-to-seasonal (S2S) prediction of precipitation that depends on many interacting processes including the land-atmosphere interactions, which are controlled through soil moisture, topography, and diurnal cycle of insolation, among others. Many of these processes, however, are poorly understood and inadequately represented in weather and climate models. In this work, we propose: (i) to describe the observed relationship between the S2S precipitation and other parameters such as soil moisture, topography, and diurnal cycle of insolation; (ii) to explore the relative contribution of soil moisture, topography, and diurnal cycle of insolation; (iii) to investigate the role of nonlinear interactions between soil moisture and insolation, and between topography and insolation on the S2S precipitation using a novel factor separation method from set theory; and (iv) to find how much bias in simulated S2S precipitation comes from the bias in the diurnal cycle of precipitation in the MC. To achieve these objectives, we will leverage a combination of NOAA and other observations, cutting-edge reanalysis products, a series of high-resolution cloud-permitting simulations using a limited-area model, and relatively coarse-resolution simulations using general circulation models. We will also use process-oriented model diagnostics (that were developed as part of prior NOAA grants) in combination with budget analyses of moisture and moist static energy to achieve our overarching goal of understanding the physical processes that modulate S2S precipitation in the MC.