Diurnal Cycle and Dipolar Pattern of Precipitation Over Borneo During the MJO: Linear Theory and Nonlinear Sensitivity Experiments

Abstract

The precipitation anomaly over Borneo features a dipolar pattern under the influence of the Madden‐Julian Oscillation (MJO). To understand the formation mechanisms of this pattern, a linear theory is developed to study the factors controlling its diurnal cycles and the dipolar pattern. The theory predicts that the prevailing wind is primarily responsible for the asymmetry over an idealized island, while the topography plays a critical role in the leeward convergence and convection asymmetry. The results are largely consistent with the observed composites of the dipole at Borneo. Nonlinear cloud‐permitting simulations are further conducted to test the effects of island topography and solar radiative heating in different MJO phases. The results show that the island topography can cause the mesoscale flow to split around the mountain due to the topographic blocking, and favor the development of the lee side sea breeze. These processes strengthen the low‐level convergence and convection at the leeside of the island during the late afternoon and night, which is very important to the formation of island dipolar precipitation anomaly. In contrast, the inland convergence is weakened and the dipole disappears when the terrain is flattened. The diurnal cycle of solar insolation is the dominant factor driving the land‐sea breeze circulation, which intensifies the island convection at the leeside. These results indicate that the MJO wind anomaly, island topography and solar insolation play distinct roles in the formation of the dipolar pattern of Borneo precipitation.

A Preliminary Study on the Parameter Configuration of Weather Research Forecasting in Tropical Peatland, Central Kalimantan

“…First, the number of stations for bias correction was not distributed evenly throughout the study site. This may disregard the influence of sea breeze on rainfall formation (Zhou et al, 2023) and temperature especially in the southern part. During dry season strong winds often occur, which trigger high land temperatures (Usup and Hayasaka, 2023), that is not captured by the available weather stations.…”

Offshore Migration of Summer Monsoon Low‐Level Jet on a Diurnal Scale

“…High‐resolution model simulations, incorporating the analysis of vertical shear components, would be the most effective approach to address the complexities of the studied phenomena. Given the significant impact of topography on offshore propagation rainfall (Zhou et al., 2023), it would be intriguing to investigate the influence of topography in offshore LLJs through sensitivity experiments. The findings in the present study deepen our understanding of the complex dynamics of the southwesterly monsoon LLJ and provide a basis for future research on the regional monsoon system.…”

Convection-permitting regional climate simulations over coastal regions in China

“…During the summer, the dominant winds along the eastern coast of China are southeast winds, which have a significant impact on the coastal climate. When studying the land-sea breeze variations, we exclude the background large-scale systems such as the East Asian monsoon for the sake of convenience, while acknowledging that the land/sea breeze is also influenced by prevailing wind associated with large-scale systems (e.g., see Zhou et al 2022Zhou et al , 2023. The range of selected breeze directions also varies according to the coastline orientation.…”

“…The different dominant rainfall factors between offshore and coastal areas lead to the difference in the characteristics of land and sea precipitation. Zhou et al (2022Zhou et al ( , 2023 indicated that either thermally or mechanically forced mesoscale local circulation can interact with convection, shaping the spatial pattern and diurnal variations of the precipitation around the tropical island. Du and Rotunno (2018) focused on the diurnal precipitation and wind characteristics manuscript submitted to Climate Dynamics on the Guangdong coast, and showed the diverse onshore and offshore propagation patterns of the diurnal precipitation.…”