Impact of islands on the MJO propagation across the maritime continent: a numerical modeling study of an MJO event

Zhou, Yihao; Fang, Juan; Wang, Shuguang

doi:10.1007/s00382-021-05849-y

Cited by 7 publications

(12 citation statements)

References 56 publications

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“…Though some studies have already performed similar terrain modifications as what we show here (H. Tan et al, 2022;Zhou et al, 2021), we go a step further and separate the effects of MC topography from the effects of its DC and land-sea contrast and identify physical processes through which those impact MJO propagation. The modeling configuration, MJO tracking, and our unique way of analyzing the DC of precipitation are described in Section 2.…”

Section: Introductionmentioning

confidence: 85%

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Land-Locked Convection as a Barrier to MJO Propagation across the Maritime Continent

Savarin

Chen

2022

Preprint

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Large-scale convection associated with the Madden-Julian Oscillation (MJO) initiates over the Indian Ocean and propagates eastward across the Maritime Continent (MC). Over the MC, MJO events are generally weakened due to complex interactions between the large-scale MJO and the MC landmass. The MC barrier effect is responsible for the dissipation of 40-50\% of observed MJO events and is often exaggerated in weather and climate models. We examine how MJO propagation over the MC is affected by two aspects of the MC -its land-sea contrast and its terrain. To isolate the effects of mountains and landsea contrast on MJO propagation, we conduct three high-resolution coupled atmosphere-ocean model experiments: 1) control simulation (CTRL) of the 2011 November-December MJO event, 2) flattened terrain without MC mountains (FLAT), and 3) no-land simulation (WATER) in which the MC islands are replaced with 50 m deep ocean. CTRL captures the general properties of the diurnal cycle of precipitation and MJO propagation across the MC. The WATER simulation produces a more intense and smoother-propagating MJO compared with that of CTRL. In contrast, the FLAT simulation produces much more convection and precipitation over land (without mountains) than CTRL, which results in a stronger barrier effect on MJO propagation. The land-sea contrast induced land-locked convection weakens the MJO's convective organization. The land-locked convective systems over land in FLAT are more intense, grow larger, and last longer, which is more detrimental to MJO propagation over the MC, than the mountains that are present in CTRL.

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Section: Introductionmentioning

confidence: 85%

“…But at higher resolution, many studies that modify the DC in one way or another find that weakening the diurnal cycle over land leads to a weaker barrier to MJO propagation (e.g., Hagos et al, 2016;Oh et al, 2013;H. Tan et al, 2022;Zhou et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Land-Locked Convection as a Barrier to MJO Propagation across the Maritime Continent

Savarin

Chen

2022

Preprint

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“…But at higher resolution, many studies that modify the DC in one way or another find that weakening the DC over land leads to a weaker barrier to MJO propagation (e.g., Hagos et al, 2016;Oh et al, 2013;H. Tan et al, 2022;Zhou et al, 2021).…”

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confidence: 99%

Land‐Locked Convection as a Barrier to MJO Propagation Across the Maritime Continent

Savarin

Chen

2023

J Adv Model Earth Syst

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The Maritime Continent (MC) is a unique region of thousands of islands in the tropical Pacific warm pool with a very dynamic distribution of topography and terrain, and one of the main drivers of the global general circulation (Ramage, 1968). It lies at the intersection of many scales of atmospheric and oceanic variability, from decadal (El Niño-Southern Oscillation), to seasonal (monsoons), intraseasonal (the Madden-Julian Oscillation (MJO), Madden & Julian, 1971, 1972, and some of the strongest diurnal cycles in the world (Moron et al., 2015). Kikuchi and Wang (2008) classify the diurnal cycle (DC) over the MC into the coastal regime under which systems of land-and sea-breezes drive precipitation location and intensity, modified by the background circulation, orography, and coastline orientation (Abbs & Physick, 1992). Differential solar heating during the day induces a sea breeze circulation around islands and precipitation begins to form on the coast, then propagate inland from noon to evening; precipitation over the neighboring oceans is suppressed (Miller et al., 2003

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“…(2022) or Zhou et al. (2021). Only one domain is used for HYCOM, which is slightly larger than D01 in WRF model.…”

Section: Nonlinear Model Simulationsmentioning

confidence: 99%

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

2023

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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.

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Impact of islands on the MJO propagation across the maritime continent: a numerical modeling study of an MJO event

Cited by 7 publications

References 56 publications

Land-Locked Convection as a Barrier to MJO Propagation across the Maritime Continent

Land-Locked Convection as a Barrier to MJO Propagation across the Maritime Continent

Land‐Locked Convection as a Barrier to MJO Propagation Across the Maritime Continent

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

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