scholarly journals Role of convection–circulation coupling in the propagation mechanism of the Madden–Julian Oscillation over the Maritime Continent in a climate model

2021 ◽  
Author(s):  
Yi-Chi Wang ◽  
Wan-Ling Tseng ◽  
Huang-Hsiung Hsu
Keyword(s):  
Climate Model ◽  
Environmental Changes ◽  
Deep Convection ◽  
Ocean Model ◽  
Cumulus Parameterization ◽  
Propagation Mechanism ◽  
Madden Julian Oscillation ◽  
Moist Convection ◽  
Maritime Continent

AbstractThis study investigates the role of convection–circulation coupling on the simulated eastward propagation of the Madden–Julian Oscillation (MJO) over the Maritime Continent (MC). Experiments are conducted with the European Centre Hamburg Model Version 5 (ECHAM5) coupled with the one-column ocean model—Snow-Ice-Thermocline (SIT) and two different cumulus schemes, Nordeng-Tiedtke (E5SIT-Nord) and Tiedtke (E5SIT-Tied). During the early phase of MJO composites, the E5SIT-Nord simulation reveals stronger intraseasonal anomalies in the apparent heat source (Q1) over the convective center, however, the E5SIT-Tied produces a stronger background Q1, suggesting that deep convection prevails over the MC but does not couple with the MJO circulation. Similarly, in the E5SIT-Tied simulation, in-column moisture is kept mostly by local deep convection over the MC, which is in contrast to the well-correlated relationship between moisture anomaly and MJO circulation in E5SIT-Nord. A case study based on an observational MJO reveals similar biases concerning of convection–circulation coupling emerges within a few days of simulations. The E5SIT-Tied simulation produces weaker heating at the convective center of the MJO than the E5SIT-Nord a few days after model initiation, resulting weaker subsidence to the east and less favorable for propagation. The present findings highlight the instantaneous responses of cumulus parameterization schemes to MJO-related environmental changes can further affect intraseasonal variability through altering convection–circulation coupling over the MC. Physical schemes of moist convection are essential to realistically represent this coupling and thereby improve the simulation of the eastward propagation of the MJO.

Role of Convection–circulation Coupling in the Propagation Mechanism of the Madden–Julian Oscillation over the Maritime Continent in Climate Models

2021 ◽  
Author(s):  
Yi-Chi Wang ◽  
Wan-Ling Tseng ◽  
Huang-Hsiung Hsu
Keyword(s):  
Climate Models ◽  
Environmental Changes ◽  
Deep Convection ◽  
Ocean Model ◽  
Cumulus Parameterization ◽  
Propagation Mechanism ◽  
Madden Julian Oscillation ◽  
Moist Convection ◽  
Maritime Continent

Abstract This study investigates the role of convection–circulation coupling on the simulated eastward propagation of the Madden–Julian Oscillation (MJO) over the Maritime Continent (MC). Experiments are conducted with the European Centre Hamburg Model Version 5 (ECHAM5) coupled with the one-column ocean model – Snow-Ice-Thermocline (SIT) and two different cumulus schemes, Nordeng (E5SIT-Nord) and Tiedtke (E5SIT-Tied). During the early phase of MJO composites, the E5SIT-Nord simulation reveals stronger intraseasonal anomalies in the apparent heat source (Q1) over the convective center, however, the E5SIT-Tied produces a stronger background Q1, suggesting that deep convection prevails over the MC but does not couple with the MJO circulation. Similarly, in the E5SIT-Tied simulation, in-column moisture is kept mostly by local deep convection over the MC, which is in contrast to the well-correlated relationship between moisture anomaly and MJO circulation in E5SIT-Nord. A case study based on an observational MJO reveals similar biases concerning of convection–circulation coupling emerges within a few days of simulations. The E5SIT-Tied simulation produces weaker heating at the convective center of the MJO than the E5SIT-Nord a few days after model initiation, resulting weaker subsidence to the east and less favorable for propagation. The present findings highlight the instantaneous responses of cumulus parameterization schemes to MJO-related environmental changes can further affect intraseasonal variability through altering convection–circulation coupling over the MC. Physical schemes of moist convection are essential to realistically represent this coupling and thereby improve the simulation of the eastward propagation of the MJO.

scholarly journals Role of Maritime Continent Convection during the Preconditioning Stage of the Madden-Julian Oscillation Observed in CINDY2011/DYNAMO

2015 ◽  
Vol 93A (0) ◽  
pp. 101-114 ◽  
Author(s):  
Hisayuki KUBOTA ◽  
Kunio YONEYAMA ◽  
Jun-Ichi HAMADA ◽  
Peiming WU ◽  
Agus SUDARYANTO ◽  
...  
Keyword(s):  
Madden Julian Oscillation ◽  
Maritime Continent

scholarly journals Role of Maritime Continent Land Convection on the Mean State and MJO Propagation

2020 ◽  
Vol 33 (5) ◽  
pp. 1659-1675 ◽  
Author(s):  
Min-Seop Ahn ◽  
Daehyun Kim ◽  
Yoo-Geun Ham ◽  
Sungsu Park
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Critical Role ◽  
Moisture Gradient ◽  
Moisture Distribution ◽  
Boreal Winter ◽  
Maritime Continent ◽  
The Mean

AbstractThe Maritime Continent (MC) region is known as a “barrier” in the life cycle of the Madden–Julian oscillation (MJO). During boreal winter, the MJO detours the equatorial MC land region southward and propagates through the oceanic region. Also, about half of the MJO events that initiate over the Indian Ocean cease around the MC. The mechanism through which the MC affects MJO propagation, however, has remained unanswered. The current study investigates the MJO–MC interaction with a particular focus on the role of MC land convection. Using a global climate model that simulates both mean climate and MJO realistically, we performed two sensitivity experiments in which updraft plume radius is set to its maximum and minimum value only in the MC land grid points, making convective top deeper and shallower, respectively. Our results show that MC land convection plays a key role in shaping the 3D climatological moisture distribution around the MC through its local and nonlocal effects. Shallower and weaker MC land convection results in a steepening of the vertical and meridional mean moisture gradient over the MC region. The opposite is the case when MC land convection becomes deeper and stronger. The MJO’s eastward propagation is enhanced (suppressed) with the steeper (lower) mean moisture gradient. The moist static energy (MSE) budget of the MJO reveals the vertical and meridional advection of the mean MSE by MJO wind anomalies as the key processes that are responsible for the changes in MJO propagation characteristics. Our results pinpoint the critical role of the background moisture gradient on MJO propagation.

Structure of the Madden–Julian Oscillation in the Superparameterized CAM

2009 ◽  
Vol 66 (11) ◽  
pp. 3277-3296 ◽  
Author(s):  
James J. Benedict ◽  
David A. Randall
Keyword(s):  
Boundary Layer ◽  
General Circulation ◽  
Deep Convection ◽  
Circulation Model ◽  
Grid Cell ◽  
Atmospheric Model ◽  
Space Time ◽  
Madden Julian Oscillation ◽  
Moist Convection ◽  
Time Structures

Abstract The detailed dynamic and thermodynamic space–time structures of the Madden–Julian oscillation (MJO) as simulated by the superparameterized Community Atmosphere Model version 3.0 (SP-CAM) are analyzed. Superparameterization involves substituting conventional boundary layer, moist convection, and cloud parameterizations with a configuration of cloud-resolving models (CRMs) embedded in each general circulation model (GCM) grid cell. Unlike most GCMs that implement conventional parameterizations, the SP-CAM displays robust atmospheric variability on intraseasonal space and time (30–60 days) scales. The authors examine a 19-yr SP-CAM simulation based on the Atmospheric Model Intercomparison Project protocol, forced by prescribed sea surface temperatures. Overall, the space–time structures of MJO convective disturbances are very well represented in the SP-CAM. Compared to observations, the model produces a similar vertical progression of increased moisture, warmth, and heating from the boundary layer to the upper troposphere as deep convection matures. Additionally, important advective and convective processes in the SP-CAM compare favorably with those in observations. A deficiency of the SP-CAM is that simulated convective intensity organized on intraseasonal space–time scales is overestimated, particularly in the west Pacific. These simulated convective biases are likely due to several factors including unrealistic boundary layer interactions, a lack of weakening of the simulated disturbance over the Maritime Continent, and mean state differences.

scholarly journals Effects of Enhanced Front Walker Cell on the Eastward Propagation of the MJO

2018 ◽  
Vol 31 (19) ◽  
pp. 7719-7738 ◽  
Author(s):  
Guosen Chen ◽  
Bin Wang
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Middle Atmosphere ◽  
Deep Convection ◽  
Madden Julian Oscillation ◽  
Maritime Continent ◽  
Walker Cell ◽  
The Indian Ocean ◽  
Upper Level ◽  
The Western Pacific

Well-organized eastward propagation of the Madden–Julian oscillation (MJO) is found to be accompanied by the leading suppressed convection (LSC) over the Maritime Continent (MC) and the western Pacific (WP) when the MJO convection is in the Indian Ocean (IO). However, it remains unclear how the LSC influences the MJO and what causes the LSC. The present study shows that the LSC is a prevailing precursor for eastward propagation of the MJO across the MC. The LSC enhances the coupling of IO convection and the Walker cell to its east [front Walker cell (FWC)] by increasing the zonal heating gradient. The enhanced FWC strengthens the low-level easterly, which increases boundary layer (BL) convergence and promotes congestus convection to the east of the deep convection; the enhanced congestus convection preconditions the lower to middle atmosphere, which further promotes the transition from congestus to deep convection and leads to eastward propagation of the MJO. The MJO ceases eastward propagation once the FWC decouples from it. Further analysis reveals that LSC has two major origins: one comes from the eastward propagation of the preceding IO dry phase associated with the MJO, and the other develops concurrently with the IO convection. In the latter case, the development of the LSC is brought about by a two-way interaction between the MJO’s tropical heating and the associated tropical–extratropical teleconnection: the preceding IO suppressed convection induces a tropical–extratropical teleconnection, which evolves and forms an anomalous western North Pacific cyclone that generates upper-level convergence and induces significant LSC.

Role of delayed deep convection in the Madden-Julian oscillation

2015 ◽  
Vol 126 (1-2) ◽  
pp. 313-321 ◽  
Author(s):  
Fei Liu ◽  
Zaoyang Chen ◽  
Gang Huang
Keyword(s):  
Deep Convection ◽  
Madden Julian Oscillation

scholarly journals Separating Dynamic and Thermodynamic Impacts of Climate Change on Daytime Convective Development over Land

2019 ◽  
Vol 32 (16) ◽  
pp. 5213-5234 ◽  
Author(s):  
Wojciech W. Grabowski ◽  
Andreas F. Prein
Keyword(s):  
Climate Change ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Deep Convection ◽  
Convective Available Potential Energy ◽  
Future Research ◽  
Small Scale ◽  
Moist Convection ◽  
The Impact

AbstractClimate change affects the dynamics and thermodynamics of moist convection. Changes in the dynamics concern, for instance, an increase of convection strength due to increases of convective available potential energy (CAPE). Thermodynamics involve increases in water vapor that the warmer atmosphere can hold and convection can work with. Small-scale simulations are conducted to separate these two components for daytime development of unorganized convection over land. The simulations apply a novel modeling technique referred to as the piggybacking (or master–slave) approach and consider the global climate model (GCM)-predicted change of atmospheric temperature and moisture profiles in the Amazon region at the end of the century under a business-as-usual scenario. The simulations show that the dynamic impact dominates because changes in cloudiness and rainfall come from cloud dynamics considerations, such as the change in CAPE and convective inhibition (CIN) combined with the impact of environmental relative humidity (RH) on deep convection. The small RH reduction between the current and future climate significantly affects the mean surface rain accumulation as it changes from a small reduction to a small increase when the RH decrease is eliminated. The thermodynamic impact on cloudiness and precipitation is generally small, with the extreme rainfall intensifying much less than expected from an atmospheric moisture increase. These results are discussed in the context of previous studies concerning climate change–induced modifications of moist convection. Future research directions applying the piggybacking method are discussed.

scholarly journals Sensitivity Experiments on the Role of Water Vapor in the Eastward Propagation of MJO

2021 ◽  
Author(s):  
Xiaoyu Zhu ◽  
Zhong Zhong ◽  
Yimin Zhu ◽  
Yijia Hu ◽  
Yao Ha ◽  
...  
Keyword(s):  
Water Vapor ◽  
Zonal Wind ◽  
Climate Model ◽  
Regional Climate ◽  
Atmospheric Stability ◽  
Wrf Model ◽  
Low Frequency ◽  
Cumulus Parameterization ◽  
Sensitivity Experiments

Abstract In this study, we employed the nudging assimilation of the Weather Research and Forecasting (WRF) model to conduct a set of sensitivity experiments on the role of water vapor in the Madden-Julian Oscillation (MJO) eastward propagation, focusing on the eastward propagating 30-60d low-frequency component in the tropical atmosphere from the Indian Ocean to the western Pacific Ocean during September-November 2004. Using 11 different cumulus parameterization schemes, the simulation results show that the ability of the regional climate model in simulating the MJO eastward propagation is sensitive to the cumulus scheme: A suitable scheme can well reproduce the MJO eastward propagation characteristics, while most schemes show no skill for the MJO eastward propagation. When the water vapor in the model domain was assimilated using reanalysis data with nudging technique, we found that the low-frequency evolution of the tropical zonal wind exhibits MJO features well, and the low-frequency phase of water vapor is ahead of the zonal wind by about 6-7 days, which suggests that the atmospheric water-vapor distribution is the key factor for the eastward propagation of the MJO, and the effect of water-vapor field via affecting the atmospheric stability. When the atmospheric temperature assimilation was conducted, there was almost no improvement in the skill of MJO simulation.

scholarly journals Impacts of Idealized Air–Sea Coupling on Madden–Julian Oscillation Structure in the Superparameterized CAM

2011 ◽  
Vol 68 (9) ◽  
pp. 1990-2008 ◽  
Author(s):  
James J. Benedict ◽  
David A. Randall
Keyword(s):  
Deep Convection ◽  
Ocean Model ◽  
Surface Fluxes ◽  
Convective Heating ◽  
Madden Julian Oscillation ◽  
Kelvin Wave ◽  
Coupled Simulation ◽  
Wave Response ◽  
Community Atmosphere Model ◽  
Anomalous Surface

Abstract Air–sea interactions and their impact on intraseasonal convective organization are investigated by comparing two 5-yr simulations from the superparameterized Community Atmosphere Model version 3.0 (SP-CAM). The first is forced using prescribed sea surface temperatures (SSTs). The second is identical except that a simplified oceanic mixed-layer model is used to predict tropical SST anomalies that are coupled to the atmosphere. This partially coupled simulation allows SSTs to respond to anomalous surface fluxes. Implementation of the idealized slab ocean model in the SP-CAM results in significant changes to intraseasonal convective variability and organization. The more realistic treatment of air–sea interactions in the coupled simulation improves many aspects of tropical convection on intraseasonal scales, from the relationships between precipitation and SSTs to the space–time structure and propagation of the Madden–Julian oscillation (MJO). This improvement is associated with a more realistic convergence structure and longitudinal gradient of SST relative to MJO deep convection. In the uncoupled SP-CAM, SST is roughly in phase with the MJO convective center and the development of the Kelvin wave response and boundary layer convergence east of the convective center is relatively weak. In the coupled SP-CAM, maxima in SST lead maxima in MJO convection by cycle. Coupling produces warmer SSTs, a stronger Kelvin wave response, enhanced low-level convergence, and increased convective heating ahead (east) of the MJO convective center. Convective development east of the MJO precipitation center is more favorable in the coupled versus the uncoupled version, resulting in more realistic organization and clearer eastward propagation of the MJO in the coupled SP-CAM.

scholarly journals Future Changes in the Brewer–Dobson Circulation under Different Greenhouse Gas Concentrations in WACCM4

2014 ◽  
Vol 71 (8) ◽  
pp. 2962-2975 ◽  
Author(s):  
Froila M. Palmeiro ◽  
Natalia Calvo ◽  
Rolando R. Garcia
Keyword(s):  
Climate Change ◽  
Climate Model ◽  
Wave Spectrum ◽  
Ocean Model ◽  
Climate Change Scenarios ◽  
Planetary Scale ◽  
Upward Displacement ◽  
Control Principle

Abstract The climatology and future changes of the Brewer–Dobson circulation (BDC) in three climate change scenarios are studied using the latest version of the Whole Atmosphere Community Climate Model (WACCM4), which is fully coupled to an ocean model. The results show an acceleration in both the shallow and deep branches of circulation in response to increasing greenhouse gases (GHGs) together with an upward displacement of the tropical upwelling in the deep branch near the stratopause. The downward control principle reveals that different waves are involved in forcing the acceleration of the upper and lower branches. Climatological-mean tropical upwelling in both the lower and upper stratosphere is dominated by explicitly resolved, planetary-scale waves. Trends in the tropical upwelling in the lower stratosphere are mainly attributed to explicitly resolved, planetary-scale waves. However, in the upper stratosphere, despite the fact that resolved waves control the forcing of the climatological upwelling, their contribution to the long-term trend diminishes with increasing GHGs, while the role of gravity waves associated with fronts increases and becomes dominant in the model scenario with the largest GHG increases. The intensification and upward displacement of the subtropical tropospheric jets due to climate change leads to filtering of the westerly part of the frontal gravity wave spectrum, leaving the easterly components to reach the upper stratosphere and force the changes in the circulation there.

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