scholarly journals Simulation of the Madden–Julian Oscillation in the NCAR CCM3 Using a Revised Zhang–McFarlane Convection Parameterization Scheme

2005 ◽  
Vol 18 (19) ◽  
pp. 4046-4064 ◽  
Author(s):  
Guang J. Zhang ◽  
Mingquan Mu
Keyword(s):  
Relative Humidity ◽  
Indian Ocean ◽  
Zonal Wind ◽  
Lower Troposphere ◽  
Parameterization Scheme ◽  
Madden Julian Oscillation ◽  
Shallow Convection ◽  
Time Period ◽  
The Indian Ocean ◽  
Convection Parameterization

Abstract This study presents the simulation of the Madden–Julian oscillation (MJO) in the NCAR CCM3 using a modified Zhang–McFarlane convection parameterization scheme. It is shown that, with the modified scheme, the intraseasonal (20–80 day) variability in precipitation, zonal wind, and outgoing longwave radiation (OLR) is enhanced substantially compared to the standard CCM3 simulation. Using a composite technique based on the empirical orthogonal function (EOF) analysis, the paper demonstrates that the simulated MJOs are in better agreement with the observations than the standard model in many important aspects. The amplitudes of the MJOs in 850-mb zonal wind, precipitation, and OLR are comparable to those of the observations, and the MJOs show clearly eastward propagation from the Indian Ocean to the Pacific. In contrast, the simulated MJOs in the standard CCM3 simulation are weak and have a tendency to propagate westward in the Indian Ocean. Nevertheless, there remain several deficiencies that are yet to be addressed. The time period of the MJOs is shorter, about 30 days, compared to the observed time period of 40 days. The spatial scale of the precipitation signal is smaller than observed. Examination of convective heating from both deep and shallow convection and its relationship with moisture anomalies indicates that near the mature phase of the MJO, regions of shallow convection developing ahead of the deep convection coincide with regions of positive moisture anomalies in the lower troposphere. This is consistent with the recent observations and theoretical development that shallow convection helps to precondition the atmosphere for MJO by moistening the lower troposphere. Sensitivity tests are performed on the individual changes in the modified convection scheme. They show that both change of closure and use of a relative humidity threshold for the convection trigger play important roles in improving the MJO simulation. Use of the new closure leads to the eastward propagation of the MJO and increases the intensity of the MJO signal in the wind field, while imposing a relative humidity threshold enhances the MJO variability in precipitation.

scholarly journals The Relationship between the ITCZ and MJO Initiation over the Indian Ocean

2019 ◽  
Vol 76 (8) ◽  
pp. 2275-2294 ◽  
Author(s):  
Rachel C. Zelinsky ◽  
Chidong Zhang ◽  
Chuntao Liu
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Madden Julian Oscillation ◽  
Shallow Convection ◽  
Theoretical Understanding ◽  
Convective Initiation ◽  
Moist Condition ◽  
The Indian Ocean ◽  
The Relationship ◽  
Global Reanalysis

Abstract Understanding convective initiation of the Madden–Julian oscillation (MJO) remains an unmet challenge. MJO initiation has been perceived as a process starting from a convectively suppressed large-scale condition with gradual growth of shallow convection to congestus and to deep convective and stratiform systems that cover a large-scale area. During the DYNAMO field campaign over the Indian Ocean, MJO initiation was observed to start from an existing intertropical convergence zone (ITCZ) south of the equator. This raises a question of what possible role the ITCZ may play in convective initiation of the MJO. This study addresses this question through analysis of satellite observations of precipitation and a global reanalysis product. By setting several criteria, MJO and ITCZ events were objectively identified and grouped according to whether MJO initiation was immediately preceded by an ITCZ. The results demonstrate that an ITCZ is neither a necessary nor sufficient condition for convective initiation of the MJO. Nonetheless, evolution of the large-scale circulation, moisture, and convective characteristics during MJO initiation can be different with and without a preexisting ITCZ. Convective growth begins gradually before and during MJO initiation when there is a preexisting ITCZ whereas it is abrupt and slightly delayed without a preexisting ITCZ. Such differences are presumably related to the existing large-scale moist condition of the ITCZ. The results from this study suggest that there are multiple mechanisms for convective initiation of the MJO, which should be considered in theoretical understanding of the MJO.

scholarly journals Objective Diagnostics and the Madden–Julian Oscillation. Part I: Methodology

2015 ◽  
Vol 28 (10) ◽  
pp. 4127-4140 ◽  
Author(s):  
Brandon O. Wolding ◽  
Eric D. Maloney
Keyword(s):  
Indian Ocean ◽  
Zonal Wind ◽  
Intraseasonal Variability ◽  
Geographical Location ◽  
Madden Julian Oscillation ◽  
Geographical Regions ◽  
The Indian Ocean ◽  
Upper Level ◽  
Static Energy ◽  
Index Value

Abstract Diagnostics obtained as an extension of empirical orthogonal function (EOF) analysis are shown to address many disadvantages of using EOF-based indices to assess the state of the Madden–Julian oscillation (MJO). The real-time multivariate MJO (RMM) index and the filtered MJO OLR (FMO) index are used to demonstrate these diagnostics. General characteristics of the indices, such as the geographical regions that most heavily influence each index, are assessed using the diagnostics. The diagnostics also identify how a given field, at various geographical locations, influences the index value at a given time. Termination (as defined by the RMM index) of the October 2011 MJO event that occurred during the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY) Dynamics of the MJO (DYNAMO) field campaign is shown to have resulted from changes in zonal wind anomalies at 200 hPa over the eastern Pacific Ocean, despite the onset of enhanced convection in the Indian Ocean and the persistence of favorable lower- and upper-level zonal wind anomalies near this region. The diagnostics objectively identify, for each specific geographical location, the index phase where the largest MJO-related anomalies in a given field are likely to be observed. This allows for the geographical variability of anomalous conditions associated with the MJO to be easily assessed throughout its life cycle. In Part II of this study, unique physical insight into the moist static energy and moisture budgets of the MJO is obtained from the application of diagnostics introduced here.

scholarly journals Analysis of Real GDP, Imports and Exports of Indian Ocean RIM Association Member Nations

2021 ◽  
Vol 58 (2) ◽  
pp. 68-100
Author(s):  
Manbir Singh, Dr. Jasdeep Kaur Dhami
Keyword(s):  
South Africa ◽  
Sri Lanka ◽  
Indian Ocean ◽  
Regional Cooperation ◽  
Islamic Republic ◽  
Association Member ◽  
Real Gdp ◽  
Time Period ◽  
The Indian Ocean

The Indian Ocean woven together by transmission of trade, commands the control of majority of the world’s cargo ships, one third of the worlds cargo traffic and two thirds of total world’s oil shipments. The main aim of this paper is to analyse Real GDP, Imports and Exports of Indian Ocean RIM Association Member Nations. Time period of the study is from 1980 to 2019.  Indian Ocean Rim Association for Regional Cooperation (IOR-ARC) contributes 11.7 per cent share in world exports, in case of member nations highest share is of Singapore 2.1 per cent  followed by India and UAE 1.7 per cent, Australia 1.5 per cent, Thailand and Malaysia 1.3 per cent. Indonesia, South Africa, Bangladesh, Oman, Iran, Islamic Republic of, Sri Lanka the share in world exports is less than 1 per cent.  

Influence of the Madden-Julian Oscillation on sea surface salinity in the Indian Ocean

2011 ◽  
Vol 38 (17) ◽  
pp. n/a-n/a ◽  
Author(s):  
Gary Grunseich ◽  
Bulusu Subrahmanyam ◽  
Anthony Arguez
Keyword(s):  
Indian Ocean ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Madden Julian Oscillation ◽  
Surface Salinity ◽  
The Indian Ocean

scholarly journals Parameter Modulation of Madden-Julian Oscillation Behaviors in BCC_CSM1.2: The Key Role of Moisture-Shallow Convection Feedback

Atmosphere ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 241 ◽  
Author(s):  
Kai Huang ◽  
Hong-Li Ren ◽  
Xiangwen Liu ◽  
Pengfei Ren ◽  
Yuntao Wei ◽  
...  
Keyword(s):  
Lower Troposphere ◽  
Latin Hypercube Sampling ◽  
Heavy Precipitation ◽  
Convective Precipitation ◽  
Physical Parameters ◽  
Madden Julian Oscillation ◽  
Shallow Convection ◽  
Climate System Model ◽  
New Strategy

To reveal key parameter-related physical mechanisms in simulating Madden-Julian Oscillation (MJO), seven physical parameters in the convection and cloud parameterization schemes of Beijing Climate Center Climate System Model (BCC_CSM1.2) are perturbed with Latin hypercube sampling method. A new strategy is proposed to select runs with good and poor MJO simulations among 85 generated ones. Outputs and parameter values from good and poor simulations are composited separately for comparison. Among the seven chosen parameters, a decreased value of precipitation efficiency for shallow convection, higher values of relative humidity threshold for low stable clouds and evaporation efficiency for deep convective precipitation are crucial to simulate a better MJO. Changes of the three parameters act together to suppress heavy precipitation and increase the frequency of light rainfall over the Indo-Pacific region, supplying more moisture in low and middle troposphere. As a result of a wetter lower troposphere ahead of the MJO main convection, the low-level moisture preconditioning along with the leading shallow convection tends to be enhanced, favorable for MJO’s further development and eastward propagation. The MJO’s further propagation across the Maritime Continent (MC) in good simulations is accompanied with more land precipitation dominated by shallow convection. Therefore, the above-mentioned three parameters are found to be crucial parameters out of the seven ones for MJO simulation, providing an inspiration for better MJO simulation and prediction with this model. This work is valuable as it highlights the key role of moisture-shallow convection feedback in the MJO dynamics.

scholarly journals Impact of the Madden–Julian Oscillation on Summer Rainfall in Southeast China

2009 ◽  
Vol 22 (2) ◽  
pp. 201-216 ◽  
Author(s):  
Lina Zhang ◽  
Bizheng Wang ◽  
Qingcun Zeng
Keyword(s):  
Indian Ocean ◽  
Tropical Indian Ocean ◽  
Summer Rainfall ◽  
Western Pacific ◽  
Madden Julian Oscillation ◽  
Energy Propagation ◽  
Southeast China ◽  
The Indian Ocean ◽  
The Impact ◽  
The Western Pacific

Abstract The impact of the Madden–Julian oscillation (MJO) on summer rainfall in Southeast China is investigated using the Real-time Multivariate MJO (RMM) index and the observational rainfall data. A marked transition of rainfall patterns from being enhanced to being suppressed is found in Southeast China (east of 105°E and south of 35°N) on intraseasonal time scales as the MJO convective center moves from the Indian Ocean to the western Pacific Ocean. The maximum positive and negative anomalies of regional mean rainfall are in excess of 10% relative to the climatological regional mean. Such different rainfall regimes are associated with the corresponding changes in physical fields such as the western Pacific subtropical high (WPSH), moisture, and vertical motions. When the MJO is mainly over the Indian Ocean, the WPSH shifts farther westward, and the moisture and upward motions in Southeast China are increased. In contrast, when the MJO enters the western Pacific, the WPSH retreats eastward, and the moisture and upward motions in Southeast China are decreased. It is suggested that the MJO may influence summer rainfall in Southeast China through remote and local dynamical mechanisms, which correspond to the rainfall enhancement and suppression, respectively. The remote role is the energy propagation of the Rossby wave forced by the MJO-related heating over the Indian Ocean through the low-level westerly waveguide from the tropical Indian Ocean to Southeast China. The local role is the northward shift of the upward branch of the anomalous meridional circulation when the MJO is over the western Pacific, which causes eastward retreat of the WPSH and suppressed moisture transport toward Southeast China.

scholarly journals Kinematic and Precipitation Characteristics of Convective Systems Observed by Airborne Doppler Radar during the Life Cycle of a Madden–Julian Oscillation in the Indian Ocean

2014 ◽  
Vol 142 (4) ◽  
pp. 1385-1402 ◽  
Author(s):  
Nick Guy ◽  
David P. Jorgensen
Keyword(s):  
Indian Ocean ◽  
Doppler Radar ◽  
Convective System ◽  
Dynamical Structure ◽  
Madden Julian Oscillation ◽  
Tropical Ocean ◽  
Convective Systems ◽  
Toga Coare ◽  
Stratiform Precipitation ◽  
The Indian Ocean

Abstract This study presents characteristics of convective systems observed during the Dynamics of the Madden–Julian oscillation (DYNAMO) experiment by the instrumented NOAA WP-3D aircraft. Nine separate missions, with a focus on observing mesoscale convective systems (MCSs), were executed to obtain data in the active and inactive phase of a Madden–Julian oscillation (MJO) in the Indian Ocean. Doppler radar and in situ thermodynamic data are used to contrast the convective system characteristics during the evolution of the MJO. Isolated convection was prominent during the inactive phases of the MJO, with deepening convection during the onset of the MJO. During the MJO peak, convection and stratiform precipitation became more widespread. A larger population of deep convective elements led to a larger area of stratiform precipitation. As the MJO decayed, convective system top heights increased, though the number of convective systems decreased, eventually transitioning back to isolated convection. A distinct shift of echo top heights and contoured frequency-by-altitude diagram distributions of radar reflectivity and vertical wind speed indicated that some mesoscale characteristics were coupled to the MJO phase. Convective characteristics in the climatological initiation region (Indian Ocean) were also apparent. Comparison to results from the Tropical Ocean and Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) in the western Pacific indicated that DYNAMO MCSs were linearly organized more parallel to the low-level shear and without strong cold pools than in TOGA COARE. Three-dimensional MCS airflow also showed a different dynamical structure, with a lack of the descending rear inflow present in shear perpendicularly organized TOGA COARE MCSs. Weaker, but deeper updrafts were observed in DYNAMO.

A Modified Multivariate Madden–Julian Oscillation Index Using Velocity Potential

2013 ◽  
Vol 141 (12) ◽  
pp. 4197-4210 ◽  
Author(s):  
Michael J. Ventrice ◽  
Matthew C. Wheeler ◽  
Harry H. Hendon ◽  
Carl J. Schreck ◽  
Chris D. Thorncroft ◽  
...  
Keyword(s):  
Zonal Wind ◽  
Velocity Potential ◽  
Longwave Radiation ◽  
Warm Pool ◽  
Boreal Summer ◽  
Madden Julian Oscillation ◽  
Systematic Analysis ◽  
Planetary Scale ◽  
Daily Data ◽  
The Indian Ocean

Abstract A new Madden–Julian oscillation (MJO) index is developed from a combined empirical orthogonal function (EOF) analysis of meridionally averaged 200-hPa velocity potential (VP200), 200-hPa zonal wind (U200), and 850-hPa zonal wind (U850). Like the Wheeler–Hendon Real-time Multivariate MJO (RMM) index, which was developed in the same way except using outgoing longwave radiation (OLR) data instead of VP200, daily data are projected onto the leading pair of EOFs to produce the two-component index. This new index is called the velocity potential MJO (VPM) indices and its properties are quantitatively compared to RMM. Compared to the RMM index, the VPM index detects larger-amplitude MJO-associated signals during boreal summer. This includes a slightly stronger and more coherent modulation of Atlantic tropical cyclones. This result is attributed to the fact that velocity potential preferentially emphasizes the planetary-scale aspects of the divergent circulation, thereby spreading the convectively driven component of the MJO’s signal across the entire globe. VP200 thus deemphasizes the convective signal of the MJO over the Indian Ocean warm pool, where the OLR variability associated with the MJO is concentrated, and enhances the signal over the relatively drier longitudes of the equatorial Pacific and Atlantic. This work provides a useful framework for systematic analysis of the strengths and weaknesses of different MJO indices.

Precursor Environmental Conditions Associated with the Termination of Madden–Julian Oscillation Events

2015 ◽  
Vol 72 (5) ◽  
pp. 1908-1931 ◽  
Author(s):  
Justin P. Stachnik ◽  
Duane E. Waliser ◽  
Andrew J. Majda
Keyword(s):  
Indian Ocean ◽  
Environmental Conditions ◽  
Warm Pool ◽  
Western Pacific ◽  
Specific Humidity ◽  
Advection Equation ◽  
Local Domain ◽  
Madden Julian Oscillation ◽  
Budget Analysis ◽  
The Indian Ocean

Abstract This study presents an analysis of the precursor environmental conditions related to the termination of Madden–Julian oscillation (MJO) events. A simple climatology is created using a real-time MJO monitoring index, documenting the locations and frequencies of MJO decay. Lead–lag composites of several atmospheric variables including temperature, moisture, and intraseasonal wind anomalies are generated from three reanalyses. There is remarkable agreement among the datasets with long-term, lower-tropospheric moisture deficits over the local domain best identifying termination events over the Indian Ocean. MJO termination in the Indian Ocean is also linked to a northward shift of the intertropical convergence zone (ITCZ) with possible lead times as much as 20 days prior to MJO decay. Statistically significant differences in the low-level vertical velocity and specific humidity are also identified more than 10 days in advance of MJO termination events in the western Pacific, though the differences here are more symmetric about the equator. Unlike the Indian Ocean and western Pacific, MJOs that terminate over the Maritime Continent appear to be related to their own intensity rather than the downstream conditions. As such, only the strongest MJOs tend to propagate into the warm pool region. Finally, a budget analysis is performed on the three-dimensional moisture advection equation in order to better elucidate what time scales and physical mechanisms are most important for MJO termination. The combination of intraseasonal vertical circulation anomalies coupled with the mean-state specific humidity best explain the anomalous moisture patterns associated with MJO termination, suggesting that the downstream influence of the MJO circulation can eventually lead to its future demise.

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