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 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 Comparison of Moist Static Energy and Budget between the GCM-Simulated Madden–Julian Oscillation and Observations over the Indian Ocean and Western Pacific

2013 ◽  
Vol 26 (14) ◽  
pp. 4981-4993 ◽  
Author(s):  
Xiaoqing Wu ◽  
Liping Deng
Keyword(s):  
Indian Ocean ◽  
General Circulation ◽  
Western Pacific ◽  
Striking Difference ◽  
Madden Julian Oscillation ◽  
Moist Static Energy ◽  
Horizontal Advection ◽  
Budget Analysis ◽  
The Indian Ocean ◽  
Static Energy

Abstract The moist static energy (MSE) anomalies and MSE budget associated with the Madden–Julian oscillation (MJO) simulated in the Iowa State University General Circulation Model (ISUGCM) over the Indian and Pacific Oceans are compared with observations. Different phase relationships between MJO 850-hPa zonal wind, precipitation, and surface latent heat flux are simulated over the Indian Ocean and western Pacific, which are greatly influenced by the convection closure, trigger conditions, and convective momentum transport (CMT). The moist static energy builds up from the lower troposphere 15–20 days before the peak of MJO precipitation, and reaches the maximum in the middle troposphere (500–600 hPa) near the peak of MJO precipitation. The gradual lower-tropospheric heating and moistening and the upward transport of moist static energy are important aspects of MJO events, which are documented in observational studies but poorly simulated in most GCMs. The trigger conditions for deep convection, obtained from the year-long cloud-resolving model (CRM) simulations, contribute to the striking difference between ISUGCM simulations with the original and modified convection schemes and play the major role in the improved MJO simulation in ISUGCM. Additionally, the budget analysis with the ISUGCM simulations shows the increase in MJO MSE is in phase with the horizontal advection of MSE over the western Pacific, while out of phase with the horizontal advection of MSE over the Indian Ocean. However, the NCEP analysis shows that the tendency of MJO MSE is in phase with the horizontal advection of MSE over both oceans.

scholarly journals Evolution of the Distribution of Upper-Tropospheric Humidity over the Indian Ocean: Connection with Large-Scale Advection and Local Cloudiness

2017 ◽  
Vol 56 (7) ◽  
pp. 2035-2052 ◽  
Author(s):  
Thomas Garot ◽  
Hélène Brogniez ◽  
Renaud Fallourd ◽  
Nicolas Viltard
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Transport Model ◽  
Intraseasonal Variability ◽  
Back Trajectory ◽  
Time Step ◽  
Air Masses ◽  
Upper Troposphere ◽  
Upper Tropospheric Humidity ◽  
The Indian Ocean

AbstractThe spatial and temporal distribution of upper-tropospheric humidity (UTH) observed by the Sounder for Atmospheric Profiling of Humidity in the Intertropics by Radiometry (SAPHIR)/Megha-Tropiques radiometer is analyzed over two subregions of the Indian Ocean during October–December over 2011–14. The properties of the distribution of UTH were studied with regard to the phase of the Madden–Julian oscillation (active or suppressed) and large-scale advection versus local production of moisture. To address these topics, first, a Lagrangian back-trajectory transport model was used to assess the role of the large-scale transport of air masses in the intraseasonal variability of UTH. Second, the temporal evolution of the distribution of UTH is analyzed using the computation of the higher moments of its probability distribution function (PDF) defined for each time step over the domain. The results highlight significant differences in the PDF of UTH depending on the phase of the MJO. The modeled trajectories ending in the considered domain originate from an area that strongly varies depending on the phases of the MJO: during the active phases, the air masses are spatially constrained within the tropical Indian Ocean domain, whereas a distinct upper-tropospheric (200–150 hPa) westerly flow guides the intraseasonal variability of UTH during the suppressed phases. Statistical relationships between the cloud fractions and the UTH PDF moments of are found to be very similar regardless of the convective activity. However, the occurrence of thin cirrus clouds is associated with a drying of the upper troposphere (enhanced during suppressed phases), whereas the occurrence of thick cirrus anvil clouds appears to be significantly related to a moistening of the upper troposphere.

scholarly journals BIOLOGI REPRODUKSI TUNA MATA BESAR (Thunnus obesus) YANG TERTANGKAP DI SAMUDERA HINDIA

2017 ◽  
Vol 3 (2) ◽  
pp. 129
Author(s):  
Ria Faizah ◽  
Budi Iskandar Prisantoso
Keyword(s):  
Indian Ocean ◽  
Gonad Development ◽  
Morphological Structure ◽  
Maturity Stage ◽  
Batch Fecundity ◽  
Gonad Maturity ◽  
Thunnus Obesus ◽  
The Indian Ocean ◽  
Index Value ◽  
Somatic Index

Tujuan penelitian ini adalah untuk mendapatkan informasi mengenai aspek reproduksi ikan tuna mata besar (Thunnus obesus) di perairan Samudera Hindia. Sebanyak 42 contoh gonad dari ikan tuna mata besar yang tertangkap perairan Samudera Hindia antara bulan Maret sampai Oktober 2008 digunakan dalam penelitian ini. Pengamatan meliputi struktur morfologi gonad ikan, perkembangan gonad, diameter telur, dan fekunditas. Hasil penelitian ini menunjukan bahwa ikantuna mata besar yang tertangkap memiliki tingkat kematangan gonad I, II, dan IV. Nilai gonado somatic index rata-rata tuna mata besar semakin meningkat seiring dengan meningkatnya tingkat kematangan gonad. Musim pemijahan untuk tuna mata besar diduga terjadi pada bulan Oktober. Tuna mata besarmemiliki fekunditas antara 8.163.715-10.365.317 butir dan memiliki pola pemijahan berganda. The objective of this research is to study the reproductive biology of big eye tuna (Thunnus obesus) from Indian Ocean. A numbers of 42 gonad samples were taken from fresh individuals captured in the Indian Ocean during period of March until October 2008. The observation comprised of morphological structure of gonad, gonad development, oocytes diameter, and batch fecundity. The results showed that the gonad maturity stages of big eye tuna were ranged from immature (the gonad maturity stage of I and II) to mature (the gonad maturity stage of IV), and the gonado somatic index value increase along with increase of gonad maturity. Spawning season for big eye tuna estimated was in October, range of fecundity were 8.163.715-10.365.317 oocytes, and the spawning type waspartial spawned.

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 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.

Distinctive Roles of Air–Sea Coupling on Different MJO Events: A New Perspective Revealed from the DYNAMO/CINDY Field Campaign*

2015 ◽  
Vol 143 (3) ◽  
pp. 794-812 ◽  
Author(s):  
Xiouhua Fu ◽  
Wanqiu Wang ◽  
June-Yi Lee ◽  
Bin Wang ◽  
Kazuyoshi Kikuchi ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Essential Role ◽  
Intraseasonal Variability ◽  
Physical Processes ◽  
Field Campaign ◽  
Strongly Coupled ◽  
The Indian Ocean ◽  
New Perspective ◽  
Sst Anomalies

Abstract Previous observational analysis and modeling studies indicate that air–sea coupling plays an essential role in improving MJO simulations and extending MJO forecasting skills. However, whether the SST feedback plays an indispensable role for the existence of the MJO remains controversial, and the precise physical processes through which the SST feedback may lead to better MJO simulations and forecasts remain elusive. The DYNAMO/Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY) field campaign recently completed over the Indian Ocean reveals a new perspective and provides better data to improve understanding of the MJO. It is found that among the five MJO events that occurred during the DYNAMO/CINDY field campaign, only two MJO events (the November and March ones) have robust SST anomalies associated with them. For the other three MJO events (the October, December, and January ones), no coherent SST anomalies are observed. This observational scenario suggests that the roles of air–sea coupling on the MJO vary greatly from event to event. To elucidate the varying roles of air–sea coupling on different MJO events, a suite of hindcast experiments was conducted with a particular focus on the October and November MJO events. The numerical results confirm that the October MJO is largely controlled by atmospheric internal dynamics, while the November MJO is strongly coupled with underlying ocean. For the November MJO event, the positive SST anomalies significantly improve MJO forecasting by enhancing the response of a Kelvin–Rossby wave couplet, which prolongs the feedback between convection and large-scale circulations, and thus favors the development of stratiform rainfall, in turn, facilitating the production of eddy available potential energy and significantly amplifying the intensity of the model November MJO.

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.

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