Impact of intraseasonal oscillation on the tropical cyclone track in the South China Sea
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Outgoing longwave radiation
Anomaly (physics)
Madden–Julian oscillation
The basic structural features of the Madden-Julian oscillation (MJO) in the lower and upper troposphere of the tropical zone are demonstrated. The problems associated with determining the main mechanisms of its formation are identified. Various approaches to the MJO quantification are considered. Using 850 and 200 hPa zonal wind speed from the ERA5 reanalysis datasets, as well as NCEP/NOAA satellite-derived data on outgoing longwave radiation, the main disadvantages and advantages are shown for one of the possible quantitative criteria of the MJO (RMM index). The results of the study are supposed to be operationally used in the NEACC’s subseasonal meteorological forecasts. Keywords: Madden-Julian Oscillation, RMM index, subseasonal foresact
Madden–Julian oscillation
Outgoing longwave radiation
Oscillation (cell signaling)
Longwave
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[1] Using satellite measurements of Outgoing Longwave Radiation (OLR) and Simple Ocean Data Assimilation (SODA) reanalysis, the Madden-Julian Oscillation (MJO) influence on Sea Surface Salinity (SSS) across the Indian Ocean is examined. The SSS pattern during different stages of the MJO propagation across the Indian Ocean are analyzed conditioned on season and phase of the El Niño – Southern Oscillation. The processes through which the SSS patterns develop depend upon anomalous atmospheric conditions and oceanic processes during the different stages of the MJO. The combinations of anomalous conditions during each stage of the MJO with seasonal and long-term climate variations create different responses in SSS. The SSS variability during the MJO may produce numerous indirect feedbacks, which are the result of SSS altering the depth of the Barrier Layer (BL) and mixed layer. Satellite salinity measurements will enhance our knowledge of the SSS variability during different stages of the MJO propagation.
Madden–Julian oscillation
Outgoing longwave radiation
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Mixed layer
Oscillation (cell signaling)
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Madden–Julian oscillation
Outgoing longwave radiation
Teleconnection
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The Madden-Julian oscillation (MJO) significantly impacts North Atlantic hurricanes, with more hurricane activity occurring when the MJO favors enhanced convection over Africa and the tropical Indian Ocean and suppressed hurricane activity occurring when the MJO favors enhanced convection over the tropical Pacific. Using data from 1905-2015, we find more hurricanes make landfall in the continental US when the MJO enhances convection over the tropical Indian Ocean. In addition, when the MJO enhances convection over the Western Hemisphere, tropical cyclones tend to form in the Gulf of Mexico or the Caribbean, leading to more Gulf Coast landfalls. As the MJO moves to the Indian Ocean, more storms form in the tropical Atlantic, increasing the number of Florida and East Coast landfalls. The MJO’s modulation of tropical cyclone steering winds appears to be secondary to its effects on genesis locations.
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Landfall
Atlantic hurricane
Tropical cyclone scales
Tropical cyclogenesis
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Abstract Centered composite analysis is described and applied to gain a better understanding of the initial phases of the Madden–Julian oscillation (MJO). Centered composite analysis identifies the dates and central locations of key events. The elements of the composite means are centered on these central locations before averages are calculated. In this way much of the spatial fuzziness, which is inherent in traditional composite analysis, is removed. The results for the MJO, based on MJO-filtered outgoing longwave radiation for the reference data and 40-yr ECMWF Re-Analysis (ERA-40) and NCEP–NCAR reanalysis products for the composites, show highly significant composites of unfiltered data for not only zero lag, but also lags back to 20 days before the target events. These composites identify propagating patterns of surface pressure, upper- and lower-troposphere zonal winds, surface temperature, and 850-hPa specific humidity associated with MJO convective events in the Indian Ocean. The propagation characteristics of important features, especially surface pressure, differ substantially for MJO convective anomalies centered over the Indian or western Pacific Oceans. This suggests that distinctly different mechanisms may be dominant in these two regions, and that many earlier analyses may be mixing properties of the two.
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The main objective of this study is to diagnose the relationship between the Madden-Julian Oscillation (MJO) and rainfall over East Africa. The data used include daily rainfall obtained from the National Meteorological and Hydrological Services (NMHSs) of Uganda, Tanzania and Kenya, daily Madden-Julian (MJO) indices from the Bureau of Meteorology Research Center (BMRC), daily Outgoing Longwave Radiation (OLR) from Climate Diagnostics Center (CDC) and wind data obtained from NCEP-NCAR.. Correlation and composite analyses are used to establish the association and the relationship between the MJO and rainfall over East Africa. The skill of forecast is verified using cross validation method. Results reveal strong association between East African rainfall and the MJO to the west of the region especially around the Lake Victoria. Out of phase (opposite) relationship between the west and the east is also revealed indicating different rain causing mechanisms for the two regions. The rainfall is also shown to depend on the configuration of the winds at low and upper levels. Based on composite analysis extreme rainfall events are shown to occur during preferential phases of the MJO. Phase 2 coincides with enhanced rainfall, high negative anomaly OLR values as well as westerly and easterly winds configuration at 700hpa and 200hpa while phase 5 and 6 are associated with depressed rainfall. The study also reveals that skillful prediction of rainfall at intraseasonal time scale is possible up to 10 days. The eastern parts of East Africa showed no prediction skills at intraseasonal time scales. The study provides evidence of the potential predictability of intraseasonal rainfall over East Africa using the MJO indices up to 10 days. However, the MJO indices only explain 18% of the variance over the Lake Victoria basin. The inclusion of other modes of variability such as Sea surface Temperatures (SSTs) and the Indian Ocean Dipole (IOD), as predictors are recommended in predicting intraseasonal rainfall. zonal wind anomalies at 850hPa and 200hPa levels. The method yields a pair of leading eigenvectors, EOF1 and EOF2 or principal components, which describes the eastward propagation of convective anomalies, associated with the MJO. The principal components time series are referred to as the Real Time Multivariate MJO indices (RMM). The MJO is also characterized by phases (Fig1), which determines the position of the convection in the tropics and the amplitude (Equation 1). Phase1 occurs when maximum convection is over West Africa; phases 2 and 3 are the times the maximum convection occurs over Indian Ocean while phases 6 and 7 occur when maximum convection is located over the Pacific Ocean (Wheeler and Hendon, 2004). Anyamba, (1990), Okoola and Camberlin (2003) associated the extreme rainfall events that occur over East Africa at intraseasonal time scales with the MJO. Pohl and Camberlin (2006) attributed the interannual variability in March-May rainfall over East Africa to fluctuations in the amplitude of the MJO. This study examines the relationship between East African rainfall and the MaddenJulian Oscillation (MJO) with the aim of predicting extreme rainfall events and dry spells that occur at intrasesaonal time scales for planning within the seasons and reduction of negative impacts associated with the events
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A reliable prognosis of extreme precipitation events in the tropics is arguably challenging to obtain due to the interaction of meteorological systems at various time scales. A pivotal component of the global climate variability is the so-called intraseasonal oscillations, phenomena that occur between 20 and 100 days. The Madden–Julian Oscillation (MJO), which is directly related to the modulation of convective precipitation in the equatorial belt, is considered the primary oscillation in the tropical region. The aim of this study is to diagnose the connection between the MJO signal and the regional intraseasonal rainfall variability over tropical Brazil. This is achieved through the development of an index called Multivariate Intraseasonal Index for Tropical Brazil (MITB). This index is based on Maximum Covariance Analysis (MCA) applied to the filtered daily anomalies of rainfall data over tropical Brazil against a group of covariates consisting of: outgoing longwave radiation and the zonal component u of the wind at 850 and 200 hPa. The first two MCA modes, which were used to create the $${ MITB}_1$$ and $${ MITB}_2$$ indices, represent 65 and 16 % of the explained variance, respectively. The combined multivariate index was able to satisfactorily represent the pattern of intraseasonal variability over tropical Brazil, showing that there are periods of activation and inhibition of precipitation connected with the pattern of MJO propagation. The MITB index could potentially be used as a diagnostic tool for intraseasonal forecasting.
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Abstract Analysis of daily observations shows that wintertime (November–April) precipitation over Southwest Asia is modulated by Madden–Julian oscillation (MJO) activity in the eastern Indian Ocean, with strength comparable to the interannual variability. Daily outgoing longwave radiation (OLR) for 1979–2001 is used to provide a long and consistent, but indirect, estimate of precipitation, and daily records from 13 stations in Afghanistan reporting at least 50% of the time for 1979–85 are used to provide direct, but shorter and irregularly reported, precipitation data. In the station data, for the average of all available stations, there is a 23% increase in daily precipitation relative to the mean when the phase of the MJO is negative (suppressed tropical convection in the eastern Indian Ocean), and a corresponding decrease when the MJO is positive. The distribution of extremes is also affected such that the 10 wettest days all occur during the negative MJO phase. The longer record of OLR data indicates that the effect of the MJO is quite consistent from year to year, with the anomalies averaged over Southwest Asia more negative (indicating more rain) for the negative phase of the MJO for each of the 22 yr in the record. Additionally, in 9 of the 22 yr the average influence of the MJO is larger than the interannual variability (e.g., the relationship results in anomalously wet periods even in dry years and vice versa). Examination of NCEP–NCAR reanalysis data shows that the MJO modifies both the local jet structure and, through changes to the thermodynamic balance, the vertical motion field over Southwest Asia, consistent with the observed modulation of the associated synoptic precipitation. A simple persistence scheme for forecasting the sign of the MJO suggests that the modulation of Southwest Asia precipitation may be predictable for 3-week periods. Finally, analysis of changes in storm evolution in Southwest Asia due to the influence of the MJO shows a large difference in strength as the storms move over Afghanistan, with apparent relevance for the flooding event of 12–13 April 2002.
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Abstract The Madden-Julian Oscillation (MJO) is a large-scale phenomenon of air-sea intra-seasonal variability in the equatorial area, particularly in the Maritime Continent (MC). This research focused on the analysis of the MJO propagation process in association with rainfall events and sea surface temperature anomaly (SSTA) during seasonal variations, i.e., November, December, January February, and March (NDJFM), and May, June, July, August September (MJJAS). MJO events from 2010 to 2019 were classified as MJO active or MJO weakening according to propagation characteristics and amplitude changes in the RMM index. This research uses a dataset of 10-year series of daily Tropical Rainfall Measuring Mission (TRMM) (3B42 V7 derived) measurements for detecting rain rates. Daily OLR data from the NOAA Physical Sciences Laboratory and SSTA daily data from Physical Oceanography Distributed Active Archive Centre (PODAAC) NOAA are considered for analysing MJO propagation. Composites of outgoing longwave radiation (OLR) were also identified differences between the two events; active MJO events had consistently higher negative OLR anomalies than weakening MJO events. Active MJO events during NDJFM had a higher rain rate and positive SSTA than weakening MJO events. Furthermore, composite rain rates distribution over MC during NDJFM are mainly located in the south of the equator, contrarily when MJJAS are north of the equator.
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