Global Climate Influencer – Madden Julian Oscillation

MADDEN-JULIAN OSCILLATION GLOBAL CLIMATE INFLUENCER By James Rohman | February 2014

May 17, 2013 October 24, 2013

Figure 1. Following heavy rainfall influenced by the Madden-Julian Oscillation, Typhoon Nari caused substantial flooding along the Mekong and Tonlé Sap Rivers in Cambodia. The flood affected more than 500,000 people, and 300,000 hectares of rice fields were destroyed. The capital city of Phnom Penh (with a population 2.2 million) is marked in the image.

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IntroductionIntroduction

The Madden-Julian Oscillation (MJO) is a slow-moving atmospheric The Madden-Julian Oscillation (MJO) is a slow-moving atmospheric pattern that impacts global tropical and sub-tropical weather. pattern that impacts global tropical and sub-tropical weather. The phenomenon was discovered by Roland Madden and Paul Julian in The phenomenon was discovered by Roland Madden and Paul Julian in 1971. They used ten years of pressure records from Kanton Island and 1971. They used ten years of pressure records from Kanton Island and Singapore to identify a 40-50 day oscillation of zonal wind anomalies in Singapore to identify a 40-50 day oscillation of zonal wind anomalies in the tropical Pacific. the tropical Pacific. Since then, MJO’s recurring pattern of intense rain and thunderstorms Since then, MJO’s recurring pattern of intense rain and thunderstorms followed by an unseasonably dry phase has been identified as occurring followed by an unseasonably dry phase has been identified as occurring every 30-60 days. every 30-60 days. MJO starts in the Indian Ocean as a band of low pressure caused by the MJO starts in the Indian Ocean as a band of low pressure caused by the Indian Ocean Dipole (IOD). It is a naturally occurring component of the ocean Indian Ocean Dipole (IOD). It is a naturally occurring component of the atmosphere. MJO extracts moisture from the water and then drops rain ocean atmosphere. MJO extracts moisture from the water and then and tropical cyclones over the Indian, Southeast Asian and Australian drops rain and tropical cyclones over the Indian, Southeast Asian and regions. Continuing east, MJO can kindle weather systems that batter the Australian regions. Continuing east, MJO can kindle weather systems Pacific Coasts of North and South America with massive rain, heavy that batter the Pacific Coasts of North and South America with massive winds and flooding. rain, heavy winds and flooding. MJO affects the entire tropical troposphere. Its fluctuating cycle is MJO affects the entire tropical troposphere. Its fluctuating cycle is responsible for most of the weather variability in the tropics by impacting responsible for most of the weather variability in the tropics by wind speed and direction, sea surface temperatures (SSTs), rainfall, impacting wind speed direction, sea surface temperatures (SSTs), rainfall, cloudiness and ocean surface evaporation. As a result, tropical weather is cloudiness and ocean surface evaporation. As a result, tropical weather is far less predictable than in the mid-latitudes. far less predictable than in the mid-latitudes. After passing across North and South America, the pattern of strong After passing across North and South America, the pattern of strong tropical rainfall reappears over the tropical Atlantic Ocean and Africa. tropical rainfall reappears over the tropical Atlantic Ocean and Africa. Variations in tropical rainfall are associated with distinct patterns of lower- and Variations in tropical rainfall are associated with distinct patterns of lower- upper-level atmospheric circulation anomalies in the subtropics and tropics. and upper-level atmospheric circulation anomalies in the subtropics and tropics.MJO interacts with the phases of the El Niño Southern Oscillation (ENSO) in the eastern tropical Pacific Ocean. Depending on the phase, ENSO can MJO interacts with the phases of the El Niño Southern Oscillation (ENSO) in increases or decreases the rainfall impact of MJO. the eastern tropical Pacific Ocean. Depending on the phase, ENSO can increasesMJO varies or widely decreases from theyear rainfall to year. impact Periods of MJO.of strong activity are followed by long periods when MJO is weak or completely absent. This MJO varies widely from year to year. Periods of strong activity are may be due to MJO linkage to the ENSO cycle. Strong MJO activity is often followed by long periods when MJO is weak or completely absent. This observed 6-12 months before the onset of El Niño, but is almost absent may be due to MJO linkage to the ENSO cycle. Strong MJO activity is often during the maxima of some El Niño episodes. MJO also tends to be more observed 6-12 months before the onset of El Niño, but is almost absent active during La Niña periods. during the maxima of some El Niño episodes. MJO also tends to be more active during La Niña periods.

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Introduction

The Madden-Julian Oscillation (MJO) is a slow-moving atmospheric pattern that impacts global tropical and sub-tropical weather. The phenomenon was discovered by Roland Madden and Paul Julian in 1971. They used ten years of pressure records from Kanton Island and Singapore to identify a 40-50 day oscillation of zonal wind anomalies in the tropical Pacific.

Since then, MJO’s recurring pattern of intense rain and thunderstorms followed by an unseasonably dry phase has been identified as occurring every 30-60 days.

MJO affects the entire tropical troposphere. Its fluctuating cycle is responsible for most of the weather variability in the tropics by impacting wind speed direction, sea surface temperatures (SSTs), rainfall, cloudiness and ocean surface evaporation. As a result, tropical weather is far less predictable than in the mid-latitudes.

After passing across North and South America, the pattern of strong tropical rainfall reappears over the tropical Atlantic Ocean and Africa. Variations in tropical rainfall are associated with distinct patterns of lower- and upper-level atmospheric circulation anomalies in the subtropics and tropics.

MJO interacts with the phases of the El Niño Southern Oscillation (ENSO) in the eastern tropical Pacific Ocean. Depending on the phase, ENSO can increases or decreases the rainfall impact of MJO.

MJO varies widely from year to year. Periods of strong activity are followed by long periods when MJO is weak or completely absent. This may be due to MJO linkage to the ENSO cycle. Strong MJO activity is often observed 6-12 months before the onset of El Niño, but is almost absent during the maxima of some El Niño episodes. MJO also tends to be more active during La Niña periods.

FigureFigure 2 2. . Vertical Vertical cross cross--sectionsection of of MJO MJO as as it it propagates propagates from from the the Indian Indian Ocean Ocean to to the the westernwestern and and central central Pacific. Pacific.

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IntroductionMJO’s Global Impact Similar to the impacts from each phase of the El Niño Southern Oscillation, the Thephases Madden of the- JulianMadden Oscillation-Julian Oscillation (MJO) is result a slow in predictable-moving atmospheric weather patterns patternTropical that Cyclonesimpacts global in tropical Eastern and Pacific/Gulfsub-tropical weather of Mexico. The phenomenon was discovered by Roland Madden and Paul Julian in 1971.MJO stronglyThey used modulates ten years tropicalof pressure cyclones records in from the Kantoneastern Island Pacific and Ocean . SingaporeDuring we tosterly identify MJO a 40phases,-50 day hurricane oscillation genesis of zonal is fourwind times anomalies more inlikely thethan tropical during Pacificeasterly. periods, and also tends to occur closer to the Mexican coast. Systems that develop during westerly phases are stronger than Sincetropical then, systems MJO’s thatrecurring develop pattern during of intense easterly rain ph andases thundersto. rms followed by an unseasonably dry phase has been identified as occurring everyTropical 30- 60storm days formation. in the Gulf of Mexico is also four times more likely during westerly MJO periods than during easterly MJO periods. So MJOis hurricane starts in genesis, the Indian and Ocean hurricanes as a band that ofare low C ategorypressure 3 caused or above by thehave a Indiangreater Ocean preference Dipole to(IOD). occur It isduring a naturally westerly occurring MJO componentevents. of the ocean atmosphere. MJO extracts moisture from the water and then dropsTropical rain and Cyclones tropical cyclones in Indian over Ocean/Westernthe Indian, Southeast Pacific Asian and Australian regions. Continuing east, MJO can kindle weather systems MJO is known to modulate tropical cyclone activity in the Indian Ocean and that batter the Pacific Coasts of North and South America with massive western Pacific by providing a large-scale environment favorable to tropical rain, heavy winds and flooding. development. MJO affects the entire tropical troposphere. Its fluctuating cycle is The strongest tropical cyclones develop when MJO favors enhanced responsible for most of the weather variability in the tropics by precipitation, although it is important to note MJO is just one of many factors impacting wind speed direction, sea surface temperatures (SSTs), rainfall, that contribute to tropical cyclone development. cloudiness and ocean surface evaporation. As a result, tropical weather is farEffects less predictable on Global than Weather in the mid- latitudes.

AfterMJO canpassing significantly across North intensify and orSouth weaken America, monsoon the pattern systems of instrong Australia,

tropicalIndia, Asia, rainfall South reappears America ove andr theNorth tropical America Atlantic. MJO’s Ocean westerly and phase, Africa. Variationslinked with in enhanced tropical rainfall rainfall, are can associated affect a monsoon’s with distinct timing patterns and ofintensity. lower- andMJO’s upper easterly-level phaseatmospheric can end circulation monsoon anomalies systems early in the, and subtropics even cause and tropics.breaks in monsoon systems.

MJO interacts with the phases of the El Niño Southern Oscillation (ENSO) in MJO is linked to extreme precipitation in the Pacific Northwest, known as the eastern tropical Pacific Ocean. Depending on the phase, ‘Pineapple Express’ events. These occur in boreal winter, whenENSO the can easterly increasesMJO interacts or decreases with westward the Northrainfall Pacific impact mid of-latitude MJO. patterns (creating heavy flooding such as the 1996-7 winter in California and Pacific Northwest). MJO varies widely from year to year. Periods of strong activity are For 7-10 days preceding a Pineapple Express event, there are distinct followed by long periods when MJO is weak or completely absent. This mayweather be due anomalies to MJO linkage in the Pacificto the ENSO Northwest cycle. andStrong subtropical MJO activity Pacific is often There is a clear relationship between MJO-related rainfall and extreme observedOcean. 6-12 months before the onset of El Niño, but is almost absent west coast precipitation events. during the maxima of some El Niño episodes. MJO also tends to be more active during La Niña periods. MJO can alter the intensity and extent of the South Atlantic Convergence Zone and the South Pacific Convergence Zone, to enhance rainfall over Southeast Brazil, or Australia and the Philippines, respectively.

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MJO can alter the intensity and extent of the South Atlantic Convergence Zone and the South Pacific Convergence Zone, to enhance rainfall over Southeast Brazil, or Australia and the Philippines, respectively. MJO can alter the intensity and extent of the South Atlantic Convergence Zone and the South Pacific Convergence Zone, to enhance rainfall over Southeast Brazil, or Australia and the Philippines, respectively. MJO’s Regional Impacts

IntroductionMJO’s Regional Impacts

Boreal winter The Madden -Julian Oscillation (MJO) is a slow-moving atmospheric pattern that impacts global tropical and sub-tropical weather.

The phenomenon was discovered by Roland Madden and Paul Julian in

1971. They used ten years of pressure records from Kanton Island and Singapore to identify a 40-50 day oscillation of zonal wind anomalies in

the tropical Pacific.

Since then, MJO’s recurring pattern of intense rain and thunderstorms followed by an unseasonably dry phase has been identified as occurring

every 30-60 days.

MJO starts in the Indian Ocean as a band of low pressure caused by the

Australia n regions. Continuing east, MJO can kindle weather systems that batter the Pacific Coasts of North and South America with massive 1. Alternating periods of wetter/drier conditions in the tropics 4. In uence on tropical cyclone development rain, heavy winds and flooding. 2. “Pineapple express” heavy rainfall events 5. Modulation of ENSO cycle through oceanic Kelvin waves 3. Modulation of monsoon systems MJO affects the entire tropical troposphere . Its fluctuating cycle is

Figureresponsible 3. Typical MJOfor most impacts of seen the weatherduring the variabilityboreal winter. in the tropics by

impacting wind speed direction, sea surface temperatures (SSTs), rainfall, cloudiness and ocean surface evaporation. As a result, tropical weather is

Boreal summer Figurefar less 3. Typicalpredictable MJO impacts than in seen the during mid-latitudes. the boreal winter.

After passing across North and South America, the pattern of strong

tropical rainfall reappears over the tropical Atlantic Ocean and Africa.

Variations in tropical rainfall are associated with distinct patterns of lower- and upper-level atmospheric circulation anomalies in the subtropics and tropics.

MJO interacts with the phases of the El Niño Southern Oscillation (ENSO) in

the eastern tropical Pacific Ocean. Depending on the phase, ENSO can increases or decreases the rainfall impact of MJO.

observed 6-12 months before the onset of El Niño, but is almost absent 4 4 Global Climate Influencer | Madden-Julian Oscillationduring the maxima of some El Niño episodes. MJO also tends to be more active during La Niña periods. 1. Alternating periods of wetter/drier conditions in the tropics

Global Climate2. InfluencerModulation | of Madden monsoon-Julian systems Oscillation 4 4 3. In uence on tropical cyclone development

Figure 4 . Typical MJO impacts associated with the boreal summer.

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IntroductionMonitoring & Predicting MJO Due to MJO’s impact on tropical weather, it is imperative to track and predict Theits development, Madden-Julian movement Oscillation and impact.(MJO) isOver a slow the- movingpast ten atmospheric years, NOAA has developed mathematical models to predict MJO, using a variety of pattern that impacts global tropical and sub-tropical weather. analysis techniques and data. NOAA’s polar orbiting and geostationary Thesatellites phenomenon generate was data discovered on strong by tropical Roland Maddenconvective and activityPaul Julian and in 1971.regional They rainfall used tenanomalies years of. pressureThese ‘departures records from-from Kanton-normal’ Island are a and main Singaporediagnostic totool identify used toa 40monitor-50 day and oscillation predict the of global zonal schematic wind anomalies of MJO. in the tropical Pacific. The global radiosonde network also provides useful information on Sincemoisture, then, temperature, MJO’s recurring atmospheric pattern of intense winds andrain andpressure thundersto at multiplerms followedaltitudes by. Twice an unseasonably daily the dataset dry phase is integ hasrated been into identified dynamic as weather occurring everyprediction 30-60 models days. to drive climate analysis and numerical weather prediction. MJO starts in the Indian Ocean as a band of low pressure caused by the Indian Ocean Dipole (IOD). It is a naturally occurring component of the ocean atmosphere. MJO extracts moisture from the water and then drops rain and tropical cyclones over the Indian, Southeast Asian and Australian regions. Continuing east, MJO can kindle weather systems that batter the Pacific Coasts of North and South America with massive rain, heavy winds and flooding.

MJO interacts with the phases of the El Niño Southern Oscillation (ENSO) in the eastern tropical Pacific Ocean. Depending on the phase, ENSO can increases or decreases the rainfall impact of MJO.

MJO varies widely from year to year. Periods of strong activity are followed by long periods when MJO is weak or completely absent. This mayFigure be 5 due. Radiosonde to MJO linkageunit used to to the measure ENSO various cycle. atmospheric Strong MJO parameters activity is. often observed 6-12 months before the onset of El Niño, but is almost absent during the maxima of some El Niño episodes. MJO also tends to be more The satellite and radiosonde data allow meteorologists to monitor and active during La Niña periods. assess MJO and its evolution.

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Introduction

The Madden-Julian Oscillation (MJO) is a slow-moving atmospheric pattern that impacts global tropical and sub-tropical weather.

The phenomenon was discovered by Roland Madden and Paul Julian in

1971. They used ten years of pressure records from Kanton Island and Singapore to identify a 40-50 day oscillation of zonal wind anomalies in

. the tropical Pacific

Since then, MJO’s recurring pattern of intense rain and thunderstorms followed by an unseasonably dry phase has been identified as occurring

every 30-60 days.

MJO starts in the Indian Ocean as a band of low pressure caused by the

Australia n regions. Continuing east, MJO can kindle weather systems that batter the Pacific Coasts of North and South America with massive

rain, heavy winds and flooding.

MJO affects the entire tropical troposphere. Its fluctuating cycle is responsible for most of the weather variability in the tropics by

impacting wind speed direction, sea surface temperatures (SSTs), rainfall, cloudiness and ocean surface evaporation. As a result, tropical weather is

far less predictable than in the mid-latitudes.

After passing across North and South America, the pattern of strong tropical rainfall reappears over the tropical Atlantic Ocean and Africa. Figure 6. A recent example from the MJO Dynamic Model Forecast. Variations in tropical rainfall are associated with distinct patterns of lower- andNOAA upper has-level a working atmospheric group circulation that creates anomalies MJO diagnostics in the subtropics. Their and Index tropics.Forecast , as displayed in Figure 6, gives two week predictions for MJO.

MJOThe forecastinteracts iswith divided the phases into octantsof the El. WhenNiño Souther MJO isn in Oscillation a particular (ENSO) octant init thewill easternenhance tropical convective Pacific development Ocean. Depending in a corresponding on the phase, part ENSO of the canworld. increasesFor example or, decreaseswhen MJO theis in rainfall phases impact1, 2 and of strong MJO. in phase 3, there will be enhanced rainfall across Mexico and the Caribbean and an increased MJO varies widely from year to year. Periods of strong activity are chance for tropical cyclone development during the tropical season across followed by long periods when MJO is weak or completely absent. This the East Pacific, Gulf of Mexico and Caribbean. There are corresponding may be due to MJO linkage to the ENSO cycle. Strong MJO activity is often forecasts for each part of the globe. observed 6-12 months before the onset of El Niño, but is almost absent duringThe circle the maximain the center of some of the El graphicNiño episodes. gives a senseMJO also of the tends intensity to be. moreMJO activebecomes during stronger La Niña as periods. the forecast moves away from the center of the Plotted points within the circle indicate a very weak or concentric circle. minimal MJO signal.

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IntroductionSummary of Conditions

TheTable Madden 1. Summary-Julian of Oscillation conditions expected(MJO) is froma slow the-moving phases atmosphericof MJO. pattern that impacts global tropical and sub-tropical weather.

The phenomenon was discovered by Roland Madden and Paul Julian in 1971. They used ten years of pressure records from Kanton Island and Singapore to identify a 40-50 day oscillation of zonal wind anomalies in the tropical Pacific. Since then, MJO’s recurring pattern of intense rain and thunderstorms followed by an unseasonably dry phase has been identified as occurring every 30-60 days.

MJO starts in the Indian Ocean as a band of low pressure caused by the Indian Ocean Dipole (IOD). It is a naturally occurring component of the ocean atmosphere. MJO extracts moisture from the water and then drops rain and tropical cyclones over the Indian, Southeast Asian and Australian regions. Continuing east, MJO can kindle weather systems that batter the Pacific Coasts of North and South America with massive rain, heavy winds and flooding. MJO affects the entire tropical troposphere. Its fluctuating cycle is responsible for most of the weather variability in the tropics by impacting wind speed direction, sea surface temperatures (SSTs), rainfall, cloudiness and ocean surface evaporation. As a result, tropical weather is far less predictable than in the mid-latitudes.

After passing across North and South America, the pattern of strong

tropical rainfall reappears over the tropical Atlantic Ocean and Africa. Variations in tropical rainfall are associated with distinct patterns of lower- and upper-level atmospheric circulation anomalies in the subtropics and tropics.

MJO interacts with the phases of the El Niño Southern Oscillation (ENSO) in the eastern tropical Pacific Ocean. Depending on the phase, ENSO can

increases or decreases the rainfall impact of MJO.

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IntroductionThe Future Why is it important? The Madden-Julian Oscillation (MJO) is a slow-moving atmospheric patternMJO’s 30 that-60 impacts day oscillation global is tropical the largest and element sub-tropical of variability weather in .weather throughout the global tropics. The diagnostics give an indication of the The phenomenon was discovered by Roland Madden and Paul Julian in position of convection and tropical storms in equatorial countries. 1971. They used ten years of pressure records from Kanton Island and SingaporeWhat does to identify it mean? a 40-50 day oscillation of zonal wind anomalies in the tropical Pacific. From its genesis in the Indian Ocean to its final dissipation over the Atlantic, SinceMJO exhibits then, MJO’s distinct recurring atmospheric pattern behavior of intense. Through rain and Westerly thundersto andrms Easterly followedphases, byMJO an eitherunseasonably increase drys or phase decrease has beens the identified potential as for occurring extreme everyweather 30- in60 tropicaldays. ocean basins.

MJOThe location starts in and the phaseIndian ofOcean the lower as a- bandlevel andof low upper pressure-level atmosphericcaused by the Indiancirculation Ocean anomalies Dipole (IOD). influence It is aweather naturally patterns occurring in component North America, of the oceanCentral atmosphere. America, South MJO exAmerica,tracts moisture Africa, Asia from and the Australia water and, where then dropsdense rainpopulations and tropical and heavily cyclones insured over values the Indian, reside. Southeast Asian and Australian regions. Continuing east, MJO can kindle weather systems thatDeveloping batter the a greater Pacific understandingCoasts of North of and the Southscience America of the Mwithadden massive- rain,Julian heavy Oscillation winds andcan flooding.therefore assist insurance underwriters in understanding regional weather patterns and their subsequent impact MJOon insured affects exposures.the entire tropical troposphere. Its fluctuating cycle is responsible for most of the weather variability in the tropics by impacting wind speed direction, sea surface temperatures (SSTs), rainfall, cloudiness and ocean surface evaporation. As a result, tropical weather is far less predictable than in the mid-latitudes.

MJO interacts with the phases of the El Niño Southern Oscillation (ENSO) in the eastern tropical Pacific Ocean. Depending on the phase, ENSO can increases or decreases the rainfall impact of MJO.

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IntroductionGlossary Boreal - Of or relating to the Northern hemisphere. The Madden-Julian Oscillation (MJO) is a slow-moving atmospheric patternConvection that impacts– Upward global flowing tropical air currents and subthat -createtropical clouds. weather Convection. is directly associated with rainfall patterns. The phenomenon was discovered by Roland Madden and Paul Julian in 1971.Easterly They MJO used- The ten ‘dryer’ years andof pressure ‘calmer’ records phase of from MJO. Kanton Island and Singapore to identify a 40-50 day oscillation of zonal wind anomalies in theEl Niño tropical - Anomalously Pacific. warm phase of ENSO cycle.

SinceEl Niño then, Southern MJO’s recurringOscillation pattern (ENSO) of intense – The 2rain-5 year and Pacificthundersto Oceanrms cycle followedbetween byEl anNiño unseasonably and La Niña dryconditions phase has that been affects identified 60% of asglobal occurring weather. every 30-60 days. Indian Ocean Dipole (IOD) – Also known as the Indian Nino, IOD is an MJOirregular starts oscillation in the Indian of sea Ocean surfa ceas temperaturesa band of low inpressure which the caused western by theIndian IndianOcean Ocean alternates Dipole between (IOD). anomalously It is a naturally warm occurring and cold component phases. of the ocean atmosphere. MJO extracts moisture from the water and then La Niña- Anomalously cold phase of ENSO. drops rain and tropical cyclones over the Indian, Southeast Asian and AustraliaPineapplen Expressregions.- Continuing The non-technical east, MJO term can used kindle to describe weather the systems thatmeteorological batter the phenomenonPacific Coasts whereby of North heavy and precipitationSouth America is dumped with massive along rain,the Pacific heavy Coast, winds anywhere and flooding. from Vancouver to Los Angeles.

MJOMadden affects-Julian the entireOscillation tropical (MJO) troposphere – A slow. Its-moving fluctuating atmospheric cycle ispattern responsiblethat impacts globalfor most tropical of the and weather sub-tropical variability weather. in the It is tropics an intraseasonal by impactingwave (30- 60wind days) speed tha direction,t creates largesea surfac-scalee variability temperatures in tropical (SSTs), weather. rainfall, cloudiness and ocean surface evaporation. As a result, tropical weather is farMJO less Index predictable Forecast than- A dynamic in the mid forecast-latitudes. for MJO that incorporates global databases to create a two-week prediction. After passing across North and South America, the pattern of strong tropicalRadiosonde rainfall- A piecereappears of equipment over the used tropical on weather Atlantic balloons Ocean usedand Africa. to Variationsmeasure various in tropical atmo rainfallspheric are parameters. associated with distinct patterns of lower- and upper-level atmospheric circulation anomalies in the subtropics and tropics.South Atlantic Convergence Zone (SACZ) - An elongated string of clouds, precipitation and convergent winds oriented across Brazil into the Atlantic MJOOcean. interacts It is a monsoonwith the phases trough ofthat the helps El Niño define Souther Brazil’sn Oscillation rainy season. (ENSO) in the eastern tropical Pacific Ocean. Depending on the phase, ENSO can – Similar to the SACZ, SPCZ is increasesSouth Pacific or decreases Convergence the rainfallZone (SPCZ) impact of MJO. a band of low pressure that extends from the west Pacific into French MJOPolynesia. varies widely from year to year. Periods of strong activity are followed by long periods when MJO is weak or completely absent. This - Phase of MJO that favors tropical development and extreme mayWesterly be due MJO to MJO linkage to the ENSO cycle. Strong MJO activity is often convective precipitation. observed 6-12 months before the onset of El Niño, but is almost absent during the maxima of some El Niño episodes. MJO also tends to be more active during La Niña periods.

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Contacts Introduction To discuss any of the contents of this paper, please contact:

The MaddenJames-Julian Rohman Oscillation (MJO) is a slow-moving atmospheric pattern thatGlobal impacts Catastrophe global Management tropical and, subNew-t ropicalYork weather. The phenomenonT: 1 (212) was 365 discovered2438 by Roland Madden and Paul Julian in 1971. TheyE: [email protected] ten years of pressure records from Kanton Island and Singapore to identify a 40-50 day oscillation of zonal wind anomalies in the tropical Pacific. To discuss the implications of this paper, and your reinsurance needs in response,Since then, please MJO’s contact: recurring pattern of intense rain and thunderstorms followed by an unseasonably dry phase has been identified as occurring Paul Mckeon every 30-60 days. Chief Underwriting Officer, North America MJO starts in the Indian Ocean as a band of low pressure caused by the T: 1 (212) 365 2120 Indian OceanE: [email protected] Dipole (IOD). It is a naturally occurring component of the ocean atmosphere. MJO extracts moisture from the water and then drops rain and tropical cyclones over the Indian, Southeast Asian and Australian regions. Continuing east, MJO can kindle weather systems

that batterJavier the PacificVijil Coasts of North and South America with massive President, Latin America rain, heavy winds and flooding. T: 1 (786)-437-3901 MJO affects the entire tropical troposphere. Its fluctuating cycle is E: [email protected] responsible for most of the weather variability in the tropics by impacting wind speed direction, sea surface temperatures (SSTs), rainfall, cloudiness and ocean surface evaporation. As a result, tropical weather is far less predictableAndy Taylor than in the mid -latitudes. Chief Underwriting Officer, Asia-Pacific Region After passing across North and South America, the pattern of strong tropical T:rainfall +44-20 reappears-7204-8604 ove r the tropical Atlantic Ocean and Africa. E: [email protected] Variations in tropical rainfall are associated with distinct patterns of lower- and upper-level atmospheric circulation anomalies in the subtropics and tropics. Geoff Peach MJO interactsDeputy with CEO, the TransRephases of London the El NiñoLimited Souther n Oscillation (ENSO) in the eastern tropical Pacific Ocean. Depending on the phase, ENSO can increasesT: or+44 decreases-20-7204- 8607the rainfall impact of MJO. E: [email protected] MJO varies widely from year to year. Periods of strong activity are followed by long periods when MJO is weak or completely absent. This may be due to MJO linkage to the ENSO cycle. Strong MJO activity is often observed 6-12 months before the onset of El Niño, but is almost absent during the maxima of some El Niño episodes. MJO also tends to be more active during La Niña periods.

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IntroductionCitations Gottschalk et al. from NOAA and NWS. ‘Madden Julian Oscillation (MJO)’ Thehttp://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/MJO_summary.pdf Madden-Julian Oscillation (MJO) is a slow-moving atmospheric pattern that impacts global tropical and sub-tropical weather. Hartmann, L, and Hendon, H. (2007). ‘Resolving an Atmospheric Enigma’. The phenomenon was discovered by Roland Madden and Paul Julian in 1971.NOAA They and usedNWS tenMJO years Prediction of pressure Center records Online from Kanton Island and Singaporehttp://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml to identify a 40-50 day oscillation of zonal wind anomalies in

theNASA tropical. Cover Pacific image,. outer fringes of 2010 Hurricane Earl over the Atlantic.

SinceDictionary then, ofMJO’s Language recurring Terminology. pattern of intense rain and thunderstorms followedhttp://www.odlt.org/dcd/ballast/radiosondes.html by an unseasonably dry phase has been identified as occurring every 30-60 days. The University Corporation for Atmospheric Research and NWS- MJOhttps://w startsww.meted.ucar.edu/index.php in the Indian Ocean as a band of low pressure caused by the

Indian Ocean Dipole (IOD). It is a naturally occurring component of the ocean atmosphere. MJO extracts moisture from the water and then drops rain and tropical cyclones over the Indian, Southeast Asian and Australian regions. Continuing east, MJO can kindle weather systems that batter the Pacific Coasts of North and South America with massive rain, heavy winds and flooding.

MJO interacts with the phases of the El Niño Southern Oscillation (ENSO) in the eastern tropical Pacific Ocean. Depending on the phase, ENSO can increases or decreases the rainfall impact of MJO.

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Copyright and Disclaimers Introduction The material and conclusions contained in this document are for information The Madden-Julian Oscillation (MJO) is a slow-moving atmospheric purposes only and the authors offer no guarantee for the completeness of its patterncontents. that The impacts statements global in thistropical document and sub may-t ropicalprovide weathercurrent expectations. Theof future phenomenon events based was discoveredon certain assumptions.by Roland Madden These and statements Paul Julian involve in 1971.known They and usedunknown ten yearsrisks, ofuncertainties pressure records and other from factors Kanton which Island are and not Singaporeexhaustive. to The identify authors a 40 of-50 this day document oscillation undertake of zonal no wind obligation anomalies to publicly in therev isetropical or update Pacific any. statements, whether as a result of new information, future events or otherwise and in no event shall Transatlantic Reinsurance SinceCompany then, or MJO’s any of recurring its affiliates pattern or employees of intense berain liable and forthundersto any damagerms and followedfinancial byloss an arising unseasonably in connection dry phase with thehas use been of identifiedthe information as occurring relating to everythis document. 30-60 days .

MJOAbout starts TransRe in the Indian Ocean as a band of low pressure caused by the Indian Ocean Dipole (IOD). It is a naturally occurring component of the oceanTransRe atmosphere. is the brand MJO name ex fortracts Transatlantic moisture Holdings, from the Inc. water and andits subsidiaries then drops(including rain Transatlantic and tropical Reinsurance cyclones over Company). the Indian, TransRe, Southeast wholly ownedAsian byand AustraliaAlleghanyn Corporation regions. Continuing (NYSE-Y) ,east is a, reinsurance MJO can kindle organization weather headquartered systems thatin New batter York the with Pacific operations Coasts worldwide. of North Since and 1978, South TransRe America has with been massive offering rain,its clients heavy the winds capacity, and expertise flooding. and creativity necessary to structure programs across the full spectrum of property and casualty risks. MJO affects the entire tropical troposphere. Its fluctuating cycle is responsibleVisit www.transre.com for most of for the additional weather information.variability in the tropics by impacting wind speed direction, sea surface temperatures (SSTs), rainfall, © 2013 Transatlantic Reinsurance Company. All rights reserved. cloudiness and ocean surface evaporation. As a result, tropical weather is far less predictable than in the mid-latitudes.

AfterTransatlantic passing acrossReinsurance North Companyand South America, the pattern of strong tropical80 Pine rainfallStreet reappears over the tropical Atlantic Ocean and Africa. VariationsNew York, in New tropical York rainfall 10005 are associated with distinct patterns of lower- and upper-level atmospheric circulation anomalies in the subtropics and tropics.

MJO interacts with the phases of the El Niño Southern Oscillation (ENSO) in the eastern tropical Pacific Ocean. Depending on the phase, ENSO can increases or decreases the rainfall impact of MJO.

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Introduction

Since then, MJO’s recurring pattern of intense rain and thunderstorms followed by an unseasonably dry phase has been identified as occurring every 30-60 days.

MJO interacts with the phases of the El Niño Southern Oscillation (ENSO) in the eastern tropical Pacific Ocean. Depending on the phase, ENSO can increases or decreases the rainfall impact of MJO.

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