1、BASICS OF EL NIO-SOUTHERN OSCILLATION (ENSO)Ernesto R. VercelesPAGASAWHAT IS EL NIO ?Common notions:“El Nio means no water in faucets and showers”“El Nio means no planting for the season or two”These are partially true these are all impacts of the EL NIOOne newspaper headline: PAGASA insists El Nio

2、already in RP - Despite heavy rains and typhoons (Panay News dated 13 January 2005)“El Nio means severe drought”WHAT IS EL NIO (LA NIA)?El Nio (La Nia) is a condition in the Pacific ocean and characterized by the cyclic warming (cooling) of the central and eastern equatorial Pacific (CEEP). Observed

3、 Sea Surface TemperatureAnalyzed Sea Surface TemperatureEL NIOLA NIALower tempLower tempHigher tempHigher tempCooler tempCooler tempWarmer tempWarmer tempCEEP warmingCEEP coolingMonthly observation and analysis of OCEAN SURFACE during El Nio 1997-98 and La Nia 1998-99El Nino 1997 started in MarchLa

4、Nina 1998 started in JulyMEASURING OCEAN PARAMETERSTHE NIO REGIONSThus, “EL NIO” is a condition in the central and eastern equatorial Pacific Ocean where unusual warming is occurring. (Note that the formation/development of El Nio is very far from the country. )Then, why is it affecting the philippi

5、nes. The answer lies in the atmosphereThe phenomenon is called SOUTHERN OSCILLATIONSouthern Oscillation is the atmospheric component of ENSO and measured in terms of the difference in standardized pressure anomalies over Tahiti and Darwin, and wind anomaly at low level winds (850 mbs level). WHAT IS

6、 SOUTHERN OSCILLATION ?EL NIO CONDITIONLA NIA CONDITIONAustraliaHLHLAustraliaCOMBINED EFFECT OF EL NIO-SOUTHERN OSCILLATION (ENSO) IN THE TROPICAL PACIFICGLOBAL IMPACT OF EL NIO-SOUTHERN OSCILLATION (ENSO)EL NIOLA NIAEL NIOLA NIAIMPACTS OF ENSO and NON-ENSO ON PHILIPPINE ANNUAL RAINFALLRED colored y

7、ears are EL NINO years, Legend: Potential Areas Under Severe drought impactsDrought impacts with major lossesModerate drought impactsNear normal to above normal conditionWay above normal conditionFlood damageSevere flood damageBLUE colored years are LA NINA yearsand BLACK colored years are NON_ENSO

8、yearsDuring El Nio EpisodeDuring La Nia Episode Drier weather conditionsWetter weather conditionsInitial results of diagnostic and statistical studies on general influences of ENSO on Philippine climateWeak monsoon activityWeak tropical cyclones activityBelow normal rainfallAbove normal air temperat

9、ures- occurrence of isolated heavy rainfall in short duration- delayed onset of the rainy season- early termination of the rainy season- tropical cyclones follow tracks further off the Philippines- less number of tropical cyclones entering the Philippine Area of Responsibility (PAR)Above normal rainfallNear-to-below normal air temperaturesModerate to Strong tropical cyclones activityModerate to strong monsoon activity- increased cloudiness and widespread rains- near normal cyclone tracks (near and/or crossing the country)- near norma