Most of the time ,trade winds push surface water across the Pacific towards Australia and the Philippines ,piling up warm water in the Western Pacific .But when these trade winds slacken or disappear altogether ,the pool of warm waters flows eastwards -the sign that an El Nino episode is underway .
This anomaly of the ocean /atmosphere system was responsible for 22,000 deaths in 1997 -1998 .That EL Nino was also the first such event monitored by satellite ,with TOPEX /Poseidon detecting the first tell -tale signs very early on ,revealing a bulge of warm water working its way across the ocean ,20 to 30 centimeters higher than the mean level .
Since that episode ,EL Nino has returned regularly every three to seven years .Luckily ,scientists have been able to develop reliable ocean -atmosphere models , thanks largely to satellite altimetry data ,and measures to protect populations are put in place six to nine months ahead .
In march 2016 , when EL Nino hit Peru ,the country had been on alert since the previous summer .EL Nino is not the only large -scale ocean anomaly :its cousin La Nina brings a reverse pattern with abnormally cold Pacific surface waters ,but its impacts are smaller .The Jason ,SARAL /AltiKa and Sentinel -3 altimetry missions are keeping a constant eye on these climate events .
This anomaly of the ocean /atmosphere system was responsible for 22,000 deaths in 1997 -1998 .That EL Nino was also the first such event monitored by satellite ,with TOPEX /Poseidon detecting the first tell -tale signs very early on ,revealing a bulge of warm water working its way across the ocean ,20 to 30 centimeters higher than the mean level .
Since that episode ,EL Nino has returned regularly every three to seven years .Luckily ,scientists have been able to develop reliable ocean -atmosphere models , thanks largely to satellite altimetry data ,and measures to protect populations are put in place six to nine months ahead .
In march 2016 , when EL Nino hit Peru ,the country had been on alert since the previous summer .EL Nino is not the only large -scale ocean anomaly :its cousin La Nina brings a reverse pattern with abnormally cold Pacific surface waters ,but its impacts are smaller .The Jason ,SARAL /AltiKa and Sentinel -3 altimetry missions are keeping a constant eye on these climate events .
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