The circulation of positive PNA index pattern is prominent in the case of persistent forcing of negative SSTA in West Wind Drift region or positive SSTA in tropical eastern Pacific, which is the typical SSTA Pattern during El Nino peak-mature phase.

• 西风漂流区持续负SSTA时或者热带中东太平洋持续正SSTA时，阿留申低压均有所加强，正PNA指数型的大气环流特征显著。 而当相反符号的SSTA持续作用时，大气中阿留申低压减弱，对应PNA指数为负。