太平洋—印度洋海表温度加热对中高纬低频振荡的调频作用

Modulation of Atmospheric Low-Frequency Oscillations in the Middle Latitudes with the Heating of Sea Surface Temperature in the Pacific Ocean and the Indian Ocean

用数值试验的方法,分别以无热源型、E lN ino初期、E l N ino成熟期对应的赤道中东太平洋与赤道印度洋海表温度作为外强迫源,应用强迫耗散准地转正压涡度方程的全球谱模式,考虑了摩擦耗散及3波准共振的共同作用,采用非定常、定常加热两种形式积分90 d,研究了对中高纬大气低频振荡的调频作用。结果表明:(1)3个行星波之间存在很强的波—波相互作用,且波动振荡呈现准双周和季节内振荡;(2)在E lN ino初期和E lN ino成熟期,无论是赤道中东太平洋海温还是赤道印度洋海温在逐渐增暖的过程中,大气低频振荡周期都有缩短的趋势。1997年2月—1997年4月,赤道印度洋调节作用强;而在1998年5月,赤道中东太平洋调节作用强;(3)赤道印度洋西区对大气低频振荡的调节作用要强于赤道印度洋东区;N ino3区对大气低频振荡的调节作用要强于N ino1+2区;(4)太平洋—印度洋海温异常模态在1997年10月为高指数(简称PIM I一型),在1996年9月为低指数(简称PIM I二型),前者对应的东太平洋—西印度洋区对大气的调频作用要大于后者对应的西太平洋—东印度洋区。

Numerical experiments on forcing dissipation and the condition of three waves quasi-resonance are carried out using a global spectral model of quasi-geostrophic barotropic vorticity equation. For every experiment the model integration is run for 90 days on the heating responses of no heat source, and sea surface temperatures at the El Nino initial and mature stages. The results are given as follow： （ 1 ） there is strong interaction among the three planetary waves and waves exhibit the quasi-two-week and intra-seasonal oscillations; （2） both the warming of sea surface temperatures of the equatorial Pacific and equatorial Indian Ocean at the El Nino initial and mature stages make the atmospheric low-frequency oscillation,but the equatorial Indian Ocean SST forcing makes more contribution from February to April, 1997 ,while the equatorial Pacific SST contributes more in May 1998 ; （ 3 ） the western equatorial Indian Ocean has more frequency modulation effect on atmospheric low-frequency oscillations than the eastern equatorial Indian Ocean,and the Nino3 region has more frequency modulation effect on atmospheric low-frequency oscillations than the Ninol ＋ 2 region ; （4 ） the eastern Pacific-western Indian Ocean region has more frequency modulation effect on atmospheric low-frequency oscillations in October 1997 （ a high index phase for Pacificn-lndian Ocean SST anomaly mode：the first type of PIMI） than the western Pacificn-eastern Indian Ocean in September 1996（a low index phase ：the second type of PIMI）.