Ms. Roulston et Jd. Neelin, The response of an ENSO model to climate noise, weather noise and intraseasonal forcing, GEOPHYS R L, 27(22), 2000, pp. 3723-3726
The response of an intermediate coupled model of the: tropical Pacific to d
ifferent forms of stochastic wind forcing is studied. An estimate of observ
ed Pacific wind variance that is unrelated to Pacific sea surface temperatu
re (SST) has a red spectrum, inconsistent with standard definitions of "wea
ther noise". The reddening is likely due to SST outside the basin; we propo
se a definition of "climate noise" for such reddened variance. Effects are
compared for (i) red climate noise; (ii) the corresponding white weather no
ise estimate; (iii) intraseasonal and interannual components of the white n
oise (to test frequency response); and (iv) a noise product with Extra powe
r in the 30-60 day range. Power is not effectively channeled from subannual
frequencies to the frequencies associated with ENSO in this model. This su
ggests that ENSO impacts of the Madden-Julian oscillation are largely restr
icted to the low-frequency tail rather than the 30-60 day spectral peak. In
terannual climate noise originating outside the tropical Pacific appears im
portant.