Phase3 Enso Case Studies

In the mid-1990s through to early 2000, there were many case studies of El Nino documenting the impact of WWEs and excitation of oceanic Kelvin waves which were believed to have triggered the onset of El Nino (e.g., Kindle and Phoebus, 1995; Kessler et al, 1996; McPhaden, 1999; McPhaden et al, 1988; Yu and Reinecker, 1998; Kutsuwada and McPhadan, 2002). Nakazawa (2000) documented various atmospheric conditions associated with the MJO and tropical cyclone activities during the 1997/1998 El Nino. Indeed, definitive observations of atmospheric MJO signals, and oceanic Kelvin wave responses from satellites and the TOGA-TAO moorings, prior to the onset of the 1997/1998 El Nino re-invigorated the debate on the role of the MJO in possibly leading to the abrupt onset and termination of ENSO cycles (McPhaden and Yu, 1999; Takayabu et al, 1999).

Figure 9.7. Space-time evolution of oceanic-atmospheric variables associated with onset and termination of the 1997/1998 El Nino: (a) Time series of a MJO index (see Section 9.6), and equatorial time-longitude sections of anomalies spanning the Indian Ocean and the Pacific, for (b) pentad 850-mb zonal wind (ms-1), (c) weekly sea level height (cm), and (d) weekly SST (°C). Anomalies are defined with respect to the period from July 1996-July 1998. Contour interval for wind is 0.5ms-1, for sea level is cm, and for SST is 0.2°C.

Figure 9.7. Space-time evolution of oceanic-atmospheric variables associated with onset and termination of the 1997/1998 El Nino: (a) Time series of a MJO index (see Section 9.6), and equatorial time-longitude sections of anomalies spanning the Indian Ocean and the Pacific, for (b) pentad 850-mb zonal wind (ms-1), (c) weekly sea level height (cm), and (d) weekly SST (°C). Anomalies are defined with respect to the period from July 1996-July 1998. Contour interval for wind is 0.5ms-1, for sea level is cm, and for SST is 0.2°C.

0 0

Post a comment