Predictability of Eastern Pacific Intraseasonal Variability

Session I: Identifying opportunities and challenges of observing and modeling IAS variability and its teleconnections
Neena Joseph
Jet Propulsion Laboratory, California Institute of Technology
The eastern Pacific (EPAC) warm pool is a region of strong intraseasonal variability (ISV) during boreal summer. The 30–50 days ISV mode of EPAC is characterized by eastward propagation of convective anomalies. In addition to this mode, a quasi biweekly mode of about 16 day periodicity is also prominent over the EPAC domain. Also, similar to the Asian monsoon ISV, the EPAC ISV exhibits some northward propagation, possibly due to the presence of strong vertical wind shear over the warm pool. It is known to impact and modulate the tropical cyclone activity over EPAC and Gulf of Mexico, it also impacts the summertime wind jets and precipitation, the North American monsoon and the mid-summer droughts over Central America and Mexico. Global weather and climate models show relatively poor skill in simulating the EPAC ISV. In the present study, the predictive skill and potential predictability of the EPAC ISV are explored in eight coupled model hindcasts from the Intraseasonal Variability Hindcast Experiment (ISVHE). The average prediction skill associated with EPAC ISV is found to be around 10 days while it exhibits a predictability of about 20–30 days. The association between the MJO phases and EPAC ISV phases were also explored and it was found that some models show a higher prediction skill for EPAC ISV when MJO convective phase was over the western Pacific, signaling the importance of understanding the dynamic link between the MJO and the EPAC ISV.
2015 - 13:25
Wednesday, September 9, 2015