|Title||The Pacific Meridional Mode and ENSO: A Review|
|Publication Type||Journal Article|
|Year of Publication||2019|
|Type of Article||Review|
|Keywords||climate; climate change; Climate dynamics; climate modeling; Climate prediction; Coupled model; decadal variability; El Nino-southern oscillation; el-nino; Energetics framework; extratropical atmospheric variability; Extratropical-tropical interactions; forecasting; internal variability; ITCZ shifts; Meteorology & Atmospheric Sciences; north pacific; ocean; oscillation; pacific; Pacific decadal variability; Pacific meridional mode; paleoclimate; seasonal footprinting mechanism; south; Subseasonal-to-seasonal; teleconnections; tropical variability; Tropics; variability|
This paper reviews recent progress in understanding of the North Pacific Meridional Mode (NPMM) and its influence on the timing, magnitude, flavor, and intensity of the El Nino-Southern Oscillation (ENSO). Recent Findings The NPMM is a seasonally evolving mode of coupled climate variability and features several distinct opportunities to influence ENSO. They include: (1) AWind-Evaporation-SST (WES) feedback-driven propagation of surface anomalies onto the equator during boreal spring, (2) Trade Wind Charging (TWC) of equatorial subsurface heat content by NPMM-related surface wind stress curl anomalies in boreal winter and early spring, (3) The reflection of NPMM-forced ocean Rossby waves off the western boundary in boreal summer, and (4) A Gill-like atmospheric response associated with anomalous deep convection in boreal summer and fall. The South Pacific Meridional Mode (SPMM) also significantly modulates ENSO, and its interactions with the NPMMmay contribute to ENSO diversity. Together, the NPMMand SPMMare also important components of Tropical Pacific Decadal Variability; however, future research is needed to improve understanding on these timescales. Summary Since 1950, the boreal spring NPMM skillfully predicts about 15-30% of observed winter ENSO variability. Improving simulated NPMM-ENSO relationships in forecast models may reduce ENSO forecasting error. Recent studies have begun to explore the influence of anthropogenic climate change on the NPMM-ENSO relationship; however, the results are inconclusive.