The Influence of Recurrent Modes of Climate Variability on the Occurrence of Monthly Temperature Extremes Over South America

Abstract

The associations between extreme temperature months and four prominent modes of recurrent climate variability are examined over South America. Associations are computed as the percent of extreme temperature months concurrent with the upper and lower quartiles of the El Niño–Southern Oscillation (ENSO), the Atlantic Niño, the Pacific Decadal Oscillation (PDO), and the Southern Annular Mode (SAM) index distributions, stratified by season. The relationship is strongest for ENSO, with nearly every extreme temperature month concurrent with the upper or lower quartiles of its distribution in portions of northwestern South America during some seasons. The likelihood of extreme warm temperatures is enhanced over parts of northern South America when the Atlantic Niño index is in the upper quartile, while cold extremes are often association with the lowest quartile. Concurrent precipitation anomalies may contribute to these relations. The PDO shows weak associations during December, January, and February, while in June, July, and August its relationship with extreme warm temperatures closely matches that of ENSO. This may be due to the positive relationship between the PDO and ENSO, rather than the PDO acting as an independent physical mechanism. Over Patagonia, the SAM is highly influential during spring and fall, with warm and cold extremes being associated with positive and negative phases of the SAM, respectively. Composites of sea level pressure anomalies for extreme temperature months over Patagonia suggest an important role of local synoptic scale weather variability in addition to a favorable SAM for the occurrence of these extremes.

Recent marine heatwaves in the North Pacific warming pool can be attributed to rising atmospheric levels of greenhouse gases

“…We arrive at this conclusion by comparing the detected MHWs with events occurring solely in response to the natural variability of the climate system. To obtain these estimates, we use CMIP6 pre-industrial control simulations of daily SST, which provide pseudorealizations of MHWs characteristics in the absence of external climate drivers 43,44 . In this manner, we can identify events that are significantly distinguishable from the distribution of events detected in Pre-industrial climate (Ho: Obs.…”

Interdecadal Variations in Extreme High–Temperature Events over Southern China in the Early 2000s and the Influence of the Pacific Decadal Oscillation

“…The study focuses on the interdecadal variation of FEHE over southern China and the role of the PDO in this interdecadal variation. It is worth noting that the PDO is a significant low-frequency oscillation in the Pacific basin, which has important influence on the global climate [71][72][73]. For example, Hartmann and Wendler [74], and Bieniek and Walsh [75] pointed that the low-frequency variability of temperature extremes in Alaska is attributed to the PDO, and that in the positive phase of PDO, there were positive anomalies of sea level pressure over Alaska, which are favorable for the occurrence of extreme-high temperature events.…”

Association between El Niño and extreme temperatures in southern South America in CMIP5 models. Part 1: model evaluation in the present climate

“…They found that the subtropical jet intensity presented significant positive (negative) correlations with the frequency of cold (warm) extremes in many months. Moreover, Loikith et al (2017) analyzed the associations between extreme temperature in South America and the 4 main modes of climate variability. In particular, ENSO is the mode that presented the strongest relationships with all extreme indices.…”