Combined impacts of the El Niño‐Southern Oscillation and Pacific Decadal Oscillation on global droughts assessed using the standardized precipitation evapotranspiration index

Abstract

Using the standardized precipitation evapotranspiration index, this study examines the combined effects of El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) on global droughts in terms of magnitude, timing, and duration. The ENSO-affected drought hotspots are identified based on drought magnitude and probability of occurrence: five hotspots for El Niño (Amazon, India, central China, Indonesia, and eastern Australia) and four hotspots for La Niña (southeastern United States, southern South America, East Africa, and Southwest Asia). When ENSO and PDO are in phase, most of the hotspots exhibit an intensification and expansion of drought, more clearly at longer time scales (6-12 months), supporting previous studies. Interestingly, the in-phase PDO advances El Niño-induced drought onset by early summer of the previous year, whereas it delays the withdrawal of La Niña-induced drought until the end of the event year. This asymmetric response is found to be in part associated with the earlier start and later end of El Niño itself during warm PDO, which does not hold for the La Niña/cold PDO composites. Further analyses of the responses of precipitation (P) and potential evapotranspiration (PET) to different ENSO-PDO combinations suggest the important role of P reduction in determining drought magnitude and timing over most of the hotspots, with some contribution of enhanced PET to drier conditions over a few La Niña hotspots. It is also found that the PDO modulation of El Niño-induced drought occurs primarily through the eastern Pacific El Niño with a limited influence on the central Pacific El Niño.

Identifying ENSO-related interannual and decadal variability on terrestrial water storage

“…Figure 4 a shows consistency with Chen et al 14 , showing that 2015–2016 El Niño causes drought, but La Niña (2010–2011) disagrees with the observation. The observed TWS shows the increase in 2011–2012 when the La Niña is weaker than 2010–2011, and it agrees with the previous studies 41 , 42 ; the LF mode (or PDO) intensifies the increase of TWS. Basin-wide comparisons are complicated because the dynamic spatial variance presented in this region creates difficulties in explaining the regional TWS using an ENSO index.…”

Increased Fire Activity in Alaska Since the 1980s: Evidence From an Ice Core‐Derived Black Carbon Record

“…(2001) showed that most of the large fires in Alaska occurred during moderate to strong El Niño events. During El Niño events, temperatures are typically near normal in western Alaska and often much warmer in southeastern Alaska (Hess et al., 2001; Nguyen et al., 2021; Papineau, 2001). In addition, Hess et al.…”

Comparative Assessment of Standard Precipitation Index and Standard Precipitation Evapotranspiration Index as Drought Evaluation Tools in Coastal Winneba-Ghana

“…The SPEI package requires long term temperature (maximum and minimum) and rainfall data. The SPEI has been employed in many drought studies and has been found suitable [8,37,38,39,40]. To estimate the value of SPEI, the variation in water balance is normalized as log-logistic probability distribution.…”