This study examined the contribution of the Pacific decadal oscillation (PDO) to the record-breaking 2013–17 drought in the Korean Peninsula. The meteorological drought signal, measured by the Standardized Precipitation Index (SPI), in 2013 and 2016 co-occurred with a heat wave. The positive phase of the PDO during the mid-2010s was responsible for the precipitation deficit, particularly in 2014, 2015, and 2017, resulting in 5 years of meteorological drought. The enhanced atmospheric heating anomalies over the subtropical central Pacific, induced by the in situ PDO-related sea surface temperature (SST) warming, led to a low-atmospheric cyclonic flow centered over the midlatitude Pacific. The northerly wind anomalies at the western edge of this low-level cyclonic flow were responsible for the horizontal negative advection of moist energy, which contributed to the decreased precipitation and the resultant negative SPI over the Korean Peninsula in 2014, 2015, and 2017. The large-ensemble simulation supported the observational findings that the composited SST anomalies during the 5 years of persistent drought exhibited prominent and persistent SST warming over the subtropical central Pacific, along with large-scale cyclonic flow over the North Pacific. The findings of this study imply that the SST anomalies over the North Pacific and subtropical central Pacific can be a predictable source to potentially increase the ability to forecast multiyear droughts over the Korean Peninsula.
In the Congo Basin, a drying trend in the April–May–June rains prevailed between 1979 and 2014, accompanied by a decline in forest productivity. This article examines the subsequent years, in order to determine whether rainfall conditions have improved and to examine meteorological factors governing conditions in those years. It is shown that a wetter period, comparable to that of 1979–1993, spanned the years 2016–2020. However, the meteorological factors responsible for the wetter conditions appear to be significantly different from those related to the earlier wet period. The wetter conditions of 1979–1993 were associated with changes in the tropical Walker circulation, in moisture flux and flux divergence, and in Pacific sea-surface temperatures (SST), namely a warmer central and eastern Pacific and a cooler western Pacific, compared to the dry phase in 2000–2014. This resulted in a lower-than-average trans-Pacific SST gradient. In contrast, SSTs were almost ubiquitously higher in the 2016–2020 period than in either prior period. However, there was some reduction in the trans-Pacific gradient. The Walker circulation and moisture flux/flux divergence were not factors in this episode. The major factors provoking the return to wetter years appear to be an increase in convective available potential energy and in total column water vapor. This could be related to the general warming of the oceans and land.
more » « less- Award ID(s):
- 1850661
- PAR ID:
- 10367249
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Environmental Research Letters
- Volume:
- 17
- Issue:
- 5
- ISSN:
- 1748-9326
- Page Range / eLocation ID:
- Article No. 054052
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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