Previous studies suggested that fast‐decay El Niño events are more favorable in generating the western North Pacific anticyclone (WNPAC) in the decaying summer. However, we found that this is not the case for all fast‐decay El Niño events. By comparing two groups of fast‐decay El Niño events with significant and insignificant WNPAC in the following summer, we found that the westward extension of the equatorial Pacific cold sea surface temperature anomalies (SSTA) and the subtropical central‐north Pacific cold SSTA play important roles in the generation and intensification of the WNPAC during decaying summer. Further analyses indicated that the internal atmospheric mode—North Pacific Oscillation during boreal spring can affect the formation of the cold SSTA over the subtropical central‐north Pacific and the westward extension of the equatorial Pacific cold SSTA during summer. Additional effects of tropical Indian and Atlantic forcing on the maintenance of the WNPAC are also shown.
Summertime heavy rainfall and its resultant floods are among the most harmful natural hazards in the US Midwest, one of the world's primary crop production areas. However, seasonal forecasts of heavy rain, currently based on preseason sea surface temperature anomalies (SSTAs), remain unsatisfactory. Here, we present evidence that sea surface salinity anomalies (SSSAs) over the tropical western Pacific and subtropical North Atlantic are skillful predictors of summer time heavy rainfall one season ahead. A one standard deviation change in tropical western Pacific SSSA is associated with a 1.8 mm day−1increase in local precipitation, which excites a teleconnection pattern to extratropical North Pacific. Via extratropical air‐sea interaction and long memory of midlatitude SSTA, a wave train favorable for US Midwest heavy rain is induced. Combined with soil moisture feedbacks bridging the springtime North Atlantic salinity, the SSSA‐based statistical prediction model improves Midwest heavy rainfall forecasts by 92%, complementing existing SSTA‐based frameworks.
more » « less- Award ID(s):
- 1663704
- NSF-PAR ID:
- 10370192
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 49
- Issue:
- 13
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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