Effects of Arctic stratospheric ozone changes on spring precipitation in the northwestern United States
2018
Abstract. Using observations and reanalysis, we find that changes in April
precipitation variations in the northwestern US are strongly linked to March
Arctic stratospheric ozone (ASO). An increase in ASO can result in enhanced
westerlies in the high and low latitudes of the North Pacific but weakened
westerlies in the midlatitudes. The anomalous circulation over the North
Pacific can extend eastward to western North America, decreasing the water
vapor concentration in the air over the northwestern United States and
enhancing downwelling in the northwestern US, which results in decreased
precipitation there and vice versa for the decrease in ASO. Model
simulations using the Whole Atmosphere Community Climate Model version 4 (WACCM4) support the statistical analysis of observations and
reanalysis data and further reveal that the ASO influences circulation
anomalies over the northwestern US in two ways. Stratospheric circulation
anomalies caused by the ASO changes can propagate downward to the troposphere
in the North Pacific and then eastward to influence the strength of the
circulation anomalies over the northwestern US. In addition, sea surface
temperature anomalies over the North Pacific, which may be related to the ASO
changes, would cooperate with the ASO changes to modify the circulation
anomalies over the northwestern US. Our results suggest that ASO variations
could be a useful predictor of spring precipitation changes in the
northwestern US.
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