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Two Large-Scale Meteorological Patterns are Associated with Short-Duration Dry Spells in the Northeastern United States

Presentation Date
Friday, December 16, 2022 at 2:45pm - Friday, December 16, 2022 at 6:15pm
McCormick Place - Poster Hall, Hall - A



We investigate the top ~14% longest dry spell events over the northeastern United States. These top ~14% longest dry spell events are identified as consecutive dry day (CDD) events lasting nine days or longer. The 500-hPa stream function anomaly fields for the first nine days of each dry spell event are time-averaged, and input to a k-means clustering algorithm in order to determine the dry spell-related large-scale meteorological patterns (LSMPs). Events are grouped into two types (clusters) based on the temporal and spatial evolution of the LSMPs during the onset period of the events. In this presentation, we will show that the first cluster is associated with a strong, low-pressure area in the midlatitude Atlantic Ocean, while the second cluster is defined by a strong, high-pressure area centered over east-central North America. The development of both LSMPs is consistent with wave activity flux (WAF) across northern North America. Both LSMPs are associated with negative specific humidity anomalies, changes to vapor transport, and subsidence associated with a dipole structure in the midlatitude jet stream that generates upper-level convergence. Cold air advection into the region provides additional support for subsidence in the first cluster, while subsidence is reinforced from the high-pressure region in the second cluster. Extratropical cyclone storm track density in this region is shown to be reduced during the dry spell events, and the two dry spell LSMPs hint at some remote associations with several large-scale modes of climate variability. This analysis provides important insight into the large-scale conditions that can facilitate short-duration dry spell events in the northeastern United States. And as model simulations indicate a future increase in the frequency of these types of events, our results can serve as an important foundation for validating models’ representation of these dry spell LSMPs in our current climate and in future climate scenarios.

Funding Program Area(s)
Additional Resources:
NERSC (National Energy Research Scientific Computing Center)