Northeast United States growing season moisture conditions: Associations with a North American mid‐tropospheric wave train

Abstract

The Palmer Drought Severity Index is examined in the Northeast United States during the May–September growing seasons of 1950–2016, seeking to better understand the role of atmospheric circulation in moisture variability. Moist conditions for the Northeast are associated with the development of a mid‐tropospheric wave train over the United States, with enhanced ridging over the west, a trough over the Ohio Valley, and ridging over the Atlantic Ocean east of Newfoundland that favours enhanced uplift, precipitation, and southeasterly flow at the surface in the Northeast. A scalar representation of the wave train, a Summer Atmospheric Drought Index (SADI), is developed and robustly validated as a strong indicator of the Northeast moisture conditions. The SADI mid‐tropospheric wave train is the second largest mode of 500 hPa height variability over the North American sector from 1950–2016, and has an increasing trend such that the ridge‐trough‐ridge pattern is more prevalent and/or has become more enhanced with time. The wave train pattern has a significant and positive relationship to the phases of the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO). This indicates that when the AO and NAO indices are positive, the wave train pattern favours the ridge‐trough‐ridge configuration over North America, and can lead to moist conditions in the Northeast. The opposite pathway is also valid and can lead to dry conditions in the Northeast. This pathway provides a physical link between Northeast moisture conditions and global‐scale variability, improving the understanding of atmospheric influences on regional drought and excessive moisture conditions.

Groundwater recharge in northern New England: Meteorological drivers and relations with low streamflow

“…At many wells, the May NAO was negatively correlated with groundwater recharge in both current RY and subsequent fall recharge seasons, indicating that a negative phase of the NAO would lead to increased groundwater recharge (Figures 3 and 5). Previous literature has found that negative NAO conditions are associated with meridional flow, increased blocking, colder temperatures, and an eastward displaced trough axis which would allow coastal storms to track almost directly east away from the Atlantic coast, contributing to reduced precipitation totals across the Northeast (Archambault et al, 2008; Bradbury, Dingman, et al, 2002; Bradbury, Keim, et al, 2002; Shabbar et al, 2001; Suriano et al, 2018; Yarnal & Leathers, 1988). The negative correlation found between RY and fall recharge with May's NAO index does not support findings in previous literature.…”

“…This result is despite the potential importance of summer air temperature to summer/fall minimum flows through evapotranspiration. Additionally, studies that considered meteorological drivers of drought conditions across the Northeast have found that precipitation was a much stronger control on drought conditions than temperature or evapotranspiration (Ficklin et al, 2015; Leathers et al, 2000; Suriano et al, 2018). The effects of climate change could reduce groundwater recharge if increases in temperature and evapotranspiration exceed expected increases in precipitation in NNE (Bjerklie et al, 2011), but based on the historical data used in our study, groundwater recharge to date is strongly related to precipitation and not temperature.…”

“…Teleconnection patterns are generally made up of two to four “centers of action” that link climate effects of geographically separated regions across the globe (Barnston & Livezey, 1987). Previous studies have documented the influence of teleconnections on the persistence of upper level, trough‐ridge patterns at the 500 and 300 mb levels on the regional distribution of surface precipitation events and air temperature (Leathers et al, 2000; Suriano et al, 2018). Across the Northeast, teleconnections that have been found to control drought conditions include the North Atlantic Oscillation (NAO; Walker & Bliss, 1932), Arctic Oscillation (AO; Thompson & Wallace, 1998), Pacific North‐American (PNA; Lorenz, 1951), and El‐Niño–Southern Oscillation (ENSO; Bjerknes, 1969).…”

“…Well Depth is the depth of the well in metres. HCDN-2009 Streamgage is the paired streamgage denoted by USGS station number and classified as part of the Hydro-Climatic Data Network, version 2009(HCDN-2009 levels on the regional distribution of surface precipitation events and air temperature (Leathers et al, 2000;Suriano et al, 2018) (Konapala & Mishra, 2020).…”

Effects of Atmospheric Circulation on Stream Chemistry in Forested Watersheds Across the Northeastern United States: Part 2. Interannual Weather Type Variability

“…In all cases, synoptic classification efficiently isolates similarly occurring atmospheric conditions as individual synoptic weather types, aiding researchers in determining the impact each weather type has on the topic of interest (Yarnal, 1993). These techniques are also advantageous in their ability to serve as a method to connect scales, linking global‐scale processes to local‐scale phenomena (Suriano et al., 2018). Connecting scales allow for a pathway of physical forcing mechanisms to be established, furthering the scientific understanding of the climate system.…”