RAL SEMINAR: The Changing Hydroclimate of New England and Impacts on Warm Season Drought
1:00 – 2:00 pm MDT
Jeffrey Basara
Dr. Basara is a Professor and serves as Chair of the Department of Environmental, Earth, and Atmospheric Sciences at the University of Massachusetts Lowell (UML). He is deeply passionate about teaching and mentorship with the goal to provide outstanding instruction and meaningful educational experiences that empower students to become future leaders and difference makers in the environmental sciences. Dr. Basara’s research is focused on the complex, integrated processes across weather, climate, water, and ecosystems with specific attention directed toward precipitation extremes and associated impacts. This includes droughts, flash droughts, flash floods, and pluvial periods, along with the evolution of the planetary boundary layer, surface-atmosphere exchange, urban-atmosphere interactions, and severe and extreme weather such as heat waves, cold air outbreaks, and cascading events. He is a Kavli Fellow of the United States National Academy of Sciences and has received multiple research awards including the Research, Education, and Economics (REE) Under Secretary’s Award in 2019 from the USDA.
Drought is changing in the northeast United States (NEUS). Although the region normally receives 10 cm of liquid precipitation each month, the past decade has shown a notable change in the climatological record including three rapidly developing warm season droughts in 2016, 2020, and 2022. To examine this shift and better understand drought dynamics in the NEUS, multiple datasets were used, including PRISM (precipitation and temperature), ERA5-Land reanalysis (potential evapotranspiration), Harvard Forest Flux Tower observations (latent heat fluxes and net radiation), United States Geological Survey (USGS) National Water Information System (NWIS) streamflow data, and satellite remote sensing observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) to evaluate vegetation responses (Land Surface Water Index; LSWI). Analysis of PRISM data reveals that the 2016, 2020, and 2022 events in New England were statistically significance when compared to the climatological record. Key characteristics of these events include anomalously high temperatures, precipitation deficits, low streamflow, and elevated atmospheric demand as indicated by increased potential evapotranspiration and net radiation. Despite these conditions, observations from the Harvard Forest EMS Flux Tower (HFR1) show that latent heat fluxes during each event remained near or above climatological norms, yielding enhanced evapotranspiration (ET). This is supported by LSWI data, which shows enhanced greening in some areas despite persistent drought conditions reported by the United States Drought Monitor (USDM), precipitation deficits, and increased atmospheric demand. As such, drought impacts were first identified in the streamflow, rather than the vegetation, as values quickly dropped below the 40th percentile from April to May, with the average of gauges in each state remaining below this threshold for the duration of the event, and below the 20th percentile in most states throughout the summer. This physical response, consistent amongst the three events, points to complex land-atmosphere interactions driven by atmospheric demand and greater reliance on groundwater use as overall drought stress increases during flash drought in the northeast United States.