Using High-Resolution Reanalysis Data to Explore Localized Western North America Hydroclimate Relationships with ENSO

Abstract

Many studies have used observational data to explore associations between El Niño–Southern Oscillation (ENSO) and western North America (NA) hydroclimate at regional spatial scales. However, relationships between tropical Pacific sea surface temperature (SST) variability and western NA hydroclimate at local scales using reanalysis data are less understood. Here, the current understanding of relationships between large-scale tropical Pacific SST variability and western NA hydroclimate is extended to localized headwaters. To accomplish this, high-resolution reanalysis data (i.e., monthly mean surface precipitation rate, 2-m temperature, 850-mb specific humidity, and 500-mb omega) were used for gridpoint correlation analyses with Niño-3.4 SST and El Niño Modoki indices. Reanalysis time series data were provided by the National Centers for Environmental Prediction North American Regional Reanalysis (NARR) product. To validate the accuracy of NARR surface data, observational Livneh precipitation and temperature data were used. Resulting correlations between tropical Pacific indices and NARR surface precipitation and 2-m temperature are consistent with previous research both spatially and temporally, indicating that the strongest correlations occur primarily over southwestern NA during the winter (DJF). The results herein demonstrate the potential of high-resolution reanalysis data to reveal distinct correlations over topographically complex watersheds in the U.S. Intermountain West (IMW) over the recent record, 1979–2015. The use of the high-resolution NARR product as a viable option to explore western NA hydroclimate is demonstrated here.

Filling a Geographical Gap: New Paleoecological Reconstructions From the Desert Southwest, USA

“…We assess pollen preservation in ciénega systems of southwestern New Mexico and southeastern Arizona as well as the relationship to past ENSO variability based on our modern understanding of ENSO and southwestern North American hydroclimate teleconnections (Heyer et al, 2017). Further, we put forward past fire activity near the ciénegas was covariant with ENSO variability, similar to connections observed in historic southwestern forest fire research (Swetnam and Betancourt, 1990).…”

“…Therefore, correlation analyses from 8,100 to 5,400 cal yr BP is not based on an actual average. However, we assume a lack of pollen preservation and charcoal accumulation at the inactive ciénega sites was due to a lack groundwater recharge, which may represent a reduction of persistent winter and spring precipitation potentially associated with reduced El Niño events (Scanlon et al, 2006;Heyer et al, 2017). We suggest if the other three ciénega sites had been active, then pollen preservation and charcoal accumulation would have been close to zero, similar to the San Bernardino ciénega.…”

“…Studies have identified a northto-south precipitation dipole correlated with ENSO in the western U.S., showing a strong relationship in the southwest between cool season (Oct-Mar) precipitation and El Niño events (Dettinger et al, 1998;Wise, 2010). Further, many studies have shown statistically significant correlations between ENSO and western North America precipitation, specifically in the southwest where spatially coherent correlations are found during the cool season (Dettinger et al, 1998;Heyer et al, 2017). However, various modes of ENSO are associated with different impacts on western NA hydroclimate (Ashok et al, 2007), and teleconnections can vary on decadal-to-centennial time scales (Gershunov and Barnett, 1998b), suggesting that southwest hydroclimate does not always respond to ENSO variability in a linear manner based on our modern understanding of southwest hydroclimate and ENSO correlations (Heyer et al, 2017).…”

“…Further, many studies have shown statistically significant correlations between ENSO and western North America precipitation, specifically in the southwest where spatially coherent correlations are found during the cool season (Dettinger et al, 1998;Heyer et al, 2017). However, various modes of ENSO are associated with different impacts on western NA hydroclimate (Ashok et al, 2007), and teleconnections can vary on decadal-to-centennial time scales (Gershunov and Barnett, 1998b), suggesting that southwest hydroclimate does not always respond to ENSO variability in a linear manner based on our modern understanding of southwest hydroclimate and ENSO correlations (Heyer et al, 2017). However, despite teleconnection variability (Gershunov and Barnett, 1998b), dipole variability (Wise, 2010) and different modes of ENSO (Ashok et al, 2007), paleo-sedimentary records suggest teleconnections between ENSO and southwest climate are similar to those observed in the modern record, and have persisted at century-millennial time scales (Barron and Anderson, 2010;Antinao and McDonald, 2013;Kirby et al, 2014;Hart et al, 2015).…”

“…Our work has been focused on ciénegas near the US/Mexico borderlands region in southern Arizona and New Mexico (Figure 1) in the monsoon-dominated ecotone of the Sonoran and Chihuahuan deserts and in a region well correlated with ENSO activity (Wise, 2010;Heyer et al, 2017). Total annual precipitation is around 254 mm (Western Regional Climate Center, 2017).…”