Multi‐decadal variability of soil moisture–temperature coupling over the contiguous United States modulated by Pacific and Atlantic sea surface temperatures

Abstract

Regions of strong land–atmosphere coupling are often depicted as static in time. However, the mechanisms through which the land surface impacts atmospheric conditions vary on sub‐daily to multi‐decadal timescales. Therefore, characterizing the long‐term variability of land–atmosphere interactions may provide a means of predicting when surface‐induced extreme temperature events will be more or less likely to occur. We evaluate the coupling strength between soil moisture, as represented by in situ observations and 1‐month Standardized Precipitation Index (SPI), and subsequent monthly maximum temperature (TMAX) over the contiguous United States. We find that the utility of SPI as a proxy for soil moisture anomalies is limited to the summer, as the correlations between SPI and TMAX are not significantly related in the other seasons. We examine the variability in summer SPI–TMAX coupling in four regions of the United States. In general, we find the strongest relationships between SPI and TMAX in the Southern Great Plains. However, our results demonstrate that the coupling strength varies considerably over time in most regions of the United States. The long‐term variability in SPI–TMAX coupling strength is strongly related to the Pacific Decadal Oscillation in the northwest and midwest United States, and the Atlantic Multidecadal Oscillation in the southeast United States The results of this study suggest that land–atmosphere coupling in the contiguous United States is modulated by multi‐decadal oscillations in Pacific and Atlantic sea surface temperatures.

Mechanisms of Seasonal Soil Moisture Drought Onset and Termination in the Southern Great Plains

“…Reductions in soil moisture can lead to reduced evapotranspiration, enhanced sensible and longwave radiative heat loss, reduced cloud cover and greater surface solar radiation which collectively lead to higher surface air temperatures. Over North America this land-atmosphere coupling is especially strong in the Great Plains and in the warm season (Koster et al 2004;Dong et al 2011;Ford et al 2017;Basara and Christian 2018) with spring soil moisture initial conditions offering the potential for limited predictability of subsequent summer precipitation (Meng and Quiring 2010a,b;Basara and Christian 2018). However, landatmosphere coupling can alter the evolution of drought but is unlikely to initiate or terminate drought.…”

Assessment of the impact of soil moisture on spring surface air temperature over the low‐latitude highlands of China

“…Furthermore, Orlowsky and Seneviratne (2010) as well as Sun and Wang (2012) demonstrated that SM‐precipitation coupling strength is strongly affected by remote SST forcing; Ford et al . (2017) also pointed out that SM‐SAT coupling in the United States is greatly related to the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation. These results suggest that the assessment of spring LLH SM‐SAT coupling in this study should be evaluated carefully.…”

Impact of Plant Functional Types on Coherence Between Precipitation and Soil Moisture: A Wavelet Analysis

“…Our research site is located in the ecotone between Great Plains grassland and eastern temperate forest, and the dominance of large‐scale climatic control on precipitation shifts from the Pacific Decadal Oscillation (PDO) to the Atlantic Multidecadal Oscillation (AMO) influence between these regions (Ford et al, ). This area is also highly influenced by the El Niño–Southern Oscillation, and our 6 year study captured strong interannual variability, including a moderate La Niña year (2011) and a very strong El Niño year (2015) (http://ggweather.com/enso/oni.htm).…”