Correlations Between Extreme Atmospheric Hazards and Global Teleconnections: Implications for Multihazard Resilience

Lee

Water Resources Research

et al. 2019

As drought involves diverse natural and human‐made processes in hydrologic cycles, it is necessary to track a process‐specific variable for efficient drought risk management. In this study, we employed a state‐of‐the‐art formulation of the generalized complementary relationship (GCR) to estimate terrestrial evapotranspiration (ET). The GCR ET estimates were used to assess historical droughts over the contiguous United States (CONUS) in relation to long‐term natural fluctuations. Results showed that the GCR provided strong performance in reproducing water balance ET estimates and correlations to the El Niño–Southern Oscillation, when compared to observation‐driven estimates and land surface models. For 1982‐2011, the GCR yielded better performance than land surface models even with estimated radiation inputs and no wind speed variations. The Standardized Evapotranspiration Deficit Index (SEDI) based on the GCR provided a consistent drought assessment with precipitation‐based drought identification and remotely sensed vegetation conditions. The SEDI seems to capture the heat wave‐driven flash drought together with water deficit‐driven droughts. In the CONUS, the La Niña‐like conditions were likely to trigger extensive vegetation droughts with extreme severity. This study found the three long‐term environmental factors that affect the general trend of ET deficits over the CONUS, which are the Atlantic Multidecadal Oscillation, the mean air temperature, and the Pacific Decadal Oscillation. Especially, the Atlantic Oscillation seems to be the most significant predictor that could explain the long‐term variation of vegetation droughts over the CONUS. This study highlights that the GCR‐based SEDI could be useful for monitoring and assessment of drought risks at a continental scale.

Section: Resultsmentioning

confidence: 99%

Historical Drought Assessment Over the Contiguous United States Using the Generalized Complementary Principle of Evapotranspiration

Lee

Water Resources Research

et al. 2019

Quart J Royal Meteoro Soc

“…Prolonged weather extremes result dynamically from long‐lived atmospheric flow patterns, whose duration spans from days to weeks (Higgins and Mo, ; Stadtherr et al., ; Mann et al., ; Kornhuber et al., ). Recurrent atmospheric teleconnections composed of adjacent cyclones/anticyclones are deemed one major source for the persistence of weather extremes (Chen and Zhai, ; Lü et al ., ; Steptoe et al., ). Monthly‐/seasonal‐scale indices of atmospheric teleconnections used to be employed in explaining, monitoring and predicting climate anomalies at interannual to inter‐decadal time‐scales (Wallace and Gutzler, ; Nitta and Hu, ; Kubota et al., ).…”

Section: Introductionmentioning

confidence: 97%

Persistent precipitation extremes in the Yangtze River Valley prolonged by opportune configuration among atmospheric teleconnections

Chen

Zhai

Liao

et al. 2019

This study investigates whether and how three synoptic-scale teleconnections, i.e. East Asia/Pacific teleconnection (EAP), Silk-Road teleconnection (SR) and Eurasia teleconnection (EU), induce persistent precipitation extremes (PPEs) in the Yangtze River Valley. Results show that only the EAP teleconnection has the potential of independently incurring PPEs; while the other two teleconnections' influences on PPEs need to be exerted via their liaison with the EAP pattern. Cases are accordingly grouped into two subsets, i.e. single EAP-PPEs and three teleconnection-PPEs. In both groups, the EAP teleconnection evolves following a similar pathway that poleward energy dispersion dynamically links a westward-extended subtropical high, a deepened midlatitude trough and the Okhotsk blocking. EAP-induced circulation anomalies enhance low-level convergences and upper-level divergences, convey exceptionally abundant moisture, and hence give birth to a quasi-stationary front leading to PPEs in the Yangtze River Valley. Despite similarities, PPEs last noticeably longer in the three-teleconnection context. The EU teleconnection-related downstream energy dispersion at higher latitudes favours both earlier establishment and latter decay of the Okhotsk blocking. Constructed meridional flows at mid-high latitudes continuously steer migratory disturbances southeastward into the EAP trough. The SR plays a bigger role during the latter half of PPE life span (3 days after onset) via stimulating new cyclonic disturbances that largely overlap with the EAP trough spatially. Moreover, EU-and SR-excited disturbances could effectively extract baroclinic and barotropic energy from local mean flows to replenish components of the EAP tripole pattern, which therefore survives longer and prolongs PPEs by several days. K E Y W O R D S monsoonal stationary front, persistent precipitation extremes, Rossby wave energy dispersion and conversion, synoptic-scale atmospheric teleconnections, thermodynamic-dynamic mechanisms Q J R Meteorol Soc. 2019;145:2603-2626. wileyonlinelibrary.com/journal/qj © 2019 Royal Meteorological Society 2603 2604 CHEN ET AL.

“…For PC2 also, the SSTa cluster over the tropical western Pacific and eastern Indian Oceans, around the Maritime continents and adjacent to northern Australia was significant. Existing literature indicated that the tropical Pacific's ENSO is a primary driver of global climate variability [18][19][20] , influencing several croplands across the world 10,21,22 ; but using different approach and datasets our analysis confirms that the tropical Pacific SST can explain two leading modes of world-wide wheat yield variability and beyond. This finding was further substantiated by another set of findings shown in Table S3 indicating that ENSO indices, peaking mostly in winter (December-January-February), associate best with PC1 variability, and to an opposite manner with PC2.…”

Section: Resultsmentioning

(Expert classified)

Larger-scale ocean-atmospheric patterns drive synergistic variability and world-wide volatility of wheat yields

Najafi

Pal

Khanbilvardi

2020

Sci Rep

Diagnosing potential predictability of global crop yields in the near term is of utmost importance for ensuring food supply and preventing socioeconomic consequences. previous studies suggest that a substantial proportion of global wheat yield variability depends on local climate and larger-scale oceanatmospheric patterns. the science is however at its infancy to address whether synergistic variability and volatility (major departure from the normal) of multinational crop yields can be potentially predicted by larger-scale climate drivers. Here, using observed data on wheat yields for 85 producing countries and climate variability from 1961-2013, we diagnose that wheat yields vary synergistically across key producing nations and can also be concurrently volatile, as a function of shared larger-scale climate drivers. We use a statistical approach called robust Principal Component Analysis (rPCA), to decouple and quantify the leading modes (pc) of global wheat yield variability where the top four PCs explain nearly 33% of the total variance. Diagnostics of PC1 indicate previous year's local Air Temperature variability being the primary influence and the tropical Pacific Ocean being the most dominating larger-scale climate stimulus. Results also demonstrate that worldwide yield volatility has become more common in the current most decades, associating with warmer northern Pacific and Atlantic oceans, leading mostly to global supply shortages. As the world warms and extreme weather events become more common, this diagnostic analysis provides convincing evidence that concurrent variability and worldwide volatility of wheat yields can potentially be predicted, which has major socioeconomic and commercial importance at the global scale, underscoring the urgency of common options in managing climate risk. Wheat accounts for around 20% of the calories that humans consume and as such is the leading source of plant protein. It is well-known that wheat productivity is sensitive to both natural climate variability and extreme weather 1-10. As a result, extreme weather disasters such as heatwaves, droughts, floods, cold spells, and the co-occurrence of compound extremes (e.g. hot and dry spell events) have caused significant production losses 11-14. The relationships between climate, wheat production variability and stability, and socioeconomic outcomes has received growing attention recently 7,10,14-17. Separate lines of evidence indicate that weather extremes across the globe can occur concurrently, due to mutual larger-scale climate drivers 18-20 , and that such larger-scale drivers influence global and regional crop productivity 7,10,21-29. While agricultural influence of climate is well-established 1-17,21-29 , a detailed account of the characteristics of synergistic multinational variability and worldwide volatility of crop yields, whereby many countries undergo harmonizing influences of climate to thwart or facilitate wheat productivity, needs more attension 10. History indicates that such synchronous volatility-led whe...