Crucial role of Black Sea warming in amplifying the 2012 Krymsk precipitation extreme

Abstract

Over the past 60 years, both average daily precipitation intensity and extreme precipitation have increased in many regions 1-3 . Part of these changes, or even individual events 4,5 , have been attributed to anthropogenic warming 6,7 . Over the Black Sea and Mediterranean region, the potential for extreme summertime convective precipitation has grown 8 alongside substantial sea surface temperature increase. A particularly devastating convective event experienced in that region was the July 2012 precipitation extreme near the Black Sea town of Krymsk 9 . Here we study the e ect of sea surface temperature (SST) increase on convective extremes within the region, taking the Krymsk event as a showcase example. We carry out ensemble sensitivity simulations with a convection-permitting atmospheric model and show the crucial role of SST increase in the extremeness of the event. The enhancement of lower tropospheric instability due to the current warmer Black Sea allows deep convection to be triggered, increasing simulated precipitation by more than 300% relative to simulations with SSTs characteristic of the early 1980s. A highly nonlinear precipitation response to incremental SST increase suggests that the Black Sea has exceeded a regional threshold for the intensification of convective extremes. The physical mechanism we identify indicates that Black Sea and Mediterranean coastal regions may face abrupt amplifications of convective precipitation under continued SST increase, and illustrates the limitations of thermodynamical bounds for estimating the temperature scaling of convective extremes.Extreme precipitation responds sensitively to both dynamical and thermodynamical forcings 10-12 . Changes in precipitation extremes can occur owing to changes in evaporation, the increased saturation vapour pressure in a warmer climate 13 , and changes in storm dynamics 12 . Global climate models project increased heavy precipitation, mainly over the tropics and high latitudes 14,15 . As temperature increases, large-scale precipitation extremes tend to scale at about 7% K −1 , along the thermodynamical bounds given by the Clausius-Clapeyron (CC) relation 3 . Convective extremes, however, are strongly influenced by mesoscale dynamics and may scale well above the CC rate 10,11 . Local factors, such as orography and moisture availability, can also impact the convective response to temperature increase.The Krymsk precipitation extreme saw a daily precipitation total that exceeded all previous annual daily maxima since 1936 by a factor of two (Fig. 1a), and a flash flood that killed over 170 people 9 . On the basis of statistical evidence from the pre-2012 record,

Sensitivity of Midlatitude Heavy Precipitation to SST: A Case Study in the Sea of Japan Area on 9 August 2013

“…As clearly evident in Figure b, the change in response to the SST is mainly of dynamic origin. The importance of the dynamical contribution for precipitation changes in response to rising SST has been pointed out by Berthou et al (, ) and Meredith et al (), unlike in many of the global warming studies (e.g., Emori & Brown, ).…”

Investigating Relationships Between Australian Flooding and Large‐Scale Climate Indices and Possible Mechanism

“…This indicates that variation of flood across Australia is closely connected to the climate system and the climate indices have a remarkable impact on the variation FMF through their effects on atmospheric circulation. The change of SST has played a key role to the variation of extreme precipitation and floods events (Gu et al, ; Liu et al, ; Meredith et al, ; Zhang et al, ). However, generating floods are determined by multiple factors such as rainfall intensity, antecedent soil moisture, catchment area, catchment soil properties, and catchment slope.…”

Attribution of extreme weather

“…1). Writing in Nature Geoscience, Meredith et al 1 now show that -exceptionally for such a localized event -it is possible to attribute this flood to climate change: they present convectionresolving simulations that suggest that incremental warming of sea surface temperature (SST) in the Black Sea over the past few decades has led to an abrupt amplification of convective precipitation.…”