Response of Extreme Precipitating Cell Structures to Atmospheric Warming

Abstract

With increasing temperatures, it is likely that precipitation extremes increase as well. While, on larger spatial and longer temporal scales, the amplification of rainfall extremes often follows the Clausius‐Clapeyron relation, it has been shown that local short‐term convective precipitation extremes may well exceed the Clausius‐Clapeyron rate of around 6.5%/K. Most studies on this topic have focused exclusively on the intensity aspect, while only few have examined (with contradictory results) how warmer and moister conditions modulate the spatial characteristics of convective precipitation extremes and how these connect to increased intensities. Here we study this relation by using a large eddy simulation model. We simulate one diurnal cycle of heavy convective precipitation activity based on a realistic observation‐based strongly forced case setup. Systematically perturbed initial conditions of temperature and specific humidity enable an examination of the response of intensities and spatial characteristics of the precipitation field over an 8° dew point temperature range. We find that warmer and moister conditions result in an overall increase of both intensities and spatial extent of individual rain cells. Colder conditions favor the development of many but smaller rain cells. Under warmer conditions, we find a reduced number of individual cells, but their size significantly grows along with an increase of intensities over a large part of a rain cell. Combined, these factors lead to larger and more intense rain cells that can produce up to almost 20% more rain per degree warming and therefore have a large impact.

Kilometer-scale modeling projects a tripling of Alaskan convective storms in future climate

“…Our results differ from those reported in similar studies conducted in the mid-latitudes, that show only a small increase (Prein et al 2017b) or even a decrease (Dai et al 2017) in the number of convective systems, for regional convection-permitting simulations (Dai et al 2017) or idealized large-eddy simulations (Lochbihler et al 2019). In the mid-latitudes, more intense storms consuming more moisture, combined with limited moisture availability, are expected to result in fewer but more intense storms Dai et al (2017); Fitzpatrick et al (2020).…”

Diurnal Self-Aggregation

“…20 Mechanistically, cold pools (CPs), that is, denser air formed by rain evaporation under thunderstorm clouds, were long implicated in the organisation of convection, 21,22 both by thermodynamic and mechanical effects, [23][24][25][26][27] and were suggested to lead to clustering. 28,29 CPs can be long-lived when they arise in MCSs. Over ocean, Chen and Houze (1997) observed MCSs to undergo bidiurnal oscillations of local cloudiness and referred to this dynamics as "diurnal dancing."…”

Shift Toward Intense and Widespread Precipitation Events Over the United States by Mid‐21st Century

“…Such an increase in atmospheric moisture with warming can also impact the spatial extent of precipitation events. However, research efforts that focus on this aspect of precipitation storm characteristics are relatively limited as only a few studies thus far have investigated the spatial characteristics of mean and extreme precipitation in observations (Hamada et al, 2014; Kunkel et al, 2012; Lochbihler et al, 2017; Touma et al, 2018, 2019; Wasko et al, 2016) and model simulations (Benestad, 2018; Chang et al, 2016; Guinard et al, 2015; Li et al, 2018; Lochbihler et al, 2019; Prein et al, 2017). Moreover, modeling studies that investigate changes in the spatial characteristics of precipitation in future climates vary in their conclusions, which partly stems from their methodological (e.g., type size and scale of events, detection algorithm) and modeling differences.…”

“…For instance, a few studies suggest that future warming may lead to intense but localized precipitation events (e.g., Benestad, 2018; Shi & Durran, 2016); however, these conclusions are based on broad‐scale aggregate analyses. On the other hand, studies that project an increase in the intensity as well as the spatial extent of precipitation events are either based on idealized simulations or are focused on specifc type of precipitation events (e.g., Lochbihler et al, 2019; Prein et al, 2017). Furthermore, some studies are based on relatively coarse‐resolution models (Guinard et al, 2015; Hamada et al, 2014) or short‐duration numerical experiments (Chang et al, 2016), which can potentially underrepresent the fine‐scale response of precipitation events due to coarser grid spacing or lack the representation of their robust behavior due to limited length of climate change experiments.…”