The Robust Relationship Between Extreme Precipitation and Convective Organization in Idealized Numerical Modeling Simulations

Abstract

The behavior of tropical extreme precipitation under changes in sea surface temperatures (SSTs) is investigated with the Weather Research and Forecasting Model (WRF) in three sets of idealized simulations: small‐domain tropical radiative‐convective equilibrium (RCE), quasi‐global “aquapatch”, and RCE with prescribed mean ascent from the tropical band in the aquapatch. We find that, across the variations introduced including SST, large‐scale circulation, domain size, horizontal resolution, and convective parameterization, the change in the degree of convective organization emerges as a robust mechanism affecting extreme precipitation. Higher ratios of change in extreme precipitation to change in mean surface water vapor are associated with increases in the degree of organization, while lower ratios correspond to decreases in the degree of organization. The spread of such changes is much larger in RCE than aquapatch tropics, suggesting that small RCE domains may be unreliable for assessing the temperature‐dependence of extreme precipitation or convective organization. When the degree of organization does not change, simulated extreme precipitation scales with surface water vapor. This slightly exceeds Clausius‐Clapeyron (CC) scaling, because the near‐surface air warms 10–25% faster than the SST in all experiments. Also for simulations analyzed here with convective parameterizations, there is an increasing trend of organization with SST.

A wavelet‐based analysis of convective organization in ICON large‐eddy simulations

“…The general tendencies with increased SCAI for weak organization on 15 August 2014 and larger values of I org and COP for strong organization on 04 and 05 July 2015 are in agreement with results of Tobin et al (2012), Tompkins and Semie (2017), Bao et al (2017), Holloway (2017), Cronin and Wing (2017), Wing et al (2018), and White et al (2018). Although convective organization is reflected in the indices, SCAI is strongly dominated by the number of clusters, whereas I org is very noisy and hard to interpret if the number of clusters is small.…”

“…(), Tompkins and Semie (), Bao et al. (), Holloway (), Cronin and Wing (), Wing et al. (), and White et al.…”

“…Other studies (e.g. Bao et al, 2017;Holloway, 2017) distinguish between convective and non-convective grid points on the basis of precipitation.…”

Estimation of extreme daily precipitation thermodynamic scaling using gridded satellite precipitation products over tropical land

“…Indeed, these observations are by essence mainly concentrated over data rich areas of the globe, leaving an unsatisfactory appraisal of the evolution of intense rainfall over conventional data poor regions like the tropical land regions (Becker et al 2013, Kidd et al 2017, Taylor et al 2017. The lack of data yields to a series of non-robust results about the scaling of daily extreme precipitation to temperature in the tropics (Utsumi et al 2011, Eiji et al 2012, Vittal et al 2016, Bao et al 2017, Barbero et al 2017, Wang et al 2017, Ali and Fowler 2018. A large number of multisource gridded precipitation products, including multiple satellites observations and microwave constellation-based products, has emerged in the recent decade (Levizzani et al 2018) that could help to alleviate this regional gap and clarify the observational relationship between precipitation extremes and surface temperature in the tropics.…”

Comments on “temperature‐extreme precipitation scaling: A two‐way causality?”

“…First, dew point temperature is a measure of humidity, thus this scaling relationship using dew point provides less insight about how extreme precipitation would behave under climate change. Second, near‐surface thermodynamic properties alone do not control extreme precipitation, which is also sensitive to upper‐air temperature and humidity as well as mesoscale organization (Bao et al, ). Because dew point and these other factors are simultaneously influenced by synoptic flow changes, the binning method yields results that do not reflect the influence of dew point alone.…”