Understanding Convective Extreme Precipitation Scaling Using Observations and an Entraining Plume Model

Abstract

Previously observed twice-Clausius-Clapeyron (2CC) scaling for extreme precipitation at hourly time scales has led to discussions about its origin. The robustness of this scaling is assessed by analyzing a subhourly dataset of 10-min resolution over the Netherlands. The results confirm the validity of the previously found 2CC scaling for extreme convective precipitation.Using a simple entraining plume model, an idealized deep convective environmental temperature profile is perturbed to analyze extreme precipitation scaling from a frequently used relation based on the column condensation rate. The plume model simulates a steady precipitation increase that is greater than ClausiusClapeyron scaling (super-CC scaling). Precipitation intensity increase is shown to be controlled by a flux of moisture through the cloud base and in-cloud lateral moisture convergence. Decomposition of this scaling relation into a dominant thermodynamic and additional dynamic component allows for better understanding of the scaling and demonstrates the importance of vertical velocity in both dynamic and thermodynamic scaling. Furthermore, systematically increasing the environmental stability by adjusting the temperature perturbations from constant to moist adiabatic increase reveals a dependence of the scaling on the change in environmental stability. As the perturbations become increasingly close to moist adiabatic, the scaling found by the entraining plume model decreases to CC scaling. Thus, atmospheric stability changes, which are expected to be dependent on the latitude, may well play a key role in the behavior of precipitation extremes in the future climate.

Scaling precipitation extremes with temperature in the Mediterranean: past climate assessment and projection in anthropogenic scenarios

“…This super-CC scaling was interpreted as resulting from a shift in rain type by Haerter and Berg (2009), and Berg and Haerter (2013), though the first reference is a hypothesis, whereas the second only discusses a small number of stations. Berg et al (2013) and Loriaux et al (2013) found with smaller statistical effect a super-CC scaling with convective precipitation only, the latter showing an important role of the vertical velocity for super-CC behavior. and from the HyMeX/MED-CORDEX simulations at the nearest grid point.…”

Future extreme precipitation intensities based on historic events

“…up to 14% per degree of warming (Lenderink & Van Meijgaard, 2008;Sugiyama et al, 2010;Panthou et al, 2014;Attema et al, 5 2014;Allan, 2011;Berg et al, 2013). The exceedance of the CC scaling for extreme precipitation is suggested to be related to the large and small-scale dynamics of the atmosphere, and to the vertical stability (Loriaux et al, 2013;Lenderink & Attema 2015). Other studies indicate that statistical factors account for temperature-related changes in precipitation types, with an increasing contribution of convective warmer rain as temperature rises (Haerter & Berg, 2009).…”

Sensitivity of historical orographically enhanced extreme precipitation events to idealized temperature perturbations

“…The Clausius-Clapeyron (CC) relation is often used as a rule of thumb on how extreme precipitation may change in a warmer climate (e.g. Allan and Ingram 2002;Trenberth et al 2003;Pall et al 2006;Loriaux et al 2013). By using a simple numerical model for idealized extreme storms, Siler and Roe (2014) found that orographic precipitation had a lower response to surface warming than expected by the CC-relation.…”