A numerical modeling study to investigate the assumptions used in the calculation of probable maximum precipitation

Abstract

Abstract. A numerical model of the atmosphere has been employed to evaluate the assumptions used in the simple two-parameter model that is utilized for many probable maximum precipitation (PMP) calculations. These assumptions are (1) the precipitation is linearly related to the precipitable water; (2) the precipitation efficiency of the storm does not change as the moisture available to the storm increases; and (3) terrain modulates the distribution of the precipitation but does not affect the synoptic-scale dynamics of the storm. A single case study is used to illustrate the techniques employed and to describe the results that were common to four case studies. We show that long-lived, moderate rainfall processes are important contributors to the total precipitation produced by the storm. Increases in the moisture availability result in the heavy rainfall beginning earlier, lasting longer, and being more continuous. As the moisture availability changes, the spatial distribution of the area over which more than 50% of the total rainfall falls as heavy rainfall changes. As the moisture availability is increased, the precipitation efficiency of the storm does not change significantly. Terrain effects are shown to have an effect on the amount of rainfall that occurs over the higher terrain as well as on the distribution of the rainfall due to the "convergence component" of the storm. Despite these deficiencies in the assumptions used to estimate PMP, improvements in the estimation of PMP may soon be possible if increased effort is placed on (amongst other things) the numerical modeling of extreme rainfall events. These improvements are only possible if the results of these efforts are communicated to the hydrological community.

Super‐Clausius–Clapeyron scaling of rainfall in a model squall line

“…However, for the sub-12-hour time-scales under consideration here, the storm model approach was shown to estimate similar PMP values to those of the simple CC scaling method. Our work strongly suggests that current methodologies are likely to lead to underestimates of PMP as was first suggested by a lower-resolution model study (Abbs, 1999). A conservative revision of PMP estimates assuming up to twice CC scaling for sub-daily rainfall point and catchment totals should be considered.…”

The impact of satellite-derived wind data assimilation on track, intensity and structure of tropical cyclones over the North Indian Ocean

“…It is mainly due to lack of sufficient resolution, less data availability for assimilation and lack of representation of land surface processes (Niyogi et al 2006, Chang et al 2009). Further, better organization of mesoscale and large-scale moisture convergence (Abbs 1999) can improve precipitation forecast, which may be obtained with the assimilation of moisture fields, which leads to better organization of mesoscale and large-scale moisture convergence.…”

Estimating Probable Maximum Precipitation by Considering Combined Effect of Typhoon and Southwesterly Air Flow

“…The concept of each method can be categorized simply as either statistical methods or hydrometeorological methods (Rakhecha and Kennedy 1985;Abbs 1999;Douglas and Barros 2003;Chen and Bradley 2007;Fernando and Wickramasuriya 2011;Casas et al 2011). PMP estimation method using numerical weather models have also been developed in recent years (Tan 2010;Yigzaw et al 2013;Ishida et al 2015).…”