The sensitivity of oceanic precipitation to sea surface temperature

Abstract

Abstract. Our study forms the oceanic counterpart to numerous observational studies over land concerning the sensitivity of extreme precipitation to a change in air temperature. We explore the sensitivity of oceanic precipitation to changing sea surface temperature (SST) by exploiting two novel datasets at high resolution. First, we use the Ocean Rainfall And Ice-phase precipitation measurement Network (OceanRAIN) as an observational along-track shipboard dataset at 1 min resolution. Second, we exploit the most recent European Reanalysis version 5 (ERA5) at hourly resolution on a 31 km grid. Matched with each other, ERA5 vertical velocity allows the constraint of the OceanRAIN precipitation. Despite the inhomogeneous sampling along ship tracks, OceanRAIN agrees with ERA5 on the average latitudinal distribution of precipitation with fairly good seasonal sampling. However, the 99th percentile of OceanRAIN precipitation follows a super Clausius–Clapeyron scaling with a SST that exceeds 8.5 % K−1 while ERA5 precipitation scales with 4.5 % K−1. The sensitivity decreases towards lower precipitation percentiles, while OceanRAIN keeps an almost constant offset to ERA5 due to higher spatial resolution and temporal sampling. Unlike over land, we find no evidence for a decreasing precipitation event duration with increasing SST. ERA5 precipitation reaches a local minimum at about 26 ∘C that vanishes when constraining vertical velocity to strongly rising motion and excluding areas of weak correlation between precipitation and vertical velocity. This indicates that instead of moisture limitations as over land, circulation dynamics rather limit precipitation formation over the ocean. For the strongest rising motion, precipitation scaling converges to a constant value at all precipitation percentiles. Overall, high resolutions in observations and climate models are key to understanding and predicting the sensitivity of oceanic precipitation extremes to a change in SST.

Advances in understanding large‐scale responses of the water cycle to climate change

“…6), and an increasing height of the tropopause with warming allows the establishment of larger systems 329 that can amplify total storm precipitation. 326 This is corroborated by observed scalings up to three times the rate expected from the Clausius-Clapeyron equation for multiple regions, [329][330][331][332] albeit with low statistical certainty. 333,334 The relevance of present-day relationships to climate change remains questionable, 335,336 although is improved by considering scaling with dewpoint temperature, which reduces dependence on dynamical factors.…”

Anthropogenic intensification of short-duration rainfall extremes

“…Although land is warming faster than the global mean, allowing faster rises in saturation specific humidity, this effect is not expected to enhance moisture increases over land since the ultimate source of moisture is primarily the oceans which are warming closer to the global mean rate. Other studies have corroborated this super-CC intensification 25,18,83 , albeit with potentially low statistical certainty due to short record lengths 84 . Evidence has also been found, mainly in tropical locations, for a strengthening of precipitation systems and significant effects of warming on peak intensities in urban areas 85,86 , with intensification of peak intensities and frequencies of hourly extreme precipitation tending to occur downwind of urban areas in mid-latitude locations such as the US Mid-west 87 .…”

Weather and Climate Extreme Events in a Changing Climate

“…There is a considerable body of literature examining scaling of sub-daily precipitation extremes, conditional on day-to-day air or dew-point temperatures (Westra et al, 2014;Fowler et al, 2021). This scaling, also termed 'apparent scaling' (Fowler et al, 2021), is robust when different methodologies are used in different regions, ranging between the C-C and two-times the C-C rate (e.g., Formayer and Fritz, 2017;Lenderink et al, 2017;Burdanowitz et al, 2019). This is confirmed when sub-daily precipitation data collected from multiple continents (Lewis et al, 2019) are analysed in a consistent manner using different methods (Ali et al, 2021).…”