Abstract
This study explores the tropical land distribution of precipitation and its extremes focusing on the daily 1° × 1° scale. A common period of 5-year over the tropical belt (30°s–30°n) corresponding to more than 39 million data points, is used to highlight the robust (and non-robust) observed features. A set of 10 observational products is analyzed ranging from satellite only to rain gauges only products and various blended intermediates as well as a sub ensemble of satellite-based products relying upon microwave observations. Overall, the various datasets show a small diversity of response as far as tropical land mean precipitation is concerned. When sorted by surface temperature, the spread in mean rainfall is also well below 10% over a large span of the surface temperature regime. The consistency between the surface temperature and the extreme precipitation is further investigated by computing the thermodynamic scaling of daily precipitation extreme with surface temperature. The wet days’ 99.9th and 99th percentiles are considered and corresponds to ‘extreme’ extremes (∼110 mm d−1) and ‘moderate’ extremes (∼60 mm d−1), respectively. The analysis reveals three regimes over the 287–305 K 2 m temperature range. In the cold regime, 287–293 K, extremes exhibit no dependence to surface temperature while in the warm regime, 299–305 K, the extremes decrease with temperature as identified in previous studies. Over the 293–299 K regime, the scaling of the sub ensemble of satellite products is ∼5.2 K/% for the ‘extremes’ extremes and 5.0% for the ‘moderate’ extremes, and is robust throughout the sub ensemble. This analysis fills the regional gap of previous conventional data based studies and further confirms the Clausius–Clapeyron theoretical expectation for the tropical land regions.
Highlights
Global energy budget considerations provide a strong constraint of global precipitation owing to the coupling between energy and water budgets and offer a physically sound theoretical pathway to explore the future evolution of precipitation under climate warming through changes of the atmospheric water vapor content (Ramanathan 1981)
Thermodynamics dictates an increase of the atmospheric water vapor content under warming at a rate of 6%–7%/K which translates in a 2%–3%/K increase in global mean precipitation via the induced radiative cooling closure enforcement of the water and energy budget (Stephens and Ellis 2008)
A secondary aim of this paper is to explore the ability of the gridded products to provide a robust perspective on the thermodynamic scaling of precipitation extremes to the surface temperature over the tropical land in the current climate
Summary
Global energy budget considerations provide a strong constraint of global precipitation owing to the coupling between energy and water budgets and offer a physically sound theoretical pathway to explore the future evolution of precipitation under climate warming through changes of the atmospheric water vapor content (Ramanathan 1981). The net condensation rate of the atmosphere is the outcome of the complex interplay between the thermodynamic profiles of the column, the intensity of convection, the cloud and rain microphysics and in particular to the tropics, the mesoscale dynamics of the cloud system (e.g. Roca et al 2017) Despites this complexity, in the tropics, following atmosphere dry static energy budget considerations and focusing on extreme conditions, extreme precipitation rate (Pe) can be expressed (O’Gorman and Schneider 2009) as. A secondary aim of this paper is to explore the ability of the gridded products to provide a robust (or not) perspective on the thermodynamic scaling of precipitation extremes to the surface temperature over the tropical land in the current climate.
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