Changing Characteristics of Tropical Extreme Precipitation–Cloud Regimes in Warmer Climates

Journal Article · Thu Jun 08 00:00:00 EDT 2023 · Atmosphere (Basel)

DOI:https://doi.org/10.3390/atmos14060995· OSTI ID:2221917

Lau, William M.  ^[1]; Kim, Kyu-Myong ^[2]; Harrop, Bryce  ^[3]; Leung, Lai Ruby  ^[3]

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1. University of Maryland, College Park, MD (United States)
2. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
3. Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

In this study, we investigated the changing characteristics of climatic scale (monthly) tropical extreme precipitation in warming climates using the Energy Exascale Earth System Model (E3SM). The results are from Atmospheric Model Intercomparison Project (AMIP)-type simulations driven by (a) a control experiment with the present-day sea surface temperature (SST) and CO₂ concentration, (b) P4K, the same as in (a) but with a uniform increase of 4K in the SST globally, and (c) the same as in (a), but with an imposed SST and CO₂ concentration from the outputs of the coupled E3SM forced by a 4xCO₂ concentration. We found that as the surface warmed under P4K and 4xCO₂, both convective and stratiform rain increased. Importantly, there was an increasing fractional contribution of stratiform rain as a function of the precipitation intensity, with the most extreme but rare events occurring preferentially over land more than the ocean, and more so under 4xCO₂ than P4K. Extreme precipitation was facilitated by increased precipitation efficiency, reflecting accelerated rates of recycling of precipitation cloud water (both liquid and ice phases) in regions with colder anvil cloud tops. Changes in the vertical profiles of clouds, condensation heating, and vertical motions indicate increasing precipitation–cloud–circulation organization from the control and P4K to 4xCO₂. The results suggest that large-scale ocean warming, that is, P4K, was the primary cause contributing to an organization structure resembling the well-known mesoscale convective system (MCS), with increased extreme precipitation on shorter (hourly to daily) time scales. Additional 4xCO₂ atmospheric radiative heating and dynamically consistent anomalous SST further amplified the MCS organization under P4K. Analyses of the surface moist static energy distribution show that increases in the surface moisture (temperature) under P4K and 4xCO₂ was the key driver leading to enhanced convective instability over tropical ocean (land). However, a fast and large increase in the land surface temperature and lack of available local moisture resulted in a strong reduction in the land surface relative humidity, reflecting severe drying and enhanced convective inhibition (CIN). It is argued that very extreme and rare “record-breaking” precipitation events found over land under P4K, and more so under 4xCO₂, are likely due to the delayed onset of deep convection, that is, the longer the suppression of deep convection by CIN, the more severe the extreme precipitation when it eventually occurs, due to the release of a large amount of stored surplus convective available potential energy in the lower troposphere during prolonged CIN.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); National Aeronautics and Space Administration (NASA)
• Grant/Contract Number: AC05-76RL01830; 300426-00001; 80NSSC21K1800
• OSTI ID: 2221917
• Report Number(s): PNNL-SA-192667
• Journal Information: Atmosphere (Basel), Vol. 14, Issue 6; ISSN 2073-4433
• Publisher: MDPI
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
climate-scale extreme tropical precipitation
stratiform and convective precipitation
precipitation efficiency
meso-scale convective complex
surface warming vs. moistening
convective inhibition over land