Details

Autor(en) / Beteiligte

• Dagan, Guy
• Seeley, Jacob T.
• Steiger, Nathan

Titel

Convection and Convective‐Organization in Hothouse Climates

Ist Teil von

• Journal of advances in modeling earth systems, 2023-11, Vol.15 (11), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2023

Quelle

Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals

Beschreibungen/Notizen

• In a “hothouse” climate, warm temperatures lead to a high tropospheric water vapor concentration. Sufficiently high water vapor levels lead to the closing of the water vapor infrared window, which prevents radiative cooling of the lower troposphere. Because water vapor also weakly absorbs solar radiation, hothouse climates feature radiative heating of the lower troposphere. In recent work, this radiative heating was shown to trigger a shift into a novel “episodic deluge” precipitation regime, where rainfall occurs in short, intense outbursts separated by multi‐day dry spells. Here, we further examine the role of the lower tropospheric radiative heating (LTRH) in the transition into the “episodic deluge” regime. We demonstrate that under high sea‐surface temperature the “episodic deluge” regime could be formed even before the LTRH turns positive. In addition, we examine whether these oscillations operate on larger scales and how these oscillations, which represent “temporal” convective self‐organization, would manifest in the presence of traditional “spatial” self‐ or forced‐aggregation in large‐domain convection‐permitting simulations. We find that the temporal oscillations become much less synchronized throughout a large domain (O $\mathcal{O}$ 1,000 km) because gravity waves cannot propagate fast enough to synchronize convection. We also show that temporal oscillations still dominate the rainfall distribution even when there is tropical convective self‐aggregation or a large‐scale overturning circulation. These results could have important implications for extreme precipitation events under a warming climate. Plain Language Summary Water vapor is a strong greenhouse gas that closely follows surface temperature. Under very warm (“hothouse”) conditions, which are believed to have existed in the Earth's distant past, temperature and water vapor are sufficiently high that the greenhouse effect of water vapor prevents heat from escaping out of the lower part of the atmosphere. This trapped heat makes the lower atmosphere even hotter, causing some unusual weather patterns. For example, it was recently shown to lead to short but intense bursts of rain, followed by several days of dry weather. However, it is unclear whether these patterns occur on larger scales and what their characteristic scale is. In this study, computer simulations were conducted to address these uncertainties and to further elucidate the role of the lower tropospheric radiative heating in the transition into this “episodic deluge” regime. We show that these temporal oscillations dominate the rainfall distribution even in the presence of other atmospheric factors such as tropical convective self‐aggregation or large‐scale overturning circulation. Key Points We examine the temporal and spatial organization of convection in simulated hothouse conditions We demonstrate that lower tropospheric radiative heating is not necessary for the “episodic deluge” precipitation regime “Episodic deluge” precipitation regime occurs in self‐ or forced‐convective aggregated large domain simulations but is less synchronized