Idealized convection‐permitting simulations of radiative‐convective equilibrium have become a popular tool for understanding the physical processes leading to horizontal variability of tropical water vapor and rainfall. However, the applicability of idealized simulations to nature is still unclear given that important processes are typically neglected, such as lateral water vapor advection by extratropical intrusions, or interactive ocean coupling. Here, we exploit spectral analysis to compactly summarize the multiscale processes supporting convective aggregation. By applying this framework to high‐resolution reanalysis data and satellite observations in addition to idealized simulations, we compare convective‐aggregation processes across horizontal scales and data sets. The results affirm the validity of the radiative‐convective equilibrium simulations as an analogy to the real world. Column moist static energy tendencies share similar signs and scale selectivity in convection‐permitting models and observations: Radiation increases variance at wavelengths above 1,000 km, while advection damps variance across wavelengths, and surface fluxes mostly reduce variance between 1,000 and 10,000 km.
There is no consensus on the physical mechanisms controlling the scale at which convective activity organizes near the Equator. Here, we introduce a diagnostic framework relating the evolution of the length‐scale of convective aggregation to the net radiative heating, the surface enthalpy flux, and horizontal energy transport. We evaluate these expansion tendencies of convective aggregation in 20 high‐resolution cloud‐permitting simulations of radiative‐convective equilibrium. While both radiative fluxes contribute to convective aggregation, the net long‐wave radiative flux operates at large scales (1,000–5,000 km) and stretches the size of moist and dry regions, while the net short‐wave flux operates at smaller scales (500–2,000 km) and shrinks it. The surface flux expansion tendency is dominated by convective gustiness, which acts to aggregate convective activity at smaller scales (500–3,000 km).
more » « less- NSF-PAR ID:
- 10453672
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Quarterly Journal of the Royal Meteorological Society
- Volume:
- 145
- Issue:
- 720
- ISSN:
- 0035-9009
- Page Range / eLocation ID:
- p. 947-966
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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