What are anvil clouds and other tropical cirrus and
why should we care about them?
(Gasparini et al., 2023; ACP)
A different type of anvil
floating in the sky
Tropical cirrus clouds are essential for climate, but our understanding of these clouds is limited due to their dependence on a wide range of small- and large-scale climate processes. The cited publication reviews recent advances in the study of tropical cirrus clouds, points out remaining open questions, and suggests ways to resolve them.
A Lagrangian perspective on anvil lifecycle in current and future climate
(Gasparini et al., 2021, JGR-A)
Animation of the output from a high resolution general circulation model simulation over the Tropical Western Pacific, in which the tracked mesoscale convective systems are delineated in red contours, while the air parcels detrained from active deep convection are shown as trajectories, colored based on their instantaneous ice mixing ratio value. The background colors represent the outgoing longwave radiation.
Clouds can have both cooling and warming effects on the climate. Storm clouds in the tropics primarily cool the climate by reflecting a significant amount of sunlight into space. The remnants of these storm clouds, known as anvil clouds because of their characteristic shape, can persist for several hours at very high altitudes and cover large areas after the initial intense rain events. Anvil clouds, like greenhouse gases, trap some of the Earth's radiation in the atmosphere, contributing to global warming. Despite their important role in the tropical climate system, the transition from highly reflective storm clouds to thin anvil clouds is not fully understood. To investigate this transition, we use climate model simulations that follow the evolution of anvil clouds from their formation in storm clouds to their eventual dissipation. By using this climate model, we can study this process under both present and future warmer climate conditions. Our results indicate that in a warmer climate, storm clouds contain more ice and reflect more sunlight, resulting in increased cooling. However, the properties of thin anvil clouds do not change significantly with warming.
Why should we care if an anvil cloud is thick or thin and
what drives the evolution of anvil clouds?
(Gasparini et al., 2019; JAMES & Gasparini et al., 2022, JClim)
In-atmospheric radiative effects play a role in the net cloud radiative effect neutrality in tropics! While microphysics modulates its effects.
Control
No atmospheric cloud radiative effects
Why is the net cloud radiative effect of tropical anvil clouds close to neutral? It's turbulence, driven by in-atmospheric radiative effects, which is strongly modulated by microphysics. Details matter!
More in Hartmann, Gasparini, et al., 2018, JAMES and Gasparini et al., 2019, JAMES)
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All you need at first is some radiation, that cools clear sky areas and triggers deep convection.
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Latent heating helps to grow the convective tower. After that, radiative heating (red) drives most of the evolution near the cloud top. Latent heating (green) is important near the cloud base. Blue represents the residual/turbulence.
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Both radiative and latent heating drive turbulence and organized cloud-scale circulations. In fact, they form a heating sandwich, which drives the circulations.
Ever wondered how does the climate model output look like? Can we simulate clouds and convection in the tropics in a reasonable way?
Check out the animation of cloud albedo from a simulation with E3SM model at 0.25°x0.25° resolution!
