Reconciling the Lack of a Robust Anvil Cloud Amount Response to Warming
Abstract
The stability-iris hypothesis proposes that tropical anvil cloud amount decreases with warming as anvils rise into environments of greater static stability. Here we show that there is no clear theoretical or simulated link between increasing static stability and anvil amount. We demonstrate analytically that identified sensitivities of static stability and pressure velocity to surface warming arise from decreasing air density aloft, which enters pressure-coordinate formulations but does not represent a process that dynamically constrains anvil formation. An ensemble of RCEMIP simulations verifies that the stability increase is robust yet arises from the air density reduction, and hence is not accompanied by a robust response in anvil amount, convectively driven water convergence into anvil levels, or the efficiency with which this convergence produces cloudiness. Overall, these findings dispel the expectation of a systematic reduction in anvil amount with warming arising from basic physical arguments.
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BibTeX
@misc{mcgraw2026reconciling,
title = {{Reconciling the Lack of a Robust Anvil Cloud Amount Response to Warming}},
author = {Zachary McGraw and Blaž Gasparini and Wouter Mol and Aiko Voigt},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.00429},
eprint = {2609.00429},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.00429},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Reconciling the Lack of a Robust Anvil Cloud Amount Response to Warming
AU - Zachary McGraw
AU - Blaž Gasparini
AU - Wouter Mol
AU - Aiko Voigt
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.00429
UR - https://arxiv.org/abs/2609.00429
AB - The stability-iris hypothesis proposes that tropical anvil cloud amount decreases with warming as anvils rise into environments of greater static stability. Here we show that there is no clear theoretical or simulated link between increasing static stability and anvil amount. We demonstrate analytically that identified sensitivities of static stability and pressure velocity to surface warming arise from decreasing air density aloft, which enters pressure-coordinate formulations but does not represent a process that dynamically constrains anvil formation. An ensemble of RCEMIP simulations verifies that the stability increase is robust yet arises from the air density reduction, and hence is not accompanied by a robust response in anvil amount, convectively driven water convergence into anvil levels, or the efficiency with which this convergence produces cloudiness. Overall, these findings dispel the expectation of a systematic reduction in anvil amount with warming arising from basic physical arguments.
ER -