Multifractal Analysis for Evaluating the Representation of Clouds in Global Kilometer‐Scale Models

Abstract Clouds are one of the largest sources of uncertainty in climate predictions. Global km‐scale models need to simulate clouds and precipitation accurately to predict future climates. To isolate issues in their representation of clouds, models need to be thoroughly evaluated with observations....

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Main Authors: Lilli J. Freischem, Philipp Weiss, Hannah M. Christensen, Philip Stier
Format: Article
Language:English
Published: Wiley 2024-10-01
Series:Geophysical Research Letters
Subjects:
Online Access:https://doi.org/10.1029/2024GL110124
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author Lilli J. Freischem
Philipp Weiss
Hannah M. Christensen
Philip Stier
author_facet Lilli J. Freischem
Philipp Weiss
Hannah M. Christensen
Philip Stier
author_sort Lilli J. Freischem
collection DOAJ
description Abstract Clouds are one of the largest sources of uncertainty in climate predictions. Global km‐scale models need to simulate clouds and precipitation accurately to predict future climates. To isolate issues in their representation of clouds, models need to be thoroughly evaluated with observations. Here, we introduce multifractal analysis as a method for evaluating km‐scale simulations. We apply it to outgoing longwave radiation fields to investigate structural differences between observed and simulated anvil clouds. We compute fractal parameters which compactly characterize the scaling behavior of clouds and can be compared across simulations and observations. We use this method to evaluate the nextGEMS ICON simulations via comparison with observations from the geostationary satellite GOES‐16. We find that multifractal scaling exponents in the ICON model are significantly lower than in observations. We conclude that too much variability is contained in the small scales (<100km) leading to less organized convection and smaller, isolated anvils.
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spelling doaj-art-ec524df7883a473dba56ad32cdddb0f92025-08-20T02:13:43ZengWileyGeophysical Research Letters0094-82761944-80072024-10-015120n/an/a10.1029/2024GL110124Multifractal Analysis for Evaluating the Representation of Clouds in Global Kilometer‐Scale ModelsLilli J. Freischem0Philipp Weiss1Hannah M. Christensen2Philip Stier3Department of Physics University of Oxford Oxford UKDepartment of Physics University of Oxford Oxford UKDepartment of Physics University of Oxford Oxford UKDepartment of Physics University of Oxford Oxford UKAbstract Clouds are one of the largest sources of uncertainty in climate predictions. Global km‐scale models need to simulate clouds and precipitation accurately to predict future climates. To isolate issues in their representation of clouds, models need to be thoroughly evaluated with observations. Here, we introduce multifractal analysis as a method for evaluating km‐scale simulations. We apply it to outgoing longwave radiation fields to investigate structural differences between observed and simulated anvil clouds. We compute fractal parameters which compactly characterize the scaling behavior of clouds and can be compared across simulations and observations. We use this method to evaluate the nextGEMS ICON simulations via comparison with observations from the geostationary satellite GOES‐16. We find that multifractal scaling exponents in the ICON model are significantly lower than in observations. We conclude that too much variability is contained in the small scales (<100km) leading to less organized convection and smaller, isolated anvils.https://doi.org/10.1029/2024GL110124fractalsglobal km‐scale modelsdeep convectionconvective organizationmodel evaluation
spellingShingle Lilli J. Freischem
Philipp Weiss
Hannah M. Christensen
Philip Stier
Multifractal Analysis for Evaluating the Representation of Clouds in Global Kilometer‐Scale Models
Geophysical Research Letters
fractals
global km‐scale models
deep convection
convective organization
model evaluation
title Multifractal Analysis for Evaluating the Representation of Clouds in Global Kilometer‐Scale Models
title_full Multifractal Analysis for Evaluating the Representation of Clouds in Global Kilometer‐Scale Models
title_fullStr Multifractal Analysis for Evaluating the Representation of Clouds in Global Kilometer‐Scale Models
title_full_unstemmed Multifractal Analysis for Evaluating the Representation of Clouds in Global Kilometer‐Scale Models
title_short Multifractal Analysis for Evaluating the Representation of Clouds in Global Kilometer‐Scale Models
title_sort multifractal analysis for evaluating the representation of clouds in global kilometer scale models
topic fractals
global km‐scale models
deep convection
convective organization
model evaluation
url https://doi.org/10.1029/2024GL110124
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