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arXiv · 2512.03066

The Iris Illusion in the Tropical Sky Seen Through Two Decades of Aura MLS Ice Water Contents

Yiguo Zhang
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Abstract

I analyzed ice water content (IWC) data from the Aura Microwave Limb Sounder (MLS) and sea surface temperature (SST) data from NOAA's Optimum Interpolation SST (OISST) product from 2004 to 2024. Using these data, I derived monthly infrared (IR) leakage over the tropics and computed derivatives of both the IR leakage and tropical SST time series from 2005 to 2023. These two derivatives produced a Pearson correlation of -0.49, indicating that IR leakage decreases when SST increases. This behavior contradicts the trend predicted by the Iris hypothesis, suggesting that tropical cirrus clouds strengthen, rather than weaken, as the ocean warms.

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Yiguo Zhang. 2025-11-27. The Iris Illusion in the Tropical Sky Seen Through Two Decades of Aura MLS Ice Water Contents. https://arxiv.org/abs/2512.03066

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