Tiny raindrops pose big challenges: Argonne researchers improve climate models, prediction of climate change
From space, large decks of closely spaced stratocumulus clouds appear like bright cotton balls hovering over the ocean. They cover vast areas — literally thousands of miles of the subtropical oceans — and linger for weeks to months.
Because these marine clouds reflect more solar radiation than the surface of the ocean, cooling the Earth's surface, the lifetime of stratocumulus clouds is an important component of the Earth's radiation balance. It is necessary, then, to accurately represent cloud lifetimes in the earth system models (ESM) used to predict future climate conditions. Turbulence — air motions occurring at small scales — is primarily responsible for the longevity of marine stratocumulus clouds.
Drizzle — precipitation comprising water droplets smaller than half a millimeter in diameter — is constantly present within and below these marine cloud systems. Because these tiny drops affect and are affected by turbulence below marine clouds, scientists need to know more about how drizzle affects turbulence in these clouds to enable more accurate climate forecasts.
A team led by EVS atmospheric scientist Virendra Ghate and EVS principal atmospheric research engineer Maria Cadeddu, has been studying the impact of drizzle inside marine clouds since 2017. Ghate and Cadeddu were interested in geophysical variables, such as cloud water content, drizzle particle size and others. Combining measurements from different instruments, they developed a novel algorithm that synergistically retrieved all the necessary parameters involved in drizzle-turbulence interactions.
“The analysis of the developed dataset allowed us to show that drizzle decreases turbulence below stratocumulus clouds — something that was only shown by model simulations in the past,” said Ghate. “The richness of the developed data will allow us to address several fundamental questions regarding drizzle-turbulence interactions in the future.”
Read the full article by Anna Marie Tomczyk.