New tool clears the air on cloud simulations

October 26, 2011 by Anne M Stark

(PhysOrg.com) -- Climate models have a hard time representing clouds accurately because they lack the spatial resolution necessary to accurately simulate the billowy air masses.

But Livermore scientists and international collaborators have developed a new tool that will help scientists better represent the observed in the sky in models.

Traditionally, observations from satellites infer the properties of clouds from the radiation field (reflection of sunlight back into space, or thermal emission of the planet). However, to accurately utilize satellite data in climate model assessment, a tool is required that allows an apples-to-apples comparison between the clouds simulated in a climate model and the retrieved from satellites.

"The models are becoming more interactive and are taking into account the radiation data from the satellite observations and is an important part of the process of making better climate models," said the Lab's Stephen Klein, who along with LLNL's Yuying Zhang and other collaborators have developed the Cloud-Feedback-Model Intercomparison Project Observation Simulator Package (COSP).

"The models have been improving and refining their representations of clouds and COSP will play an important role in furthering this improvement," Klein said.

Climate models struggle to represent clouds accurately because the models lack the spatial resolution to fully represent clouds. Global climate models typically have a 100-kilometer resolution while meteorological models have a 20-kilometer range. However, to accurately represent clouds as seen in , the scale would need to be from the 500-meter resolution to 1-kilometer range.

"But those small scales are not practical for weather or global climate models," Klein said. "Our tool will better connect with what the satellites observe – how many clouds, their levels and their reflectivity."

The COSP is now used worldwide by most of the major models for climate and weather prediction, and it will play an important role in the evaluation of models that will be reviewed by the next report of the Intergovernmental Panel on , Klein said.

The COSP allows for a meaningful comparison between model-simulated clouds and corresponding satellite observations. In other words, what would a satellite see if the atmosphere had the clouds of a climate model?

"COSP is important and necessary development because modeled clouds cannot be directly compared with observational data; the model representation of clouds is not directly equivalent to what satellites are able to see," Klein explained. "The COSP eliminates significant ambiguities in the direct comparison of model simulations with satellite retrievals."

COSP includes a down-scaler that allows for large-scale to estimate the clouds at the satellite-scale. The tool also allows modelers to diagnose how well models are able to simulate clouds as well as how climate change alters clouds. The tool already has revealed climate model limitations such as too many optically thick clouds, too few mid-level clouds and an overestimate of the frequency of precipitation. Additionally, COSP has shown that climate change leads to an increase in optical thickness and increases the altitude of high clouds and decreases the amount of low and mid-level clouds.

Explore further: The insides of clouds may be the key to climate change

More information: More information about the COSP appears in the August issue of the Bulletin of the American Meteorological Society. journals.ametsoc.org/doi/pdf/10.1175/2011BAMS2856.1

Related Stories

The insides of clouds may be the key to climate change

February 17, 2007

As climate change scientists develop ever more sophisticated climate models to project an expected path of temperature change, it is becoming increasingly important to include the effects of aerosols on clouds, according ...

Study could mean greater anticipated global warming

November 22, 2010

Global climate models disagree widely in the magnitude of the warming we can expect with increasing carbon dioxide. This is mainly because the models represent clouds differently. A new modeling approach successfully simulates ...

Down-and-dirty details of climate modeling

May 4, 2011

For the first time, researchers have developed a comprehensive approach to look at aerosols—those fine particles found in pollution—and their effect on clouds and climate. Scientists from Pacific Northwest National ...

Connecting the dots on aerosol details

July 27, 2011

Predicting future climate change hangs on understanding aerosols, considered the fine details in the atmosphere. Researchers at Pacific Northwest National Laboratory and the National Center for Atmospheric Research used a ...

Recommended for you

Climate ups odds of 'grey swan' superstorms

August 31, 2015

Climate change will boost the odds up to 14-fold for extremely rare, hard-to-predict tropical cyclones for parts of Australia, the United States and Dubai by 2100, researchers said Monday.

Quantifying the impact of volcanic eruptions on climate

August 31, 2015

Large volcanic eruptions inject considerable amounts of sulphur in the stratosphere which, once converted into aerosols, block sun rays and tend to cool the surface of the Earth down for several years. An international team ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

hush1
not rated yet Oct 26, 2011
This is good. Models having the same eyes, the same senses as satellites.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.