Researchers improve simulations of deep moist convection to accurately predict effects of climate change

November 8, 2013
Figure 1: The global Nonhydrostatic ICosahedral Atmospheric Model, when run with a 0.87-kilometer grid size, simulates realistic features of major weather structures. Credit: American Geophysical Union

Simulations of deep moist convection need to be run at grid resolutions finer than 2 kilometers to accurately predict the effects of climate change.

Deep moist atmospheric convection controls the development of major weather systems like hurricanes, drives the global transport of energy within the system and strongly influences the uncertainty of projected climate change. As computational power advances, the direct simulation of cloud processes within models is on the horizon. Yoshiaki Miyamoto, Hirofumi Tomita and their colleagues from the RIKEN Advanced Institute for Computational Science reveal that in order to realistically simulate the critical features of cloud convection, models will ultimately need to be run at a grid resolution no coarser than 2 kilometers.

Unless cloud simulations improve, uncertainties will remain unacceptably high for many pressing topics, such as the response of regional precipitation and global mean temperature to increases in greenhouse gas concentrations. Yet despite decades of research, the role of clouds in a changing climate remains unclear, largely reflecting a disconnect between cloud processes operating at the scale of individual water droplets and the 50- to 100-kilometer resolution used in many simulations of future climate.

Miyamoto and his colleagues showed that an intermediate resolution can be used to drive deep moist convection, thus providing a clear target for future climate model development. The team simulated 12 hours of global cloud processes with the Nonhydrostatic ICosahedral Atmospheric Model (NICAM) at a range of grid spacings of 0.87 to 14 kilometers. They found that simulations at 0.87 kilometers resolved deep moist convective processes ranging from individual subkilometer convective cells to the detail of tropical cyclones spanning hundreds of kilometers (Fig. 1).

At resolutions coarser than 2 kilometers, crucial cloud features were lost. "In the real world, convection is intensely variable and clouds have wide gradients in water vapor density and vertical velocity," says Miyamoto. "Coarser grids create unrealistically sharp transitions in cloud properties, with negative consequences for the realistic representation of related processes like condensation and precipitation."

New theoretical insights could also arise from the team's work. "Our finding that convective features change drastically at resolutions of 2 kilometers or more opens up new avenues for research into the interactions between convection and global atmospheric circulation that would have been invisible at coarser resolutions."

Hitting the 2-kilometer target will be a challenge. Even with ever-expanding computational power, 2-kilometer simulations of climate for a period of a few years, let alone the next century, are probably a decade or more away. Another option, according to Miyamoto, would be to simulate a limited area at a 2-kilometer spacing within a coarser global grid.

Explore further: Taming uncertainty in climate prediction

More information: Miyamoto, Y., Kajikawa, Y., Yoshida, R., Yamaura, T., Yashiro, H. & Tomita, H. Deep moist atmospheric convection in a subkilometer global simulation. Geophysical Research Letters 40, 4922–4926 (2013).

Related Stories

Taming uncertainty in climate prediction

March 23, 2012

( -- Uncertainty just became more certain. Atmospheric and computational researchers at Pacific Northwest National Laboratory used a new scientific approach called "uncertainty quantification," or UQ, that allowed ...

Ahoy aquaplanet: Identifying model resolution shortcomings

August 5, 2013

By putting models through their paces in an all-water world, scientists at Pacific Northwest National Laboratory found highly scale-sensitive issues in regional climate modeling. In the first of two studies, two approaches ...

A new metric to help understand Amazon rainforest precipitation

August 14, 2013

In the Amazon rainforest, the chain of events that turns a small-scale process like a localized increase in evaporation into a towering storm cloud is long and twisted. To understand the complex dynamics that lead to precipitation, ...

Recommended for you

Horn of Africa drying ever faster as climate warms

October 9, 2015

The Horn of Africa has become increasingly arid in sync with the global and regional warming of the last century and at a rate unprecedented in the last 2,000 years, according to new research led by a University of Arizona ...

Could 'The Day After Tomorrow' happen?

October 9, 2015

A researcher from the University of Southampton has produced a scientific study of the climate scenario featured in the disaster movie 'The Day After Tomorrow'.


Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (9) Nov 08, 2013
The Alchemist
1 / 5 (9) Nov 14, 2013
I've been predicting climate and macro-weather perfectly for years. It doesn't take any kind of resolution, just an understanding of weather systems, local terrain effects, will and...
Note artificial carriage return. Here it is for the clickers:


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.