ARM Develops an Affordable, Flexible, and More Accurate Method for Computing Atmospheric Radiative Transfer


A team of international researchers led by DOE’s Atmospheric Radiation Measurement Program (ARM) has developed an improved way to mathematically describe the transfer of the sun’s rays (radiative transfer) through the atmosphere. This new method will improve the ability of models to simulate and predict changes in the Earth’s weather and climate. Current methods used to simulate radiative transfer through the atmosphere require large amounts of computer resources and include assumptions regarding the nature and properties of clouds that are subject to bias and error. The new method (named McICA) uses a complex statistical technique to more efficiently incorporate the complexity of cloud properties and their effects on the sun’s rays into radiation transfer calculations. The code is more accurate because it does many radiative transfer calculations using the actual cloud distributions as opposed to doing one radiative transfer calculation with average cloud distributions. Previously, the long computation times rendered the statistical approach impracticable. However, the investigators’ ingenious scheme dramatically reduces the computational time and makes the approach affordable. The inclusion of the new code into climate models will help reduce uncertainty in global climate and weather predictions. The code has been released for use by modelers in their models. The McICA technique is now being tested for the European Centre for Medium Range Weather Forecasting model.