High-Resolution Image

Cloud tomography is a novel method for determining cloud water distribution by measuring cloud microwave emission from multiple directions. The upper plot shows a 2D cross-sectional snapshot of the liquid water structure of a stratocumulus cloud simulated by a large-eddy model. It also shows the four scanning microwave radiometers used to retrieve the cloud liquid water structure shown in the lower plot (the cloud is assumed frozen while the radiometers scan it). Note the fidelity of the retrieval. We greatly improve the tomographic retrieval methods proposed in the 1980s by: (1) using an iterative constrained algorithm; and (2) replacing the conventional pixel scheme with a functional representation. With four microwave radiometers, our tomographic method captures the spatial variation of cloud water at a resolution of 10’s of meters in the vertical and 100’s of meters in the horizontal. The difference between the true and retrieved liquid water fields is within 5 percent of its maximum water content.

(submitted by Warren Wiscombe, NASA and Dong Huang, Brookhaven National Laboratory)