Limitations to Note

Close inspection of the MODIS imagery and resulting products leads us to believe that the inference of cloud overlap has obvious limitations. Among these are the following:

• in areas where the cloud deck covers a wide spatial area, the lack of clear-sky radiance information becomes a limiting factor on the application of the algorithm.
• midlevel clouds (e.g., altostratus and altocumulus) tend to cause confusion. If three cloud layers are present in an array, the midlevel cloud layer tends to be identified as being multilayered, when in reality it may be a distinct cloud layer in the data.
• another area that bears further development is when towering cumulus, i.e., active convection, are present in the imagery. In such areas, there tend to be a range of cloud heights. This is a very different situation than what we are trying to identify, specifically high-level thin cirrus overlying low-level water clouds.

Efforts are underway to ameliorate these problems. We expect that more issues will become apparent as more people inspect the product.