84th AMS Annual Meeting

Wednesday, 14 January 2004
Global seasonal variations of cirrus clouds using the Terra MODIS instrument
Hall AB
Marjorie Shoemake, Texas A&M University, College Station, TX; and L. Panetta, P. Yang, and B. C. Gao
Understanding the effects that cirrus clouds have on radiative transfer processes is critical when accurately predicting climate changes. It is well known that cirrus clouds have the ability to both offset and contribute to global warming by affecting the radiative transfer budget in two opposing processes: 1) increased albedo decreases solar input, and 2) increased albedo decreases infrared output. Three different weather mechanisms form cirrus clouds; cumulonimbus convection, baroclinic fronts and lows, and orographic lifting. The global variations of cirrus clouds over different seasons are investigated using the Level 3 monthly-mean Moderate Resolution Imaging Spectroradiometer (MODIS) atmospheric data products. The most frequent and strongest signal of cirrus clouds year round can be found within the Intertropical Convergence Zone (ITCZ), oscillating north and south with the changing seasons. The MODIS cirrus cloud monthly mean data can also resolve tracks of cirrus produced by hurricanes and tropical storms. A semi-strong cirrus cloud signal is seen over the Tibetan Plateau during the Northern Hemispheric winter to spring season, while appearing almost nonexistent from summer to fall. The MODIS instrument includes an unprecedented channel centered at 1.375Ám, established to detect the presence of thin wispy cirrus clouds. It is expected that the measurements of cirrus clouds using the MODIS instrument will provide an accurate assessment of the optical properties of high clouds, and thus give a better understanding of global climate.

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