Aqua, CALIPSO, and TERRA satellite data all indicate lower frequency of cloud occurrence at mid-level altitudes in the North Atlantic Ocean, (45N-49N, 25W-5W)
Abstract
The altitude corresponding to cloud glaciation and release of latent heat is often an input in climate models and is important in many other problems such as interpreting satellite retrievals. Our findings, that mid-level clouds (in this study ~3-7 km ) are rare under some conditions, may render the precise glaciation level statistically unimportant for some of these studies: the majority of clouds will be far from the uncertain point of glaciation and easily designated, while clouds that are at mid-level, if in a low-density region/season, will be rare and not require precise designation. Indeed in some cases no mid-level clouds are seen for significant regions and spans of time: complementary use of CALIPSO and Aqua-MODIS, A-train satellites with a 1-2 minute lag between them, show that there are no mid-level clouds for N. Atlantic (45N-49N, 25W-5W), 2006-2008, September 15-30, day/afternoon (11:45-15:40 UTC) and night/morning (1:30-5:00 UTC). This example is further verified by data from TERRA-MODIS, covering the same region at different overpass times than the A-train satellites, the latter having near-polar orbits rather a near-circular orbit. TERRA-MODIS does retrieve some mid-level clouds, but they account for less than 1% of cloud-top phases retrieved. (See figure below for relevant histograms.) Studies of various regions and seasons will be presented in addition to these findings. This type of study, extended globally and annually, will present valuable data for modeling and interpretation of climatic trends.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.A13G0303A
- Keywords:
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- 0321 ATMOSPHERIC COMPOSITION AND STRUCTURE / Cloud/radiation interaction;
- 0360 ATMOSPHERIC COMPOSITION AND STRUCTURE / Radiation: transmission and scattering;
- 0394 ATMOSPHERIC COMPOSITION AND STRUCTURE / Instruments and techniques