Schröder, Marc;
König, Marianne;
Schmetz, Johannes
Deep convection observed by the Spinning Enhanced Visible and Infrared Imager on board Meteosat 8: Spatial distribution and temporal evolution over Africa in summer and winter 2006
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Media type:
E-Article
Title:
Deep convection observed by the Spinning Enhanced Visible and Infrared Imager on board Meteosat 8: Spatial distribution and temporal evolution over Africa in summer and winter 2006
Contributor:
Schröder, Marc;
König, Marianne;
Schmetz, Johannes
imprint:
American Geophysical Union (AGU), 2009
Published in:Journal of Geophysical Research: Atmospheres
Language:
English
DOI:
10.1029/2008jd010653
ISSN:
0148-0227
Origination:
Footnote:
Description:
<jats:p>We analyze the spatial distribution of deep convection and its diurnal cycle and life cycle over Africa in June and December 2006. We investigate regions of distinct temporal evolution and of largest frequency of occurrence of deep convection (hereinafter referred to as convective activity), and we define and identify the deep convective stage from space observations. The analysis is based on hourly, half‐hourly, and quarter‐hourly brightness temperature (BT) observations of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board Meteosat 8. Eulerian and Lagrangian approaches are utilized. In the Eulerian approach, diurnal cycles and spatial distributions of BTs are calculated as averages on a local solar time (LST) and pixel basis. In the Lagrangian approach we use a stand‐alone algorithm that tracks deep convective systems. Deep convection is frequently found over mountainous regions and exhibits a distinct diurnal cycle over large lakes. Local maxima of convective activity and origin of tracked systems are observed over the ocean off the west coast of Africa early in the morning. Over land the diurnal cycle of deep convective systems starts with strong rates of BT change in the formative stage, continues with the minimum BT around 1530 LST (start of the mature stage), and reaches the maximum cold cloud cover at 1730 LST (end of mature stage). The maximum number of split events marks the center of the dissipation stage at ∼1930 LST. A time shift of 1–2 h to earlier times is found in December. The life cycle analysis perfectly complements the diurnal cycle analysis and reveals characteristics of deep convective systems around the time of minimum BT10.8. Extreme rates of BT change and area expansion rates successively increase with decreasing temporal resolution. Thus quarter‐hourly measurements are needed to observe the most vigorous updraft and downdraft events.</jats:p>