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Morphology of organized convection in tropics and subtropics. Chuntao Liu. Table of content. Differences between land and ocean in the organized convection. Where are the organized convection? Seasonal variation of the organized convection. Diurnal variation of the organized convection.
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Morphology of organized convection in tropics and subtropics Chuntao Liu
Table of content • Differences between land and ocean in the organized convection. • Where are the organized convection? • Seasonal variation of the organized convection. • Diurnal variation of the organized convection. • Linear shaped organized convection and their orientations. • Relationship between Wind shear and the shapes of the organized convection.
Examples of organized convection with different “shapes” The shape of the convective region is inferred by major and minor axis of fitting ellipse over the contiguous convective raining area identified by 2A23 algorithm
Precipitation regions and Convective regionsland (contours) vs. ocean (color fill) Convective region: Size: Land > Ocean Linear shape: more over ocean Precipitation region: Size: Ocean > land Linear shape: more over ocean
Samples of the organized convection and precipitation region
Where are they? • More round systems over land. • More convective lines over ocean. • How about meridional change?
# of samples Sample bias is not removed.
Winter time frontal systems dominate the local organized convection Higher fraction of linear shape over ocean
For precipitation features
How about the seasonal variation? Large organized convection (> 1000 km2) Linear shape organized convection (minor / major axis < 0.2)
After remove the sample bias, there are more organized convection over tropics than subtropics However, the fraction of the large convective regions is higher over subtropics, especially in winter time over ocean, and spring over land
Orientation of the convective lines Color represents the orientation, deep red is from north-northeast to southwest deep blue is from north-northwest to southeast Size of the symbols represent the size of the convective lines Note the terrain impact to the orientation of the lines over south slope of Himalayas
Orientation transition from land to ocean North-South Northwest-Southeast East-west Northeast-Southwest North-South Over subtropics, convective lines are more north-south oriented over ocean than over land
Orientation of the precipitation regions are more complicated due to the complexity of the trailing stratiform region
Diurnal variation of shapes of organized convection Convective lines tend to occur a little earlier in the day
Convective intensity differences land (contours) vs. ocean (colorfill) In addition to the general weaker convective intensity over ocean, there is a group of organized, but shallow convection over ocean (15% compare to 1.5% over land).
Why there are different shape of the convection? especially for those linear shape systems? • Low level wind shear is shown to be important with the squall lines. • The wind component along the line and cross line are believed to have some roles. • CAPE? • Mid level moisture.
