Observations of the life cycle of marine stratocumulus drizzle cells: Preliminary results Sandra Yuter, Andrew Hall, and Casey Burleyson

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All C-band radar data: BL height controls on drizzle Casey’s fig Casey’s fig 3

“Cell” = contiguous group of pixels > 4 dBZ and “Cell” = contiguous group of pixels > 4 dBZ and  0.5 km 2 (8 pixels, each 0.25 km x 0.25 km) Cell’s centroid and area are calculated Cell’s centroid and area are calculated 4 Reflectivity  Filtered/Enhanced  Cells Identified

Cells from all C-band radar data 5 Cell count

Cell Tracking (3 min data) Cells are linked by proximity Cells are linked by proximity Tracks joined preferentially to new cells in their established direction of travel Tracks joined preferentially to new cells in their established direction of travel Track ended if distance moved is > 4 km in 3 min Track ended if distance moved is > 4 km in 3 min Refinement still in progress Refinement still in progress Some long tracks are erroneously broken into smaller tracks Some long tracks are erroneously broken into smaller tracks Not all cells are tracked Not all cells are tracked 6

6 cases (radar domain on IR) 7 Satellite/radar of each one --SY 7 hrs 20 hrs8 hrs 22 Oct Oct Oct Oct Nov Nov 2008

Histograms of all tracks 8 22 Oct Oct Oct Oct Nov Nov 2008 Long tracks = 45 min or longer, 72 tracks

Example of drizzle cell tracking 9

Long Tracks: Cell Size vs. Tracked Duration 10 Typical cell size 2 – 4 km 2

11 Cell Median dBZ vs. Track Length Centered on Peak Intensity Comstock et al. (2005) EPIC results

12 Circle size  Cell Area Long Track Cell Characteristics BL height (m)

Preliminary Conclusions Trackable cells (> 4 dBZ) are typically between 2 and 4 km 2 Trackable cells (> 4 dBZ) are typically between 2 and 4 km 2 Intense cells with median Z > 15 dBZ are outliers Intense cells with median Z > 15 dBZ are outliers Cells with long-lived tracks (> 45 min) Cells with long-lived tracks (> 45 min) Occur in both shallow and deep BL clouds Occur in both shallow and deep BL clouds Usually have a single peak intensity along their track Usually have a single peak intensity along their track Long cell tracks within shallow BL tend to occur at earlier local times compared to most long tracks within deep BL Long cell tracks within shallow BL tend to occur at earlier local times compared to most long tracks within deep BL

14 BL Height and Cell Size