Wheeler and Hendon 2004 The MJO

7N Equator

SKa NCAR S-PolKa Radar

Satellite Global models Soundings Other island radars Ship data Ship radars Aircraft data S-PolKa radar NCAR radar processor UW server UW workstations Daily Science Summaries NCAR field catalog Project Data Flow LIghtning

Radar experiment goal  Characteristics and evolution of the MJO cloud population in the region where the disturbance builds up Addu Atoll

Supp. Active Lull Rain over area scanned by S-PolKa

Suppressed condition echoes

Supp. Active Lull

Suppressed phases: Lines of non- precipitating clouds

Suppressed phases: The “worm echo”

Slightly active moist layer Clouds building at cold pool boundaries

Slightly active moist layer Clouds building at cold pool boundaries

Cold pool boundaries seen in differential reflectivity (ZDR) Birds? Dragonflies? ???

Birds caught on camera

graupel small ice large non-melting ice heavy rain melting ice Moderate cumulonimbus begin to grow upscale Doppler velocity Hydrometeor type

Supp. Active Lull

October 16

Refl.Rain Conv. Strat. October 16

5 km 10 km Intense melting layer melting snow graupel 50 dBZ!

Active phase few days later Convection feeding into a large MCS

Biggest MCS of first active phase: weak unidirectional shear

Supp. Active Lull

Giant Rings of Convection Larger than mesoscale organization of deep convection

Squall line in late active phase westerlies Doppler velocity Hydrometeor type

Supp. Active Lull

Suppressed condition clouds

Supp. Active Lull

Supp. Active Lull

Westerly Surges November October Larger than mesoscale organization of deep convection

Supp. Active Lull

Long arc line

Long arc line segment on radar

Squall line in the strong westerlies

Weak stratiform in the strong westerlies

Stratiform Rain Fraction S-PolKa S-band Stratiform Rain Fraction

Supp. Active Lull

The most robust squall line in the strong westerlies… …only moderate stratiform …robust momentum transport

Supp. Active Lull

Summary of MJO cloud population characteristics & evolution seen by the S-PolKa radar  Humidity gradient layers monitored & measured  Cloud lines dominate in highly suppressed period  Cold pools are first stage of convective population  Graupel & other ice lofted & input into stratiform regions  Convection enhanced inside stratiform regions  MCS development strongest in weak shear  Shear inhibits stratiform region formation  Westerlies organize convection on larger than mesoscale  Squall lines form in westerlies at back of active zone  Squall lines transport momemtum downward

End This research is supported by NSF grant ATM AGS , DOE grant DE- SC /ER-64752, and NASA grants NNX10AM28G and NNX10AH70G