Transcript 131211SanFrancisco_AGU_Virts.ppt

MJO Modulation of Lightning in
Mesoscale Convective Systems
Katrina S. Virts and Robert A. Houze, Jr.
University of Washington
AGU Fall Meeting, San Francisco, 11 December 2013
Identifying MCSs using A-Train data
MODIS 10.8 m brightness temperature
AMSR-E rain rate
Years included: 2007-2010
Details in Yuan and Houze 2010
“Separated”
Separated
HCSMCS
active
260K
Heavy Rain
Closed
Rain
contour
“HCS”
“Connected”
active MCS
Details in Yuan and Houze 2010
World-Wide Lightning Location Network
(WWLLN)
Global network of 70+ sensors
Monitors very low frequency radio waves
Lightning strokes located to within 5 km and a few
s
World-Wide Lightning Location Network
(WWLLN)
Global network of 70+ sensors
Monitors very low frequency radio waves
Lightning strokes located to within 5 km and a few
s
Lightning in one-hour window
– Separate coordinate system for each MCS,
centered on largest raining core
– Lightning in cloudy grid boxes
MCS climatology
Indian
Ocean
Maritime
Continent
Western
SPCZ
Pacific Ocean
Maritime Continent
SMCSs
Active period - phases 3-4-5
Break period - phases 7-8-1
More frequent lightning, broader
lightning maximum during break period
MCS environments more unstable
during break period
W
Peak lightning at end of
break period
Lower lightning density
in CMCSs
E
TRMM radar precipitation features
Contiguous areas with near-surface rain rate > 0
Use features with maximum height of 30 dBZ > 6
km
Size equivalent to smallest and largest 50% of
MCSs
Years included: 1998-2012
convective rain volume
convective rain fraction 
convective stratiform rain volume
TRMM RPF data obtained from
University of Utah TRMM
database. Details in Liu et al. 2008
Peak convective rain
fraction at end of
break period
Lower convective rain
fraction in large
precipitation features
Conclusions
Larger, more connected, and more numerous
MCSs during MJO active period
Peak lightning just prior to active period (except
over SPCZ)
Lower lightning
densities and lower
convective rain
fractions during
active period
Higher lightning
densities in SMCSs
The End
This research was supported by NASA
grant NNX10AM28G and DOE grant DESC0008452.