R. A. Houze, Jr., R. A. Houze, Jr., U. RomatschkeU. RomatschkeK. L. RasmussenK. L. Rasmussen

R. A. Houze, Jr., R. A. Houze, Jr., U. RomatschkeU. RomatschkeK. L. RasmussenK. L. Rasmussen

AGU Fall Meeting, Remote Sensing of Natural Hazards, San Francisco, 9 Dec 2011AGU Fall Meeting, Remote Sensing of Natural Hazards, San Francisco, 9 Dec 2011

Mesoscale Aspects Mesoscale Aspects of Storms Producing of Storms Producing Floods over Arid Floods over Arid MountainsMountains

University of WashingtonUniversity of Washington

"Almost 20 million people need shelter, food and emergency care. That is more than the entire population hit by the Indian Ocean tsunami, the Kashmir earthquake, Cyclone Nargis, and the earthquake in Haiti—combined.”Secretary-General Ban Ki-moonAugust 2010

"Almost 20 million people need shelter, food and emergency care. That is more than the entire population hit by the Indian Ocean tsunami, the Kashmir earthquake, Cyclone Nargis, and the earthquake in Haiti—combined.”Secretary-General Ban Ki-moonAugust 2010

2000 lives lost, extensive livestock, household, infrastructure & agricultural ($20B)2000 lives lost, extensive livestock, household, infrastructure & agricultural ($20B)

Recent papers:

• Webster et al. (2011, GRL)• Houze et al. (2011, BAMS)

Synoptic time sequence…

700 mb wind (~3 km)700 mb wind (~3 km)

LL LL LLLL

HH

Water vapor anomaly500 mb windWater vapor anomaly500 mb wind

Rain

ECMWF Ensemble Forecast analyzed by Webster et al. (2011)

• 51 Ensemble members• 50/80 km resolution• Compared to CMORPH

precipitation product

A COMPARISON OF RAINFALL IN 2008 AND 2010:

• 2010 produced devastating floods but was not an outlier meteorologically

• The hydrological uniqueness came because of the number of prior extreme events over the mountainous north, run-off due to drought in 2009, deforestation, and the TYPE OF STORM

Webster et al. 2011

Monsoon Mean Rainfall Climatology

Webster et al. 2011

Webster et al. 2011

Summary of predictions of major July rain events in Pakistan

The type of storm matters…

• TRMM climatology shows different kind of rainstorms in eastern vs western Himalayan region

Deep Convective

Cores

Wide Convective

Cores

BroadStratiform

Regions

Climatology of extreme convective features shown by TRMM for 10 years of data

Broad stratiform precipitation occurred over the mountains of Pakistan

Broad stratiform!

Floods!

Houze et al., BAMS 2011

17:09 UTC15:31UTC

Could the storm type have been anticipated?

Normal

Normal 500 mb anomaly patterns for South Asian storms observed by TRMM

Isolated deep convection

Nor

mal

Normal

Isolated deep convection

Broadstratiform

Normal 500 mb anomaly patterns for South Asian storms observed by TRMM

500 mb pattern 28 July 2010: very abnormal

Nor

mal

Normal

Isolated deep convection

Broadstratiform

500 mb pattern 28 July 2010: very abnormal

500 mb pattern 28 July 2010 was very abnormal

NOT NORMAL

NORMAL

BroadBroadstratiformstratiform

BroadBroadstratiformstratiform

Conclusions from Pakistan

• The probability of major rain periods over The probability of major rain periods over Pakistan was predictable ~7-10 days in Pakistan was predictable ~7-10 days in advanceadvance

• Not every predicted rain event produced Not every predicted rain event produced floodsfloods

• The type of storm mattered—the flooding The type of storm mattered—the flooding storms had mesoscale stratiform storms had mesoscale stratiform characteristics normally seen only in storms characteristics normally seen only in storms far to the eastfar to the east

• The possibility of such cloud systems The possibility of such cloud systems occurring in the west could be seen in the occurring in the west could be seen in the forecast wind pattern and from a knowledge of forecast wind pattern and from a knowledge of the satellite climatologythe satellite climatology

Leh, India, August 2010300 casualties due to flood in a high altitude valley of the Indus River

1200

0200

1200

0200

1200

0200 Flash flood at Leh

Afternoon convective scales grew upscale to form a

mesoscale system that moved off the plateau and fed on low-

level moisture

Rasmussen and Houze 2011

Could remote sensing have identified this as a

flood case?

Deep Convective

Cores

Wide Convective

Cores

BroadStratiform

Regions

Satellite climatology shows occurrence of wide convective systems or systems with broad stratiform regions to be extremely rare

Conclusions from Leh

• The flood producing storms were squall lines The flood producing storms were squall lines of mesoscale proportionsof mesoscale proportions

• The squall lines fed on moisture from low The squall lines fed on moisture from low levels when they moved off the Tibetan levels when they moved off the Tibetan PlateauPlateau

• Such storm are rare over the Tibetan PlateauSuch storm are rare over the Tibetan Plateau

• Again, a satellite climatology of storm type for Again, a satellite climatology of storm type for the region would help to anticipate such an the region would help to anticipate such an event.event.

EndEndThis research was supported byThis research was supported by

NSF grants ATM-0820586 and NASA grant NNX10AH70GNSF grants ATM-0820586 and NASA grant NNX10AH70G