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TEMPLATE DESIGN © 2008
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Combining IR and Lightning for Enhanced Geostationary Satellite Rain Estimates
Nai-Yu Wang, Yalei You ESSIC/CICS, University of Maryland, College Park, MD. Email: [email protected]
Lightning-enhanced Infrared Rainfall Estimates from TRMM 4. Geostationary Himawari-8 and Ground Lightning-enhanced Infrared
Rainfall Estimates
2. IR-based C/S Technique (CST) (Adler and Negri , 1988)
3. Lightning-enhanced IR CST
(Xu, Adler, and Wang, 2013, 2014)
5. Next Steps
1. ABSTRACT
A. Conv. cores w/o lightning in mature systems are removed; B. Conv. areas (with flashes) missed by CST are added.
A. Conv. core defined by local Tb minima that pass slope test B. Conv. core area is a function of Tb minima.
Lightning is very valuable in helping IR to correctly
identify convective
rainfall locations for
organized systems
CST C/S
Radar C/S
IR Tb + lightning
CST C/S CST + L C/S
Radar C/S IR + L
Precipitation estimates from geostationary satellites provide the rapid temporal update desired by the operational meteorologists to capture the growth and decay of precipitating cloud systems on a scale of several kilometers. The upcoming launch of the Geostationary Operational Environmental Satellite-R Series (GOES-R) ushers a new era of geostationary satellite with the 16 channel Advanced Baseline Imager (ABI) and the Geostationary Lightning Mapper (GLM) and the ability to take full-disk images of Earth at five-minute intervals. A combined IR and lightning convective features and precipitation algorithm for the US National Weather Service Pacific Region is being developed using geostationary JMA’s Himawari-8 infrared and ground lightning network GLD360 lightning observations in preparation for GOES-R. Following the heritage of an IR-lightning combined precipitation algorithm over land (Xu, Adler, and Wang 2013, 2014), the Pacific Ocean region IR and lightning convective feature and precipitation algorithm uses a combination of an IR-based C/S technique (CST) and lightning information to identify deep convection cores, and estimates rainfall rates from IR brightness temperatures and lightning flash rates. The technique works well over land in summer time deep convective storms. However, over tropical ocean where rainfall systems are smaller and shallower in vertical extent, techniques such as CST (and others) have limiting applications over the ocean. Further more, the utility of Lightning as a proxy for deep convection is limited over ocean due to scarce of lightning. This study presents an overview of an oceanic IR-lightning Convective feature and precipitation algorithm, case studies, and provides some thoughts on the next step improvements.
Southeast U.S.
Hawaii, Pacific Ocean
IR + L
CST C/S CST + L C/S
PMW C/S Pro: Lightning is valuable in
helping CST to identify convective
rainfall locations for
organized systems
Con: Convective cores w/o
lightning are falsely
removed
CST C/S CST + L C/S
CST C/S Rainrate CST + L C/S Rainrate
Guam Radar Guam Radar + GLD360
Hawaii, Pacific Ocean
Himawari-8 Ch13
Black crosses are GLD360 lightning flashes
Red : convective Blue: other rain
A. Convective rainfall rate: a function of IR brightness temperature and lightning flash rate
Considerations on the next step improvements (over ocean) 1. Better use of lightning information as the means to
identify/remove convective cores in conjunction with IR
2. How to handle Shallow convections w/o lightning and warm rain
3. Additional use of cloud microphysical information
6. References Adler, R.F. and A. Negri, 1988: A satellite Infrared Technique to estimate Tropical Convective and Stratiform Rainfall , J.. Appl. Meteor. Climatol., 27,30-51. Xu, W., R. F. Adler, and N.-Y. Wang, 2013: Improving Geostationary Satellite Rainfall Estimates Using Lightning Observations: Underlying Lightning- Rainfall Relationships. J. Appl. Meteor. Climatol., 52, 213-229. Xu, W., R. F. Adler, and N.-Y. Wang, 2014: Combining Satellite Infrared and Lightning Information to Estimate Warm Season Convective and Stratiform Rainfall. J.. Appl. Meteor. Climatol., doi:10.1175/JAMC-D-13-069.1 .