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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: Nai-Yu.Wang@noaa.gov

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 .