Date post: | 21-Jan-2016 |
Category: |
Documents |
Upload: | alfred-murphy |
View: | 216 times |
Download: | 0 times |
Relationships between lightning flash rates over the tropics and subtropics and the vertical
structures of precipitation radar reflectivity
Chuntao Liu
Department of Atmospheric sciences, University of Utah
Contributors:Edward Zipser1 , Daniel Cecil2
1. University of Utah2. University of Alabama at Huntsville
Riming electric charge separation
Takahashi and Miyawaki, 2002, JAS
Keys :
Graupel
Temperature
Super-cooled liquid water
Why there is a relationship between radar reflectivity and lightning flash?
Define precipitation features using TRMM Precipitation Radar
Radar Precipitation Features (RPFs)
Contiguous area with rainfall
Properties of precipitation features
Flash rateTemperature at 20, 30, 40 dBZ
echo topsMaximum reflectivity at temperatures
Area of 20, 30, 40 dBZ at temperaturesVolume of 20, 30 40 dBZ at -5oC - -35oC
IWC of 20, 30 40 dBZ at -5oC - -35oC
PR echo top height (km)
Population of RPFs and those with lightning
• 1998-2010
Land Coast Open ocean All 36S-36N
RPF 3.7 million 6.4m million 11.8 million 22.2 million
With flash 11.5% 2.6% 0.5% 3%
Correlation between radar reflectivity vs. flash rate in precipitation features
Echo top temperature vs. Flash rate
Correlation coefficient to flash rate in precipitation features
Ocean Coast Land All 36S-36N
Maximum 20 dBZ echo top Temperature
-0.12 -0.18 -0.27 -0.24
Maximum 30 dBZ echo top Temperature
-0.30 -0.36 -0.40 -0.38
Maximum 40 dBZ echo top Temperature
-0.49 -0.50 -0.49 -0.50
Correlation coefficient to flash rate in precipitation features
area of reflectivity at temperatures vs. Flash rate
Solid : land dotted: ocean
area of reflectivity at temperatures vs. Flash rateauto-correlation among different part of storms removed
Solid : land dotted: ocean
Regional variation of correlations (I)Correlation coefficients
Regional variation of correlations (II)Slope of linear relationship
Summary• Flash rate is best correlated with the volume of the high reflectivity (> 30 dBZ) in the mixed phase region, confirming the importance of the presence of large particles in the charging process.
• More flashes are generated over land than over ocean given the same volume of 30-35 dBZ in the mixed-phase region.
• There are large regional differences in the correlations between radar reflectivity properties vs. flash rate.
• Even with the similar radar reflectivity profiles to the oceanic systems, it is still easier to have lightning flashes over Amazon. Other factors must play important roles besides the graupel at mixed phase region in the lightning generation.
2-D histogram of RPFs and probability with lightning
Temperature of 20 dBZ echo top vs. Temperature of 30 dBZ echo top
Regional variation of lightning probability in precipitation systems
Correlation coefficient to flash rate in precipitation features
maximum reflectivity at altitudes vs. Flash rate
Correlation coefficient to flash rate in precipitation features
area of reflectivity at temperatures vs. Flash rate
Solid : land dotted: ocean