MET4994_5994_RS_Lec24_S11

MET4994_5994_RS_Lec24_S11 - MET MET 4994 Remote Sensing:...

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MET 4994 Remote Sensing: Radar and Satellite Meteorology MET 5994 Remote Sensing in Meteorology Lecture 24: March 21, 2011 1. Z-R relationships, Hail, and Attenuation 2. Spaceborne Weather Radar: TRMM and CloudSat
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Raindrop Size Distributions (RSDs) 66 0 () ii z N D D dD N D  33 0 ( ) ( ) i i i R N D V D D dD NV D where V(D) is the terminal fall velocity of raindrops, which is approximately proportional to D 0.5 to D 1 for raindrops and frozen hydrometeors depending on their sizes and habits, etc. (Rodgers and Yau 1989; Pruppacher and Klett, 1997). Rain rate: Radar Reflectivity:
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Marshall Marshall-Palmer Drop Palmer Drop-size Distribution size Distribution 0 D d N N e where N 0 =8000/(m 3 mm). D is drop diameter (mm). 0.21 4.1 R Where R is rainrate in mm/h. DSD can be obtained for any specific rain rate. Reflectivity can be derived from DSD.
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Z-R Relationships R Relationships b z AR where z is the radar reflectivity factor (mm 6 /m 3 ), R is rain rate (mm/h), and A and b are empirical constants. Marshall-Palmer Z-R relationship: Using experimentally measured DSD to determine the empirical power-law Z-R relationship: 1.6 200 zR Z-R relationships are different for different meteorological conditions.
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Hail Definition: Hail is defined as precipitation in the form of ice that has a diameter of at least 5 mm. Hail ranges from 5 mm to about 10 cm in diameter. Hail occurs almost always in thunderstorms, but can fall from rainstorms. 85 % of all thunderstorms contain hail at least during part of their lives.
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Reflectivity for hail Rain: usually 20-50 dBZ (sometime could go up to 55 dBZ) Hail: a general rule: reflectivity>= 60 dBZ, definitely hail; 50-55 dBZ, possible hail Reflectivity from hail: 1) if outside is wet, then reflectivity is high. 2) Almost all hailstones are in Mie region for 3-cm and 5-cm radars. For 10-cm radar, small hail is in Rayleigh region, but large hail is in Mie region
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Severe thunderstorms over South Dakota, July 23, 2010 The giant hailstone that fell from a supercell at the town of Vivian, South Dakota, on July 23, 2010, had a record- breaking diameter of eight inches.
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Cross section
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Radar images at Aberdeen SD around 23Z on July 23 (0.5, 0.9, 1.3, 1.8 degree elevation angles)
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MET4994_5994_RS_Lec24_S11 - MET MET 4994 Remote Sensing:...

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