Passive Microwave Data Tools Derek Wroe Acknowledgements: Naval Research Laboratory Hurricane Specialist Chris Velden, Cooperative Institute for Meteorological Satellite Studies Central Pacific Hurricane Center Derrick Heardon, Cooperative Institute for Meteorological Satellite Studies
Agenda • Microwave imagery interpretation review • CIMSS & CIRA AMSU Intensity Algorithm • CIMSS Satellite Consensus (SATCON)
Passive Microwave Data • Tropical cyclone (TC) monitoring requires the use of multiple satellites and sensors to accurately assess TC location and intensity. • Geostationary satellite data provide the bulk of TC information, but upper-level cloud obscurations limit these important data. • Passive microwave data and imagery from polar orbiting satellites can provide key storm structural details and offset many of the VIS/IR spectral problems. • The ability to view storm rainbands, eyewalls, impacts of shear, and exposed low-level circulations, whether it is day or night, makes passive microwave data a significant tool for the satellite analyst.
Passive Microwave Data Temporal & Spatial Issues
Microwave Review: 85-89GHz • TC core and rainbands in 85 - 89 GHz channels marked by dramatically lowered equivalent blackbody brightness temperatures (Tb) caused by scattering from precipitation-size ice hydrometeors – Cold: High portions of deep convection (ice!) – Warm: Low cloud fields
Microwave Review: 36-37GHz • TC core and rainbands in 36 - 37 GHz channels marked by elevated Tb caused by absorption from mainly liquid water – Warm: Rain at low levels – Note: Eye often smaller than in 85 - 89 GHz
Center Finding
Center Finding
Center Finding
Center Finding
Center Finding
Center Finding
Center Finding
Center Finding
Center Finding
Microwave Imagery Availability • Available from Naval Research Laboratory Monterey, CA: – http://www.nrlmry.navy.mil/tc_pages/tc_home.html
Microwave Data in ADT • Uses the 85GHz brightness temperature signal to deduce the Eyewall temperatures vigor and organization of the developing eyewall/eye, and calculate an intensity score • If thresholds are exceeded, T number of 4.3 or 5.0 is overridden in ADT Warmest eye pixel
AMSU Intensity Algorithm • A dvanced M icrowave S ounding U nit on NOAA 15 -19, METOP, and Aqua • Channels 5-8 in the 54 - 55 GHz range measure upper level warm core aloft C IM S S /N E S D IS -U S A F /N R L A M S U T C In te n s ity E s tim a tio n : • Estimate MSLP via H U R R IC A N E IO K E T h u rs d a y 2 4 a u g 0 6 T im e : 0 2 0 5 U T C L a titu d e : 1 8 .3 1 L o n g itu d e : -1 7 1 .1 1 hydrostatic assumptions S to rm p o s itio n c o rre s p o n d s to A M S U -A F O V 3 [1 < ---> 3 0 ] ----------------------------------------------------------------- • Algorithm needs RMW & | E s tim a te d M S L P : 9 7 5 h P a | E s tim a te d M a x im u m S u s ta in e d W in d : 8 0 k ts | E s tim a te C o n fid e n c e : F a ir ( ± 1 0 m b ± 1 2 k ts ) outermost isobar input ----------------------------------------------------------------- S to rm is s u b -s a m p le d : B ia s c o rre c tio n a p p lie d is -6 h P a ( ~ 1 5 0 C h a n n e l 8 h P a ) T b A n o m a ly : 1 .4 1 (c h a n n e l u s e d fo r e s tim a te ) C h a n n e l 7 ( ~ 2 5 0 h P a ) T b A n o m a ly : 0 .6 9 R M W : 2 8 k m R M W S o u rc e is : T P C E n v iro n m e n ta l P re s s u re : 1 0 1 1 (T P C ) S a te llite : N O A A -1 6 A T C F d a ta fo r M o n th : 0 8 D a y : 2 4 T im e (U T C ): 0 6 0 0
CIMSS AMSU Intensity Algorithm • Available from CIMSS website: – http://tropic.ssec.wisc.edu/ Access AMSU Data
AMSU Channels 929hPa Ch 8 Ch 7 Ch 6 Ch 5 Hurricane Inez Sept 28 1966 (Hawkins and Imbembo)
AMSU Sensor Characteristics • Field of View (FoV) resolution varies across the scan swath due to the instrument ’ s cross-track scanning strategy • Best spatial resolution at nadir is ~ 50 km AMSU Scan Swath 80 km 80 km 50 km FOV 1 FOV 30 LIMB NADIR LIMB
AMSU Field of View C IM S S /N E S D IS -U S A F /N R L A M S U T C In te n s ity E s tim a tio n : H U R R IC A N E IO K E • Spatial resolution variability T h u rs d a y 2 4 a u g 0 6 T im e : 0 2 0 5 U T C needs to be taken into account L a titu d e : 1 8 .3 1 L o n g itu d e : -1 7 1 .1 1 S to rm p o s itio n c o rre s p o n d s to A M S U -A F O V 3 [1 < ---> 3 0 ] relative to the TC core position ----------------------------------------------------------------- in the swath. A TC core-sized | E s tim a te d M S L P : 9 7 5 h P a warm anomaly viewed at 50km | E s tim a te d M a x im u m S u s ta in e d W in d : 8 0 k ts | E s tim a te C o n fid e n c e : F a ir ( ± 1 0 m b ± 1 2 k ts ) will be better resolved then at ----------------------------------------------------------------- 80km. S to rm is s u b -s a m p le d : B ia s c o rre c tio n a p p lie d is -6 h P a C h a n n e l 8 ( ~ 1 5 0 h P a ) T b A n o m a ly : 1 .4 1 (c h a n n e l u s e d fo r • FOV provided in message e s tim a te ) C h a n n e l 7 ( ~ 2 5 0 h P a ) T b A n o m a ly : 0 .6 9 R M W : 2 8 k m R M W S o u rc e is : T P C E n v iro n m e n ta l P re s s u re : 1 0 1 1 (T P C ) S a te llite : N O A A -1 6 A T C F d a ta fo r M o n th : 0 8 D a y : 2 4 T im e (U T C ): 0 6 0 0 AMSU Scan Swath 80 km 80 km 50 km FOV 1 FOV 30 LIMB NADIR LIMB
AMSU Sub-sampling C IM S S /N E S D IS -U S A F /N R L A M S U T C In te n s ity E s tim a tio n : H U R R IC A N E IO K E • Near limb T h u rs d a y 2 4 a u g 0 6 T im e : 0 2 0 5 U T C footprint L a titu d e : 1 8 .3 1 L o n g itu d e : -1 7 1 .1 1 S to rm p o s itio n c o rre s p o n d s to A M S U -A F O V 3 [1 < ---> 3 0 ] ----------------------------------------------------------------- | E s tim a te d M S L P : 9 7 5 h P a | E s tim a te d M a x im u m S u s ta in e d W in d : 8 0 k ts • “ Bracketing ” | E s tim a te C o n fid e n c e : F a ir ( ± 1 0 m b ± 1 2 k ts ) ----------------------------------------------------------------- S to rm is s u b -s a m p le d : B ia s c o rre c tio n a p p lie d is -6 h P a C h a n n e l 8 ( ~ 1 5 0 h P a ) T b A n o m a ly : 1 .4 1 (c h a n n e l u s e d fo r e s tim a te ) C h a n n e l 7 ( ~ 2 5 0 h P a ) T b A n o m a ly : 0 .6 9 R M W : 2 8 k m R M W S o u rc e is : T P C E n v iro n m e n ta l P re s s u re : 1 0 1 1 (T P C ) S a te llite : N O A A -1 6 A T C F d a ta fo r M o n th : 0 8 D a y : 2 4 T im e (U T C ): 0 6 0 0 AMSU Scan Swath 80 km 80 km 50 km FOV 1 FOV 30 LIMB NADIR LIMB
AMSU: Warm Core Size C IM S S /N E S D IS -U S A F /N R L A M S U T C In te n s ity • Environmental pressure and E s tim a tio n : H U R R IC A N E IO K E radius of maximum winds T h u rs d a y 2 4 a u g 0 6 T im e : 0 2 0 5 U T C L a titu d e : 1 8 .3 1 L o n g itu d e : -1 7 1 .1 1 • Algorithm needs to start with S to rm p o s itio n c o rre s p o n d s to A M S U -A F O V 3 [1 < ---> 3 0 ] ----------------------------------------------------------------- an input for warm core size | E s tim a te d M S L P : 9 7 5 h P a | E s tim a te d M a x im u m S u s ta in e d W in d : 8 0 k ts | E s tim a te C o n fid e n c e : F a ir ( ± 1 0 m b ± 1 2 k ts ) • Three possible sources: ----------------------------------------------------------------- S to rm is s u b -s a m p le d : B ia s c o rre c tio n a p p lie d is -6 h P a – Automated algorithm ( ~ 1 5 0 C h a n n e l 8 h P a ) T b A n o m a ly : 1 .4 1 (c h a n n e l u s e d fo r e s tim a te ) – ADT C h a n n e l 7 ( ~ 2 5 0 h P a ) T b A n o m a ly : 0 .6 9 R M W : 2 8 k m – NHC, CPHC, or JTWC R M W S o u rc e is : T P C E n v iro n m e n ta l P re s s u re : 1 0 1 1 (T P C ) S a te llite : N O A A -1 6 A T C F d a ta fo r M o n th : 0 8 D a y : 2 4 T im e (U T C ): 0 6 0 0
CIMSS AMSU Intensity • Output: C IM S S /N E S D IS -U S A F /N R L A M S U T C In te n s ity E s tim a tio n : H U R R IC A N E IO K E – MSLP T h u rs d a y 2 4 a u g 0 6 T im e : 0 2 0 5 U T C L a titu d e : 1 8 .3 1 L o n g itu d e : -1 7 1 .1 1 – MSW S to rm p o s itio n c o rre s p o n d s to A M S U -A F O V 3 [1 < ---> 3 0 ] ----------------------------------------------------------------- • Confidence based on: | E s tim a te d M S L P : 9 7 5 h P a | E s tim a te d M a x im u m S u s ta in e d W in d : 8 0 k ts | E s tim a te C o n fid e n c e : F a ir ( ± 1 0 m b ± 1 2 k ts ) – FOV ----------------------------------------------------------------- S to rm is s u b -s a m p le d : B ia s c o rre c tio n a p p lie d is -6 h P a – Any sub-sampling? ( ~ 1 5 0 C h a n n e l 8 h P a ) T b A n o m a ly : 1 .4 1 (c h a n n e l u s e d fo r e s tim a te ) C h a n n e l 7 ( ~ 2 5 0 h P a ) T b A n o m a ly : 0 .6 9 – Quality of data R M W : 2 8 k m R M W S o u rc e is : T P C E n v iro n m e n ta l P re s s u re : 1 0 1 1 (T P C ) S a te llite : N O A A -1 6 A T C F d a ta fo r M o n th : 0 8 D a y : 2 4 T im e (U T C ): 0 6 0 0 • Note: For TC < 45 kt, algorithm has high bias of ~ 4.9 kt
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