Radar Observations of Convection in NAMMA...Radar Observations of Convection in NAMMA Robert...
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Radar Observations of Convection in NAMMA Robert Cifelli 1 , Timothy Lang 1 , Steven A. Rutledge 1 , Bradley Smull 2 , Bob Bowie 1 , John Gerlach 3 1 Colorado State University 2 University of Washington 3 NASA Wallops Flight Facility Goals for TOGA Radar Observations in NAMMA • Collect radar data and assist in guidance of DC-8 during field phase • Analyze precipitation and circulation structures within maritime MCSs in the vicinity of the Cape Verde islands and describe the progression of their structure and behavior as they transition from the African continent to a more maritime environment • Document kinematic, microphysical, and precipitation features, internal to these MCSs, that are relevant to tropical cyclogenesis Acknowledgements This work is supported by NASA NAMMA grant NNX06AC11G under the supervision of Dr. Ramesh Kakar NASA TOGA Radar Deployment Cape Verde Islands TOGA Radar DC-8 Dakar 650 km • TOGA location 100m above coastline outside Praia on south coast of Sao Tiago • The site provided an unobstructed view east-southwest where most precipitation activity was observed • TOGA: C-band (wavelength 5.3 cm) • Deployment:15 August - 16 September, 2006 in Praia, Republic of Cape Verde • Data Collected: Unfiltered reflectivity (ZT), filtered reflectivity (DZ), radial velocity (VR), and spectral width (SW) • Scan strategy: 1-tilt (0.8°) surveillance scan covering 360° azimuth(300 km maximum range) And one of the following… 18-tilt (0.8°-29°) scan covering 360° azimuth (150 km maximum range) -used most often 20-tilt (0.8°-53°) scan covering 360° azimuth (150 km maximum range) -used occasionally 21-tilt (0.8°-54°) scan covering 360° azimuth (150 km maximum range) -used rarely • Scans repeat on a 10-minute cycle • Radar operated nearly continuously during deployment 9,000 scans collected View NW of TOGA on a clear day View NW of TOGA on a dust day Flash flooding around Praia during 3 September event View NE of TOGA with local wildlife in foreground Photo by Brad Smull Photo by Nathan Gears Photo by Brad Smull Photo by Tim Lang TRMM Background Climatology • The Cape Verde Islands are in a transition region between intense land-based convection over Africa and weaker maritime convection over the open ocean Approximate region of TOGA coverage TOGA Radar QC Issues QC algorithm approach •Ground clutter and side lobes removed using a clutter template for each sweep • Multiple trip echo removed using a VR mask •Sea clutter removed using vertical reflectivity gradient threshold • Calibration bias determined from comparisons between TOGA and TRMM PR • Based on 4 overpass intercomparisons (22 August, 3 September, 12 September, and 14 September), TOGA is 4.0 dB (±2.2 dB) high relative to TRMM PR • The radar data contains multiple artifacts that must be removed before it can be used for research analyses Sea clutter Ground clutter 2nd trip Blocked sectors Side lobes TOGA PPI during suppressed period showing spurious echo features •Apply calibration bias offset •Apply GATE attenuation correction •Version 1 data set to be released summer 2007 Example TRMM PR - TOGA comparison on14 September Plot courtesy of Steve Nesbitt 1 2 3 4 5 14 Aug. 16 Sept. 21 Aug. 28 Aug. 4 Sept. 11 Sept. 15 Aug (11Z) - 15 Aug (20Z) •EVAD scans 21 Aug (16Z) - 22 Aug (16Z) •“Pre-Debbie” • Good TRMM overpass at 10:35Z 22 Aug. 2 Sept (9Z) - 4 Sept (0Z) •DC-8 coordination 9 Sept (6Z) - 10 Sept (9Z) 6 14 Sept (9Z) - 16 Sept (16Z) •Flash flooding in Praia •Good TRMM overpass at 13:51Z 14 Sept. 12 Sept (9Z) - 13 Sept (20Z) •“Pre-Helene” •DC-8 coordination •Flash flooding in Praia •Fair TRMM overpass at 23:55Z 12 Sept. •EVAD scans Major Activity* Time Line * Significant echo within 150 km of TOGA exhibiting MCS scale structure and lasting at least 6 hours Observations of Convection Observed Features of Interest in Major Events: • Classic leading line convection - trailing stratiform MCSs • Leading stratiform - trailing convection MCSs • Narrow convective bands (> 100 km in length) with no accompanying stratiform • Orographic forced convection over islands • Broad scale cyclonic circulation and embedded vortices 3 September 2006 DC-8/TOGA Coordination METEOSAT winds/IR 1200 UTC DC-8 flight track TOGA reflectivity PPI (1230 UTC) TOGA reflectivity PPI (1540 UTC) DC-8 spiral location (1235 UTC) DC-8 dropsonde location (1250 UTC) Large-scale cyclonic circulation Photo by Brad Smull 12-13 September “Pre-Helene” Convection TOGA reflectivity CAPPI on 13 Sept.( 0541 UTC) Leading line-trailing stratiform MCS TOGA reflectivity PPI on 13 Sept. (0141 UTC) Low-level jet TOGA VR PPI 0515 UTC METEOSAT winds/IR 0600 UTC “Pre-Helene” circulation Cyclonic circulation signature TOGA VR PPI on 12 Sept.(1541 UTC)
Transcript of Radar Observations of Convection in NAMMA...Radar Observations of Convection in NAMMA Robert...
Radar Observations of Convection in NAMMARobert Cifelli1, Timothy Lang1, Steven A. Rutledge1, Bradley Smull2, Bob Bowie1, John Gerlach3
1 Colorado State University2 University of Washington3 NASA Wallops Flight Facility
Goals for TOGA Radar Observations in NAMMA
• Collect radar data and assist in guidance of DC-8during field phase
•Analyze precipitation and circulation structureswithin maritime MCSs in the vicinity of the CapeVerde islands and describe the progression of theirstructure and behavior as they transition from theAfrican continent to a more maritime environment
• Document kinematic, microphysical, andprecipitation features, internal to these MCSs, thatare relevant to tropical cyclogenesis
Acknowledgements
This work is supported by NASA NAMMA grantNNX06AC11G under the supervision of Dr.Ramesh Kakar
Photo by Nathan Gears
NASA TOGA Radar Deployment
Cape Verde Islands
TOGA Radar
DC-8
Dakar ̃ 650 km
• TOGA location ̃100m above coastline outside Praia on south coastof Sao Tiago
• The site provided an unobstructed view east-southwest wheremost precipitation activity was observed
•TOGA: C-band (wavelength 5.3 cm)
•Deployment:15 August - 16 September, 2006 in Praia, Republic of Cape Verde
•Data Collected: Unfiltered reflectivity (ZT), filtered reflectivity (DZ), radial velocity (VR), andspectral width (SW)
•Scan strategy:1-tilt (0.8°) surveillance scan covering 360° azimuth(̃300 km maximum range)And one of the following…
18-tilt (0.8°-29°) scan covering 360° azimuth (̃150 km maximum range) -used most often 20-tilt (0.8°-53°) scan covering 360° azimuth (̃150 km maximum range) -used occasionally21-tilt (0.8°-54°) scan covering 360° azimuth (̃150 km maximum range) -used rarely
•Scans repeat on a 10-minute cycle
•Radar operated nearly continuously during deployment ̃ 9,000 scans collected
View NW of TOGA on a clear day
View NW of TOGA on a dust dayFlash flooding around Praia during 3September event
View NE of TOGA with local wildlifein foreground
Photo by Brad Smull Photo by Nathan Gears Photo by Brad Smull
Photo by Tim Lang
TRMM Background Climatology
•The Cape Verde Islands are in a transition region between intense land-basedconvection over Africa and weaker maritime convection over the open ocean
Approximateregion ofTOGAcoverage
TOGA Radar QC Issues
QC algorithm approach
•Ground clutter and side lobes removed using aclutter template for each sweep• Multiple trip echo removed using a VR mask•Sea clutter removed using vertical reflectivitygradient threshold
•Calibration bias determined fromcomparisons between TOGA and TRMMPR•Based on 4 overpass intercomparisons(22 August, 3 September, 12September, and 14 September), TOGAis 4.0 dB (±2.2 dB) high relative toTRMM PR
• The radar data contains multiple artifactsthat must be removed before it can beused for research analyses
Sea clutter
Ground clutter
2nd trip
Blocked sectors
Side lobes
TOGA PPI during suppressed period showingspurious echo features
•Apply calibration bias offset•Apply GATE attenuation correction•Version 1 data set to be released summer 2007
Example TRMM PR - TOGA comparison on14September
Plot courtesy of Steve Nesbitt
Photo by Tim Lang
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14 Aug.
16 Sept.
21 Aug.
28 Aug.
4 Sept.
11 Sept.
15 Aug (11Z) - 15 Aug (20Z)•EVAD scans
21 Aug (16Z) - 22 Aug (16Z)•“Pre-Debbie”• Good TRMM overpass at 10:35Z 22 Aug.
2 Sept (9Z) - 4 Sept (0Z)•DC-8 coordination
9 Sept (6Z) - 10 Sept (9Z)
614 Sept (9Z) - 16 Sept(16Z)•Flash flooding in Praia•Good TRMM overpass at13:51Z 14 Sept.
12 Sept (9Z) - 13 Sept (20Z)•“Pre-Helene”•DC-8 coordination•Flash flooding in Praia•Fair TRMM overpass at 23:55Z12 Sept.•EVAD scans
Major Activity* Time Line
* Significant echo within 150 km of TOGA exhibiting MCS scale structure and lasting at least6 hours
Observations of Convection
Observed Features of Interest in Major Events:
•Classic leading line convection - trailing stratiformMCSs
• Leading stratiform - trailing convection MCSs
•Narrow convective bands (> 100 km in length)with no accompanying stratiform
•Orographic forced convection over islands
•Broad scale cyclonic circulation and embeddedvortices
3 September 2006DC-8/TOGA Coordination
METEOSAT winds/IR 1200 UTC DC-8 flight track
TOGA reflectivity PPI (1230 UTC) TOGA reflectivity PPI (1540 UTC)
DC-8 spiral location(1235 UTC)
DC-8 dropsondelocation (1250 UTC)
Large-scale cyclonic circulation
Photo by Brad Smull12-13 September“Pre-Helene” Convection
TOGA reflectivity CAPPI on 13Sept.( 0541 UTC)
Leading line-trailingstratiform MCS
TOGA reflectivity PPI on 13Sept. (0141 UTC)
Low-level jet
TOGA VR PPI 0515 UTC
METEOSAT winds/IR 0600 UTC
“Pre-Helene” circulation Cyclonic circulation signature
TOGA VR PPI on 12Sept.(1541 UTC)
