Transcript Document

RADAR OBSERVATIONS DURING NAME 2004
PART I: DATA PRODUCTS AND QUALITY CONTROL
JP3J.5
Timothy J. Lang, Rob Cifelli, Lee Nelson, Stephen W. Nesbitt, Gustavo Pereira, and Steven A. Rutledge
Colorado State University, Fort Collins, Colorado
David Ahijevych and Richard E. Carbone
National Center for Atmospheric Research, Boulder, Colorado
1. Network Design and Radar Operations
4. S-Pol Blockage Correction
Major Blocks
Three radars in core Monsoon region
(NAME Tier I)
Ocean
Mountain
Clutter
Further complicated by multiple
blocks along same ray.
Minor
Block
Mean clear-air power over several hours
by azimuth, 0.8° elevation
S-Pol 24-h Ops 7/8-8/21; Two Modes
Climatology
Used most frequently; 200-km range
Full-volume 360s, complete in 15 min
Rain-map angles (0.8,1.3,1.8°) & 0.0°
Storm Microphysics
70-80 hours total spread over ~35 cases
Usually 150-km range
2-3 PPIs with 0-1 RHIs in 15 min
360s @ rain-map angles (0.8,1.3,1.8°)
SMN Upgrade and 24-h Ops
Guasave
Upgrade completed 6/10 (recorded into Fall)
Multiple PRFs; >200-km range
Single sweep at 0.5, 1.0, or 1.5° (varied)
Data recording outage 7/22-31
Mtns
Ocean
Block
ZH scatter plot for KDP between 1 and 2
° km-1 by azimuth (date range 8/2-9)
Los Cabos
Upgrade completed 7/15
Multiple PRFs; >200-km range
Single sweep at 0.6°
Data recording only thru 8/14
Threshold on NCP, ZH, and Power
●Hand edit insects, clutter
●Clutter map used to help eliminate clutter at Guasave
●Visual and statistical gate-to-gate intercomparison
w/ S-Pol to determine calibration offset for ZH
●Correct Z
H for gaseous attenuation (Battan 1973)
●Correct Z
H for rain attenuation using GATE method (Patterson et al. 1979)
●Used same Z-R as S-Pol
-1 to mitigate ice contamination
●Capped rain rates at ~230 mm h
PPI of blockage-corrected ZH (left) and a
QC flag showing angle used (right) – 0.8°
(greens), 1.3° (yellows), 1.8° (reds)
Example 2-D composite ZH
Due to the self-consistency
between polarimetric radar
variables in rain (Scarchilli et al.
1996), we expect that, over a
small range of KDP, ZH should also
vary over a small range. Exploit
this by plotting ZH values as a
function of azimuth for a given
range of KDP.
Significant depressions in ZH
signal blocks, the magnitude of
which is the offset that needs to
be added to ZH at that particular
azimuth.
Use higher elevation angles to fill
In for severe blocks and filtered
clutter. Goal is to create a single
low-level sweep with good ray-toray consistency.
●
3. Basic SMN Quality Control
Attempt recover using
experimental specific differential
phase technique.
Due to multiple blocks along rays,
need to breakdown the azimuthZH scatter plots by range.
2. Basic S-Pol Quality Control
Threshold on HV, (DP) – noise, clutter
●Threshold on Z , Z
H
DR – insects
●Threshold on LDR, 
DP – second trip
● 21-pt (3.15 km) finite impulse response (FIR) filter on 
DP
● Adaptive linear fit to calculate K
DP (i.e., higher ZH, fewer pts used)
● Z , Z
H
DR rain attenuation correction via DP method (Carey et al. 2000)
● Z
H corrected for gaseous attenuation (Battan 1973)
● Rainfall from CSU blended polarimetric algorithm (Cifelli et al. 2002)
(Base Z-R: Z=221R1.25 from gages; Used pol-tune as guide)
● Fuzzy hydrometeor ID (FHC) from CSU method (Tessendorf et al. 2005)
Low-level sweeps from all three radars were
organized into groups every 15 minutes (when
available). They were then interpolated to 2-D
grids containing near-surface ZH and rainfall
fields. Also, each grid point lists height MSL, to
aid users in making the decision to consider the
point in statistics (e.g., rain rate estimate above
the freezing altitude).
Much of the land portions of lowelevation sweeps (< 2° elevation)
were blocked at S-Pol.
Network covered Gulf of California,
Sierra Madre Occidental, Coastal
Plain, Baja Peninsula, Pacific Ocean
S-Pol – S-Band, Polarimetric, Doppler
SMN – Cabo and Guasave radars
(C-Band, Doppler)
6. Regional Radar Composite Creation
Currently do not correct ZDR – set
to missing in blocks
5. Version 2 Plans
Version 1 blockage correction currently only corrects up to 5 dB before
utilizing higher angle (1.3° or 1.8°; 1.8° never blocked more than 5 dB).
KDP using Version 1 method is very noisy; Version 2 fields are much
smoother due to improvements in and greater restrictions on KDP
computation, greatly reducing spurious values.
●
In Version 2, will correct up to 35 dB before moving to higher scan –
better reliance on low-level scans. Version 2 QC will also include
improvements to Z-R estimates, including polarimetric tuning and
stratiform/convective partitioning of Z-R. Also, SMN attenuation
correction will be improved and radar rain estimates validated by gages.
Version 2 NAME radar data will be available later this winter. Version 1
available now, with no validation of rain estimates.
Before converting to a lat/lon grid, the data
along each ray were smoothed and resampled
to a more sparse array. Where radar gates
from different radars overlapped, the lowest
gate took precedence and higher gates were
eliminated.
Remaining gates were combined and
interpolated to a regular lat/lon grid. An inversedistance weighting method was employed to
produce the interpolated values.
A circular smoothing filter also was applied.
Example rainfall product:
1-day total (17 July 2004)
Grids are available at the following spacings:
0.01º, 0.02°, and 0.05° (~1, 2, and 5 km), at 15minute intervals during NAME 2004.
7. Data Distribution
Version 1 2-D regional radar composites (0.02° and 0.05° spacing)
have been placed on the UCAR/JOSS NAME FTP server. The 0.01°
grids are available by request. Quick-look composite images available
at http://radarmet.atmos.colostate.edu/name/composites/. Now
creating 2-D Version 2 grids, along with 3-D grids containing vertical
information from S-Pol, including FHC.Available soon.
8. Acknowledgments
The engineering side of the S-Pol deployment was led by Don Ferraro of NCAR Earth Observing
Laboratory (EOL). Jon Lutz, also of NCAR EOL, provided engineering oversight for the S-pol
operation and led the SMN radar upgrade and data collection efforts. He was assisted by Arturo
Valdez-Manzanilla of Juarez University and by Armando Rodriguez of SMN. We thank all the other
NCAR engineers, technicians and field scientists for contributing to the successful S-pol operation, as
well as Robert Bowie of the CSU-CHILL Radar Facility staff who also worked at S-pol. Bob Rilling of
NCAR EOL led initial quality control and distribution of the S-Pol and SMN radar data. Further data
quality control efforts, as outlined here, were assisted by Chad Chriestenson of CSU. Sounding data
were obtained from Richard Johnson and Paul Ciesielski of CSU. We thank the federal and local
government agencies in Mexico, in particular SMN, for their cooperation in making the S-Pol
deployment and the SMN upgrades possible. The SMN radar upgrades, S-Pol deployment, radar
operations, and ensuing research were funded by the National Oceanic and Atmospheric
Administration (NOAA; SMN radars) and the National Science Foundation (NSF; S-Pol). NCAR is
funded by NSF.
9. References
Battan, L. J., 1973: Radar Observation of the Atmosphere, University of Chicago Press, 324 pp.
Carey, L. D., S. A. Rutledge, D. A. Ahijevych, and T. D. Keenan, 2000: Correcting propagation effects in C-Band polarimetric radar observations of tropical convection using
differential propagation phase. J. Appl. Meteorol., 39, 1405–1433.
Cifelli, R., W. A. Petersen, L. D. Carey, and S. A. Rutledge, 2002: Radar observations of the kinematic, microphysical, and precipitation characteristics of two MCSs in
TRMM-LBA. J. Geophys. Res., 29, 10.1029/2000JD0000264.
Patterson, V. L., M. D. Hudlow, P. J. Pytlowany, F. P. Richards, and J. D. Hoff, 1979: GATE radar rainfall processing system. NOAA Tech. Memo. EDIS 26, NOAA,
Washington, DC, 34 pp. [Available from National Technical Information Service, Sills Building, 5285 Port Royal Road, Springfield, VA 22161.].
Scarchilli, G., E. Gorgucci, V. Chandrasekar, and A. Dobaie, 1996: Self-consistency of polarization diversity measurement of rainfall. IEEE Trans. Geosci. Remote Sens., 34,
22-26.
Tessendorf, S.A., L.J. Miller, K.C. Wiens, and S.A. Rutledge, 2005: The 29 June 2000 supercell observed during STEPS. Part I: Kinematics and microphysics. J. Atmos. Sci.,
in press.
Contact Info: Timothy Lang, CSU Atmospheric Science, Ft Collins, CO 80523
(970) 491-6944, [email protected]