Post on 28-Mar-2018
Radar Observations in NAMERadar Observations in NAME
Steve Rutledge,Timothy Lang,Steve Nesbitt,David Lerach,and Lee Nelson
Colorado State University
NAME Homepage:http://www.joss.ucar.edu/name
Field Programs of the Radar Meteorology Group, CSU
The North American Monsoon The North American Monsoon Experiment (W. Higgins)Experiment (W. Higgins)
• Multiyear, multi-tier research program aimed at studying the sources and limits of predictability of warm season precipitation over N. America
• Scientific Objectives:• Improve characterization of warm season convective processes in complex terrain (Tier 1)• Describe and improve simulation of mechanisms controlling intraseasonal variability of the monsoon (Tier 2)• Define the response of the warm season circulation and precipitation to slowly varying boundary conditions (Tier 3)• Improve simulation and prediction of the North American Monsoon System and its variability
Moisture Budget RegionMoisture Budget Region
NAME Radar Network
Planned●S-Pol●4 SMN Radars●SMN radars run in full-volume 360s●15-min resolution
Actual●S-Pol (7/8-8/21)●Cabo (7/15-Fall)●Guasave (6/10-Fall)●SMN radars single low-level sweep (high temporal resolution)
NCAR/NSF SNCAR/NSF S--pol pol Radar (Rutledge, Radar (Rutledge, Carbone Carbone PI’s)PI’s)
• Deployed north of Mazatlan at La Cruz
• 24/7 operation• Approx. 500 m resolution,
120-200 km range• Reflectivity, Doppler
velocity, polarimetric observations
• Coordinated with NERN raingages
• Reflectivity available in real-time
S-Pol Operations24-h Ops started 7/8, continued through 8/21
Occasional downtime for Ka-band work in preparation for RICO –Usually mid-morning precipitation minimum
Two Modes of Scanning:
“Climatology”Used most frequently200-km rangeFull-volume 360s, completed in 15-minIncludes rain-mapping angles (0.8,1.3,1.8-deg) & 0.0-deg
“Storm Microphysics”70-80 hours total spread over ~35 casesUsually 150-km range2-3 sector PPI volumes with 0-1 sets of RHIs in 15 minIncludes 360s @ rain-mapping angles (0.8,1.3,1.8-deg)
Polarimetric Radar Variables
Horizontal (V) Reflectivity (ZH, ZV) Size, concentration
Differential Reflectivity (ZDR) Size, shape, phase, ZH/ZV
Differential Phase (ΨDP)Specific Differential Phase (KDP)
LWC, shapeOblate Raindrop
Small RaindropHail/Graupel
Polarimetric Radar Variables
Linear Depolarization Ratio (LDR)Orientation, canting, melting
Correlation CoefficientMixed phase
Can use all these variables, along with temperature, in combination to infer bulk hydrometeor type within storms
H
V
Improved rainfall estimation compared to conventional radar
Fuzzy-Logic Hydrometeor ID
Hydrometeor ClassesLarge Hail (D > 2 cm; LH)Small Hail (D < 2 cm; SH)Rain (R)High-Density Graupel (HG)Low-Density Graupel (LG)Drizzle (Drz)Wet snow (WS)Dry Snow (DS)Vertical Ice (VI)
1. Examine polarimetric parameters and temperature at each grid point
2. Score each hydrometeor category based on observations relative to known range of values for each hydrometeor class (determined from field obs, scatter modeling)
3. Highest score wins
Algorithm produces “dominant” hydrometeor type---thiscan be summed to provide storm volumes of hydro type-crude information can be derived on mixing ratios.
SMN Radar: Lang (CSU), SMN Radar: Lang (CSU), Carbone Carbone (NCAR) and SMN(NCAR) and SMN
• SMN C-band Doppler radars
• 24/7 operation• Reflectivity and Doppler
velocity products• Coordination with
NERN raingages• Reflectivity available in
real-time where internet service is available
Contacts: tlang@atmos.colostate.educarbone@ucar.edu
SMN Upgrade IssuesGuasaveUpgrade completed 6/10PRF increased 7/29 – Best Doppler data afterwardSoftware problems prevented full-volume 360sData recording outage 7/22-29
Los CabosUpgrade completed 7/15PRF increased 7/20 – Best Doppler data afterwardMechanical problems prevented full-volume 360sNo solar gain calibrations
ObregonTransmitter power supply failed
PalmitoLightning strike and fuel/shippingdelays
●Highest priority radars upgraded (Guasave & Cabo)
●Can use low-level sweeps to map rainfall and characterize horizontal structure of storms
NERN : NERN : ShuttleworthShuttleworth, Watts, Gochis, , Watts, Gochis, GaratuzaGaratuza
• 100 Event logging, tipping bucket raingages
• 6 major W-E transects traversing SMO
• Major improvement in topographic and temporal sampling of precipitation
• Installed 2002-2003, in operation through spring of 2006
• Not available in real-time
Contacts: gochis@rap.ucar.edu, watts@fisica.uson.mx, garatuza@itson.mx
Integrated Sounding Systems: JohnsonIntegrated Sounding Systems: Johnson
• 3 NCAR/ISSs deployed at Puerto Peñasco, Kino Bay, Los Mochis– GPS soundings, 915 MHz
wind profiler, RASS, sfc. met.
• 1 NCAR GLASS system deployed at Loreto, BCS– GPS sounding, sfc. met.
• Up to 6 soundings per day during IOPs
• Available in real-time, GTS available
Contacts: johnson@atmos.colostate.edu
Puerto Peñasco - ISS
Kino Bay - ISS
Los Mochis - ISSLoreto - GLASS
Precipitation and Vertical Wind Profiling: Precipitation and Vertical Wind Profiling: Williams and WhiteWilliams and White
• Coastal Site (near Mazatlan, SIN)– S-band vertically
pointing profiler– 449 MHz vertical wind
profiler– Surface disdrometer
• Vertical air motion and particle motion obs.
• Site 40 km from SPOL
• Not available in real-timeContacts: cwilliams@al.noaa.gov
allen.b.white@noaa.gov
Coastal Site: Southern SINCoastal Site: Southern SIN
S-Pol Blockage
Mean PowerClear-Air0.8 degElevation
Little to No Blockageabove 2 deg Elevation
MinorBlock
Major Blocks
Much of Low-Elevation Sweeps over Land Blocked at S-PolBut We Can Recover Using Phase!
MountainClutter
Ocean
Radar Data Quality Control
S-Pol RadarMostly automatedThreshold away non-meteorological echo (clutter, insects, etc.)Filter differential phase (PHIDP) and calculate KDPBlockage & attenuation correction
Currently working to improve the KDP algorithm
SMN RadarsApply calibration – Intercomparison with S-Pol & TRMMCan threshold away most non-meteorological echoSome hand-editing needed for insects and leftover clutterRainfall & attenuation correction based on Z-R (Hudlowalgorithm from GATE) – Tune using S-Pol
Red - 1.8°Yellow - 1.3°Green - 0.8°
DBZ corrected for blockage by invoking self-consistency betweenDBZ and KDP in rain
Corrected up to 5 dB reduction in DBZ; ZDR set to missing in blocksBlocks > 5 dB – use higher angle sweep in iterative manner
(0.8 -> 1.3 -> 1.8 deg)1.8 deg not blocked anywhere more than 5 dB – last resort
Blockage Correction
S-Pol Version 1 Quality Control MethodologyThreshold on RHOHV, STDDEV(PHIDP) – noise, clutterThreshold on DBZ, ZDR – insectsThreshold on LDR, PHIDP – second trip21-pt (3.15 km) finite impulse response (FIR) filter on PHIDPAdaptive linear fit to calculate KDP (i.e., higher DBZ, fewer pts used)DBZ, ZDR corrected for rain attenuation via PHIDP methodDBZ corrected for gaseous attenuation (Battan 1973)Rainfall calculated using CSU algorithm; base Z-R: Z=221R^1.25
(Z-R from gauge intercomparison; Used pol-tune as guide)FHC done using CSU method (Tessendorf et al. 2005)
S-Pol Version 2 ImprovementsImproved blockage correction due to reduced KDP noiseCan correct up to 35 dB before moving to higher scanImproved filters to eliminate spurious dataAvailable this winter
SMN QCThreshold on NCP, DBZ, and PowerHand edit insects, clutterClutter map used to help eliminate clutter at GuasaveVisual and statistical gate-to-gate intercomparison
w/ S-Pol to determine calibration offset for DBZCorrect DBZ for gaseous attenuation (Battan 1973)Correct DBZ for rain attenuation using GATE iterative methodUsed same Z-R as S-PolCapped rain rates at ~230 mm/hr due to ice contamination
Regional Composites
Example – 0200 UTC on 8/6/04
Cabo
Guasave
S-Pol
“Near-surface” reflectivity and rainfall every 15 minutes – 0.01, 0.02, & 0.05-deg grids
Use low-level sweep – For S-Pol, use higher sweeps to fill in gaps caused by clutter and complete blocks
S-Pol uses polarimetric rainfall estimates; SMNs will use Z-R based on polarimetrictuning – Constrain with gauges
Will create smaller grid containing vertical information from S-Pol (0.5-km vert res);Grid will include hydrometeor ID
Priority is EOP coverage by S-Pol (7/9-8/21)
Example ofproducts provided by radar composites:Accumulated Rainfall
Shown here:1-day rainfall for 17 July 2004
Regimes: Analysis Domain• Radar composites were
rotated 35° to be terrain-parallel, and features were identified within the dashed box (every 15 minutes where available)
• Radiosondes werelaunched at Los Mochis ISS site (4-6 x per day) and Mazatlan airport (2-6 x per day)
S-Pol
Guasave
CaboMazatlanMazatlan
Los Los MochisMochis
W E S N
Regime Aindex Regime B
index
Example of Reduced Dimension Example of Reduced Dimension AnalysisAnalysis44--9 August 20049 August 2004
RegimesA; E to W
B; S to N
A/B-mix
No identi-fiableregimes
Ahijevych and Carbone, NCAR
• E-W composites show propagation of systems from peaks -> foothills -> coastal plain -> GoC
• N-S composites shows slight northward propagation of systems in the diurnal cycle
1-D Reduced Dimension Diurnal Analysis
NAME Precipitation Feature/Regime Analysis
• Contiguous areas (including corner pixels) of radar reflectivity ≥ 15 dBZ were identified as precipitation features within the NAME regional composites (following Nesbitt et al. 2000)
• For the entire field project, 145712 features were identified within the composites for the ~10 week period July-August 2004
• Attributes including rainfall volume, conditional rain rates, convective area/rain fraction (Steiner et al.1995), and feature maximum dimension were recorded for each feature
NAME Composite Reflectivity LoopNAME Composite Reflectivity Loopfrom 00 Z 5 Aug from 00 Z 5 Aug -- 00 Z00 Z 7 Aug7 Aug
Diurnal cycle of PF characteristics as a function of location
• Demonstrates gradual propagation of precipitating systems E -> W
• Large rainfall phase difference between peaks and coastal plain
SMOheating;Migration,Sea-breeze,Mergers,Land breeze
Location of Location of ““OrganizedOrganized””Precipitation Features within the Precipitation Features within the
Diurnal CycleDiurnal Cycle
X
•No Regime: “Noon Balloon”type convection quickly organizes, but rarely progresses downslope into the night time hours
•During the disturbed regimes, convection propagates downslope, but is longer lasting to the south until itdissipates near sunrise over the GoC; AB regime most active
Regime Thermodynamic Sounding Composites at Los Mochis, Mazatlan
•CAPE lowest during during AB regime, but moistest above 700 hPa
•Generally more CAPE at Los Mochis due to higheroverall low level θe (RH similar)
• “No Regime” has highestCAPE, but relatively drier, especially at Los Mochis -may serve to limit westward propagation in diurnal cycle through entrainment and evaporation
•Strongest U wind low-level shear in AB, esp. at Mazatlan
•Weakest shear inNo Regime cases
•Little differentiation in V wind profiles, stronger by 1-2 m/s in B and AB cases
•Overall low level shear stronger at Mazatlan, may explain longer lived systems in S part ofdomain
Unrotated Unrotated wind profiles at Los wind profiles at Los MochisMochis, , MazatlanMazatlan
Preliminary Conclusions from Radar Preliminary Conclusions from Radar PF/Sounding AnalysisPF/Sounding Analysis
• Different regimes reflected in characteristic PF diurnal cycles– Noon initiation seen in all regimes, but differing environments seen in
disturbed/undisturbed regimes – More moist, more shear in disturbed regimes; more favorable for long-lived
convective systems– N/S Variability in lifetime of organized convection tied to N/S variability in
moisture and cross-barrier low-level wind shear. Why?• Need to deconvolve pertinent local- large-scale mechanisms which influence
the observed convective forcing and convective system morphologies throughout their life cycle
– Gulf surges– Easterly Waves– Position of Monsoon High– Influence of Westerlies– Land Surface/Atmosphere Interactions– Sea Breeze Convergence
Radar/Lightning AnalysesZonal Propagation: Standard Anomalies
(Flash Count – Mean)/σ
Courtesy: Walt Petersen
CG FlashHovmollersfrom theLong-RangeNLDN
Expansion of monsoon with time
Easterly waves clearly evident
ZH
RHOHV
ZDR
PHIDP Power LDR
KDPLargeHailAloft(D > 2 cm)
Attenuation
Melting hailcausing largephase shifts
Melt Level
05 Aug '042123 UTC
Large HailHigh ZNeg ZdrLow RHOHigh LDR
Very IntenseConvection!
Courtesy T. Lang
Future Work – Microphysical Case Studies
7/20-21 MCS(Vertically Intense)
During IOP #3(Monsoon ridge breakdown)
7/29 Sea breeze (Shallower)
During IOP #4(Monoon break & sea breeze)
23 July 2004
Future Work – Satellite Intercomparison
What are the convective characteristics causing of the reversal of the PR-TMI bias between the SMO and Coastal Plain?