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?