GV for Snowfall GV for Snowfall Retrieval ResearchRetrieval Research

David HudakDavid Hudak

Paul JoePaul Joe Environment EnvironnementCanada Canada

2nd International GPM Ground Validation Workshop, 27-29 September, Taipei, Taiwan

Ref: WMO Publication No. 9 Volume ARef: WMO Publication No. 9 Volume A

All active Synoptic Stations north of 50 N

90° N

75° N

60° N

45° N

247729 Oct 200129 Oct 2001

POSS OccurrencePOSS Occurrence(1 minute data)(1 minute data)

•Surface obs•Doppler XBand•Derived Snowrates•Minutely•Snow only•Typed by observer•1 winter of data

YEV=Inuvik 68°NYUL=Montreal 45°N

Vertical Profile AnalysisVertical Profile AnalysisFort Simpson (62Fort Simpson (62°°N)N) Montreal (45°N)(45°N)

Quantifying Snow Gauge Errors

Systematic errors:

WIND (temperature) wetting loss evaporation loss non-zero trace

capping of gauge orifice

blowing snow

Goodison et al

0

20

40

60

80

100

120

0 1 2 3 4 5 6 7 8 9

Wind speed at gauge height (m/s)

Rat

io o

f gau

ge c

atch

to th

e D

FIR

(%)

Canadian Nipher NWS 8" AlterNWS 8" unsh Hellmann unshTretyakov

WMO Intercomparison Study Results

Catch Efficiency vs Wind for the 4 most widely used gauges

Precipitation Occurrence Sensing System (POSS)

•Doppler •Mie Scattering•Terminal Velocity

•XBand •Bistatic•Continuous Wave

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2POSS Estimate/DFIR

0

0.1

0.2

0.3

0.4

0.5

Re

lati

ve

fre

qu

en

cy

Egbert,O nt. Sept 1997-Feb 200459 observations (tw ice daily)so lid precip ita tion onlyT<0C ; D FIR >=1 m m

R PR PV

POSS Research Applications Quantitative Precipitation Estimation (QPE)

• Solid precipitation rate validation using the Double Fence Intercomparison Reference (DFIR)

Under over

POSS Research ApplicationsQPE Snow Density

0.0 0.10.02 0.04 0.06 0.08 0.20

Average density (gcm -3)

1

2

0.90.8

0.7

0.6

0.5

0.4

0.3

0.2

PO

SS

(RP

)/D

FIR

E gbert, O nt. Sept1997 to Feb 200454 observations (tw ice daily)R P m ethod assum ing snow density=0.1 gcm -3

Tem p. <0 C ; W ind<20kts; D FIR >0.1m m

0.01 0.10.02 0.04 0.060.08 0.2

A verage density (gcm -3)

0.6

0.8

1

1.2

1.4

Ave

rag

e m

ode

velo

city

(m

s-1

)

Egbert, O nt. Sept1997 to Feb 200446 observations (tw ice daily)Tem p. <0 C ; W ind<10kts; D FIR >0.1m m

1 minute snow water equivalent precipitation rate

Hot plate insensitive

18:00 19:00 20:00 21:00 22:00 23:00 0:00Time

0

1

2

3

4

Sn

ow

f al l

wa

ter

eq

uiv

ale

ntp

r ec i

pi ta

ti on

r ate

( mm

h-1)

AIRS2 Mirabel SnowEnding: 031218 00:00Observer total amount= 4.8 mm

Hot Plate1(5.23 mm)Hot Plate2 (4.69 mm)POSS (5.18 mm)

POSS Research ApplicationsAirport Vicinity Icing and Snow Advisor (AVISA)

NCAR/DRI Hot Plate

Centre fo Atmospheric Research ExperimentsCentre fo Atmospheric Research ExperimentsEC field project deployment suite

Penn StateSpectrometer

Wind Profiler

HotPlates

X-bandRadar

Univ. of AlaskaW-bandRadar

McGill Univ.

Video Disdrometer

10m met towerRadiation sensorsVisibility meterCeilometer

MW Radiometer

POSS

W-band:

•Nadir and Vertical-up: Z, LDR, Vd

•Vertical-up – side: Polarimetric, Vd

•Nadir-Side: Polarimetric, Doppler

•Nadir – Nadir-aft – Dual-Doppler

•Side – Side-forward – Dual-Doppler

X-band:

•Nadir and vertical-up – Single polarization

•Side - Polarimetric

NRC Airborne W/X – band radar (NAWX)

Fully Polarimetric and Doppler W-band: Five ports – Electronic switching X-band: Two ports - Electronic switching

CONVAIR-580 CLOUD MICROPHYSICS (cntd)

C a n a d a

Standard PMS 2D Imagery

800 um

6400 um

Under-wing particle probes

POSS Research ApplicationsPrecipitation Typing

Doppler Spectral Mode Analysis

RAIN SNOW

Mixed SNOW & RAIN

YHMYKF

King City C-band Dual Polarized radar

ZR-IP-S

Correlation Coefficient ρhv

C-band Polarization parameters

Correlation Coefficient ρhv

Differential Reflectivity ZDR

Reflectivity Z

Specific Differential Phase kdp