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Gauge Precipitation and Snow Depth Measurements
Daqing Yang University of Alaska Fairbanks
Barry GoodisonEnvironment Canada
• Gauge network: global coverage with various operational, national/regional networks.
• Gauge network data: long-term and fundamental, defining global snowfall/climate regimes and changes.– Manual and automatic gauges, measuring water equivalent (amount), not
snow particle size. – Manual gauges can measure snowfall (rate) at 6-hour to daily time intervals,
and auto gauges can provide hourly (or sub-hourly) snowfall (rate).
• Snow rulers / snow depth sensor: snowfall observations at the national/regional networks, providing snow depth info, not SWE.
• Snow pillow/snowboard: snow accumulation changes over time -(in)direct measurement of snowfall.
Status of Observations
Arctic Precipitation Issues
• Operational networks – our knowledge base – Decline of the networks in the northern regions, including
Siberia, Alaska and N. Canada– Few stations in the mountain regions – How to sustain and improve the operational networks
• Data quality and compatibility across national boundaries– Large biases in gauge measurements of solid precipitation– Incompatibility of precipitation data due to difference in
instruments and methods of data processing – Difficulties to determine precipitation changes in the arctic
regions
• Validation of precip data, including satellite and reanalysis products and fused products at high latitudes.
Various networks
Synoptic/climate stations on land above 45°N and the Arctic Ocean drifting stations
Russia
Mongolia
Kazakhstan
Greenland
China
Canada
• Sparseness of the networks.
• Uneven distribution of measurement sites, i.e. biased toward coastal and the low-elevation areas, less stations over mountains and oceans.
AMBLER (1994 - 95) HAPPY VALLEY CAMP (1970 - 77) POINT HOPE (1924 - 82)
AMBLER WEST (1981 - 92) KILLIK (1981) PRUDHOE BAY (1986 - 99)
BARTER ISLAND AP (1947 - 1988) KIVALINA (1973 - 75) SAG RIVER DOT (2000 - present)
CANDLE (1903 - 50) KOBUK (1953 - 79) SELAWIK (1953 - 55)
CAPE THOMPSON (1960 - 63) KUPARUK (1983 - present) SHISHMAREF (1919 - 1973)
COLVILLE VILLAGE (1996 - present) LONELY (1977 - 81) SHUNGNAK CAA (1949 - 1950)
DEADHORSE AIRPORT (1999 - present) NOATAK (1917 - 24) UMIAT ARPT (1945 - 2001)
GALBRAITH (1970 - 80) NOORVIK (1997) WAINWRIGHT (1935 - 1968
NWS Climate Station Network
XX
Xhttp://climate.gi.alaska.edu/Stations/Arctic/index.html
NRCS SNOTEL / Wyoming gauge network
www.wcc.nrcs.usda.gov/snotel/Alaska/alaska.html
NRCS National Water and Climate Center
UAF/WERC Kuparukbasin rain
gauge stations
http://www.uaf.edu/water
Upper headwater, July 14-18, 1999
0
1
2
3
4
5
6
7
8
9
10
195 196 197 198 199 200
Julian day
Hou
rly ra
infa
ll (m
m)
0
10
20
30
40
50
60
70
80
90
100
Cum
ulat
ive
rain
fall
(mm
)l
Heavy rainfall events in summer of 1999
NOAA US CRN
http://www.ncdc.noaa.gov/oa/climate/uscrn/
Various gauges and snow fences
National standard gauges tested in Barrow
Canadian Nipher
Hellmann
Russian Tretyakov
US 8”
Blowing snow impact: blocking snow fence
Barrow, CRN- DFIR, Mar 3/03
Barrow, UAF-DFIR, Mar 3/03
Barrow, CRN- DFIR, Mar 3/03Barrow, CRN- modified DFIR, at 2.5m, Mar 3/03
Barrow, UAF Wyoming snow fence, Mar/03 Barrow, UAF DFIR, Mar 03
Blowing snow blocking
gauge / wind shield
Barrow, UAF-DFIR, Mar 3/03
NOAA ETI recording gauge at 1m, Barrow, Mar 3/03
Tretyakov gauge in the DFIR Barrow, Mar 3/03
Blowing snow impact: gauge overcatch?
a) Dikson (73.30N, 80.24E)
05
101520253035
0 2 4 6 8 10 12 14 16 18 20
Daily mean w ind speed at 2m (m/s)
Daily
sno
wfa
ll pre
cipi
tatio
n (m
m)
a) DIKSON, 73.30N, 80.24E
0
20
40
60
80
100
120
1 2 3 4 5 6 7 8 9 10 11 12
Mon
thly
pre
cipi
tatio
n (m
m)
trace amount
wind loss
measured
• Wind-induced gauge under-catch• Wetting and evaporation losses• Underestimate of trace precipitation events • Blowing snow into gauges at high winds• Uncertainties in auto gauge systems
Biases in Gauge Measurements
WMO double fence intercomparison reference (DFIR)
in Barrow, AK
WMO Solid Precipitation Intercomparison
CRN modified DFIR
Goodison, B.E., P.Y.T. Louie, and D. Yang, 1998: WMO solid precipitation measurementintercomparison, final report, WMO/TD-No. 872, WMO, Geneva, 212pp.
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
0
5
10
15
20
25
30
35
1 2 3 4 5 6 7 8 9 10 11 12Months
Prec
ipita
tion
(mm
)
trace
wind-loss
measuredOverall mean for the NP drifting stations, 1957-90 (Yang, 1999)
Overall mean for 61 climate stations in Siberia, 1986-92 (Yang and Ohata, 2001)0
10
20
30
40
50
60
70
80
1 2 3 4 5 6 7 8 9 10 11 12
Month
Prec
ipita
tion
(mm
)
trace amount
wind correction
measured
0
5
10
15
20
25
30
Jan
Feb
Mar
Apr
May Jun
Jul
Aug
Sep
Oct
Nov
Dec
measureable trace
05
1015202530354045
Jan
Feb
Mar
Apr
May Jun
Jul
Aug
Sep
Oct
Nov
Dec
tracewetting losswind lossmeasured
Prec
ip (
mm
)Pr
ecip
day
s
Bias corrections of daily precipitation data, Barrow, 1982-83
(Yang et al., 1998)
a) Pm (mm) b) Pc (mm) c) CF
Mean Gauge-Measured (Pm) and Bias-Corrected (Pc) Precipitation, and Correction Factor (CF) for January
-180
-150-1
20
-90
-60
-30
0
30
60
90
120
150
180
45 60 75 90
Pc (mm)
0 - 1010 - 2020 - 3030 - 4040 - 5050 - 6060 - 7070 - 8080 - 9090 - 390
-180
-150
-120
-90
-60
-30
0
30
60
90
120
150
18045 60 75 90
CF
1 - 1.11.1 - 1.21.2 - 1.31.3 - 1.41.4 - 1.51.5 - 1.61.6 - 1.71.7 - 1.81.8 - 1.91.9 - 2.3
-150
-120
-90
-60
-30
0
3060
90
120
150
45 6 0 75 90
Pm (mm)
0 - 1010 - 2020 - 3030 - 4040 - 5050 - 6060 - 7070 - 8080 - 9090 - 330
• Total 4827 stations located north of 45N, with data records longer-than 15 years during 1973-2004.
• Similar Pm and Pc patterns – corrections did not significantly change the spatial distribution.
• CF pattern is different from the Pm and Pc patterns, very high CF along the coasts of the Arctic Ocean.
Yang et al., 2005, GRL
y = 1.2103x - 0.1012R2 = 0.9448
-15
-12
-9
-6
-3
0
3
6
9
12
15
-15 -12 -9 -6 -3 0 3 6 9 12 15
Pm trend (mm)
Pc tr
end
(mm
y = 1.0575xR2 = 0.9962
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7
Pm trend (mm)
Pc tr
end
(mm
Jul.
Jan.
Impact of Bias-Corrections on Precip TrendPm & Pc Trend Comparison, Selected Stations with Data > 25 Yrs during 1973-04
Yang et al., 2005, GRL
Impact of Bias-Corrections on
Northern Hydrology:
CLM3 simulations with/without P
corrections, 1973-045~25%
Auto gauges and snow depth sensor
Challenges for auto QA/QC
0
2
4
6
8
10
12
14
16
18
20
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300 010
020
030
040
050
060
070
080
090
010
0011
0012
0013
0014
0015
0016
0017
0018
0019
0020
0021
0022
0023
00
Time (15 min intervals)
Acc
umul
ated
Pre
cipi
tatio
n (m
m) a
nd 2
m w
ind
spee
d (m
/s)
-20
-15
-10
-5
0
5
Air
Tem
pera
ture
(deg
.C)Ws2 (m/s)
Unsh. Belfort (mm total)
Alter Belfort (mm total)
Nipher Belfort (mm total)
DFIR Belfort (mm total)
Ta (deg.C)
WMO Study: Timing and catch differences of Belfort Gauges at Kortright, Ontario Feb. 19-20/1988
Automation of precipitation measurementsAutomation of precipitation measurements
Need for adjustmentsNeed for adjustments
0
20
40
60
80
100
120
adjusted Nipher Belfort Belfort Belfort Belfort
DFIR Nipher unshielded unshielded Alter shielded Nipher shielded DFIR shielded
Types of Precipitation Gauges & Shields
Prec
ipita
tion
Am
ount
(% o
f adj
uste
d D
FIR)
all types(R, S, X) snow only
Mean annual accumulated winter precipitation > 3.0 mm, of different gauge types and shielding as a percentage of DFIR (adjusted for catch deficiency) at the Canadian Evaluation Station at Kortright Centre, Ontario from 1987-1991.
WMO result: Geonor vs. DFIR Jokioinen, Finland, 12h data, 12/1988-4/1993
-5
0
5
10
15
20
25
30
-5 0 5 10 15 20 25 30
Geonor + DFIR (mm)
Geo
nor (
mm
)
rainmixedsnow
Catch-wind relation, 12h snowfall, DFIR > 3mm, Jokioinen
y = -7.5744x + 93.485R2 = 0.4693
0
20
40
60
80
100
120
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
Wind speed at 3 m (m/s)
Ratio
of G
eono
r to
Geo
nor-DFI
R (%
)
Oct Feb Jun Oct Feb Jun
Dep
th (c
m)
0
10
20
30
40 Test Auto A (SR50)Test Auto BTest Auto CTest Auto DTest Auto ETest Auto FStation AutoStation Manual (ruler)
Snow Depth Spatial Variability and Fixed-Point Measurements
Edmonton International Airportopen landscape
see a high degree of spatial variability even over a short distance (3 to 300m)
of six temporary and a fixed station SR50, and manual ruler measurements, none are statistically similar to each other
Challenges:to provide the best quality measurements to
the research communityfor the research community to recognize these
issues when using the data (e.g. comparisons with spaceborne data)
Arctic Precipitation Issues
• Operational networks – our knowledge base – Decline of the networks in the northern regions, including
Siberia, Alaska and N. Canada– Few stations in the mountain regions – How to sustain and improve the operational networks
• Data quality and compatibility across national boundaries– Large biases in gauge measurements of solid precipitation– Incompatibility of precipitation data due to difference in
instruments and methods of data processing – Difficulties to determine precipitation changes in the arctic
regions
• Validation of precip data, including satellite and reanalysis products and fused products at high latitudes.
Measuring freshly fallen snowfall with Snow Measuring freshly fallen snowfall with Snow BoardsBoards
Original
Weaverboard 2000
for use as an Observer’s aid
10cm snowfall is 10mm precipitation
Russian Meteorological
stations
MSC Networks – precip/Snow Cover