results of the wmo intercomparison of thermometer screens/shields and hygrometers in hot desert...
TRANSCRIPT
RESULTS OF THE WMO
INTERCOMPARISON OF
THERMOMETER
SCREENS/SHIELDS AND
HYGROMETERS IN HOT DESERT
CONDITIONS
Muriel LacombeWMO CIMO-TECO 2010, 31 August 2010
2
Contents
1. Introduction• Background• Objectives
2. Methods• Site• Instruments• Calibration• QA/QC
3. Results4. Conclusions
3
Introduction
Background Several intercomparisons of screens and hygrometers, all in
temperate conditions None in hot or cold desert conditions Importance for climatology
Objectives Performance of screens/shields for high radiations Performance of hygrometers in high temperatures and very low
humidity conditions Evaluate the impact of ancillary factors on the sensors Draft recommandations to CIMO
4
Methods - 1
Site Ghardaïa, in central Algeria
Instruments 29 screens/shields
o artificially-ventilated: 7 different modelso naturally-ventilated: 9 different models
17 humidity sensors (8 different models) 2 extra Thies ultrasonic wind sensors
Most of sensors were installed in pairs.
Intercomparison period From the 1st of Nov., 2008 to the 1st of Nov., 2009
5
Methods - 2
Calibration Temperature measurements: calibrated Pt100 Before the intercomparion, in the RIC of Trappes On-site calibration No calibration after the intercomparison for the moment
QA/QC Daily check by local staff Pictures taken once per month Specific software to flag data according CBS recommendations
6
Results
One full year of measurements A large dataset although some gaps in the data More than 500 000 minutes available for most of sensors
o More than 95% available valid data
The analysis was made jointly by :o Météo-France : Muriel Lacombe and Michel Leroy o ONM: Djazia Bousri and Mohamed Mezred
Final report : published soon A dedicated study for each model of instrument is available
7
Temperature during the intercomparison period
8
Relative humidity during the intercomparison period
9
Choice of the references
Screens Artificially-ventilated screen The coldest during daytime
Choice: Eigenbrodt screen
Hygrometers Thygan as first reference Communication problems with Thygan, during the last 6 monthes Another reference, the closest to Thygan
Choices: Thygan and Vaisala HMP45D
10
Results for screens - 1
General results Nearly all small naturally-ventilated screens are warmer Artificially-ventilated screens are not significantly colder Large Stevenson screens are very close to the reference
-1,5
-1
-0,5
0
0,5
1
1,5
ATH
I1
ATH
I2
LBO
M
LCA
S
LLA
N1
LLA
N2
LSO
C
SDA
V1
SDA
V2
SSO
C1
SSO
C2
SVA
I1
SVA
I2
SWIN
1
SWIN
2
SYO
U1
SYO
U2
VD
AV
1
VD
AV
2
VE
IG11
VE
IG12
VE
IG21
VFI
S1
VFI
S2
VRO
T1
VTH
Y1
VTH
Y2
VY
OU
1
VY
OU
2
Screen/ Shield
Tem
pera
ture
diff
eren
ces w
ith
VE
IG22
(°C
)
3292
06
3083
33
5031
24
5031
24
5031
24
5031
24
5031
24
5031
23
5031
24
5031
24
5031
24
3454
61
2397
93
5031
24
5031
24
5031
24
5031
24
5031
24
5031
24
5031
16
5031
24
4768
18
5031
24
5031
24
4995
31
9655
1120
4
4457
0
4457
0
Number of cases
Median 5% - 95% interval 25% - 75% interval 0.5% - 99.5% interval Extrema
11
Results for screens - 2
During clear days and low wind speeds Some small naturally-ventilated screens are colder Artificially-ventilated screens are generally warmer Large Stevenson screens are very close to the reference
-5
-4
-3
-2
-1
0
1
2
3
4
5
ATH
I1
ATH
I2
LBO
M
LCA
S
LLA
N1
LLA
N2
LSO
C
SDA
V1
SDA
V2
SSO
C1
SSO
C2
SVA
I1
SVA
I2
SWIN
1
SWIN
2
SYO
U1
SYO
U2
VD
AV
1
VD
AV
2
VE
IG11
VE
IG12
VE
IG21
VFI
S1
VFI
S2
VRO
T1
VTH
Y1
VTH
Y2
VY
OU
1
VY
OU
2
Screen/ Shield
Tem
pera
ture
diff
eren
ces w
ith
VE
IG22
(°C
)
1421
4
1265
7
1800
6
1800
6
1800
6
1800
6
1800
6
1800
6
1800
6
1800
6
1800
6
1415
9
8907
1800
6
1800
6
1800
6
1800
6
1800
6
1800
6
1800
6
1800
6
1706
0
1800
6
1800
6
1800
5
247
325
4720
4720
Number of cases
Median 5% - 95% interval 25% - 75% interval 0.5% - 99.5% interval Extrema
12
Results for screens - 3
Combined effect of wind and radiation
13
Results for hygrometers - 1
General results 5 models gave very good results: 98% differences are within
3% 2 models stayed within 4% of the reference 1 model showed larger deviations
-20-18-16-14-12-10-8-6-4-202468
101214161820
LBO
M
SVA
I1
SVA
I2
UH
MP1
1
UH
MP1
2
UH
MP2
1
UH
MP2
2
UTE
S2
VFI
S1
VFI
S2
VRO
T1
VTH
Y1
VTH
Y2
Sensor
Rel
ativ
e hu
mid
ity
differ
ence
s w
ith
UH
MP2
(%)
464160 329350 241294 464064 464077 464168 464168 463970 464160 464159 464114 9600 11043
Number of cases
Median 5% - 95% interval 25% - 75% interval 0.5% - 99.5% interval Extrema
14
Results for hygrometers – 2
Periods with relative humidity lower than 20%
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
LBO
M
SVA
I1
SVA
I2
UH
MP1
1
UH
MP1
2
UH
MP2
1
UH
MP2
2
UTE
S2
VFI
S1
VFI
S2
VRO
T1
VTH
Y1
VTH
Y2
Sensor
Rel
ativ
e hu
mid
ity
differ
ence
s w
ith
UH
MP2
(%)
86307 68206 64156 86305 86305 86308 86308 86307 86305 86305 86304 0 0
Number of cases
Median 5% - 95% interval 25% - 75% interval 0.5% - 99.5% interval Extrema
15
Conclusions – What is next?
Final report : published soon It is the first WMO intercomparison of
screens/shields and hygrometers in hot desert conditions
Despite some gaps, a large dataset was collected during this intercomparison
A deep analysis was conducted:o To select referenceso To study each sensor’s behaviour
Experience and specific tools were developpedo Database systems, QC softwares, macros/codes for
plots…
A similar comparison is planned in Canadao for cold desert conditions
Thank you !