Transcript TECO-2012 (Brussels,Belgium,17 Oct. 2012) 3（5） Field experiment on the effects of a nearby asphalt road on temperature measurement Summer N S wind Meteorological Instruments Center, Japan Meteorological Agency (JMA) Mariko.

TECO-2012 (Brussels,Belgium,17 Oct. 2012)
3（5）
Field experiment on the effects
of a nearby asphalt road
on temperature measurement
Summer
N
S
wind
Meteorological Instruments Center, Japan Meteorological Agency (JMA)
Mariko Kumamoto1, Michiko Otsuka2, Takeshi Sakai1 and Toshinori Aoyagi2
1
Meteorological Instruments Center, JMA, Tsukuba, Japan
2 Meteorological Research Institute (MRI), Tsukuba, Japan
http://www.jma.go.jp/jma/indexe.html
http://www.jma.go.jp/jma/jma-eng/jma-center/ric/RIC_HP.html
1
0．Background
Needs for observing temperature data
of high quality from data users
Many JMA stations are located in
urbanized areas and surrounded by
artificial heat source (buildings, car
roads, car parks, artificial surfaces … )..
Metadata describing site
environment would be helpful.
e.g. the WMO siting
classification (CIMO Guide)
However, interpretation of such metadata is unclear
without any theory or guidelines based on related
experiment or research.
2
1. Purpose of Study
• Focus on the effects from asphalt surface on temperature
measurement
• Clarify the characteristics of temperature distribution near an
asphalt car road
– With relation to the distance from the road, wind condition
and mounting height of sensors
• Better interpretation of siting
metadata to estimate temperature
measurement uncertainty
WIND
Tref
Glass
Heated Air
T1 Ｔ2 Ｔ3 Ｔ4
Asphalt road
Glass
3
2．Data and method
2-1. Field layout and sensor installations
Summer : 30th June - 1st Oct. 2010, Winter :29th Nov. 2010 - 6th Jan. 2011
Sample
points
T4
T3
T2
T1
Distances from the road (m)
10.0m
6.9m
3.2m
0.8m
10.0m
Reference
point
T0
(Image:Google Maps)
height
2.5m
10.0m
2m
Prevailing wind direction
Summer: S (SSW-ESE)
Screen with artificial ventilation
( Thermometer )
Ultrasonic anemometer
□ : Experiment Site (square 100m)
as area below indicates
● : Thermometers with radiation
shield
：Asphalt Road
Difference(℃)
δT = TN – T0
(compared at
the same height)
1.5m
0.5m
T0
TN
(N=1,2,3,4)
The height of temperature
measurement is 1.5m on
JMA operational observation.
Surface temperature (Asphalt road, glass)
In winter, the prevailing wind direction was NW (WNW-NE), so the sensors were installed on the opposite side.
4
2-2. WMO siting classification and sampling points
●Temperature by the WMO siting classification (2010) （surface of heat sources［％］）
class5
class3
class4
・not meeting the
requirement of
Class4
class1
30m circle
100m circle
up to 1℃
up to 2℃
Uncertainty up to 5℃
class2
・less than 50 %
circular area of 10m
・ less than 30 %
circular area of 3m
10m circle
Class 3, 4, and 5 are determined by the environment within 10m in radius.
● The distances from the road and S ［％］ at each sampling point
（the ratio of the area occupied by the road within 10m in radius)
T1
T2
T3
T4
10m
0.8m
class5
circle 10m in radius
45％
3.2m
class4
6.9m
class3
10.0m
The distance from the road for each
sampling point was determined to
represent the conditions of Class 3, 4
and 5 in the WMO siting classification.
class3
S ［％］
30％
10％
0％
5
3. Results
3 - 1. Wind direction frequency and δT distribution
at different distances / heights
distances
Summer （30th June - 1st Oct. 2010）
1.5m
Frequency
×103
T3
3.2 m
T4
6.9m
48
48
44
44
44
40
40
40
36
36
36
36
32
32
32
32
28
28
28
28
24
24
24
24
20
20
20
20
16
16
16
16
12
12
12
12
8
8
8
8
4
4
4
4
0
0
0
44
40
-0.5
0
0.5
1
-1
-0.5
0
0.5
-0.5
0
0.5
1
-1
32
32
32
28
28
28
28
24
24
24
24
20
20
20
20
16
16
16
16
12
12
12
12
8
8
8
4
8
4
4
0
4
0
0
-0.5
0
0.5
1
-1
-0.5
0
0.5
1
16
12
8
4
0
16
12
8
4
0
-1
-0.5
0
0.5
class5
1
(℃)
-0.5
0
0.5
class4
1
(℃)
-0.5
0
0.5
1
0
-1
-0.5
0
0.5
1
-1
-0.5
0
0.5
1
-1
-0.5
0
0.5
1
16
12
8
4
0
16
12
8
4
0
-1
10.0m
0
-1
1
32
-1
0.5m
T2
0.8 m
48
-1
Frequency
×103
heights
2.5m
Frequency
×103
T1
48
-1
-0.5
0
0.5
class3
1
(℃)
class3
δT(℃)
 At 0.5m height in case of southerly wind, the highest frequency of biases were up to +0.2 to
+0.4 ℃
 At 1.5m height , only small biases were seen near the road. No significant biases at T2, T3 and T4.
6
3－2. By wind speed δT frequency distributions
(Surface temperature difference ≧ 10 °C)
Summer (30th June - 1st Oct. 2010)
0.5m
［m/s］
1.5m
［m/s］
heights
2.5m
0.8 m
T2
distances
3.2 m
T3
6.9m
T4
10.0m
Frequency ratio
×0.01［％］
Wind speed
［m/s］
T1
Southerly
+0.2℃
+0.5℃
+0.1℃
+0.3℃
class5 (℃)
class4 (℃)
class3 (℃) class3 δT(℃)
 In all cases, the stronger the wind, the fewer large biases
 At 0.5m height, the highest frequency of δTs and the range of δTs variation were larger
when the wind was less than 2m/s.
 At 1.5m height, even when the wind speed was relatively weak, the highest frequency of
δTs appeared around 0.0℃ to +0.2 ℃ regardless of the distance from the road.
7
4．Summary
The extent of effects of the asphalt road (10m in width)
 At the height of 1.5 m, the high frequency of δTs for the
total period was around +0.1 – +0.2℃ and 0.0 ℃ , for summer
and for winter respectively.
 At the height of 0.5 m, the effect depends significantly on
the distance from the road. Not much difference at the height
of 1.5 m.
When the wind speed is over 2 m/s in summer or over 1
m/s in winter, the effect is reduced.
We presented only summer cases. If you would like to know winter cases or much
more in details, please read papers.
8
5. Conclusion
From the results of the field experiment,
 The effects of the road depend much on prevailing wind directions.
were reduced when the wind was relatively strong.
 In the implementation of the WMO siting classification,
we also need to take wind conditions into account.
よとｈ
How effect
by the
windward
side?
Surrounding objects such as buildings or
trees may reduce the wind speed and affect
temperature measurement.
0
40m
(Image:Google Maps)
As a next step, we study the effects of nearby trees on the wind
speed and temperature measurement by field experiment.
9
●
Another Experiment (currently in progress )
－Influences by the trees around the observation field－
(height:20.5m)
Pyranometer
(height:2m)
Trees
(West
side)
Radiometer
(height:1.5m)
1H=9m (average height of trees on west side)
Pt 3mmΦ(Screen(E-834-Z1))
MR-60
Pt 3mmΦ(Screen(JV-280))
CMP-21
Surface temperature (thermocouple)
WXT520 (1H, 2H）, WS425 （4.5H）
FF13
WS-JN6
Fig. Layout of instrumentation
To support reliable high-quality climate monitoring, it is necessary to consider how
environmental changes around the site influence observation data.
The examination is performed to allow quantitative evaluation for the effects of trees located
10
at one side of the field on temperature and wind measurement data.