CO2 and Heat Flux Observations in Suburban Baltimore (Cub Hill)
Five-day Ensemble Fluxes
Sue Grimmond1, Brian Offerle1, John Hom 2 and Dan Golub2
1Dept
Energy and radiation balance fluxes
of Geography, Indiana University, Bloomington, IN (grimmon@indiana.edu); 2Northeastern Research Station, USDA Forest Service, Newton Square, PA
The Importance of Urban Areas
Urban Energy Balance
The Site and Seasonal Changes
Data Availability
Flux Data Availability
Modification of the energy balance in urban areas
comes from:
• Changes in the surface materials and morphology
• Additional sources of energy from human activities
Earth at Night
Q* + QF = QE + QH + ?QS
Q*
QF
QE
QH
∆QS
Not Observed
Missing or invalid 10 Hz data
Incomplete day (rain, etc.)
10 Hz data for sonic only
Complete day, QA
May
[W m-2]
net all-wave radiation
anthropogenic heat flux (heat released by human activities)
latent heat flux
sensible heat flux
storage heat flux (heating the urban fabric)
Fisheye image from top of tower
Credit: C. Mayhew & R. Simmon (NASA/GSFC), NOAA/ NGDC, DMSP Digital Archive
Study Site: Cub Hill, Maryland
• Urban areas are extensive. ~ 50% world’s population (3 billion
people) live in urban areas. By 2025 the UN predicts this will double
• Cities are major sources of CO2 and other atmospheric pollutants
– the effects of cities extend well beyond their boundaries
• Within urban areas the controls on surface atmosphere exchanges
are both the sources of the emissions and the physical meteorology
Ancillary Data Availability
26 June (175)
• Site is near Towson, MD in Greater Baltimore
• Suburban area which is extensively forested
(mature deciduous forest - see photos)
• Large increase in number of buildings in recent
years. Further increases in density are likely.
• The buildings in the area around the tower are
predominately 1 storied single-family dwellings
(see photos)
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23
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26
27
28
29
30
31
Jun
Jul
Aug
Sep
Not Observed
Missing data
Only ground data
Complete
Oct
May
Jun
Jul
Aug
Sep
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9
10
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31
Oct
CO2 fluxes
Daily Energy, Radiation and CO2 Fluxes
12 July (193)
Variability of Fluxes with Wind Direction
Objective
To determine the momentum, heat, water, CO2 fluxes at the local
or neighborhood scale for an urban area
Qh/Q*
Bowen
.8
7 Sep (250)
.6
.4
Spatial Scales
.2
To conduct eddy covariance measurements in an urban environment
that are representative of the local scale, it is necessary to ensure:
• instruments are located high enough above the roughness
elements (buildings, trees); typically > 2zH
• there is sufficient fetch (i.e. the neighborhood is extensive)
.0
10 Oct (283)
•
•
•
•
101 m
Micro-scale
102-103 m
Local-scale
104-106 m
Meso-scale
23 Oct (296)
Instrumentation
Wind Distribution by 10o Sector (30 min periods)
Mounted ~ 40 m above ground level
Vertical
10° bins
Data period: 2001/137-275 (biased towards Sept/Oct data)
QH/Q* - scale: red numbers
ß = QH/QE - scale: 0-4 (yellow circle)
0
340
350 .04
10
20
330
30
23 Oct (296)
Relative Frequency
320
40
.03
310
50
300
60
.02
290
70
.01
280
80
270
.00
90
260
100
250
110
240
120
230
130
220
140
210
200
Instrumentation
[Oke 1997]
Acknowledgements: Site access is provided by the Maryland Department of
Natural Resources, Communications, State Police and Forest Service. This
research is supported by the USDA Forest Service (Grimmond), National Science
Foundation (Grimmond), USFS Northern Global Change (Hom), and NSF Baltimore
Ecosystem Study LTER.
Incoming and outgoing short (K) and
long (L) wave radiation fluxes -> Q*
Temperature/Relative Humidity
Precipitation
Wind speed and direction
Pressure
Different levels on the tower
Temperature
Air intakes for CO2 concentration
Ground Level
Soil Heat Flux
Soil Temperature
Soil Moisture
160
0
350 4.5
330
10
4
3.5
3
2.5
2
1.5
1
0.5
0
320
310
300
Speed (m/s)
C02, H20, T profile
170
180
340
R.M. Young Sonic Anemometer
Model 81000
Licor Li-7500 CO2/H20 analyzer
Kipp and Zonnen CNR1 Net
radiometer
CSI 500
Weathertronics 6011B raingauge
R.M. Young wind sentry
Vaisala PTB101B
190
290
280
270
Mean
Max
20
30
40
50
60
70
80
3
6
90
12
9
260
100
250
110
240
Omega thermcouple wire
Licor Li-6262 Closed-Path IRGA
120
230
130
220
140
210
150
200
CSI HFT 1 Soil heat flux plates
CSI TCAV
CSI TDR CS-615
190
170
180
160
Maximum mean over 30 minutes
Top of Tower
Heat, moisture, momentum & CO2
fluxes
150