applied micrometeorology in the arctic - candac•micrometeorology (n.): the study of meteorology on...
TRANSCRIPT
![Page 1: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/1.jpg)
Applied Micrometeorology in the Arctic
Summer School in Arctic Atmospheric Science
Nottawasaga Inn
12 July 2011
Ralf Staebler, Environment Canada
![Page 2: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/2.jpg)
Outline
• Significance of surface –
atmosphere interactions
• Crash course in
micrometeorology:
– turbulent transport
– stability / atm. stratification
– flux-gradient relationships
• A flavour of recent Arctic
research projects
![Page 3: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/3.jpg)
Surface-Atmosphere Interactions
in the Arctic
• Weather & climate forecasting: lower boundary condition of input of heat & water vapour into the atmosphere
• The Arctic Ocean as a CO2 sink
• The Arctic Ocean as a source of aerosol particles and/or their precursors (e.g. DMS)
• Deposition of aerosol particles (esp. soot) onto the Arctic snowpack (albedo effects)
• Atmosphere-surface exchange of ozone, mercury vapour and chemical species involved in their destruction / transformation
![Page 4: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/4.jpg)
What is usually available:
• Surface parameters (remote sensing, in situ monitoring)
• Column parameters
(remote sensing, balloon profiles)
• Vertical gradients
What we’re usually really after:
Surface fluxes (emission
&
deposition rates)
Need to develop reliable
flux-gradient relationships
to get from here to there!
![Page 5: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/5.jpg)
Crash Course in Micromet
• Micrometeorology (n.): the study of
meteorology on a spatial scale of < 1km
and time scale of < 1 day
• Focus on boundary layer dynamics,
turbulent transport, local circulations,
microclimates, atmosphere-surface
exchange
![Page 6: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/6.jpg)
From: Oke, Boundary Layer Climates
![Page 7: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/7.jpg)
The Boundary Layer:that part of the troposphere that is directly influenced by the presence
of the earth’s surface and responds to surface forcings with a time
scale of ~ an hour [100’s to low 1000’s of meters]
The Surface Layer:the layer in direct contact with the surface in which turbulent fluxes are
not significantly different from the surface fluxes
(“constant flux layer”)
Often arbitrarily taken as the bottom 10% of the BL.
More Definitions...
![Page 8: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/8.jpg)
From R.B.Stull: An Introduction to Boundary Layer Meteorology
![Page 9: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/9.jpg)
uD
itycosvis
inertiaRe
From: Oke, Boundary Layer Climates
Laminar vs. Turbulent Flow
![Page 10: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/10.jpg)
From: D.A. Haugen (Ed.), Workshop on Micrometeorology
“Big whorls have little whorls,
which feed on their velocity;
and little whorls have lesser whorls,
and so on to viscosity.“L.F. Richardson, 1922
(paraphrasing Jonathan Swift)
![Page 11: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/11.jpg)
Energy source for ALL atmospheric motions:
Horizontal
temperature
gradients
Mechanical turbulence
Wind
Vertical
temperature
gradients
Thermal turbulence
Buoyancy
The SUN
Surface Heating
![Page 12: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/12.jpg)
So you may say: don’t forget about molecular diffusion as
a transport mechanism!
Well…
Molecular diffusivity: ~10-5 m2s-1
Eddy (turbulent) diffusivity at 20 m with moderate
winds: ~ 10 m2s-1 (i.e. a million times higher)
Molecular diffusivity only plays a role really close to the
surface, where eddy diffusivity drops (~ linearly with z),
i.e. for z < 1 mm
![Page 13: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/13.jpg)
The Richardson Number: a measure of stability
2
z
u
z
g
Ri
potential energy
kinetic energy
negative lapse rate Ri < 0 statically unstable
KE > PE Ri < 0.25 dynamically unstable
positive lapse rate &
wind shear not too big: Ri > 0.25 stable
Stull 1988
![Page 14: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/14.jpg)
Profile Statistics, Amundsen 2008Temperature
(Microwave Profiler)
Wind Speed
(Sodar) Richardson Number
![Page 15: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/15.jpg)
Dome C (French/Italian Antarctic Research Station): 3233m ASL
C. GENTHON, D. SIX, V. FAVIER, L. GENONI,
C. POUZENC, A. PELLEGRINI
CNRS / LGGE (France): “Extremely Stable
Boundary Layer on the Antarctic Plateau”. IPY
Science Conference, Oslo, June 2010.
![Page 16: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/16.jpg)
Analogy of turbulent fluxes with diffusion: the eddy diffusivity approach
Classical Diffusion – Fick’s First Law
x
cDJ
Where
J is the diffusion flux [mol m-2 s-1]
D is the diffusion coefficient or diffusivity [m2 s-1]
c is the concentration [mol m-3]
x is the position [m]
z
cKF
So we assume that turbulence transports
quantity c in a similar manner, and say
Where
F is the turbulent flux [mol m-2 s-1]
K is the turbulent transport coefficient
or eddy diffusivity [m2 s-1]
low c
high c
![Page 17: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/17.jpg)
To deal with this, we turn to Monin-Obukhov Similarity Theory:
A bunch of universal empirical relationships to describe
vertical profiles and fluxes in the boundary layer
For example: The wind profile in the surface layer under neutral conditions
(no heat flux) is well described by
kz
u
dz
u *
)''(2
* wuu where u* is the friction velocity and k is the von Karman constant
(0.4). Note that u* is a measure of the momentum flux.
dz
u
u
kzm
*
Let’s define a nondimensional gradient
It stands to reason that the relationship between vertical gradients and
fluxes is a function of stability; i.e.
z
cstabilityKF )(
![Page 18: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/18.jpg)
Similarity Theory continued
There are similar relationships between heat flux and the temperature profile, etc.
[Businger-Dyer relationships]
, z/L > 0 (stable)
, z/L =0 (neutral)
, z/L < 0 (unstable)
L
z7.41
4/1
151
L
z
m = 1
''
3
*
v
v
wkg
uL
Turns out that m under non-neutral conditions can be expressed as a universal
empirical function of the normalized height z/L,
where L, the Obukhov length, is given by
![Page 19: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/19.jpg)
Flux-Gradient Relationships
z
uKF mmm
)(
To get back to the eddy diffusivity concept:
1
*
1)( mmneutralmm kzuKK
It is easy to show that
unstable stable
neutral
and similar for eddy diffusivities for heat and
gases
![Page 20: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/20.jpg)
Low O3
High O3
Updraft:
w’ > 0
O3’ < 0
Downdraft:
w’ < 0
O3’ > 0
Average Wind O3 & w’
Sensors
www '
333 ' OOO
'' 3OwFlux
Still not convinced this is a flux? Check the units: (m/s)(ng/m3) = ng/m2/s
The Eddy Covariance Technique
Example: O3 fluxes
![Page 21: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/21.jpg)
(Ultra)Sonic Anemometers
d / t1 = c - w
d / t2 = c + w
w = d/2(1/t2 – 1/t1)
c = d/2(1/t2 + 1/t1)
Tc
t1t2
![Page 22: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/22.jpg)
Sources
and Sinks (s)
szcw
xcu
zw
xuc
zcw
xcu
tccu
tc
Dt
Dc
'''')()(
dz
z
cwAdvectionVertical :
cdzt
Storage :
The O3
budget: conservation of c (2-D simplification)
'': cwExchangeTurbulent
dzx
cu
AdvectionHorizontal
:
![Page 23: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/23.jpg)
Current Research
• Under what conditions can Arctic surface
fluxes be determined through standard flux
techniques?
• How far can we extend Monin-Obukhov
similarity theory into very stable regimes?
• Can we develop a theory that quantifies
intermittent transport in very stable
regimes?
![Page 24: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/24.jpg)
SHEBA data set
• Micromet tower near the Des
Groseilliers Canadian Coast
Guard Icebreaker, parked in the
Beaufort/Chukchi Seas
• 5 sonics between 2.2 and 18.2m
• 11 months of data
![Page 25: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/25.jpg)
Grachev et al., Boundary-Layer Meteorology (2005) 116:201235
(z1 = 2m)
![Page 26: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/26.jpg)
z
uKFlux neutral
![Page 27: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/27.jpg)
OASIS 2009
Barrow, Alaska
Micromet Tower:
5 sonic anemometers
4-component net radiometer
Temperature & humidity
Surface temperature (IR)
Atmospheric Pressure
nearby (420m south):
SODAR (wind speed & direction up to
800m)
NOAA / ARM (2km east):
ozone sondes
rawinsondes
Microwave profiler
![Page 28: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/28.jpg)
![Page 29: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/29.jpg)
![Page 30: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/30.jpg)
Median sonic SL Profiles, Barrow’09
![Page 31: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/31.jpg)
“There is no critical Richardson number above which the turbulence
vanishes”. Larry Mahrt (2010), “Variability and Maintenance of Turbulence
in the Very Stable Boundary Layer”, BLM 135, 1-18.
![Page 32: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/32.jpg)
Sorbjan & Grachev (2010)
SHEBA Galperin et al. (2007)
Prandtl Number:
Pr = Km/Kh
![Page 33: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/33.jpg)
Summary:
1. It’s not THAT stable in the Barrow
surface layer (in April), i.e. standard
flux methods work well much (85%)
of the time
2. We still don’t know how to deal with
very stable conditions… need multi-
year flux-gradient measurements to
collect enough ultra-stable data
Future Work:
1. Flux-gradient relationships for gas
exchange (Kc(z/L))
2. Flux-gradient “monitoring” at various
locations
3. Theoretical framework to deal with
intermittent mixing in very stable
conditions
![Page 34: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/34.jpg)
Questions?
![Page 35: Applied Micrometeorology in the Arctic - CANDAC•Micrometeorology (n.): the study of meteorology on a spatial scale of < 1km and time scale of < 1 day •Focus on boundary layer dynamics,](https://reader035.vdocuments.us/reader035/viewer/2022070217/611f5782db1dc85c7a0d8e4e/html5/thumbnails/35.jpg)
Collapsible mast:
* Wind-speed/direction
* Global radiation (up/down)
* Sonic anemometer
* Tilt sensor
* Temperature 3 levels
* Relative humidity
* High level gas sampling
Top of instrument box:
* MAXDOAS scanhead with
tilt/compass sensor
* GPS antenna
* WiFi antenna
* webcam
Inside instrument box:
Two shock proof instrument racks :
* 2B ozone monitors (two)
* Gardis GEM monitors (two)
* MAXDOAS spectrometer for BrO
* Licor CO2 monitor
* GPS
* CR3000 data logger
* PC104 computer
* WiFi radio
Other features
* 100% autonomous operation for
duration of battery charge (~2 days)
* Self heating
* 24 VDC power with DC/DC
converters providing stable 12.6 VDC
* Sled on Teflon runners
* Low level gas sampling (10 cm)
* Setup time: 15 min
The famous OOTI sled