Eduardo Barbaro * with contributions of:

25
Aerosols in the convective boundary layer: effects on the radiation field and the land-atmosphere system Eduardo Barbaro * with contributions of: Jordi Vila, Maarten Krol, Huug Ouwersloot, Henk Baltink, Fred Bosveld, Dave Donovan, Wouter Knap, Ping Wang eorology and air-quality group eningen University [email protected] CESAR DAY KNMI

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Aerosols in the convective boundary layer : effects on the radiation field and the land-atmosphere system. Eduardo Barbaro * with contributions of: Jordi Vila, Maarten Krol, Huug Ouwersloot, Henk Baltink, Fred Bosveld, Dave Donovan, Wouter Knap, Ping Wang . CESAR DAY. KNMI. - PowerPoint PPT Presentation

Transcript of Eduardo Barbaro * with contributions of:

Page 1: Eduardo Barbaro * with contributions of:

Aerosols in the convective boundary layer: effects on the radiation field and the land-atmosphere system

Eduardo Barbaro*

with contributions of:Jordi Vila, Maarten Krol, Huug Ouwersloot, Henk Baltink, Fred Bosveld, Dave Donovan, Wouter Knap, Ping Wang

*Meteorology and air-quality group Wageningen University [email protected]

CESAR DAYKNMI

Page 2: Eduardo Barbaro * with contributions of:

This talk is about:

CBL dynamicsRadiation

Land surface

Scattering

Aerosols

Absorption

Soil propertie

s

Latent heat

Sensible heat

Heat

budget

CBL height

θ, q

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Strategy to answer:

Research question

Combining observations and

numerical modeling

How do the CBL dynamics and the land-atmosphere system react to the SW radiation absorbed by the aerosols during the day ?

CBL dynamics

Radiation

Land surface

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Comprehensive observation dataset

CBL heightθq

CBL dynamics

RadiationAerosols

Land surface

Radiation budget:(LW ↕and SW ↕)

Aerosol properties:AOD, ω, g

SEB:QNET, SH,LE,G0

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Numerical modeling

CBLdynamic

s

Surface

fluxes

Aerosols and

radiation

• LES: 3-D high-resolution model able to reproduce detailed CBL dynamics.

• MXL: Simplified bulk model able to reproduce the most important CBL dynamics.

• Penman-Monteith: Land-surface model able to calculate the SEB.

• Delta-Eddington: Broadband radiative transfer code able to calculate SW radiation profiles accounting for the aerosol information.

LESMXL

Radiative transfer (Delta- Eddington)

SEB (Penman- Monteith)

The MXL model is used to perform 256 systematic runs (sensitivity analysis) varying the initial aerosol properties (AOD and ω).

Broader quantification!

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CBL prototypes

t

h 25th September 2003

Aerosol layer

t

h 8th May 2008

Aerosol layer

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Aerosol temporal evolution and vertical structure

Similar to Wang et al 2009

We constrain the aerosol data in our LES and MXL models (red dashes).

8th May 2008

t

h

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Initial conditions: θ and q8th May 2008

Residual layer Aerosol layer

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Radiation budget8th May 2008

R2 = 0.99RMSE = 8.4 Wm-2

R2 = 0.93RMSE = 9.7 Wm-2

LES

CESAR

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SEB and CBL height8th May 2008

LES

CESAR

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Thermodynamic variables8th May 2008

LES

CESAR

Entrainment of drier air

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Sensitivity Analysis: AOD

CLEAR CONTROL AERO+

Cabauw BeijingBarcelona

OsloQuebec

τCONTROL = 0.2 τAERO = 0.6τCLEAR = 0.0

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SW and SEB modificationsτ = 0.6

τ = 0.2

τ = 0.0

25th September 2003

- Aerosols directly reduce downward irradiance- Relatively constant reduction on LE (10-20%) - SH is influenced more strongly- Aerosols increase EF (up to 20%)

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Vertical heat budget and θτ = 0.6

τ = 0.2

τ = 0.0

25th September 2003

Aerosols:- Morning (dotted lines):

reduce the surface fluxeswarm the residual layer

- Afternoon (solid lines):Heat the CBL

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CBL height evolution

- Aerosols shallow the CBL because of less entrainment- Aerosols delay/anticipate the CBL onset/collapse

τ = 0.6

τ = 0.2

τ = 0.0

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MXL: sensitivity analysis (τ x ω)

C A

25th September 2003

C AC AC A

AOD and SSA

IrradianceEvaporative

fraction

CBL height

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Take home message:

Disrupt the land-atmosphere diurnal cycle• Reduce irradiance, SH and LE• Shallow and warm the CBL

Aerosols will (in a nutshell):

When also located above the CBL (I): • Strongly shallow the CBL • Delay the CBL onset

When located within the CBL (II): • Shallow the CBL (also reduce Δθ) • Anticipate the CBL afternoon collapse

t

h

(I) (II)

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Aerosols on the land-atmosphere system

SH

Δθ

QNET

θ

ω τ+- +

-

τ-

ω+

τ-

ω+

LE

τ-ω

+

HR

zi

-+

τ-

ω+

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(τ x ω)25th September 2003

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Two-stream approximation

N=1

Two stream approach is an approximation of the RTE in which radiation is propagating in only two discrete directions.

Diffuse radiance production by simple scattering of direct solar radiation

Diffuse radiance production by scattering of diffuse radiation available in dτ.

The multiple scattering contribution is represented by up(down)ward

intensities weighted by the appropriated asymmetry factor

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Two-stream approximationTwo stream approach is an approximation of the RTE in which radiation is propagating in only two discrete directions.

Diff (2) and filling (1) in we have:

Boundary conditions:TOP -> I↓ = 0SURF -> I↑ = albedo*I ↓

Page 22: Eduardo Barbaro * with contributions of:

Two-stream + Eddington’s approximationEddinton’s approximation is an improvement on two-stream approach.It can be used to obtain the radiance in a plane-parallel medium with ISOTROPIC SCATTERING.The scattering is also assumed frequency-independent (representative λ) ->not true for aerosols!.Example: Stellar atmospheres (Eddington, 1916).

OPS!

Boundary conditions:TOP -> I↓ = 0SURF -> I↑ = albedo*I ↓

I

μ

Page 23: Eduardo Barbaro * with contributions of:

The DELTA-Eddington principleThe Eddinton-two stream approach produces very good results for thick layers but is inaccurate for thin layers andwhen significant absorption is involved.

f, fraction of scattered energy residing in the forward peak

We remove f=g2 (f≈0.5) from τ, ω, and g in order to better define the phase function.

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A complex system: (Interconnection between radiation – land surface – CBL dynamics - Aerosols)

Almost no mass here!

BL h

eigh

t

(<2km)

TOA (100km)

870 Wm-2

Mie scattering + absorption -> attenuates shortwave radiation!Big particles (both absorption + scattering)

H LE

(39 km)

25%SW Reflection

θCBL↑

Tsurf ↓ 800 Wm-2

CABAUWTOA

Rayleigh scattering

Diffuse Direct