Physik Fachbereich 1 Institut für Umweltphysik Satellite Based Retrieval of Desert Dust Deposition...

PhysikFachbereich 1

Institut für Umweltphysik

Satellite Based Retrieval of Desert DustDeposition into the Atlantic Ocean

SeaWIFS AOT June 2008

Jäger, Malte1; Lelli, Luca1; von Hoyningen-Huene, Wolfgang1; Vountas, Marco1; Burrows, John Philip1

*Institute of Environmental Physics (IUP), Bremen

Project information:

• working group: CASPAR @ IUP (Cloud Aerosol Surface PArameter Retrieval group)• cooperation with MARUM: Jan-Berend Stuut, Ute Merkel, Gerhard Fischer, Carmen Friese

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Institut für UmweltphysikSatellite Based Retrieval of Desert Dust

Deposition into the Atlantic Ocean

Content

• Motivation• The whole project• Study area & aims• Retrieval method• Preliminary results• Summary & outlook

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Motivation

[Winckler, et. al.]

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Study Area & Aims

SeaWIFS AOT June 2008

Dust deposition: estimation of mass loss along transport trajectory

Comparison with sedimentation records


Atlantic Ocean west of Sahara, e.g. Cape Blanc

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Main Goal:

Establish the relationship between dust sedimentation at sea bottom and atmospheric dust load

S edim entation record fromsea bottom

R econstruction of AO T of past tim es

M odelling aerosol radiative forc ing and SST change of the past

D erive present atm osphericdust deposition in N -A tlanticfrom satellite observations of AO T

M odellingsedim entation process of dustto the ocean bottom

M odelling of present aerosol radiative forc ingand e ffect on S STfrom AO T andsedim ent data

Calibra tion of dust deposition m assin term s of AO T

Sedim entationm easurem ents(Sedim ent traps)

The whole project


Interdisciplinary ProjectInstitute of EnvironmentalPhysics,Uni Bremen

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Retrieval Method


• Step 1: Aerosol / dust data

• AOT data (BAER SeaWiFS, BAER OE MERIS, MISR, …)

• Identification of aerosol type (dust): AAIUV

• Estimation of the columnar aerosol load from AOT

3 ( ) log ( )4 logAer ext Col Aer Aer

dM rQ d r xxxxxxxxdz M f ar d r

xx

Aerosol optical thickness columnar aerosol mass

size distribution & density of dust needed.. … …. .

.. … …. ... … …. .

.. … …

.. ..… …. .

.. … …. ... … …. .

.. … …. ... … …

.. ..… …. .

h

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Retrieval Method


• Step 2A: Deposition estimation

• Dust deposition: estimation of mass loss along transport trajectory

• Definition of several boxes along trajectory of dust transport

• Difference in AOT between boxes -> deposition

M2 M1

1 2 ( )I IIAer Aer

SedaM Mc

A t A t

Using long term averages of dust mass change over a reference area

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Retrieval Method


• Step 2B: Transport trajectories

• Wind data: ECMWF reanalysis {+ satellite data}

• Transport level / altitude:1. wind data ~ 1.5km2. retrieval run3. new wind level adapted to situation: assumption: high deposition <-> lot of dust at low level -> the higher the deposition from 1st run, the lower the relevant wind level4. 2nd retrieval run with adapted wind data

• Box orientation and form adapted to trajectory

• Future improvements: aerosol profiles, e.g. CALIPSO CALIOP

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First test and visualization


Limitations:

• Transport:• Real wind not considered• Assumption: easterly-winds

• Coarse spatial resolution: ~1° AOT, deposition fields 2° x 2°

• Low temporal resolution: monthly mean AOT

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Preliminary Results 1Example: MISR L3 AOT: Time series and images


Two boxes (M1, M2):

AOT:• strong maximum in

summer• clear and repeating

minimum around winter (+ small maximum)

Deposition:• AOTM2 < AOTM1 => deposition• strong signal during

summer

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Preliminary Results 2: SeaWiFSData: 1997 - 2010

Boxes:Latitude for all: 20-22°N

1. 13,5 - 15,5 ° W2. 15,5 - 17,5 ° W3. 17,5 - 19,5 ° W

4. 19,5 - 21,5 ° W5. 21,5 - 23,5 ° W


1996 2000 2004 2008 2012Tim e

-0.40

0.00

0.40

0.80

1.20

1.60

AO

T(0.

412

µm)

SeaW iFS , C ape B lanc, m onth ly AO T(412 nm )G rid B oxes 20-22 N

13.5-15.5 W

15.5-17.5 W

17.5-19.5 W

19.5-21.5 W

21.5-23.5 W

[Hoyningen-Huene]

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Preliminary Results 2: SeaWiFS


[Hoyningen-Huene]

( )I IIIAer Aer

Sed AerM aA t

1996.00 2000.00 2004.00 2008.00 2012.00T im e / years /

0.00

0.02

0.04

0.06

0.08

Del

ta A

OTR

2R3*

AO

TR2

0

200

400

600

Dus

t Sed

imen

tatio

n /

mg/

(m²*

day)

/

-0.02 0.00 0.02 0.04 0.06grad(AO TR 2R 3)*AO T(R 2)

0.00

100.00

200.00

300.00

400.00

Dus

t Sed

imen

tatio

n /

mg/

(m² d

ay)

/

[data: Hoyningen-Huene, Yoon, Fischer]

Deposition derived from AOT and real sedimentationSediment trap,Picture: Stuut

Correlation:Data:

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Summary & outlook



Article summarizing the project:Luca Lelli, W. von Hoyningen-Huene, M. Vountas, M. Jäger and J.P. Burrows ; Dust deposition rates derived from optical satellite observations; Past Global Changes Magazine; Volume 22, 2014http://www.pages.unibe.ch/download/docs/magazine/2014-2/PAGESmagazine_2014(2)_64-65_Lelli.pdf

13 / 14

• First retrieval to measure dust deposition from satellites• Main idea: evaluation of AOT changes along transport path of dust• Promising results from first tests, even though these included many simplifying assumptions -> correlation with in-situ observations

• Implementation of real trajectories upcoming• Calibration for mass deposition rates (using particle size distribution and in-situ measured deposition rates)• Identification of mineral dust via AAIUV

• Detailled comparison with in-situ data from sediment traps and surface dust collectors

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Thank you for your attention

Questions?

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Thank you for your attention

Questions?


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Instrument: SeaWiFS

[NASA]

SeaStar satellite with SeaWiFS on board

Instrument BandsBand Wavelength

1 402-422 nm2 433-453 nm3 480-500 nm4 500-520 nm5 545-565 nm6 660-680 nm7 745-785 nm8 845-885 nm

instrument characteristics:Mission Characteristics

Orbit Type Sun Synchronousat 705 km

Equator Crossing Noon +20 min, descending

Orbital Period 99 minutes

Swath Width 2,801 km LAC/HRPT (58.3 degrees)

Swath Width 1,502 km GAC (45 degrees)

Spatial Resolution 1.1 km LAC, 4.5 km GACRevisit Time 1 day

time of operation: 1997 - 2010


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Motivation

• Aerosols play an important role in climate development:• warming effect• cooling effect (mineral dust)

[IPCC 2013]

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Motivation

[ESA: ENVISAT MERIS]

• Mineral dust has an influence on the oceans

-> Fertilisation

Climate …


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Aerosol Absorbing Index (UV)


[Pepijn Veefkind, et. al., KNMI]

Physik Fachbereich 1 Institut für Umweltphysik Satellite Based Retrieval of Desert Dust Deposition...

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