Optical Properties and Radiative Forcing of Desert Dust at Lampedusa Island: What We Have Learned Since 1999

Daniela Meloni Laboratory for Earth Observations and Analyses, ENEA, Rome

7th International Workshop on Sand/Duststorms and Associated Dustfall 2-4 December 2013, ESA/ESRIN, Frascati (Rome), Italy

Thanks to:

Fabrizio Anello, Carlo Bommarito, Paolo Chamard, Lorenzo De Silvestri,

Tatiana Di Iorio, Alcide di Sarra, Jose Luis Gómez-Amo, Francesco

Monteleone, Giandomenico Pace, Salvatore Piacentino, Damiano M.

Sferlazzo, Claudia Di Biagio, Marco Cacciani, Wolfgang Junkermann, Victor

Estellés, Giampitro Casasanta, Virginia Ciardini, Maria Mansueto, Cecilia

Tirelli, Chiara Volta, Jose Antonio Martinez-Lozano

WHY LAMPEDUSA?

• Lampedusa island is largely affected by dust intrusions from the Sahara desert, particularly in late spring and early summer, with large aerosol optical depths and particles extending in the vertical up to 6-8 km;

• The island hosts the ENEA Station for Climate Observations, with the aim of long-term monitoring of greenhouse gases, aerosol, radiation;

• The ENEA Station represents an ‘open sea’ measurement site, optimal for the validation of satellite observations;

• In the last 15 years the ENEA Station has been improving in the number and quality of measurements…

www.lampedusa.enea.it

IN 1999… Brewer

spectrophotometer Visible MultiFilter Rotating Shadowband Radiometer

(MFRSR)

Lidar system for tropospheric aerosols (ENEA/Univ. of Rome)

Meteorological tower

… IN 2013

AERONET CIMEL

ENEA/Univ. of Rome LIDAR

HATPRO

BREWER Visible and UV MFRSR PYRANOMETER,

PYRGEOMETER, PAR

METEO TOWER

RADIOSOUNDING

ACTINOMETER

SP02 AND SP02-L

SHADED PYRANOMETER AND PYRGEOMETER, PYRHELIOMETER, HYPEROCR

TSI

HYPEROCR

APPROACH

Dust optical properties and

radiative forcing

GROUND-BASED MEASUREMENTS

AIRBORNE MEASUREMENTS SATELLITE OBSERVATIONS

RADIATIVE TRANSFER MODEL SIMULATIONS

UV-VIS IR

DERIVATION OF THE AEROSOL SINGLE SCATTERING ALBEDO,

ASYMMETRY FACTOR AND OF THE DIRECT AEROSOL RADIATIVE

FORCING IN THE UV-VISIBLE

a) Using ground-based and airborne measurements during the Photochemical Activity and Ultraviolet Radiation modulating factors II (PAUR II) campaign in May-June 1999 b) Using ground-based measurements and Multi-angle Imaging SpectroRadiometer (MISR) spaceborne observations in July 2002

THE PAUR II CAMPAIGN IN MAY-JUNE 1999

Ground-based measurements: AOD, total ozone, lidar extinction profile, meteorological paramters, UV and VISIBLE spectra.

Vertical profiles (up to 4 km) of ozone, aerosol extinction, aerosol particle size, radiation and meteorological parameters from the instrumented IMK-IFU ultralight ENDURO-KIT (P.I. dr Wolfgang Junkermann).

Radiative transfer model libRadtran [Mayer et al., 1997], 200-800 nm, with main modifications.

DERIVATION OF THE AEROSOL SINGLE SCATTERING ALBEDO, ASYMMETRY FACTOR AND OF THE DIRECT AEROSOL RADIATIVE FORCING IN THE UV-VISIBLE

METHODOLOGY AND RESULTS Comparison of measured and modelled surface Brewer UV spectra (286.5-363 nm) for cloud free-conditions to estimate the aerosol COMPLEX REFRACTIVE INDEX.

THE MULTI-ANGLE IMAGING SPECTRORADIOMETER (MISR)

SPACEBORNE OBSERVATIONS IN JULY 2002

DERIVATION OF THE AEROSOL SINGLE SCATTERING ALBEDO, ASYMMETRY FACTOR AND OF THE DIRECT AEROSOL RADIATIVE FORCING IN THE UV-VISIBLE

AOD (500 nm) = 0.227

14 July

α = 0.080

16 July α = 0.698

METHODOLOGY AND RESULTS

Best match wavelength-independent SSA and g in the visible

Simulation of the visible MFRSR global irradiances with different SSA and g minimum

RMSD

Simulation of the visible MISR equivalent

reflectances with different SSA and g

14 July SSA = 0.96-0.97

g = 0.79-0.80

16 July SSA = 0.88-0.89

g = 0.81-0.82

Meloni et al., JGR, 2004

DERIVATION OF THE AEROSOL SINGLE SCATTERING ALBEDO, ASYMMETRY FACTOR AND OF THE DIRECT AEROSOL RADIATIVE FORCING IN THE UV-VISIBLE

DIRECT AEROSOL RADIATIVE FORCING CALCULATIONS 400-700 nm

Day ω0 g Surface ADRFE (W/m2)

TOA ADRFE (W/m2)

18/05/1999 0.79 0.77 -54.4 -2.4

14/07/2002 0.97 0.80 -29.4 -15.9

16/07/2002 0.88 0.81 -44.5 -9.5

DERIVATION OF THE AEROSOL SINGLE SCATTERING ALBEDO IN THE

VISIBLE-NEAR INFRARED FROM MFRSR MEASUREMENTS AND

RADIATIVE TRANSFER SIMULATIONS

SSA(λ)

Computation of look-up tables of diffuse-to-direct radiation ratio (DDR) at 415.6 and 868.7 nm (60°±2.5°SZA) by means of libRadtran.

415.6 nm

Measured DDR(λ) and AOD(λ)

METHODOLOGY

Period: July 2001-September 2003

RESULTS

SSA(415.6 nm)= 0.81±0.05

SSA(868.7 nm)= 0.94±0.05

Meloni et al., ACP, 2006

Period: May 1999-December 2005

0.70 0.75 0.80 0.85 0.90 0.95 1.00

SSA

0.00

0.04

0.08

0.12

0.16

RE

LA

TIV

E F

RE

QU

EN

CY

0.4 0.6 0.8

0.5

0.6

0.7

0.8

0.9

1

SS

A

-0.2 0 0.2 0.4 0.6

0.5

0.6

0.7

0.8

0.9

1

SS

A

SSA(415.6 nm)= 0.77±0.04

SSA(868.7 nm)= 0.94±0.04

Meloni et al., Atm. Env., 2007

Uncertainty ± 0.06

SSA(441 nm)= 0.91±0.03

SSA(869 nm)= 0.98±0.01

0.4

Cimel #172, Lampedusa, 2003-2013 Lev. 2

Reference Wavelength (nm)

SSA

Meloni et al. 2003 (PAUR II)

500 0.78-0.79

Meloni et al. 2004 (MISR)

400-700 0.96-0.97 0.88-0.89

Meloni et al. 2006 415.6 868.7

0.81±0.05 0.94±0.05

Meloni et al. 2007 415.6 868.7

0.77±0.04 0.94±0.04

AERONET Lampedusa (2003-2013)

441 869

0.91±0.03 0.98±0.01

Estellés et al. 2007 500 0.91±0.04

Tafuro et al. 2006 440 0.84-0.92

Collaud Coen et al. 2004 470 880

0.87-0.91 0.92-0.94

Masmoudi et al. 2003 870 0.86-0.99

Kubilay et al. 2003 440 870

0.93-0.98 0.97-0.99 Uncertainty ± 0.03

DERIVATION OF THE DIRECT AEROSOL RADIATIVE FORCING IN

THE SHORTWAVE FROM GROUND-BASED AND SATELLITE

MEASUREMENTS IN 2004-2007

Co-located surface and Clouds and the Earth’s Radiant Energy System (CERES) observations on Terra and Aqua platforms

Di Biagio et al., JGR, 2009

Direct method [Satheesh and Ramanathan, 2000]:

METHODOLOGY AND RESULTS

Desert dust (DD)

AOD (495.7 nm)

Di Biagio et al., JGR, 2009, 2010

RESULTS

DERIVATION OF THE AEROSOL OPTICAL PROPERTIES AND OF

THE DIRECT AEROSOL RADIATIVE FORCING IN THE

SHORTWAVE AND LONGWAVE

DURING THE GROUND-BASED AND AIRBORNE

MEASUREMENTS OF AEROSOL RADIATIVE FORCING (GAMARF)

CAMPAIGN IN APRIL-MAY 2008

The EU European Fleet for Airborne Research (EUFAR) project supported 6 flights (12 hours) performed by the IMK-IFU ultralight ENDURO-KIT (P.I. dr Wolfgang Junkermann).

Two pyrgeometers measured upward and downward LW irradiance: one Kipp&Zonen CGR4 and one Eppley PIR.

GROUND-BASED MEASUREMENTS

Univ. of Barcelona CIMEL Sunphotometer

Profile of the aerosol backscatter ratio at 532 nm

F3 F5

2

4

6

8

10

DURING THE FLIGHT (6:11-8:17) AOD 500 nm = 0.60 ± 0.02

AE = 0.36 ± 0.01

DURING THE FLIGHT (6:07-8:13) AOD 500 nm = 0.14 ± 0.01

AE = 1.19 ± 0.11

METHODOLOGY

Simulation with the Modtran 4.2 model [Berk at al., 1998] of: a)Measured downward SW and LW irradiances (SW ↓ and LW↓) at surface; b)Measured LW↓ profiles; c)Aerosol-free SW and LW profiles. Calculation of surface, top of the atmosphere (TOA) and atmospheric SW and LW ADRF and ADRFE.

AEROSOL OPTICAL PROPERTIES FROM Optical Properties of Aerosol and Clouds (OPAC) database [Hess et al., 1998]: 3 MAY: Desert Dust with 98% RH 5 MAY: Continental Polluted with 98% RH

RESULTS

5 MAY 2008

RMSE (240-2700 m) = 1.8 Wm-2

Model simulations reproduce the surface downward SW and LW irradiances within measurement uncertainties.

FIRST DESCENT

SECOND ASCENT

SZA=47°

RMSE (240-2700 m) = 2.7 Wm-2

SW ADRF (Wm-2)

SW ADRFE (Wm-2)

LW ADRF (Wm-2)

LW ADRFE (Wm-2)

LW/SW (%)

TOA -19.8 -34.7 4.1 7.2 21

ATMOSPHERE 52.7 92.1 -7.6 -13.3 14

SURFACE -72.5 -126.8 11.7 20.5 16

3 MAY 2008

SW and LW simulations using:

• the aerosol size distribution from the Cimel inversion with suitable refractive index;

• the aerosol size distribution from the airborne GRIMM measurements with suitable

refractive index.

NEXT STEP

Thank you