Radiative transfer simulations of the ATR-42 SW and LW irradiance profiles above

Lampedusa Island

Daniela Meloniwith contributions from:

ChArMEx/ADRIMED SOP1a meeting, Paris, 5-6 June 2014

ATR-42 flights above Lampedusa

22 June 28 June

22 June – F35 (descent)

AOD (500 nm)=0.38±0.02

α (500, 870)=0.53±0.03

SZA (TOP)=15°

SZA (BOTTOM)=12°

TIME (TOP)=10:23 UT

TIME (BOTTOM)=11:26 UT

28 June – F38 (descent)

AOD (500 nm)=0.213±0.004

α (500, 870)=0.76±0.03

TIME (TOP)=12:25 UT

TIME (BOTTOM)=13:30 UT

SZA (TOP)=20°

SZA (BOTTOM)=32°

Radiative transfer model simulationsMODTRAN 5.3

MODEL INPUT DATA

p, T, RH profiles ATR-42, radiosounding

Aerosol extinction profile lidar

Aerosol optical properties Cimel

Surface albedo - sea Jin et al. (2004)

Surface albedo - Lampedusa Jin et al. (2004) + MODTRAN barren

Surface emissivity MODTRAN

Sea surface temperature Italian tide gauge network

Columnar O3 Brewer

Surface CO2 Picarro

O3, CO2 profiles Mid-latitude standard atmos.

Over SEA: upward and downward SW and LW irradiance profilesOver LAMPEDUSA: downward global, direct and diffuse irradiances,

downward LW irradiance, downward WINDOW irradiance

Aerosol optical properties

AERONET retrieval of the aerosol size distribution and the spectral

refractive index (440, 500, 870, 1020 nm) closest in time to the flight

Mie calculations with AERONET size distributions

SW simulations: AERONET refractive index

LW simulations: OPAC (Hess et al., 1998) mineral refractive index

Results- 22 June - F35Downward SW irradiance

Pitch angle < 1°Roll angle < 2°

Results- F35Upward SW irradiance

Results- F35Downward LW irradiance

Results- F35Upward LW irradiance

ResultsSurface irradiances

SZA=12°

MEASUREMENT (Wm-2)

UNCERTAINTY (%)

MODEL(Wm-2)

DIFFERENCE (%)

Downward SW global

979.9 ±2.0(daily totals)

953.3 -2.7

Downward SW diffuse

220.5 ±4.0 244.9 +11.1

Direct SW 725.6 ±2.0(hourly totals)

708.4 -2.4

Downward LW 359.9 ±1.4 354.1 -1.6

Downward WINDOW

82.5 ±2.4 85.9 +4.1

Possible reasons

• Discrepancies in the measured and modeled spectral AOD

• Sphericity

• Complex refractive index (real part 1.41-1.43, imaginary part 0.004-0.006)

• Differences in columnar and in situ aerosol size distributions and refractive index.

• Differences in columnar and in situ spectral aerosol properties.

• Differences in measured and modeled direct spectral irradiances: comparison with MFRSR/ HyperOCR Satlantic/SP02 Middleton/PSR.

• Differences in measured and modeled diffuse spectral irradiances: comparison with MFRSR/ HyperOCR Satlantic.

• Differences in measured and modeled global spectral actinic fluxes: comparison with METCON DAS.

In situ size distributions 22 June – F35

Results- 28 June - F38Downward SW irradiance

Pitch angle < 1°Roll angle < 2°

Results- F38Upward SW irradiance

Results- F38Downward LW irradiance

Results- F38Upward LW irradiance

Conclusions

Preliminary comparison of ATR-42 SW and LW irradiance vertical profiles and surface measurements at Lampedusa.

To do:

• Improve the modeled spectral AOD;

• Use in situ aerosol size distributions and refractive indices;

•Compare modeled and measured spectral irradiances/actinic fluxes.