Extremely fresh biomass burning aerosol observed in Potenza by multiwavelength Raman Lidar MUSA and the CIMEL 318 sun-photometer.

On 14 August 2021 a forest fire started at 16:00 U.T.C. were observed by the Lidar Raman MUSA and the CIMEL 318 sun-photometer of CNR IMAA of Potenza located at 1 km from the fire. Due to proximity to only 1 km this measurements represents an important case of study. Measurements carried out by the Lidar MUSA  reveal the presence of a smoke layer below 2.7 km  from 22:27 to 23:19 the. The optical parameters derived are backscattering at 355, 532 and 1064 nm, extinction at 355 and 532 nm, Lidar ratios at 355 and 532 nm wavelengths, Ångström exponents,  and particle and volume depolarization at 532 nm. Results indicate a low absorption  an high scattering of fire particles.

Lidar ratio are 40 sr at 355 and 38 at 532, particle depolarization is 0.025 and Ångström exponents are approx 1.5 for all wavelengths.

To derive microphysical properties are used The inversion of 3 β + 2 α. The values of surface concentration is 410 µm² cm^-3, the volume concentration is 21 µm³ cm^-3and numeric density is  2300 cm^-3. The size distribution is  bi-modal distribution with a peak at 0.13 µm. The effective radius is 0.15 µm. The single scattering albedo at 355, 532 and 1064 are 0.96, the real and the imaginary part of the refractive index are respectively 1.58 and 0.006.

Therefore, particles are small, spherical and weakly absorbing probably due to a minimum contribution of black carbon

The CIMEL 318 sun photometer measurements at 5:34 U.T.C confirm the results of MUSA.