Large High Altitude Air Shower Observatory(LHAASO), located at 29.35◦N, 100.13◦E at an
average altitude of 4410 meters on the Haizi Mountain in Daocheng County, Sichuan Province,
China, is situated in the center of Hengduan Mountains (24◦40′
-34◦00′N, 96◦20′
-104◦30′ E).
Hengduan Mountains are the transition zone of the Tibetan Plateau (TP), Sichuan Basin, and
Yunnan-Guizhou Plateau, most of which belong to TP. The topography of Hengduan Mountains
are complex, which are composed of plateau, alpine, canyon and basin and so on. They lie in the
intersection of South Asia monsoon, East Asia monsoon and westlines, also controlled by westerly
wind in winter and autumn period. The Wide-Field Cherenkov Telescope Array (WFCTA), one
of the three detector arrays at LHAASO, comprises 18 wide-field Cherenkov telescopes and is
primarily utilized to accurately measure the 1013 to 1018 eV energy spectrum of the primary cosmic
rays. The accuracy of observation of the WFCTA cosmic ray is influenced by variations in aerosols
in the atmosphere. It is importance to understand well the optical characteristics of aerosols over
the LHAASO. The solar photometer (CE-318T) was in normal operation at the LHAASO site
from October 2020 to October 2022, and a total of 394 days and 23254 sets of valid observation
data samples were obtained, excluding cloudy weather. Data analysis results after on-site field
calibration showed that the annual average aerosol optical depth at 440 nm (AOD440𝑛𝑚) was 0.05
± 0.03, and the annual average Angstrom exponent at 440-870 nm (AE440−870𝑛𝑚) was 1.17 ± 0.30.
The monthly average maximum of AOD440𝑛𝑚 occurred in April (0.11 ± 0.05) and the minimum
was in November (0.03 ± 0.01). The monthly average maximum of AE440−870𝑛𝑚 was in June (1.36
± 0.29) and the minimum was in December (0.91 ± 0.19).These results provide a basis for the
calibration of photon number and reconstruction of extensive air shower observed by WFCTA.