Observation apparatus and atmospheric state determination method

An observation apparatus comprising:

• a deep ultraviolet light source configured to transmit pulse light having a wavelength belonging to an ultraviolet region of a solar blind band;
• a photodetector configured to output a pulse of which a wave height changes according to the number of photons of reflected light of the pulse light received within a response period;
• and
• a threshold setting unit, a wave height determinator, a LiDAR data generation unit, a pulse number integration unit, a threshold distribution generation unit, and an atmospheric state determination unit, wherein
• the threshold setting unit sets a different threshold for the wave height determinator for each measurement period, and during the measurement period, the wave height determinator determines and outputs a pulse having a wave height equal to or more than the threshold among pulses output from the photodetector,
• the LiDAR data generation unit generates, for each measurement period, LiDAR data in which the number of pulses having a wave height equal to or more than the threshold set in the measurement period and output from the wave height determinator is aggregated for each distance,
• the pulse number integration unit integrates a total number of pulses within a predetermined distance range in the LiDAR data for each piece of the LiDAR data,
• the threshold distribution generation unit generates a threshold distribution obtained by aggregating, for each threshold, the total number of pulses integrated for each of the LiDAR data, and
• the atmospheric state determination unit determines an atmospheric state by comparing the threshold distribution with a reference threshold distribution.