Diurnal temperature variations in the lower troposphere as measured by an all-day-operational pure rotational Raman lidar

摘要

We describe a pure rotational Raman lidar for measuring the all-day temperature profiles in the lower troposphere. The lidar is made up of a frequency-tripled Nd:YAG laser at 354.82 nm with similar to 250 mJ pulse energy at the 30 Hz repetition rate, a 200 mm receiving telescope, and narrow-band interference-filter-based detection optics. The lidar performance is shown by measured examples. Under clear sky conditions, with an integration time of 60 min and a vertical resolution of 90 m, the 1-sigma statistical uncertainty does not exceed 1 K up to the altitude of similar to 4.1 km during nighttime, while the corresponding altitude is similar to 2.3 km at noon. The diurnal temperature variation characteristics have been revealed by the lidar measurements with the 1-sigma statistical uncertainty <1 K between altitudes ranging from 0.6 to similar to 2.0 km at Wuhan, China (30.53 degrees N, 114.37 degrees E). The atmospheric temperature shows a strong diurnal oscillation and moderate semidiurnal oscillation at altitudes 0-1.4 km for two days in July 2019 (July period), 0-1.4 km for four days in September 2019 (September period), and 0-0.8 km for three days in January 2018 (January period), respectively. The mean diurnal and semidiurnal amplitudes of the nine days are respectively similar to 1.4 K and similar to 0.5 K at the 0.6 km altitude, while the corresponding surface values are similar to 4.2 K and similar to 1.4 K, respectively. The diurnal amplitudes tend to weaken with increasing altitude. At altitudes >0.6 km, the diurnal amplitude in the September period is less than that in the July period, but greater than that in the January period. The phase delays of the diurnal oscillations are similar to 3 h in the July period, 5-6 h in the September period, and 5-7 h in the January period compared to those at the surface, respectively. Both the diurnal amplitudes and phase delays indicate a possible seasonal dependence. (C) 2020 Optical Society of America