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We have developed a 1.6 μm carbon dioxide (CO_2) differential absorption lidar utilizing a quasi-phase-matching optical parametric oscillator (OPO) and a photon-counting detector. The operating wavelengths were chosen based on their low interference from water vapor and low temperature sensitivity. The online wavelength was in the (30012?0001) band of CO_2, which was insensitive to atmospheric temperature. The established OPO laser achieved a 10 mJ, 200 Hz repetition rate at the online and offline wavelengths. Our observations confirmed the statistical error of 2% with 5 h of accumulation for the CO_2 density profile less than 5.2 km. Also, the statistical error of 1% at an altitude of 2 km was demonstrated. The results of the vertical CO_2 concentrations acquired using a 1.6 μm wavelength are presented.

A UV ozone differential-absorption lidar (DIAL) utilizing a Nd:YAG laser and a single Raman cell filled with carbon dioxide (CO_2) is designed, developed, and evaluated. The generated wavelengths are 276, 287, and 299 nm, comprising the first to third Stokes lines of the stimulated Raman scattering technique. The correction terms originated from the aerosol extinction, the backscatter, and the absorption by other gases are estimated using a model atmosphere. The experimental results demonstrate that the emitted output energies were 13 mJ/pulse at 276 nm and 287 nm and 5 mJ/pulse at 299 nm, with pump energy of 91 mJ/pulse and a CO_2 pressure of 0.7 MPa. The three Stokes lines account for 44.0% of the available energy. The use of argon or helium as a buffer gas in the Raman cell was also investigated, but this leads to a dramatic decrease in the third Stokes line, which makes this wavelength practically unusable. Our observations confirmed that 30 min of integration were sufficient to observe ozone concentration profiles up to 10 km. Aerosol extinction and backscatter correction are estimated and applied. The aerosol backscatter correction profile using 287 and 299 nm as reference wavelengths is compared with that using 355 nm. The estimated statistical error is less than 5% at 1.5 km and 10% at 2.6 km. Comparisons with the operational carbon-iodine type chemical ozonesondes demonstrate 20% overestimation of the ozone profiles by the DIAL technique.

The tropospheric particle extinction-to-backscatter ratio, the depolarization ratio, and the water-vapor mixing ratio were measured by use of a Raman lidar and a polarization lidar during the Asian dust seasons in 2001 and 2002 in Tsukuba, Japan. The apparent (not corrected for multiple-scattering effects) extinction-to-backscatter ratios (S_p) showed a dependence on the relative humidity with respect to ice (RH_ice) obtained from the lidar-derived water-vapor mixing ratio and radiosonde-derived temperature; they were mostly higher than 30 sr in dry air (RH_ice < 50%), whereas they were mostly lower than 30 sr in ice-supersaturated air (RH_ice ≥ 100%), where the apparent extinction coefficients were larger than 0.036 km^-1. Both regions showed mean particle depolarization ratios of 20%–22%. Comparisons with theoretical calculations and the previous experiments suggest that the observed dependence of S_p on RH_ice is attributed to the difference in the predominant particles: nonspherical aerosols (mainly the Asian dust) in dry air and cloud particles in ice-supersaturated air.