Kohei Mizutani

Rayleigh lidar observations of mesospheric inversion layers at Poker Flat, Alaska (65 °N, 147°W)

Rayleigh lidar measurements of the stratosphere and mesosphere have been made on an ongoing basis over a three-year period at Poker Flat, Alaska (65°N, 147°W). These observations have yielded 27 nightly measurements of the middle atmosphere temperature profile (∼ 40–80 km). These nighttime measurements are distributed between August and April. Mesospheric inversion layers have been observed on five occasions. The average altitude of the inversion layer peak is 60 km, with average amplitude of 18 K. The temperature gradients on the topside of the inversion layers approach the adiabatic lapse rate. The inversion layers do not exhibit the apparent downward phase velocities that are commonly observed at lower latitudes. Furthermore, the inversion layers appear significantly less frequently than at lower latitudes. The observations are discussed in terms of current models and observations at other sites.

Stratospheric ozone changes at 43°N And 36°N over Japan between 1991 and 1994

Total ozone and ozonesonde profiles obtained from Sapporo (43°N) and Tsukuba (36°N), Japan showed significant ozone decreases in 1992 and 1993, coinciding with the large increase of aerosol loading from the Pinatubo eruption. The ozone anomaly in Sapporo was deeper and longer lasting than in Tsukuba, indicating a latitudinal variation. The ozone decrease occurred mainly below 24 km and was most pronounced in winter and spring. In addition, the altitude regions where significant ozone decreases occurred, descended between 1992 and 1994 coincident with the descent of the Pinatubo aerosol layer. Some increase in ozone was seen above 26 km at the two stations in the winter and spring of 1992. These ozone changes are indicative of heterogeneous chemical effects on ozone under perturbed aerosol loading.

Laser-ranging scanning system to observe topographical deformations of volcanoes.

We have developed a laser-ranging system to observe the topographical structure of volcanoes. This system can be used to measure the distance to a target by a laser and shows the three-dimensional topographical structure of a volcano with an accuracy of 30 cm. This accuracy is greater than that of a typical laser-ranging system that uses a corner-cube reflector as a target because the reflected light jitters as a result of inclination and unevenness of the target ground surface. However, this laser-ranging system is useful for detecting deformations of topographical features in which placement of a reflector is difficult, such as in volcanic regions.

2-um Coherent Lidar Technology Developed at NICT: Past, Current, and Future

We present a development and research of the 2-µm coherent lidar with a conductively-cooled laser-diode-pumped single-frequency Q-switched Tm,Ho:YLF pulse laser developed at the NICT.

Development of coherent Doppler lidar at CRL

Global wind profiling with a space-borne Doppler lidar is expected to bring big progress in the studies on global climate change and Numerical Weather Prediction. A feasibility study has been done for an eye-safe 2micron coherent Doppler lidar aiming at demonstration of the technology onboard the Japanese Experiment module of the International Space Station. We are now developing an airborne coherent Doppler lidar system to measure wind profile under a jet plane for simulation of the Doppler lidar measurement in space. This system is also operated in the ground to develop algorithm of the wind measurements and the results of the wind profiles are compared with those derived from other instruments.

Lidar Observations of the PSCs and Stratospheric Aerosols over Eureka in Canadian Arctic

The behavior of the polar stratospheric clouds, PSCs, and the stratospheric aerosols is very important to understand the ozone destruction in the polar stratosphere. Lidar observations of the PSCs and stratospheric aerosols have been carried out at the Arctic stratospheric ozone observatory, AStrO, near the Eureka weather station at 80°N, 86°W since February 1993, using a depolarization sensitive NdrYAG lidar. During the four winter campaigns from February 1993 to February 1996, no PSC was observed in the winter of 1992/1993 and 1993/1994, however, several PSC events were observed in the winter of 1994/1995 and 1995/1996. The first event appeared on December 12, 1994 and continued to December 16, 1994. The PSCs in this event are categorized into the TYPE la, which is considered to be crystallized nitric acid trihydrate (NAT) particles. The second event happened from January 5 and 14, 1995, with a short disappeared period on 10 and 11. In the later event, less depolarized component hung down to about 14 km altitude from the main peak, where the TYPE la existed, with higher depolarization around 20 km. The temperature in the hung down region was obviously higher than the freezing point of the NAT. This suggests that the compositions of the PSCs are not only NAT and/or ice but also other species such as sulfuric acid tetrahydrate (SAT) and sulfuric acid dihydrate (SAD) particles.

Development of conductively cooled Tm,Ho:YLF MOPA for lidar applications

The realization of three-dimensional global wind profile measurements provides significant benefits, such as improvement in the precision of numerical weather forecasts and understanding of the causes of climate change. A spaceborne coherent Doppler wind lidar is considered to be the most powerful instrument for providing accurate tropospheric wind profiles with high spatial and temporal resolutions. Conductively cooled techniques are also important for spaceborne lidar applications because they have several advantages over liquid cooling systems. The National Institute of Information and Communications Technology (NICT) is conducting feasibility studies of conductively cooled, Q-switched 2 μm Tm,Ho:YLF lasers to meet a requirement for a spaceborne CDWL. In recent years, the energy extraction efficiency from Tm,Ho:YLF lasers has been improved dramatically by reviewing the laser rod parameters and the resonator design. In this study, we report on a single-frequency, Q-switched Tm,Ho:YLF master oscillator power amplifier (MOPA), which meets the specifications of a spaceborne CDWL transmitter. The MOPA consists of a 3.86-mlong ring oscillator and a single-pass amplifier. For the single-pass amplification, an average output power of 3.95 W, which corresponds to a pulse energy of 131.7 mJ, was obtained at a pulse repetition frequency of 30 Hz and a cooling temperature of -40°C.

Efficient, Room-Temperature Tm,Ho:GdVO 4 Microchip Laser

A diode-pumped Tm,Ho:GdVO4microchip laser demonstrated an output power of 0.55 W and a conversion efficiency of 23.7%. To our knowledge, it is the highest efficiency reported for Tm:Ho-codoped vanadate lasers operating near room temperature.

Coherent Doppler wind lidar for the Japanese experimental module of the ISS

A feasibility study has been done for a space-borne 2micron coherent Doppler lidar system aiming at demonstration of the technology onboard the Japanese Experiment module of the International Space Station. We are also developing an airborne coherent Doppler lidar system for simulation of the Doppler lidar measurement in space.

Seasonal variation of aerosol over Bandung, Indonesia

Variation of stratospheric aerosol affects atmospheric minor constituents and climate through changes in the radiation field as well as by dynamic and chemical processes. In order to estimate the impact quantitatively, it is very important to observe stratospheric aerosol vertical distribution and their lime variation To obtain stratospheric aerosol especially in equatorial region a lidar was installed in Bandung (6.9° S; 107.7° E) Indonesia under collaboration between National Institute of Aeronautic and Space (LAPAN), Communication Research Laboratory of Japan and Meteorological Research Institute of Japan. The Lidar transmitter system employ fundamental (1064 nm), second harmonic (532 nm) and third harmonic (355 am) wavelengths ofNd: YAG laser are transmitted. The second harmonic backscatter light and its N2 ranian backscatter light (607 am) are collected by a 28 cm and a 35 cm diameter telescope. In 35 cm telescope system, upper troposphere and stratosphere are observed by photon counting. 532 am light component polarized parallel and perpendicular to the laser light are separately observed to get information about shape of aerosol. Bandung is located at around 750 m above mean sea level and it is surrounded by mountains, therefore clouds are easily formed especially between 10 and 17 km height. Stratospheric aerosol over Bandung are spreaded between 18 and 35 km in altitude and form more than 1 sub layer, below 30 km and upper 30 km. The maximum aerosol concentration is obtained around 22.5 km height. To understand the seasonal variation of stratospheric aerosol we integrated the backscattering coefficients for altitude range 18-35 km and it was obtained that the stratospheric aerosol concentration in 1997 was higher than in 1999. The integrated backscattering coefficient in June was higher than in August. But seems the seasonal variation of integrated backscattering coefficient in Bandung does not so clear determined yet.