Takatsugu Matsumura

Ice clouds and Asian dust studied with lidar measurements of particle extinction-to-backscatter ratio, particle depolarization, and water-vapor mixing ratio over Tsukuba

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 (Sp) showed a dependence on the relative humidity with respect to ice (RHice) obtained from the lidar-derived water-vapor mixing ratio and radiosonde-derived temperature; they were mostly higher than 30 sr in dry air (RHice < 50%), whereas they were mostly lower than 30 sr in ice-supersaturated air (RHice > or = 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 Sp on RHice 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.

Comparisons of Raman Lidar Measurements of Tropospheric Water Vapor Profiles with Radiosondes, Hygrometers on the Meteorological Observation Tower, and GPS at Tsukuba, Japan

Abstract The vertical distribution profiles of the water vapor mixing ratio (w) were measured by Raman lidar at the Meteorological Research Institute, Japan, during the period from 2000 to 2004. The measured values were compared with those obtained with radiosondes, hygrometers on a meteorological observation tower, and global positioning system (GPS) antennas near the lidar site. The values of w obtained with the lidar were lower than those obtained with the corrected Meisei RS2-91 radiosonde by 1.2% on average and higher than those obtained with the corrected Vaisala RS80-A radiosonde by 17% for w ≥ 0.5 g kg−1. The lidar data were higher than those radiosondes’ data by 19% or 33% for w < 0.5 g kg−1. The vertical variations of w obtained with the lidar differed from those obtained with the Meisei RS-01G radiosonde and Meteolabor Snow White radiosonde by 5% on average for w ≥ 0.5 g kg−1. The lidar data were lower than those radiosondes’ data by 37% or 39% for w < 0.5 g kg−1. The temporal variations of w o...

Optical and Microphysical Properties of Upper Clouds Measured with the Raman Lidar and Hydrometeor Videosonde: A Case Study on 29 March 2004 over Tsukuba, Japan

Abstract Optical and microphysical properties of the upper clouds at an altitude range of 5–11 km were measured over Tsukuba, Japan, on 29–30 March 2004 using a ground-based Raman lidar and a balloon-borne hydrometeor videosonde (HYVIS). The Raman lidar measured the vertical distributions of the particle extinction coefficient, backscattering coefficients, depolarization ratio, and extinction-to-backscatter ratio (lidar ratio) at 532 nm; further, it measured the water vapor mixing ratio. The HYVIS measured the vertical distributions of the particle size, shape, cross-sectional area, and number concentration of the cloud particles by taking microscopic images. The HYVIS measurement showed that the cloud particles were ice crystals whose shapes were columnar, bulletlike, platelike, and irregular, and 7–400 μm in size. The Raman lidar measurement showed that the depolarization ratio ranged from 0% to 35% and the lidar ranged from 0.3 to 30 sr for the clouds in ice-saturated air. The comparison between the me...

Hygroscopic Growth of an (NH 4 ) 2 SO 4 Aqueous Solution Droplet Measured Using an Environmental Scanning Electron Microscope (ESEM)

The contact angle, θ, and volume equivalent diameter of an (NH4)2SO4 aqueous droplet was measured using an environmental scanning electric microscope (ESEM), showing the hygroscopic growth of the solution droplet as the relative humidity (RH) increased from 80% to 98%. (NH4)2SO4 particles with diameters in the range 1–2 μ m were produced by an atomization technique, and collected onto a copper substrate that had been treated with polytetrafluoroethylene. To observe the hygroscope growth, the sample chamber of the ESEM was filled with water vapor at a pressure of 600 Pa, and the sample temperature was adjusted using a cooling stage to control the relative humidity inside the chamber. Before the observation of the hygroscopic growth, we determined the value of θ from overhead views of droplets on the stage at a tilted angle of 45°. The average value of θ was 96 ± 10°, and this value was used to estimate the droplet diameter. We measured the diameter of the (NH4)2SO4 droplets at different RH, and observed that the growth factor, G, increased with increasing RH. The experimental value of G was consistent with the theoretically estimated value. This shows that our method for determining the value of θ was valid, and that the ESEM technique can be used to measure the diameters of droplets of aqueous solutions.

Comparisons of the Raman lidar measurements of the tropospheric water vapor profiles with radiosondes, meteorological observation tower, and GPS at Tsukuba, Japan

The vertical distributions of the water vapor mixing ratio (w) were measured by Raman lidar at the Meteorological Research Institute, Japan, in 2000 to 2004. The measured values were compared with those obtained with radiosondes, hygrometers on the meteorological observation tower, and Global Positional System (GPS) antennas. The values of w obtained with the lidar agreed within 9% with those obtained with the Meisei RS2-91 radiosonde for w > 0.5 g/kg-1. However, they were systematically higher than those obtained with the Vaisala RS80-A radiosonde for that region. The vertical variations of w obtained with the lidar were similar to those obtained with the Meisei RS-01G and Meteolabor Snow White radiosondes for w > 0.3 g/kg-1. The temporal variations of w obtained with the lidar were similar to those obtained with the hygrometers at heights between 50 and 213 m on the tower, although the absolute values differed systematically due to the incomplete overlap of the laser beam and the receivers field of view at the lower heights. The precipitable water vapor content obtained with the lidar generally agreed with those obtained with GPS, except for the period when the large spatial inhomogeneity of w was present.

Lidar and Optical Particle Counter (OPC) measurements of polar and tropical stratospheric aerosols

Lidar and Optical Particle Counter (OPC) measurements were performed in the Canadian Arctic and in the Indonesian Tropical region. The observations yielded very interesting and important results about the features of the latitudinal difference in the stratospheric aerosols. Besides the latitudinal difference, the aerosol distributions and their time variation showed unique characteristics in each of the regions. In Arctic winter, the aerosol concentration varies frequently day-to-day. In the Tropical region, the aerosol distribution and the vertical transport is, probably, controlled by the variation of the circulation pattern in the lower stratosphere related to the QBO in the tropical stratosphere. Based on the results of the simultaneous measurements by lidar and OPCs, we estimated surface area density, volume density, S-parameter (extinction to backscatter ratio), backscatter to surface area conversion factor, and backscatter to volume conversion factor of the stratospheric aerosols at 20km-altitude in the Arctic and Tropical regions.

Comparison of lidar measurement with balloonborne OPC measurement over Bandung, Indonesia

For the study of stratospheric aerosol over the Tropics, balloon-borne OPC measurements have been made six times from April 1997 to March 2000 at Bandung, Indonesia (6.9 deg S, 107.6 deg E)where Lidar measurements have also been made since early 1997. Correlative measurements of Lidar and OPC were conducted on March 25, 1998 and August 23, 1999. Results of the latter measurement were compared in this paper. The profile of back scattering ratio measured by Lidar almost represents a vertical distribution of small particles having radii smaller than 0.4 μm. We calculated back scattering coefficients from the results of OPC measurement. The calculated and measured back scattering coefficients were not consistent completely but not so unreasonable.