Sachiko Hayashida

Arctic polar stratospheric clouds observed with the Improved Limb Atmospheric Spectrometer during winter 1996/1997

The newest retrieval (version 4.20) of the Improved Limb Atmospheric Spectrometer (ILAS) on board the Advanced Earth Observing Satellite (ADEOS) captured more than 60 polar stratospheric cloud (PSC) profiles during the winter and early spring of 1997 in the Northern Hemisphere. That winter is well known for its long-lasting polar vortex and significant ozone loss over the Arctic. The ILAS PSC measurements were the only spaceborne measurements made on a regular basis (about 14 times daily) during that period. PSC events were selected by comparing an individual profile with a threshold value at each altitude that was defined as an average of the extinction coefficient of background aerosols plus five standard deviations. Many of the selected PSC events correspond to temperatures lower than the nitric acid trihydrate (NAT) temperature, which was calculated using nitric acid and water vapor data observed with ILAS. The correlation between the aerosol extinction coefficient and temperature shows that the extinction data increase as the temperature decreases to a point several degrees lower than the NAT temperature, suggesting the formation of particles of a supercooled ternary solution. Some of the nitric acid profiles corresponding to intense PSC events showed a decreased mixing ratio, suggesting the uptake of nitric acid in the gas-phase into particles. The highest probability of sighting PSCs was obtained in mid-January at an altitude of approximately 23 km, and subsequent occurrences of PSCs were found intermittently at lower altitudes until mid-March. The 1997 Arctic winter was characterized by the prolonged appearance of PSCs until mid-March, associated with a long-lasting polar vortex. The PSC data presented in this paper compensate for the gap in the long-term PSC record from space and help to reveal the chemical mechanisms that caused the Arctic ozone loss observed that season.

ILAS observations of chemical ozone loss in the Arctic vortex during early spring 1997

Chemical ozone loss rates were estimated for the Arctic stratospheric vortex by using ozone profile data (Version 3.10) obtained with the Improved Limb Atmospheric Spectrometer (ILAS) for the spring of 1997. The analysis method is similar to the Match technique, in which an air parcel that the ILAS sounded twice at different locations and at different times was searched from the ILAS data set, and an ozone change rate was calculated from the two profiles. A statistical analysis indicates that the maximum ozone loss rate was found on the 450 K potential temperature surface in February, amounting to 84 ppbv/day. The integrated ozone loss for two months from February to March 1997 showed its maximum of 1.5±0.1 ppmv at the surface that followed the diabatic descent of the air parcels and reached the 425 K level on March 31. This is about 50% of the initial (February 1) ozone concentration. The present study demonstrated that data from a solar occultation sensor with a moderate altitude resolution can be used for the Match analysis.

Stratospheric aerosol change in the early stage of volcanic disturbance by the Pinatubo Eruption observed over Tsukuba, Japan

An increase in the amount of stratospheric aerosol due to the Pinatubo eruption (June 12-15, 1991, 15.14[degree]N, 120.35[degree]E) was observed from the end of June by a lidar in NIES, Tsukuba (36[degree]N, 140[degree]E). The first arrival of volcanic aerosol layers was observed just above the tropopause on June 28, 1991, only two weeks after the eruption. Aerosol layers higher than 20 km appeared sporadically in July and August, reflecting the inhomogeneity of aerosol distribution. After the change in the wind system from summer easterlies to winter westerlies, the main body of the volcanic aerosol layer made its appearance over Tsukuba. The integrated backscattering coefficient (IBC) increased in winter as a result of transportation of aerosols from the tropical region. The IBC, which can be converted to optical thickness, exceeded the level of the value observed after the El Chichon eruption. 15 refs., 4 figs.

Quantum yields of O(1D) formation in the photolysis of ozone between 230 and 308 nm

[1] Ozone molecules are photolyzed in the strong photoabsorption band of the Hartley band at 230-308 nm, and the O( 3 P j ) photofragments produced by the photolysis are detected directly by a technique of laser-induced fluorescence around 130 nm. The quantum yield values for O( 1 D) formation in the photolysis of ozone at 297 ± 2 K are determined as a function of the photolysis wavelength, using the O( 1 D) quantum yield value of 0.79 at 308 nm as a reference. The O( 1 D) quantum yield values obtained are found to be almost independent of the photolysis wavelength over the Hartley band (∼0.91). The results are compared with the values measured previously using various experimental techniques and also with the recommendation values for use in atmospheric modeling. The effects of the present yield data on the O( 1 D) production rates from ozone photolysis in the stratosphere are evaluated. Impact of our new O( 1 D) quantum yield values on the stratospheric chemistry has also been explored using a one-dimensional photochemical model. The smaller O( 1 D) production rates as compared to the latest NASA/JPL recommendation values are followed by changes in the efficiency of the chemical chain reactions involving HO x , NO x , and ClO x and result in the higher O 3 concentrations throughout the stratosphere.

Comparison of aerosol extinction measurements by ILAS and SAGE II

Seventy-three pairs of nearly coincident profiles of aerosol extinction at visible wavelengths from the Improved Limb Atmospheric Spectrometer (Version 3.1) and the Stratospheric Aerosol and Gas Experiment (SAGE) II (Version 5.931) are compared for a week in January and February 1997. The comparisons require an interpolation of SAGE II multi-wavelength aerosol extinction profiles to compensate for the difference between the measurement wavelengths of the two instruments. The profiles are shown to agree within ten percent for the altitude range from approximately 15 to 24 km, with a small systematic bias that requires further study.

Development of an interactive visual data mining system for atmospheric science

In atmospheric science, 3D visualization techniques have been mainly used to create impressive presentation in recent decades. However, from the viewpoint of utilize for visual data mining, 3D visualization methodology has difficulties in becoming wide spread because most conventional and established way is to make 2D diagrams consisting of two dimensions of a temporal transitional 3D grid. From these observations, we have been developing a quick look tool of atmospheric science data for 3d visual data mining. We expect that scientists can utilize this tool for finding out 2D diagrams from the data by using various 2D or 3D visualization methods, and become accustomed themselves to 3D visualization methods.

Anti‐Correlation between stratospheric aerosol extinction and the Ångström parameter from multiple wavelength measurements with SAGE II—A characteristic of the decay period following major volcanic eruptions

Stratospheric Aerosol and Gas Experiment (SAGE) II data at multiple wavelengths were analyzed to show how aerosol extinction decays with time following major volcanic eruptions. Comparisons were made between the lowest background level in 1999 and the past data record of the stratospheric aerosol layer. The time variation of the extinction coefficients was compared with the Angstrom parameter, which is a good indicator of particle size. A clear anti-correlation was found between the extinction and the Angstrom parameter after the eruption of Mt. Pinatubo. Comparison of the extinction coefficients and Angstrom parameters in 1989 and 1999 made it clear that the aerosol layer was affected by volcanic eruptions in 1989. The distinguishing negative correlation is a characteristic feature of decay periods following volcanic eruptions.

Gravity wave activity in the upper stratosphere and lower mesosphere observed with the Rayleigh lidar at Tsukuba, Japan

We delineated the climatological characteristics of the potential energy of gravity waves, Ep, using Rayleigh lidar observations made in 1990–1991 at Tsukuba, Japan (36°N, 140°E). Tendency of large and small values of Ep in winter and summer, respectively, was detected in the upper stratosphere (30–45 km), suggesting annual variation with a winter maximum. This annual cycle seemed to be consistent with lidar observations made in France and UK [Wilson et al., 1991; Mitchell et al., 1991]. The obtained Ep values in the upper stratosphere and lower mesosphere (45–60 km) were rather similar to the French data, despite the large scatter of the Tsukuba values.

Retrieval of Asian dust amount over land using ADEOS-II/GLI near UV data

We propose a retrieval method of Asian dust (Yellow sand or Kosa aerosol) columnar amount around source regions using a near ultraviolet radiometry observation from space. The method simultaneously retrieves an optical thickness and mode radius of Kosa aerosol, and then derives its columnar amount. The method was applied to ADEOS-II / GLI data in the spring of 2003 around Taklimakan desert source region, inland China. The retrieved optical thickness and mode radius were about 0.34 and 1.75 μm, respectively, at a validation site. They are comparable to the in situ observations conducted within the framework of ADEC project. The estimated columnar amount around a validation site is about 2.77 g m-2, which seems reasonable under a relatively calm situation. The method should be further validated with a regional model simulation study, and then it is useful to monitor Asian dust around source regions from space in the future.

HCl/Cly ratios just before the breakup of the Antarctic vortex as observed by SMILES/MLS/ACE-FTS

The International Space Station/Japanese Exposure Module (ISS/JEM) borne instrument, the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES), has successfully measured chemical species in the middle atmosphere between October 2009 and April 2010. We focus on inorganic chlorine species measured inside the late spring Antarctic vortex, when hydrogen chloride (HCl) was a main component of the total inorganic chlorine (Cly). Comparisons with other satellite instruments, the Aura Microwave Limb Sounder (MLS) and Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS), are also presented to show the SMILES HCl and chlorine monoxide (ClO) data quality.