30-year lidar observations of the stratospheric aerosol layer state over Tomsk (Western Siberia, Russia)

There are only four lidar stations in the world which have almost continuously performed observations of the stratospheric aerosol layer (SAL) state over the last 30 years. The longest time series of the SAL lidar measurements have been accumulated at the Mauna Loa Observatory (Hawaii) since 1973, the NASA Langley Research Center (Hampton, Virginia) since 1974, and Garmisch-Partenkirchen (Germany) since 1976. The fourth lidar station we present started to perform routine observations of the SAL parameters in Tomsk (56.48° N, 85.05° E, Western Siberia, Russia) in 1986. In this paper, we mainly focus on and discuss the stratospheric background period from 2000 to 2005 and the causes of the SAL perturbations over Tomsk in the 2006–2015 period. During the last decade, volcanic aerosol plumes from tropical Mt. Manam, Soufrière Hills, Rabaul, Merapi, Nabro, and Kelut and extratropical (northern) Mt. Okmok, Kasatochi, Redoubt, Sarychev Peak, Eyjafjallajökull, and Grímsvötn were detected in the stratosphere over Tomsk. When it was possible, we used the NOAA HYSPLIT trajectory model to assign aerosol layers observed over Tomsk to the corresponding volcanic eruptions. The trajectory analysis highlighted some surprising results. For example, in the cases of the Okmok, Kasatochi, and Eyjafjallajökull eruptions, the HYSPLIT air mass backward trajectories, started from altitudes of aerosol layers detected over Tomsk with a lidar, passed over these volcanoes on their eruption days at altitudes higher than the maximum plume altitudes given by the Smithsonian Institution Global Volcanism Program. An explanation of these facts is suggested. The role of both tropical and northern volcanic eruptions in volcanogenic aerosol loading of the midlatitude stratosphere is also discussed. In addition to volcanoes, we considered other possible causes of the SAL perturbations over Tomsk, i.e., the polar stratospheric cloud (PSC) events and smoke plumes from strong forest fires. At least two PSC events were detected in 1995 and 2007. We also make an assumption that the Kelut volcanic eruption (Indonesia, February 2014) could be the cause of the SAL perturbations over Tomsk during the first quarter of 2015

Crystal structure of bis(η5-cyclopenta-dienyl)(1,4-di-tert-butylbuta-1-en-3-yn-1-yl) zirconium(IV) μ2-hydroxido-bis[tris-(pentafluorophenyl) borate]

Alkyl zirconocene cations have been of considerable inter­est as reactive species in many polymerization processes. In the crystal structure of the title compound, [Zr(C12H19)(C5H5)2](C36HB2F30O), the [Zr(C5H5)2((t-Bu)C=C(H)-C2(t-Bu))]+ cation displays a buta-1-en-3-yne ligand side-on coordinated to a typical bent zirconocene [centroid(cp)-Zr-centroid(cp) = 131.4 (3)°, Zr-C(buta-1-en-3-yne) = 2.255 (3), 2.597 (3) and 2.452 (2) Å]. In the [HO(B(C6F5)3)2]- anion, intra­molecular O-H...F hydrogen bonds are observed. One tert-butyl group in the complex cation is disordered over two sets of sites with occupancies 0.701(4):0.299(4)

Crystal structure of di-n-but­yl­bis­([eta]5-penta­methyl­cyclo­penta­dien­yl)hafnium(IV)

The crystal structure of the title compound, [Hf(C10H15)2(C4H9)2], reveals two independent mol­ecules in the asymmetric unit. The diffraction experiment was performed with a racemically twinned crystal showing a 0.529 (5):0.471 (5) component ratio. Each HfIV atom is coordinated by two penta­methyl­cyclo­penta­dienyl and two n-butyl ligands in a distorted tetra­hedral geometry, with the cyclo­penta­dienyl rings inclined to one another by 45.11 (15) and 45.37 (16)°. In contrast to the isostructural di(n-butyl)bis([eta]5-penta­methyl­cyclo­penta­dien­yl)zirconium(IV) complex with a noticeable difference in the Zr-butyl bonding, the Hf-Cbut­yl bond lengths differ from each other by no more than 0.039 (3) Å

Crystal structure of bis(η5-cyclopenta-dienyl)(2, 3-diethylbutane-1, 4-diyl)-hafnium(IV)

The title compound, [Hf(C5H5)2(C8H16)], proves a structural motif of hafna­cyclo­pentane besides the coordination of two cyclo­penta­dienyl ligands in an [eta]5-fashion. The hafna­cyclo­pentane ring has a twist conformation and is substituted by two ethyl groups in the [beta],[beta]'-positions, which are trans orientated to each other. One cyclo­penta­dienyl ring and one ethyl group are each disordered over two positions with site-occupancy ratios of 0.679 (15):0.321 (15) and 0.702 (18):0.298 (18), respectively

Lidar measurements of ozone in the upper troposphere - lower stratosphere at Siberian lidar station in Tomsk

The paper presents the results of DIAL measurements of the vertical ozone distribution at the Siberian lidar station. Sensing is performed according to the method of differential absorption and scattering at wavelength pair of 299/341 nm, which are, respectively, the first and second Stokes components of SRS conversion of 4th harmonic of Nd:YAG laser (266 nm) in hydrogen. Lidar with receiving mirror 0.5 m in diameter is used to implement sensing of vertical ozone distribution in altitude range of 6-16 km. The temperature correction of zone absorption coefficients is introduced in the software to reduce the retrieval errors

Measurement of ozone concentration in the lower stratosphere - upper troposphere

We describe an ozone lidar and consider an algorithm for retrieving the ozone concentration, taking into consideration the aerosol correction. Results of lidar measurements at wavelengths 299 and 341 nm well agree with model estimates, indicating that ozone is sensed with acceptable accuracies in the altitude range of about 6-18 km. It should be noted that the retrieved profiles of altitude distribution of ozone concentration more closely resemble those from satellite data than according to Krueger model. A lidar is developed and put into operation at Siberian Lidar Station (SLS) to measure the vertical ozone distribution (VOD) in the upper troposphere-lower stratosphere. Sensing is performed according to the method of differential absorption and scattering at wavelength pair 299/341 nm, which are respectively the first and second Stokes components of stimulated Raman scattering (SRS) conversion of the fourth harmonic of Nd:YAG laser (266 nm) in hydrogen

DIAL measurements of the vertical ozone distribution at the Siberian lidar station

The paper presents the results of DIAL measurements of the vertical ozone distribution at the Siberian lidar station. Sensing is performed according to the method of differential absorption and scattering at wavelength pair of 299/341 nm, which are, respectively, the first and second Stokes components of SRS conversion of 4th harmonic of Nd:YAG laser (266 nm) in hydrogen. Lidar with receiving mirror 0.5 m in diameter is used to implement sensing of vertical ozone distribution in altitude range of 6-16 km. The temperature correction of zone absorption coefficients is introduced in the software to reduce the retrieval errors

Reduction of 1,4-dichlorobut-2-yne by titanocene to a 1,2,3-butatriene. Formation of a 1-titanacyclopent-3-yne and a 2,5-dititanabicyclo[2.2.0]hex-1(4)-ene

The 2,5-dititanabicyclo[2.2.0]hex-1(4)-ene (bis-titanocene-μ-(Z)-1,2,3-butatriene complex) (3) is formed starting from [Cp2Ti(η2-Me3SiC2SiMe3)] by in situ generated titanocene and 1,4-dichlorobut-2-yne via the 1-titanacyclobut-3-yne (2)

Tris(η5-cyclo­penta­dien­yl)hafnium(III)

In the crystal structure of the title compound, [Hf(C5H5)3], three cyclo­penta­dienyl ligands surround the HfIII atom in a trigonal–planar geometry. The mol­ecule lies on a sixfold inversion axis