Lidar observations of polar stratospheric clouds at South Pole 2. Stratospheric perturbed conditions, 1992 and 1993

Observations of polar stratospheric clouds (PSCs), carried out at the Amundsen Scott South Pole Station by lidar from May 1992 through October 1993, are reported and compared with previously obtained results. At that time the Antarctic stratosphere was loaded with sulfuric acid aerosol due to the eruptions of Mount Pinatubo, primarily, and of Mount Hudson. The seasonal evolution of the backscatter profiles has been investigated in relation to the presence of the volcanic aerosol and to the processes of PSC formation, particle sedimentation, and dehydration. During the first winter after the eruptions the PSC activity was more intense than in the following year, particularly above 12.5 km, where the amount of volcanic aerosol was larger in 1992 than in 1993. At lower altitudes the volcanic aerosol loading as well as the PSC phenomenon were comparable during the 2 years. No substantial changes in the signal due to the volcanic aerosol has been observed comparing the backscattering profiles before and after the PSC periods (June–September), except for a downward shift, attributed to the subsidence of the air inside the polar vortex. It is concluded that only a small fraction of the aerosol particles, probably those with the largest radii, were involved in the nucleation of PSC particles

Observations of surface radiation and stratospheric processes at Thule Air Base, Greenland, during the IPY

International audienceGround-based measurements of atmospheric parameters have been carried out for more than 20 years at the Network for the Detection of Atmospheric Composition Change (NDACC) station at Thule Air Base (76.5°N, 68.8°W), on the north-western coast of Greenland. Various instruments dedicated to the study of the lower and middle polar atmosphere are installed at Thule in the framework of a long standing collaboration among Danish, Italian, and US research institutes and universities. This effort aims at monitoring the composition, structure and dynamics of the polar stratosphere, and at studying the Arctic energy budget and the role played by different factors, such as aerosols, water vapour, and surface albedo. During the International Polar Year (IPY), in winter 2008-2009, an intensive measurement campaign was conducted at Thule within the framework of the IPY project “Ozone layer and UV radiation in a changing climate evaluated during IPY” (ORACLE-O3) which sought to improve our understanding of the complex mechanisms that lead to the Arctic stratospheric O3 depletion. The campaign involved a lidar system, measuring aerosol backscatter and depolarization ratios up to 35 km and atmospheric temperature profiles from 25 to 70 km altitude, a ground-based millimeter-wave spectrometer (GBMS) used to derive stratospheric mixing ratio profiles of different chemical species involved in the stratospheric ozone depletion cycle, and then ground-based radiometers and a Cimel sunphotometer to study the Arctic radiative budget at the surface. The observations show that the surface radiation budget is mainly regulated by the longwave component throughout most of the year. Clouds have a significant impact contributing to enhance the role of longwave radiation. Besides clouds, water vapour seasonal changes produce the largest modification in the shortwave component at the surface, followed by changes in surface albedo and in aerosol amounts. For what concerns the middle atmosphere, during the first part of winter 2008-2009 the cold polar vortex allowed for the formation of polar stratospheric clouds (PSCs) which were observed above Thule by means of the lidar. This period was also characterized by GBMS measurements of low values of O3 due to the catalytic reactions prompted by the PSCs. In mid-January, as the most intense Sudden Stratospheric Warming event ever observed in the Arctic occurred, GBMS and lidar measurements of O3, N2O, CO and temperature described its evolution as it propagated from the upper atmosphere to the lower stratosphere.</p

Through the magnifying glass: provincial aspects of industrial growth in post-Unification Italy

This article presents estimates of industrial production in post-Unification Italy's 69 provinces in the census years 1871, 1881, 1901, and 1911. Initially industry was largely artisanal, and located in the former political capitals; but even then the waterfalls of the subalpine north-west attracted what factory industry there was. Contrary to widespread opinion, in the aftermath of Unification the industrial and overall growth leaders were actually in the south, where selected provinces reaped the gains from the freer foreign trade, and infrastructure investment, that accompanied the loss of independence. Over the later nineteenth century industry concentrated into the ‘industrial triangle’; but even there industrialization remained sharply local, and excluded the right bank of the upper Po. The early twentieth century, in turn, brought a measure of industrial diffusion—to the centre/north-east, where it was tied to the production of perishables on recently improved land—and concentration within the north-western triangle itself, into its major cities, as progress in energy transmission effectively moved the waterfalls into the plains