Accuracy Assessment of Digital Elevation Model Generated by SAR Stereoscopic Technique Using COSMO-Skymed Data

Radargrammetry technique using the stereoscopic synthetic aperture radar (SAR) images is used for the generation of a digital elevation model (DEM) of a region requires only the amplitude images. SAR stereoscopic technique is analogous to the stereo-photogrammetric technique where the optical stereoscopic images are used for DEM generation. While the advantages of the SAR images are their indifference to atmospheric transparency and solar illumination conditions, the side-looking geometry of the SAR increases the complexity in the SAR stereo analysis. The availability of high spatial and temporal resolution SAR data in recent years has facilitated generation of high-resolution DEM with greater vertical accuracy using radargrammetric technique. In the present study, attempt has been made to generate the DEM of Dehra Dun region, India, from the COSMO-Skymed X-band SAR data-pair acquired at 8 days interval through the radargrammetry technique. Here, radargrammetric orientation approach has been adopted to generate the DEM and various issues and processing steps with the radargrammetry technique have been discussed. The DEM was validated with ground measured elevation values using a differential global positioning system and the root-mean-square error of the DEM was found as 7.3 m. The DEM was compared with the reference DEM of the study area generated from the Cartosat-1 stereo data with a model accuracy of 4 m.     

STATE OF THE WORLD ENVIRONMENT MAPPING PROJECT

An international team of cartographers describes the initial concept and methodological principles underlying an IGU-sponsored project to compile a map of the state of the world's environments on the basis of a unified approach and guidelines. The project, which is to involve cartographers and Earth scientists throughout the world, is to provide a comprehensive characterization of the condition of marine and terrestrial ecosystems at a scale of 1:15,000,000 and is to be made available in both digital and paper formats. Translated by Edward Torrey, Alexandria, VA from: Izvestiya Akademii Nauk, seriya geograficheskaya, 1999, No. 1, pp. 108-113.     

A technique to assess dispersion

A technique to arrive at conditions congenial to maintaining a stable suspension of fine particles has been described. The technique involves continuous monitoring of apparent loss of weight of a body suspended in settling slurries. Such a technique is useful in fixing the best conditions for gravity separation of fine particles involving Bartles-Mozley concentrators or hydrocyclones.     

Atmospheric pollution in North Africa (ecosystems–atmosphere interactions): a case study in the mining basin of El Guettar–M’Dilla (southwestern Tunisia)

Air quality transcends all scales with in the atmosphere from the local to the global with handovers and feedbacks at each scale interaction. Air quality has manifold effects on health, ecosystems, heritage and climate. New insights into the characterisation of both natural and anthropogenic emissions are reviewed looking at both natural (e.g. dust and lightning) as well as plant emissions. In the phosphate mining area (El Guettar–M’Dilla basin: Southwestern Tunisia), several diseases have been known as cancer, respiratory, allergies, cardiovascular, dental fluorosis, stress, etc. These diseases are directly related with the installation of the industrial sector of the CPG (from 1896) and the deforestation and the ecosystem degradation (fauna and flora).     

Trends and fluctuations of rainfall regime in the Brahmaputra and Barak basins of Assam, India

Severe weather conditions create negative impacts on humans. One of the severe weather conditions is storms. In the scope of this study, the storm effects on the Marmara Region were investigated using data for the period 2000 to 2010 giving the hourly averaged wind direction and speed in the Marmara Region, as provided by the Turkish Meteorological Service. The monthly distribution of storms has been estimated and their daily variability has been investigated. Additionally, air masses that cause storms have been determined by using NCEP/NCAR re-analysis data. Other than this, by studying the storms, extreme values have been ascertained and northerly values from these storm values (since in percentage terms they are larger) and hourly variability in a single day for 17 weather stations have been depicted graphically. The days that northerly storms reached extreme values are shown with the meteorological maps (surface chart, 850, 700, 500, and 300 hPa) and the temperature diagrams for Istanbul in the Marmara Region have been examined and analysed.     

THE CORRELATION BETWEEN SUNSPOT AND CORONAL HOLE CYCLES AND A FORECAST OF THE MAXIMUM OF SUNSPOT CYCLE 23

We have shown in previous papers that a close relationship exists between the evolution of polar coronal hole area, estimated from K-coronameter observations, and the Wolf sunspot number, with a time lag of about half a solar cycle. In this paper we study the same relationship, but with the total coronal hole area at the base of the corona as obtained from a potential field model of the coronal magnetic field, which provides a more complete series of about three solar cycles. We confirm the relationship for the two last cycles and find that the forward time shift in the coronal hole area for the best correlation with sunspot number is almost the same for cycles 21 and 22, and this shift is also the time between peaks in both series. We use this result to make an early prediction of the time and size of the sunspot maximum for solar cycle 23, and find that this should occur early in 2001 and have a magnitude of about 190, similar to that of the two previous sunspot cycles.     

The Kuwae (Vanuatu) eruption of<Emphasis Type="SmallCaps"> AD</Emphasis> 1452: potential magnitude and volatile release

Sometime during AD 1452, according to new evidence, a large-magnitude, initially phreatomagmatic eruption, destroyed the island of Kuwae (16.83°S, 168.54°E), located in the present-day Republic of Vanuatu. It created a 12×6-km submarine caldera composed of two adjacent basins. Based on estimates of caldera volume, between 30 and 60 km³ DRE of dacite magma was ejected as pyroclastic flow and fall deposits during this event. Annual layers of ice dating from the period AD 1450–1460 contain acidity peaks representing fallout of sulfuric acid onto both the Greenland and Antarctic ice caps. These acidity peaks have been attributed by others to the sedimentation of H₂SO₄ aerosols that originated from sulfur degassing during the Kuwae eruption. Improved dating techniques and new data from nineteen ice cores reveal a single acidity peak attributed to Kuwae lasting from 1453 to 1457. In this study, we present new electron microprobe analyses of the S, Cl, and F contents of matrix glasses and glass inclusions in phenocrysts from tephra ejected during the Kuwae eruption. We establish that the Kuwae event did indeed yield a large release of sulfur gases. From our glass inclusion data and analysis, we calculate that the total atmospheric aerosol loading from the 1452 Kuwae eruption was ≫100 Tg H₂SO₄. Much of the volatile mass released during the eruption was probably contained in a separate, volatile-rich, fluid phase within the pre-eruptive Kuwae magma body. Comparing the volatile release of the Kuwae eruption with other large-magnitude eruptions, places Kuwae as the greatest sulfuric acid aerosol producer in the last seven centuries, larger even than sulfur emissions from the eruption of Tambora (Indonesia) in 1815, and possibly Laki (Iceland) in 1783. The severe and unusual climatic effects reported in the mid- to late-1450s were likely caused by the Kuwae eruption.