Construction and characterization of an atmospheric simulation smog chamber

Currently, air pollution in Beijing has become a complex problem with two types of source pollutants： coal smoke and photochemical smog. Furthermore the maximum hourly mean concentration of O3 increases continuously, especially in the summer. In order to simulate the photochemical reaction, develop an air quality simulation model and further improve the air quality of Beijing, a precisely temperature-controlled, indoor, smog chamber facility was designed and constructed at Tsinghua University. Characterization experiments have been carried out to acquire the basic parameters of the smog chamber, such as the wall loss rates of NO2, NO, O3, C3H6 and particulate matter （PM）, the intensity of ultraviolet （UV） light in the chamber, the reactivity of the purified air and the reproducibility of the experimental results. The results indicate that the facility performs up to specifications, and can meet the demands required for simulating the photochemical reaction. The effect of high primary contaminated PM on the formation of ozone and secondary organic aerosol （SOA） is under investigation.     

Progress Report on the Deployment of MAGDAS

As Japan’s leading contribution to the International Heliophysical Year (IHY), the Space Environment Research Center (SERC) of Kyushu University, Fukuoka, Japan is in the process of deploying globally 50 state-of-the-art magnetometers. In this brief article, we outline our progress to date (23 Sept 2007). We also briefly describe our magnetometer, which is able to send its data in near realtime to a central server, where data from all units can be compared with relative ease and quickness.     

The structure and behavior of the arctic cyclone in summer analyzed by the JRA-25/JCDAS data

In this study, three-dimensional structures and the life-time behavior of arctic cyclones are investigated as case studies, using reanalysis data of JRA-25 and JCDAS. In recent years, arctic region has undergone drastic warming in conjunction with the reduced sea ice concentration in summer. The rapid reduction of the sea ice concentration is explained, to some extent, by a pressure dipole of the arctic cyclone and Beaufort high over the Arctic Ocean. This paper presents some case studies for the structure of the arctic cyclone.It is found by the analysis of this study that the arctic cyclone indicates many differences in structure and behavior compared with the mid-latitude cyclone. The arctic cyclones move rather randomly in direction over the Arctic Ocean. The arctic cyclone has a barotropic structure in the vertical from the surface to the stratosphere. The arctic cyclone detected at the sea level pressure is connected with the polar vortex at the 500 hPa level and above. Importantly, the arctic cyclone has a cold core in the troposphere and a warm core around the 200 hPa level. The mechanism of the formation is discussed based on the analyzed structure of the arctic cyclones.     

Changes in climate classification and extreme climate indices from a high-resolution future projection in Korea

We investigate the future changes in the climate zone and six extreme temperature indices in Korea, using the 20-km high-resolution atmospheric general circulation model (MRI-AGCM3.1S). The Trewartha and K?ppen climate classification schemes are applied, and four summer-based extreme temperature indices (i.e., summer days, tropical nights, growing degree days, and cooling degree days (CDD) and two winter-based indices (frost days and heating degree days (HDD) are analyzed. To represent significantly the change in threshold indices, the monthly mean bias is corrected in model. The model result reasonably captures the temporal and spatial distribution of the present-day extreme temperatures associated with topography. It was found that in the future climate, the area of the subtropical climate zone in Korea expands northward and increases by 21% under the Trewartha classification scheme and by 35% under the K?ppen classification scheme. The spatial change in extreme climate indices is significantly modulated by geographical characteristics in relation to land-ocean thermal inertia and topographical effects. The change is manifested more in coastal regions than in inland regions, except for that in summer days and HDD. Regions with higher indices in the present climate tend to reveal a larger increase in the future climate. The summer-based indices display an increasing trend, while the winter-based indices show a decreasing trend. The most significant increase is in tropical nights (+452%), whereas the most significant decrease is in HDD (?25%). As an important indicator of energy-saving applications, the changes in HDD and CDD are compared in terms of the frequency and intensity. The future changes in CDD reveal a higher frequency but a lower temperature than those in HDD. The more frequent changes in CDD may be due to a higher and less dispersed occurrence probability of extreme temperatures during the warm season. The greater increase in extreme temperature events during the summer season remains an important implication of projecting future changes in extreme climate events.     

Dynamic modeling of forest conversion: Simulation of past and future scenarios of rural activities expansion in the fringes of the Xingu National Park,Brazilian Amazon

The present work is committed to simulate the expansion of agricultural and cattle raising activities within a watershed located in the fringes of the Xingu National Park, Brazilian Amazon. A spatially explicit dynamic model of land cover and land use change was used to provide both past and future scenarios of forest conversion into such rural activities, aiming to identify the role of driving forces of change in the study area. The employed modeling platform – Dinamica EGO – consists in a cellular automata environment that embodies neighborhood-based transition algorithms and spatial feedback approaches in a stochastic multi-step simulation framework. Biophysical variables and legal restrictions drove this simulation model, and statistical validation tests were then conducted for the generated past simulations (from 2000 to 2005), by means of multiple resolution fitting methods. Based on optimal calibration of past simulations, future scenarios were conceived, so as to figure out trends and spatial patterns of forest conversion in the study area for the year 2015. In all simulated scenarios, pasturelands remained nearly stable throughout the analyzed period, while a large expansion in croplands took place. The most optimistic scenario indicates that more than 50% of the natural forest will be replaced by either cropland or pastureland by 2015. This modeling experiment revealed the suitability of the adopted model to simulate processes of forest conversion. It also indicates its possible further applicability in generating simulations of deforestation for areas with expanding rural activities in the Amazon and in tropical forests worldwide.     

Direct evidence for nitrogen isotope discrimination during sedimentation and early diagenesis in Lake Kasumigaura, Japan

Sediment core samples from the center of Lake Kasumigaura, Japan, were collected from 1979 to 2007 at intervals of 1 month to 5 yr. We evaluated the degree of modification in N isotope composition during sedimentation and diagenesis. We estimated the degree of isotope discrimination during diagenesis by comparing historical changes in N isotope composition of the surface sediment (top 2 cm) against the vertical profile of the isotope composition of sediment core samples (15 cm depth). The degree of ¹⁵N enrichment during sedimentation appeared to be significant under the preferential N decomposition that occurred in the periods with low C/N ratio values of suspended particulate organic matter. We documented ¹⁵N depletion in sediment deeper than approximately 3 cm during diagenesis. The contrasting directions of N isotope discrimination during sedimentation and diagenesis suggest changing mechanisms of isotopic shift across an oxidation-reduction boundary.     

Paleoecology of Inoceramus amakusensis Nagao et Matsumoto, 1940 (Bivalvia) in a Late Cretaceous shallow clastic sea: The Himenoura Group, Kyushu, Japan

The taphonomic features and paleoecology of this species were investigated focused on vertically embedded individuals of articulated Inoceramus amakusensis Nagao et Matsumoto. In the Hinoshima Formation, Himenoura Group of Kyushu, Japan, this Santonian (Late Cretaceous) inoceramid bivalve characteristically occurs in incised-valley fill siliciclastic marine deposits. Modes of I. amakusensis occurrence and preservation, from in situ (= occurrence in life position) to allochthonous shell fragments, are strongly affected by its paleoecology and depositional environments. Several I. amakusensis (up to 25 cm in shell height) were recovered from bioturbated sandstones associated with storm-influenced deposits. Their commissural planes are almost perpendicular to the bedding plane, with the anterior face oriented downward and the posteroventral portion extending upward. Furthermore, I. amakusensis is morphologically comparable to endobyssate mytilid bivalves today. These results suggest that this Cretaceous species was an orthothetic sand sticker at least during mid-ontogeny that preferentially inhabited a well-oxygenated, nearshore seafloor. I. amakusensis was distributed in various depositional environments and has been regarded as a recliner in offshore muddy substrate. However, the present discovery suggests that it was also well adapted, with an upright life position, to high-energy shallow clastic environments characterized by high sediment supply.     

Hypernovae and Gamma-Ray Bursts

The nature of very energetic supernovae (hypernovae) is discussed. They are the explosive death of stars more massive than ~20–25M _⊙, probably linked to the enigmatic Gamma-Ray Bursts. The optical properties of hypernovae indicate that they are significantly aspherical. Synthetic light curves and late-phase spectra of aspherical supernova/hypernova models are presented. These models can account for the optical observations of SNe 1998bw and 2002ap. The abundance patterns of hypernovae are characterized by large ratios (Zn, Co)/Fe and small ratios (Mn, Cr)/Fe, indicating a significant contribution of hypernovae to the early Galactic chemical evolution.