Climatology of yellow sand (Asian sand,Asian dust or Kosa) in East Asia

In order to study climatology of yellow sand (Asian sand, Asian dust or Kosa) in East Asia, secular fluctuation in China, Korea and Japan in the recent 30 years was presented. The number of days with sand-dust storm at five stations in China—Hotan, Zhangye, Minqin, Jurh and Beijing, decreases a lot at the former three stations, but changed little at the latter two stations. Suggesting that the recent global warming is more evident in Xinjiang and Gansu, where the frequency of cold air invasions from the higher latitudes is decreasing. But, the eastern parts of Mongolia, inner Mongolia, and North China encounter stronger cyclones in early spring as a result of global warming. These cyclones bring cold air from higher latitudes, causing severe dust storms. Secular variation in the annual days with sand-dust storms in China and Kosa days in Korea and Japan show a parallel change with higher frequency from 1975 to 1985. This may be related to the higher frequency of La Nina years. However, different tendency was shown in the period from 1986 to 1996. Since 1996 or 1997, a sharp increase is clear, which may be caused by the developed cyclones in East Asia as well as human activities, and stronger land degradation under La Nina conditions. Anomalies of the total number of stations with Kosa days were discussed in accordance with some synoptic meteorological conditions such as the differences between Siberian anticyclone and Aleutian cyclone center at 500 hPa level during the previous winter.

     

Improved absorption cross-sections of oxygen in the wavelength region 205–240 nm of the Herzberg continuum

The laboratory values of the Herzberg continuum absorption cross-section of oxygen at room temperature from Cheung et al. (1986, Planet. Space Sci. 34, 1007), Jenouvrier et al. (1986a, Planet. Space Sci. 34, 253) and Jenouvrier et al. (1986, J. quant. Spectrosc. radiat. Transfer 36, 349) have been compared and re-analyzed. There is no discrepancy between the absolute values of these two sets of independent measurements. These values have been combined together in a linear least-squares fit to obtain improved values of the Herzberg continuum cross-section of oxygen at room temperature throughout the wavelength region 205–240 nm. Agreement with in situ and other laboratory measurements is discussed.     

High resolution absorption cross-section measurements of N2O at 295–299 K in the wavelength region 170–222 nm

High resolution absorption cross-section measurements of N₂O at 295–299 K have been performed in the wavelength region 170–222 nm with a 6.65 m scanning spectrometer/spectrograph of sufficient resolution to yield cross-sections that are independent of the instrumental function. The measured cross-sections are presented graphically and are available throughout the region 44925–58955 cm^?1 at intervals of 0.1–0.2 cm^?1 as a numerical tabulation stored on magnetic tape from the National Space Science Data Center, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. Previously unresolved details of the banded structure which is superposed on the continuous absorption in the region 174–190 nm are observed.     

High resolution absorption cross section measurements and band oscillator strengths of the (1, 0)−(12, 0) Schumann-Runge bands of O2

Cross sections of O₂ at 300 K have been obtained from photoabsorption measurements at various pressures throughout the wavelength region 179.3–201.5 nm with a 6.65 m photoelectric scanning spectrometer equipped with a 2400 lines mm^?1 grating and having an instrumental width (FWHM) of 0.0013 nm. The measured absorption cross sections of the Schumann-Runge bands (12, 0) through (1, 0) in this wavelength region are absolute, i.e., independent of the instrumental width, a result not achieved previously. The measured cross sections are presented graphically and are available at wavenumber intervals of > sim; 0.1 cm^?1 as numerical complications stored on magnetic tape from the National Space Science Data Center, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. Band oscillator strengths of the (12, 0) through (1, 0) bands have been determined by direct numerical integration of the measured cross sections.     

Thermal belt and cold air drainage on the mountain slope and cold air lake in the basin at quiet, clear night

This paper reviews results of recent observations on the thermal belt, cold air drainage and cold air lake, which are striking in local climatic phenomena in mountain areas.The height (A) of the warmer part, the thermal belt, of the mountain slopes changes with time from early evening, midnight to early morning and also seasonally and differs according to the velocity of the upper general wind and cloudiness, but is generalized by the height difference (H) between the bottom of the basin and the surrounding mountain ridges. Roughly speaking, A = (0.25–0.30) H.On the mountain slopes, cold air flows down intermittently. The air temperature shows positive correlation to the wind speed of cold air drainage in the source region of cold air drainage. On the other hand, however, there is a negative correlation between the wind speed and air temperature in the drainage region at the lower part of the slope. Above the downslope cold air drainage, there is an anti-down-slope wind. The relatively large drainages are formed at frequencies corresponding to periods of oscillation of 1–2 hours and the smaller ones are of several minutes.In the basin or valley bottom, cold air lakes are formed. They are well defined by a strong inversion in air temperature. In most cases, the stagnant air in the cold air lake flows down slowly in accordance with inclination of the basin or valley floor. Above the cold air lake, we find the neutral or weak inversion layer. In some periods the drained cold air flows into this layer from the side slopes of the mountains. However, the radiation cooling of the basin or valley floor seems to be more effective for the formation of the cold air lake. Above the neutral or weak inversion layer, there is a layer of the general wind caused by the synoptic scale circulation systems. Their effects are controlled by the surrounding topography as well as the basin or the valley itself.In short, the structure of thermal belt, cold air drainage and cold air lake is a good example of the small-scale climatic processes under the influence of the synoptic scale phenomena and the one-order-greater scale topography.     

State of stress within a thin elastic wedge: a model of internal deformation of the continental plate at arc—arc junctions

Summary. Anomalous stress distributions near arc—arc junctions have been found in several parts of the world. As a simple two-dimensional model, a thin elastic wedge is introduced to model the continental side of the arc—arc junction, and the stress distribution within it is calculated to interpret those anomalies. Uniform normal and/or shear stress boundary conditions are given separately to each edge to approximate the effect of the two neighbouring converging plate boundaries; Stress components are obtained by numerical integration. Among the various results, the following features are predominant and seem to be actually taking place at arc—arc junctions.
(1) The anomaly in stress pattern within the wedge is basically due to the difference in stress conditions between the two boundaries.
(2) A large stress concentration takes place when symmetrical shear stresses are applied to the two edges.     

A threshold in soil formation at Earth’s arid-hyperarid transition

The soils of the Atacama Desert in northern Chile have long been known to contain large quantities of unusual salts, yet the processes that form these soils are not yet fully understood. We examined the morphology and geochemistry of soils on post-Miocene fans and stream terraces along a south-to-north (27° to 24° S) rainfall transect that spans the arid to hyperarid transition (21 to ∼2 mm rain y⁻¹). Landform ages are ? 2 My based on cosmogenic radionuclide concentrations in surface boulders, and Ar isotopes in interbedded volcanic ash deposits near the driest site indicate a maximum age of 2.1 My. A chemical mass balance analysis that explicitly accounts for atmospheric additions was used to quantify net changes in mass and volume as a function of rainfall. In the arid (21 mm rain y⁻¹) soil, total mass loss to weathering of silicate alluvium and dust (−1030 kg m⁻²) is offset by net addition of salts (+170 kg m⁻²). The most hyperarid soil has accumulated 830 kg m⁻² of atmospheric salts (including 260 kg sulfate m⁻² and 90 kg chloride m⁻²), resulting in unusually high volumetric expansion (120%) for a soil of this age. The composition of both airborne particles and atmospheric deposition in passive traps indicates that the geochemistry of the driest soil reflects accumulated atmospheric influxes coupled with limited in-soil chemical transformation and loss. Long-term rates of atmospheric solute addition were derived from the ion inventories in the driest soil, divided by the landform age, and compared to measured contemporary rates. With decreasing rainfall, the soil salt inventories increase, and the retained salts are both more soluble and present at shallower depths. All soils generally exhibit vertical variation in their chemistry, suggesting slow and stochastic downward water movement, and greater climate variability over the past 2 My than is reflected in recent (∼100 y) rainfall averages. The geochemistry of these soils shows that the transition from arid to hyperarid rainfall levels marks a fundamental geochemical threshold: in wetter soils, the rate and character of chemical weathering results in net mass loss and associated volumetric collapse after 10⁵ to 10⁶ years, while continuous accumulation of atmospheric solutes in hyperarid soils over similar timescales results in dramatic volumetric expansion. The specific geochemistry of hyperarid soils is a function of atmospheric sources, and is expected to vary accordingly at other hyperarid sites. This work identifies key processes in hyperarid soil formation that are likely to be independent of location, and suggests that analogous processes may occur on Mars.