Seasonal Trend in the Occurrence of Nocturnal Drainage Flow on a Forested Slope Under a Tropical Monsoon Climate

Using data for one year, we examined the vertical wind speed profileson a mountain slope covered with forest in northern Thailand undera tropical monsoon climate. We defined two profile patterns: higherwind speeds at greater heights (Pattern 1) and lower wind speeds atgreater heights (Pattern 2). We classified 9.4% of the data as Pattern 2;this pattern tended to occur during the night, at low wind speeds, and with high outgoing longwave radiation. In addition, stable stratification anddecoupling between the canopy surface air and the overlying layers wereobserved when Pattern 2 occurred frequently. These facts suggested thatPattern 2 was caused by a nocturnal drainage flow. The occurrence ofPattern 2 showed a clear seasonal trend, indicating that there is a seasonaltrend in the occurrence of nocturnal drainage flows. Pattern 2 was observedmore frequently between August and February and less frequently betweenMarch and July. This corresponded to the seasonal trend in wind speed, butdid not correspond to the seasonal trend in the outgoing longwave radiation.     

A Raman spectroscopic study of shock-wave densification of anorthite (CaAl2Si2O8) glass

Structural modifications induced by shock-wave compression up to 40 GPa in anorthite glass are investigated by Raman spectroscopy. In the first investigation, densification increases with increasing shock pressure. A maximum densification of 2.2% is obtained for a shock pressure of 24 GPa. This densification is attributed to a decrease of the average ring size, favoring three-membered rings. The densification is much lower than in silica glass subject to shock at similar pressures (11%), because the T-O-T bond angle decrease is impeded in anorthite glass. For higher shock pressures, the decrease of the recovered densification is attributed to partial annealing of the samples due to high after-shock residual temperatures. The study of the annealing process of the most densified glass by in-situ high temperature Raman spectroscopy confirms that relaxation of the three-membered rings occurs above about 900 K. Received: 21 July 1998 / Revised and accepted: 27 January 1999     

Horizontal distribution of calanoid copepods in the western Arctic Ocean during the summer of 2008

The horizontal distribution of the epipelagic zooplankton communities in the western Arctic Ocean was studied during August–October 2008. Zooplankton abundance and biomass were higher in the Chukchi Sea, and ranged from 3,000 to 274,000 ind. m^?2 and 5–678 g WM m^?2, respectively. Copepods were the most dominant taxa and comprised 37?94% of zooplankton abundance. For calanoid copepods, 30 species belonging to 20 genera were identified. Based on the copepod abundance, their communities were classified into three groups using a cluster analysis. The horizontal distribution of each group was well synchronized with depth zones, defined here as Shelf, Slope and Basin. Neritic Pacific copepods were the dominant species in the Shelf zone. Arctic copepods were substantially greater in the Slope zone than the other regions. Mesopelagic copepods were greater in the Basin zone than the other regions. Stage compositions of large-sized Arctic copepods (Calanus glacialis and Metridia longa) were characterized by the dominance of late copepodid stages in the Basin. Both the abundance and stage compositions of large copepods corresponded well with Chl. a concentrations in each region, with high Chl. a in the Shelf and Slope supporting reproduction of copepods resulting in high abundance dominated by early copepodid stages.     

实验变形岩石低温破裂作用的微观机制

通过对湿度和压力分别达300℃和3GPa干条件下实验变形的一系列花岗岩样品的系统光学和扫描电镜显微构造分析,识别出了几种具有不同特点及不同变形机制的显微破裂型式:a.微破碎带;b.微透镜带;c.短程破裂;d.扭折带破裂;e.粒内破裂;f.颗粒边界破裂。评价了它们与高压型和低压型破裂的显微构造对应性,认为a和f是低压破裂的特征性构造型式;b、c和d在高压破裂中最为典型;而e则可以出现在两种破裂型式中。本文阐述了破裂作用的微观机制,包括破裂的成核、扩展、生长和连接。破裂作用、由破裂诱发的脆性破裂和碎裂流动在目前实验变形条件下占主导地位,而在相对较高温条件下晶质塑性也起着一定的作用。破裂作用的成核可以始于颗粒边界,而引起摩擦颗粒边界滑移,也可以始于相邻颗粒或晶内包体颗粒的一些端点,或始于晶内双晶和解理面。破裂的生长和扩展一般是由于一些破裂的侧向延伸、相近破裂系统的联合和不同破裂系统的转变。低压样品的最终破裂一般归咎于一些贯穿性微断层的出现及主断层附近微破裂群的产生,微破碎角砾岩是其主要构造岩类型,类似于天然张性断层带构造;而沿主高压破裂附近却从未见到这种微破裂群的出现,主要表现为主破裂面及一些均匀分布的短程破裂构造, 典型构造岩为构造透镜体, 类似于天然压性与压扭性断层构造。两种破裂在成核、扩展与位移发育诸方面表现出的差别有助理解它们在声发射方面的差异。