月球Airy均衡状态与月壳厚度估计

月球水准面异常和表面地形变化是其内部密度不均匀和各个界面的起伏变化的体现,因此利用水准面和地形之比(geoid to topography ratio,GTR)可估计月球均衡和月壳厚度。本文基于月球重力场模型SGM100h和地形模型STM359_grid-02,经过去除表面玄武岩填充和深层异常质量影响,并结合理论Airy均衡模型中GTR与参考月壳厚度的关系,计算得到了新的月壳厚度模型。该模型的月壳平均厚度为36.9 km,背面比正面平均厚约13.5 km,Apollo12/14登陆点的月壳厚度分别是28.3 km和29.1 km。在各月海盆地存在着中央较薄、四周逐渐增厚的趋势。     

A Diagnostic and Numerical Study on a Rainstorm in South China Induced by a Northward-Propagating Tropical System

A strong cyclonic wind perturbation generated in the northern South China Sea （SCS） moved northward quickly and developed into a mesoscale vortex in southwest Guangdong Province, and then merged with a southward-moving shear line from mid latitudes in the period of 21-22 May 2006, during which three strong mesoscale convective systems （MCSs） formed and brought about torrential rain or even cloudburst in South China. With the 1° ×1° NCEP （National Centers for Environment Prediction） reanalysis data and the Weather and Research Forecast （WRF） mesoscale model, a numerical simulation, a potential vorticity inversion analysis, and some sensitivity experiments are carried out to reveal the formation mechanism of this rainfall event. In the meantime, conventional observations, satellite images, and the WRF model outputs are also utilized to perform a preliminary dynamic and thermodynamic diagnostic analysis of the rainstorm systems. It is found that the torrential rain occurred in favorable synoptic conditions such as warm and moist environment, low lifting condensation level, and high convective instability. The moisture transport by strong southerly winds associated with the rapid northward advance of the cyclonic wind perturbation over the northern SCS provided the warm and moist condition for the formation of the excessive rain. Under the dynamic steering of a southwesterly flow ahead of a north trough and that on the southwest side of the West Pacific subtropical high, the mesoscale vortex （or the cyclonic wind perturbation）, after its genesis, moved northward and brought about enormous rain in most parts of Guangdong Province through providing certain lifting forcing for the triggering of mesoscale convection. During the development of the mesoscale vortex, heavy rainfall was to a certain extent enhanced by the mesoscale topography of the Yunwu Mountain in Guangdong. The effect of the Yunwu Mountain is found to vary under different prevailing wind directions and intensities. The location o     

江西省一次冷空气过程中的灰霾天气过程分析

利用江西省常规气象观测资料、探空站资料和空气污染资料,对2008年12月12～13日江西省的一次大范围灰霾天气过程进行了综合分析研究。结果表明:横槽转竖引导冷空气南下和中层高度的干燥暖舌共同影响,是这次灰霾天气过程发生的天气形势背景;冷空气受到700hPa干暖舌的抑制作用,形成低层偏冷,中层偏暖的"逆温"结构,导致了大范围的灰霾天气过程出现、维持;空气相对湿度较低,受昼夜温差和冷空气的共同影响,造成轻雾和灰霾天气之间频繁转换;较低的混合层高度导致近地面污染物以水平运动为主,在遇到较高海拔的山脉阻挡后,沿山脉边缘向东西方向扩展,汇集到平原、河谷地区,降低这些地区的能见度,导致灰霾区域由"南北向型"演变成了"东西向型"。     

Simulation of Tsaoling landslide, Taiwan, based on Saint Venant equations over general topography

The 1999 Chi-Chi earthquake triggered the catastrophic Tsaoling landslide in Taiwan. The geomorphological change measured from the data of the 1989 and 2000 aerial photos reveals that the scar and deposit volumes are about 0.126 km³ and 0.15 km³ respectively. The debris material ran over a distance of 1.6 km with 500 m descent in elevation. In this paper, we use the continuum model of hydraulic flow, SHALTOP^2D, based on the equations of Bouchut and Westdickenberg to simulate numerically the landslide dynamics. When the mass is moving, the flow is assumed hydrostatic with a basal Coulomb friction. The best fit is obtained using the basal friction angle equal to 6°, the only parameter of the simulation, uniformly applied in the calculation domain. The landslide front reaches the Chinshui river valley, the foothill of the slope, within only about 25 s after initiation and the motion settles in about 113 s. The maximum speed is estimated 75 m/s. The spreading of the deposit agrees well with the field measurement.     

Reef-island topography and the vulnerability of atolls to sea-level rise

Low-lying reef islands on the rim of atolls are perceived as particularly vulnerable to the impacts of sea-level rise. Three effects are inferred: erosion of the shoreline, inundation of low-lying areas, and saline intrusion into the freshwater lens. Regional reconstruction of sea-level trends, supplementing the short observational instrumental record, indicates that monthly mean sea level is rising in the eastern Indian and western Pacific Oceans. This paper reviews the morphology and substrate characteristics of reef islands on Indo-Pacific atolls, and summarises their topography. On most atolls across this region, there is an oceanward ridge built by waves to a height of around 3 m above MSL; in a few cases these are topped by wind-blown dunes. The prominence of these ridges, together with radiocarbon dating and multi-temporal studies of shoreline position, indicate net accretion rather than long-term erosion on most of these oceanward shores. Less prominent lagoonward ridges occur, but their morphology and continuity are atoll-specific, being a function of the processes operating in each lagoon. Low-lying central areas are a feature of many islands, often locally excavated for production of taro. These lower-lying areas are already subject to inundation, which seems certain to increase as the sea rises. Tropical storms play an important role in the geomorphology of reef islands in those regions where they are experienced. Topographical differences, as well as features such as emergence of the reef flat and the stability of the substrate, mean that islands differ in terms of their susceptibility to sea-level rise. Further assessment of variations in shoreline vulnerability based on topography and substrate could form the basis for enhancing the natural resilience of these islands.     

南海夏季风爆发的数值预报试验

分析了1986年南海夏季风爆发的环流演变特征,由经向风速剖面图看出,南风首先在中南半岛迅速加强,然后向南海发展,南海夏季风爆发同孟加拉湾低压的发展密切相关。通过地形和非绝热单因子敏感性数值预报试验表明,地形作用和凝结潜热等非绝热作用对南海夏季风的爆发都是很重要的,包含有这两种作用在内的控制试验成功地预报出了南海夏季风爆发的中期演变过程,单独的地形作用或非绝热作用都不能预报出南海夏季风的爆发。     

Retrieving spatial variations of land surface temperatures from satellite data–Cairo region,Egypt

Cairo region is characterized by a range of physiographic features, including: flat agricultural lands, bare sandy deserts, highlands, calcareous terrains and urban land use. A time series data-set (300 images) acquired from the Moderate Resolution Imaging Spectroradiometer for the period July 2002–June 2015 were utilized to retrieve the spatial variations in the mean land surface temperature (LST) for the above-mentioned surface features. Results showed that vegetation, topography and surface albedo have negative correlations with LST. Vegetation/LST correlation has the maximum regression coefficient (R² = 0.68) and albedo/LST has the minimum (R² = 0.03). Cultivated lands reveal the lowest mean LST (<32 °C), whereas industrial lands exhibit the highest LST (>40 °C) of Cairo region. There is a considerable urban heat island formed at Helwan south of Cairo, where heavy industries are settled. Industrial activities raised the mean LST of the region by at least 4 °C than the surrounding urban lands.     

Spatial Distribution of Shelf- and Slope-Dwelling Fishes Collected by Bottom Longline off Lanzarote and Fuerteventura, Canary Islands

Abstract. A total of 1789 fish belonging to 38 families and 73 species were collected at depths between 18 and 1102 m during 216 bottom longline operations off Lanzarote and Fuerteventura, Canary Islands, between February 1994 and December 1995. For each species the depth distribution is provided. Length-weight and depth-size relationships are reported for three shelf-dwelling species. The bigger-deeper relationship found in two of them contrasts with the bigger-shallower pattern of the deeper living trichiurid Lepidopus caudatus . In November 1997, nine additional bottom longline operations were carried out off eastern Fuerteventura at depths between 805 and 1217 m. In this area, after earlier studies in October 1995, a spawning aggregation of the morid Mora moro was encountered for the second time. The catches of 1997 revealed a strongly male-biased sex ratio. Also, the males showed a significantly lower gonadosomal index than two years earlier. These findings indicate slight interannual variations in reproductive timing and an earlier arrival of male Mora moro at the spawning grounds. Clear variations in the number of fish collected at adjacent sites possibly reflect a preference for distinct microhabitats. Preliminary evidence of local upwelling of cold water above the spawning grounds is provided by satellite imagery.     

Numerical studies of upwelling in coastalareas of the East China Sea——Ⅰ The tide-induced upwelling

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DGPS在航道的水下地形与水深测量中的应用示例

ＧＰＳ动态实时差分定位模式具有精度高,性能可靠,使用方便等优点,它在许多领域都展示了广阔的应用前景,本文将以ＤＧＰＳ在航道的水下地形与不深测量方面的具体应用为例予以简单介绍,代与同行交流。