Prediction of fish yield and potential productivity from limnological data in Lake Borollus, Egypt

Four limnological models (lake shoreline development (D_L), Morphoedaphic Index (MEI), primary production and total nutrient input) have been applied to Lake Borollus to estimate existing fish yield and future potential productivity. The estimated existing fish yield from the lake is about 1260 kg/ha (i.e. 53,000 tons/annum), which is at or near its existing potential and is considered in the ultra enriched category. From 1931 to 1935, the estimated fish production of Lake Borollus was about 68 kg/ha, which is considered low enriched category, while from1960 to 1970, the lake belonged to the moderately enriched category, where the estimated fish production was about 155 kg/ha, and then tremendously increased to about 580 kg/ha during the 1980's.Thisincrease in fish yield is mainly attributed to the nutrient loading of the southern and eastern drains to the lake. In the long term, and based on existing nutrient input to fish yield relationships, it is estimated that increased nutrient loading from drainage water may elevate its yield by 24, 580 tons by the year 2005 (i.e. total fish yield could be increased to 77,500 tons/annum). This revised version was published online in July 2006 with corrections to the Cover Date.     

用NOAA卫星可见光和红外资料估算甘肃省东部农田区土壤湿度

应用NOAA卫星AVHRR通道1、2计算的植被指数和通道4的亮温、农业气象试验站观测的土壤湿度，并结合气象卫星完成的土地覆盖分类等资料，建立了由植被指数和亮温估算甘肃省东部农田区土壤湿度的方程。结果表明，农田土壤湿度与植被指数和亮温间均存在一定相关关系；用植被指数和亮温可以估计土壤湿度情况，并对干旱进行监测。     

Bred-ensemble ocean forecast of loop current and rings

Ocean forecasting with a General Circulation Model (GCM) commonly begins from an initial analysis obtained by data assimilation. Instead of a single initial state, bred-ensemble forecast [BEnF; which is used for weather forecasting at the National Centers for Environmental Prediction] begins from an ensemble of initial states obtained by using the GCM to breed fast-growing modes into the analysis. Here we apply the technique to forecast the locations and strengths of the Loop Current and rings from July through September 2005. Model results are compared against satellite observations, surface drifter trajectories, and moored currents. It is found that BEnF gives closer agreements with observations than the conventional single forecast. The bred-vectors (perturbed minus unperturbed state-vectors) have growth rates ≈0.04–0.08 day⁻¹ and spatial (cyclone–anticyclone) scales ≈200–300 km suggestive of baroclinic instability mode in the Loop Current and rings. As in atmospheric applications, initializations with these growing vectors contribute to the more accurate ensemble mean forecast.     

Airborne Laser Sensing of Scottish Coastal Waters

An Nd:YAG-based airborne lidar system has been used to measure the optical properties of littoral waters off the northwest Scottish coast. The small-scale structure of subsurface scattering layers was also investigated. Methods of solving the Lidar Sensing Equation in the single scattering approximation are described and the values of the derived extinction indices presented. The extinction index averaged over a series of five flights to the northeast of the Gulf Stream was ε= 0.224 m -1 with a standard deviation of 0.212 m -1 . Further, it was demonstrated that, in coastal waters, optical inhomogeneities with dimensions between 50 m and 200 km obey the power law Sp ε ~ k -P with the parameter P close to two. In turbid or transparent areas, the water extinction index can change by several tenths of a percent with respect to the surrounding water mass. This suggests that the observed nonmonotonic behavior of the power spectra of the water extinction index fluctuations is caused by the outer scale of turbulence, in particular, by the bottom depth at the measurement site.     

黄、渤海表层沉积物中钙质超微化石分布规律与黄海暖流流路

黄、渤海表层沉积物中钙质超微化石有较广泛分布,属种较大洋和开阔海少而单调。黄海南部见有14个种,北黄海及渤海海峡4～5个种,渤海沿岸区2～3个种。钙质超微化石分异度D_H以及主要化石种相对百分含量的高值区的主轴线的走向与现代黄海暖流的流路密切相关。得出黄海暖流由南黄海东南部流入北黄海,通过渤海海峡的北侧进入渤海,在渤海中部呈南北向伸展。     

Annual precipitation in the Yellowstone National Park region since AD 1173

Cores and cross sections from 133 limber pine (Pinus flexilis James) and Douglas fir (Pseudotsuga menziesii (Mirbel) Franco) at four sites were used to estimate annual (July to June) precipitation in the Yellowstone National Park region for the period from AD 1173 to 1998. Examination of the long-term record shows that the early 20th century was markedly wet compared to the previous 700 yr. Extreme wet and dry years within the instrumental period fall within the range of past variability, and the magnitude of the worst-case droughts of the 20th century (AD 1930s and 1950s) was likely equaled or exceeded on numerous occasions before AD 1900. Spectral analysis showed significant decadal to multidecadal precipitation variability. At times this lower frequency variability produces strong regime-like behavior in regional precipitation, with the potential for rapid, high-amplitude switching between predominately wet and predominately dry conditions. Over multiple time scales, strong Yellowstone region precipitation anomalies were almost always associated with spatially extensive events spanning various combinations of the central and southern U.S. Rockies, the northern U.S.-Southern Canadian Rockies and the Pacific Northwest.     

云南汛期旱涝特征及成因分析

通过Z指数和旋转经验正交函数(REOF)分析等对云南省汛期(5~10月)降水作旱涝等级划分、型态分布和旱涝时空分布特征研究,发现云南省各地汛期降水具有一致性,1980年代以来,汛期旱涝有更频繁发生的趋势,东、西部和东南部地区为云南省全省旱涝多发区。对比分析了云南旱涝年的大气环流特征,发现两者显著差异:涝年500 hPa位势高度距平亚洲区域自西向东为“- -”波列结构,云南北部低槽活跃,反映出有强冷空气活动的环流背景,伊朗高压及青藏高压活跃,利于与副热带高压形成“两高辐合”的强降水形势;低层850 hPa水汽输送和OLR场特征揭示出低纬度热带海洋具有强烈的水汽输送机制;旱年则反之。并讨论了导致云南汛期旱涝的热带强迫源区主要位于孟加拉湾、南海—西太平洋,可能机制是热带强迫所激发的大尺度准定常波列的传播。     

KV法在判定岩体完整性中的应用

使用某花岗岩体内16个钻孔的资料,用KV法分别对该岩体的强、中等、微风化层的完整性作出判断,并与钻孔揭示的实际情况进行比对,结果证明:在具备大量、较准确的波速测试数据的前提下,用KV法判断岩石的完整性所得出的结论和实际情况几乎完全一致。     

玉林市近50年来干旱的发生规律及防御对策

根据玉林市春、夏、秋三个季节干旱对农业生产的影响，参照历年的旱情资料，确定出干旱的农业气象指标，分析47a来干旱的时空分布规律和特点，并针对玉林市的具体情况提出一些防御干旱的对策。     

高CO2条件下贝加尔针毛对土壤干旱胁迫响应的试验研究

贝加尔针毛 (Stipa baicalensis) 是我国内蒙古东部和东北西部主要的地带性植被之一。通过人工模拟试验分析了CO₂浓度升高对贝加尔针毛的“施肥”效应, 结果表明:贝加尔针毛的生物量、生长量随CO₂浓度的升高而增加, 根中P的含量、叶中C、N、P的含量也随CO₂浓度的升高而增加。土壤干旱胁迫对贝加尔针毛的生物量、生长量的影响均为负效应, 且干旱程度的加重使影响更明显。干旱使针毛叶、根中的C、N含量增加。