Possible effect of ENSO on annual sediment discharge of debris flows in the Jiangjia Ravine based on Morlet wavelet transforms

The multi-time-scale structures of an annual sediment discharge series of debris flow in the Jiangjia Ravine and the Southern Oscillation index are analysed using the method of Morlet wavelet transformations. The possible effects of E1 Nirio episodes on the annual sediment discharge are discussed by comparing the period variations of ENSO and the discharge. The results show that the annual sediment discharge series of debris flow is related to E1 Nifio episodes. Generally, the annual sediment discharge of debris flow is less than usual during an E1 Nifio episode and debris flow is less active. On the contrary, the annual sediment discharge of debris flows is greater than usual during a La Nifia episode and debris flows are more frequent. There is a relationship between the annual sediment discharges of debris flow in the Jiangjia Ravine and the summer Southern Oscillation index, with both having quasi-periodic variations of 2 and 5-6 years.     

基于地貌分区的1990-2015年中国耕地时空特征变化分析

地形地貌通过分配地表水分和热量制约耕地的利用形式和成效,对耕地质量具有非常重要的决定意义,以地貌分区的视角研究中国耕地变化具有重要意义。根据1990-2015年中国6期土地利用空间数据和地貌分区数据,运用GIS空间叠加分析方法,分析中国耕地1990-2015年的面积变化和空间分布格局,进一步探讨不同地貌分区下的耕地新增与流失方向。结果表明,中国耕地面积略有增加,但总体变化不大,耕地面积从1990年的17715万hm²增加到2015年的17851万hm²,平均每年增加5.44万hm²,每年增幅仅为0.03%。耕地主要分布在平原地区,台地、丘陵次之;新增耕地主要来源为草地、林地和未利用地。东部平原低山丘陵区（I）耕地面积最大,而西北高中山盆地高原区（IV）耕地动态度明显高于其他地貌区。空间上呈现“南减北增,新增耕地的重心向西北移动”的特征。1990-2015年间,西北高中山盆地高原区（IV）和东部平原低山丘陵区（I）为耕地面积增长区,平均每年增加耕地面积分别为8.9万hm²和5.4万hm²;东南低山丘陵平原区（II）和西南中低山高原盆地区（V）为耕地面积减少区,平均每年减少耕地面积分别为5.9万hm²和2.8万hm²;而华北—内蒙东中山高原区（III）和青藏高原高山极高山盆地谷地区（VI）耕地面积几乎没有变化,平均每年变化仅为0.15 万hm²和0.06万 hm²。耕地流失主要发生在东部平原低山丘陵区（I）和东南低山丘陵平原区（II）,主要原因为城镇化进程加快带来的建设用地对优质耕地的大量占用;而新增耕地主要发生在西北高中山盆地高原区（IV）,多来自于对草地和未利用地的开垦。     

Fault zone hydrogeology in arid environments: The origin of cold springs in the Wadi Araba Basin,Egypt

The role of faults in controlling groundwater flow in the Sahara and most of the hyper-arid deserts is poorly understood due to scarcity of hydrological data. The Wadi Araba Basin (WAB), in the Eastern Sahara, is highly affected by folds and faults associated with Senonian tectonics and Paleogene rifting. Using the WAB as a test site, satellite imagery, aeromagnetic maps, field observations, isotopic and geochemical data were examined to unravel the structural control on groundwater flow dynamics in the Sahara. Analysis of satellite imagery indicated that springs occur along structurally controlled scarps. Isotopic data suggested that cold springs in the WAB showed a striking similarity with the Sinai Nubian aquifer system (NAS) water and the thermal springs along the Gulf of Suez (e.g., δ¹⁸O = −8.01‰ to −5.24‰ and δD = −53.09‰ to −31.12‰) demonstrating similar recharge sources. The findings advocated that cold springs in the WAB represent a natural discharge from a previously undefined aquifer in the Eastern Desert of Egypt rather than infiltrated precipitation over the plateaus surrounding the WAB or through hydrologic windows from deep crystalline basement flow. A complex role of the geological structures was inferred including: (1) channelling of the groundwater flow along low-angle faults, (2) compartmentalization of the groundwater flow upslope from high-angle faults, and (3) reduction of the depth to the main aquifer in a breached anticline setting, which resulted in cold spring discharge temperatures (13–22°C). Our findings emphasize on the complex role of faults and folds in controlling groundwater flow, which should be taken into consideration in future examination of aquifer response to climate variability in the Sahara and similar deserts worldwide.     

Physically based maximum precipitation estimation under future climate change conditions

Estimation of the extreme precipitation over a target watershed under a changing climate would be necessary to design safe large hydraulic structures. For this purpose, the maximum precipitation (MP) estimation approach was applied to the American River Watershed (ARW) in Northern California under several future climate conditions over 90 water years (2010–2099). These future climate conditions were obtained using 13 future climate projections from two general circulation models (ECHAM5 and CCSM3) based on four future climate scenarios (Special Report on Emissions Scenarios: A1B, A1FI, A2, and B1). A total of 1,170 future projected severe storm events (90 years × 13 projections) were selected with respect to the 72‐hr basin‐average precipitation over the ARW. The 72‐hr basin‐average precipitation for each of the selected severe storm events was maximized over the ARW by horizontally shifting the atmospheric boundary conditions of a regional atmospheric model in order to optimize the path of the storm system that corresponded to the particular event. After maximization, the MP estimates, which are the largest precipitation depths among the maximized results, were obtained as 836.7 mm for the early half‐century period (2010–2054) and 1,056.5 mm for the late half‐century period (2055–2099).     

Turbulence structure of a tropical forest

A detailed analysis is presented of the horizontal wind fluctuations with periods 20 s to 1 hr, and their vertical structure as measured with light three-cup anemometers in a tropical forest environment. Information collected during the TREND (Tropical Environmental Data) experiment in a monsoon dominated region, was utilized. A special attempt was made to extract information relevant for dispersion modeling. Variability parameters within and above the forest canopy under different stability conditions were derived. A similar analysis was performed for a nearby clearing, to facilitate comparison between relatively smooth and rough surfaces, under identical ambient conditions. A limited sample of data (7 days) was utilized, initially, to develop a methodology to be later applied on a comprehensive data base, spanning the whole monsoon cycle.     

On the two classes of filament-prominence disappearance and their relation to coronal mass ejections

We analyze the phenomenon of sudden disappearance (DB) of quiescent filaments and prominences, with examples of the two classes (dynamic and thermal DB) observed on the solar disk and at the limb. The differences between their dynamics are discussed, and it is shown that only dynamic DBs are associated with coronal mass ejections (CME), whereas thermal DBs are only local disturbances of the lower corona. We finish with a discussion of DBs detected on the disk and limb, to explain the statistical differences between the disappearance of filaments and the production of CME.     

Propagation of pressure shocks in radiating fluids with variable transport coefficients

The propagation of pressure shocks in a viscous, heat-conducting, and radiating magnetofluid of finite electric conductivity is studied. The equilibrium diffusion approximation of the radiation field is applied. After determining the velocity of the wave front, a differential equation governing the shock strength during propagation is derived. The effects of radiation pressure, radiation flux, and variation of the transport coefficients on the propagation are examined.     

Symplectic methods and their application to the motion of small bodies in the Solar System

Symplectic methods have been widely used in Solar System dynamics. This paper discusses both single step and multistep symplectic methods. For single step methods we point out that the modified algorithm (Wisdom et al., 1991, Kinoshita et. al., 1991) can be executed in the mass center coordinate system and in the Jacobian coordinate system. For multistep methods we describe the connections between symmetric and symplectic methods.