基于ConvLSTM的广西短临降水预报

针对传统雷达回波外推算法在快速增长或消散降水过程预报精度较低的问题,利用华南雷达回波拼图资料数据,建立ConvLSTM回波外推模型,对广西区域范围进行短临降水预报研究.采用气象业务中的正确率(POD)、临界成功指数(CSI)及误报率(FAR)评判标准检验预报模型,并将ConvLSTM与光流法的预报结果进行对比分析.结果...     

(137)Cs baseline levels in the Mediterranean and Black Sea: a cross-basin survey of the CIESM Mediterranean Mussel Watch programme

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify (137)Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured (137)Cs levels were found to be very low (usually < 1 Bq kg(-1) wet wt) (137)Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.     

太湖草/藻型湖区沉积物-水界面环境特征差异

在太湖草、藻型湖区进行冬、夏两季多点采样,分别对采样点的水环境特征、泥面以上5 cm上覆水中营养盐以及沉积物的含水量、中值粒径、有机碳、氮、磷、金属元素和溶解氧进行测定.结果表明:夏季藻型湖区表层水体pH高于中、底层,冬季草型湖区各层水体pH高于藻型;草型湖区水体浊度夏季低于藻型,冬季反之;藻型湖区上覆水中的硝态氮和磷酸根浓度显著高于草型;草型湖区沉积物中含水量冬季显著高于夏季;草型湖区沉积物中总有机碳显著高于藻型;Fe、Zn、Ca、Pb、Na和K等元素在草、藻型湖区间差异显著;沉积物中溶解氧表现为冬季深于夏季,藻型深于草型的规律.     

Short‐term flood inundation prediction using hydrologic‐hydraulic models forced with downscaled rainfall from global NWP

A short‐term flood inundation prediction model has been formulated based on the combination of the super‐tank model, forced with downscaled rainfall from a global numerical weather prediction model, and a one‐dimensional (1D) hydraulic model. Different statistical methods for downscaled rainfall have been explored, taking into account the availability of historical data. It has been found that the full implementation of a statistical downscaling model considering physically‐based corrections to the numerical weather prediction model output for rainfall prediction performs better compared with an altitudinal correction method. The integration of the super‐tank model into the 1D hydraulic model demonstrates a minimal requirement for the calibration of rainfall–runoff and flood propagation models. Updating the model with antecedent rainfall and regular forecast renewal has enhanced the model's capabilities as a result of the data assimilation processes of the runoff and numerical weather prediction models. The results show that the predicted water levels demonstrate acceptable agreement with those measured by stream gauges and comparable to those reproduced using the actual rainfall. Moreover, the predicted flood inundation depth and extent exhibit reasonably similar tendencies to those observed in the field. However, large uncertainties are observed in the prediction results in lower, flat portions of the river basin where the hydraulic conditions are not properly analysed by the 1D flood propagation model. Copyright © 2013 John Wiley & Sons, Ltd.     

Estimation on dynamic release of phosphorus from wind-induced suspended particulate matter in Lake Taihu

The internal source, especially resuspension process of the sediments in lakes and its environ- mental effect has been paid shining attention in the West as well as in China[1—6] although the influence of external source is important to water environment[7]. S鴑dergaard et al. compared the releases of soluble reactive phosphorus (SRP) in the surface sediments of Lake Arres before and after disturbance and they found that disturbing can increase the release by 20—30 times[3]. Robarts and ot…     

西藏纳木错末次间冰期以来的气候变迁与湖面变化

在西藏纳木错沿岸,发育了6级湖岸阶地及拔湖48～139.2m的高位湖相沉积.根据湖相沉积的U系法测年和孢粉分析结果,本文探讨了纳木错及邻区末次间冰期(MIS5)以来的古植被、古气候与湖面变化.研究表明,纳木错与邻区的湖面变化可以划分为116～37kaB.P.间的古大湖--"羌塘东湖"期、37～30kaB.P.间的"古纳木错"外流湖-残余古大湖期和30kaB.P.以来的纳木错-藏北湖群期等3大阶段.在MIS5的古大湖阶段,包括纳木错、色林错等藏北高原东南部的众多大、中型湖泊,是互相连通的一个大湖,其范围可能超过了现代的藏北内、外流(怒江)水系的分水岭.在MIS5e末的最高湖面时期,湖面面积可达78800km2,它或许还与藏北高原西南部和中南部的其他古大湖相连,成为面积巨大的网格状深水大湖--"羌塘湖".通过纳木错湖面变化曲线与西昆仑古里雅、格陵兰、南极等冰芯和深海岩芯的氧同位素变化曲线的对比可以发现,全球MIS5的气温要高于末次冰期间冰阶(MIS3),此时藏北高原为气候温和轻爽与湖面最高的大湖期;在末次冰期的两个冰阶(MIS4和MIS2)中,湖面明显下降,邻近的念青唐古拉山发育了小型山谷冰川;而在间冰阶MIS3中,其气候波动的幅度,要比世界其他地区更加明显,湖面波动也较大,特别是36～35kaB.P.间,气温和湿度都较今略高或较高,但不及MIS1中的全新世气候最宜时期的暖湿程度.总之,MIS5和MIS3是亚洲夏季风强烈时期,但前者的强烈程度应大于后者.     

太湖梅梁湾富营养化主要驱动因子的多时间尺度分析

采用太湖湖泊生态系统研究站太湖梅梁湾富营养化四种主要驱动因子叶绿素a(Chl.a)、水温、总磷(TP)、总氮浓度1992-2010年的监测数据,利用小波变换方法,分析了四种因子不同时间尺度上的时间格局特征.结果表明,四种驱动因子在年际和年代际尺度上都具有清晰的多时间尺度特征,主周期各不相同,但Chl.a和TP浓度的小波实部变化趋势具有较高的一致性.本文分析了各因子在不同时间尺度上的强弱分布以及高低交替,并在此基础上从时间尺度的角度预测出在未来3~5年内,太湖梅梁湾湖区的富营养化程度将保持在一个比较平稳的水平,为太湖富营养化的认识和治理提供更加可靠的科学依据.     

太湖藻类生长模型研究

本文提出了一改进的藻类生长模型及其新颖的计算机模拟算法,该模型不但考虑了不温、总氮、总氮、总磷、浮游动物的辐射等因素对藻类生长率的影响,而且根据水量,总磷和藻类浓度等因素对藻类死亡率进行了修正和计算精度至关重要的,因此,本文建立了具有绝对稳定性和二阶精度的数值算法求解藻类生长模型中的偏微分方程组,此外,为了进一步验证该藻类生长模型的实测值进行模拟,由于实测值为每个月中某一天的测量值,为了模拟过程能正确进行,本文采用样条插值的方法估计出每用插值等方法,本文提出了一种广义拟结果与测量数据基本符合,而在有明显的差异的地方,文中作出了相应的解释,结果表明,本文提出了藻类生长模型及其算法是有效的,各采样点藻类浓度的模拟值能较好地拟合实测值。     

Nutrient fluxes induced by disturbance in Meiliang Bay of Lake Taihu

A wave flume experiment was conducted to study nutrient fluxes at water-sediment interface of Meiliang Bay under different hydrodynamic conditions. The results reveal that hydrodynamics has remarkable effects on nutrient fluxes in this area. With a bottom wave stress of 0.019 N m^?2 (equivalent to disturbance caused by wind SE 5–7 m s^?1 at the sediment sample site of Meiliang Bay), the fluxes of TN, TDN and NH₄ ⁺-N were separately 1.92 × 10^?3, ?1.81 × 10^?4 and 5.28 × 10^?4 mg m^?2 s^?1 (positive for upward and negative for downward), but for TP, TDP and SRP, the fluxes were 5.69 × 10^?4, 1.68 × 10^?4 and ?1.29 × 10^?4 mg m^?2 s^?1. In order to calculate the released amount of nutrients based on these results, statistic analysis on the long-term meteorological data was conducted. The result shows that the maximum lasting time for wind SE 5–7 m s^?1 in this area is about 15 h in summer. Further calculation shows that 111 t TN, 32 t NH₄ ⁺-N, 34 t TP and 10 t TDP can be released into water (the sediment area was 47.45% of the whole surface area), resulting in concentration increase of 0.025, 0.007, 0.007 and 0.002 mg L^?1 separately. With stronger disturbance (bottom wave stress is 0.217 N m^?2 which is equivalent to disturbance caused by wind SE 10–11 m s^?1 at the same site), there has been significant increase of nutrient fluxes (1.16 × 10^?2, 6.76 × 10^?3, 1.14 × 10^?2 and 2.14 × 10^?3 mg m^?2 s^?1 for TN, DTN and NH₄ ⁺-N and TP). The exceptions were TDP with flux having a decrease (measured to be 9.54 × 10^?5 mg m^?2 s^?1) and SRP with flux having a small increase (measured to be 5.42 × 10^?5 mg m^?2 s^?1). The same statistic analysis on meteorological data reveal that the maximum lasting time for wind SE 10–11 m s^?1 is no more than 5 h. Based on the nutrient fluxes and the wind lasting-time, similar calculations were also made suggesting that 232 t TN, 134.9 t TDN, 228 t NH₄ ⁺-N, 42.7 t TP, 2.0 t TDP and 1.1 t SRP will be released from sediment at this hydrodynamic condition resulting in the concentration increases of 0.050, 0.029, 0.049, 0.009, 0.0004 and 0.0002 mg L^?1. Therefore in shallow lakes, surface disturbance can lead to significant increase of nutrient concentrations although some components in water column had negative flux with weak disturbance (e.g. TDN and SRP in this experiment). In this case, sediment looks to be a source of nutrients. These nutrients deposited in sediment can be carried or released into water with sediment resuspension or changes of environmental conditions at water-sediment interface, which can have great effects on aquatic ecosystem and is also the characteristics of shallow lakes.