Hydrodynamic-phytoplankton model for short-term forecasts of phytoplankton in Lake Taihu, China

Phytoplankton biomass is an important factor for short-term forecasts of algal blooms. Our new hydrodynamic-phytoplankton model is primarily intended for simulating the spatial and temporal distribution of phytoplankton in Lake Taihu within a time frame of 1-5 days. The model combines two modules: a simple phytoplankton kinetics module for growth and loss; and a mass-transport module, which defines phytoplankton transport horizontally with a two dimensional hydrodynamic model. To adapt field data for model input and calibration, we introduce two simplifications: (a) exclusion of some processes related to phytoplankton dynamics like nutrient dynamics, sediment resuspension, mineralization and nitrification, and (b) use of monthly measured data of the nutrient state. Chlorophyll-α concentration, representing phytoplankton biomass, is the only state variable in the model. A sensitivity analysis was carried out to identify the most sensitive parameter set in the phytoplankton kinetics module. The model was calibrated with field data collected in 2008 and validated with additional data obtained in 2009. A comparison of simulated and observed chlorophyll-α concentration for 33 grid cells achieved an accuracy of 78.7%. However, mean percent error and mean absolute percent error were 13.4% and 58.2%, respectively, which implies that further improvement is necessary, e.g. by reducing uncertainty of the model input and by an improved parameter calibration.     

Intermodel Diversity of Simulated Long-term Changes in the Austral Winter Southern Annular Mode: Role of the Southern Ocean Dipole

The Southern Annular Mode(SAM)plays an important role in regulating Southern Hemisphere extratropical circulation.State-of-the-art models exhibit intermodel spread in simulating long-term changes in the SAM.Results from Atmospheric Model Intercomparison Project(AMIP)experiments from 28 models archived in CMIP5 show that the intermodel spread in the linear trend in the austral winter(June?July?August)SAM is significant,with an intermodel standard deviation of 0.28(10 yr)?1,larger than the multimodel ensemble mean of 0.18(10 yr)?1.This study explores potential factors underlying the model difference from the aspect of extratropical sea surface temperature(SST).Extratropical SST anomalies related to the SAM exhibit a dipole-like structure between middle and high latitudes,referred to as the Southern Ocean Dipole(SOD).The role of SOD-like SST anomalies in influencing the SAM is found in the AMIP simulations.Model performance in simulating the SAM trend is linked with model skill in reflecting the SOD?SAM relationship.Models with stronger linkage between the SOD and the SAM tend to simulate a stronger SAM trend.The explained variance is about 40%in the AMIP runs.These results suggest improved simulation of the SOD?SAM relationship may help reproduce long-term changes in the SAM.     

金川镍矿含矿岩体的稀土元素及微量元素地球化学特征

通过对采自金川镍矿I矿区露天矿的第二期侵入岩体中。样品的稀土元素、微量元素进行全岩等离子质谱（ICP－MS）测定发现第二期侵入的岩体具有明显的轻稀土元素富集和无明显铕异常的特征，是上地幔低比例平衡部分熔融和分离结晶共同作用的产物。岩体中镍黄铁矿、磁黄铁矿、黄铁矿成条带状出现，表明其形成时低氧逸度的成岩环境。     

^40Ar／^39Ar测年中的冷却年龄和变形年龄

^40Ar／^39Ar法年龄数据的解释与Ar同位素在矿物中的封闭温度有关。冷却年龄只能限制变质——变形事件发生的时间区间,不能真正代表地质事件的发生时间。因此,必须想办法得到变形年龄。本文从封闭温度概念出发,探讨了压力、冷却速率、有效扩散范围和几何形态、颗粒大小、动力学参数等对矿物封闭温度的影响,介绍了新近提出的“封闭窗”概念,并讨论了在什么情况下可以获得变形年龄。     

Roles of Wind Stress and Subsurface Cold Water in the Second-Year Cooling of the 2017/18 La Ni?a Event

After the strong 2015/16 El Ni?o event, cold conditions prevailed in the tropical Pacific with the second-year cooling of the 2017/18 La Ni?a event. Many coupled models failed to predict the cold SST anomalies(SSTAs) in 2017. By using the ERA5 and GODAS(Global Ocean Data Assimilation System) products, atmospheric and oceanic factors were examined that could have been responsible for the second-year cooling, including surface wind and the subsurface thermal state. A time sequence is described to ...     

基于GIS的叶城县核桃种植气候适宜性精细化区划

本文以叶城县特色林果—核桃为研究对象，研究叶城核桃种植的气候适宜性，以期充分利用农业气候资源，科学规划叶城县核桃种植布局和发展区域提供气候依据。利用叶城县及其周边20个气象站1981-2019年近39年的气温观测数据和同期核桃生长发育的物候资料，在分析核桃生长发育关键期与光、热、水气候条件关系的基础上，提出影响核桃生长发育的关键气候因子≥10℃积温、冬季最低气温≤-25℃日数、终霜冻日早于≥10℃初日天数作为核桃气候适宜性区划指标，基于GIS空间插值技术对叶城县核桃种植各区划指标因子进行空间特征分析，采用GIS空间加权分析法对核桃种植气候指标进行精细化分区，结果表明：叶城县影响核桃的各指标因子空间分布受海拔高度影响，≥10℃积温总体呈现“北疆多、南疆少、平原和盆地多、 山区少”的格局；最低气温≤-25℃日数呈现由山区向平原逐渐减少的特点；终霜冻日早于≥10℃初日天数的空间分布总体呈现山区少平原多的格局。在上述各指标气候要素空间特征的综合作用下，叶城县核桃种植可分为适宜、次适宜和不适宜三个分区。适宜区主要分布在县域北部海拔低于1400m的平原地带，该区能够满足核桃生长发育和优质高产对热量条件的需求，同时，核桃树遭受越冬冻害的风险很低，春季核桃树展叶、开花和结实期遭受霜冻危害的几率也很低，因此，适宜区是叶城县发展核桃种植业最理想的区域，加之，该区地处叶尔羌河上游流域，土壤肥沃，灌溉有保障，应大力发展优质核桃种植面积。次适宜区分布在县域中部海拔1400～2000m的山前倾斜平原和丘陵地带，该区核桃树具有一定的遭受越冬冻害的风险，不宜大规模发展核桃种植。不适宜区分布在叶城县南部海拔2000m以上的山区，该区域核桃树遭受越冬冻害的风险较高，因此，不宜种植核桃。