Analyses and forecasts of a tornadic supercell outbreak using a 3DVAR system ensemble

As part of NOAA’s "Warn-On-Forecast" initiative, a convective-scale data assimilation and prediction system was developed using the WRF-ARW model and ARPS 3DVAR data assimilation technique. The system was then evaluated using retrospective short-range ensemble analyses and probabilistic forecasts of the tornadic supercell outbreak event that occurred on 24 May 2011 in Oklahoma, USA. A 36-member multi-physics ensemble system provided the initial and boundary conditions for a 3-km convective-scale ensemble system. Radial velocity and reflectivity observations from four WSR-88 Ds were assimilated into the ensemble using the ARPS 3DVAR technique. Five data assimilation and forecast experiments were conducted to evaluate the sensitivity of the system to data assimilation frequencies, in-cloud temperature adjustment schemes, and fixed- and mixed-microphysics ensembles. The results indicated that the experiment with 5-min assimilation frequency quickly built up the storm and produced a more accurate analysis compared with the 10-min assimilation frequency experiment. The predicted vertical vorticity from the moist-adiabatic in-cloud temperature adjustment scheme was larger in magnitude than that from the latent heat scheme. Cycled data assimilation yielded good forecasts, where the ensemble probability of high vertical vorticity matched reasonably well with the observed tornado damage path. Overall, the results of the study suggest that the 3DVAR analysis and forecast system can provide reasonable forecasts of tornadic supercell storms.     

青藏高原东北缘冬给错纳湖全新世湖面波动

青藏高原处于东亚季风、印度季风和西风环流交互作用区.末次冰消期以来,太阳辐射对该地区的古气候环境产生了重要影响,湖泊随着季风系统的变化发生了明显的水位升降,对湖岸阶地的形成起到了直接作用.本项研究重建了青藏高原东北缘冬给错纳湖湖岸阶地记录的湖面波动历史,试图了解青藏高原季风系统演变过程.通过湖泊北岸265 cm厚湖岸阶地沉积物粒度、碳酸盐、矿物、元素和介形虫古环境指标,结合OSL年代模式,分析表明在约10. 2 ka B. P.之前水体较浅;约10. 2~9. 0 ka B. P.湖面开始上升,气候凉湿;9. 0~8. 5 ka B. P.为印度季风强盛期,湖面明显上升,降雨量增高、温度上升;8. 5~7. 9 ka B. P.湖面降低与气候变冷有关;7. 9~7. 0 ka B. P.印度季风开始减弱,气温、降雨下降,但有效湿度较大,湖面降低;7. 0~6. 1 ka B. P.湖面上升可能与低蒸发作用有关,印度季风仍然影响该地区;6. 1~5. 2 ka B. P.,印度季风衰退,气候逐渐变冷、降雨量减小、水体变浅;5. 2~4. 6 ka B. P.气候冷干,有效湿度减小,湖面进一步下降;4. 6 ka B. P.至今气候干冷,东亚季风衰退,湖面下降,期间也可能受西风环流影响而有短暂的降雨增加时期.     

Characterization and advanced oxidation treatment of dyeing effluent by Fenton’s reagent

Textile effluent from dyeing process has been a serious environmental threat for years. This study was intended to evaluate the performance of Fenton’s process for the removal of chemical oxygen demand (COD), colour and turbidity. Experiments were conducted by laboratory-scale reactors fed with cotton dyeing effluent. The Fenton process employs ferrous ions and hydrogen peroxide H₂O₂ under acidic pH conditions. The experimental variables studied include doses of iron salts and hydrogen peroxide, oxidation time, pH for oxidation and coagulation. The COD, color and turbidity removal reached a maximum of 97.2, 96.8 and 84.8% respectively at a reaction time of 20 min under optimum doses of H₂O₂ and Fe²⁺. Hydrogen peroxide dose ranging from 0.5 to 2.0 mL/500 mL and FeSO₄ · 7H₂O in the range of 0.5–4.0 gm/500 mL were selected to be examined at different reaction times between 10 and 30 min. Optimum dose of hydrogen peroxide and ferrous sulphate were 2.0 mL and 1.0 gm respectively for 500 mL of sample. In this study optimized pH 4.0 and 6.0 was found effective for oxidation and coagulation respectively.     

Origin of trondhjemite and albitite at the expense of A-type granite,Aravalli orogen,India:Evidence from new metasomatic replacement fronts

The A-type Harsora-Dadikar granites in the Alwar complex of northern Aravalli orogen,NW India provide evidence for subsolidus-requilibration of feldspars.They record three new discrete stages of albitisation,producing trondhjemite and albitite sequentially at the expense of original granite.Stage-Ⅰ metasomatism deanorthised the magmatic oligoclase and transformed the grey least-albitised granite to pinkish grey microcline-oligoclase granite.Stage-II converted the latter to trondhjemite by replacement of microcline to oligoclase.Stage-Ⅲ metasomatism led to the formation of albitite/albite granite from trondhjemite,where the metasomatically formed oligoclase was replaced by albite.This stage of metasomatism resulted in nearly complete disappearance of amphibole and biotite,producing a monomineralic rock(albitite),which is consistent with Korzhinskii theory of infiltration metasomatism.The reaction fronts delineating the Stage-Ⅱ and Stage-Ⅲ are sharp and easily discernible by their prominent color differences in Harsora on the outcrop scale.Chemically,the mineral transformations during three stages are manifested by the differential gains/losses in Na,K,Ca,Rb,Ba,Sr,Fe and Mg.The formation of albite,Cl-rich marialitic scapolite and Cl-rich amphibole in the albitised granites are suggestive of Naand Cl-brines as the metasomatising fluids.The fluid-rock interactions,which can significantly transform the pristine mineralogy of granitoids,should be carefully considered to avoid any misinterpretations about their petrological history.     

Spatial variability of climatic hazards in Bangladesh

Natural Hazards - Climate change is evident with the extreme climatic indices changing all over the world. Bangladesh is one of the most vulnerable countries to climate change. The patterns of...