17 research outputs found
Impact of period and timescale of FDDA analysis nudging on the numerical simulation of tropical cyclones in the Bay of Bengal
No full textIn this study, the impact of four-dimensional data assimilation (FDDA) analysis nudging is examined on the prediction of tropical cyclones (TC) in the Bay of Bengal to determine the optimum period and timescale of nudging. Six TCs (SIDR: November 13–16, 2007; NARGIS: April 29–May 02, 2008; NISHA: November 25–28, 2008; AILA: May 23–26, 2009; LAILA: May 18–21, 2010; JAL: November 04–07, 2010) were simulated with a doubly nested Weather Research and Forecasting (WRF) model with a horizontal resolution of 9 km in the inner domain. In the control run for each cyclone, the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) analysis and forecasts at 0.5_ resolution are used for initial and boundary conditions. In the FDDA experiments available surface, upper air observations obtained from NCEP Atmospheric Data Project (ADP) data sets were used for assimilation after merging with the first guess through objective analysis procedure. Analysis nudging experiments with different nudging periods (6, 12, 18, and 24 h) indicated a period of 18 or 24 h of nudging during the pre-forecast stage provides maximum impact on simulations in terms of minimum track and intensity forecasts. To determine the optimum timescale of nudging, two cyclone cases (NARGIS: April 28–May 02, 2008; NISHA: November 25–28, 2008) were simulated varying the inverse timescales as 1.0e-4 to 5.0e-4 s−1 in steps of 1.0e-4 s−1. A positive impact of assimilation is found on the simulated characteristics with a nudging coefficient of either 3.0e-4 or 4.0e-4 s−1 which corresponds to a timescale of about 1 h for nudging dynamic (u,v) and thermodynamical (t,q) fields.Authors sincerely thank Dr. Satyamurty Director, EIRSG, Dr. B. Venkatrman, AD, RSEG and Dr. R. Baskaran Head, RIAS for their encouragement and support in carrying out the study. The first author acknowledges the Space Applications Centre, Ahmadabad for the award of the Junior Research Fellowship under MeghaTropiques-Utilization Project under which this research was carried out. The WRF-ARW model was obtained from NCAR. The NCEP GFS analysis and forecasts were downloaded from NCEP. The QSCAT data were obtained from NASA. The prepbufr surface upper air observations are taken from the online archives of NCAR. Authors thank the anonymous reviewers for critical reviews and valuable comments, which helped to improve the manuscript
Fully Differential Difference Amplifier based Microphone Interface Circuit and an Adaptive Signal to Noise Ratio Analog Front end for Dual Channel Digital Hearing Aids
No full textabstract: A dual-channel directional digital hearing aid (DHA) front-end using a fully differential difference amplifier (FDDA) based Microphone interface circuit (MIC) for a capacitive Micro Electro Mechanical Systems (MEMS) microphones and an adaptive-power analog font end (AFE) is presented. The Microphone interface circuit based on FDDA converts the capacitance variations into voltage signal, achieves a noise of 32 dB SPL (sound pressure level) and an SNR of 72 dB, additionally it also performs single to differential conversion allowing for fully differential analog signal chain. The analog front-end consists of 40dB VGA and a power scalable continuous time sigma delta ADC, with 68dB SNR dissipating 67u¬W from a 1.2V supply. The ADC implements a self calibrating feedback DAC, for calibrating the 2nd order non-linearity. The VGA and power scalable ADC is fabricated on 0.25 um CMOS TSMC process. The dual channels of the DHA are precisely matched and achieve about 0.5dB gain mismatch, resulting in greater than 5dB directivity index. This will enable a highly integrated and low power DHADissertation/ThesisPh.D. Electrical Engineering 201
New records of Stratiomyidae (Diptera) from the Near East with a key to the species of Israel, Sinai and the Golan
No full textA supplement is given to the publications of the senior author (Lindner, 1974 and 1975) on the Stratiomyidae of the Near East. Pachygaster atra Panzer and Aspidacantha atra Kertesz (Pachygastrinae) are recorded from the area for the first time. The male of Heradina galeata Lindner is described for the first time. New synonyms are established, and a key is given to all the species recorded so far from the area
Impacts of using an ensemble Kalman filter on air quality simulations along the California-Mexico border region during Cal-Mex 2010 Field Campaign
No full textThe purpose of this study is to investigate the impact of using an ensemble Kalman filter (EnKF) on air quality simulations in the California-Mexico border region on two days (May 30 and June 04, 2010) during Cal-Mex 2010, The uncertainties in ozone (O-3) and aerosol simulations in the border area due to the meteorological initial uncertainties were examined through ensemble simulations. The ensemble spread of surface O-3 averaged over the coastal region was less than 10 ppb. The spreads in the nitrate and ammonium aerosols are substantial on both days, mostly caused by the large uncertainties in the surface temperature and humidity simulations. In general, the forecast initialized with the EnKF analysis (EnKF) improved the simulation of meteorological fields to some degree in the border region compared to the reference forecast initialized with NCEP analysis data (FCST) and the simulation with observation nudging (FDDA), which in turn leading to reasonable air quality simulations. The simulated surface O-3 distributions by EnKF were consistently better than FCST and FDDA on both days. EnKF usually produced more reasonable simulations of nitrate and ammonium aerosols compared to the observations, but still have difficulties in improving the simulations of organic and sulfate aerosols. However, discrepancies between the EnKF simulations and the measurements were still considerably large, particularly for sulfate and organic aerosols, indicating that there are still ample rooms for improvement in the present data assimilation and/or the modeling systems. (C) 2014 Elsevier B.V. All rights reserved.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000343613200016&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Environmental SciencesSCI(E)[email protected]; [email protected]
Correction to: Free Diced Dorsal Augmentation (FDDA) rhinoplasty in non-caucasian patients: tips and tricks (European Journal of Plastic Surgery, (2025), 48, 1, (7), 10.1007/s00238-024-02259-1)
No full textIn this article the author’s name ‘Gianluca Marcaccini’ was incorrectly written as ‘Gianlcua Marcaccini’. Authors ‘Mirco Pozzi’ and ‘Pietro Susini’ should have been denoted as equally contributing author[s]. The original article has been corrected
Disentangling regional and local tree diversity in the Amazon
No full textThis is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordWe analyzed the most extensive data set of tree inventory plots spread over the complete Amazon basin and Guiana shield. We aimed to separate the regional and local tree alpha‐diversity to investigate the drivers of diversity at the relevant scale. Our results are consistent with the partitioning of total tree alpha‐diversity into regional and local components, which are controlled by evolutionary‐ and ecological processes, respectively. Regional diversity is correlated with palaeo‐climatic stability (31%), and long‐term large‐scale ecosystem dynamics (14%), as represented by the age of the geological formation. Both mechanisms contribute to high diversity in the central to western Amazon. Actual rainfall seasonality is correlated with regional tree diversity to a certain extent (19%), but we argue that this is of little consequence for the evolutionary drivers of the regional species pool. Frequency of disturbance is the main process driving local diversity, although its explanatory power is relatively small (17%).The first author was supported by PAN‐AMAZONIA project, Inst. Internacional de Educação do Brasil (BECA program) and Conselho Nacional de Ciência e Tecnologia (CNPq – Brazil)
Species Distribution Modelling: Contrasting presence-only models with plot abundance data
No full textSpecies distribution models (SDMs) are widely used in ecology and conservation. Presence-only SDMs such as MaxEnt frequently use natural history collections (NHCs) as occurrence data, given their huge numbers and accessibility. NHCs are often spatially biased which may generate inaccuracies in SDMs. Here, we test how the distribution of NHCs and MaxEnt predictions relates to a spatial abundance model, based on a large plot dataset for Amazonian tree species, using inverse distance weighting (IDW). We also propose a new pipeline to deal with inconsistencies in NHCs and to limit the area of occupancy of the species. We found a significant but weak positive relationship between the distribution of NHCs and IDW for 66% of the species. The relationship between SDMs and IDW was also significant but weakly positive for 95% of the species, and sensitivity for both analyses was high. Furthermore, the pipeline removed half of the NHCs records. Presence-only SDM applications should consider this limitation, especially for large biodiversity assessments projects, when they are automatically generated without subsequent checking. Our pipeline provides a conservative estimate of a species' area of occupancy, within an area slightly larger than its extent of occurrence, compatible to e.g. IUCN red list assessments
Hyperdominance in the Amazonian tree flora
No full textThe vast extent of the Amazon Basin has historically restricted the study of its tree communities to the local and regional scales. Here, we provide empirical data on the commonness, rarity, and richness of lowland tree species across the entire Amazon Basin and Guiana Shield (Amazonia), collected in 1170 tree plots in all major forest types. Extrapolations suggest that Amazonia harbors roughly 16,000 tree species, of which just 227 (1.4%) account for half of all trees. Most of these are habitat specialists and only dominant in one or two regions of the basin. We discuss some implications of the finding that a small group of species--less diverse than the North American tree flora--accounts for half of the world's most diverse tree community
Disentangling regional and local tree diversity in the Amazon
No full textWe analyzed the most extensive data set of tree inventory plots spread over the complete Amazon basin and Guiana shield. We aimed to separate the regional and local tree alpha‐diversity to investigate the drivers of diversity at the relevant scale. Our results are consistent with the partitioning of total tree alpha‐diversity into regional and local components, which are controlled by evolutionary‐ and ecological processes, respectively. Regional diversity is correlated with palaeo‐climatic stability (31%), and long‐term large‐scale ecosystem dynamics (14%), as represented by the age of the geological formation. Both mechanisms contribute to high diversity in the central to western Amazon. Actual rainfall seasonality is correlated with regional tree diversity to a certain extent (19%), but we argue that this is of little consequence for the evolutionary drivers of the regional species pool. Frequency of disturbance is the main process driving local diversity, although its explanatory power is relatively small (17%)
Hyperdominance in the Amazonian tree flora
No full textIntroduction: Recent decades have seen a major international effort to inventory tree communities in the Amazon Basin and Guiana Shield (Amazonia), but the vast extent and record diversity of these forests have hampered an understanding of basinwide patterns. To overcome this obstacle, we compiled and standardized species-level data on more than half a million trees in 1170 plots sampling all major lowland forest types to explore patterns of commonness, rarity, and richness.
Methods: The ~6-million-km2 Amazonian lowlands were divided into 1° cells, and mean tree density was estimated for each cell by using a loess regression model that included no environmental data but had its basis exclusively in the geographic location of tree plots. A similar model, allied with a bootstrapping exercise to quantify sampling error, was used to generate estimated Amazon-wide abundances of the 4962 valid species in the data set. We estimated the total number of tree species in the Amazon by fitting the mean rank-abundance data to Fisher’s log-series distribution.
Results :Our analyses suggest that lowland Amazonia harbors 3.9 × 1011 trees and ~16,000 tree species. We found 227 “hyperdominant” species (1.4% of the total) to be so common that together they account for half of all trees in Amazonia, whereas the rarest 11,000 species account for just 0.12% of trees. Most hyperdominants are habitat specialists that have large geographic ranges but are only dominant in one or two regions of the basin, and a median of 41% of trees in individual plots belong to hyperdominants. A disproportionate number of hyperdominants are palms, Myristicaceae, and Lecythidaceae.
Discussion: The finding that Amazonia is dominated by just 227 tree species implies that most biogeochemical cycling in the world’s largest tropical forest is performed by a tiny sliver of its diversity. The causes underlying hyperdominance in these species remain unknown. Both competitive superiority and widespread pre-1492 cultivation by humans are compelling hypotheses that deserve testing. Although the data suggest that spatial models can effectively forecast tree community composition and structure of unstudied sites in Amazonia, incorporating environmental data may yield substantial improvements. An appreciation of how thoroughly common species dominate the basin has the potential to simplify research in Amazonian biogeochemistry, ecology, and vegetation mapping. Such advances are urgently needed in light of the >10,000 rare, poorly known, and potentially threatened tree species in the Amazon
