Relevant bibliographies by topics / Assimilation

Academic literature on the topic 'Assimilation'

Author: Grafiati
Published: 4 June 2021
Last updated: 31 July 2024

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Journal articles on the topic "Assimilation"

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Tang, Wenfu, Benjamin Gaubert, Louisa Emmons, Daniel Ziskin, Debbie Mao, David Edwards, Avelino Arellano, Kevin Raeder, Jeffrey Anderson, and Helen Worden. "Advantages of assimilating multispectral satellite retrievals of atmospheric composition: a demonstration using MOPITT carbon monoxide products." Atmospheric Measurement Techniques 17, no. 7 (April 5, 2024): 1941–63. http://dx.doi.org/10.5194/amt-17-1941-2024.

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Abstract. The Measurements Of Pollution In The Troposphere (MOPITT) is an ideal instrument to understand the impact of (1) assimilating multispectral and joint retrievals versus single spectral products, (2) assimilating satellite profile products versus column products, and (3) assimilating multispectral and joint retrievals versus assimilating individual products separately. We use the Community Atmosphere Model with chemistry with the Data Assimilation Research Testbed (CAM-chem+DART) to assimilate different MOPITT carbon monoxide (CO) products to address these three questions. Both anthropogenic and fire CO emissions are optimized in the data assimilation experiments. The results are compared with independent CO observations from TROPOspheric Monitoring Instrument (TROPOMI), the Total Carbon Column Observing Network (TCCON), NOAA Carbon Cycle Greenhouse Gases (CCGG) sites, In-service Aircraft for a Global Observing System (IAGOS), and Western wildfire Experiment for Cloud chemistry, Aerosol absorption and Nitrogen (WE-CAN). We find that (1) assimilating the MOPITT joint (multispectral; near-IR and thermal IR) column product leads to better model–observation agreement at and near the surface than assimilating the MOPITT thermal-IR-only column retrieval. (2) Assimilating column products has a larger impact and improvement for background and large-scale CO compared to assimilating profile products due to vertical localization in profile assimilation. However, profile assimilation can outperform column assimilations in fire-impacted regions and near the surface. (3) Assimilating multispectral and joint products results in similar or slightly better agreement with observations compared to assimilating the single spectral products separately.
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Nie, Suping, Xiaolong Jia, Weitao Deng, Yixiong Lu, Dongyan He, Liang Zhao, Weihua Cao, and Xueliang Deng. "The Influence of FY-4A High-Frequency LST Data on Data Assimilation in a Climate Model." Remote Sensing 15, no. 1 (December 22, 2022): 59. http://dx.doi.org/10.3390/rs15010059.

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Based on the Beijing Climate Center’s land surface model BCC_AVIM2.0, an ensemble Kalman filter (EnKF) algorithm is developed to assimilate the land surface temperature (LST) product of the first satellite of Fengyun-4 series meteorological satellites of China to study the influence of LST data with different time frequencies on the surface temperature data assimilations. The MODIS daytime and nighttime LST products derived from Terra and Aqua satellites are used as independent validation data to test the assimilation results. The results show that diurnal variation information in the FY-4A LST data has significant effect on the assimilation results. When the time frequencies of the assimilated FY-4A LST data are sufficient, the assimilation scheme can effectively reduce the errors and the assimilation results reflect more reasonable spatial and temporal distributions. The assimilation experiments with a 3 h time frequency show less bias as well as RMSEs and higher temporal correlations than that of the model simulations at both daytime and nighttime periods. As the temporal frequency of assimilated LST observations decreases, the assimilation effects gradually deteriorate. When diurnal variation information is not considered at all in the assimilation, the assimilation with 24 h time frequency showed the largest errors and smallest time correlations in all experiments. The results demonstrate the potential of assimilating high-frequency FY-4A LST data to improve the performance of the BCC_AVIM2.0 land surface model. Furthermore, this study indicates that the diurnal variation information is a necessary factor needed to be considered when assimilating the FY-4A LST.
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Cheng, Yueming, Tie Dai, Daisuke Goto, Nick A. J. Schutgens, Guangyu Shi, and Teruyuki Nakajima. "Investigating the assimilation of CALIPSO global aerosol vertical observations using a four-dimensional ensemble Kalman filter." Atmospheric Chemistry and Physics 19, no. 21 (November 5, 2019): 13445–67. http://dx.doi.org/10.5194/acp-19-13445-2019.

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Abstract. Aerosol vertical information is critical to quantify the influences of aerosol on the climate and environment; however, large uncertainties still persist in model simulations. In this study, the vertical aerosol extinction coefficients from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) are assimilated to optimize the hourly aerosol fields of the Non-hydrostatic ICosahedral Atmospheric Model (NICAM) online coupled with the Spectral Radiation Transport Model for Aerosol Species (SPRINTARS) using a four-dimensional local ensemble transform Kalman filter (4-D LETKF). A parallel assimilation experiment using bias-corrected aerosol optical thicknesses (AOTs) from the Moderate Resolution Imaging Spectroradiometer (MODIS) is conducted to investigate the effects of assimilating the observations (and whether to include vertical information) on the model performances. Additionally, an experiment simultaneously assimilating both CALIOP and MODIS observations is conducted. The assimilation experiments are successfully performed for 1 month, making it possible to evaluate the results in a statistical sense. The hourly analyses are validated via both the CALIOP-observed aerosol vertical extinction coefficients and the AOT observations from MODIS and the AErosol RObotic NETwork (AERONET). Our results reveal that both the CALIOP and MODIS assimilations can improve the model simulations. The CALIOP assimilation is superior to the MODIS assimilation in modifying the incorrect aerosol vertical distributions and reproducing the real magnitudes and variations, and the joint CALIOP and MODIS assimilation can further improve the simulated aerosol vertical distribution. However, the MODIS assimilation can better reproduce the AOT distributions than the CALIOP assimilation, and the inclusion of the CALIOP observations has an insignificant impact on the AOT analysis. This is probably due to the nadir-viewing CALIOP having much sparser coverage than MODIS. The assimilation efficiencies of CALIOP decrease with increasing distances of the overpass time, indicating that more aerosol vertical observation platforms are required to fill the sensor-specific observation gaps and hence improve the aerosol vertical data assimilation.
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Sun, Juanzhen, Ying Zhang, Junmei Ban, Jing-Shan Hong, and Chung-Yi Lin. "Impact of Combined Assimilation of Radar and Rainfall Data on Short-Term Heavy Rainfall Prediction: A Case Study." Monthly Weather Review 148, no. 5 (May 1, 2020): 2211–32. http://dx.doi.org/10.1175/mwr-d-19-0337.1.

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Abstract Radar and surface rainfall observations are two sources of operational data crucial for heavy rainfall prediction. Their individual values on improving convective forecasting through data assimilation have been examined in the past using convection-permitting numerical models. However, the benefit of their simultaneous assimilations has not yet been evaluated. The objective of this study is to demonstrate that, using a 4D-Var data assimilation system with a microphysical scheme, these two data sources can be assimilated simultaneously and the combined assimilation of radar data and estimated rainfall data from radar reflectivity and surface network can lead to improved short-term heavy rainfall prediction. In our study, a combined data assimilation experiment is compared with a rainfall-only and a radar-only (with or without reflectivity) experiments for a heavy rainfall event occurring in Taiwan during the passage of a mei-yu system. These experiments are conducted by applying the Weather Research and Forecasting (WRF) 4D-Var data assimilation system with a 20-min time window aiming to improve 6-h convective heavy rainfall prediction. Our results indicate that the rainfall data assimilation contributes significantly to the analyses of humidity and temperature whereas the radar data assimilation plays a crucial role in wind analysis, and further, combining the two data sources results in reasonable analyses of all three fields by eliminating large, unphysical analysis increments from the experiments of assimilating individual data only. The results also show that the combined assimilation improves forecasts of heavy rainfall location and intensity of 6-h accumulated rainfall for the case studied.
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Thodsan, Thippawan, Falin Wu, Kritanai Torsri, Thakolpat Khampuenson, and Gongliu Yang. "Impact of the Assimilation of Multi-Platform Observations on Heavy Rainfall Forecasts in Kong-Chi Basin, Thailand." Atmosphere 12, no. 11 (November 12, 2021): 1497. http://dx.doi.org/10.3390/atmos12111497.

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Data assimilation with a Numerical Weather Prediction (NWP) model using an observation system in a regional area is becoming more prevalent for local weather forecasting activities to reduce the risk of disasters. In this study, we evaluated the predictive capabilities of multi-platform observation assimilation based on a WRFDA (Weather Research and Forecasting model data assimilation) system with 9 km grid spacing over the Kong-Chi basin (KCB), where tropical storms and heavy rainfall occur frequently. Data assimilation experiments were carried out with two assimilation schemes: (1) assimilating the combined multi-platform observations of PREPBUFR data from the National Centers for Environmental Prediction (NCEP) and Automatic Weather Stations (AWS) data from the National Hydroinformatics Data Center in Thailand, and (2) assimilating the AWS data only, which are referred to as DAALL and DAAWS, respectively. Assimilation experiments skill scores with lead times of 48 h and 72 h were evaluated by comparing their accumulated rainfall and mean temperatures every three hours in the AWS for heavy rainfall events that occurred on 28 July 2017 and 30 August 2019. The results show that the DAALL improved the statistical skill scores by improving the pattern and intensity of heavy rainfall events, and DAAWS also improved the model results of near-surface location forecasts. The accuracy of the two assimilations for 3 h of accumulated rainfall with a 5 mm threshold, was only above 70%, but the threat score was acceptable. Temperature observations and assimilation experiments fitted a significant correlation with a coefficient greater than 0.85, while the mean absolute errors, even at the 48 h lead times remained below 1.75 °C of the mean temperature. The variables of the AWS observations in real-time after combining them with the weather forecasting model were evaluated for unprecedented rain events in the KCB. The scores suggested that the assimilation of the multi-platform observations at the 48 h lead times has an impact on heavy rainfall prediction in terms of the threat score, compared to the assimilation of AWS data only. The reason for this could be that fewer observations of the AWS data affected the WRFDA model.
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Crow, Wade T., and Emiel Van Loon. "Impact of Incorrect Model Error Assumptions on the Sequential Assimilation of Remotely Sensed Surface Soil Moisture." Journal of Hydrometeorology 7, no. 3 (June 1, 2006): 421–32. http://dx.doi.org/10.1175/jhm499.1.

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Abstract Data assimilation approaches require some type of state forecast error covariance information in order to optimally merge model predictions with observations. The ensemble Kalman filter (EnKF) dynamically derives such information through a Monte Carlo approach and the introduction of random noise in model states, fluxes, and/or forcing data. However, in land data assimilation, relatively little guidance exists concerning strategies for selecting the appropriate magnitude and/or type of introduced model noise. In addition, little is known about the sensitivity of filter prediction accuracy to (potentially) inappropriate assumptions concerning the source and magnitude of modeling error. Using a series of synthetic identical twin experiments, this analysis explores the consequences of making incorrect assumptions concerning the source and magnitude of model error on the efficiency of assimilating surface soil moisture observations to constrain deeper root-zone soil moisture predictions made by a land surface model. Results suggest that inappropriate model error assumptions can lead to circumstances in which the assimilation of surface soil moisture observations actually degrades the performance of a land surface model (relative to open-loop assimilations that lack a data assimilation component). Prospects for diagnosing such circumstances and adaptively correcting the culpable model error assumptions using filter innovations are discussed. The dual assimilation of both runoff (from streamflow) and surface soil moisture observations appears to offer a more robust assimilation framework where incorrect model error assumptions are more readily diagnosed via filter innovations.
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Tian, X., Z. Xie, Y. Liu, Z. Cai, Y. Fu, H. Zhang, and L. Feng. "A joint data assimilation system (Tan-Tracker) to simultaneously estimate surface CO<sub>2</sub> fluxes and 3-D atmospheric CO<sub>2</sub> concentrations from observations." Atmospheric Chemistry and Physics 14, no. 23 (December 12, 2014): 13281–93. http://dx.doi.org/10.5194/acp-14-13281-2014.

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Abstract. We have developed a novel framework ("Tan-Tracker") for assimilating observations of atmospheric CO2 concentrations, based on the POD-based (proper orthogonal decomposition) ensemble four-dimensional variational data assimilation method (PODEn4DVar). The high flexibility and the high computational efficiency of the PODEn4DVar approach allow us to include both the atmospheric CO2 concentrations and the surface CO2 fluxes as part of the large state vector to be simultaneously estimated from assimilation of atmospheric CO2 observations. Compared to most modern top-down flux inversion approaches, where only surface fluxes are considered as control variables, one major advantage of our joint data assimilation system is that, in principle, no assumption on perfect transport models is needed. In addition, the possibility for Tan-Tracker to use a complete dynamic model to consistently describe the time evolution of CO2 surface fluxes (CFs) and the atmospheric CO2 concentrations represents a better use of observation information for recycling the analyses at each assimilation step in order to improve the forecasts for the following assimilations. An experimental Tan-Tracker system has been built based on a complete augmented dynamical model, where (1) the surface atmosphere CO2 exchanges are prescribed by using a persistent forecasting model for the scaling factors of the first-guess net CO2 surface fluxes and (2) the atmospheric CO2 transport is simulated by using the GEOS-Chem three-dimensional global chemistry transport model. Observing system simulation experiments (OSSEs) for assimilating synthetic in situ observations of surface CO2 concentrations are carefully designed to evaluate the effectiveness of the Tan-Tracker system. In particular, detailed comparisons are made with its simplified version (referred to as TT-S) with only CFs taken as the prognostic variables. It is found that our Tan-Tracker system is capable of outperforming TT-S with higher assimilation precision for both CO2 concentrations and CO2 fluxes, mainly due to the simultaneous estimation of CO2 concentrations and CFs in our Tan-Tracker data assimilation system. A experiment for assimilating the real dry-air column CO2 retrievals (XCO2) from the Japanese Greenhouse Gases Observation Satellite (GOSAT) further demonstrates its potential wide applications.
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Xie, J., F. Counillon, J. Zhu, and L. Bertino. "An eddy resolving tidal-driven model of the South China Sea assimilating along-track SLA data using the EnOI." Ocean Science 7, no. 5 (October 6, 2011): 609–27. http://dx.doi.org/10.5194/os-7-609-2011.

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Abstract. The upper ocean circulation in the South China Sea (SCS) is driven by the Asian monsoon, the Kuroshio intrusion through the Luzon Strait, strong tidal currents, and a complex topography. Here, we demonstrate the benefit of assimilating along-track altimeter data into a nested configuration of the HYbrid Coordinate Ocean Model that includes tides. Including tides in models is important because they interact with the main circulation. However, assimilation of altimetry data into a model including tides is challenging because tides and mesoscale features contribute to the elevation of ocean surface at different time scales and require different corrections. To address this issue, tides are filtered out of the model output and only the mesoscale variability is corrected with a computationally cheap data assimilation method: the Ensemble Optimal Interpolation (EnOI). This method uses a running selection of members to handle the seasonal variability and assimilates the track data asynchronously. The data assimilative system is tested for the period 1994–1995, during which time a large number of validation data are available. Data assimilation reduces the Root Mean Square Error of Sea Level Anomalies from 9.3 to 6.9 cm and improves the representation of the mesoscale features. With respect to the vertical temperature profiles, the data assimilation scheme reduces the errors quantitatively with an improvement at intermediate depth and deterioration at deeper depth. The comparison to surface drifters shows an improvement of surface current by approximately −9% in the Northern SCS and east of Vietnam. Results are improved compared to an assimilative system that does not include tides and a system that does not consider asynchronous assimilation.
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Wang, Bingli, Wei Cheng, Yansong Bao, Shudong Wang, George P. Petropoulos, Shuiyong Fan, Jiajia Mao, Ziqi Jin, and Zihui Yang. "Effects of Assimilating Ground-Based Microwave Radiometer and FY-3D MWTS-2/MWHS-2 Data in Precipitation Forecasting." Remote Sensing 16, no. 14 (July 22, 2024): 2682. http://dx.doi.org/10.3390/rs16142682.

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This study investigates the impacts of the joint assimilation of ground-based microwave radiometer (MWR) and FY-3D microwave sounder (MWTS-2/MWHS-2) observations on the analyses and forecasts for precipitation forecast. Based on the weather research and forecasting data assimilation (WRFDA) system, four experiments are conducted in this study, concerning a heavy precipitation event in Beijing on 2 July 2021, and 10-day batch experiments were also conducted. The key study findings include the following: (1) Both ground-based microwave radiometer and MWTS-2/MWHS-2 data contribute to improvements in the initial fields of the model, leading to appropriate adjustments in the thermal structure of the model. (2) The forecast fields of the experiments assimilating ground-based microwave radiometer and MWTS-2/MWHS-2 data show temperature and humidity performances closer to the true fields compared with the control experiment. (3) Separate assimilation of two types of microwave radiometer data can improve precipitation forecasts, while joint assimilation provides the most accurate forecasts among all the experiments. In the single-case, compared with the control experiment, the individual and combined assimilation of MWR and MWTS-2/MWHS-2 improves the six-hour cumulative precipitation threat score (TS) at the 25 mm level by 57.1%, 28.9%, and 38.2%, respectively. The combined assimilation also improves the scores at the 50 mm level by 54.4%, whereas individual assimilations show a decrease in performance. In the batch experiments, the MWR_FY experiment’s TS of 24 h precipitation forecast improves 28.5% at 10 mm and 330% at 25 mm based on the CTRL.
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Anderson, Jeffrey L., Bruce Wyman, Shaoqing Zhang, and Timothy Hoar. "Assimilation of Surface Pressure Observations Using an Ensemble Filter in an Idealized Global Atmospheric Prediction System." Journal of the Atmospheric Sciences 62, no. 8 (August 1, 2005): 2925–38. http://dx.doi.org/10.1175/jas3510.1.

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Abstract An ensemble filter data assimilation system is tested in a perfect model setting using a low resolution Held–Suarez configuration of an atmospheric GCM. The assimilation system is able to reconstruct details of the model’s state at all levels when only observations of surface pressure (PS) are available. The impacts of varying the spatial density and temporal frequency of PS observations are examined. The error of the ensemble mean assimilation prior estimate appears to saturate at some point as the number of PS observations available once every 24 h is increased. However, increasing the frequency with which PS observations are available from a fixed network of 1800 randomly located stations results in an apparently unbounded decrease in the assimilation’s prior error for both PS and all other model state variables. The error reduces smoothly as a function of observation frequency except for a band with observation periods around 4 h. Assimilated states are found to display enhanced amplitude high-frequency gravity wave oscillations when observations are taken once every few hours, and this adversely impacts the assimilation quality. Assimilations of only surface temperature and only surface wind components are also examined. The results indicate that, in a perfect model context, ensemble filters are able to extract surprising amounts of information from observations of only a small portion of a model’s spatial domain. This suggests that most of the remaining challenges for ensemble filter assimilation are confined to problems such as model error, observation representativeness error, and unknown instrument error characteristics that are outside the scope of perfect model experiments. While it is dangerous to extrapolate from these simple experiments to operational atmospheric assimilation, the results also suggest that exploring the frequency with which observations are used for assimilation may lead to significant enhancements to assimilated state estimates.
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Dissertations / Theses on the topic "Assimilation"

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Le, Andrew Nguyen. "Assimilating through social networks? The importance of networks in assimilation trajectories." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42483.

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The assimilation outcomes of second generation youths have been hotly debated amongst scholars (Alba et al. 2011, Haller et al. 2011). While the outcomes are contested, it is undeniable that ethnic organizations play a central role in the second generation’s assimilation trajectory. Zhou and Bankston (1998) suggest that participating in ethnic religious institutions promotes upward assimilation through instilling an ethnic identity onto youths. My research on the greater Seattle area Vietnamese Buddhist youth organizations uncovered similar mechanisms that led to Zhou and Bankston’s overall quantitative findings, but also uncover the importance of resource brokering and networks. Based on 43 in-depth interviews, I find that organization participation promotes upward and downward assimilation, and the friendships formed inside ethnic organizations play a crucial role in assimilation outcomes. My project shows that participation in Buddhist youth groups instills a Vietnamese-American identity on youths and, in turn, this ethnic identity can lead to upward assimilation only if the individual is part of a peer network that promotes normative values. Downward assimilation can be associated with youth group participation if the youths enter peer networks that promote deviant behaviors. These deviant peer networks can supersede the positive effects of the youth organization’s overall influence on the individual.
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Peubey, Carole. "Assimilation of ENVISAT data in an advanced data assimilation system." Thesis, University of Reading, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485367.

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i~to a stratosphere-troposphere version of the Met Office assimilation system, producing one of the first analyses to reproduce the September 2002 split of the Antarctic polar vortex. The aim of the project was to investigate the benefit of assimilating MIPAS retrievals and to assess the Met Office 3D-Var assimilation system by examining its different components. The ozone analysis was found to agree with independent ozone observations through most of the middle and upper stratosphere, biases above 60 hPa being within the range -20% to +10% and typically smaller. More significant positive biases were found in the lower stratosphere and inside the polar vortex. Although ozone amounts are shown to be slightly overestimated by MIPAS retrievals in these same regions, these biases are demonstrated to be caused by shortcomings in the model chemistry and transport. MIPAS data have been shown to have a limited impact on the Met Office temperature analysis, although a ' positive effect was identified at the mesopause. It is shown that MIPAScould bring larger benefits if more realistic background error statistics were used for ozone, especially in the lower stratosphere. Based on an evaluation of these statistics using independent datasets, it is suggested that background error variances should be decreased near the ozone maximum and increased below 70 hPa It is also recommended to introduce latitudedependence in vertical error correlations and height-dependence in horizontal error correlations. Improvements are also proposed to improve the ozone assimilation in the polar vortex region. Finally, analysed winds have been found to induce errOneous transport of ozone by increasing vertical diffusion of ozone and enhancing the mean zonal circulations. This especially affects the tropics, where ozone analyses reveal excessive exchanges of air parcels between the stratosphere and the troposphere.
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Barillec, Remi Louis. "Bayesian data assimilation." Thesis, Aston University, 2008. http://publications.aston.ac.uk/15276/.

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This thesis addresses data assimilation, which typically refers to the estimation of the state of a physical system given a model and observations, and its application to short-term precipitation forecasting. A general introduction to data assimilation is given, both from a deterministic and stochastic point of view. Data assimilation algorithms are reviewed, in the static case (when no dynamics are involved), then in the dynamic case. A double experiment on two non-linear models, the Lorenz 63 and the Lorenz 96 models, is run and the comparative performance of the methods is discussed in terms of quality of the assimilation, robustness in the non-linear regime and computational time.
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Ali, A. H. "Nitrate assimilation in yeasts." Thesis, Swansea University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635757.

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Torres, Javier. "Essays on immigrant assimilation." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44777.

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This dissertation examines immigrants (to Canada) assimilation problems from a perspective of imperfect human capital transferability. Chapter 2 discusses how much of the immigrant wage gap can be explained by the undervaluation of foreign human capital (education and work experience). The identification of the human capital source (using information available in the 2006 Canadian census) can explain up to 70% of the native-immigrant wage gap. The foreign-born dummy coefficient goes from around -11% to close to -3%. Education acquired in Asia tends to be valued less than education from South America, Africa and East Europe; which in turn is less valued than education from Oceania, the U.S. and the rest of continental Europe. Studying in the UK consistently appears more beneficial than studying in Canada. When incorporating country of origin fixed effects, the different specifications visibly reduce the heterogeneity of country coefficients. The reduction is sizeable for Pakistan, India, China and the Philippines; though their coefficients remain negative. A smaller reduction for Europe, South-East Asia, Hong Kong and the US drives their coefficients close to zero. The UK country of origin dummy has the only persistently positive coefficient. Chapter 3 describes the occupational assimilation process of 2000-2001 immigrants in their first four years. The results show that those with high levels of education experience a more significant decline in their first occupation. Education, though, has a positive and significant effect on occupational improvement; which reduces the size and significance of the negative effect of education on the second occupational gap. It, however, does not change its sign. The same pattern is observed when analyzing occupational gaps through time. Chapter 4 focuses on immigrants' English proficiency improvement. Overall, immigrants show relatively small improvements in language proficiency in the first four years in Canada. Still, those arriving under the family immigrant category with an intermediate or advanced level are less likely to improve and more likely to decrease their English proficiency. Human capital variables (age and education) are also consistently relevant for English proficiency improvement.
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Campbell, Elizabeth M. "Nitrogen assimilation by limpets." Thesis, University of Glasgow, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479100.

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Gregory, Alastair. "Multilevel ensemble data assimilation." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/60645.

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This thesis aims to investigate and improve the efficiency of ensemble transform methods for data assimilation, using an application of multilevel Monte Carlo. Multilevel Monte Carlo is an interesting framework to estimate statistics of discretized random variables, since it uses a hierarchy of discretizations with a refinement in resolution. This is in contrast to standard Monte Carlo estimators that only use a discretization at a fine resolution. A linear combination of sub-estimators, on different levels of this hierarchy, can provide new statistical estimators to random variables at the finest level of resolution with significantly greater efficiency than a standard Monte Carlo equivalent. Therefore, the extension to computing filtering estimators for data assimilation is a natural, but challenging area of study. These challenges arise due to the fact that correlation must be imparted between ensembles on adjacent levels of resolution and maintained during the assimilation of data. The methodology proposed in this thesis, considers coupling algorithms to establish this correlation. This generates multilevel estimators that significantly reduce the computational expense of propagating ensembles of discretizations through time and space, in between stages of data assimilation. An effective benchmark of this methodology is realised by filtering data into high-dimensional spatio-temporal systems, where a high computational complexity is required to solve the underlying partial differential equations. A novel extension of an ensemble transform localisation framework to finite element approximations within random spatio-temporal systems is proposed, in addition to a multilevel equivalent.
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Archangeli, Diana. "Keley-I Consonant Assimilation." University of Arizona Linguistics Circle, 1987. http://hdl.handle.net/10150/226555.

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Keley-i, a Philippine language, has two rules assimilating consonants across a vowel. Such rules might be taken as evidence against the Morphemic Tier Hypothesis (MTH) and against the Locality Condition (LC). The MTH states (1) Morphemic Tier Hypothesis (MTH) If and only if two segments are members of separate morphemes are those two segments aligned in separate phonological tiers. The Keley-i data suggest that the MTH does not hold universally because consonants assimilate across vowels, which has been taken as evidence for two segmental planes in order to prevent the crossing of association lines. The data also create problems for the Locality Condition: (3) Locality Condition (LC) A phonological rule is applicable only if the target and trigger are adjacent. The consonant features assimilate across an intervening vowel: the target and trigger, being skeletal slots, are not adjacent. I suggest here that adopting the feature hierarchy as proposed in Archangeli and Pulleyblank (1986) (which is a modification of Clements 1985) combined with underspecification theory (Archangeli 1984, Pulleyblank 1986, Archangeli and Pulleyblank 1986) allows an analysis of the Keley -i data which permits maintaining the MTH and the LC. A further result is that the Spreading Hypothesis is maintained as well, thus supporting the hypothesis that phonological assimilation is formally expressed in one manner only, namely by insertion of association lines, and not by feature copy rules. (See Hayes 1986, Archangeli and Pulleyblank 1986.) (4) Spreading Hypothesis Phonological assimilation is expressed only by rules adding association lines. The discussion is organized as follows. First, the feature hierarchy and the theory of underspecification are briefly outlined. I then present a partial analysis of the Keley-i data. The analysis consists of a syncope rule and some rules of consonant assimilation. Finally, I return to the problems that Keley -i presents for the MTH and the LC and propose that the relevant Keley-i data are not only in accordance with the MTH and the LC but predicted by the interaction of the two sub -theories, the Feature Hierarchy and Underspecification.
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Fishman, Jonathan. "Young Adults' Assimilation of Parental Divorce: A Developmental Elaboration of the Assimilation Model." Miami University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=miami1240597649.

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Fishman, Jonathan L. "Young adults' assimilation of parental divorce a developmental elaboration of the assimilation model /." Oxford, Ohio : Miami University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1240597649.

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Books on the topic "Assimilation"

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Barth, Kelly. Assimilation. Detroit: Greenhaven Press, 2010.

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Kelly, Barth, ed. Assimilation. Detroit: Greenhaven Press, 2009.

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Kelly, Barth, ed. Assimilation. Detroit: Greenhaven Press, 2009.

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Lahoz, William, Boris Khattatov, and Richard Menard, eds. Data Assimilation. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-540-74703-1.

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Evensen, Geir. Data Assimilation. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03711-5.

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Law, Kody, Andrew Stuart, and Konstantinos Zygalakis. Data Assimilation. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-20325-6.

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Brasseur, Pierre P., and Jacques C. J. Nihoul, eds. Data Assimilation. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-78939-7.

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Rowse, Tim, and Richard Nile. Contesting assimilation. Perth, W.A: API Network, 2005.

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Evensen, Geir, Femke C. Vossepoel, and Peter Jan van Leeuwen. Data Assimilation Fundamentals. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-96709-3.

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Van Leeuwen, Peter Jan, Yuan Cheng, and Sebastian Reich. Nonlinear Data Assimilation. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-18347-3.

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Book chapters on the topic "Assimilation"

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Smokowski, Paul R., and Martica Bacallao. "Assimilation." In Encyclopedia of Adolescence, 187–96. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-1695-2_337.

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Agius, Mark. "Assimilation." In Encyclopedia of Immigrant Health, 238–39. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4419-5659-0_55.

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Steinmetz, Horst. "Assimilation." In Wie international ist die Literaturwissenschaft?, 337–45. Stuttgart: J.B. Metzler, 1996. http://dx.doi.org/10.1007/978-3-476-03631-5_19.

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Kühnen, Ulrich, and Dora Simunovic. "Assimilation." In Encyclopedia of Evolutionary Psychological Science, 1–4. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-16999-6_2408-1.

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Gori, Simone. "Assimilation." In Encyclopedia of Color Science and Technology, 1–4. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-642-27851-8_272-1.

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Gori, Simone. "Assimilation." In Encyclopedia of Color Science and Technology, 1–4. Berlin, Heidelberg: Springer Berlin Heidelberg, 2020. http://dx.doi.org/10.1007/978-3-642-27851-8_272-2.

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Lehmann, Ulrich. "Assimilation." In A Companion to Dada and Surrealism, 431–48. Hoboken, NJ: John Wiley & Sons, Inc, 2016. http://dx.doi.org/10.1002/9781118476215.ch26.

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Kibler, Jackie. "Assimilation." In Encyclopedia of Child Behavior and Development, 152. Boston, MA: Springer US, 2011. http://dx.doi.org/10.1007/978-0-387-79061-9_204.

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Bayar, Tuğba. "Assimilation." In The Palgrave Encyclopedia of Global Security Studies, 1–4. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-74336-3_165-1.

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Leibovici, Martine. "Assimilation." In Arendt-Handbuch, 330–31. Stuttgart: J.B. Metzler, 2022. http://dx.doi.org/10.1007/978-3-476-05837-9_72.

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Conference papers on the topic "Assimilation"

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Hardgrave, Bill, Deborah Armstrong, and Cynthia Riemenschneider. "RFID Assimilation Hierarchy." In 2007 40th Annual Hawaii International Conference on System Sciences (HICSS'07). IEEE, 2007. http://dx.doi.org/10.1109/hicss.2007.469.

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Vaidya, Kishor, A. S. M. Sajeev, and Junbin Gao. "E-procurement assimilation." In the 7th international conference. New York, New York, USA: ACM Press, 2005. http://dx.doi.org/10.1145/1089551.1089630.

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Evans, Brynn, and Stuart Card. "Augmented information assimilation." In Proceeding of the twenty-sixth annual CHI conference. New York, New York, USA: ACM Press, 2008. http://dx.doi.org/10.1145/1357054.1357207.

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Mallick, Swapan, Indira Rani S., Desamsetti Srinivas, and John P. George. "Assimilation of CrIS hyperspectral radiances in a 4D-Var assimilation system." In SPIE Asia-Pacific Remote Sensing, edited by Allen M. Larar, Prakash Chauhan, Makoto Suzuki, and Jianyu Wang. SPIE, 2016. http://dx.doi.org/10.1117/12.2222775.

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Turan, Adnan. "Comparing Assimilation Processes: Why Are Some Migrants More Vulnerable to Assimilation?" In 2021 AERA Annual Meeting. Washington DC: AERA, 2021. http://dx.doi.org/10.3102/1687463.

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Lu, Yang. "Assimilation among First-Generation Chinese Immigrants in 2010s: Not Adapting, but Assimilating." In 10th International Conference on Humanities, Psychology and Social Sciences. Acavent, 2020. http://dx.doi.org/10.33422/10th.hps.2020.03.69.

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Lu, Qifeng, Xuebao Wu, Peng Zhang, Songyan Gu, Chaohua Dong, Jiandong Gong, Xueshun Shen, Chenli Qi, and Gang Ma. "Assimilating FY-3A VASS data into Chinese 3Dvar assimilation system (Grapes 3Dvar)." In 2009 IEEE International Geoscience and Remote Sensing Symposium. IEEE, 2009. http://dx.doi.org/10.1109/igarss.2009.5418215.

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Suzuki, Shoko, and Takayuki Osogami. "Real-time data assimilation." In 2011 Winter Simulation Conference - (WSC 2011). IEEE, 2011. http://dx.doi.org/10.1109/wsc.2011.6147791.

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Penenko, A. V. "Sequential variational data assimilation." In SPIE Proceedings, edited by Gelii A. Zherebtsov and Gennadii G. Matvienko. SPIE, 2006. http://dx.doi.org/10.1117/12.675876.

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"INCONSISTENCY-TOLERANT KNOWLEDGE ASSIMILATION." In 2nd International Conference on Software and Data Technologies. SciTePress - Science and and Technology Publications, 2007. http://dx.doi.org/10.5220/0001331701980205.

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Reports on the topic "Assimilation"

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Wang, Ping, Tsz-Nga Wong, and Chong Yip. Mismatch and Assimilation. Cambridge, MA: National Bureau of Economic Research, August 2018. http://dx.doi.org/10.3386/w24960.

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Schunk, Robert W. Assimilation Ionosphere Model. Fort Belvoir, VA: Defense Technical Information Center, August 2002. http://dx.doi.org/10.21236/ada626262.

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Hernandez-Lasheras, Jaime, Ali Aydogdu, and Baptiste Mourre. Intercomparison of glider assimilation in the different analysis and forecasting systems. EuroSea, 2023. http://dx.doi.org/10.3289/eurosea_d4.9.

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The present deliverable is a continuation of deliverable D4.21, in which we presented the first steps in the design and preparation of different reanalysis simulations assimilating glider data. We here show the assessment and intercomparison of CMCC MedFS and SOCIB WMOP systems experiments. We have performed, for each system, three different experiments, running a one-year simulation during 2017. We compare a free-run simulation without data assimilation (FREE) and two reanalyses including assimilation: one considering only the generic data sources included in each operational system (NOGLID) and another one adding glider observations to the previous dataset (GLIDER). The models are assessed and inter compared to each other, focusing on the performance to represent the observed 3D structure of the ocean and on their capacity to recreate physical processes, as an anticyclonic eddy structure present in the Balearic sea. Results show how in both systems the use of glider observations can help to further improve the results obtained when using data assimilation, helping to an enhancement of the forecasting capabilities. (EuroSea Deliverable, D4.9)
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Bennett, Andrew F. Open Ocean Data Assimilation. Fort Belvoir, VA: Defense Technical Information Center, September 2001. http://dx.doi.org/10.21236/ada627701.

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Bennett, Andrew F. Open Ocean Data Assimilation. Fort Belvoir, VA: Defense Technical Information Center, September 2002. http://dx.doi.org/10.21236/ada629134.

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Bennett, Andrew F. Open Ocean Data Assimilation. Fort Belvoir, VA: Defense Technical Information Center, September 2002. http://dx.doi.org/10.21236/ada629176.

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Godinez Vazquez, Humberto C. Data Assimilation with GITM. Office of Scientific and Technical Information (OSTI), February 2013. http://dx.doi.org/10.2172/1062701.

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Cossarini, Gianpiero. Results of the BGC data assimilation. EuroSea, 2023. http://dx.doi.org/10.3289/eurosea_d4.10.

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This document presents the results of simulations that include glider profiles assimilation. Simulations are performed with the Marine Copernicus operational biogeochemical model system of the Mediterranean Sea. The deliverable shows that the assimilation of BGC-glider is feasible in the contest of biogeochemical operational systems and that it is built upon the experience of BGC-Argo float data assimilation. Different configuration of the assimilation of glider data have been tested to assess the impact of the physical and biogeochemical glider observations. The deliverable also describes the pre-processing activities of the BGC-glider data to provide qualified observations for the data assimilation and the cross validation of chlorophyll glider data with other sensors (ocean colour and BGC-Argo floats). Results of the simulations show that BGC-glider data assimilation, as already shown for BGC-Argo floats, provides complementary information with respect to Ocean Colour data (which is the only or the most commonly assimilated data in biogeochemical operational systems). Beside their relatively limited horizontal spatial impact, the assimilation of BGC profiles can constrain model simulations for relevant biogeochemical processes in specific periods (summer and transition periods) and layers (surface and subsurface). Results also highlight the importance of the assimilation modelling systems that can efficiently resolve the inconsistencies between chlorophyll observations of different sensors. (EuroSea Deliverable ; D4.10)
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Williams, Brian J. Data Assimilation - Advances and Applications. Office of Scientific and Technical Information (OSTI), July 2014. http://dx.doi.org/10.2172/1148964.

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Mariano, Arthur J., and Toshio M. Chin. Coastal and Ocean Data Assimilation. Fort Belvoir, VA: Defense Technical Information Center, September 2006. http://dx.doi.org/10.21236/ada612624.

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