scholarly journals Assimilation of GPSRO Bending Angle Profiles into the Brazilian Global Atmospheric Model

2019 ◽  
Vol 11 (3) ◽  
pp. 256 ◽  
Author(s):  
Ivette Banos ◽  
Luiz Sapucci ◽  
Lidia Cucurull ◽  
Carlos Bastarz ◽  
Bruna Silveira
Keyword(s):  
Data Assimilation ◽  
Weather Forecast ◽  
Atmospheric Model ◽  
Meridional Wind ◽  
Point Of View ◽  
Bending Angle ◽  
Global Atmospheric Model ◽  
Angle Data ◽  
Meteorological Systems ◽  
Bending Angles

The Global Positioning System (GPS) Radio Occultation (RO) technique allows valuable information to be obtained about the state of the atmosphere through vertical profiles obtained at various processing levels. From the point of view of data assimilation, there is a consensus that less processed data are preferable because of their lowest addition of uncertainties in the process. In the GPSRO context, bending angle data are better to assimilate than refractivity or atmospheric profiles; however, these data have not been properly explored by data assimilation at the CPTEC (acronym in Portuguese for Center for Weather Forecast and Climate Studies). In this study, the benefits and possible deficiencies of the CPTEC modeling system for this data source are investigated. Three numerical experiments were conducted, assimilating bending angles and refractivity profiles in the Gridpoint Statistical Interpolation (GSI) system coupled with the Brazilian Global Atmospheric Model (BAM). The results highlighted the need for further studies to explore the representation of meteorological systems at the higher levels of the BAM model. Nevertheless, more benefits were achieved using bending angle data compared with the results obtained assimilating refractivity profiles. The highest gain was in the data usage exploring 73.4% of the potential of the RO technique when bending angles are assimilated. Additionally, gains of 3.5% and 2.5% were found in the root mean square error values in the zonal and meridional wind components and geopotencial height at 250 hPa, respectively.

On the initial conditions of the ICON-D2-EPS ensemble: An analysis in terms of spread and skill.

2020 ◽  
Author(s):  
Chiara Marsigli
Keyword(s):  
Data Assimilation ◽  
Initial Conditions ◽  
Weather Forecast ◽  
Point Of View ◽  
Ensemble Forecasting ◽  
Limited Area ◽  
Initial Condition ◽  
Weather Situation ◽  
Operational Phase ◽  
Data Assimilation System

<p><span>The COSMO-D2-EPS ensemble is running operationally at DWD at a resolution of 2.2 km. In the framework of the transition from the COSMO to the ICON model for the limited-area applications, the ICON-D2-EPS ensemble is starting its pre-operational phase. Therefore, the perturbation strategy developed for COSMO-D2-EPS is adapted to the new ensemble.</span><br><span>In this work, the focus is on the initial conditions, which are provided by the first 20 analyses generated by a LETKF ensemble data assimilation system (KENDA).</span><br><span>The KENDA analyses present the advantage of providing perturbed initial conditions to the convection-permitting ensemble, where the perturbations contain also the information on the convection-permitting scale uncertainties. On the other hand, the KENDA analyses are optimised for </span><span>the purpose of data assimilation. The ensemble of analyses which is the most suitable for initialising the next data assimilation cycle may not be the same which is the most suitable for initialising the weather forecast ensemble, e.g. in terms of spread.</span></p><p><span>The analyses generated by the KENDA cycle are evaluated from the point of view of their usage for ensemble forecasting initialisation. Their spread is computed for different variables, assessing also how it varies with the spatial scale and with the weather situation. Furthermore, the spread is compared to the error of the analyses and of the forecasts, in order to assess the ability of the analyses to describe the initial condition uncertainty. </span><br><span>The growth of the differences between the members during the first hours of the forecasts is studied as well, in dependence on the weather situation.</span></p><p><span>The final aim of this work is to identify possible improvements for deriving the ensemble initial conditions from the KENDA analyses.</span></p>

scholarly journals Vorticity-Divergence semi-Lagrangian Global Atmospheric Model SL-AV20: Dynamical Core

2016 ◽  
Author(s):  
Mikhail Tolstykh ◽  
Vladimir Shashkin ◽  
Rostislav Fadeev ◽  
Gordey Goyman
Keyword(s):  
Numerical Solutions ◽  
Climate Modeling ◽  
Region Of Interest ◽  
Weather Forecast ◽  
Seasonal Prediction ◽  
Atmospheric Model ◽  
Medium Range Weather Forecast ◽  
Variable Resolution ◽  
Dynamical Core ◽  
Global Atmospheric Model

Abstract. SL-AV (Semi-Lagranginan Absolute Vorticity) is a global atmospheric model. Its latest version SL-AV20 provides global operational medium-range weather forecast with 20 km resolution over Russia. The lower resolution configurations of SL-AV20 are being tested for seasonal prediction and climate modeling. The article presents the model dynamical core. Its main features are vorticity-divergence formulation at the unstaggered grid, high-order finite-difference approximations, semi-Lagrangian semi-implicit discretization and the reduced latitude-longitude grid with variable resolution in latitude. The accuracy of SL-AV20 numerical solutions using reduced lat-lon grid and the variable resolution in latitude is tested with two idealized testcases. The results agree well with other published model solutions. It is shown that the use of the reduced grid having up to 25 % less grid points than the regular grid does not significantly affect the accuracy. Variable resolution in latitude allows to improve the accuracy of solution in the region of interest.

scholarly journals Limits, Variability, and General Behavior of Statistical Predictability of the Midlatitude Atmosphere

2008 ◽  
Vol 65 (1) ◽  
pp. 263-275 ◽  
Author(s):  
Richard Kleeman
Keyword(s):  
Initial Conditions ◽  
Storm Track ◽  
Weather Forecast ◽  
Atmospheric Model ◽  
Horizontal Resolution ◽  
Statistical Prediction ◽  
Ensemble Spread ◽  
Winter Storm ◽  
Global Atmospheric Model ◽  
Summer Storm

Abstract The nature of statistical predictability is analyzed in a T42 global atmospheric model that is able to adequately capture the main features of the midlatitude atmosphere. Key novel features of the present study include very large prediction ensembles and information theoretic techniques. It is found globally that predictability declines in a quasi-linear fashion with time for short-term predictions (3–25 days), while for long ranges (30–45 days) there is an exponential tail. In general, beyond 45 days the prediction and climatological ensembles have essentially converged, which means that beyond that point, atmospheric initial conditions are irrelevant to atmospheric statistical prediction. Regional predictions show considerable variation in behavior. Both of the (northern) winter storm-track regions show a close-to-quasi-linear decline in predictability toward a cutoff at around 40 days. The (southern) summer storm track shows a much more exponential and considerably slower decline with a small amount of predictability still in evidence even at 90 days. Because the winter storm tracks dominate global variance the behavior of their predictability tends to dominate the global measure, except at longer lags. Variability in predictability with respect to initial conditions is also examined, and it is found that this is related more strongly to ensemble signal rather than ensemble spread. This result may serve to explain why the relation between weather forecast skill and ensemble spread is often observed to be significantly less than perfect. Results herein suggest that the ensemble signal as well as spread variations may be a major contributor to skill variations. Finally, it is found that the sensitivity of the calculated global predictability to changes in model horizontal resolution is not large; results from a T85 resolution model are not qualitatively all that different from the T42 case.

Impact of GNSS radio occultation bending angle data assimilation in YH4DVAR system

2014 ◽  
Vol 23 (6) ◽  
pp. 069202
Author(s):  
Meng-Bin Zhu ◽  
Wei-Min Zhang ◽  
Xiao-Qun Cao ◽  
Yi Yu
Keyword(s):  
Data Assimilation ◽  
Radio Occultation ◽  
Bending Angle ◽  
Angle Data

scholarly journals Derivation of the Water Vapor Content from the GNSS Radio Occultations Observations

2006 ◽  
Vol 23 (7) ◽  
pp. 936-943 ◽  
Author(s):  
Francesco Vespe ◽  
Teresa Persia
Keyword(s):  
External Information ◽  
Mathematical Treatment ◽  
Low Latitude ◽  
Bending Angle ◽  
Ground Pressure ◽  
Pressure Profiles ◽  
Angle Data ◽  
The Relationship ◽  
Humidity Profiles ◽  
Bending Angles

Abstract The present work investigates the possibility of retrieving humidity using the bending angle data obtained from radio occultation of GPS signals without additional external information. In particular, with the proposed approach, the dry pressure profiles are obtained by fitting the bending angles of the outer-troposphere layers (from h = h250K up to the stratopause) using the Hopfield dry atmosphere model. The ground pressure and temperature are the parameters of the model to be estimated. In the second step the humidity profiles are extracted by subtracting the contribution resulting from the dry atmosphere from the measured bending angles. Such derivation implies a complex mathematical treatment of the relationship between the bending angle and the refractivity, which is fully explained herein. Furthermore, the method was applied on Challenging Minisatellite Payload (CHAMP) profiles. The CHAMP profiles are achieved by applying heuristic retrieval algorithms based on the canonical transform. The algorithms are applied to minimize the negative refractivity bias that is observed for low-latitude GNSS RO. Thus, the results are shown and discussed in the second part of the paper. Finally, it is widely discussed how the proposed method is able to retrieve refractivity profiles without using the Abel inversion.

scholarly journals Dynamical Heating of the Arctic Atmosphere during the Springtime Transition

2017 ◽  
Vol 30 (23) ◽  
pp. 9539-9553 ◽  
Author(s):  
Xiaoyu Long ◽  
Walter A. Robinson
Keyword(s):  
Baroclinic Instability ◽  
Stationary Wave ◽  
Atmospheric Model ◽  
Meridional Wind ◽  
Early Spring ◽  
Heat Fluxes ◽  
The Arctic ◽  
Global Atmospheric Model ◽  
Eddy Heat Flux ◽  
Arctic Atmosphere

The Arctic undergoes an abrupt transition from the quasi-steady climate of winter to a period of rapid warming in spring. To explore the atmospheric dynamics of this transition, an extended simulation using a global atmospheric model driven by a fixed repeating annual cycle of sea surface temperatures and sea ice cover is analyzed. The model reproduces the timing, structure, and interannual variability of the observed spring onset, thus providing a platform for addressing its dynamics. It is found that atmospheric eddy heat fluxes across the Arctic boundary, highly variable in winter but much less so in spring, shape the transition and determine its timing. Together with the rapid springtime increase of solar heating, the decreased variability in dynamical heating creates the abrupt appearance of the spring transition. Perpetual season simulations for winter, early spring, and late spring further reveal the dynamics of seasonally varying dynamical heating. The eddy heat flux is less variable in spring than winter because the variance of the eddy meridional wind and the stationary wave in temperature, resulting from land–sea contrast, both weaken. Further analysis shows that the strong wintertime variance in meridional wind is associated with traveling planetary wavenumber 1, which amplifies when its phase corresponds to an east–west dipole spanning the Greenland Sea. In this configuration the transient wind–stationary thermal interaction releases zonal available potential energy into wavenumber 1. Thus the highly variable wintertime dynamical heating of the Arctic arises from a baroclinic mechanism, but one distinct from baroclinic instability or cyclogenesis.

scholarly journals A Flexible Two-Sensor System for Temperature and Bending Angle Monitoring

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2962
Author(s):  
Yifeng Mu ◽  
Rou Feng ◽  
Qibei Gong ◽  
Yuxuan Liu ◽  
Xijun Jiang ◽  
...  
Keyword(s):  
Electronic System ◽  
Disease Diagnosis ◽  
Accurate Information ◽  
Polyimide Films ◽  
Bending Angle ◽  
Multiple Sensors ◽  
Constituent Material ◽  
Application Potential ◽  
Wearable Electronic ◽  
Bending Angles

A wearable electronic system constructed with multiple sensors with different functions to obtain multidimensional information is essential for making accurate assessments of a person’s condition, which is especially beneficial for applications in the areas of health monitoring, clinical diagnosis, and therapy. In this work, using polyimide films as substrates and Pt as the constituent material of serpentine structures, flexible temperature and angle sensors were designed that can be attached to the surface of an object or the human body for monitoring purposes. In these sensors, changes in temperature and bending angle are converted into variations in resistance through thermal resistance and strain effects with a sensitivity of 0.00204/°C for temperatures in the range of 25 to 100 °C and a sensitivity of 0.00015/° for bending angles in the range of 0° to 150°. With an appropriate layout design, two sensors were integrated to measure temperature and bending angles simultaneously in order to obtain decoupled, compensated, and more accurate information of temperature and angle. Finally, the system was tested by being attached to the surface of a knee joint, demonstrating its application potential in disease diagnosis, such as in arthritis assessment.

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