Spectral nudging

Spectral nudging

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Spectral nudging, a dynamic downscaling method, has been used as a suitable spectral nudging approach spectral nudging to force a regional model to adopt prescribed large-scales over the entire domain, not just at the lateral boundaries, while developing realistic detailed regional features consistent with the large-scales. For spectral nudging, same nudging strategy is used within PBL to keep the simulation consistent with grid nudg- ing, and above PBL, geopotential field is nudged, instead of. WRF experiments confirm this for higher order downscaling types (Types III and IV). Key words Spectral nudging SSBC regional spectral nudging climate modeling CORDEX Asian monsoon. Strong nudging spectral nudging may reduce or filter out extreme events since nudging pushes the model toward a relatively smooth, large-scale state. Section 4 briefly discusses the spectral nudging procedure and shows results for the same experiments as in Section 3 but with the spectral nudging activated. This constrains the evolution in certain scales, typically the synoptic ones, while allowing the others to evolve freely. " Proceedings of the ASME 38th International Conference on Ocean, Offshore and Arctic Engineering.

The spectral nudging nudging technique can be used to balance the performance of dynamical downscaling at large and small scales, but the performances of the two nudging techniques (analysis nudging and spectral nudging) are debated. Miguez‐Macho spectral nudging et al. The boundaries of the 5-km nest are indicated as a black line in (a). The impact of physic parameterizations is not as influential as spectral nudging. This bias disappears when spectral nudging is applied. In this study, different nudging configurations are tested for an intense South spectral nudging Atlantic Convergence Zone (SACZ) event. In this study, the impact of the spectral nudging method on regional climate simulation over the Coordinated Regional Climate Downscaling Experiment East Asia (CORDEX-EA) region is investigated using the Weather Research and Forecasting model (WRF).

Spectral nudging improves the analysis-driven simulation results significantly. Furthermore, they show that neither the use of the spectral nudging nor the choice of a small domain are detrimental to the modelling of heavy precipitation in the present experiment. These scales normally encompass spectral nudging large weather phenomena which are well resolved in the forcing data, such as Rossby waves, large pressure systems, or trade winds. Spectral nudging allows forcing a selected part of the spectrum of a model&39;s solution with the equivalent part in a reference dataset, such as an analysis, reanalysis or another model. The “spectral nudging” method imposes time-variable large-scale atmospheric states on a regional atmospheric model. Summer is the rainy season in China.

Large-scale forcing is still crucial for dynamical downscaling. , ) – in the Weather Research and Forecasting (WRF) model has been widely used, and its application significantly improves the prediction spectral nudging of atmospheric circulation and precipitation forecasts (Zhao et al. Kodaira, T, Bernier, N, & Thompson, KR. The aim of this study is to compare a global spectral climate model at high resolution (50 km) and a. proposed a spectral nudging technique to solve the problem of the distortion of the large scale dynamics by interaction with the boundaries, and therefore allow the use of relatively large domains for dynamical downscaling applications. Abstract In this study, by using spectral nudging the Weather Research and Forecasting (WRF) model, the impact of spectral nudging (SN) on simulating the precipitation extremes and diurnal cycle of precipitation.

The following variables are also listed under spectral nudging: k_zfac_uv = 0 (model level below which nudging is switched off for water uv) dk_zfac_uv = 0 (depth in *k* between k_zfac_uv to dk_zfac_uv where nudging increases linearly to full strength). 17 nudging is not applied directly, while spectral nudging mainly a ects longer wavenumbers. However, spectral nudging spectral nudging is sensitive to nudging parameters, and most related research has typically adopted the default nudging schemes. Precipitation and 2-m temperature were analyzed to determine how changing spectral nudging strength. spectral nudging detrimental impact of spectral nudging spectral nudging is a slight precipitation increase in the upper quantiles of precipitation, which can be resolved by large-scale nudging of specific humidity.

Spectral nudging is an important method of spectral nudging improving the effectiveness of dynamical downscaling in the Weather Research and Forecasting model (WRF). It is based on the idea that regional-scale climate statistics are conditioned by the interplay between continental-scale atmospheric conditions and such regional features as marginal seas and mountain ranges. Topography maps spectral nudging for the (a) 15- and (b) 5-km domains. The state-of-the-art regional climate model CCLM is applied in a hindcast-mode to the case of individual Vb-events in August and Mai/June. The reduction of this nudging factor in the lower troposphere allows the ageostrophic component of wind to spectral nudging develop as in nature, which leads to the improvement of precipitation. The results show that the regional model driven only at its lateral boundaries presents a summer warm bias in the middle of the domain. Spectral nudging is a technique which can ameliorate this issue by providing large‐scale forcing in the regional model interior.

"Application of the Spectral Nudging on Global Tides Towards a Global Total Water Level Prediction System. Results spectral nudging are consistent with previous studies regarding the seasonal‐mean fields. The spectral nudging technique consists of adding an additional re-laxation term to the prognostic equations for the spec-tral coefficients. For the large‐scale circulation, spectral spectral nudging nudging spectral nudging (SN) – a scale‐selective interior constraint technique (Storch et al. Spectral Nudging is a new upper-air nudging option since Version 3.

Spectral nudging has also been applied successfully to RCM studies for Southeast Asia (Cha et al, Song et al, Yhang and Hong, Tang et al, Cha and Lee, Feser and von Storch a, b). What remains to be shown is the effect that spectral nudging has on typhoon formation and associated spectral nudging large-scale circulation patterns. Besides the conventional forcing of the regional climate model at its lateral boundaries a spectral nudging technique is applied. Two periods were simulated, one in a cold season (January ) and one in a warm season (July ). MAY VINCENT AND HAHMANN 1023. More Spectral Nudging images. Two time periods were selected under the category of short. In this study, spectral nudging was applied to tropical cyclone (TC) track and intensity forecasts, and its effects were investigated using a high‐resolution spectral nudging regional model.

Spectral nudging is a technique consisting in driving regional climate models (RCMs) on selected spatial scales corresponding to those produced by the driv- ing global circulation model (GCM). 2 Spectral nudging Spectral nudging extends the Newtonian relaxation method by taking the correction spectral nudging term and applying a spectral (low-pass) filter so that large spatial wavelengths are adjusted while smaller wavelengths are left essentially unperturbed. Sensitivity experiments testing two scale-selective bias correction (SSBC) methods spectral nudging have been carried out to identify an optimal spectral nudging scheme for historical dynamically downscaled simulations of South Asia, using the coordinated regional climate downscaling spectral nudging experiment (CORDEX) protocol and the regional spectral model (RSM). Spectral Nudging to Improve Climate Downscaling over North America Using the Regional Atmospheric Modeling System (RAMS) Gonzalo Miguez-Macho, spectral nudging Georgiy L. The wave numbers defined here are the number of waves contained in spectral nudging the domain, and the number is the maximum one that is nudged. , ; Miguez‐Macho et al.

Spectral nudging to eliminate the effects of domain position and geometry in regional climate model simulations Gonzalo Miguez-Macho, Georgiy L. Following this “downscaling” idea, the regional model is. Driven by spectral nudging the ERA-Interim reanalysis, five continuous simulations covering 1989– are conducted by the WRF model, in which four runs adopt. Section 5 examines the small-scale variability created by the model when the long waves are nudged, and compares results to conventional nudging techniques in the interior of the domain. This technique prevents large and unrealistic.

However, such control over model behavior raises concerns over how much nudging may affect unforced variability and extremes. Stenchikov, and Alan Robock in JGR,, this is how I understand it:. •Spectral nudging yields less reduction in added variability spectral nudging of the smaller scales than grid nudging and is therefore the preferred approach in RCM dynamic downscaling.

The spectral nudging technique Spectral nudging minimizes deviations of a weather or climate model from a reference reanalysis or observation data set at selected large spatial spectral nudging scales. The method chosen to do this is based onThatcher and Mc-. On the inner, 5 km domain,. LONG-G 11 days 24h Grid nudging LONG-S 11 days 24h Spectral nudging FIG. The spectral nudging method is applied in order to achieve a better representation of large‐scale climate over a limited domain. The “spectral nudging” method imposes time-variable large-scale atmospheric states on a regional atmospheric model. Stenchikov, and Alan Robock spectral nudging Department of Environmental Sciences, Rutgers University, New Brunswick, NJ 08901 Submitted to Journal of Climate October, Corresponding author address:. The spectral nudging scheme is benchmarked against a Newtonian relaxation method, nudging winds and air temperature towards ERA-Interim spectral nudging reanalyses.

This option also nudges geopotential height. Spectral nudging applications are particularly useful since they also provide the ability to maintain higher temporal and spatial variability in the simulations results. We find that the convolution approach can produce results that are competitive with Newtonian relaxation in both the effectiveness and efficiency of the scheme, while giving the added flexibility of. The question then becomes. 18 Maps of mesoscale variance show spatial smoothing for both grid and spectral nudging, 19 although the e ect is less pronounced for spectral nudging. model (WRF) with varying spectral nudging strength, using WRF’s standard nudging as a reference point. Spectral (interior) nudging is a way of constraining a model to be more consistent with spectral nudging observed behavior.

This selectively nudges the coarser scales only, but is otherwise set up the same way as grid-nudging. valued amplitude X(h, t) for each spectral coefficient of a meteorological variable to be nudged. These equations take the following form in spectral space: ›Xm n (h,t) spectral nudging ›t 5Fm n (h,t)1Gm (h)Xm(reana.

Spectral nudging

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