scholarly journals The use of regression for assessing a seasonal forecast model experiment

2016 ◽  
Author(s):  
Rasmus E. Benestad ◽  
Retish Senan ◽  
Yvan Orsolini
Keyword(s):  
Sea Ice ◽  
Forecast Model ◽  
Seasonal Forecast ◽  
Ocean Model ◽  
Seasonal Forecasts ◽  
Model Set ◽  
Set Up ◽  
Numerical Model Experiments ◽  
The Tropics

Abstract. We demonstrate how factorial regression can be used to analyse numerical model experiments, testing the effect of different model settings. We analysed results from a coupled atmosphere-ocean model to explore how the different choices in the experimental set-up influence the seasonal predictions. These choices included a representation of the sea-ice and the choice of top of the atmosphere, and the results suggested that the simulated monthly mean temperatures poleward of the mid-latitudes are highly sensitivity to the specification of the top of the atmosphere, interpreted as the presence or absence of a stratosphere. The seasonal forecasts for the mid-to-high latitudes were also sensitive to whether the model set-up included a dynamic or non-dynamics sea-ice representation, although this effect was less important than the role of the stratosphere. The temperature in the tropics was insensitive to these choices.

scholarly journals The use of regression for assessing a seasonal forecast model experiment

2016 ◽  
Vol 7 (4) ◽  
pp. 851-861 ◽  
Author(s):  
Rasmus E. Benestad ◽  
Retish Senan ◽  
Yvan Orsolini
Keyword(s):  
Sea Ice ◽  
Forecast Model ◽  
Ocean Model ◽  
Seasonal Forecasts ◽  
Air Temperatures ◽  
Model Set ◽  
Set Up ◽  
Numerical Model Experiments ◽  
The Tropics

Abstract. We show how factorial regression can be used to analyse numerical model experiments, testing the effect of different model settings. We analysed results from a coupled atmosphere–ocean model to explore how the different choices in the experimental set-up influence the seasonal predictions. These choices included a representation of the sea ice and the height of top of the atmosphere, and the results suggested that the simulated monthly mean air temperatures poleward of the mid-latitudes were highly sensitivity to the specification of the top of the atmosphere, interpreted as the presence or absence of a stratosphere. The seasonal forecasts for the mid-latitudes to high latitudes were also sensitive to whether the model set-up included a dynamic or non-dynamic sea-ice representation, although this effect was somewhat less important than the role of the stratosphere. The air temperature in the tropics was insensitive to these choices.

scholarly journals Seasonal Forecast Skill of ENSO Teleconnection Maps

2020 ◽  
Vol 35 (6) ◽  
pp. 2387-2406
Author(s):  
Nathan J. L. Lenssen ◽  
Lisa Goddard ◽  
Simon Mason
Keyword(s):  
Missing Values ◽  
Southern Oscillation ◽  
Forecast Model ◽  
Seasonal Forecast ◽  
Quality Data ◽  
Seasonal Forecasts ◽  
Tropical Precipitation ◽  
Precipitation Anomalies ◽  
Additional Value ◽  
The Tropics

AbstractEl Niño–Southern Oscillation (ENSO) is the dominant source of seasonal climate predictability. This study quantifies the historical impact of ENSO on seasonal precipitation through an update of the global ENSO teleconnection maps of Mason and Goddard. Many additional teleconnections are detected due to better handling of missing values and 20 years of additional, higher quality data. These global teleconnection maps are used as deterministic and probabilistic empirical seasonal forecasts in a verification study. The probabilistic empirical forecast model outperforms climatology in the tropics demonstrating the value of a forecast derived from the expected precipitation anomalies given the ENSO phase. Incorporating uncertainty due to SST prediction shows that teleconnection maps are skillful in predicting tropical precipitation up to a lead time of 4 months. The historical IRI seasonal forecasts generally outperform the empirical forecasts made with the teleconnection maps, demonstrating the additional value of state-of-the-art dynamical-based seasonal forecast systems. Additionally, the probabilistic empirical seasonal forecasts are proposed as reference forecasts for future skill assessments of real-time seasonal forecast systems.

Role of river stage in characterization of phreatic line

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Vikram Kumar ◽  
Srivastava Granthi
Keyword(s):  
Irrigation Planning ◽  
Content Type ◽  
Measured Distance ◽  
Model Set ◽  
Downstream Section ◽  
Large Water ◽  
Set Up ◽  
Observation Wells

Purpose The purpose of this study is to understand the basics of interactions of groundwater and surface water, which is needed for effective management of water resources. Design/methodology/approach The experimental setup was framed using curved flume and the straight flume, which simulates the model of river and groundwater storage, respectively. The model set up further consists, downstream, central and upstream sections where 14 observation wells, which are arranged at a measured distance from the canal side. Findings Exit gradient is higher at downstream when the average head differences between canal and river are 31.9 cm and 35.7 cm. Free seepage height is more in the downstream wells than upstream and central wells. At the downstream section, there is a greater chance of instability of the riverbank. Research limitations/implications Results will be used for better planning of hydraulic structural design. Practical implications Results will help in storing the large water and better irrigation planning for the water acute states and locations. Originality/value The originality is own developed physical model and its own first type to understand the basic of interaction and effects.

scholarly journals An Analytical Framework for Understanding Tropical Meridional Modes

2017 ◽  
Vol 30 (9) ◽  
pp. 3303-3323 ◽  
Author(s):  
Cristian Martinez-Villalobos ◽  
Daniel J. Vimont
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Ocean Model ◽  
Sea Surface ◽  
Transient Growth ◽  
Kelvin Wave ◽  
Wes Feedback ◽  
Meridional Mode ◽  
The Tropics

A theoretical framework is developed for understanding the transient growth and propagation characteristics of thermodynamically coupled, meridional mode–like structures in the tropics. The model consists of a Gill–Matsuno-type steady atmosphere under the long-wave approximation coupled via a wind–evaporation–sea surface temperature (WES) feedback to a “slab” ocean model. When projected onto meridional basis functions for the atmosphere the system simplifies to a nonnormal set of equations that describes the evolution of individual sea surface temperature (SST) modes, with clean separation between equatorially symmetric and antisymmetric modes. The following major findings result from analysis of the system: 1) a transient growth process exists whereby specific SST modes propagate toward lower-order modes at the expense of the higher-order modes; 2) the same dynamical mechanisms govern the evolution of symmetric and antisymmetric SST modes except for the lowest-order wavenumber, where for symmetric structures the atmospheric Kelvin wave plays a critically different role in enhancing decay; and 3) the WES feedback is positive for all modes (with a maximum for the most equatorially confined antisymmetric structure) except for the most equatorially confined symmetric mode where the Kelvin wave generates a negative WES feedback. Taken together, these findings explain why equatorially antisymmetric “dipole”-like structures may dominate thermodynamically coupled ocean–atmosphere variability in the tropics. The role of nonnormality and the role of realistic mean states in meridional mode variability are discussed.

scholarly journals Runoff Forecasting and Its Application in Reservoir Operation and Flood Warnings in Nepal

2014 ◽  
Vol 15 ◽  
pp. 23-29
Author(s):  
Anup Khanal ◽  
Netra Prasad Timalsina ◽  
Knut Alfredsen
Keyword(s):  
Reservoir Operation ◽  
Weather Forecast ◽  
Forecast Model ◽  
Developed Countries ◽  
Runoff Forecasting ◽  
Model Set ◽  
Runoff Forecast ◽  
Set Up ◽  
Hbv Model ◽  
Flood Warnings

Runoff forecasting is a very useful tool in hydrology to predict runoff based on a weather forecast. In developed countries, the method is also currently used for flood forecasting, and to predict runoff for hydropower reservoirs and water allocation for irrigation. But this is not the case in Nepal. The purpose of this paper is to demonstrate how to set up a system for runoff forecasting for a Nepalese catchment and illustrate how these procedures could be utilized in reservoir operation and flood warnings. This paper provides the necessary steps for implementing such a system in Nepal, including the selection of a meteorological forecast model, bias correction of the model output, HBV model set up, and runoff forecast simulation.DOI: http://dx.doi.org/10.3126/hn.v15i0.11288HYDRO Nepal JournalJournal of Water Energy and EnvironmentVolume: 15, 2014 JulyPage: 23-29

Assessing reasons for skilful predictions of winter windstorms over the Atlantic/European region

2020 ◽  
Author(s):  
Lisa Degenhardt ◽  
Gregor Leckebusch ◽  
Adam Scaife
Keyword(s):  
Large Scale ◽  
Surface Wind ◽  
Forecast Model ◽  
Surface Wind Speed ◽  
Seasonal Forecast ◽  
Forecast Skill ◽  
Seasonal Forecasts ◽  
Financial Industry ◽  
Near Surface ◽  
Skill Scores

<p>Severe Atlantic winter storms are affecting densely populated regions of Europe (e.g. UK, France, Germany, etc.). Consequently, different parts of the society, financial industry (e.g., insurance) and last but not least the general public are interested in skilful forecasts for the upcoming storm season (usually December to March). To allow for a best possible use of steadily improved seasonal forecasts, the understanding which factors contribute to realise forecast skill is essential and will allow for an assessment whether to expect a forecast to be skilful or not.</p><p>This study analyses the predictability of the seasonal forecast model of the UK MetOffice, the GloSea5. Windstorm events are identified and tracked following Leckebusch et al. (2008) via the exceedance of the 98<sup>th</sup> percentile of the near surface wind speed.</p><p>Seasonal predictability of windstorm frequency in comparison to observations (based e.g., on ERA5 reanalysis) are calculated and different statistical methods (skill scores) are compared.</p><p>Large scale patterns (e.g., NAO, AO, EAWR, etc.) and dynamical factors (e.g., Eady Growth Rate) are analysed and their predictability is assessed in comparison to storm frequency forecast skill. This will lead to an idea how the forecast skill of windstorms is depending on the forecast skill of forcing factors conditional to the phase of large-scale variability modes. Thus, we deduce information, which factors are most important to generate seasonal forecast skill for severe extra-tropical windstorms.</p><p>The results can be used to get a better understanding of the resulting skill for the upcoming windstorm season.</p>

scholarly journals Estimating Zonal Ekman Transport along Coastal Senegal during Passage of Hurricane Fred (2015) from August 30 to 31, 2015

2019 ◽  
Author(s):  
Abdou Lahat Dieng ◽  
Siny Ndoye ◽  
Gregory S. Jenkins ◽  
Saïdou Moustapha Sall ◽  
Amadou Thierno Gaye
Keyword(s):  
Forecast Model ◽  
Ocean Model ◽  
Coastal Communities ◽  
Ekman Transport ◽  
Southerly Wind ◽  
Wind Speeds ◽  
Meridional Winds ◽  
Observed Damage ◽  
Coastal Damage

We examine the role of zonal Ekman transport along the coast of Senegal on 30 August, 2015 when the tropical disturbance associated with Tropical Cyclone Fred was located to the west of Senegal causing considerable coastal damage to coastal areas south of Dakar, Senegal. Ten-meter winds from three Weather Research and Forecast model simulations were used to estimate zonal Ekman transport, with the largest values found during the 30 August. The simulations are in agreement with limited coastal observations showing increasing southerly wind speeds during 30 August but are overestimated relative to the 3 coastal stations. The strong meridional winds translate into increased zonal Ekman transport to the coast of Senegal on 30 August. The use of a coupled ocean model will improve the estimates of Ekman transport along the Guinea-Senegalese coast. The observed damage suggests that artificial and natural barriers (mangroves) should be strengthened to protect coastal communities in Senegal.

scholarly journals Simultaneous Parameter Optimization of an Arctic Sea Ice–Ocean Model by a Genetic Algorithm

2019 ◽  
Vol 147 (6) ◽  
pp. 1899-1926 ◽  
Author(s):  
Hiroshi Sumata ◽  
Frank Kauker ◽  
Michael Karcher ◽  
Rüdiger Gerdes
Keyword(s):  
Genetic Algorithm ◽  
Sea Ice ◽  
Cost Function ◽  
Parameter Optimization ◽  
North Atlantic Ocean ◽  
Current Model ◽  
Ocean Model ◽  
Arctic Sea Ice ◽  
Model Parameters ◽  
Set Up

AbstractImprovement and optimization of numerical sea ice models are of great relevance for understanding the role of sea ice in the climate system. They are also a prerequisite for meaningful prediction. To improve the simulated sea ice properties, we develop an objective parameter optimization system for a coupled sea ice–ocean model based on a genetic algorithm. To take the interrelation of dynamic and thermodynamic model parameters into account, the system is set up to optimize 15 model parameters simultaneously. The optimization is minimizing a cost function composed of the model–observation misfit of three sea ice quantities (concentration, drift, and thickness). The system is applied for a domain covering the entire Arctic and northern North Atlantic Ocean with an optimization window of about two decades (1990–2012). It successfully improves the simulated sea ice properties not only during the period of optimization but also in a validation period (2013–16). The similarity of the final values of the cost function and the resulting sea ice fields from a set of 11 independent optimizations suggest that the obtained sea ice fields are close to the best possible achievable by the current model setup, which allows us to identify limitations of the model formulation. The optimized parameters are applied for a simulation with a higher-resolution model to examine a portability of the parameters. The result shows good portability, while at the same time, it shows the importance of the oceanic conditions for the portability.

scholarly journals River Freshwater Contribution in Operational Ocean Models along the European Atlantic Façade: Impact of a New River Discharge Forcing Data on the CMEMS IBI Regional Model Solution

2021 ◽  
Vol 9 (4) ◽  
pp. 401
Author(s):  
Marcos G. Sotillo ◽  
Francisco Campuzano ◽  
Karen Guihou ◽  
Pablo Lorente ◽  
Estrella Olmedo ◽  
...  
Keyword(s):  
River Discharge ◽  
Ocean Model ◽  
Salinity Field ◽  
Freshwater Forcing ◽  
Salinity Variability ◽  
Regional Ocean Model ◽  
Model Set ◽  
Set Up ◽  
Marine Environment Monitoring ◽  
Monitoring Service

River freshwater contribution in the European Atlantic margin and its influence on the sea salinity field are analyzed. The impacts of using a new river discharge database as part of the freshwater forcing in a regional ocean model are assessed. Ocean model scenarios, based on the CMEMS (Copernicus Marine Environment Monitoring Service) operational IBI-MFC (Iberia Biscay Ireland Monitoring Forecasting Centre) model set-up, are run to test different (observed, modeled and climatological) river and coastal freshwater forcing configurations throughout 2018. The modelled salinity fields are validated, using as a reference all known available in-situ observational data sources. The IBI model application is proven to adequately simulate the regional salinity, and the scenarios showcase the effects of varying imposed river outflows. Some model improvement is achieved using the new forcing (i.e., better capture of salinity variability and more realistic simulation of baroclinic frontal structures linked to coastal and river freshwater buoyancy plumes). Major impacts are identified in areas with bigger river discharges (i.e., the French shelf or the northwestern Iberian coast). Instead, the Portuguese shelf or the Gulf of Cadiz are less impacted by changes in the imposed river inflows, and other dynamical factors in these areas play a major role in the configuration of the regional salinity.

scholarly journals Estimating zonal Ekman transport along coastal Senegal during passage of Hurricane Fred, 30–31 August 2015

2021 ◽  
Vol 3 (5) ◽  
Author(s):  
Abdou Lahat Dieng ◽  
Siny Ndoye ◽  
Gregory S. Jenkins ◽  
Saïdou M. Sall ◽  
Amadou T. Gaye
Keyword(s):  
Forecast Model ◽  
Ocean Model ◽  
Ekman Transport ◽  
Southerly Wind ◽  
Wind Speeds ◽  
Meridional Winds ◽  
Water Level Variations ◽  
Observed Damage ◽  
Coastal Damage

AbstractWe examine the role of zonal Ekman transport along the coast of Senegal on 30 August 2015 when the tropical disturbance associated with Tropical Cyclone Fred was located to the west of Senegal, causing considerable coastal damage in the southern Senegal–Gambia domain (south of Dakar, Senegal). Ten-meter winds from three Weather Research and Forecast model simulations were used to estimate zonal Ekman transport, when the maximum values were found on 30 August. These simulations are in agreement with limited coastal observations showing increasing southerly wind speeds during 30 August but overestimated relative to the three coastal stations. The strong meridional winds translate into increased zonal Ekman transport to the coast of Senegal on 30 August and are likely responsible for some coastal flooding. Ekman transport along the coast contributes significantly to the water-level variations during swell events. The use of a coupled ocean model will improve the estimates of Ekman transport along the Guinea-Senegalese coast. The observed damage suggests that artificial and natural barriers (mangroves) should be strengthened to protect coastal communities in Senegal.

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