Seasonal predictability of the 2010 Russian heat wave

The atmospheric blocking over eastern Europe and western Russia that prevailed during July and August of 2010 led to the development of a devastating Russian heat wave. Therefore the question of whether the event was predictable or not is highly important. The principal aim of this study is to examine the predictability of this high-impact atmospheric event on a seasonal timescale. To this end, a set of dynamical seasonal simulations have been carried out using an atmospheric global circulation model (AGCM). The impact of various model initializations on the predictability of this large-scale event and its sensitivity to the initial conditions has been also investigated. The ensemble seasonal simulations are based on a modified version of the lagged-average forecast method using different lead-time initializations of the model. The results indicated that only a few individual members reproduced the main features of the blocking system 3 months ahead. Most members missed the phase space and the propagation of the system, setting limitations in the predictability of the event

A 2-year intercomparison of the WAM-Cycle4 and the WAVEWATCH-III wave models implemented within the Mediterranean Sea

In this work we present the implementation of a wave forecast/hindcast system for the Mediterranean Sea at a 1/10º horizontal resolution and we show a first assessment of its performance by inter-comparing model results to observational data time series at selected points for the period 2000-2001. The system which is part of the POSEIDON-II operational system includes the WAM – Cycle4 and the WAVEWATCH-III wave forecast models (implemented within the same region) one way coupled with the non-hydrostatic version of the ETA atmospheric model which provides at 3-hour intervals the necessary wind velocity fields to the wave models. The same system but based on the WAM-Cycle4 wave model, has been used in the past for the production of the Aegean Sea wind and wave Atlas. Overall, the inter-comparison shows that both wave models are rather skilful in predicting the integral wave parameters with significant wave height skill scores in the range 0.85-0.90 and mean period scores in the range 0.77-0.83. It is also evident that WAM model has a tendency to overestimate mean wave periods while the opposite is true for WAVEWATCH-III model. Differences between the two models simulated spectra exist along the main passage of cyclonic systems over the Mediterranean Sea while in the wind seas dominated areas of the basin (the Aegean Sea for example) the two models show almost the same behavior

Latest LAPS developments Assimilating remote sensing data and its impact on LAPS predictability

Presentación realizada en la 3rd European Nowcasting Conference, celebrada en la sede central de AEMET en Madrid del 24 al 26 de abril de 2019

Dynamic downscaling of the ERA-40 data using a mesoscale meteorological model

A sophisticated downscaling procedure that was applied to reproduce high resolution historical records of the atmospheric conditions across the Mediterranean region is presented in this paper. This was accomplished by the dynamical downscaling of the European Center for Medium-Range Forecasts ERA-40 reanalyses with the aid of the atmospheric model of the POSEIDON weather forecasting system. The full three dimensional atmospheric fields with 6 hours of temporal resolution and the surface meteorological parameters at hourly intervals were produced for a 10-year period (1995-2004). The meteorological variables are readily available at 10 km resolution and may constitute the atmospheric forcing to drive wave, ocean hydrodynamic and hydrological models, as well as the baseline data for environmental impact assessment studies. A brief overview of the procedure and a quantitative estimation of the benefit of the new dynamical downscaling dataset are presented

Model-derived seasonal amounts of dust deposited on Mediterranean Sea and Europe

The dust amounts deposited on the surface depends critically upon the seasonal varia- bility of the dust cycle in the atmosphere. Analyses of ground and satellite-based obser- vations can lead to useful results in relation to the seasonal variability of dust deposition. However, to gain a feeling of the magnitude and the geographical distribution of the dust deposition on ground surfaces and on coastal and open seas, the use of a credible numerical model is considered essential. In this study, using the SKIRON/Eta weather forecasting system, a database of seasonal amounts of dust deposited on Mediterranean Sea and Europe has been created. © 2003 Elsevier B.V. All rights reserved

Regional atmospheric response to tropical Pacific SST perturbations

An extended domain limited area model was implemented for seasonal-range simulations to assess the effect of tropical Pacific SST perturbations on weather patterns over Europe and Mediterranean. The experimental method consisted of Skiron/Eta model integrations with coarse and fine grid increment using artificially-modified as well as analysis SST forcing. The selected period was August-October 1997. Model simulations with coarse grid increment produced a weak signal in the precipitation pattern and the synoptic scale circulation over Europe, implying a damping of the North Atlantic atmospheric response to the tropical Pacific SST perturbation. Fine resolution experiments suggested an amplified dynamic response providing a direct link between tropical Pacific SST and North Atlantic synoptic circulation. The output signal is mainly attributed to the effective representation of the regional/ mesoscale atmospheric features due to the model implementation with a fine mesh grid. Copyright 2005 by the American Geophysical Union

The weather forecasting system for POSEIDON - An overview

A weather forecasting system has been developed in the framework of the POSEIDON project "Monitoring, forecasting and information system for the Greeks seas". The system is currently running operationally at the National Centre for Marine Research (NCMR) providing detailed and accurate weather forecasts. It also forces a general circulation ocean model and an offshore wave model with the surface fluxes of momentum and heat and with the precipitation rates. Because of the specific applications for marine studies and operations, emphasis was given to the surface processes especially over the water body. The system contains a viscous sublayer model, which is considered as appropriate for a flux description. The system is evaluated systematically with the aid of the POSEIDON buoy network and other meteorological information available. A description of the system and its capabilities are presented below

Transatlantic Saharan dust transport: Model simulation and results

Long-range transport of desert dust from the Sahara across the northern Atlantic has been recorded many times by satellite imagery and ground-based measurements. However, this evidence cannot fully describe all the phases of the atmospheric dust lifecycle. To partly compensate for the lack of such knowledge, an atmospheric model with incorporated dust uptake-transport-deposition module has been used in this study. The goal was to assess qualitatively and quantitatively the ability of the model to predict the dust cycle in the atmosphere for a long period. For this purpose, the complicated dust episode of June-July 1993 (almost one month) was simulated with the SKIRON weather forecasting system. This dust intrusion was associated with long-range transport of Saharan dust across the Atlantic Ocean and simultaneous regional transport towards the Mediterranean Sea. Comparison of the forecasts with the available observations (in a qualitative and quantitatively way) indicated that the model was able to simulate the long-range dust transport patterns and in particular to estimate the spatiotemporal distribution of the dust concentration on a satisfactory way. Copyright 2006 by the American Geophysical Union

Evaluation of POSEIDON forecasts in the Aegean Sea for a three-year period

In this study, the POSEIDON forecasts in the Aegean Sea are evaluated against surface observations retrieved from the POSEIDON buoy network over a three-year period. The estimated fields of the wind speed and direction, the air temperature, the mean sea level pressure, the wave height and direction, the sea surface temperature and the current speed and direction are verified using the point measurements of the buoys. The evalu- ation system consists of various statistical schemes depending on the nature (scalar or vectorial) of the verified fields. Despite the fact that the buoys are located close to the coastline, where topography often modifies the general conditions creating local effects, the numerical models present quite satisfactory forecasting skill. © 2003 Elsevier B.V. All rights reserved

sensitivity on sea surface temperature

www.nat-hazards-earth-syst-sci.net/11/1233/2011