Model HIRLAM Research Articles

Toward Scatterometer Winds Assimilation in the Mesoscale HARMONIE Model

Data assimilation (DA) experiments have been conducted with the high-resolution limited-area model HirLAM Aladin Regional Mesoscale Operational NWP In Euromed (HARMONIE), which is operational at most weather centers, which are part of the European HirLAM consortium. Recently, the assimilation of scatterometer ocean surface winds was introduced, showing limited forecast skill improvement. Possible explanations are discussed. These include model bias and the time mismatch between observation and analysis time, which introduces nonnegligible correlated errors in a three-dimensional (3-D) variational assimilation system. Also, ignoring the time mismatch increases the innovation, i.e., the observation minus background (model short-term forecast), by about 20% for scatterometer winds. The use of observations as point observations in most DA systems needs reconsideration for mesoscale DA. The introduction of observation operators, taking into account the instrument footprint, would improve the innovation by about 5% for scatterometer winds. Additional directions for improved use of observations in HARMONIE are discussed based on the notice that DA is an inherent deterministic concept. Hence, the selection of the spatial scale for deterministic DA should depend primarily on the 4-D observation coverage rather than the effective model resolution.

Hydrodynamic modeling of floods in Saint Petersburg considering the operating dam

The Baltic Sea level is computed from the BALT-P three-dimensional hydrodynamic model at the grid with the horizontal resolution of 2 nautical miles, and the computation for the top of the Gulf of Finland is provided at the grid with the spatial resolution of 90 m. The sea motion is induced by the air pressure gradients and wind stress values from the HIRLAM model forecast specified on the sea surface. The sea level is calculated for three floods in Saint Petersburg with account that each of eight spillways of the dam closed and opened not instantly but during the prescribed period of time. It is revealed that the BALT-P model simulates the sea level well during three floods in Saint Petersburg considering the operating dam. The model can be used for the sea level forecasting in Saint Petersburg based on the HIRLAM atmospheric model data with the lead time of 60 hours.

An improved version of the consequence analysis model for chemical emergencies, ESCAPE

We present a refined version of a mathematical model called ESCAPE, “Expert System for Consequence Analysis and Preparing for Emergencies”. The model has been designed for evaluating the releases of toxic and flammable gases into the atmosphere, their atmospheric dispersion and the effects on humans and the environment. We describe (i) the mathematical treatments of this model, (ii) a verification and evaluation of the model against selected experimental field data, and (iii) a new operational implementation of the model. The new mathematical treatments include state-of-the-art atmospheric vertical profiles and new submodels for dense gas and passive atmospheric dispersion. The model performance was first successfully verified using the data of the Thorney Island campaign, and then evaluated against the Desert Tortoise campaign. For the latter campaign, the geometric mean bias was 1.72 (this corresponds to an underprediction of approximately 70%) and 0.71 (overprediction of approximately 30%) for the concentration and the plume half-width, respectively. The geometric variance was <1.5 (this corresponds to an agreement that is better than a factor of two). These values can be considered to indicate a good agreement of predictions and data, in comparison to values evaluated for a range of other similar models. The model has also been adapted to be able to automatically use the real time predictions and forecasts of the numerical weather prediction model HIRLAM, “HIgh Resolution Limited Area Model”. The operational implementation of the ESCAPE modelling system can be accessed anywhere using internet browsers, on laptop computers, tablets and mobile phones. The predicted results can be post-processed using geographic information systems. The model has already proved to be a useful tool of assessment for the needs of emergency response authorities in contingency planning.

Weather model verification using Sodankylä mast measurements

Abstract. Sodankylä, in the heart of Arctic Research Centre of the Finnish Meteorological Institute (FMI ARC) in northern Finland, is an ideal site for atmospheric and environmental research in the boreal and sub-Arctic zone. With temperatures ranging from −50 to &amp;amp;plus;30 °C, it provides a challenging testing ground for numerical weather forecasting (NWP) models as well as weather forecasting in general. An extensive set of measurements has been carried out in Sodankylä for more than 100 years. In 2000, a 48 m-high micrometeorological mast was erected in the area. In this article, the use of Sodankylä mast measurements in NWP model verification is described. Starting in 2000, with the NWP model HIRLAM and Sodankylä measurements, the verification system has now been expanded to include comparisons between 12 NWP models and seven measurement masts, distributed across Europe. A case study, comparing forecasted and observed radiation fluxes, is also presented. It was found that three different radiation schemes, applicable in NWP model HARMONIE-AROME, produced somewhat different downwelling longwave radiation fluxes during cloudy days, which however did not change the overall cold bias of the predicted screen-level temperature.

High Resolution HIRLAM Simulations of the Role of Low-Level Sea-Breeze Convergence in Initiating Deep Moist Convection in the Eastern Iberian Peninsula

We present a numerical investigation of a non-forecast sea-breeze-initiated thunderstorm that occurred unexpectedly in the eastern complex area of the Iberian Peninsula (Spain) on 7 August 2008. A high horizontal (2.5-km grid spacing) and vertical (60 sigma levels) resolution set-up of the hydrostatic HIRLAM model is used to simulate the evolution of isolated convection associated with sea breezes. The convective inhibition, convective available potential energy, vertical velocity, wind and precipitation fields are examined here in order to analyze the role of low-level sea-breeze convergence and sea-breeze front development in initiating intense convective activity (heavy rainfall, hail and gusty winds) under weakly defined synoptic disturbances. We observe that convective inhibition layers are eroded by sea-breeze frontal zones, increasing the convective available potential energy due to the enhanced vertical motion, forcing parcels to lift to the level of free convection. We show that the location of thunderstorms along the east coast of the Iberian Peninsula is partly controlled by the impact of sea-breeze fronts on modulating the diurnal spatio-temporal evolution of convective inhibition, convective available potential energy and updrafts.

Sea breeze thunderstorms in the eastern Iberian Peninsula. Neighborhood verification of HIRLAM and HARMONIE precipitation forecasts

In this study we investigated sea breeze thunderstorms with intense convective activity (i.e., heavy rainfall, hail and gusty winds) that occurred over the eastern Iberian Peninsula (Spain) and were missed by the operational HIRLAM model. We used two grid-spacing setups (5.0km and 2.5km) of the hydrostatic HIRLAM model, and the non-hydrostatic spectral HARMONIE suite (2.5km), to simulate isolated convection associated with sea breezes. The overall aim is to estimate the ability of these three experimental setups, in particular the HARMONIE model as the forthcoming operational numerical weather prediction in most European Weather Services, to correctly simulate convective precipitation associated with sea breezes. We evaluated high-resolution gridded precipitation forecasts from HIRLAM and HARMONIE suites for 15 sea breeze thunderstorms against high-density gridded raingauge measurements applying different neighborhood verification techniques. The results indicate that higher horizontal resolutions of HIRLAM and HARMONIE models succeeded in predicting the occurrence of these missed sea breeze thunderstorms, the HARMONIE suite being the most capable of providing good estimates of accumulated precipitation in convective events in terms of space and time. Advances in quantitative precipitation forecasting of locally driven convection could have practical applications for nowcasting dangerous sea breeze convective phenomena.

Evaluation of the HIRLAM and HARMONIE Numerical Weather Prediction Models during an Air Pollution Episode over Greater İstanbul Area

We have evaluated the performance of operational versions of the numerical weather prediction (NWP) model HIRLAM and HARMONIE in severe air pollution atmospheric conditions in İstanbul in November 18–20 of 2009. During the episode, a high pressure system over northwest Turkey, including İstanbul, lead to the formation of an exceptional ground‐based temperature inversion. The forecasts generated by HIRLAM and HARMONIE models were compared to observations at meteorological stations in the area. Both HIRLAM and HARMONIE 24 h's forecasts are successful to predict possible episode conditions due to meteorological circumstances, and thus both models provide reliable weather input to an air pollution warning system. Results of this study are important especially for those involved in NWP, in air pollution modeling and decision‐making where high resolution NWP model outputs are becoming a valuable product.

A mass-conserving and multi-tracer efficient transport scheme in the online integrated Enviro-HIRLAM model

Abstract. In this paper a new advection scheme for the online coupled chemical–weather prediction model Enviro-HIRLAM is presented. The new scheme is based on the locally mass-conserving semi-Lagrangian method (LMCSL), where the original two-dimensional scheme has been extended to a fully three-dimensional version. This means that the three-dimensional semi-implicit semi-Lagrangian scheme which is currently used in Enviro-HIRLAM is largely unchanged. The HIRLAM model is a computationally efficient hydrostatic operational short-term numerical weather prediction model, which is used as the base for the online integrated Enviro-HIRLAM. The new scheme is shown to be efficient, mass conserving, and shape preserving, while only requiring minor alterations to the original code. It still retains the stability at long time steps, which the semi-Lagrangian schemes are known for, while handling the emissions of chemical species accurately. Several mass-conserving filters have been tested to assess the optimal balance of accuracy vs. efficiency.

Modelling fetch-limited wave growth from an irregular shoreline

The wave model WAM was used to study the effect of the grid resolution and the description of an irregular shoreline on modelling of fetch-limited wave growth. Three different methods to compile a grid for a wave model in the case of an irregular shoreline are discussed. Several combinations of shoreline description, grid resolution, and wind field were used to model the effect of the irregularities of the shoreline on fetch-limited wave growth. The modelling confirmed the usual assumption that these effects will rapidly vanish as the distance from the shore increases. However, close to the shoreline the differences between the modelled values of significant wave height were relatively large. The modelled spectral wave parameters were compared against wave measurements made in the Bothnian Sea in 1976. None of the combinations was able accurately to predict the measured wave growth. Close to the shoreline the modelled wave energy and peak period grew too fast, and further offshore the modelled wave energy was underestimated. Close to the shoreline the most accurate results were obtained when a high-resolution grid of 0.25nmi was used together with a re-analysed wind field from the atmospheric model HIRLAM. The effect of grid resolution on the growth rate of the wave energy at short fetch was relatively large.

The uncertainty of UTCI due to uncertainties in the determination of radiation fluxes derived from numerical weather prediction and regional climate model simulations

In this study we examine the determination accuracy of both the mean radiant temperature (Tmrt) and the Universal Thermal Climate Index (UTCI) within the scope of numerical weather prediction (NWP), and global (GCM) and regional (RCM) climate model simulations. First, Tmrt is determined and the so-called UTCI-Fiala model is then used for the calculation of UTCI. Taking into account the uncertainties of NWP model (among others the HIgh Resolution Limited Area Model HIRLAM) output (temperature, downwelling short-wave and long-wave radiation) stated in the literature, we simulate and discuss the uncertainties of Tmrt and UTCI at three stations in different climatic regions of Europe. The results show that highest negative (positive) differences to reference cases (under assumed clear-sky conditions) of up to -21°C (9°C) for Tmrt and up to -6°C (3.5°C) for UTCI occur in summer (winter) due to cloudiness. In a second step, the uncertainties of RCM simulations are analyzed: three RCMs, namely ALADIN (Aire Limitée Adaptation dynamique Développement InterNational), RegCM (REGional Climate Model) and REMO (REgional MOdel) are nested into GCMs and used for the prediction of temperature and radiation fluxes in order to estimate Tmrt and UTCI. The inter-comparison of RCM output for the three selected locations shows that biases between 0.0 and ±17.7°C (between 0.0 and ±13.3°C) for Tmrt (UTCI), and RMSE between ±0.5 and ±17.8°C (between ±0.8 and ±13.4°C) for Tmrt (UTCI) may be expected. In general the study shows that uncertainties of UTCI, due to uncertainties arising from calculations of radiation fluxes (based on NWP models) required for the prediction of Tmrt, are well below ±2°C for clear-sky cases. However, significant higher uncertainties in UTCI of up to ±6°C are found, especially when prediction of cloudiness is wrong.

Evaluation of ‘GLAMEPS’—a proposed multimodel EPS for short range forecasting

Grand Limited Area Model Ensemble Prediction System (GLAMEPS) is prepared for pan-European, short-range probabilistic numerical weather prediction of fine synoptic-scale, quasi-hydrostatic atmospheric flows. Four equally sized ensembles are combined: EuroTEPS, a version of the global ECMWF EPS with European target; AladEPS, a downscaling of EuroTEPS using the ALADIN model; HirEPS_K and HirEPS_S, two ensembles using the HIRLAM model nested into EuroTEPS including 3DVar data-assimilation for two control forecasts. A 52-member GLAMEPS thus samples forecast uncertainty by three analysed initial states combined with 12 singular vector-based perturbations, four different models and the stochastic physics tendencies in EuroTEPS. Over a 7-week test period in winter 2008, GLAMEPS produced better results than ECMWF’s EPS with 51 ensemble members. Apart from spatial resolution, the improvement is due to the multimodel combination and to a smaller extent the dedicated EuroTEPS. Ensemble resolution and reliability are both improved. Combining uncalibrated ensembles is seen to produce a better combined ensemble than the best single-model ensemble of the same size, except when one of the single-model ensembles is considerably better than the others. Bayesian Model Averaging improves reliability, but needs further elaboration to account for geographical variations. These conclusions need to be confirmed by long-period evaluations.

A comparison of ASCAT wind measurements and the HIRLAM model over the Baltic Sea

This paper presents a comparison of the wind data measured by the ASCAT polar-orbiting satellite scatterometer and winds forecast by the numerical weather prediction model HIRLAM in the Baltic Sea region during the stormy season in 2009. Two different resolution models were used in the comparison. Mutual quality and uncertainty characteristics of the measurements and predictions are determined. The results of the study show that the ASCAT wind data are well correlated with the HIRLAM predicted winds, which raises the credibility of both data sources in operational and hindcasting applications over the Baltic Sea. A case of phase error in a HIRLAM forecast of cyclonic activity over the Baltic Sea is discussed.

Evaluation of ‘GLAMEPS’—a proposed multimodel EPS for short range forecasting

Grand Limited Area Model Ensemble Prediction System (GLAMEPS) is prepared for pan-European, short-range probabilistic numerical weather prediction of fine synoptic-scale, quasi-hydrostatic atmospheric flows. Four equally sized ensembles are combined: EuroTEPS, a version of the global ECMWF EPS with European target; AladEPS, a downscaling of EuroTEPS using the ALADIN model; HirEPS_K and HirEPS_S, two ensembles using the HIRLAM model nested into EuroTEPS including 3DVar data-assimilation for two control forecasts. A 52-member GLAMEPS thus samples forecast uncertainty by three analysed initial states combined with 12 singular vector-based perturbations, four different models and the stochastic physics tendencies in EuroTEPS. Over a 7-week test period in winter 2008, GLAMEPS produced better results than ECMWF’s EPS with 51 ensemble members. Apart from spatial resolution, the improvement is due to the multimodel combination and to a smaller extent the dedicated EuroTEPS. Ensemble resolution and reliability are both improved. Combining uncalibrated ensembles is seen to produce a better combined ensemble than the best single-model ensemble of the same size, except when one of the single-model ensembles is considerably better than the others. Bayesian Model Averaging improves reliability, but needs further elaboration to account for geographical variations. These conclusions need to be confirmed by long-period evaluations.

Evaluation of diabatic initialization improvements in the numerical weather prediction model Hirlam, focusing on the effect this may have on precipitation and dispersion forecasts

Abstract Amongst the key issues concerning mesoscale modeling capability for air pollution and dispersion applications are precipitation and cloud cover forecasts. The long-standing problem of the spin-up of clouds and precipitation in numerical weather prediction models limits the accuracy of the prediction of short-range dispersion and deposition from local sources. Customary the spin-up problem is avoided by only using NWP forecasts with a lead time greater than the spin-up time of the model. Due to the increase of uncertainty with forecast range this reduces the quality of the associated forecasts of the atmospheric flow. Improvements through diabatic initialization in the spin-up of large-scale precipitation in the Hirlam NWP model are discussed. In a synthetic example the effects of these improvements on a dispersion forecast are explored specifically for wet deposition. Using a case study of several weeks the optimal lead time for precipitation is discussed. The analysis presented in this paper leads to the conclusion that, at least for situations where large-scale precipitation dominates, proper diabatic initialization of a weather model may limit spin-up so that its full forecast range can be used. The implication for dispersion modeling is that such an improved model is particularly useful for short-range forecasts and the calculation of local deposition. The sensitivity of the hydrological process to proper initialization implies that the spin-up problem may reoccur with changes in the model and increased model resolution. This is demonstrated using a recent version of Hirlam. Spin-up should therefore not only be an ongoing concern for atmospheric modelers, but a reason for close cooperation with dispersion modelers.

High resolution re-analysis for the Baltic Sea region during 1965–2005 period

Regional reanalysis database BaltAn65+ comprising meteorological data for Baltic Sea region for the time period 1965–2005 is described. For data assimilation and hindcasts, the numerical weather prediction model HIRLAM 7.1.4 is applied, with 11 km horizontal and 60-layer vertical resolution. Reanalysis includes three-dimensional weather analysis data. Standard surface observations and meteorological soundings together with ship and buoy measurements from WMO observational network are used in analysis. Boundary fields are obtained from ECMWF ERA-40 global re-analysis. The BaltAn65+ can be considered as a regional refinement of ERA-40 for Baltic Sea region, providing the historical weather and climate data with enhanced spatial resolution, which is main motivation for creation of this novel reanalysis database.

A study of the underlying surface parameters influence on quality of the hydrodynamic forecasts for the territory of East Africa

An assessment of a new ECOCLIMAP database in terms of the short-range hydrodynamic (Numerical Weather Prediction, NWP) forecasting skills of the HIRLAM model is presented for the territory of East Africa (Tanzania). It was done by incorporating of the ECOCLIMAP database into the HIRLAM NWP system and performing of numerical experiments. The decision-making principles for usage of the ECOCLIMAP database and recommendations for its further development are formulated. Results of intercomparison of the underlying surface parameter fields obtained from the HCS and ECOCLIMAP databases are discussed; it was revealed that, for the territory of East Africa those fields are essentially different. The annual cycle of the parameters obtained from the ECOCLIMAP database is more feasible. It was concluded that use of this database in the HIRLAM NWP system for East Africa (Tanzania) is advisable.

A Finite Element Algorithm of a Nonlinear Diffusive Climate Energy Balance Model

We present a finite element algorithm of a climate diagnostic model that takes as a climate indicator the atmospheric sea-level temperature. This model belongs to the category of energy balance models introduced independently by the climatologists M.I. Budyko and W.D. Sellers in 1969 to study the influence of certain geophysical mechanisms on the Earth climate. The energy balance model we are dealing with consists of a two-dimensional nonlinear parabolic problem on the 2-sphere with the albedo terms formulated according to Budyko as a bounded maximal monotone graph in \({\mathbb{R}}^{2}.\) The numerical model combines the first-order Euler implicit time discretization scheme with linear finite elements for space discretization, the latter is carried out for the special case of a spherical Earth and uses quasi-uniform spherical triangles as finite elements. The numerical formulation yields a nonlinear problem that is solved by an iterative procedure. We performed different numerical simulations starting with an initial datum consisting of a monthly average temperature field, calculated from the temperature field obtained from 50 years of simulations, corresponding to the period 1950–2000, carried out by the Atmosphere General Circulation Model HIRLAM.

Assessment of the impact of key terrestrial observing systems using DMI‐HIRLAM

AbstractFollowing a EUCOS decision to make an assessment of the impact on NWP forecasts of different components of the current observing systems in various combinations, a number of OSEs (Observing System Experiments) have been made by a number of NWP centres, with some running global models and some limited‐area models. The Danish Meteorological Institute (DMI) carried out OSEs with the limited‐area model HIRLAM. The following runs were made by DMI (two periods, one month each): (1) A baseline system (BL); (2) BL + all aircraft wind and temperature data; (3) BL + non‐GUAN radiosonde winds; (4) BL + non‐GUAN radiosonde temperature and wind; (5) BL + wind profiler; (6) as (4) + aircraft wind and temperature; (7) as (4) + non‐GUAN radiosonde humidity; (8) as BL + all in situ data (full combined system); and (9) BL + E‐AMDAR only (no ACARS and no traditional AIREPs). The lateral boundaries for these OSEs were provided by runs made by ECMWF, which was one of the centres to make OSEs with a global model.The main conclusions are that the radiosonde data are the most important data, closely followed by the aircraft data, and that aircraft data and radiosonde data are complementary and not redundant data. Furthermore the results show that it is important to have both wind and temperature profile data; wind data alone produce much poorer impact. Copyright © 2008 Royal Meteorological Society

Application of a potential vorticity modification method to a case of rapid cyclogenesis over the Atlantic Ocean

AbstractA method to modify the potential vorticity of a numerical weather analysis is applied to a case of rapid cyclogenesis over the Atlantic Ocean. The development of the cyclone's intensity in terms of mean sea level pressure is underestimated by the Dutch version of the limited‐area weather prediction model HIRLAM. The analysis shows a rather clear mismatch between the potential vorticity of the analysis and the corresponding water vapour satellite image. A barotropic displacement of potential vorticity, based on a subjective comparison with the water vapour satellite image, improves the forecast in terms of the cyclone's mean sea level pressure eighteen hours after the analysis. Similar but different modifications are investigated to assess the sensitivity of the development to the modification applied.The numerical analysis of the global ECMWF model displays a similar mismatch between potential vorticity and water vapour image, although the mismatch is somewhat less dramatic than for the HIRLAM model. Notwithstanding, the ECMWF model describes the development of the mean sea level pressure of the cyclone very well. Investigation of targeted singular vectors and a regular ensemble for this case shows, however, that the forecast is sensitive to perturbations of the initial state, in particular in the region of the potential vorticity/water vapour mismatch. The operational forecast lies in the middle of the ECMWF ensemble, the ensemble containing members with both stronger and weaker development of the cyclone.Our study confirms that a mismatch between an analysed potential vorticity field and a water vapour satellite image might indicate an error in the analysis. However, the error is not necessarily confined to the upper atmosphere and may involve the lower atmosphere as well. Pairs of ECMWF ensemble members, differing according to the sign of the initial perturbation and leading to either shallow or deep cyclones, are studied to shed some light on the effect of different initial conditions. The modification that improves the HIRLAM forecast resembles one of the more strongly developing ensemble members, indicating that the modification lies within the range of acceptable possibilities. Copyright © 2007 Royal Meteorological Society

Non-hydrostatic semi-elastic hybrid-coordinate SISL extension of HIRLAM. Part I: numerical scheme

Two-time-level, semi-implicit, semi-Lagrangian (SISL) scheme is applied to the non-hydrostatic pressure coordinate equations, constituting a modified Miller—Pearce—White model, in hybrid-coordinate framework. Neutral background is subtracted in the initial continuous dynamics, yielding modified equations for geopotential, temperature and logarithmic surface pressure fluctuation. Implicit Lagrangian marching formulae for single time-step are derived. A disclosure scheme is presented, which results in an uncoupled diagnostic system, consisting of 3-D Poisson equation for omega velocity and 2-D Helmholtz equation for logarithmic pressure fluctuation. The model is discretized to create a non-hydrostatic extension to numerical weather prediction model HIRLAM. The discretization schemes, trajectory computation algorithms and interpolation routines, as well as the physical parametrization package are maintained from parent hydrostatic HIRLAM. For stability investigation, the derived SISL model is linearized with respect to the initial, thermally non-equilibrium resting state. Explicit residuals of the linear model prove to be sensitive to the relative departures of temperature and static stability from the reference state. Relayed on the stability study, the semi-implicit term in the vertical momentum equation is replaced to the implicit term, which results in stability increase of the model.