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The present study aims at producing localized near-surface icing envelopes that contribute to optimal designs of near-surface structures under icing conditions. For this purpose, the 99th percentiles of liquid water content and wind speed that correspond to low-level supercooled clouds are used. Near-surface icing events and cloud microphysics are explored using North American Regional Reanalysis during winter months (D–J–F), over 32 years. The investigation of the regional climatology of icing events involves 74 regional zones that cover Canada. For each zone, regional power loss of wind turbines under icing condition is estimated. The East and West coastal regions of the Hudson Bay demonstrate higher liquid cloud water of 0.4 g m− 3. The highest potential of wind is located in the West coast. The climatology of liquid water content around the Rocky Mountains manifests orographic condensation of the Pacific moisture transported toward the mountains. Within the range of temperatures [− 15 °C to 0 °C], the near-surface results over Canada show that the monthly mean of wind speeds varies mostly between 4 m s− 1 and 10 m s− 1, and the mean supercooled cloud water content decreases linearly from 0.3 g m− 3 to 0.2 g m− 3, with decreasing temperature. The quantification of ice accumulation and the duration of icing events reveal that the West and the South of the Hudson Bay as well as the North of Manitoba and Ontario are exposed to extreme icing conditions, with a monthly accumulation that varies from 150 mm to 225 mm, and a monthly duration of icing events near 375 h. Over the region encompassing the Gaspe Peninsula, St. Lawrence River and New Brunswick the higher limit of wind speed varies around 15 m s− 1. The cloud water upper limit of 0.45 g m− 3 occurs in December and January, and 0.3 g m− 3 in February. With decreasing temperature these upper limits reach 0.1 g m− 3 at − 15 °C. The highest wind energy is located in the Canadian East Coast regions. The Canadian arctic is characterized mostly by lower wind energy and larger power degradation under icing conditions. The average of wind turbine power loss during winter months (D–J–F) under icing conditions varies throughout Canada and reaches its maximum of about 15% over North-East of Manitoba, South of the Hudson Bay and the North coast of Ontario.

In-cloud icing can impose safety concerns and economic challenges for various industries. Icing climate representations proved beneficial for optimal designs and careful planning. The current study investigates in-cloud icing, its related cloud microphysics and introduces a 15-year time period climatology of icing events. The model was initially driven by reanalysis data from North American Regional Reanalysis and downscaled through a two-level nesting of 10 km and 5 km, using a limited-area version of the Global Environment Multiscale Model of the Canadian Meteorological Center. In addition, a hybrid approach is used to reduce time consuming calculations. The simulation realized exclusively on significant icing days, was combined with non-significant icing days as represented by data from NARR. A proof of concept is presented here for a 1000 km area around Gaspe during January for those 15 years. An increase in the number and intensity of icing events has been identified during the last 15 years. From GEM-LAM simulations and within the atmospheric layer between 10 m and 200 m AGL, supercooled liquid water contents indicated a maximum of 0.4 g m− 3, and 50% of the values are less than 0.05 g m− 3. All values of median volume diameters (MVD) are approximately capped by 70 μm and the typical values are around 15 μm. Supercooled Large Droplets represent approximately 5%. The vertical profile of icing climatology demonstrates a steady duration of icing events until the level of 60 m. The altitudes of 60 m and 100 m indicate substantial icing intensification toward higher elevations. GEM-LAM demonstrated a substantial improvement in the calculation of in-cloud icing, reducing significantly the challenge posed by complex terrains.

The large size of modern wind turbines and wind farms triggers processes above the surface layer, which extend to the junction between microscales and mesoscales, and pushes the limits of existing approaches to predict the wind. The main objectives of this study are thus to introduce and evaluate an approach that will better account for physical processes within the atmospheric boundary layer (ABL), and allow for both microscale and mesoscale modeling. The proposed method, in which mathematical model and main numerical aspects are presented, combines a mesoscale approach with a large-eddy simulation (LES) model based on the Compressible Community Mesoscale Model (MC2). It is evaluated relying on a shear-driven ABL case allowing the authors to assess the model behavior at very high resolution as well as more specific numerical aspects such as the vertical discretization and time and space splitting of turbulence-related terms. The proposed LES-capable mesoscale model is shown to perform on par with other similar reference LES models, while being slightly more dissipative. A new vertical discretization of the turbulent processes eliminates a spurious numerical mode in the solution. Finally, the splitting of horizontal and vertical turbulence-related terms is shown to have no impact on the results of the test cases. It is thus demonstrated that the revised MC2 is suitable at both microscales and mesoscales, thus setting a strong foundation for future work.

Wind turbine performance depends mainly on the wind speed and aerodynamics of blades. The roughness generated from ice accretion can significantly reduce the aerodynamics and consequently the power production of the wind turbine. This study locates the glaze and rime ice on the blade, to detect the critical zones involved in significant power production loss. On the blade, the distribution of the elementary power production as well as the type and thickness of the accreted ice are inconsistent. Under icing conditions, the outer section of the blade starting from the radial position r/R = 0.8 contribute significantly to the blades aerodynamics. The freezing fraction is unevenly distributed; since it initially forms rime ice near the root and then glaze toward the tip of the blade. The critical freezing fraction 0.88 associated with the double horn ice shape is spatially limited and occupies a restricted segment on the blade and gradually moves towards the tip with decreasing temperature. With the use of power degradation analogy with sub-scaled rotor blades of a helicopter under icing conditions, a power loss factor is introduced to quantify and locate power loss along the blades of wind turbines. The study is based on four values of liquid water content that delineate five classes of icing severity. Including power loss factor, the most significant power loss that corresponds to freezing fraction 0.88 is found to be located at r/R ~ [0.93 0.96] which corresponds to T = − 2.6 °C, − 4.5 °C, − 12 °C, and − 20 °C and for liquid water content LWC = 0.04 g · m− 3, 0.07 g · m− 3, 0.2 g · m− 3, and 0.36 g · m− 3 respectively. The resulted power degradation can reach a maximum of 40%. Locally it is the shape rather than the thickness of ice that causes more power loss, meanwhile when considering the whole blade, power degradation is controlled mainly by ice thickness regardless of the type of ice. The results obtained can help the setup of a sensor that triggers the ice-protection system upon detection of critical freezing fraction.

The Mesoscale Compressible Community (MC2) model [1], devoted for weather forecasting and used in the Wind Energy Simulation Toolkit (WEST) [2], performs well for simulations over flat, gentle and moderate terrain slopes but is subject to numerical instability and strong spurious flows in presence of steep topography. To remove its inherent computational mode and reduce the wind overestimation due to terrain-induced numerical noise, a new semi-implicit (N-SI) scheme [3] was implemented to discretize and linearize the non-hydrostatic Euler equations with respect the mean values of pressure and temperature instead of arbitrary reference state values, redefining as well the buoyancy to use it as the thermodynamic prognostic variable. Additionally, the climate-state classification of the statistical-dynamical downscaling (SDD) method [4] is upgraded by including the Brunt-Väisälä frequency that accounts for the atmospheric thermal stratification effect on wind flow over topography. The present study provides a real orographic flow validation of these numerical enhancements in MC2, assessing their individual and combined contribution for an improved initialization and calculation of the surface wind in presence of high-impact terrain. By statistically comparing the wind simulations with met-mast data, obtained within the Whitehorse area of the Canadian Rocky Mountains, it is confirmed that these numerical enhancements may reduce over 40 percent of the wind overestimation, thus, attaining more accurate results that ensure reliable wind resource assessments over complex terrain.

Environment Canada (EC) and Hydro-Québec (HQ) have been collaborating in a Research & Development and Demonstration project on a high resolution wind energy dedicated forecasting system (SPÉO: Système de Prévision ÉOlien under its French acronym). This project emphasizes the operational tests and the forecast of high impact events, e.g. wind ramps. It was found that SPÉO improves the Canadian Regional Deterministic Prediction System (RDPS), by about 18% in terms of the RMSE (Root Mean Square Error) of the predicted wind speed when compared with mast observations from three wind power plants. The improvement is most significant in the cold season. When the average wind speed measured at all wind turbines (nacelle anemometer) is used as a reference, SPÉO improves the RMSE of the average wind speed at a wind power plant in complex terrain (24%) compared with that of RDPS. However, there is almost no improvement for two other wind power plants located in less complex terrain. The average wind speed is corrected with the average wind speed measured at all turbines, and is then fed into a wind-to-power conversion module for power production forecasts. The power production forecast is improved by 6% on average in complex terrain when SPÉO winds are used as input compared to the RDPS. The most important finding of this project is SPÉO's ability to predict ramps due to mountain waves/downslope winds. The proposed forecast index for ramps based on the Froude number is useful for predicting the onset of this kind of ramp when a high resolution NWP model is unavailable.

Atmospheric icing became a primary concern due to the significant impact and hazardous conditions of its accretion on structures. The objective of this study is to provide a map of icing events over 32 years (1979 to 2010) that describes the severity of winter icing. This information will prove useful to prevent damages and economical losses due to icing events by documenting the risk factor. To validate the icing climatology method, two case studies involving two topographically contrasting sites were selected: a simple terrain site which is the airport of Bagotville, near Saguenay (Canada) and a complex terrain site located in Mt Belair, near Quebec City (Canada). Ice accumulation calculated by the use of reanalysis data was quantified using ice accretion on a cylinder model. Comparison between measurement and the model over Bagotville revealed insignificant differences in ice accumulation less than 0.3 mm, and in duration of icing events less than 0.2 day. On the other hand, during winter months, the calculation that showed a maximum of 60 mm in January 1999 over Mt Belair site also had an underestimation of ice accumulation that varies from 5 mm to 16 mm. The horizontal resolution of NARR imposes a challenge on the calculation of icing events over complex terrains, especially during the months of November and March when air temperature is near freezing point. Taking into account the liquid water content, the duration of icing events and the classes of icing events as weighting factors, the icing severity index based on reanalysis data was introduced to assess the severity level of icing events, covering the north-east of Quebec including Quebec City, Sept-Iles, the east of Saguenay, the lower St Lawrence River and the Gaspe region. Consequently, an icing severity index mapping that represents the climatology of in-cloud atmospheric icing was produced.

Although the Mesoscale Community Compressible (MC2) model successfully reproduces the wind climate (for wind energy development purposes) of the Gaspe region, equivalent simulations for the steep moun- tainous southern Yukon have been unsatisfactory. An important part of the problem lies in the provision of suit- able boundary conditions in the lower troposphere. This paper will describe an alternative provision of boundary conditions to the MC2 model based partly on standard National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis statistics, however, with modified lower tropos- pheric conditions based on local radiosonde measurements. The MC2 model is part of the AnemoScope wind energy simulation toolkit which applies statistical-dynamical downscaling of basic large-scale weather situations (i.e., the NCEP/NCAR Reanalysis) to simulate the steady- state wind climate of a complex region. A case study summarized here imposes a typical mean winter tempera- ture inversion on the boundary conditions to reduce downward momentum transfer in the MC2 model over the Whitehorse region. In conjunction with this step, the geostrophic wind at the boundaries is held constant (with height) in speed and direction, based on the (observed) dominant southwesterly winds above the mountaintops. The resulting simulation produces wind directions within the modelled domain that are in much better agreement with the available measurements. However, despite the imposed atmospheric stability, downward transfer of hor- izontal momentum from aloft still appears to exceed that occurring in nature. It is recommended that (in future studies of this type regarding mountain wind climate) the input statistics processed from the NCEP/NCAR Reanalysis be modified by referencing the geostrophic winds to a level above the mountaintops. It is also suggested that converting to a height (z) coordinate system may reduce the erroneous downward momentum transfer found in the present terrain-following grid. RESUME (Traduit par la redaction) Meme si le modele de mesoechelle compressible communautaire (MC2) reproduit adequatement la climatologie du vent (pour les besoins du developpement eolien) dans la region de Gaspe, il n'y est pas parvenu de facon satisfaisante lors de simulations equivalentes dans les regions de montagnes escarpees du sud du Yukon. Une partie importante du probleme reside dans la fourniture de conditions aux limites appropriees dans la basse troposphere. Cet article decrira une autre facon de fournir des conditions aux limites du modele MC2 fondee en partie sur les statistiques normalisees des reanalyses des NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) avec, cependant, des conditions modifiees dans la basse troposphere en fonction des mesures locales obtenues par radiosondes. Le modele MC2 fait partie de la trousse de simulation de l'energie eolienne AnemoScope qui applique une reduction d'echelle statistique-dynamique a des situations meteorologiques a grande echelle (c.-a-d. les reanalyses des NCEP/NCAR) pour simuler la climatologie du vent en regime permanent dans une region au relief accidente. Une etude de cas que l'on resume ici impose une inversion thermique moyenne caracteristique de l'hiver comme conditions aux limites pour reduire le transfert de quantite de mouvement vers le bas dans le modele MC2 au-dessus de la region de Whitehorse. En meme temps, le vent geostrophique aux limites est maintenu constant (avec la hauteur) en vitesse et en direction et base sur les vents dominants du sud-ouest (observes) au-dessus du sommet des montagnes. La simulation resultante produit des directions du vent dans le domaine modelise qui s'accordent beaucoup mieux avec les mesures que nous avons. Cependant, malgre la stabilite atmospherique imposee, le transfert de quantite de mouvement vers le bas a partir des couches en altitude semble encore plus important que dans la realite. Nous recommandons que (dans les futures etudes de ce genre sur la climatologie du vent en regions montagneuses) les statistiques derivees des reanalyses des NCEP/NCAR fournies en entree soient modifiees en definissant les vents geostrophiques par rapport a un niveau situe au-dessus du sommet des montagnes. Nous pensons aussi que l'emploi d'un systeme de coordonnees de hauteur (z) pourrait reduire le transfert errone de quantite de mouvement vers le bas observe avec la grille actuelle, qui epouse le relief.

Wind assessment in a coastal environment remains a complex issue for both synthetic aperture radar (SAR) satellite imagery and numerical weather prediction (NWP) models. This study compares the accuracy of each technique to improve the overall mapping precision of both methods. On the one hand, 14 RADARSAT-1 scenes of the St. Lawrence River (Canada) are converted into wind speeds using a hybrid model function that consists of the CMOD-IFR2 geophysical model function and a C-band polarization ratio. A priori information on wind directions is gathered from QuikSCAT scatterometer and in situ wind data. On the other hand, co-located wind maps are generated with the Environment Canada mesoscale compressible community (MC2) model. Comparisons between these two methods are then presented according to three approaches: a systematic SAR and MC2 comparison at 4 km grid-point spacing, a validation with observations (buoy and QuikSCAT scatterometer), and a local analysis of SAR and MC2 winds along a transect perpendi...

A state-of-art wind mapping system, the Wind Energy Simulation Toolkit (WEST), was developed in the Meteorological Service of Canada (MSC) for use by the wind energy industry. WEST is based on a statistical-dynamical downscaling approach, i.e. (i) a statistical analysis of climate data to determine the basic atmospheric states, and (ii) a dynamic adaptation of each basic state to high-resolution terrain and surface roughness by using mesoscale and microscale models. The approach has already been used by Frank and Landberg (1997), in their KAMM/WAsP method, to create a numerical wind atlas. The novel part of WEST is the fixed wind-speed interval in classification scheme and the integration of different modules (meso-/micro-scale models and statistical module) into a single toolkit in a more portable form. WEST was built for use by industries not having sophisticated computer facilities. WEST is applied to the Gaspé region of Canada. The mesoscale model MC2 (operated within WEST) is run at 5 km resolution, while the microscale model within WEST is at 200 m resolution. The simulation results are evaluated in comparison with tower observations at a height of 40 m above ground level. The mean of the 29 observed sets of wind data is 6.6 m/s. The mean absolute difference between the observed and simulated sets of wind data is 0.83 m/s with MC2 (meso-component of WEST) and 0.69 with ‘full WEST’ (with both meso- and micro- components). The correlation coefficient of the mean wind-speeds between the simulations and observations for the 29 stations is improved from 0.5 with MC2 to 0.7 with WEST.

The wind climate of the mountainous terrain in the southern Yukon is simulated using the Wind Energy Simulation Toolkit (WEST) developed by the Recherche en Prevision Numerique (RPN) group of Environment Canada and is compared to measurements in the field. WEST combines two models that operate at different spatial scales. The Mesoscale Compressible Community (MC2) model is a mesoscale numerical weather prediction model that produces simulations over large domains of the order of a thousand kilometres. The MC2 model uses long‐term synoptic scale wind climate data from the analysis of radiosonde and other observations to simulate mean wind fields at tens of metres above the ground using a horizontal resolution of a few kilometres. The mesoscale results are used as input to MS‐Micro/3 (Mason and Sykes (1979) version of the Jackson and Hunt (1975) model version for microcomputers/3‐dimensional; MS‐Micro hereafter), a more computer‐efficient, microscale model with simpler linearized momentum equations...

The Canadian Mesoscale Compressible Community (MC2) model provided daily forecasts across the Alps at 3-km resolution during the Mesoscale Alpine Programme (MAP) field phase of 1999. Among the results of this endeavor, some have had an immediate impact on MC2 itself as it increasingly became evident that the model was spuriously too sensitive to finescale orographic forcing. The model solves the Euler equations of motion using a semi-implicit semi-Lagrangian scheme in an oblique terrain-following coordinate. To improve model behavior, typical approaches were tried at first. These included a generalization of the coordinate transformation to make the terrain influence decay much more quickly with height as well as the introduction of nonisothermal basic states to diminish the amplitude of numerical truncation errors. The concept of piecewise-constant finite elements was invoked to reduce coding arbitrariness. But it was later pointed out that the problem was very specific and due to a numerical inconsistency. The true height of model grid points is fixed and known in height-based coordinates. Nevertheless, it was discovered that for this semi-Lagrangian scheme to be consistent, the departure height is an unknown that must be obtained in the same manner as the other unknowns.

The dynamics and structure of the lee-side flow over the Po valley during a northerly föhn event, which occurred in the framework of the Mesoscale Alpine Programme Special Observation Period (on 8 November 1999 during Intensive Observation Period 15), has been investigated using aircraft data and high-resolution numerical simulations. Numerical simulations were performed with the mesoscale non-hydrostatic model Meso-NH, using three nested domains (with horizontal resolutions 32, 8 and 2 km), the 2 km resolution domain being centred on the Po valley. The basic data–model comparison, and back-trajectory and tracer release analyses, provided evidence that the jet/wake structure of the flow above the Po valley could be reasonably identified with the mountain pass/peak distributions. Measurements from three aircraft flying below the Alps crestline (at 2700, 1500 and 600 m above sea level) along two 350 km east–west legs, designed to be approximately perpendicular to the northerly synoptic flow, were used to compute the potential vorticity (PV) experimentally assuming the lee-side flow to be two-dimensional. (The simplified form of the PV under these assumptions is hereafter referred to as SPV). Due to increasing lee-side flow curvature with decreasing altitude (caused by flow splitting at the scale of the Alps), the experimentally derived SPV was compared to its simulated counterpart. In situ measurements showed that coherent secondary PV banners (PVB2s) do exist downstream of the complex Alpine terrain, as observations show oscillations between positive and negative values of SPV as expected from the simulations. The details of the structure of the SPV field simulated with Meso-NH were found to be different from the observations (i.e. the location of observed maxima and minima of SPV did not match their simulated counterparts at particular points). This is because the correspondence between observed and modelled velocity and potential temperature fields was not good enough to expect good correspondence between differentiated quantities such as vorticity and potential temperature gradient (since less-reliable shorter-scale features are thereby accentuated). Parametrized processes such as surface drag and internal diffusion, and ‘numerical’ processes, such as model filters, to which PV production mechanisms are sensitive and whose role is difficult to assess, also contribute to the poor agreement between observed and modelled SPV fluctuations. Finally, simulations suggest that lowlevel gravity-wave breaking was the main mechanism responsible for the formation of the elongated PVB2 modelled/observed over the Po valley.

During the Special Observation Period (SOP, 7 September–15 November, 1999) of the Mesoscale Alpine Programme (MAP), the Canadian Mesoscale Compressible Community Model (MC2) was run in real time at a horizontal resolution of 3 km on a computational domain of 350☓300☓50 grid points, covering the whole of the Alpine region. The WATFLOOD model was passively coupled to the MC2; the former is an integrated set of computer programs to forecast flood flows, using all available data, for catchments with response times ranging from one hour to several weeks. The unique aspect of this contribution is the operational application of numerical weather prediction data to forecast flows over a very large, multinational domain. An overview of the system performance from the hydrometeorological aspect is presented, mostly for the real-time results, but also from subsequent analyses. A streamflow validation of the precipitation is included for large basins covering upper parts of the Rhine and the Rhone, and parts of the Po and of the Danube. In general, the MC2/WATFLOOD model underestimated the total runoff because of the under-prediction of precipitation by MC2 during the MAP SOP. After the field experiment, a coding error in the cloud microphysics scheme of MC2 explains this underestimation to a large extent. A sensitivity study revealed that the simulated flows reproduce the major features of the observed flow record for most of the flow stations. The experiment was considered successful because two out of three possible flood events in the Swiss-Italian border region were predicted correctly by data from the numerical weather models linked to the hydrological model and no flow events were missed. This study has demonstrated that a flow forecast from a coupled atmospheric-hydrological model can serve as a useful first alert and quantitative forecast. Keywords: mesoscale atmospheric model, hydrological model, flood forecasting, Alps

In the framework of the RAPHAEL EU project, a series of past heavy precipitation events has been simulated with different meteorological models. Rainfall hindcasts and forecasts have been produced by four models in use at various meteorological services or research centres of Italy, Canada, France and Switzerland. The paper is focused on the comparison of the computed precipitation fields with the available surface observations. The comparison is carried out for three meteorological situations which lead to severe flashflood over the Toce-Ticino catchment in Italy (6599 km2) or the Ammer catchment (709 km2) in Germany. The results show that all four models reproduced the occurrence of these heavy precipitation events. The accuracy of the computed precipitation appears to be more case-dependent than model-dependent. The sensitivity of the computed rainfall to the boundary conditions (hindcast v. forecast) was found to be rather weak, indicating that a flood forecasting system based upon a numerical meteo-hydrological simulation could be feasible in an operational context. Keywords: meteorological models, precipitation forecast

Recent developments in numerical modeling and computer technology will soon allow for limited-area production-type numerical weather prediction at a resolution of 1–2 km. This advance opens exciting prospects for the prediction of airflow and precipitation phenomena in and around mountainous regions, by improving the representation of the underlying topography, and by explicitly simulating (rather than parameterizing) moist convection. During the Special Observation Period (SOP; 7 Sept–15 Nov 1999) of the Mesoscale Alpine Programme (MAP) the Canadian Mesoscale Compressible Community Model (MC2) has been run in real time at a horizontal resolution of 3 km on a computational domain of 350 × 300 × 50 grid points, covering the whole of the Alpine region. An overview of the model configuration and performance will be presented along with simulation and validation results from selected MAP cases. Some critical aspects that require particular attention in future research will also be addressed.

Many studies have demonstrated the importance of land surface schemes in climate change studies using general circulation models (GCMs). However, there have not been many studies that explore the role of land surface schemes in the context of short-range and high spatial resolution precipitation forecasts. The motivation of this study is to examine the sensitivity of simulated precipitation, and sensible and latent heat fluxes, to the use of different land surface schemes at two different spatial resolutions. The meteorological model used is the Mesoscale Compressible Community (MC2) model, and the land surface schemes are the force‐restore method and the Canadian Land Surface Scheme (CLASS). Parallel runs have been performed using MC2/CLASS and MC2/force‐restore at spatial resolutions of 10 and 5 km to simulate the severe precipitation case of 19‐21 July

The purpose of this study is to present the possibilities offered by coupled atmospheric and hydrologic models as a new tool to validate and interpret results produced by atmospheric models. The advantages offered by streamflow observations are different from those offered by conventional precipitation observations. The dependence between basins and sub-basins can be very useful, and the integrating effect of the large basins facilitates the evaluation of state of-the-art atmospheric models by filtering out some of the spatial and temporal variability that complicate the point-by-point verifications that are more commonly used. The streamflow predicted by the coupled atmospheric-hydrologic model versus the measured streamflow is sufficiently sensitive to clearly assess atmospheric model improvements resulting from increasing horizontal resolution and altering the treatment of precipitation processes in the model. A case study for several southern Ontario river basins is presented with the Watflood hydrologic model developed at the University of Waterloo. It is passively coupled to a nonhydrostatic mesoscale atmospheric model (mc2) that is integratedc at horizontal resolutions of 35, 10 and 3 km. The Watflood model is also driven by radar derived precipitation amounts from King City Radar observations. It is demonstrated that the hydrological model is sufficiently sensitive and accurate to diagnose model and radar errors. This tool brings an additional degree of verification that will be very important in the improvement of technologies associated with atmospheric models, radar observations and the water resources management.

The roles and mechanisms of transport and chemical transformation affecting surface ozone in the Canadian southern Atlantic region (SAR) are investigated using a three-dimensional Eulerian comprehensive modeling system. The investigation is focused a regional ozone episode over the eastern North America during the first week of August 1988. The model performance is evaluated with available observations during this period. The model is shown to reproduce the general features of this regional episode, with better performance for the sites with clear local photochemical activities than for those strongly influenced by complex coastal flow. It is shown from the reconstructed time history of various processes along the backward trajectories originating from a site in Nova Scotia that the elevated ground-level ozone in the SAR during the study period was associated with transport at low levels, under a strong southwesterly flow. The high ozone brought to the site was mostly produced within the stable marine boundary layer from precursors picked up earlier over the emission area on the east coast of the United States. A second transport situation was also simulated and shown to be associated with transport aloft that was never mixed to the surface. This study also shows that differential advection, due to stable stratification and vertical shear of horizontal wind, can deform surface-based plumes to produce elevated layers of pollutants over the Gulf of Maine.

The next generation of high-performance computers will be based on clusters of shared-memory symmetric multiprocessor (SMP) nodes interconnected by a low-latency, high-bandwidth network. In this paper, the parallel performance of the nonhydrostatic Mesoscale Compressible Community (MC2) limited-area atmospheric model on clusters of NEC SX-4 symmetric multiprocessor (SMP) nodes is presented. Several hybrid parallel-programming approaches are now possible with the SMP cluster SC-MC2 implementation based on internode MPI message-passing and intranode shared-memory tasking or threads. At total sustained execution rates of between 25 and 30 Gflop s−1 on single-node or multinode clusters, it is now possible for the first time ever to generate a 24–48-h real-time weather forecast over North America at 10-km resolution.

This paper studies the mesoscale wind field during the blizzard of March 1993 off the east coast of North America and examines the influence of the sea surface temperature distribution on surface winds. Can the Gulf Stream and its meanders, by its strong influence on the marine boundary layer, generate mesoscale features in the wind field? Numerical simulations of the storm are carried out using the MC2, a fully elastic nonhydrostatic model. Simulations are conducted at different resolutions (50, 25, 10, 5, and 2 km) with both detailed and smoothed SST fields, so as to examine the influence of these parameters on the marine boundary layer winds. Results from these numerical simulations are compared with surface observations from buoys. The study reveals some mesoscale features in the wind field caused by the Gulf Stream’s meanders and the warm eddies of the SST field. In a stable boundary layer, the meanders shaped a 50–55-kt (26–28 m s−1) band of winds in a general 40–45-kt (21–23 m s−1) wind fi...

Traditional semi‐implicit formulations of nonhydrostatic compressible models may not be stable in the presence of steep terrain when pressure gradient terms are split and lagged in time. If all pressure gradient terms and the divergence are treated implicitly, the resulting wave equation for the pressure contains off‐diagonal cross‐derivative terms leading to a highly nonsymmetric linear system of equations. In this paper we present a more implicit formulation of the Mesoscale Compressible Community (MC2) model employing a Generalized Minimal Residual (GMRES) Krylov iterative solver and a more efficient semi‐Lagrangian advection scheme. Open boundaries now permit exact upwind interpolation and the ability to reproduce simulations to machine precision is illustrated for one‐way nesting at equivalent resolution. Numerical simulations of hydrostatic and nonhydrostatic mountain waves demonstrate the stability and accuracy of the new adiabatic kernel. The computational efficiency of the model is repor...

Wintertime precipitation events in the Mackenzie River basin (MRB) play an important role in the hydrology of the region because they contribute substantially to water storage prior to the spring runoff maximum. The Mesoscale Compressible Community (MC2) Model is used to simulate a representative wintertime MRB precipitation event. The MC2 simulation, gridded analyses, and raw observations are used to (i) document meteorological conditions associated with the precipitation event, (ii) assess the ability of the model to reproduce the precipitation event and antecedent large-scale moisture transport, and (iii) identify which planetary- and synoptic-scale features are responsible for the observed moisture transport using piecewise quasigeostrophic potential vorticity (QGPV) inversion. Precipitation in the MRB develops north of an intense frontal boundary as a southwesterly flow of moisture originating over the Pacific Ocean is lifted over cold, dense arctic air near the surface. A lee cyclone forms ...

The MERMOZ (Montreal-96 Experiment on Regional Mixing and Ozone) field experiment was conducted in the greater Montreal area in June 1996. The measurement program was designed to examine several aspects of boundary layer dynamics and chemical transport. The project featured high-resolution real-time simulations with a mesoscale meteorological model driving several air quality models; the deployment of a research aircraft, fully instrumented for turbulent flux measurements; and a number of other supporting meteorological measurements such as two boundary layer wind profilers, a Doppler weather radar, and a special network of surface stations, upper-air soundings, tethersondes, and ozonesondes. An overview of the MERMOZ field program is presented with some preliminary results on various aspects of the experiment.

Computational fluid dynamics and meteorology in particular are among the major consumers of high performance computer technology. The next generation of atmospheric models will be capable of representing fluid flow phenomena at very small scales in the atmosphere. The mesoscale compressible community (MC2) model represents one of the first successful applications of a semi-implicit, semi-Lagrangian scheme to integrate the compressible governing equations for atmospheric flow in a limited area domain. A distributed-memory SPMD implementation of the MC2 model is described and the convergence rates of various parallel preconditioners for a Krylov type GMRES elliptic solver are reported. Parallel performance of the model on the Cray T3E MPP and NEC SX-4/32 SMP is also presented.

This paper attempts to document the developmental research and early mesoscale results of the new fully nonhydrostatic atmospheric model called MC2 (mesoscale compressible community). Its numerical scheme is the semi-implicit semi-Lagrangian approach conceived and demonstrated by Tanguay, Robert, and Laprise. The dominant effort required to become a full-fledged mesoscale model was to connect it properly to a full-scale and evolving physics package; the enlarged scope of a package previously dedicated to hydrostatic pressure coordinate-type models posed some new questions. The one-way nesting is reviewed and particularly the self-nesting or cascade mode; the potential implication of this mode is explored with a stand-alone forecast experiment and related to the other existing approach employing hemispheric or global variable meshes. One of the strong assets of MC2 is its growing community of users and developers. To demonstrate the wideband characteristic of MC2, that is, its applicability to a l...

A high resolution regional simulation of the severe precipitation episode which gave rise to the floods in the Saguenay, Quebec region during July 19–21, 1996 was performed using the Mesoscale Compressible Community Model (MC2). The model is first calibrated by comparing the simulated precipitation field with radar observations for an earlier precipitation event. The model is then applied without further tuning to the Saguenay episode. This simulation is initialized with the Canadian Meteorological Center (CMC) analyses at a resolution of 35 km. A one-way nested integration is next performed with a resolution of 10 km. The simulated precipitation field compares well with available station observations.

A special operational forecasting guidance was produced during the field phase of the Beaufort and Arctic Storms Experiment (BASE) with the mesoscale compressible community model (MC2). After a brief description of the model, its performance during BASE is compared to observations. The in-house numerical database assembled at RPN especially for the BASE model is described briefly. Based on the 26 September 1994 precipitation bands event at Tuktoyaktuk, a case study shows the model sensitivity to the ice extent in the Beaufort Sea. Some applications of the MC2 model and its two-dimensional variant are mentioned to show the versatility of the model.

The authors evaluate the performance of current regional models in an intercomparison project for a case of explosive secondary marine cyclogenesis occurring during the Canadian Atlantic Storms Project and the Genesis of Atlantic Lows Experiment of 1986. Several systematic errors are found that have been identified in the refereed literature in prior years. There is a high ( low ) sea level pressure bias and a cold ( warm) tropospheric temperature error in the oceanic ( continental ) regions. Though individual model participants produce central pressures of the secondary cyclone close to the observed during the final stages of its life cycle, systematically weak systems are simulated during the critical early stages of the cyclogenesis. Additionally, the simulations produce an excessively weak ( strong ) continental anticyclone ( cyclone ) ; implications of these errors are discussed in terms of the secondary cyclogenesis. Little relationship between strong performance in predicting the mass field and skill in predicting a measurable amount of precipitation is found. The bias scores in the precipitation study indicate a tendency for all models to overforecast precipitation. Results for the measurable threshold ( 0.2 mm) indicate the largest gain in precipitation scores results from increasing the horizontal resolution from 100 to 50 km, with a negligible benefit occurring as a consequence of increasing the resolution from 50 to 25 km. The importance of a horizontal resolution increase from 100 to 50 km is also generally shown for the errors in the mass field. However, little improvement in the prediction of the cyclogenesis is found by increasing the horizontal resolution from 50 to 25 km.

The fully compressible 3D nonhydrostatic semi-implicit semi-Lagrangian MC2 (mesoscale compressible community) model described by Tanguay et al. has been modified in order to incorporate orography through the Gal-Chen and Somerville transformation of the vertical coordinate by Denis. In this study, a 2D version of the model is tested against classical solutions covering various mountain-wave regimes for continuously stratified flows. A close inspection of the propagation of the vertical momentum flux is performed to asses the accuracy and stability of the numerical method. The study emphasizes also the fact that a correct representation of forced hydrostatic gravity waves is reliable for Courant numbers less than 0.5. This limitation may be less severe as the flow becomes more nonhydrostatic. Furthermore, the sensitivity of the isothermal reference state for flows with realistic static stability and over steep slope mountain is explored.

Due to the natural variability of the wind, it is necessary to conduct thorough wind resource assessments to determine how much energy can be extracted at a given site. Lately, important advancements have been achieved in numerical methods of multiscale models used for high resolution wind simulations over steep topography. As a contribution to this effort, an enhanced numerical method was devised in the mesoscale compressible community (MC2) model of the Meteorological Service of Canada, adapting a new semi-implicit scheme with its imbedded large-eddy simulation (LES) capability for mountainous terrain. This implementation has been verified by simulating the neutrally stratified atmospheric boundary layer (ABL) over flat terrain and a Gaussian ridge. These preliminary results indicate that the enhanced MC2-LES model reproduces efficiently the results reported by other researchers who use similar models with more sophisticated sub-grid scale turbulence schemes. The proposed multiscale method also provides a new wind initialization scheme and additional utilities to improve numerical accuracy and stability. The resulting model can be used to assess the wind resource at meso- and micro-scales, reducing significantly the wind speed overestimation in mountainous areas.

The issue of complexity is more and more present in numerous domains of biological research, including aging research. In the present paper, based on a selective review of literature, we propose both a conceptual and a methodological framework to address age-related changes in functional complexity of the neurobehavioral system, presumably resulting from modifications of the coupling between cognitive and sensorimotor processes. In particular, after reviewing pioneering and more recent studies on aging and complexity in the neuromusculoskeletal system, we explore the possibility that an age-induced increase in the coupling between cognitive and sensorimotor domains could be captured by a stronger covariation of high-order variables, common to both cognitive and sensorimotor functioning. Our main assumption is that these variables could behave as neurobehavioral markers of aging in the neuromusculoskeletal system. The present approach markedly differs from other traditional approaches, which focused on process-specific variable correlates of chronological age, domain-by-domain, and task-by-task. It provides a coherent conceptual framework, a terminology, and a method for studying age-related coupling of cognitive and sensorimotor processes with the use of complexity and nonlinear dynamical systems theories.

The implementation of a predictive cloud-water scheme in a regional finite-element weather prediction model is presented. The model employed in this study includes efficient and accurate numerical techniques and is equipped with a relatively extensive parameterization of the planetary boundary layer, surface process, and radiation. The modifications made to the meteorological model in this study include the addition of the advection equation for cloud water to the set of primitive meteorological equations. In our implementation of the predictive cloud-water scheme, the cloud-water equation represents the grid-resolved cloud-water field, whereas the effects of subgrid convective clouds are parameterized with the convective scheme of Kuo. The numerical solution of the advection equation for cloud water is analogous to the solution of the moisture equation using the semi-Lagrangian advection algorithm applied previously in regional weather forecast. The advection of cloud water is performed using th...

High‐resolution versions of the Canadian operational regional finite‐element model (RFE) have been developed to assess their potential in simulating mesoscale, difficult‐to‐forecast and potentially dangerous weather systems commonly referred to as polar lows. The operational (1989) 100‐km version and a 50‐km version of the model have been run for two different polar low cases: one over Hudson Bay and one over Davis Strait. More integrations have also been performed on the Hudson Bay event both at 50 and 25 km to assess the model sensitivity to ice cover. As expected, the reduction in spatial truncation errors provided by the increase in resolution results in a better simulation of the systems. Moreover, when run at higher resolutions the model shows a significant sensitivity to ice cover. The results of the ice‐cover experiments also put into perspective the interaction between the heat and moisture fluxes at the surface, the low‐level wind structure, and the relation of these to the development ...

Anatomical and pharmacological evidence suggests a role for substance P (SP) in the control of vasopressin secretion, but the origins of SP-immunoreactive (IR) projections to the paraventricular (PVH) and supraoptic (SO) nuclei of the hypothalamus have not yet been identified. Combined axonal transport, immunohistochemical, and ablation approaches were used to characterize the organization of SP-IR projections to the PVH. The results may be summarized as follows: (1) SP-IR projections are broadly and prominently distributed throughout the SO and both the magnocellular and parvicellular divisions of the PVH. The distribution within the PVH is quite uniform. (2) Combined retrograde transport-immunohistochemical analyses identified multiple potential sources of SP-IR inputs to the PVH. These included a number of hypothalamic cell groups, the laterodorsal and peduculopontine tegmental nuclei, and the rostral and caudal aspects of the ventrolateral medulla. Portions of the tegmental and medullary SP-IR neurons that were retrogradely labelled following tracer deposits in the PVH also stained positively for choline acetyltransferase or tyrosine hydroxylase, respectively. (3) To evaluate the distribution and prominence of medullary SP-IR projections to the PVH and SO, staining for SP and catecholamine-synthesizing enzymes was carried out in animals that had previously received knife cuts at the level of the pontomedullary border. Pronounced, and roughly parallel decrements in staining for peptide and amines were seen in the magnocellular division of the PVH and in the SO; less marked reductions in SP-IR were evident in the parvicellular division of the PVH. Collectively, these results suggest that SP-IR varicosities are in a position to influence multiple visceral regulatory cell types in the PVH and SO. Inputs to the magnocellular neurosecretory system arise in large measure from medullary neurons in which SP coexists with catecholamines. SP-IR projections to the parvicellular division of the PVH appear to originate from a number of sources.

The usefulness of numerical weather prediction models in very short-range forecasting is limited by the spinup problem, resulting in an underestimation of both the divergent wind component and the precipitation. To alleviate the spinup problem, latent-heating profiles were directly assimilated into the Canadian regional finite-element (RFE) model. The estimates of latent heating were based on the precipitation rates inferred from GOES infrared and visible imagery. The latent heating was distributed in the vertical according to the stratiform condensation scheme of the model, but the heating rates were normalized to correspond to the satellite-inferred rain rates. The initial relative humidity field was enhanced to 95% between sigma-level 0.875 and the cloud top wherever the probability of precipitation, derived from satellite imagery, was larger than 40%. The results of a case study from the Canadian Atlantic Storms Program (CASP) indicated that the spinup time of the vertical motion, initially o...

With the development of a version of the Canadian non-hydrostatic MC2 model optimized for massively parallel processors, it has become possible to solve very large weather forecast problems in a time sufficiently short to envision a realtime daily calculation over a domain covering the entire Alps. MAP is a large multinational research program that will gather new knowledge about the heavy precipitation over steep topography; its field phase is to take place during Fall of 1999. The tentative grid dimensions are 490 − 400 − 35 at a horizontal resolution of 2 km, with possibly a need to increase the number of vertical layers. This is a very large problem to be solved with realtime constraints. The model results will be accessible to the forecasters at the MAP Operations Centre in Innsbruck, to assist in the scientific briefings to dispatch the flight plans of the research aircraft. The forecasts are planned to be performed on the NEC-SX/4 (10 PE) at the CSCS (Centro Svizzero di Calcolo Scientifico) in Manno (Canton Ticino, Switzerland), which is affiliated with the ETH. The current state of this joint effort is presented.

This paper describes the set-up and application of a non-hydrostatic Canadian meteorological numerical model (MC2) for mesoscale simulations of wind field and other meteorological parameters over the complex terrain of Hong Kong. Results of the simulations of one case are presented and compared with the results of radiosonde and aircraft measurements. The model is proved capable of predicting high-resolution, three-dimensional fields of wind and other meteorological parameters within the Hong Kong territory, using reasonable computer time and memory resources.

Elevated ozone levels in the Canadian southern Atlantic region (SAR) are usually associated with regional ozone episodes over the northeastern US and southern Ontario/Quebec, typically under the synoptic settings of a high pressure system to the east over the Atlantic Ocean and a low pressure system to the northwest. Under this condition the southwesterly flow at the backside of the high pressure cell favours the transport of ozone and its precursors from the US northeastern seaboard to the SAR. Observations during the 1993 North Atlantic Regional Experiment field campaign indicate that high ozone observed over the Gulf and over the coast of Nova Scotia is generally related to moderate to fast transport from the Boston-New York corridor, typically in the warm sector ahead of an approaching cold front. However, due to the complicated vertical layering structure that dominates the lower atmosphere over the Gulf of Maine, especially towards the Nova Scotia side, high ozone concentrations are often observed well above the surface unaccompanied by surface ozone events.

Surface precipitation is a key input parameter for hydrologic models. Validation of the precipitation field simulated by an atmospheric model is a first step in the development of a coupled atmospheric-hydrologic model. The objective of the present study is to simulate the surface precipitation using MC2 (Mesoscale Compressible Community Model) in a self-nesting mode. Two heavy rain cases in Quebec are examined. Using the first case (October 14-15, 1995), model parameters are adjusted to obtain a good simulation of the precipitation, when compared with that retrieved from Doppler radar measurements. The model is then applied to the second case (November 8-9, 1996) with no further tuning. The highest resolution used in both studies is 6 km. The spatial distribution of the simulated precipitation is very similar to that retrieved from radar measurements. The difference between the magnitude of the MC2 precipitation and radar estimates is of the same order as the uncertainty of the latter. A time shift is found in the simulated precipitation fields, which increases with the forecast lead time.

The effects of chronic central administration of corticotropin-releasing factor (CRF) on food intake, body weight, and hypothalamic-pituitary-adrenocortical hormones were investigated in rats. The infusion of ovine CRF at doses of 0.3 and 1.0 microgram/h continuously induced decrease in food intake and a suppression of body-weight gain for 7 days. The inhibition of body weight gain induced by CRF could not be accounted for solely by a decreased food intake since the suppression of body-weight gain in CRF-infused rats was significantly greater than that observed in rats which received the same amount of food as the CRF-infused rats. The content of proopiomelanocortin (POMC) -derived peptides in the anterior lobe of the pituitary as well as the plasma levels of ACTH and corticosterone (B) were significantly elevated in CRF-treated rats, and the CRF content in the hypothalamus was significantly decreased. These results suggest that chronic intracerebroventricular (icv) administration of CRF stimulates the synthesis and secretion of POMC-related peptides in the pituitary and suppresses food intake accompanied by inhibition of body weight gain. The results are similar to clinical and laboratory findings observed in patients with stress-induced anorexia.

Several peptides are generated from prosomatostatin (proSS) in addition to somatostatin-14 (SS-14) and somatostatin-28 (SS-28). These are SS-28(1–12), proSS(1–76) and, as shown more recently, proSS(1–63) and antrin. Important variations in the proportion of these molecular forms are seen among different tissues and among different species. Processing of the precursor in the human brain yields minimal quantities of SS-28(1–12) and high levels of proSS(1–76), namely in cortical areas and in the bed nucleus of the stria terminalis. This is in contrast with findings in rat brain, where SS-28(1–12) is a predominant molecular form. Antrin, which corresponds to proSS(1–10), reaches its highest concentration in the antral portion of the stomach (117 ± 13 pmol/g wet weight), where it is found in secretory granules of delta cells. We observed an inverse relationship between levels of antrin and proSS(1–63) after chromatography of various tissue extracts. This suggests a precursor-product relationship between these two peptides.

The biochemical characterization and anatomical distribution of somatostatin binding sites were examined in the brain of the frog Rana ridibunda, and the distribution of the receptors was compared with the location of somatostatin immunoreactive neurons. The pharmacological profile of somatostatin receptors was determined in the frog brain by means of an iodinated superagonist of somatostatin, [125I-Tyr0,DTrp8]S-14. Membrane-enriched preparations from frog brain homogenates were shown to contain high-affinity receptors (KD = 0.78 ± 0.34 nM; Bmax = 103 + 12.7 fmoles /mg protein) with pharmacological specificity for [DTrp] substituted S14 and S28 analogs. The distribution of somatostatin-binding sites was studied by autoradiography on coronal sections of frog brain. Various densities of somatostatin receptors were detected in discrete areas of the brain. The highest concentration of binding sites was observed in the olfactory bulb, in the pallium, and in the superficial tectum. Moderate binding was observed in the striatum, amygdaloid complex, preoptic area, and cerebellum. Immunocytochemical studies of the distribution of somatostatin-28 (S28) related peptides were also conducted in the frog brain. Two antisera that recognize distinct epitopes of the somatostatin molecule have been used for immunohistochemical mapping of the peptide. Antiserum SS9 recognizes both S28 and somatostatin-14 (S14) and allowed the labelling of perikarya. Antiserum S320 recognizes the N-terminal fragment (1–12) resulting from enzymatic cleavage of S28. This latter antiserum, which does not cross-react with S28, stained mainly neuronal processes. At the infundibular level, however, both antisera stained cell bodies and fibers. Immunoreactive somatostatin-related peptides were detected in many areas of the frog brain. In the diencephalon, a heavy accumulation of perikarya and fibers was seen in the preoptic nucleus, the dorsal and ventral infundibular nuclei, and the median eminence. Immunoreactive perikarya were also observed in the telencephalon, especially in the pallium and in thalamic nuclei. Immunostained processes were detected in many telencephalic areas and in the tectum. There was good correlation between the distribution of somatostatin-immunoreactive elements and the location of somatostatin-binding sites in several areas of the brain, in particular in the median pallium, the tectum, and the interpeduncular nucleus. In contrast, mismatching was observed in the olfactory bulb, lateral pallium, and the cerebellum (which contained moderate to high levels of binding sites but virtually no somatostatin-immunoreactive fibers) and the hypothalamic areas (preoptic area and infundibular nuclei), in which a low concentration of binding sites but a high density of immunoreactive perikarya and fibers were detected. The present data provide the first pharmacological characterization and anatomical distribution of somatostatin-binding sites in the brain of a non-mammalian vertebrate species. The present results suggest that many of the major features of somatostatinergic systems described in mammals (e.g., the wide distribution of somatostatinergic neurons and somatostatin-binding sites; pharmacological characteristics of somatostatin receptors) had already arisen in tetrapod ancestors. Such findings suggest that both neuroendocrine and extrahypothalamic somatostatinergic systems have important functions throughout the vertebrate phylum.

A deficiency in somatostatin is the most consistently described neurochemical alteration in Alzheimer's disease (AD) attributable to intrinsic cortical neurons. Somatostatin-28 (SOM-28), an N-terminal-extended form of somatostatin, can be cleaved to form somatostatin-28(1-12)(SOM-28(1-12) ) and somatostatin-14 (SOM-14). We have measured concentrations of SOM-28(1-12)-like immunoreactivity in 8 cortical regions from 12 patients with AD and 13 controls. Significant reductions (P less than 0.001) were found in all cortical regions examined with the largest decrease in temporal lobe. Reductions were significantly correlated with decreases in somatostatin-14-like immunoreactivity in the same regions. The similar reductions of two prosomatostatin-derived peptides in AD cerebral cortex supports the contention that decreased somatostatin immunoreactivity in AD is caused by a degeneration of somatostatin cortical neurons and terminals.

We have isolated from extracts of ovine hypothalami two molecules characterized as somatostatin-28 and somatostatin-4–28 (referred to as somatostatin-25). They were reproduced by solid phase synthesis. In equimolar ratio and depending upon the experimental conditions, synthetic somatostatin-28 and somatostatin-25 are 3–14 times more potent than somatostatin-14 to inhibit the basal in vitro secretion of growth hormone or as stimulated by prostaglandin (PGE 2 ). In early studies in vivo, somatostatin-28 and somatostatin-25 are also more potent than somatostatin-14 in inhibiting the secretion of growth hormone acutely stimulated in the rat by injection of morphine; somatostatin-28 is also longer-acting than somatostatin-14. These results suggest that somatostatin-14, as originally isolated, is a biologically active fragment of a larger molecule of greater specific activity; it should be considered as another form of somatostatin with high biological activity present in some tissues and likely secreted by the tissues along with somatostatin-14 and possibly other somatostatin-peptides of diverse sizes.

The products generated after addition of the ARG-LYS esteropeptidase activity purified from rat brain to synthetic somatostatin-28 were analyzed using radioimmunoassay, HPLC and amino acid analysis. In addition to somatostatin-14, both free arginine and free Lysine were identified together with somatostatin-28. The dipeptide ARG-LYS was not present, which indicates that three peptide bonds were hydrolyzed in order to achieve excision of the doublet. Since it is likely that the octacosapeptide is a precursor for both somatostatin-14 and somatostatin-28, these observations add further support to the hypothesis that the convertase is also involved in the in vivo processing of endogenous somatostatin-28.