C. Fortelius - Academia.edu (original) (raw)

Papers by C. Fortelius

Geoscientific Instrumentation, Methods and Data Systems Discussions, 2015

Sodankylä, in the heart of Arctic Research Centre of the Finnish Meteorological Institute (FMI AR... more 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 +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. Started in 2000 with NWP model HIRLAM and Sodankylä measurements, the verification system has now been expanded to include comparisons between 12 NWP models and seven measurement masts. A case study, comparing forecasted and observed radiation fluxes, is also presented. It was found that three different radiation schemes, applicable in NWP mod...

Modelling re-analysis of dispersion of

Advances in Space Research, 1989

Bulletin of the American Meteorological Society, 2001

European geosciences union general assembly, 2016

The Baltic Sea Experiment’s (BALTEX) Main Experiment commenced on 1 October 1999 and, since then,... more The Baltic Sea Experiment’s (BALTEX) Main Experiment commenced on 1 October 1999 and, since then, the BALTEX Radar Data Centre (BRDC) has been providing homogeneous datasets from the BALTRAD network to a multitude of applications. These datasets are briefly presented. New quality control procedures have been incorporated into the generation of these datasets and new results on the performance of a multisource method for identifying and removing non-precipitation echoes are presented. The performance of the gauge adjustment technique used at the BRDC is also summarized. One application of BRDC datasets is in the validation of precipitation produced by a numerical weather prediction model, and an example of such activities is given. Another application is presented where BRDC datasets have been used in the development of an algorithm for retrieval of precipitation information from different satellite sensors. BALTEX radar activities are being continued as part of the global GEWEX Coor...

Quarterly Journal of the Royal Meteorological Society, 2016

Quarterly Journal of the Royal Meteorological Society, 2015

ABSTRACT The coastal area off Helsinki in the Gulf of Finland has both a complex shoreline and ba... more ABSTRACT The coastal area off Helsinki in the Gulf of Finland has both a complex shoreline and bathymetry which makes modelling the wave field especially challenging. Experience has shown, that these types of areas generally benefits from the use of a high-resolution model grid. Even though the coastal area is very sensitive to the resolution, this is not necessarily true for the boundary field used to force the nested grid. The area outside Helsinki was modelled with the third generation spectral wave model WAM, using a high-resolution 0.1 nmi grid. This nested grid was forced with boundary fields with two different resolutions (1 nmi and 4 nmi), and the difference in significant wave height inside the nested grid due to the change of boundary field is discussed. In comparison to the coarser 4 nmi boundary grid, the finer 1 nmi version was able to model the wave field with higher accuracy near the coastline. This led to an improved accuracy of the modelled significant wave height inside the nested grid also. However, the differences inside the coastal archipelago and at the two wave buoy sites inside the nested grid were insignificant.

ABSTRACT The increasing size of wind turbines, their height and the area swept by their blades ha... more ABSTRACT The increasing size of wind turbines, their height and the area swept by their blades have revised the needs for understanding the vertical structure of wind gusts. Information is needed for the whole profile. In this study, we analysed turbulence measurements from a 100 m high meteorological mast at the Danish National Test Station for Large Wind Turbines at Hø vsø re in Denmark. The site represents flat, homogeneous grassland with an average gust factor of 1.4 at 10 m and 1.2 at 100 m level. In a typical surface layer gust parameterization, the gust factor is composed of two components, the peak factor and turbulence intensity, from which the turbulence intensity was found to rule over the peak factor in determining the effects of stability and height above surface on the gust factor. The peak factor only explained 15 % or less of the vertical decrease of the gust factor, but determined the effect of a gust duration on the gust factor. The statistical method to estimate the peak factor did not reproduce the observed vertical decrease in near neutral and stable conditions and near constant one in unstable conditions. Despite of this inconsistensy, the theoretical method provides estimates for a peak factor when comparing gust durations of 1 s and 3 s with averaging period lengths of 10 min and 1 h. A new technique to study the timing of maxima at different levels relative to the maximum gust at some level was developed. Results showed that a 10 m level maximum gust was typically preceded by maxima at higher levels, and vice versa, a 100 m gust was usually followed by a maximum at lower levels.

The paper re-analyses the consequences of Chernobyl catastrophe for the radionuclide contaminatio... more The paper re-analyses the consequences of Chernobyl catastrophe for the radionuclide contamination of the European region. In the re-analysis, we tried to use the best available information and establish the ground for the source-apportionment studies, similar to those conducted by the team for ETEX experiment. The modelling tool used in the simulations was the Finnish Emergency and Air Quality modelling

Quarterly Journal of the Royal Meteorological Society, 2013

ABSTRACT Wind gusts are traditionally observed and reported at the reference height of 10 m and m... more ABSTRACT Wind gusts are traditionally observed and reported at the reference height of 10 m and most gust parametrization methods have been developed only for this height. In many practical applications, e.g. in wind energy, the relevant heights are, however, up to a few hundred metres. In this study, mean gustiness conditions were studied using observations from two coastal/archipelago weather masts in the Gulf of Finland (northern Europe) with observation heights between 30 and 143 m. Only moderate and strong wind cases were addressed. Both masts were located over relatively flat terrain but the local environment, and hence the surface roughness length, differed between the mast locations. The observations showed that above all the gust factor depended on the surface roughness. Stability had a more pronounced effect over the rough forested surface than over the smooth sea surface. At both locations the stability had a larger effect on gusts than the observation height. Two existing parametrization methods, developed for a 10 m reference height, were validated against the observations and a new parametrization was proposed. In the new method, the gust factor depends on the standard deviation of the wind speed, which is parametrized on the basis of the surface friction velocity, the Obukhov length and height and the boundary-layer height. The new gust parametrization method outperformed the two older methods: the effects of surface roughness, stability and the height above the surface were well represented by the new method.

Meteorological Applications, 2005

STUK-A217 Ympäristön …, 2006

Bulletin of the American Meteorological Society, 2013

The Helsinki Urban Boundary-Layer Atmosphere Network (UrBAN: http://urban.fmi.fi) is a dedicated ... more The Helsinki Urban Boundary-Layer Atmosphere Network (UrBAN: http://urban.fmi.fi) is a dedicated research-grade observational network where the physical processes in the atmosphere above the city are studied. Helsinki UrBAN is the most poleward intensive urban research observation network in the world and thus will allow studying some unique features such as strong seasonality. The network's key purpose is for the understanding of the physical processes in the urban boundary layer and associated fluxes of heat, momentum, moisture, and other gases. A further purpose is to secure a research-grade database, which can be used internationally to validate and develop numerical models of air quality and weather prediction. Scintillometers, a scanning Doppler lidar, ceilometers, a sodar, eddy-covariance stations, and radiometers are used. This equipment is supplemented by auxiliary measurements, which were primarily set up for general weather and/or air-quality mandatory purposes, such ...

gewex.org

... For more detailed description see Jacob et al., 2001. ... Arritt, RW, CJ Anderson, WJ Gutowsk... more ... For more detailed description see Jacob et al., 2001. ... Arritt, RW, CJ Anderson, WJ Gutowski, Jr., ES Takle, Z. Pan, F. Otieno, M. de Castro, D. Caya, S.-C. Chen, JH Christensen, OB Christensen, M. Fox-Rabinovitz, MA Gaertner, F. Giorgi, G. Grell, S.-Y. Hong, C. Jones, H.-MH ...