Helsinki, Finland

The Finnish Meteorological Institute is the government agency responsible for gathering and reporting weather data and forecasts in Finland. It is a part of the Ministry of Transport and Communications but it operates semi-autonomously. The Institute is an impartial research and service organisation with expertise covering a wide range of atmospheric science activities other than gathering and reporting weather data and forecasts. The headquarters of the Institute is in Kumpula Campus, Helsinki, Finland. Wikipedia.

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Vihma T.,Finnish Meteorological Institute
Surveys in Geophysics | Year: 2014

The areal extent, concentration and thickness of sea ice in the Arctic Ocean and adjacent seas have strongly decreased during the recent decades, but cold, snow-rich winters have been common over mid-latitude land areas since 2005. A review is presented on studies addressing the local and remote effects of the sea ice decline on weather and climate. It is evident that the reduction in sea ice cover has increased the heat flux from the ocean to atmosphere in autumn and early winter. This has locally increased air temperature, moisture, and cloud cover and reduced the static stability in the lower troposphere. Several studies based on observations, atmospheric reanalyses, and model experiments suggest that the sea ice decline, together with increased snow cover in Eurasia, favours circulation patterns resembling the negative phase of the North Atlantic Oscillation and Arctic Oscillation. The suggested large-scale pressure patterns include a high over Eurasia, which favours cold winters in Europe and northeastern Eurasia. A high over the western and a low over the eastern North America have also been suggested, favouring advection of Arctic air masses to North America. Mid-latitude winter weather is, however, affected by several other factors, which generate a large inter-annual variability and often mask the effects of sea ice decline. In addition, the small sample of years with a large sea ice loss makes it difficult to distinguish the effects directly attributable to sea ice conditions. Several studies suggest that, with advancing global warming, cold winters in mid-latitude continents will no longer be common during the second half of the twenty-first century. Recent studies have also suggested causal links between the sea ice decline and summer precipitation in Europe, the Mediterranean, and East Asia. © 2014, The Author(s).

Karpechko A.Y.,Finnish Meteorological Institute
Geophysical Research Letters | Year: 2010

Atmospheric circulation variability associated with the Northern Annular Mode (NAM) modulates the climate over large areas in the Northern Hemisphere. Therefore, it is expected that future NAM changes in response to greenhouse gas concentration increases and other forcing will influence the climate change in these regions. Climate models simulate a wide range of future NAM changes, which introduces an uncertainty into regional climate predictions. To quantify this uncertainty we use the intermodel spread of the climate projections by the models participated in the Intergovernmental Panel on Climate Change Fourth Assessment Report. We show that the intermodel spread of the future NAM projections account for up to 40% of the variance of the surface temperature and precipitation projections over some regions in Eurasia and North America across the simulations. This result implies that the uncertainty in the future NAM makes a considerable contribution into the overall uncertainty in regional climate predictions. © 2010 by the American Geophysical Union.

Schultz D.M.,Finnish Meteorological Institute
Bulletin of the American Meteorological Society | Year: 2010

The factors leading to the rejection rates for journal publishing in the atmospheric sciences is discussed. the rejection rates of submissions is less than the ultimate success rate for manuscripts because manuscripts can be withdrawn by the author and rejected manuscripts can be revised and resubmitted to the same or to a different journal with the hope of being published. Journals with low rejection rates include IJM (2%), unnamed (9%), NHESS (10%) and ACP (12%). The low rejection rates of these journals with a low number of submissions may be results of striving to improve received submissions and grow the journal. The reason for low rejection rate is the interactive peer review and public discussion which indeed has a deterring deficient submission and counteract the flooding of the scientific publication market.

Leinonen J.,Finnish Meteorological Institute
Optics Express | Year: 2014

The PyTMatrix package was designed with the objective of providing a simple, extensible interface to T-Matrix electromagnetic scattering calculations performed using an extensively validated numerical core. The interface, implemented in the Python programming language, facilitates automation of the calculations and further analysis of the results through direct integration of both the inputs and the outputs of the calculations to numerical analysis software. This article describes the architecture and design of the package, illustrating how the concepts in the physics of electromagnetic scattering are mapped into data and code models in the computer software. The resulting capabilities and their consequences for the usability and performance of the package are explored.©2014 Optical Society of America.

Karvonen J.,Finnish Meteorological Institute
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014

High-resolution ice concentration information is required for navigation purposes, validating ice models, and data assimilation. The currently available operational ice concentration products are based on microwave radiometer data, and their typical resolution is several kilometers. We present an algorithm for the estimation of ice concentration based on dual-polarized (HH/HV) C-band synthetic aperture radar (SAR) data. The algorithm is based on the multilayer perceptron (MLP) neural network. Ice concentration estimated based on the HH channel is used as one MLP input, and the local incidence angle is used as another. The additional inputs are based on the HV channel. Digitized Finnish Ice Service ice charts, which were also used as the training data, the SAR-based HH-channel ice concentration, and the ice concentration based on a radiometer algorithm are used as reference data sets. The results for the dual-polarized algorithm show improvement compared to the algorithm based on HH-polarized SAR data only. © 2014 IEEE.

L. Van De Kamp M.M.J.,Finnish Meteorological Institute
Annales Geophysicae | Year: 2013

The ionosphere above Scandinavia in December 2006 is successfully imaged by 4-dimensional tomography using the software package MIDAS from the University of Bath. The method concentrates on medium-scale structures: between 100 km and 2000 km in horizontal size. The input consists of TEC measurements from the dense GPS network Geotrim in Finland. In order to ensure sufficient vertical resolution of the result, EISCAT incoherent scatter radar data from Tromsø are used as additional input to provide the vertical profile information. The TEC offset of the measurements is unknown, but the inversion procedure is able to determine this automatically. This auto-calibration is shown to work well. Comparisons with EISCAT radar results and with occultation results show that the inversion using EISCAT data for profile information is much better able to resolve vertical profiles of irregular structures than the inversion using built-in profiles. Still, with either method the intensities of irregular structures of sizes near the resolution (about 100 km horizontal size) can be underestimated. Also, the accuracy of the inversion worsens above areas where no receivers are available. The ionosphere over Scandinavia in December 2006 often showed a dense E-layer in early morning hours, which generally disappeared during midday when a dense F-layer was present. On 14 December, a strong coronal mass ejection occurred, and many intense irregularities appeared in the ionosphere, which extended to high altitudes. © 2013 Author(s).

Karvonen J.,Finnish Meteorological Institute
Annals of Glaciology | Year: 2013

The Finnish Meteorological Institute has installed image-capturing devices on some Baltic Sea coastal radars for operational sea-ice monitoring and ice product validation. These devices produce radar images, which are saved operationally at about every 2min. These data can efficiently be utilized in automated tracking of ice motion over sequences of radar images. Reliable estimates of point-wise ice drift can be used as virtual drifter buoys to validate fine-scale ice models. For this purpose we have developed an algorithm, which first locates objects that can reliably be recognized from one radar image to another, and then tracks the motion of these objects until they are lost by the algorithm. The recognizable objects in the first image of an image sequence are located by requiring an object to include a textural content, i.e. the object does not solely consist of a uniform area, and detected edge corner points. The corner points are required to exclude straight linear edges. After locating a suitable number of traceable objects, the tracking is performed between each pair of successive images using a two-resolution phase-correlation algorithm. We have tested the tracking algorithm using image sequences of two coastal radars collected during the 2010/11 and 2011/12 winters.

Karvonen J.,Finnish Meteorological Institute
Ocean Science | Year: 2012

An algorithm for computing ice drift from pairs of synthetic aperture radar (SAR) images covering a common area has been developed at FMI. The algorithm has been developed based on the C-band SAR data over the Baltic Sea. It is based on phase correlation in two scales (coarse and fine) with some additional constraints. The algorithm has been running operationally in the Baltic Sea from the beginning of 2011, using Radarsat-1 ScanSAR wide mode and Envisat ASAR wide swath mode data. The resulting ice drift fields are publicly available as part of the MyOcean EC project. The SAR-based ice drift vectors have been compared to the drift vectors from drifter buoys in the Baltic Sea during the first operational season, and also these validation results are shown in this paper. Also some navigationally useful sea ice quantities, which can be derived from ice drift vector fields, are presented. © Author(s) 2012.

Karvonen J.,Finnish Meteorological Institute
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2012

Ice concentration measurements are important information e.g., for navigation, ice modeling, and climate change research. Here we present an algorithm for estimating ice concentration from C-band SAR data. The resolution of SAR data is significantly higher than the resolution of the current operational ice concentration products based on radiometer data. Our algorithm is based on segment-wise autocorrelation distributions. The algorithm results were compared with two reference data sets: ice concentrations from the Finnish Ice Service (FIS) ice charts, and ice concentrations from the radiometer-based operational ice concentration algorithm of University of Bremen. The new algorithm gives reasonable ice concentration estimates in a high resolution (500 m) for an arbitrary segmentation. © 2008-2012 IEEE.

Eerola K.,Finnish Meteorological Institute
Weather and Forecasting | Year: 2013

The High-Resolution Limited-Area Model (HIRLAM) international research program maintains a synoptic-scale NWP system. At the Finnish Meteorological Institute, the HIRLAM system has been run operationally since 1990. The HIRLAM forecasts from 1990 to 2012 have been verified against the numerical analysis. In 2-day forecasts, the monthly rms error of the mean sea level pressure has decreased from about 4 to about 2 hPa; that is, the error is now about half of the value it was in the early 1990s. Similar reduction is seen in the 500-hPa height. The negative bias has decreased significantly. In addition, the dependence on the weather regime, measured as the correlation between the North Atlantic Oscillation (NAO) index and rms error, has decreased. The reason for these improvements can often be attributed to changes in the HIRLAM system. A single improvement, improving most significantly the forecast skill, is the rerun concept, which improves the HIRLAM first guess by utilizing the high-quality ECMWF analysis. Verifying against observations or against the initial analysis gives similar results for a 48-h forecast. For a 6-h forecast, however, the field verification gives lower rms error values and lower bias values. In summary, the results indicate that the goal of the HIRLAM program has been fulfilled: to develop and maintain an up-to-date NWP system for 1- and 2-day forecasts on a limited domain. © 2013 American Meteorological Society.

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