Jørn Kristiansen

• Norwegian Meteorological Institute

A data-driven model (DDM) suitable for regional weather forecasting applications is presented. The model extends the Artificial Intelligence Forecasting System by introducing a stretched-grid architecture that dedicates higher resolution over a regional area of interest and maintains a lower resolution elsewhere on the globe. The model is based on...

Numerical systems used for weather and climate predictions have substantially improved over past decades. We argue that despite a continued need for further addressing remaining limitations of their key components, numerical prediction systems have reached a sufficient level of maturity to examine and critically assess the suitability of Earth's cu...

The Iceland and Greenland Seas are a crucial region for the climate system, being the headwaters of the lower limb of the Atlantic Meridional Overturning Circulation. Investigating the atmosphere–ocean–ice processes in this region often necessitates the use of meteorological reanalyses—a representation of the atmospheric state based on the assimila...

Citizen weather stations are rapidly increasing in prevalence and are becoming an emerging source of weather information. These low-cost consume-rgrade devices provide observations in real time and form parts of dense networks that capture high-resolution meteorological information. Despite these benefits, their adoption into operational weather pr...

Strengthening weather services with open weather data and public digital goods. Reliable, usable, understandable and accessible weather forecasts are of great importance for emergency preparedness, planning and efficient use of resources in a number of sectors. However, individuals and organisations in many developing countries currently have poor...

A coordinated atmosphere-ocean research project, centered on a rare wintertime field campaign to the Iceland and Greenland Seas, seeks to determine the location and causes of dense water formation by cold-air outbreaks. The Iceland Greenland Seas Project (IGP) is a coordinated atmosphere-ocean research program investigating climate processes in the...

In this study a 1-yr dataset of a convective-scale atmospheric prediction system of the European Arctic (AROME-Arctic) is compared with the ECMWF's medium-range forecasting, ensemble forecasting, and reanalysis systems, by using surface and radiosonde observations of wind and temperature. The focus is on the characteristics of the model systems in...

The mass, momentum and energy fluxes between the atmosphere and ocean surface depend on the state of the ocean surface. The fluxes in turn can significantly alter the nature of the marine boundary layer and the state of the ocean surface. These interactions can be modelled deterministically using a multiphase modelling approach or using a semi-stoc...

We present a multiscale approach to model a windfarm under real meteorological conditions. The multiscale model consists of a mesoscale atmospheric code coupled to a stochastic ocean wave model, a microscale model and a super-microscale model. The mesoscale model (with 2.5km × 2.5km horizontal resolution) forces the microscale model (with finer 100...

Since October 2013 a convective-scale weather prediction model has been used operationally to provide short-term forecasts covering large parts of the Nordic region. The model is now operated by a bilateral cooperative effort [Meteorological Cooperation on Operational Numerical Weather Prediction (MetCoOp)] between the Norwegian Meteorological Inst...

Offshore wind energy compared to its onshore counterpart appears more attractive due to its lesser visual impact and lesser issues related to land acquisition. Relatively more convenient accessibility to open sea allows for the installation of larger and larger turbines capable of producing much more power resulting in far lesser number of turbines...

Many people depend on and use weather forecasts to plan their schedules. In so doing, ordinary people with no expertise in meteorology are frequently called upon to interpret uncertainty with respect to weather forecasts. With this in mind, this study addresses two main questions: 1) How do laypeople interpret online weather reports with respect to...

olar lows are short lived maritime mesoscale cyclones that develop because of processes unique to the Polar Regions. In the ice-free Nordic and Barents Seas they are associated with violent weather during wintertime and form in cold air outbreaks underneath a cold through. The longer predictability of the large-scales may provide early warnings of...

Eight symposium on policy and socio-economic research: https://ams.confex.com/ams/93Annual/webprogram/Paper212104.html

Presentation: https://presentations.copernicus.org/EMS2012-64_presentation.pdf

The high-resolution (4-km grid length) Met Office (UKMO) Unified Model forecasts driven by the coarser-resolution (8-km grid length) High-Resolution Limited-Area Model (HIRLAM), UM4, often produce significantly colder screen-level (2 m) temperatures in winter over Norway than forecast with HIRLAM itself. To diagnose the main error source of this co...

In this study we have evaluated the JULES (Joint UK Land Environment Simulator) multi-layer snow-scheme at 18 weather stations in Norway. The stations are mainly located close to or within forested areas, but some are also located at exposed high-mountain areas. JULES has been run for single points (1D study), using forcing data which combines both...

Polar lows are intense mesoscale cyclones that mainly occur during the winter over the sea in polar regions. Owing to their small spatial scale with a diameter between 200 and 1000 km, simulating polar lows is a challenging task. In this study we investigated how increased resolution of a numerical weather prediction model impacts its ability to si...

Severe weather is frequently associated with polar lows over ice-free waters during Arctic winter. We propose a high-resolution, limited area ensemble prediction system (EPS) to enable early warnings of such events. The system (UMEPS) employs the UK Met Office non-hydrostatic Unified Model at 4-km resolution to downscale the 21 ensemble members of...

The atmospheric Integrated Forecast System model from the European Centre for Medium-Range Weather Forecasts is used to calculate forcing perturbations which are optimal in producing atmospheric response patterns resembling the ‘cold-ocean-warm-land’ (COWL) flow regime over 4 d. Similar initial state perturbations are computed for comparison. COWL...

The atmospheric Integrated Forecast System model from the European Centre for Medium-Range Weather Forecasts is used to calculate forcing perturbations which are optimal in producing atmospheric response patterns resembling the ‘cold-ocean-warm-land’ (COWL) flow regime over 4 d. Similar initial state perturbations are computed for comparison. COWL...

The atmospheric Integrated Forecast System model from the European Centre for Medium-Range Weather Forecasts is used to calculate forcing perturbations which are optimal in producing atmospheric response patterns resembling the ‘cold-ocean-warm-land’ (COWL) flow regime over 4 d. Similar initial state perturbations are computed for comparison. COWL...

Eighteen years of monthly averaged low cloud cover data from the International Satellite Cloud Climatology Project are correlated with both total solar irradiance and galactic cosmic ray flux from neutron monitors. When globally averaged low cloud cover is considered, consistently higher correlations (but with opposite sign) are found between low c...

We present a re-evaluation of the hypothesis of a coupling between galactic cosmic rays, clouds and climate. We have used two independent estimates of low cloud cover from the International Satellite Cloud Climatology Project, covering 16.5 years of data. The cloud cover data are used in conjunction with estimates of galactic cosmic ray flux and me...

We present a re-evaluation of the hypothesis of a coupling between galactic cosmic rays, clouds and climate. We have used two independent estimates of low cloud cover from the International Satellite Cloud Climatology Project (ISCCP), covering 16.5 years of data. The cloud cover data are used in conjunction with three independent estimates of solar...

In order to evaluate a recent hypothesis of a coupling between galactic cosmic rays, clouds, and climate we have investigated temporal variations in global cloudiness and radiative fluxes at the top of the atmosphere. For this purpose we have used the best available global data sets, i.e., those of the International Satellite Cloud Climatology Proj...

Shortware cloud forcing (SWCF) is one measure of the impact of clouds on radiation and climate. This quantity is determined by insolation, surface albedo, cloud thickness and height, cloud cover and the size distribution of the cloud droplets. We have carried out controlled experiments with a single column model in order to facilitate interpretatio...