Helicopters are sometimes hit by lightning when flying offshore along the coast of Norway. Often, the helicopter’s presence is what triggers the lightning strike, and this phenomenon is called Helicopter Triggered Lightning ...

Accurate forecasts of very low temperatures in stable boundary layer (SBL) conditions in arctic areas remain a challenge in numerical weather prediction. These forecasts are of great importance both for local communities ...

The tropical tropopause layer TTL acts as the gateway for water vapor and other chemical tracers to the stratosphere, and is important for the chemical composition and radiative balance. In this thesis, two reanalyses from ...

The Atlantic meridional overturning circulation (AMOC) is projected to weaken under global warming. This study investigates this weakening overturning and addresses the question regarding which aspects lead to such a ...

Abstract: Increased anthropogenic emissions of nitrogen oxides, carbon monoxide, volatile organic compounds and methane causes production of ozone in the troposphere, particularly in the northern hemisphere. This causes ...

This master study addresses the monthly evolution from April to September of the extremeheat wave that occurred in Europe in 2018. Heat waves cause serious hazards related to regionaleconomics, ecosystems, human health and ...

A transition to renewable energy is needed to mitigate climate change. This transition has been led by wind energy, and it is expected to continue to be the largest source of renewable energy through to 2030 (Sawyer et ...

Periods of unusually high or low temperatures have a significant impact on both nature and society at all times of the year. A possible change in frequency or persistence of such events would impact the wildlife as well ...

The role of sea ice in the climate response after the 536 and 540 CE volcanic eruptions hasbeen investigated through MPI-ESM simulations with imposed volcanic forcing. There is aclear response in the Arctic sea-ice cover ...

Heavy rain events in the Arctic archipelago Svalbard can have a high impact on nature and settlements, and are predicted to become more frequent and intense in the coming decades. This thesis work focuses on heavy rain ...

Previous studies showed the importance to have information about the vertical distribution of precipitation to simulate snow and related cyclone development correctly in regional, mesoscale models. During Christmas 2016, ...

Flux towers provide important climatic information about surface exchange processes in the land-atmosphere system. At the Finse flux tower in alpine Norway, the inhomogeneous surface and hilly terrain influence the quality ...

Air pollution from traffic is a major health problem in urban areas, and there is a great interest in modeling and measuring the dispersion of pollutants from near- ground sources. Due to the complex nature of the motions ...

This thesis explores the meteorology in an urban area during a winter period and how well a numerical model is able to represent it. The air quality in the cities is of large interest to the citizens and policymakers. ...

Precipitation patterns and rates change with global warming. These changes can be separately evaluated in fast and slow responses, the combination of the two are called apparent responses. The fast precipitation responses ...

We know that lichen cover in polar and high altitude regions may change due to grazing or climate change. Some previous studies have found that removal of lichen reduces the albedo and potentially changes the temperature, ...

Two cases of severe thunderstorms that impacted the Oslo area have been investigated. The thunderstorms occurred during the summer of 2014, an extraordinary summer with record high temperatures, number of lightning strikes ...

Soil moisture plays an essential role in the land surface energy balance, ap- portioning the available energy into latent and sensible heat. As an impor- tant boundary for the atmosphere, accurate initialization of the ...

In this thesis, the large-scale thermohaline circulation in the Late Permian was studied. A steady state circulation was obtained by running MITgcm with a 2 times 2 degrees spherical-polar grid, and solving the nonlinear ...

Climate change has increased extreme weather events over the planet. The most robust changes in East Africa (EA) are for daily temperature and precipitation, where high-impact extreme values have become more common. The ...

It is well known that cyclonic and anticyclonic eddies are numerous in the Skagerrak. Nevertheless a systematic analysis of their statistics appears to be missing. This is the topic of the present thesis in which we ...

Observational data from 61 moorings was used to decompose vertical velocity fields into its modal components using two different approaches, one assuming a flat bottom ocean and one assuming an ocean with rough topography. ...

We assess how reliable the Eddy-Covariance (EC) method is in estimating surface fluxes under the difficult conditions that occur in the high Arctic. Emphasis is placed on stable stratification and the breakdown of EC ...

The influence of diminishing sea ice and increased aerosol number concentration on low clouds over the Beaufort Sea, north of Canada and Alaska, has been investigated by use of a formulation of the Weather Research and ...

The timescales of transport from the surface to the tropical tropopause layer (TTL) was studied using the Lagrangian transport model Flexpart. The model was driven by the ERA-Interim reanalysis from the European Center for ...

The advent of satelitte observations revolutionalized Oceanography, and it has unveiled a turbulent ocean circulation dominated by mesoscale eddies (10-100km). Eddies represent an important aspect of the flow, and understanding ...

We consider results from from a one year simulation in the Oslofjord area, produced by an 800- and 300- meter versions of the ROMS model. The two versions differ only in resolution and grid orientation. Our objective is ...

The emission of ozone precursors as CO, and NOx has increased over the last decades, this report looks at how this increase potentially could affect the concentration of tropospheric ozone over India. It gives a short ...

In the summer of 2013, Europe got affected by smoke from wildfires in North America. A haze was covering the sky, attenuating the incident solar radiation, at many places in Europe. Especially during two periods, high ...

Bølgemekanismer i havet slik som ”Stokes drift” bidrar til å systematisk forflytte store mengder vannpartikler i en bestemt retning over store avstander. Stokes drift har blitt studert grundig for overflatebølger for ...

Arktis har vært, og er fortsatt, et utfordrende område for numeriske modeller for studier av fenomener knyttet til skyer. Mye av dette skyldes at skyer ikke blir simulert godt nok. Spesielt det å simulere underkjølt skyvann, ...

Målet med dette arbeidet er å finne ut om moderne numeriske atmosfæremodeller klarer å varsle underkjølt skyvann og underkjølt regn. I den mye brukte atmosfæremodellen WRF (Weather Research and Forcasting [Skamarock et al. ...

Oseanografiske data ble samlet inn ved hjelp av 20 klappmyss i de Nordiske havene i 2007 og 2008, som en del av IPY-prosjektet MEOP. 6112 vertikale profiler av temperatur og konduktivitet ble samlet inn. Selene dykker dypt, ...

Wildfires are a source of major perturbations in the earth-atmosphere system. Between 1997 and 2008, an area of roughly 4 · 106 km2 has been burned each year. Among other species, wildfire aerosols consist of black carbon ...

Anthropogenicgreenhouse gases have become widely accepted as the primary cause of global warming. With increasing emissions rates, warming is set to continue and baring any drastic change in mitigation policies, the rate ...

Tropospheric ozone is currently the third most important anthropogenic greenhouse gas in terms of radiative forcing. In contrast to the long-lived greenhouse gases, e.g. CO2 and CH4, ozone has the ability to cause regional ...

Paltridge (1975,1978) proposed that the atmosphere seeks to maximize entropy production, as a non-equilibrium thermodynamic system. He constructed a simple box model of the atmosphere which yields surprisingly realistic ...

Den turbulente dynamikken i det øvre havet er et mye omtalt tema av forskere. Tidligere studier har vist seg og støtte to hovedteorier; overflate kvasigeotrofisk teori og to dimensional teori. I denne oppgaven har vi brukt ...

The Arctic Ocean is supplied with water from the Atlantic and Pacific through the Nordic Seas and the Bering Strait. Changes in temperature, salinity and density are seen in the Amundsen, Makarov and Beaufort Basins. The ...

IPCC results indicate that the main bulk of uncertainties on global warming is within aerosol-cloud interactions. Based on observations this thesis aims to measure how anthropogenic aerosol from mid-latitudes increase ...

The polar low in the Norwegian Sea on March 16-17 2008 has been studied using both weather analysis and the numerical weather prediction (NWP) model weather research and forecasting (WRF). This particular polar low was ...

I denne oppgaven har vi studert lavfrekvent variabiliteten i havet gjennom det 20-århundret. I tillegg til observasjoner har vi brukt data fra fire klimamodeller; CCSM3, Gfdl-CM2.0, BCM2.0 og HadCM3, som er kjørt med ...

ERRATA Figure ?? p. 7 refers to Figure 3.1 Figure ?? p. 15 refers to Figure 4.1 Figure ?? p. 17 refers to Figure 4.2 Eq. (4.9) shall read: u_comp = RMS_u sin(fi) Eq. (4.11) shall read NS_vel = u_comp + v_comp For the ...

Extreme mesoscale weather in the Arctic region often forms in the vicinity of the ice edge. A polar low was observed in the region between Svalbard and the ice cap, 8. january 2010. This was the first polar low to have ...

En samling av nedleggelse ordninger for Eddy diffusivities κ, passende for isopycnal diffusjon (Redi 1982) og omrøring (Gent-McWilliams 1990), er testet og sammenlignet med utgang fra høy oppløsning regional havmodell. ...

Relative dispersion is a widely used measure to characterize mixing properties of atmospheric passive tracers. Numerical models allow for a large number of particles. In this thesis, the Lagrangian transport model FLEXPART ...

Regional climate modeling has become an important tool for downscaling global climate models (GCMs), to assess high impact regional climate pro-jections. Southern Africa is one of the most exposed regions to the effects ...

Forskning over de siste ti årene har etablert at dagens bakgrunnskonsentrasjon av bakkenær ozon er høy nok til å ha skadelig effekt på vegetasjon. Disse effektene inkluderer reduksjon i biomasseproduksjon, trevekst og ...

In boundary layer modelling, the Monin-Obukhov theory is widely used to parmeterize the wind profiles and the momentum fluxes. During the IPY-THORPEX campaign at Andøya at 3. March 2008, a flight was made across an arctic ...

Long, non-dispersive coastal wind-generated internal waves in the Hardangerfjord is investigated based on hydrographic data at the coast and current and temperature measurements in the fjord. The aim of the present work ...

We consider the relative importance of wind and currents in the determination of optimal routes, commonly referred to as weather routing, for sailboats. Weather routing for sailboats is the process of finding the fastest ...

Seven experiments are conducted on a coupled ice-ocean model in order to gain insight in the sensitivity of the modeled Arctic sea-ice extent and thickness to crucial changes in the parametrization of the models albedo ...

Forecasting severe weather events is of great importance, especially since it can have impact on life and society. Even though numerical weather prediction (NWP) models have had great improvements in the last decade, some ...

Based on linear shallow water theory for a uniformly rotating, homogeneous ocean, the properties of freely propagating shelf waves are investigated, applying the rigid lid approximation. Applied to the Norwegian shelf, ...

High resolution forecast models have the potential to produce more detailed forecasts of, for example precipitation, than comparable models with a coarser resolution. This is because high resolution forecast models, amongst ...

The growth of the international ship trade has raised the great concern about the impact of the ship emitted pollutants to the clouds and climate, air quality est. Apart from emitting large extents of sulphur dioxide which ...

Forcing perturbations, which are optimal in producing atmospheric respons patterns resembling the Cold-Ocean-Warm-Land (COWL) flow regime over 4 days, have been calculated with the atmospheric Integrated Forecast ...

This thesis presents results from an AGCM sensitivity study in which the response in the Northern Hemisphere storm tracks to an imposed SST anomaly is investigated. The study was motivated by observational studies cited ...

We decided to take a fresh new look at the historical hydrographic data from the Environmental Working Group-atlas (EWG) in light of the recent dramatic changes, first and foremost to shed light on the cause of the large ...

Clouds in the Arctic differ from clouds elsewhere in that they have a net warming effect at the surface. This happens because the longwave (LW) radiation dominates the radiation regime due to large solar zenith angles ...

A short range, limited area ensemble prediction system, LAMEPS, is currently in operational use at the Norwegian Meteorological Institute. It employs 3D-Var for 6 hourly data assimilation cycling for analysis of the control ...

In this thesis, transport pathways, temporal trends and seasonality of persistent organic pollutants (POPs) in the Arctic are examined. These pollutants, which can be transported over long distances, constitute a great ...

Aerosols have in recent years been given increased attention due to their effects on climate and health. Drastic reductions in sulphur emissions in Europe during the last two decades have led to a larger relative importance ...

The heat capacity of the global ocean is very large compared to the rest of the spheres in the climate system of the Earth. It is therefore reasonable to assume that ocean heat uptake or release would manifest itself in ...

Ved å bruke en invers metode kan høydeprofilen av svoveldioksid (SO2) utslippene fra et vulkanutbrudd estimeres. Metoden bruker satellitt observerte SO2 kolonneverdier (AIRS, OMI) og en partikkel dispersjons modell (FLEXPART) ...

Svalbard, ei øygruppe i Arktis, vert påverka både av langtransportert og lokal forureining. I denne oppgåva har konsentrasjonar av elementært karbon (EC) i snøen og effekten det har på albedo blitt undersøkt. Eit overslag ...

This thesis concerns the equilibrium climate response to an anthropogenic change in aerosols since pre-industrial times compared to a 63 % increased CO2 level in the atmospheric GCM CAM-Oslo coupled to a slab ocean model. ...

Initial condition will improve the weather forecast and that is the subject in this master thesis. Will weather observations from aircrat improve the weather prognoses in Norway. Forecast have been made for observings ...

This thesis looks into features of the volume flux in the narrow Drøbak strait, and water level changes in the inner Oslofjord. Earlier measurements suggest that the volum flux in the east course of the strait, calculated ...

In this work we have examined the baroclinic instability in a linear two layer model, where the perturbations are presume to depend the latitude. From the linear equations we have computed the growthrates and speeds of ...