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Disputation: Helene Birkelund Erlandsen

Doctoral candidate Helene Birkelund Erlandsen at the Department of Geosciences, Faculty of Mathematics and Natural Sciences, is defending the thesis Perturbing and constraining Norway's surface water and energy balance for the degree of Philosophiae Doctor.

Photo of Helene Birkelund Erlandsen. Photo: Private

Helene Birkelund Erlandsen. Photo: Private

The PhD defence and trial lecture are fully digital and streamed using Zoom. The host of the session will moderate the technicalities while the chair of the defence will moderate the disputation. A limited number of seats are available in auditorium 1.

Ex auditorio questions: the chair of the defence will invite the audience to ask ex auditorio questions either written or oral. This can be requested by clicking 'Participants -> Raise hand'. 

Trial lecture

Causes and effects of current and future heatwaves over Nordic regions

Conferral summary (in Norwegian)

Mengde vann i norske kraftmagasiner og vårflommer og temperaturen vi opplever er prisgitt vann- og energibalansen på bakken. I avhandlingen belyses hvordan endringer på bakkenivå påvirker atmosfæren over, og omvendt. Ved bruk av en regional klimamodell finner vi at årlig avrenning i Sør-Norge er sensitiv for endringer av sjø-overflatetemperaturen eller hvor tregrensen går. Videre presenteres et høy-oppløst strålings- og fuktighets-datasett for Norge med atmosfæriske variabler som inngår i bakkens vann- og energibalanse. En studie av Norges vannbalanse der stråling og fuktighet benyttes som inngangsdata i en videreutviklet hydrologisk modell, viser at det er usikkerhet i eksisterende estimater for normal nedbør og fordampning.

Main research findings

Popular scientific article about Erlandsen’s dissertation:

Perturbing and constraining Norway's surface water and energy balance

This summer extreme flooding events and wildfires took place worldwide. The interplay of the land surface and atmosphere has been studied for a thousand years.

Illustrasjon: geographie_der_pflanzen_in_den_tropen-landern
Life is both subjected to and interacts with the water and energy balance. Alexander von Humboldt’s 1807 Tableau Physique was an innovative diagram depicting a cross-section of equatorial Andes mountains, showing how plant communities changed with elevation and climate. Figure source WIKIMEDIA COMMONS

Yet, we are still unsure about how changes on the land surface impact the atmosphere and vice versa. Further, present-day models of surface and near-surface variables rely on simplifications. This thesis takes on these issues in three studies, by combining novel model experiments and observational data.

In one study we conducted experiments in a regional climate model centered on South Norway. We perturbed surface features, either forest extent, snow cover, or sea surface temperature (SST). Annual precipitation and runoff were sensitive to both forest extent and SST changes. Another study considers two drivers of the land surface: near-surface humidity and incident radiation. It presents a new method producing a high-resolution data-set of these variables. Exciting estimates and the new data-set were compared with observational data. A limited number of seats are available in auditorium 1.

The new data-set was exploited in a third study. In a gridded hydrological model we allowed snowmelt and evaporation to also react to humidity and radiation. Comparison with previous studies showed uncertainty about Norway's average annual precipitation and evaporation.

Photo and other information:

Press photo: Helene Birkelund Erlandsen, portrait; 500px. Photo: Private

Other photo material: Figure with description and credit as specified in the article above, size 1000px.

Published Sep. 10, 2021 2:22 PM - Last modified Oct. 4, 2021 12:58 PM