Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Sikt i snöfall: En studie av siktförhållanden under perioder med snöfall
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
2007 (Swedish)Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The purpose of this thesis is to study the visibility conditions during snowfall events in order to study the possibility of improvement of the visibility forecast currently in use. Measurement data for visibility and precipitation rate was gathered from Storöns automatic weather station at Storön in the Kalix archipelago situated in most northern part of the Bay of Bottnia. The elevation of weather station at Storön is fairly low. Examination of data gathered from the automatic weather station at Storön shows a large degree of scatter in the visibility for a given precipitation rate.

An estimation of visibility function from the gathered data exhibits some discrepancy from the visibility function in the operational model. However this discrepancy is not statistically significant. On comparison with previous studies of the relationship between visibility and precipitation rate, the estimated visibility function was found to be somewhere in the middle of the previous estimates.

In order to try to explain some of the deviation in the measured visibility from the value estimated by the visibility function, three factors were studied. These three were cloud temperature, the average temperature in the layers between ground and approximately 850 hPa and the time/month during the year when the snowfall occurred. The reason behind the choice of these factors were that literature shows that the underlying physics is the same in both the case of visibility reduction due to snowfall and density of freshly fallen snow, and in the latter studies has shown that these factors to some extent explain the variability in snow density. Based on the available data the results never the less show that these factors does not influence the variability of the measured visibility.

Abstract [sv]

Syftet med denna uppsats är att studera siktförhållanden under perioder med snöfall för att undersöka om det finns möjlighet till förbättringar av dagens siktprognoser. Mätdata över sikt och nederbördsintensiteter kom från Storöns automatstation som ligger på en relativt låg ö i Kalix skärgård, i den nordligaste delen av Bottenviken. Undersökningen av mätdata från Storöns automatstation visar på en stor spriding av siktvärden vid givna nederbördsintensiteter. En skattning av siktfunktionen utifrån mätdata gav en viss skillnad jämfört med dagens prognosmodell. Dock var skillnaden inte statistiskt signifikant. Vid en jämförelse med tidigare studier av sikten vid snöfall befanns denna skattning ligga någonstans i mitten av skattade siktfunktioner. I ett försök att förklara en del av avvikelserna från den skattade siktfunktionen studerades huruvida tre faktorer, som visat sig ha betydelse för prognostisering av snödensiteter även påverkade siktvärden. Dessa tre var molntemperatur, medeltemperatur i de lägsta skikten samt när under året snöfallet ägde rum, uppdelat månadsvis. Skälet till att dessa tre faktorer studerades var likheten mellan den bakomliggande fysiken hos siktreduktionen respektive snödensiteten. Både snöns densitet och siktreduktion till följd av snöpartiklar i luften beror på egenskaper hos de enskilda snöflingorna. Resultaten baserade på tillgängliga mätdata gav dock inget stöd för att dessa faktorer även påverkar sikten.

Place, publisher, year, edition, pages
2007.
Series
Examensarbete vid institutionen för geovetenskaper
Keyword [sv]
sikt i snöfall, siktmätningar, siktprognos
National Category
Meteorology and Atmospheric Sciences
Identifiers
URN: urn:nbn:se:uu:diva-303920OAI: oai:DiVA.org:uu-303920DiVA: diva2:974597
Subject / course
Meteorology
Available from: 2016-10-04 Created: 2016-09-27 Last updated: 2016-10-06Bibliographically approved

Open Access in DiVA

fulltext(789 kB)30 downloads
File information
File name FULLTEXT01.pdfFile size 789 kBChecksum SHA-512
31549a241b49e02277dd210fc19a65fcca02ce0227647fa6a4aaa49299de0e786584ee85e4009111ee20c36d0b803c0ecaa361b66d51a83ba22c761e21d516b9
Type fulltextMimetype application/pdf

By organisation
LUVAL
Meteorology and Atmospheric Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 30 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 214 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf