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Author:Moisander, Mikko
Title:Kaukokartoitus lumen vesiarvon seurannan tukena
Supporting operational observations of snow water equivalent with remote sensing data
Publication type:Master's thesis
Publication year:2014
Pages:ix + 75 s.+ liitt, 13      Language:   fin
Department/School:Maankäyttötieteiden laitos
Main subject:Fotogrammetria ja kaukokartoitus   (M3006)
Supervisor:Haggrén, Henrik
Instructor:Metsämäki, Sari ; Sjöblom, Heidi
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201406252232
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Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  1427   | Archive
Keywords:snow water equivalent
passive microwaves
satellite remote sensing
operative hydrology
modelling
snow lines
data-assimilation
HUT snow emission model
lumen vesiarvo
passiiviset mikroaallot
satelliittikaukokartoitus
operatiivinen hydrologia
mallintaminen
AMSR-E
SSM/I
lumilinjat
data-assimilaatio
HUT lumen säteilymalli
Abstract (eng):Snow water equivalent (SWE) is used to measure how much water would form should whole of a snow pack melt instantly at its current location.
Information about snow water equivalent is needed in many applications e.g. flood forecasting, control-ling water level of power plant reservoirs, planning for forestry and crop irrigation and as input and control variable for many environment research purposes including climate change research.
Traditionally snow water equivalent has been measured with in-situ samples or by interpolating weather station observations.
Observation networks however tend to be quite sparse and time intervals between sampling can be long.
Another option to provide information on snow water equivalent is by using space-borne microwave observations.
Satellite instruments make it possible to have observations each day, and thanks to large swath of the instruments, global coverage can be reached within few days.
Standalone radiometer observations can be somewhat imprecise.
Correct interpretation of the brightness temperatures observed by the radiometer requires accurate information on attributes of the snow pack itself, on vegetation cover and about composition of atmosphere over the observed area.
Rarely are all this data available for the entire area observed by the instrument.
To increase the reliability and the accuracy of snow water equivalent estimates, radiometer observations can be assimilated with background information about the spatial distribution of snow depth.
This information can be derived from synoptic weather station network.
In this thesis work the suitability of radiometer data for purposes of the Finnish environment institute's operational observations of snow water equivalent is investigated.
Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and Special Sensor Microwave / Imager (SSM/I) data interpreted with Helsinki University of Technology (HUT) snow emission model and assimilated with snow depth data from Finnish Meteorological synoptic weather stations from years 2011 to 2013 are compared with in-situ observations from Finnish snowline network and with areal snow water equivalents calculated thereof.
Error rates and spatial and temporal distribution of differences in snow water equivalent between products are investigated, and factors affecting the difference and suggestions how to narrow down the difference are given.
Abstract (fin):Lumen vesiarvoa kertoo, kuinka paljon vettä muodostuisi, jos lumikerros sulaisi välittömästi ja kokonaan nykyisellä paikallaan.
Tietoa lumen vesiarvosta tarvitaan muun muassa tulvien enna-koimiseen, vesistöjen pintojen säännöstelyyn, maa- ja metsätalouden suunnitteluun sekä ympä-ristö- ja ilmastotutkimuksen tarpeisiin.
Lumen vesiarvoa mitataan perinteisesti maastohavain-noilla tai interpoloimalla sääasemahavaintoja, mutta havaintoverkot ovat harvoja ja mittausker-tojen välit pitkiä.
Tietoa lumen vesiarvosta voidaan saada myös avaruudesta käsin tehtävillä mikroaaltohavainnoilla.
Satelliitti-instrumenteilla on mahdollista saada havaintoja päivittäin ja kattaa koko maapallo muutamassa päivässä.
Radiometrihavainnot yksinään ovat melko epätark-koja, koska kaikkea havaintojen oikeaan tulkitsemiseen tarvittavaa tietoa on harvoin saatavilla.
Estimaattien tarkkuuden lisäämiseksi radiometrihavainnot voidaan yhdistää sääasemahavain-noista interpoloitavaan taustatietoon lumen vesiarvon spatiaalisesta jakautumisesta.
Tässä työssä on tutkittu radiometrihavaintojen soveltuvuutta Suomen ympäristökeskuksen operatiivisen seu-rantatyön tarpeisiin.
Data-assimilaatioon ja HUT lumen säteilymalliin perustuvia estimaatteja lumen vesiarvosta verrattiin lumilinjoilta tehtyihin maastohavaintoihin sekä näistä laskettuihin lumen aluevesiarvoihin.
Työssä selvitettiin virheen suuruus sekä spatiaalinen ja ajallinen jakau-tuminen vuosina 2011-2013.
Työssä on myös selvitetty eroihin vaikuttavat tärkeimmät tekijät sekä annettu ideoita, miten eri tavalla tuotetut estimaatit lumen vesiarvosta saataisiin lähemmäs toisiaan.
ED:2014-08-03
INSSI record number: 49471
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