Title: | Kaukokartoitus lumen vesiarvon seurannan tukena Supporting operational observations of snow water equivalent with remote sensing data |
Author(s): | Moisander, Mikko |
Date: | 2014-06-09 |
Language: | fi |
Pages: | 76+13 |
Major/Subject: | Fotogrammetria ja kaukokartoitus |
Degree programme: | Geomatiikan koulutusohjelma |
Supervising professor(s): | Hagrén, Henrik |
Thesis advisor(s): | Metsämäki, Sari; Sjöblom, Heidi |
Keywords: | lumen vesiarvo, passiiviset mikroaallot, satelliittikaukokartoitus, operatiivinen hydrologia, mallintaminen, AMSR-E, SSM/I, lumilinjat, data-assimilaatio, HUT lumen säteilymalli, snow water equivalent, passive microwaves, satellite remote sensing, operative hydrology, modelling, AMSR-E, SSM/I, snow lines, data-assimilation, HUT snow emission model |
Location: | Archive |
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Abstract: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. |
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