Snow covered area estimation using space-borne radar

Tässä työssä tutkitaan TKK:n Avaruustekniikan laboratoriossa kehitetyn lumenpeittoalan estimointimenetelmän tarkkuutta. Tärkeimpänä tavoitteena on menetelmän tilastollisen tarkkuuden selvittäminen. Toissijaisesti tutkitaan myös referenssikuvien valinnan, metsäkompensoinnin, maaston topografian ja satelliitin lentoradan vaikutuksia lumenpeittoalan estimointiin. Menetelmää tutkitaan suorittamalla lumenpeittoalan estimointi 24:lle ERS-2 SAR satelliittikuvalle pohjois-Suomen havumetsävaltaiselle koealueelle. Menetelmän tarkkuuden arviointi suoritetaan vertaamalla saatuja estimointituloksia referenssiaineistoon.An accuracy analysis of the HUT Snow Covered Area estimation method is presented in this work. The main emphasis is to resolve the statistical accuracy of the estimation method. Other studied subjects include the effects of reference image selection, forest compensation, topography and satellite flight path on the SCA estimation method. The method is studied by conducting the SCA estimation for 24 ERS-2 SAR intensity images for the boreal forest dominated test area in Northern Finland. The evaluation of the method is conducted by comparing the SCA estimation results with the available reference data

Remote sensing of snow-cover for the boreal forest zone using microwave radar

This doctoral dissertation describes the development of an operationally feasible snow monitoring methodology utilizing spaceborne synthetic aperture radar (SAR) imagery, intended for hydrological applications on the boreal forest zone. The snow-covered area (SCA) estimation methodology developed is characterized using extensive satellite-based datasets, including SAR-based estimation and optical reference data gathered during the snow-melt seasons of 1997-1998, 2000-2002 and 2004-2006 from northern Finland. The methodology applies satellite-based C-band SAR data for snow monitoring during the spring snow-melt season. The SCA information can be utilized for river discharge forecasting and flood predictions and for the optimization of hydropower production. The development efforts included 1) demonstration of a forest compensation algorithm, 2) establishing the use of wide-swath SAR data 3) development of a weather station assimilation procedure and 4) creation of an enhanced reference image selection algorithm for the SCA estimation methodology. The feasibility of a proposed, non-boreal forest specific, SAR-based SCA estimation method was evaluated for the boreal forest zone. The acquired results were compared with the characteristics determined for the boreal-forest specific methodology developed within this dissertation. These results can be used when selecting appropriate SCA estimation approaches for future snow monitoring systems whether conducted in different regions or intended for larger i.e. continental or global scale purposes. An automatic processing system for SCA estimation was developed and demonstrated as part of this work; the system has been delivered to the Finnish Environment Institute for operational use

Introduction to GlobSnow Snow Extent products with considerations for accuracy assessment

Highlights • GlobSnow Snow Extent provides 17-years data record for Fractional snow cover (FSC). • Snow extent products cover the Northern Hemisphere in 0.01 deg. resolution. • FSC retrieval uses SCAmod method enabling fractional snow mapping also in forests. • Landsat TM/ETM+-based reference is not always representative for validation of FSC

Assessing climate impact indicators:Evaluation criteria and observed strengths and weaknesses

This report documents and reviews a selected set of climate change and impact indicators. They are documented according to reference criteria that were based on a literature study and later refinement in expert discussions. Methodological description, data requirements and availability, treatment of uncertainty, fitness for purpose of indicator time series, and seven other relevant criteria are documented for a total of 81 climate change and impact related indicators. The indicators were grouped into three tiers that reflect their main purpose of use, ranging from change in climate variables to the socio-economic consequences of climate change. A key observation is the limited availability of indicators that explicitly link climate change with socio-economic phenomena. This might be explained by the complexity of the system that hinders quantitative attribution of economic and multi-level societal development to climatic factors. The strengths and weaknesses of indicators are discussed at a general level and also outlined both on an indicator-by-indicator basis and with respect to their potential uses. The report presents a consistent set of criteria and approaches for the incorporation of indicator information into climate information portals. The collected information on climate change and impact indicators can support the development of the Copernicus Climate Services and the indicators that such services will promote

GlobSnow v3.0 snow water equivalent (SWE)

ESA GlobSnow v3.0 snow water equivalent (SWE) dataset. Time series of 1980-2018 Northern Hemisphere terrestrial (non-mountainous) snow water equivalent data, containing monthly and monthly-bias-corrected SWE estimates. Dataset constructed by combining satellite-based passive microwave radiometer data (Nimbus-7 SMMR, DMSP 5D2 SSM/I and DMSP 5D3 SSMIS) with ground based synoptic snow depth observations using bayesian data assimilation, incorporating HUT Snow Emission model; by Pulliainen et al. 1999 (doi:10.1109/36.763302) and Lemmetyinen et al. 2011 (doi:10.1109/TGRS.2010.2041357). SWE retrieval according to Takala et al. 2011 (doi:10.1016/j.rse.2011.08.014) and Pulliainen 2006 (doi:10.1016/j.rse.2006.01.002). Dataset contains monthly SWE data and monthly bias-corrected SWE data. Bias-correction according to Pulliainen et al. 2020 (doi:10.1038/s41586-020-2258-0)

Monitoring Lake Ice Extent on hemispherical scale

An oral presentation about a new method for Lake Ice Extent retrieval for Northern Hemisphere. This method is exploited in provision of 500m Lake Ice Extent Northern Hemisphere (LIE-NH) as one of the cryosphere products in the Copernicus Global Land Service. The LIE-NH product is also available in the Lake Ice Service for Arctic Climate and Safety (https://tarkka.syke.fi/eo-tarkka/map/?ver=0&collectionId=lake_ice_service&lang=en). The presentation introduces also the Lake Ice Service

Monitoring Lake Ice Extent on hemispherical scale

A poster presentation about a new method for Lake Ice Extent retrieval for Northern Hemisphere. This method is exploited in provision of 500m Lake Ice Extent Northern Hemisphere (LIE-NH) as one of the cryosphere products in the Copernicus Global Land Service. The LIE-NH product is also available in the Lake Ice Service for Arctic Climate and Safety (https://tarkka.syke.fi/eo-tarkka/map/?ver=0&collectionId=lake_ice_service&lang=en). The presentation introduces also the Lake Ice Service for Arctic Climate and Safety