Remote sensing of snow at SYKE Sari Metsämäki

Transcription

1 Remote sensing of snow at SYKE Sari Metsämäki

2 Activities in different projects Snow extent product in ESA DUE-project GlobSnow Long term datasets (15-30 years) on Snow Extent (SE) and Snow Water Equivalent (SWE) for climate research purposes. SYKE s SCAmod method for fractional snow cover mapping implemented for Northern hemisphere Based on Envisat/AATSR and ERS-2/ATSR-2 Operational production of fundamantal climate record on snow, implemented and operated by the Finnish Metorological Institute (FMI) Outside mapping area 0% Water 50% Not mapped in product time frame Too low solar angle for snow retrieval Missing or invalid satellite data 100% Fractional snow cover Steps of 1% in product, steps of 10% in colour legend Cloud Snow retrieval algorithm breakdown No snow retrieval algorithm applicable

3 Activities in different projects ESA PolarView Operational production of Fractional snow maps over Baltic Sea Area Based on SCAmod applied to Terra/MODIS

4 Polar View Baltic region snow service processing flow Pre-prosessing Product calculation Data delivery Receiving station End products Internet Data fetching Automatic fetching & archieving Pre-prosessing Unpacking Calibration Athmospheric correction Geocoding Archieving SCA A SCA model Calculation Archiving Cloud masking Automatic Visual verification Hydrological model SCA for 3rd order drainage basins

5 PolarView service at SYKE 2011

6 Polar View Portal

7 Fractional Snow Cover maps by SCAmod Envisat/AATSR Terra/MODIS SYKE SCAmod-method: examples of Fractional snow cover maps on April 2, 2004

8 Fractional Snow Cover maps by SCAmod Terra/MODIS NOAA/AVHRR Apr29, 2006 Apr19, 2008 SYKE SCAmod-method: example of Fractional snow cover maps

9 ( SCA) ( 1 t ) * 2 2 Reflectance model forest t SCA * ( 1 SCA) * snow ground SCA i 1 tˆ 2 i ( SCA) 1 (1 tˆ snow 2 i ) ground forest ground (SCA) snow ground forest tˆ SCA observed reflectance from unit area reflectance for wet snow reflectance for snow-free ground reflectance for forest canopy forest canopy transmissivity for unit area fraction of snow covered area

10 Northern Hemisphere transmissivity map for SCAmod

11 SYKE snow course network A snow course is a 2 to 4 km long trail through various terrains typical of the locality. Each course measured once a month Measurements on snow depth along the trail at locations, with information on land cover type. For density, the snow is weighed at 8 points along the snow course. The fraction of snow-free ground (patchiness) is visually estimated at each snow depth measurement point.

12 Land cover types used in snow course measurement recording 1 open area 2 forest opening 3 forest, pine dominating 4 forest, spruce dominating 5 forest, deciduous dominating 6 open bog

13 Weather station observations by FMI The Finnish Meteorological Institute regularly produces several kinds of observations nearly from 500 locations around the country. The SE related measured parameters: state of ground (e-code) snow depth Daily measurements over several decades Snow e-code Indication 9 dry snow full cover 7 wet snow full cover 6 snow cover more than 50% but less than 100% 5 snow cover less than 50% but more than 0% 4 Open areas snow free, snow exists in forests 3 0% snow cover

14 SCA from RADARSAT-1 Since spring images during spring Augments the optical method Results assimilated to WSFS Method developed at TKK

15 SCA from RADARSAT-1 Spring 2008

16 SWE from microwave radiometer and weather station measurements Assimilation method Data Microwave radiometer data (AMSR-E) Weather station snow depth measurements Microwave emission model Pulliainen, J. Mapping of snow water equivalent and snow depth in boreal and sub-arctic zones by assimilating space-borne microwave radiometer data and ground-based observations, Remote Sens. Environ., vol 101, pp , 2006.

17 Satellite SWE estimation process background info SWE estimate Weather station

18 Interpolated snow depth Snow depth using Ordinary Kriging Interpolation error

19 SWE maps from spring 2009

20 Snow Covered Area on Lake Ice (MODIS-Terra) Snow Covered Area on Lake ice from 8 th, 18 th and 27 th May 2010, lake Inari March 2011 Product Portfolio

21 Snow Covered Area on Lake Ice (MODIS-Terra) Snow Covered Area on Lake ice from March 09, April 12 and May 05, lake Päijänne March 2011 Product Portfolio

22 Ice cover in Lake Laatokka