Ice and Snow Cover of Continental Water Bodies from Simultaneous Radar Altimetry and Radiometry Observations

Abstract

We show how the studies of ice and snow cover of continental water bodies can benefit from the synergy of more than 15 years-long simultaneous active (radar altimeter) and passive (radiometer) observations from radar altimetric satellites (TOPEX/Poseidon, Jason-1, ENVISAT and Geosat Follow-On) and how this approach can be complemented by SSM/I passive microwave data to improve spatial and temporal coverage. Five largest Eurasian continental water bodies-Caspian and Aral seas, Baikal, Ladoga and Onega lakes are selected as examples. First we provide an overview of ice regime and history of ice studies for these seas and lakes. Then a summary of the existing state of the art of ice discrimination methodology from altimetric observations and SSM/I is given. The drawbacks and benefits of each type of sensor and particularities of radiometric properties for each of the chosen water bodies are discussed. Influence of sensor footprint size, ice SSM/I stands for Special Sensor Microwave/Imager. roughness and snow cover on satellite measurements is also addressed. A step-by-step ice discrimination approach based on a combined use of the data from the four altimetric missions and SSM/I is presented, as well as validation of this approach using in situ and independent satellite data in the visible range. The potential for measurement of snow depth on ice from passive microwave observations using both altimeters and SSM/I is addressed and a qualitative comparison of in situ snow depth observations and satellitederived estimates is made.

A point-wise least squares spectral analysis (LSSA) of the Caspian Sea level fluctuations, using TOPEX/Poseidon and Jason-1 observations

“…Extreme temperature conditions contribute to the changing Caspian Sea level while the annual component has an amplitude of approximately 20 mm as reported in Swenson and Wahr (2007). A detailed discussion on the ice cover of the Caspian Sea as well as the techniques for detecting them from remote sensing observations are documented, e.g., in Kouraev et al (2003Kouraev et al ( , 2004Kouraev et al ( and 2008.…”

“…Ignatov et al (1993), for example, explained the cause of these fluctuations to be possibly climatic, and that it is dependent on the water budget of its basin (precipitation and river recharge minus water loss by evaporation). Impact of ice coverage changes on the level variations of the Caspian and its detecting using altimetry data sets is discussed, e.g., in Kouraev et al (2003Kouraev et al ( , 2004Kouraev et al ( and 2008. Short-term wind-induced fluctuations are known to cause a rise of up to 4 m, although the average fluctuation is about one meter.…”

Télédétection satellitaire des surfaces enneigées et englacées

“…En effet, le signal altimétrique en bande Ku pénètre la neige à l'inverse du signal en bande Ka (37 GHz) bloqué à la surface, ce qui par différence permet d'obtenir des cartes de neige sur tout l'Arctique. Une méthode similaire a été développée au lac Baïkal pour estimer l'épaisseur de la couverture neigeuse sur la glace à partir des observations micro-ondes passives des altimètres et du radiomètre spatial SSM/I (Kouraev et al, 2008).…”

The Performance of Altimeter Waveform Retrackers at Lake Baikal

“…No attempts were made to isolate or distinguish data points over the lake surface covered by ice or snow from those over water surface in this analysis. However, it should be noted that Kouraev et al (2008) reported a reliable method of ice discrimination in Lake Baikal based on a joint classification of altimeter backscatter coefficient and a radiometer parameter.…”

“…Also, because of calm waters of rivers and lakes, the waveforms often are specular echoes (Gommenginger et al 2011) having a peak amplitude that is significantly increased rendering the retrackers unsuitable based on the Brown ocean model (Brown 1977). Strong peaky echoes are returned also from thin sea-ice (Peacock and Laxon 2004;Kouraev et al 2008).…”