17:15 〜 18:45
[SGD02-P01] GNSSデータの年周変化と積雪深の関係―富山県立山室堂の事例―
キーワード：GNSS、年周変化、積雪、立山、測地学、雪氷学
We investigated the relationship between annual variation of Global Navigation Satellite System (GNSS) data and snow depth in Tateyama Murodo, Toyama (longitude, latitude, and elevation of the area are approximately 137.598°E, 36.578°N, and 2450 m, respectively). We used data from the GNSS Earth Observation Network System (GEONET) station 041138 operated by the Geospatial Information Authority of Japan (GSI) and is located on the building of Murodo Terminal. We used receiver independent exchange (RINEX) formatted data from the station and estimated daily height by precise point positioning with ambiguity resolution (PPP-AR) analysis of Gipsy-X version 1.4 provided by National Aeronautics and Space Administration (NASA) (Bertiger et al., 2020). We then estimated displacements caused by mass loadings due to atmospheric pressure, land water storage, and non-tidal ocean using the International Mass Loading Service (Petrov, 2017). After removing the vertical displacements due to these mass loadings, large annual height changes of 2–3 cm still remain. The cause of this annual height variation is presumed to be heavy snowfall of this region. We also removed tectonic displacement by subtracting a line function connecting average heights of August every year. Besides, snow surveys have been conducted in Tateyama Murodo by University of Toyama (e.g., Aoki and Watanabe, 2009) and Tateyama Caldera Sabo Museum (e.g., Iida et al., 2009). A negative correlation between height changes from August 2006 and snow depths from these surveys is clearly seen. Approximating the relationship by a quadratic function, we obtained y = –4948x2 – 414.6x – 1.177 (where x is the height change from August 2006 [m], and y is snow depth [m]). The coefficient of determination is R2 = 0.80, and the root mean square error (RMSE) is 0.86 m. It can expect to estimate the temporal change using GNSS data in areas of heavy snowfall using the obtained relationship.