AbstractsGeography &GIS

Assessing the availability of remote sensing, hydrological modeling and in situ observations in snow cover research

by Chunyu Dong




Institution: Universität Heidelberg
Department:
Year: 2016
Posted: 02/05/2017
Record ID: 2067224
Full text PDF: http://www.ub.uni-heidelberg.de/archiv/21603;


Abstract

Snow is an important component of the hydrological cycle. As a major part of the cryosphere, snow cover also represents a valuable terrestrial water resource. In the context of climate change, the dynamics of snow cover play a crucial role in rebalancing the global energy and water budgets. Remote sensing, hydrological modeling and in situ observations are three techniques frequently utilized for snowpack investigation. However, the uncertainties caused by systematic errors, scale issues, snow physics limit the availability of the three approaches in snow studies. This dissertation aims at the linkage of the three methods, seeking for a more effective way to understand the spatial-temporal behavior of seasonal snow cover at regional scales. Four case studies have been conducted in the Upper Rhine Region, southwestern Germany. A novel algorithm has been developed to improve the data quality of remotely sensed snow datasets with the help of ground-based meteorological observations. In particular, in situ snow depth measurements were involved into the cloud-gap-filling schemes of MODIS (Moderate Resolution Imaging Spectroradiometer) snow cover products with a conditional probability method. Meteorological filters generated by temperature, precipitation and snow depth data showed high performance in rejecting the overestimation errors of remotely sensed snow maps. A distributed hydrological model (TRAIN) was employed to simulate the seasonal snow cover, which was then validated against the improved cloud-free MODIS snow products and station-derived snow depth data, indicating a well model performance. The long-term trends of the simulated snow water equivalent as well as the recorded air temperature and precipitation were detected using Mann-Kendall trend test and Theil-Sen estimator, which showed a significant snow retreat at the high elevations and an intense warming trend in March during the study period of 1961-2008. Moreover, a snow monitoring network consisting of automatic weather stations, time-lapse photography and manual measurement was applied to reveal the complex snow processes in montane forest environments. Time-lapse photography proved great ability in collecting quantitative snow process information, such as snow canopy interception and blowing snow, suggesting a potential contribution to snow modeling. Finally, it was concluded that a synergistic application of remote sensing, hydrological modeling (with data assimilation) and field observations should be strengthened for the snow cover research in the future. Schnee ist ein wichtiger Bestandteil des Wasserkreislaufs. Als Teil der Kryosphäre ist die Schneedecke eine wertvolle terrestrische Ressource von Wasser. Im Kontext des Klimawandels spielt die Variabilität der Schneedecke eine entscheidende Rolle bei den Veränderungen des globalen Energie- und Wasserhaushalts. Die Fernerkundung, die hydrologische Modellierung und Feldbeobachtungen sind die drei wichtigsten Methoden zur Untersuchung von Schneedecken. Unsicherheiten die durch systematische… Advisors/Committee Members: Menzel, Lucas (advisor).