ESA CCI Research Fellowship: Kristoffer Aalstad

Probabilistic reAnalysis of the Terrestrial Cryosphere by History-matching using Evidence from Satellites (PATCHES)

Fellowship project summary:

Snow, permafrost, and glaciers that together make up the terrestrial cryosphere play a key role in the climate system by regulating the global cycles of energy, water, and carbon. As such, all three of these cryospheric components have been designated the status of Essential Climate Variables (ECVs). Nonetheless, these ECVs are only partially observable using Earth Observation (EO) satellites due to spatio-temporal gaps, sensor noise, and the indirectness of retrieval algorithms. As demonstrated through the initialization of numerical weather predictions and the generation of atmospheric reanalyses, data assimilation presents a natural solution to this problem of partial observability. Data assimilation has nonetheless received relatively little attention from the EO community despite its potential for adding value to satellite data by both filling spatio-temporal gaps and inferring latent ECVs with uncertainty quantification.

PATCHES aims to apply ensemble-based data assimilation techniques so as to improve on existing methods to infer cryospheric ECVs from EO. The main focus is devoted to seasonal snow where accurate snow water equivalent estimation in complex terrain is a central challenge. As such, the primary objective of PATCHES is to provide a high resolution global seasonal snow reanalysis by leveraging the multi-decadal EO snow cover climate data record from the Snow_cci. The envisaged ensemble-based reanalysis workflow in PATCHES can potentially be adapted to permafrost and glaciers, as well as other terrestrial ECVs. The PATCHES project is carried out in close collaboration with both the Permafrost_cci reanalysis team and the Snow_cci EO science team.

Research fellow: Kristoffer Aalstad

Host Institution: Department of Geosciences, University of Oslo