Interaction of land surface processes and the atmosphere in the Arctic - sensitivities and extremes

• Main Author: Matthes, Heidrun
• Format: Thesis
• Language: unknown
• Published: 2011
• Subjects: albedo; Arctic; Climate change
• Online Access: https://epic.awi.de/id/eprint/32449/; https://hdl.handle.net/10013/epic.41043

For several years, the Arctic has now been in the focus of scientific debate on climate change. It is a region of high spatio-temporal climate variability and additionally a region of high climate sensitivity due to strong feedback processes like the ice-albedo feedback. As there is a strong linkage to the global climate system, changes in the Arctic impact onto the global climate. In modeling the Arctic climate, regional climate models are an important tool because with their high resolution they provide the possibility to account for the horizontally heterogeneous soil and surface characteristics. Here, the regional climate model HIRHAM is used with 25km resolution for the analysis of spatial patterns, variability and trends of the Arctic climate and temperature-derived indices describing climate extremes. Inter-annual temperature variability (ITV) for present-day conditions (1958 to 2008) is examined from station data, the ERA40 re-analysis and HIRHAM results. It shows a pronounced decadal variability and specific regional and seasonal characteristics. Seasonal temperatures in general show warming trends, though they are mostly not statistically significant. Intra-seasonal extreme temperature range (ETR) trends were of mixed sign and only significant from station data over the eastern Russian Arctic. In general, the spatial pattern and magnitude of the Arctic temperature variability, both of seasonal temperature and intra-seasonal ETR, are well reproduced by HIRHAM. The large variability of the Arctic temperature, which is inherent in the analysis period, demonstrates that natural variability is an important factor in the Arctic climate. This variability is not restricted to climate means but also appears in temperature extremes. An analysis of station-derived an re-analysis-based climate indices shows complex behavior, some measures like frost days show consistent decrease (i.e. warming), while others like cold spell days provide a more diverse picture. As with seasonal temperatures, only few trends are ...