Linking global circulation model outputs to regional geomorphic models: a case study of landslide activity in New Zealand

General circulation models (GCMs) were constructed for future projections of circulation patterns on a global scale. IPCC emission scenarios, adopted by GCMs, suggest that climate change is due to anthropogenic emissions of greenhouse gases. Application of GCMs to regionalscale studies is difficult due to the different spatial resolutions. Downscaling techniques transfer GCM results to larger scales. Rainfall-triggered landslides are a worldwide phenomenon and can cause socio-economic problems. Regional models of these geomorphic processes were linked to regionalized GCM outputs for New Zealand. Climate-model outputs from HadCM2SUL were used to produce precipitation and temperature scenarios via analog downscaling. Climate-impact studies have rarely been developed for New Zealand. For both Wellington and Hawke's Bay, climate-change scenarios were applied to 3 deterministic landslide models (the daily rainfall model, the antecedent daily rainfall model and the antecedent soil water status model). All of them relate landslide occurrence to climate conditions. Results give a more reliable projected probability change of landslide occurrence for Wellington than for Hawke's Bay. Wellington's cold-season precipitation is mostly associated with synoptic weather systems depending on large-scale circulation features, captured using the downscaling procedure. In contrast, Hawke's Bay receives its peak precipitation from frequent high-magnitude storms. Common to all 3 applied landslide models for both regions is the trend of decreased landslide activity for the target period, 2070-2099.