Final Report: The Influence of the North Pacific Jet Stream on Future Fire in California
Dates
Publication Date
2015-09
Citation
Valerie Trouet, Julio L Betancourt, Robert Shepard, Flurin Babst, Soumaya Belmecheri, and Mary Glueck, 2015-09, Final Report: The Influence of the North Pacific Jet Stream on Future Fire in California: .
Summary
Originally, we had two primary objectives for this project: (1) To study North Pacific Jet (NPJ) climatology on interannual to decadal time scales by (a) extending the instrumental NPJ period back in time based on Twentieth Century Re-analysis data and (b) by developing a tree-ring based reconstruction of the winter NPJ position. (2). To analyze the influence of NPJ position on Sierra Nevada (SN) fire regimes. For this purpose, we planned to use historical SN fire regime data to establish a pre-settlement NPJ-fire relationship and recent annual area burned data to determine whether this relationship persists into the 21st century. We have reached objective 1a in a study of twentieth century NPJ climatology (Belmecheri et al. in prep; [...]
Summary
Originally, we had two primary objectives for this project: (1) To study North Pacific Jet (NPJ) climatology on interannual to decadal time scales by (a) extending the instrumental NPJ period back in time based on Twentieth Century Re-analysis data and (b) by developing a tree-ring based reconstruction of the winter NPJ position. (2). To analyze the influence of NPJ position on Sierra Nevada (SN) fire regimes. For this purpose, we planned to use historical SN fire regime data to establish a pre-settlement NPJ-fire relationship and recent annual area burned data to determine whether this relationship persists into the 21st century.
We have reached objective 1a in a study of twentieth century NPJ climatology (Belmecheri et al. in prep; results section a), in which we develop a set of spatially and seasonally explicit jet stream indices across the Northern Hemisphere and relate them to climatological and ecosystem variables.
We had to deviate from our original approach to objective 1b slightly, because we found that a tree-ring based NPJ reconstruction based on existing tree-ring records from CA and the Northern Rockies was not feasible prior to ~1870 CE (see first progress report). We therefore have modified our approach for NPJ reconstruction and in collaboration with Eugene Wahl and Eduardo Zorita have applied a proxy surrogate reconstruction approach to reconstruct the position of the North Pacific Jet back to 1571 CE (Wahl et al. in prep.; results section d). This approach has also allowed us to analyze the influence of NPJ position on historical Sierra Nevada (SN) fire regimes (objective 2).
In addition to the above two objectives, we have leveraged the tree-ring and fire history data compiled in the framework of this project for two additional analyses. We combined the master chronology developed from the CA tree-ring data with an existing winter temperature reconstruction for CA (Wahl et al. 2014) to reconstruct (1500-1980 CE) Sierra Nevada (SN) April 1 Snow Water Equivalent (SWE) (Belmecheri et al. 2016; results section b). We prioritized this research avenue in spring and summer 2015 to provide a timely historical context for the 2015 April 1 SWE record low. Our prioritization paid off, because our work was published in Nature Climate Change in September 2015 and was picked up by a wide range of national and international media outlets (see section 14).
The SN fire history data set is unique in its completeness and allowed us to investigate many aspects of past SN fire regimes, including potential North Pacific Jet links (see results section d), but also socio-ecologically induced fire regime shifts and fire-climate modulations (results section c).
These objectives will allow us, as originally planned, to develop data products (e.g., SN April 1 SWE reconstruction; results section b) and management applications (e.g., projected climate-ecosystem reorganization in SN forests; results section d) that can be translated to fire and fuels managers.
