@article {bnh-8355, title = {Representing vapour and capillary rise from the soil improves a leaf litter moisture model}, journal = {Journal of Hydrology}, volume = {612}, year = {2022}, month = {06/2022}, abstract = {

Litter moisture content plays a critical role in fire danger rating systems and forest ecosystems. Soil moisture content has been proposed to affect litter moisture due to vapour flux and capillary rise from the soil. However, few models consider soil water content when predicting litter moisture, and to our knowledge, no model includes capillary fluxes. In this study, we represented soil moisture coupling in a physics-based litter moisture prediction model by describing the vapour and capillary fluxes from the soil to litter. We aimed to evaluate if litter moisture predictions can be improved by incorporating the hydrological process at the soil-litter interface and explored the possible role of soil moisture in litter moisture simulations. Three model versions were compared against observations at a dry and wet experimental site in Australia: the original physics-based model, a model version extended with soil vapour flux only, and a version that incorporates both soil vapour flux and capillary rise. The simulation results suggest that soil moisture considerably influences litter moisture through soil vapour flux and capillary rise, which can lead to more than 10\% of oven-dried weight, particularly under wet soil conditions. The corresponding model showed the best performance in comparison with field observations. The contribution of upward soil moisture fluxes was small after long dry and warm periods but noticeable during more moist periods. Further research is needed to evaluate the revised model for a broader range of weather, soil and litter conditions.

}, keywords = {capillary rise, fuel moisture content, leaf litter, Soil moisture, vapour flux}, doi = {https://doi.org/10.1016/j.jhydrol.2022.128087}, url = {sciencedirect.com/science/article/abs/pii/S002216942200662X}, author = {Li Zhao and Marta Yebra and Albert van Dijk and Geoffrey J. Cary} } @article {bnh-7761, title = {The influence of soil moisture on surface and sub-surface litter fuel moisture simulation at five Australian sites}, journal = {Agricultural and Forest Meteorology}, volume = {298-299}, year = {2021}, month = {03/2021}, abstract = {

Fuel moisture content (FMC) of the litter is a critical factor determining fire ignition and spread and is an important input for most fire behaviour prediction models. Several models, ranging from empirical regression functions to physics-based models, have been developed to forecast litter FMC. Soil moisture below the litter layer has been shown to influence litter FMC, but few models explicitly consider its effect. This study aimed to evaluate how soil moisture content may affect litter FMC by coupling soil moisture as a boundary condition to the physics-based {\textquoteleft}Koba{\textquoteright} model, which simulates radiation, energy and moisture fluxes in the surface and subsurface litter layer. The coupled model was tested at five sites in Victoria, Australia, where litter FMC values were recorded continuously during 2014-2015 using calibrated fuel stick sensors. Two versions of the model were compared against the observations: an uncoupled model and a model version accounting for the vapour flux from soil to litter. The simulation results show that the influence of soil moisture depends on environmental conditions. Soil moisture appeared to have a minor influence on FMC when both soil and litter are dry, but a stronger influence when the soil is relatively wet. Correspondingly, the coupled model explained observed FMC better than the uncoupled model for the two wetter study sites. As expected, the subsurface litter in contact with the soil appeared more sensitive to soil moisture conditions than the surface litter. The influence of soil vapour flux on litter FMC can be considerable during the transition from wet to dry litter and soil conditions. This has implications for hazard reduction burning, which is typically planned to take advantage of transitional fuel moisture conditions. Further research is needed to understand the influence of the structure and thickness of litter on the importance of soil vapour flux.

}, keywords = {Coupled model, Dead fuel, forecast, fuel moisture content, Soil moisture}, doi = {https://doi.org/10.1016/j.agrformet.2020.108282}, url = {https://www.sciencedirect.com/science/article/abs/pii/S0168192320303841?dgcid=coauthor}, author = {Li Zhao and Marta Yebra and Albert van Dijk and Geoffrey J. Cary and Stuart Matthews and Gary J. Sheridan} } @article {bnh-5928, title = {Mapping bushfire hazards and impacts annual report 2018-2019}, number = {511}, year = {2019}, month = {09/2019}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This annual report is the output from the Bushfire and National Hazards CRC (BNHCRC), Project A1 {\textquoteleft}Mapping Bushfire Hazard and Impacts{\textquoteright}. It summarises the project objectives, introduces the team members as well as documents the project progress and outcomes during the financial year 2018/2019.

During this financial year we have:

  1. Worked on a comprehensive characterization of fire risk conditions through the integration of fire weather, dead Fuel Moisture Content (FMC) and total biomass into the Australian Flammability Monitoring System (AFMS);
  2. Worked on AFMS website version 3 that incorporated feedback on the trial utilisation of the data service;
  3. Evaluated the feasibility and benefits of the operational use of alternative satellite data in AFMS to ensure long-term data continuity;
  4. Coupled a process-based model that simulates litter fuel moisture and a distributed biophysical model (the Australian Water Resources Assessment system Landscape model) to predict dead fuel moisture content;
  5. Published six journal manuscripts, seventeen conference abstracts and one milestone reports with another one in preparation. We have also had eight appearances in the media;
  6. Hosted two international exchange visits and were approached by more than 30 domestic and international applicants for a PhD scholarship or postdoc position in bushfire research; and
  7. Submitted an application for utilisation funds from the BNHCRC to develop a high-resolution prototype version of AFMS.

Over the next year (2019-2020), this research project will focus on finishing the analysis on the fire risk index as well as using remote sensing data to derive spatial and temporal explicit fuel accumulation curves. In terms of utilization, we will liaise with Geoscience Australia (GA) on transitioning the AFMS as GA has agreed to be in charge of the long term operationalization and maintenance.

}, keywords = {bushfires, fire behavior, fire impacts, hazards, impacts, mapping}, issn = {511}, author = {Marta Yebra and Albert van Dijk and Geoffrey J. Cary and Li Zhao and Honghao Zeng} }