Daily and hourly fire risk forecasts - API

These services provide daily and hourly fire risk forecasts. The API for days is available for 6 days and represents the fire risk in the afternoon when the fire risk is usually at its highest. The hourly API describes the fire risk hour by hour for the next 48 hours and thus shows the variation of the fire risk during the day. In the APIs for fire risk analysis there are corresponding calculations but backwards in time, when the fire risk on the current day also depends on how the weather was before, especially with regard to precipitation. SMHI's work with fire risk calculations (forecasts and analyses) is carried out on behalf of the Swedish Civil Defence Agency, formerly the Swedish Civil Contingencies Agency. Calculations of fire risk (forecast and analysis) are made only over land and lakes in Sweden. In both the daily and hourly API, the Canadian Fire Weather Index (FWI) model* is a well-used model both in Europe and abroad. The FWI model is also part of a larger model system for assessing fire risk and fire behaviour called the Canadian Forest Fire Danger Rating System (CFFDRS)**. At SMHI, the daily version of the FWI model was introduced in 1999. The FWI model describes, among other things, fire behaviour, spread rate and the amount of available fuel for the fire in different variables. Inputs for the daily variant of the FWI model are the weather parameters temperature, relative humidity and wind 12 UTC and precipitation 18-18 UTC, from PMP. Inputs for the hourly variant of the FWI model are instead temperature, relative humidity and precipitation for each hour from PMP. Differences between the daily and hourly variants of the FWI model: - The hourly variant uses input data from the daily variant for (DMC, DC, BUI) as these variables do not vary significantly during the day. - In the hourly variant, the humidification/drying speeds are faster than in the daily variant. The daily version ignores the first 0.5 mm, but the hourly version includes all precipitation. - Since the model set and input to the daily and hourly variants are not the same, the different FWI models will get different values even for the time 12 UTC. In addition to the variables of the FWI model, the hourly API also contains: - grass fire risk in the old last year's grass - potential spread rate of a fully developed grass fire in uncut and uncut last year's grass (m/min) (Rn) - global radiation in W/m2 (GLirr). In addition to the variables of the FWI model, the daily API also contains: - the fuel dehydration, which indicates how dehydrated it has become both in the fuel and in the soil layers that are most important in forest fires*** - grass fire risk in the old last year's grass according to the grass fire model on a daily basis - potential spread rate of a fully developed grass fire in uncut and uncut last year's grass (m/min) (Rn) according to the grass fire model on a daily basis. The daily model**** for grass is based on the hourly model***** and uses temperature, precipitation, relative humidity, wind, global radiation (solar radiation) and snow cover as input. The daily model represents the highest grass fire risk during the day, as opposed to the hourly model, which instead describes the grass fire risk for each hour. Development and structure of the Canadian Forest Fire Weather Index System. 1987. Van Wagner, C.E. Canadian Forestry Service, Headquarters, Ottawa. Forestry Technical Report 35. 35 p. https://cfs.nrcan.gc.ca/publications?id=19927 ** https://cwfis.cfs.nrcan.gc.ca/background/summary/fdr *** Fuel dehydration - replacement for HBV forest (2022) Jansson, A https://www.mcf.se/sv/publikationer/bransleuttorkning--ersättare-till-hbv-skog/ **** Development of grass fire hazard model for day and hour forecast (2022) Sjöström, J and Granström, A https://www.mcf.se/sv/publikationer/utveckling-av-modell-for-grasbrandsfara-avseende-prognos-for-dygn-och-timma/ and Snow cover in the grass fire model - Evaluation and implementation (2022) Jansson, A and Böhlin, J https://www.mcf.se/sv/publikationer/snötäcke-i-grasbrandsmodellen--utvärdering-och-implementation/ ***** A new model for grass fire hazard (2021) Sjöström, J., Granström, A, Jansson, A and Böhlin, J https://www.mcf.se/sv/publikationer/en-ny-modell-for-grasbrandsfara-i-sverige/