Sweden: Ground Moisture, Forest and Grass Fire Indices


The Swedish Rescue Services Agency (SRSA) in cooperation with the Swedish Meteorological and Hydrological Institute (SMHI) provides daily updated fire danger maps of Sweden during spring and summer. There are three maps relevant to wildland fire fighting, the grass fire risk map (relevant during spring), the forest fire risk map (relevant during summer) and the ground moisture map.

 


Grass Fire Risk

In Sweden the grass fire risk is present during the grass fire season, in spring after the snow has melted but before new green grass has grown up. The map is found here: http://www.raddningsverket.se/templates/SRV_Page____830.aspx

 


The map has five different colours corresponding to the following conditions:

 

Light grey

Snow covered ground, no grass fire season

Orange

Dead grass from last year may burn if weather conditions cause the grass to dry up. The risk for grass fire is low or moderate. Local variations or rapid changes in the weather may however cause the grass fire risk to alter quickly compared to the prognosis

Red


High risk for grass fire. This prognosis means that the conditions are expected to cause such low moisture content in last years grass that a fire will easily ignite and spread quickly. Local variations or rapid changes in the weather may however cause the grass fire risk to alter quickly compared to the prognosis

Green lines

There is still grass from last year but new green grass has begun to grow. The risk for grass fires decreases as new grass grows in to the old

Green

New green grass has grown up. The risk for grass fires is low



Forest Fire Risk

The Swedish forest fire risk is calculated using the Canadian Fire Weather Index (FWI) system of which more can be read here: http://cwfis.cfs.nrcan.gc.ca/en/background/bi_FWI_summary_e.php

 


The numeric values of the FWI is transformed to six different levels of risk displayed on the forest fire risk map which is found here: http://www.raddningsverket.se/templates/SRV_Page____826.aspx

 


The six levels of forest fire risk are the following: 

1 = Very low fire risk. Corresponds to a FWI value of 0 - 1

2 = Low fire risk. Corresponds to a FWI value of 1 - 6

3 = Normal fire risk. Corresponds to a FWI value of  7 - 16

4 = High fire risk. Corresponds to a FWI value of 17 - 21

5 = Very high fire risk. Corresponds to a FWI value 22 - 27

5E = Extreme high fire risk. Corresponds to a FWI value of 28 or higher 

 


Ground Moisture

The map displays the water content in the upper layer of the ground. It is calculated using a hydrological model, the HBV-model, developed by the Swedish Meteorological and Hydrological Institute. The map is found here: http://www.raddningsverket.se/templates/SRV_Page____818.aspx

 


The map has seven different colours that corresponds to six different ground moisture indexes:

Grey lines = No data available

1 = Very wet

2 = Wet

3 = Moderately wet

4 = Dry

5 = Very dry

5E = Extremely dry

 


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