Germany: Forest and Grassland Fire Danger Indices


Forest Fire Danger Index

 

The weather forecasts of the German Weather Service (Deutscher Wetterdienst - DWD) provides an agricultural service which includes the prediction of forest fire danger. 

 

 

After entering the website please navigate to the upper right box where you see a small fire danger map – and click on “mehr”. The main map is the forest fire danger index of the current day. The small maps on the right side provide the forecast for the next 4 days (click on “vergrößern” for the enlarged map. On the left side detailed values of the States (Laender) are provided.

Overview of the Woodland Burning Index (WBI)

During the forest fire season (March to October), the DWD provides forest fire danger forecasts for Germany, which are updated three times a day. (Outside the fire season, the last chart of the previous season continues to be displayed). The operational calculation of the forest fire danger is based on the WBI model. In line with international practice, a scale ranging from 1 to 5 is used to describe the danger of forest fires.

Degree of danger

WBI level

Very low danger

1

Low danger

2

Moderate danger

3

High danger

4

Very high danger

5


Calculation of the Forest Fire Danger

The index uses hourly data of air temperature, relative humidity, wind speed, precipitation, incoming short- and longwave radiation, as well as, at the beginning of the fire season, the daily snow depth measured in the morning. These data are used to estimate the soil moisture and litter moisture content in order to obtain an indication of the amount of flammable fuel. In addition, the rate of spread of the fire line is calculated using a formula from the Canadian Forest Fire Behaviour Prediction System. For assessing the fire intensity, the rate of spread of the fire line is combined with the amount of flammable fuel.  

Forest fire statistics show that the danger level for forest fires depends on the stand type. Therefore, different calculations are made for coniferous forests, mixed forests and deciduous forests using specific soil types and leaf-area indexes.

To represent the mid-afternoon fire peak, a chart of the WBI’s daily maximum between 12 and 18 UTC (13 - 19 CET) is published on the website.
 

Grassland Fire Index (Prototype)

The grassland fire index describes the fire danger for open, unshaded land with dried grass.

After entering the website please navigate to the lower right box where you see a small fire danger map – and click on “mehr”. The grassland fire index describes the fire danger for open, unshaded land with dried grass. The current test version (which is presently being further developed) is a fully automatic computer product which computes hourly time series of various meteorological parameters from approximately 200 stations in the measuring network of the DWD. Like the German WBI for forests, the weather-related fire danger for grassland is classified into five levels:

Classified Levels

level of risk

description

1

  very low risk

2

  low risk

3

  medium risk

4

  high risk

5

  very high risk


Only the 12 UTC value of the index is shown.
 
The grassland fire index takes into account risk-reducing deposits of water due to dew formation, interception of precipitation, or snow, as well as litter moisture and soil humidity (water absorption and evaporation) and the wind speed, which is relevant for the speed of a fire front. At times of high litter moisture and low wind speed or leaf wetness the risk level is low, whereas at times of low litter moisture and high wind speeds the risk level is high.


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