Definition

Precipitation duration in hours is used by 100-hr and 1000-hr fuel moisture indices of the NDRFS.
When absent it can be estimated usinga a formula proposed by Bradshaw et al. (1983).

Formula

Bradshaw et al. (1983) proposed to replace the \(P_{Dur}\) as follows:

\[ P_{Dur}= min( 8, \dfrac{P + 0.02)}{p_r}) \]

with the precipitation rate \(p_r\) [inch/h] defined as

\[ p_r = \begin{cases} 0.25, & \mbox{for } Climate {\ 1\ or\ 2} \\ &\\ 0.05, & \mbox{for } Climate {\ 3\ or\ 4} \\ \end{cases} \]

where \(P\) is the 24-hours precipitation in inches and \(Climate \) is the climate class according to Deeming (1977).

References

Literature:
Bradshaw et al. (1983)
Deeming (1977)