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Effect of active crown fire on the Rate of Spread
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Previous commits computed the occurrence of active crown fire and set
currentCohort%fraction_crown_burned = 1.0_r8

Here I begin to introduce the effects of active crown fire on the size
and intensity of the fire as discussed with @jkshuman in NGEET#573. First
step in this is the effect of active crown fire on the Rate of Spread.

I have confirmed that, with the code changes this far,
history varialbes FIRE_ROS, SUM_FUEL, fire_fuel_bulkd have changed,
while fire size and intensity have not changed. This is what I expected.
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@slevis-lmwg
slevis-lmwg committed Oct 25, 2019
1 parent b762dad commit 9a3fac0
Showing 1 changed file with 67 additions and 19 deletions.
86 changes: 67 additions & 19 deletions fire/SFMainMod.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,7 @@ module SFMainMod

public :: fire_model
public :: fire_danger_index
public :: charecteristics_of_fuel
public :: characteristics_of_fuel
public :: rate_of_spread
public :: ground_fuel_consumption
public :: fire_intensity
Expand Down Expand Up @@ -79,6 +79,9 @@ subroutine fire_model( currentSite, bc_in)

type (ed_patch_type), pointer :: currentPatch

real(r8) :: MEF(nfsc) ! Moisture extinction factor of fuels
real(r8) :: fuel_moisture(nfsc) ! Scaled moisture content of small litter fuels

!zero fire things
currentPatch => currentSite%youngest_patch
do while(associated(currentPatch))
Expand All @@ -94,13 +97,15 @@ subroutine fire_model( currentSite, bc_in)
if( hlm_use_spitfire == itrue )then
call fire_danger_index(currentSite, bc_in)
call wind_effect(currentSite, bc_in)
call charecteristics_of_fuel(currentSite)
call rate_of_spread(currentSite)
call characteristics_of_fuel(currentSite, MEF, fuel_moisture)
call rate_of_spread(currentSite, MEF, fuel_moisture)
call ground_fuel_consumption(currentSite)
call fire_intensity(currentSite)
call area_burnt(currentSite)
call crown_scorching(currentSite)
call crown_damage(currentSite)
call rate_of_spread(currentSite, MEF, fuel_moisture)
! TODO Recalculate area_burnt, FI for altered Scorch Height (SH)
call cambial_damage_kill(currentSite)
call post_fire_mortality(currentSite)
end if
Expand Down Expand Up @@ -157,7 +162,7 @@ end subroutine fire_danger_index


!*****************************************************************
subroutine charecteristics_of_fuel ( currentSite )
subroutine characteristics_of_fuel ( currentSite, MEF, fuel_moisture )
!*****************************************************************

use SFParamsMod, only : SF_val_drying_ratio, SF_val_SAV, SF_val_FBD
Expand All @@ -168,9 +173,12 @@ subroutine charecteristics_of_fuel ( currentSite )
type(ed_cohort_type), pointer :: currentCohort
type(litter_type), pointer :: litt_c

! ARGUMENTS
real(r8), intent(out) :: MEF(nfsc) ! Moisture extinction factor of fuels integer n
real(r8), intent(out) :: fuel_moisture(nfsc) ! Scaled moisture content of small litter fuels

! LOCAL VARIABLES
real(r8) alpha_FMC(nfsc) ! Relative fuel moisture adjusted per drying ratio
real(r8) fuel_moisture(nfsc) ! Scaled moisture content of small litter fuels.
real(r8) MEF(nfsc) ! Moisture extinction factor of fuels integer n

fuel_moisture(:) = 0.0_r8

Expand Down Expand Up @@ -322,15 +330,15 @@ subroutine charecteristics_of_fuel ( currentSite )

enddo !end patch loop

end subroutine charecteristics_of_fuel
end subroutine characteristics_of_fuel


!*****************************************************************
subroutine wind_effect ( currentSite, bc_in)
!*****************************************************************.

! Routine called daily from within ED within a site loop.
! Calculates the effective windspeed based on vegetation charecteristics.
! Calculates the effective windspeed based on vegetation characteristics.
! currentSite%wind is daily wind converted to m/min for Spitfire units

use FatesConstantsMod, only : sec_per_min
Expand Down Expand Up @@ -411,13 +419,15 @@ subroutine wind_effect ( currentSite, bc_in)
end subroutine wind_effect

!*****************************************************************
subroutine rate_of_spread ( currentSite )
subroutine rate_of_spread ( currentSite, MEF, fuel_moisture )
!*****************************************************************.
!Routine called daily from within ED within a site loop.
!Returns the updated currentPatch%ROS_front value for each patch.

use SFParamsMod, only : SF_val_miner_total, &
SF_val_part_dens, &
SF_val_SAV, &
SF_val_drying_ratio, &
SF_val_miner_damp, &
SF_val_fuel_energy

Expand All @@ -426,7 +436,19 @@ subroutine rate_of_spread ( currentSite )
type(ed_site_type), intent(in), target :: currentSite

type(ed_patch_type), pointer :: currentPatch
type(ed_cohort_type), pointer :: currentCohort
type(litter_type), pointer :: litt_c

! ARGUMENTS
real(r8), intent(in) :: MEF(nfsc) ! Moisture extinction factor of fuels
real(r8), intent(in) :: fuel_moisture(nfsc) ! Scaled moisture content of small litter fuels

! LOCAL VARIABLES
real(r8) :: sum_fuel ! value saved for comparison
real(r8) :: leaf_c ! leaf carbon [kg]
real(r8) :: alpha_live_fuel ! ratio of mass fine live fuel to mass total fine fuel (1-hour fuels Rothermal 1972)
real(r8) :: fuel_eff_moist_dead
real(r8) :: fuel_mef_fine
! Rothermal fire spread model parameters.
real(r8) beta,beta_op ! weighted average of packing ratio (unitless)
real(r8) ir ! reaction intensity (kJ/m2/min)
Expand All @@ -442,6 +464,7 @@ subroutine rate_of_spread ( currentSite )
real(r8),parameter :: q_dry = 581.0_r8 !heat of pre-ignition of dry fuels (kJ/kg)

currentPatch=>currentSite%oldest_patch;
litt_c => currentPatch%litter(element_pos(carbon12_element))

do while(associated(currentPatch))

Expand All @@ -454,6 +477,36 @@ subroutine rate_of_spread ( currentSite )
! remove mineral content from net fuel load per Thonicke 2010 for ir calculation
currentPatch%sum_fuel = currentPatch%sum_fuel * (1.0_r8 - SF_val_miner_total) !net of minerals

! ---------------------------------------------------
! Active crown fire effects: https://github.com/NGEET/fates/issues/573
! Update some characteristics of fuel
sum_fuel = currentPatch%sum_fuel ! save for comparison later
if (currentPatch%fire == 1) then
currentCohort=>currentPatch%tallest
do while(associated(currentCohort))
if (currentCohort%active_crown_fire_flg == 1) then
! Add the leaf carbon from each cohort to currentPatch%sum_fuel
leaf_c = currentCohort%prt%GetState(leaf_organ, all_carbon_elements)
currentPatch%sum_fuel = currentPatch%sum_fuel + leaf_c
end if
currentCohort => currentCohort%shorter;
enddo !end cohort loop

! if sum_fuel was indeed updated for a case of active crown fire, go
! on to update currentPatch%fuel_mef and currentPatch%fuel_eff_moist
if (currentPatch%sum_fuel > sum_fuel) then
alpha_live_fuel = (currentPatch%livegrass + leaf_c) / &
(currentPatch%livegrass + leaf_c + sum(litt_c%leaf_fines(:)) + litt_c%ag_cwd(tw_sf))
fuel_eff_moist_dead = sum(currentPatch%fuel_frac(tw_sf:dl_sf) * fuel_moisture(tw_sf:dl_sf))
fuel_mef_fine = currentPatch%fuel_frac(tw_sf) * MEF(tw_sf) + &
currentPatch%fuel_frac(dl_sf) * MEF(dl_sf) + &
currentPatch%fuel_frac(lg_sf) * MEF(lg_sf)
currentPatch%fuel_mef = max((2.9_r8 * ((1.0_r8 - alpha_live_fuel) / alpha_live_fuel) * (1.0_r8 - fuel_eff_moist_dead) - 0.226_r8), fuel_mef_fine)
currentPatch%fuel_eff_moist = exp(-1.0_r8 * currentSite%acc_NI * SF_val_SAV(lg_sf) / SF_val_drying_ratio)
end if
end if
! ---------------------------------------------------

! ----start spreading---

if ( hlm_masterproc == itrue .and.debug) write(fates_log(),*) &
Expand Down Expand Up @@ -888,15 +941,12 @@ subroutine crown_damage ( currentSite )
!returns the updated currentCohort%fraction_crown_burned for each tree cohort within each patch.
!currentCohort%fraction_crown_burned is the proportion of crown affected by fire



type(ed_site_type), intent(in), target :: currentSite

type(ed_patch_type) , pointer :: currentPatch
type(ed_cohort_type), pointer :: currentCohort

real(r8) :: leaf_c ! leaf carbon [kg]
real(r8) :: crown_fuel_bulkd ! leaf biomass per unit area divided by canopy depth [kg/m3] Van Wagner used this method according to Scott (2006) p. 12
real(r8), parameter :: low_heat_of_combustion = 12700.0_r8 ! [kJ/kg]
real(r8), parameter :: critical_mass_flow_rate = 0.05_r8 ! [kg/m2/s] value for conifer forests; if available for other vegetation, move to the params file?
real(r8) active_crown_FI ! critical fire intensity for active crown fire ignition (kW/m)
Expand Down Expand Up @@ -964,25 +1014,22 @@ subroutine crown_damage ( currentSite )
! critical_mass_flow_rate by 3.34, an empirical
! constant in Bessie & Johnson 1995
leaf_c = currentCohort%prt%GetState(leaf_organ, all_carbon_elements)
crown_fuel_bulkd = currentCohort%n * leaf_c / &
currentPatch%fuel_bulkd = currentCohort%n * leaf_c / &
(0.45_r8 * currentCohort%c_area * crown_depth)
active_crown_FI = critical_mass_flow_rate * &
low_heat_of_combustion * currentPatch%sum_fuel / &
(0.45_r8 * 3.34_r8 * crown_fuel_bulkd)
(0.45_r8 * 3.34_r8 * currentPatch%fuel_bulkd)

! Initiate active crown fire?
! EQ 14b Bessie & Johnson 1995
ignite_active_crown = currentPatch%FI / active_crown_FI

if (ignite_active_crown >= 1.0_r8) then
currentCohort%active_crown_fire_flg = 1 ! active crown fire ignited
write(fates_log(),*) 'SF currentCohort%active_crown_fire_flg, crown_fuel_bulkd = ', currentCohort%active_crown_fire_flg, crown_fuel_bulkd ! slevis diag
write(fates_log(),*) 'SF currentCohort%active_crown_fire_flg, currentPatch%fuel_bulkd = ', currentCohort%active_crown_fire_flg, currentPatch%fuel_bulkd ! slevis diag
currentCohort%fraction_crown_burned = 1.0_r8
! TODO Additional effects of active crown fire.
! Currently in code design phase; see
! https://github.com/NGEET/fates/issues/573
else
write(fates_log(),*) 'SF currentPatch%FI < active_crown_FI, crown_fuel_bulkd = ', currentPatch%FI, active_crown_FI, crown_fuel_bulkd ! slevis diag
write(fates_log(),*) 'SF currentPatch%FI < active_crown_FI, currentPatch%fuel_bulkd = ', currentPatch%FI, active_crown_FI, currentPatch%fuel_bulkd ! slevis diag
endif ! ignite active crown fire
else ! crown damage based on scorch height done below
write(fates_log(),*) 'SF currentPatch%FI < passive_crown_FI, height_cbb = ', currentPatch%FI, passive_crown_FI, height_cbb ! slevis diag
Expand Down Expand Up @@ -1014,6 +1061,7 @@ subroutine crown_damage ( currentSite )
currentCohort => currentCohort%shorter;

enddo !end cohort loop

endif !fire?

currentPatch => currentPatch%younger;
Expand Down

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