============================================================================== ============================================================================== Optional input files for Century 4.5. ------------------------------------------------------------------------------ nscale.dat: The optional multipliers on N inputs contained in this file can be used to scale the amount of fertilizer added through FERT events, the amount of atmospheric N deposition, or both. This file is organized in 13 columns. Column 1 is the year. Columns 2 - 13 contain the N input scalars. A value of 1.0 used for a scalar will have no effect on the amount of N input. A value of less that 1.0 used for a scalar will reduce the N input amount. A value of greater than 1.0 used for the scalar will increase the N input amount. A value of less than 0.0 in the nscale.dat file is invalid and the model will use the value of 0.0 for the scalar in this case, in effect eliminating the N inputs. ------------------------------------------------------------------------------ omadscale.dat: The optional multiplier on OMAD inputs contained in this file can be used to scale the amount of organic matter added through OMAD events. This file is organized in 13 columns. Column 1 is the year. Columns 2 - 13 contain the OMAD scalars. A value of 1.0 used for a scalar will have no effect on the amount of organic matter input. A value of less that 1.0 used for a scalar will reduce the organic matter input amount. A value of greater than 1.0 used for the scalar will increase the organic matter input amount. A value of less than 0.0 in the omadscale.dat file is invalid and the model will use a value of 0.0 for the scalar in this case, in effect eliminating the OMAD inputs. ============================================================================== ============================================================================== Code changes for Century 4.5. ============================================================================== Temperature curve change: The temperature effect is now being computed using an arctangent curve, previous versions of the model used an exponential curve. The teff(4) parameter values read from the FIX.100 file are used in the temperature equation. TEFF(1) = "x" location of inflection point TEFF(2) = "y" location of inflection point TEFF(3) = step size (distance from the maximum point to the minimum point) TEFF(4) = slope of line at inflection point The conversion utility assigns the following default values to these parameters. 15.4000 'TEFF(1)' 11.7500 'TEFF(2)' 29.7000 'TEFF(3)' 0.03100 'TEFF(4)' ============================================================================== Non-symbiotic soil N fixation change: Non-symbiotic soil N fixation is now being computed using annual evapotranspiration in place of precipitation. Old equation: non-symbiotic N fixation = epnfs(1) + epnfs(2)*MIN(annual precipitation,100.0) New equation: non-symbiotic N fixation = epnfs(2) * (annual evapotranspiration - epnfs(1)) The conversion utility assigns the following default values for the parameters used in this equation. EPNFS(1) - 30.0000 EPNFS(2) - 0.01000 ============================================================================== Runoff now calculated: Runoff is now calculated and subtracted from the total water (precipitation + irrigation) before water is applied. runoff = MAX(0.0, 0.15 * ((precipitation + irrigation) - 8.0)) ============================================================================== Phosphorus changes: When running a simulation with phosphorus (NELEM >= 2) a back flow calculation for flowing phosphorus from occluded P to secondary P has been added. An additional input parameter, PSECOC2, was added to the FIX.100 file to parameterize the calculation for this flow. The original PSECOC variable in the FIX.100 file retains its original definition but has been renamed PSECOC1. The conversion utility changes the PSECOC variable name to PSECOC1, adds the new PSECOC2 parameter to the FIX.100 file, and sets a default value of 0.0000 for the new PSECOC2 parameter. We have also implemented a check in the code to adjust the C/N ratio of leaves when simulating phosphorus so that the N/P ratio of the leaves does not exceed an observed critical value. The new MAXNP parameter in the TREE.100 file represents this critical value. ============================================================================== Dynamic C allocation: Grassland/crop system - In the grassland/crop system the root to shoot carbon allocation is done as a function of soil water and soil nutrient functions. The new input parameters in the CROP.100 file for controlling dynamic carbon allocation are: FRTCINDX - plant growth type 0 - use Great Plains equation to compute root to shoot ratio (fixed carbon allocation based on rainfall) 1 - perennial plant (i.e., grass, dynamic carbon allocation) 2 - annual plant (i.e., crop, dynamic carbon allocation) FRTC(1) - fraction of C allocated to roots at planting, with no water or nutrient stress, used when FRTCINDX = 2 FRTC(2) - fraction of C allocated to roots at time FRTC(3), with no water or nutrient stress, used when FRTCINDX = 2 FRTC(3) - time after planting (months with soil temperature greater than RTDTMP) at which the FRTC(2) value is reached, used when FRTCINDX = 2 FRTC(4) - maximum increase in the fraction of C going to the roots due to water stress, used when FRTCINDX = 2 FRTC(5) - maximum increase in the fraction of C going to the roots due to nutrient stress, used when FRTCINDX = 2 CFRTCN(1) - maximum fraction of C allocated to roots under maximum nutrient stress, used when FRTCINDX = 1 CFRTCN(2) - minimum fraction of C allocated to roots with no nutrient stress, used when FRTCINDX = 1 CFRTCW(1) - maximum fraction of C allocated to roots under maximum water stress, used when FRTCINDX = 1 CFRTCW(2) - minimum fraction of C allocated to roots with no water stress, used when FRTCINDX = 1 KMRSP(1) - the fraction of net primary production that goes to the maintenance respiration storage pool for crops CKMRSPMX(1) - maximum fraction of aboveground live C that goes to maintenance respiration for crops CKMRSPMX(2) - maximum fraction of belowground live C that goes to maintenance respiration for crops NO3PREF(1) - fraction of N update that is NO3 for crops, currently not being used CLAYPG - number of soil layers used to determine water and mineral N, P, and S that are available for grass/crop growth TMPGERM - germination temperature for the growing degree day submodel, will cause a FRST event when FRTCINDX = 3 or a PLTM event when FRTCINDX = 4 (degrees C) DDHARV - required number of thermal units that need to accumulate to trigger a SENM/HARV event when simulating a grass/crop using the growing degree submodel, FRTCINDX = 3 or 4 TMPKILL - temperature at which growth will stop when using the growing degree day submodel, will cause a SENM and LAST event when FRTCINDX = 3 or a HARV and LAST event if FRTCINDX = 4, if the required number of thermal units has not been accumulated prior to trigger a SENM or a HARV event (degrees C) NOTE: The TMPGERM, DDHARV, and TMPKILL parameters are used by DayCent only but are included in the Century crop.100 file to enable file sharing between the two models. Tree system - In the tree system carbon is allocated to leaves and fine roots first. The allocation to leaves is based on forest type and growing season. For deciduous trees growth occurs only between the months of leaf out and leaf drop. For deciduous and drought deciduous forests all of the C is allocated to leaves during the leaf out period. In tree growth periods that are not identified as leaf out periods carbon is allocated to fine roots first then to leaves, up to a optimum LAI based on large wood biomass. Any leftover C to be allocated after partitioning to leaves and fine roots is then distributed to the woody components, fine branches, coarse roots, and large wood, based on a normalizing of the carbon allocation fractions defined for the tree in the TREE.100 file, FCFRAC(3,*), FCFRAC(4,*), and FCFRAC(5,*). Potential tree production is now controlled by PRCS(2) (formerly PRDX(3)), maximum net forest production, input parameter only, the original PRDX(2) parameter is no longer being used and has been removed from the file. The new input parameters in the TREE.100 file for controlling dynamic carbon allocation are: TFRTCN(1) - maximum fraction of C allocated to fine roots under maximum nutrient stress TFRTCN(2) - minimum fraction of C allocated to fine roots with no nutrient stress TFRTCW(1) - maximum fraction of C allocated to fine roots under maximum water stress TFRTCW(2) - minimum fraction of C allocated to fine roots with no water stress ============================================================================== Maintenance respiration: In addition to heterotrophic respiration from decomposition, RESP(1), Century 4.5 includes submodels to simulate maintenance respiration. A user defined portion of net primary production, NPP, is allocated to the maintenance respiration pool. This pool supplies C for maintenance respiration for above and belowground plant compartments. Respiration for each plant compartment is a function of the mass of the compartment, soil or air temperature, and a user defined maximum respiration parameter. The new input parameters for controlling maintenance respiration in the CROP.100 file are: KMRSP(1) = the fraction of net primary production that goes to the maintenance respiration storage pool for crops CKMRSPMX(1) = maximum fraction of aboveground live C that goes to maintenance respiration for crops CKMRSPMX(2) = maximum fraction of belowground live C that goes to maintenance respiration for crops The new input parameters for controlling maintenance respiration in the TREE.100 file are: KMRSP(2) = the fraction of net primary production that goes to the maintenance respiration storage pool for trees FKMRSPMX(1) = maximum fraction of live leaf C that goes to maintenance respiration for trees FKMRSPMX(2) = maximum fraction of live fine root C that goes to maintenance respiration for trees FKMRSPMX(3) = maximum fraction of live fine branch C that goes to maintenance respiration for trees FKMRSPMX(4) = maximum fraction of live large wood C that goes to maintenance respiration for trees FKMRSPMX(5) = maximum fraction of live coarse roots C that goes to maintenance respiration for trees NOTE: The maintenance respiration code has not been fully tested and validated at this point. There are some inconsistencies in the carbon balance when running the model with the maintenance respiration turned on. Until the maintenance respiration code has been fully tested and validated we recommend that you run your simulations with the maintenance respiration turned off. To do this set the parameter values for KMRSP(*), CKMRSPMX(*), and FKMRSPMX(*) to 0.0. ============================================================================== Changes to the savanna submodel: The SITPOT variable value will be dynamic and will be computed as a function of average annual precipitation. Average annual precipitation is calculated by summing the PRECIP(*) values from the .100 files. For tuning purposes the SITPOT parameter value read from the TREE.100 file for the initial tree will be used as a multiplier. if (arain .lt. 30.0) then sitpot = 1000.0 else if (arain .gt. 80.0) then sitpot = 3500.0 else sitpot = line(arain, 30.0, 1000.0, 80.0, 3500.0) endif sitpot = sitpot * sitpot_m Where: arain = average annual rainfall sitpot_m = sitpot value for initial tree as read from TREE.100 file And: The line function returns the following value: line = (y2 - y1) / (x2 - x1) * (x - x2) + y2 Where: x = arain x1 = 30.0 y1 = 1000.0 x2 = 80.0 y1 = 3500.0 The conversion utility sets all of the SITPOT parameters in a converted TREE.100 file to 1.0 for no multiplicative effect. Volatilization loss that occurs as a function of gross mineralization will be affected by soil texture. The value for VLOSSG is a function of soil texture based on clay content. For tuning purposes the VLOSSG parameter value as read from the FIX.100 file will be used as a multiplier. if (clay .lt. 0.10) then vlossg = 0.03 else if (clay .gt. 0.30) then vlossg = 0.01 else vlossg = line(clay, 0.10, 0.03, 0.30, 0.01) endif vlossg = vlossg * vlossg_m Where: clay = fraction of clay in soil as read from .100 file vlossg_m = vlossg value as read from FIX.100 file And: The line function returns the following value: line = (y2 - y1) / (x2 - x1) * (x - x2) + y2 Where: x = clay x1 = 0.10 y1 = 0.03 x2 = 0.30 y1 = 0.01 The conversion utility sets the VLOSSG parameter in a converted FIX.100 file to 1.0 for no multiplicative effect. If you are simulating a forested system the VLOSSG parameter value should be set between 0.3 and 0.5. We have also modified the way that the tree basal area is being calculated. Old code: wdbmas = (fbrchc + rlwodc) * 2.0 trbasl = wdbmas / basfct New code: wdbmas = (fbrchc + rlwodc) * 2.0 basf = (wdbmas/(0.88 * ((wdbmas * 0.01)**0.635))) if (basf .lt. 250.0) then basf = basf * basfct endif trbasl = wdbmas / basf Where: wdbmas = wood biomass fbrchc = fine branch carbon rlwodc = large wood carbon trbasl = tree basal area basfct = input parameter from TREE.100 file, the value for this input parameter will be given a default value of 1.0 by the conversion utility ============================================================================== Fire code changes for charcoal: There have been changes to fire code so that burning of dead fine branches and dead large wood occurs as a FIRE event rather than a TREM event. The carbon from the burning of the dead fine branches and dead large wood can be returned to the system as charcoal in the passive SOM pool. (See the changes in the FIRE.100 input parameters for more information on how the charcoal return is parameterized.) Removal, by burning, of dead fine branches and dead large wood will no longer be done with a TREM event but will occur as a result of a FIRE event. A TREM fire event will burn only live leaves, live fine branches, and live large wood. A TREM cutting, windstorm or other non-fire event will remove dead fine branches and dead large wood in the same manner as Century 4.0. ============================================================================== Grazing change: The GRET(1) parameter from the GRAZ.100 file is no longer being used. The value for GRET(1) now being used in the model equations is calculated based on soil texture so that the fraction of consumed N that is returned is now a function of clay content. if (clay .lt. 0.0) then gret(iel) = 0.7 else if (clay .gt. 0.30) then gret(iel) = 0.85 else gret(iel) = line(clay, 0.0, 0.7, 0.30, 0.85) endif The line function returns the following value: line = (y2 - y1) / (x2 - x1) * (x - x2) + y2 Where: x = clay x1 = 0.0 y1 = 0.7 x2 = 0.30 y2 = 0.85 ============================================================================== pH effect on decomposition: A pH effect multiplier has been added to the decomposition equations. There are three equations used to simulate bacterial, fungi, and combination pH effects on decomposition flows as follows: SOM1C(1) - combination SOM1C(2) - bacterial SOM2C - fungi SOM3C - fungi METABC(1) - bacterial METABC(2) - bacterial STRUCC(1) - combination STRUCC(2) - combination WOOD1C - combination WOOD2C - combination WOOD3C - combination The user also has the ability to simulate a shift in soil pH content if desired. This is implemented with a change in the schedule file. If the value for PHSYS as read from the schedule file is greater than 0 then the next line in the schedule file contains the start year and end year for the pH effect and then another additional line in the schedule file gives the ending pH amount. The pH in the soil will be ramped from the start value to the end value over the period of years indicated. If the pH shift is not being modeled a value of -1 should be read in for the PHSYS variable. ============================================================================== Potential production calculation change: Potential production is now taking into account the photo period effect on growth. In the fall, when the day length is decreasing, growth will slow down. The definitions for PRDX(1), CROP.100, and PRDX(2), TREE.100, have been changed. These parameters now represent the coefficient used when calculating the potential production as a function of solar radiation outside of the atmosphere. Potential grass/crop production is now being computed in the same manner as potential forest production using an estimate for total production rather than estimating potential aboveground production only. The allocation of aboveground to belowground production for the grass/crop is now based on the fraction of root carbon rather than the root to shoot ratio. We recommend using a value of 0.5 for PRDX(1) and PRDX(2). ============================================================================== Automatic fertilization: Automatic fertilization was not working correctly in earlier versions of Century. Alister Metherell's modifications for the implementing the automatic fertilization option were added to Century 4.5. ============================================================================== Irrigation change: Irrigation will be allowed to occur even on days when the temperature is below freezing. This change was made to allow an irrigated system to reach anerobic conditions evern if the temperature is low. ============================================================================== Changes in snow routines: The snow submodel has been modified so that order of events for snow has been changed from accumulate, melt, sublimate to accumulate, sublimate, melt. We have also added a solar radiation effect to the snow melt equation. This will require you to modify the value of TMELT(2) in your FIX.100 file from the value used by earlier versions of the model. We recommend using a default value of 0.002 for this parameter. ============================================================================== Dynamic value for NLAYPG: The amount of soil water and mineral N, P, and S that is available for plant growth is now based on a dynamic NLAYPG value. Each crop and tree option will have a specific NLAYPG value assigned to them in the CROP.100 (CLAYPG) and TREE.100 (TLAYPG) files. Any time a crop and/or tree option is changed the value for NLAYPG will be recomputed. In a grassland system the value for NLAYPG will be based on the CLAYPG value read for the current crop option from the CROP.100 file. In a forest system the value for NLAYPG will be based on the TLAYPG value read for the current tree option from the TREE.100 file. In a savanna system the value for NLAYPG will be weighted based on the crop/grass LAI, tree LAI, and the CLAYPG and TLAYPG values. The new NLAYPG value is also used for computing soil transpiration. Soil transpiration will occur from the top NLAPYG layers in the soil profile rather than from the full soil profile. The NLAYPG value from the .100 file is no longer being used. ============================================================================== User specified temperatures for leaf out and leaf drop in deciduous trees: There have been two additional variables added to the TREE.100 file to allow the user to specify the temperature values for controlling leaf out, TMPLFS, and leaf drop, TMPLFF, for the specified tree. These temperature values are in degrees C. ============================================================================== Change in PET calculation: The PET calculation is now taking into account solar radition outside of the atmosphere and an approximated cloud cover based on temperature range. As a result of this change the FWLOSS(4) parameter in the FIX.100 file needs to be rescaled. A default value of 0.8 is now recommended for this parameter. ============================================================================== Runoff now calculated with user defined values: There have been two parameters added to the .100 file used for computing the simulated runoff. PRECRO - the amount of monthly rainfall required in order for runoff to occur (cm) (used by monthly Century only) FRACRO - the fraction of the monthly rainfall, over PRECRO, which is lost via runoff (0.0 - 1.0) (used by monthly Century only) The values assigned to this variables in the .100 file replace previous hard coded values in the runoff calculation. Old code: runoff = MAX(0.0, 0.15 * ((precipitation + irrigation) - 8.0)) New code: runoff = MAX(0.0, FRACRO * ((precipitation + irrigation) - PRECRO)) ============================================================================== Fractional volume of rock used to modify field capacity and wilting point: The ROCK parameter has been added to the .100 file and will be used for modifying the AFIEL(*) and AWILT(*) values when SWFLAG is not equal to 0. Set this parameter value to 0.0 to run a simulation with no rock effect on field capacity and wilting point values. ============================================================================== Soil warming experiments can now be simulated: The soil surface temperature warming option allows the user to simulate experiments where the soil surface temperature is warmed without an increase in the minimum and maximum air temperature values. The soil surface warming option is implemented in the same manner the CO2 effect and the pH shift effect options. If the value for stsys as read from the schedule file header is greater than 0 then the next line in the schedule file header contains the start year for the soil surface warming and the following line contains the amount to warm the soil surface temperature in degrees C. ============================================================================== The VOLPL and VOLPLA output variables now include the N that is volatilized from excreted animal waste: In the grazing subroutine we are now calculating the amount of N that is volatilized from excreted faeces and urine. This volatilized N is added to the VOLPL and VOLPLA output variables. ============================================================================== Separate decomposition rates used for surface and soil pools: When using the relative water content option, IDEF = 1 in the FIX.100 file, the model will compute separate values for surface and soil decomposition rates. The water content in the top soil layer will be used for computing decomposition for the surface pools; METABC(1), STRUCC(1), SOM1C(1), WOOD1C, and WOOD2C. A weighted average of the water content in the 2nd, 3rd, and 4th soil layers will used for computing decomposition for the soil pools; METABC(2), STRUCC(2), SOM1C(2), SOM2C, SOM3C, and WOOD3C. In addition this soil decomposition rate will be used in the growth and phosphorous weathering calculations. ============================================================================== Added an option to allow the use of scalars on the N inputs: The optional multiplier on N inputs can be used to scale the amount of fertilizer added through FERT events, the amount of atmospheric N deposition, or both. The optional N scalar option is implemented in the same manner as the CO2 effect, the pH shift effect, and the soil surface warming options. If the value for Nstart as read from the schedule file header is greater than 0 then the next line in the schedule file header contains the start year for the use of the N input scalars. Valid N input scalar options are as follows: 0 - No scalars used 1 - Use scalars on FERT options only 2 - Use scalars on atmospheric N deposition only 3 - Use scalars on both FERT options and atmospheric N deposition The nscale.dat file contains the N input scalars. The file is organized in 13 columns. Column 1 is the year. Columns 2 - 13 contain the N input scalars. A value of 1.0 used for a scalar will have no effect on the amount of N input. A value of less that 1.0 used for a scalar will reduce the N input amount. A value of greater than 1.0 used for the scalar will increase the N input amount. A value of less than 0.0 in the nscale.dat file is invalid and the model will use the value of 0.0 for the scalar in this case, in effect eliminating the N inputs. ============================================================================== Added an option to allow the use of scalars on the OMAD inputs: The optional multiplier on OMAD inputs can be used to scale the amount of organic matter added through OMAD events. The optional OMAD scalar option is implemented in the same manner as the CO2 effect, the pH shift effect, and the soil surface warming options. If the value for OMADstart as read from the schedule file header is greater than 0 then the next line in the schedule file header contains the start year for the use of the OMAD scalars. Valid OMAD input scalar options are as follows: 0 - No scalars used 1 - Use scalars on OMAD options The omadscale.dat file contains the OMAD scalars. The file is organized in 13 columns. Column 1 is the year. Columns 2 - 13 contain the OMAD scalars. A value of 1.0 used for a scalar will have no effect on the amount of organic matter input. A value of less that 1.0 used for a scalar will reduce the organic matter input amount. A value of greater than 1.0 used for the scalar will increase the organic matter input amount. A value of less than 0.0 in the omadscale.dat file is invalid and the model will use a value of 0.0 for the scalar in this case, in effect eliminating the OMAD inputs. ============================================================================== ============================================================================== New output variables in the *.bin output file: AAGDEFAC - average annual value of AGDEFAC, the decomposition factor which combines the effects of temperature and moisture for the surface decomposition (replaces ADEFAC) ABGDEFAC - average annual value of BGDEFAC, the decomposition factor which combines the effects of temperature and moisture for the soil decomposition (replaces ADEFAC) (currently not being used, is equal to AAGDEFAC) AGCMTH(12) - aboveground C production for the grass/crop for the current month, 1-12 (gC/m2) AGCPRD - aboveground C production for the grass/crop over the last completed growing season (gC/m2/y) AGDEFAC - decomposition factor based on temperature and moisture (replaces DEFAC) ANNET - annual evapotranspiration (cm) BGCMTH(12) - belowground C production for the grass/crop for the current month, 1-12 (gC/m2) BGCPRD - belowground C production for the grass/crop over the last completed growing season (gC/m2/y) BGDEFAC - decomposition factor based on temperature and moisture for soil decomposition (replaces DEFAC) (currently not being used, is equal to AGDEFAC) CMRSPFLUX(1) - monthly maintenance respiration flux from aboveground grass/crop material that flows from the grass/crop maintenance respiration storage pool (MRSPSTG(1,*)) to the C source/sink pool (CSRSNK) (gC/m2) CMRSPFLUX(2) - monthly maintenance respiration flux from belowground grass/crop material that flows from the grass/crop maintenance respiration storage pool (MRSPSTG(1,*)) to the C source/sink pool (CSRSNK) (gC/m2) CRTPRD - coarse root component C production for the forest system over the last completed growing season (gC/m2/y) EUPPRD(3) - E uptake by grass, crop, or tree over the last completed growing season (g/m2/y) (1) = N (2) = P (3) = S FBRPRD - fine branch component C production for the forest system over the last completed growing season (gC/m2/y) FCMTH(12) - forest system C production for the grass/crop for the current month, 1-12 (gC/m2) FCPRD - forest system C production over the last completed growing season (gC/m2/y) FERTAC(1) - annual accumulator for N fertilizer (gN/m2) FERTAC(2) - annual accumulator for P fertilizer (gP/m2) FERTAC(3) - annual accumulator for S fertilizer (gS/m2) FMRSPFLUX(1) - monthly maintenance respiration flux from live leaf material that flows from the tree maintenance respiration storage pool (MRSPSTG(2,*)) to the C source/sink pool (CSRSNK) (gC/m2) FMRSPFLUX(2) - monthly maintenance respiration flux from live fine root material that flows from the tree maintenance respiration storage pool (MRSPSTG(2,*)) to the C source/sink pool (CSRSNK) (gC/m2) FMRSPFLUX(3) - monthly maintenance respiration flux from live fine branch material that flows from the tree maintenance respiration storage pool (MRSPSTG(2,*)) to the C source/sink pool (CSRSNK) (gC/m2) FMRSPFLUX(4) - monthly maintenance respiration flux from live large wood material that flows from the tree maintenance respiration storage pool (MRSPSTG(2,*)) to the C source/sink pool (CSRSNK) (gC/m2) FMRSPFLUX(5) - monthly maintenance respiration flux from live coarse root material that flows from the tree maintenance respiration storage pool (MRSPSTG(2,*)) to the C source/sink pool (CSRSNK) (gC/m2) FRTPRD - fine root component C production for the forest system over the last completed growing season (gC/m2/y) MRSPANN(1) - total annual maintenance respiration for grass/crop system (gC/m2/year) MRSPANN(2) - total annual maintenance respiration for forest system (gC/m2/year) MRSPFLOW(1) - maintenance respiration flow to storage pool from grass/crop system (gC/m2) MRSPFLOW(2) - maintenance respiration flow to storage pool from forest system (gC/m2) MRSPSTG(1,1) - unlabeled C in maintenance respiration storage for grass/crop system (gC/m2) MRSPSTG(1,2) - labeled C in maintenance respiration storage for grass/crop system (gC/m2) MRSPSTG(2,1) - unlabeled C in maintenance respiration storage for forest system (gC/m2) MRSPSTG(2,2) - labeled C in maintenance respiration storage for forest system (gC/m2) RLVPRD - leaf component C production for the forest system over the last completed growing season (gC/m2/y) RLWPRD - large wood component C production for the forest system over the last completed growing season (gC/m2/y) RUNOFF - monthly runoff (cm H2O/month) STRMAC(1) - annual accumulator for cm H2O of stream flow (base flow + storm flow) STRMAC(2) - annual accumulator for N from mineral leaching of stream flow (base flow + storm flow) (g/m2) STRMAC(3) - annual accumulator for P from mineral leaching of stream flow (base flow + storm flow) (g/m2) STRMAC(4) - annual accumulator for S from mineral leaching of stream flow (base flow + storm flow) (g/m2) STRMAC(5) - annual accumulator for C from organic leaching of stream flow (base flow + storm flow) (g/m2) STRMAC(6) - annual accumulator for N from organic leaching of stream flow (base flow + storm flow) (g/m2) STRMAC(7) - annual accumulator for P from organic leaching of stream flow (base flow + storm flow) (g/m2) STRMAC(8) - annual accumulator for S from organic leaching of stream flow (base flow + storm flow) (g/m2) TGZRTE(1) - total N returned in faeces and urine from a grazing event (g/m2) TGZRTE(2) - total P returned in faeces and urine from a grazing event (g/m2) TGZRTE(3) - total S returned in faeces and urine from a grazing event (g/m2) TOTSYSC - total system C (AGLIVC + BGLIVC + STDEDC + STRUCC(1) + STRUCC(2) + METABC(1) + METABC(2) + RLEAVC + FROOTC + FBRCHC + RLWODC + CROOTC + WOOD1C + WOOD2C + WOOD3C + SOM1C(1) + SOM1C(2) + SOM2C + SOM3C) (g/m2) TOTSYSE(1) - total N in system (AGLIVE(1) + BGLIVE(1) + STDEDE(1) + STRUCE(1,1) + STRUCE(2,1) + METABE(1,1) + METABE(2,1) + RLEAVE(1) + FROOTE(1) + FBRCHE(1) + RLWODE(1) + CROOTE(1) + WOOD1E(1) + WOOD2E(1) + WOOD3E(1) + SOM1E(1,1) + SOM1E(2,1) + SOM2E(1) + SOM3E(1) (g/m2) TOTSYSE(2) - total P in system (AGLIVE(2) + BGLIVE(2) + STDEDE(2) + STRUCE(1,2) + STRUCE(2,2) + METABE(1,2) + METABE(2,2) + RLEAVE(2) + FROOTE(2) + FBRCHE(2) + RLWODE(2) + CROOTE(2) + WOOD1E(2) + WOOD2E(2) + WOOD3E(2) + SOM1E(1,2) + SOM1E(2,2) + SOM2E(2) + SOM3E(2) (g/m2) TOTSYSE(3) - total S in system (AGLIVE(3) + BGLIVE(3) + STDEDE(3) + STRUCE(1,3) + STRUCE(2,3) + METABE(1,3) + METABE(2,3) + RLEAVE(3) + FROOTE(3) + FBRCHE(3) + RLWODE(3) + CROOTE(3) + WOOD1E(3) + WOOD2E(3) + WOOD3E(3) + SOM1E(1,3) + SOM1E(2,3) + SOM2E(3) + SOM3E(3) (g/m2) VOLEAC - annual accumulator for N volatilization as a function of N remaining after uptake by grass, crop, or tree (g/m2) VOLGAC - annual accumulator for N volatilized as a function of gross mineralization (g/m2) VOLPAC - annual accumulator for N volatilized from plant at harvest, senescence, and/or from grazing removal for grass/crop (g/m2) WD1C2(2) - dead fine branch respiration (g/m2/mo) (1) = unlabeled (2) = labeled WD2C2(2) - dead large wood respiration (g/m2/mo) (1) = unlabeled (2) = labeled WD3C2(2) - dead coarse roots respiration (g/m2/mo) (1) = unlabeled (2) = labeled NOTE: The growing season accumulator values for carbon production (ACRCIS(*), AFBCIS(*), AFRCIS(*), AGCACC, AGCISA(*), ALVCIS(*), ALWCIS(*), BGCACC, BGCISA(*), CRTACC, FBRACC, FCACC, FRTACC, PTAGC, PTBGC, RLVACC, RLWACC) and the growing season accumulator values for E uptake (EUPACC(*), EUPAGA(*), EUPBGA(*), and EUPPRT(*,*)) output for the simulation were being reset to 0.0 at the start of the growing season, when a FRST, PLTM, or TFST event occurred. These production output variables would seem to indicate that production was still occurring because the output variables were not set back to zero at the end of a growing season and would retain a constant value until the next FRST, PLTM or TFST event occurred. These accumulators are now being reset to 0.0 at the end of the simulation timestep in which a LAST or TLST event occurs, after the output for the timestep has been saved to the output file. Old way: Accumulators initialized to 0.0 at start of run Accumulators reset to 0.0 on FRST, PLTM, or TFST and begin accumulation New way: Accumulators initialized to 0.0 at start of run Accumulators begin accumulation on FRST, PLTM, or TFST Accumulators reset to 0.0 on LAST or TLST after output written to file The new growing season production variables, AGCPRD, BGCPRD, CRTPRD, EUPPRD(*), FBRPRD, FCPRD, FRTPRD, RLVPRD, and RLWPRD, are set equal to the value of their associated accumulator value when a LAST or TLST occurs. These values can be used when examining yearly output to see the amount of production that occurred over the previously completed growing season. These growing season production variables will be set back to zero in January if no production has occurred over the previous 12 month period. ============================================================================== ============================================================================== Parameter file changes: Century version 4.0 CROP.100, FERT.100, FIRE.100, FIX.100, TREE.100, and .100 parameter files must be modified to work Century 4.5. Century version 4.0 schedule files must also be modified to work with Century 4.5 A conversion utility, convert100.exe, has been provided to make these file modifications using default values for the modified parameters. ------------------------------------------------------------------------------ CROP.100: The CROP.100 file used by Century version 4.5 has 15 additional parameters: FRTCINDX - plant growth type 0 - use Great Plains equation to compute root to shoot ratio (fixed carbon allocation based on rainfall) 1 - perennial plant (i.e., grass, dynamic carbon allocation) 2 - annual plant (i.e., crop, dynamic carbon allocation) FRTC(4) - maximum increase in the fraction of C going to the roots due to water stress, used when FRTCINDX = 2 FRTC(5) - maximum increase in the fraction of C going to the roots due to nutrient stress, used when FRTCINDX = 2 CFRTCN(1) - maximum fraction of C allocated to roots under maximum nutrient stress, used when FRTCINDX = 1 CFRTCN(2) - minimum fraction of C allocated to roots with no nutrient stress, used when FRTCINDX = 1 CFRTCW(1) - maximum fraction of C allocated to roots under maximum water stress, used when FRTCINDX = 1 CFRTCW(2) - minimum fraction of C allocated to roots with no water stress, used when FRTCINDX = 1 KMRSP(1) - the fraction of net primary production that goes to the maintenance respiration storage pool for crops CKMRSPMX(1) - maximum fraction of aboveground live C that goes to maintenance respiration for crops CKMRSPMX(2) - maximum fraction of belowground live C that goes to maintenance respiration for crops NO3PREF(1) - fraction of N update that is NO3 for crops, currently not being used CLAYPG - number of soil layers used to determine water and mineral N, P, and S that are available for grass/crop growth TMPGERM - germination temperature for the growing degree day submodel, will cause a FRST event when FRTCINDX = 3 or a PLTM event when FRTCINDX = 4 (degrees C) DDHARV - required number of thermal units that need to accumulate to trigger a SENM/HARV event when simulating a grass/crop using the growing degree submodel, FRTCINDX = 3 or 4 TMPKILL - temperature at which growth will stop when using the growing degree day submodel, will cause a SENM and LAST event when FRTCINDX = 3 or a HARV and LAST event if FRTCINDX = 4, if the required number of thermal units has not been accumulated prior to trigger a SENM or a HARV event (degrees C) For reference, here are the definitions for the other FRTC(*) parameters which are also used in the new dynamic carbon allocation routines: FRTC(1) - fraction of C allocated to roots at planting, with no water or nutrient stress, used when FRTCINDX = 2 FRTC(2) - fraction of C allocated to roots at time FRTC(3), with no water or nutrient stress, used when FRTCINDX = 2 FRTC(3) - time after planting (months with soil temperature greater than RTDTMP) at which the FRTC(2) value is reached, used when FRTCINDX = 2 The FRTCINDX, FRTC(*), CFRTCN(*), and CFRTCW(*) parameters are used in the new dynamic carbon allocation routines. FRTCINDX is inserted into the crop parameterization preceding the FRTC(1) parameter. The FRTC(4), FRTC(5), CFRTCN(1), CFRTCN(2), CFRTCW(1), and CFRTCW(2) parameters follow the FRTC(3) parameter. When converting from an existing Century 4.0 CROP.100 file format to a Century 4.5 CROP.100 file format the following rules will be used to set default values for these parameters. 1. If FRTC(1) = 0.0 in the Century 4.0 crop parameterization assume this is a parameterization that should be set to use the Great Plains equation. Set FRTCINDX to 0. 2. If FRTC(1) != to 0.0 in the Century 4.0 crop parameterization then we cannot make an assumption about what this parameterization represents. The user will be prompted to enter a 1 for a perennial plant, or a 2 for an annual plant to set the FRTCINDX value. In all cases FRTC(1), FRTC(2) and FRTC(3) will retain their original Century 4.0 values. FRTC(4) will be set to 0.2, FRTC(5) will be set to 0.1, CFRTCN(1) will be set to 0.4, CFRTCN(2) will be set to 0.25, CFRTCW(1) will be set to the original Century 4.0 FRTC(1) value, and CFRTCW(2) will be set to the original Century 4.0 FRTC(2) value. The KMRSP(1), CKMRSPMX(1), and CKMRSPMX(2) parameters are used in the new maintenance respiration routines. These parameters are give the following values: KMRSP(1) - 0.00000 CKMRSPMX(1) - 0.00000 CKMRSPMX(2) - 0.00000 The NO3PREF(1) parameter is not being used by the model currently but is included in this conversion utility for compatability with anticipated future code changes. The NO3PREF(1) parameter is given a default value of 0.25000. The KMRSP(1), CKMRSPMX(1), and CKMRSPMX(2), and NO3PREF(1) parameters follow the CO2IRS(1) parameter. The CLAYPG parameter is added to each crop option in the crop.100 file following the NO3PREF(1) parameter. It is given a default value of 4. The TMPGERM, DDHARV, and TMPKILL parameters are added to the end of each crop option in the crop.100 file following the CLAYPG parameter. These parameters are given default values of 10.0000, 1500.00, and 7.00000 respectively. These parameters are used by DayCent only but are included in the Century crop.100 file to enable file sharing between the two models. The definition for the PRDX(1) parameter has been changed and each crop option in the crop.100 file should have the value for PRDX(1) set to a default value of 0.5. New Century 4.5 PRDX(1) definition: PRDX(1) - coefficient for calculating potential aboveground monthly production as a function of solar radiation outside the atmosphere ------------------------------------------------------------------------------ FERT.100: The FERT.100 file used by Century version 4.5 has 1 additional parameter: NINHIB - reduction factor on nitrification rates due to nitrification inhibitors added with the fertilizer Using a value of 1.0 for this parameter will have no effect on the nitrification rate. The reduction in nitrification rate will linger for 1 1/2 months after the fertilizer application. The default value for this parameter: NINHIB - 1.00000 NOTE: The NINHIB parameter value is not currently used in Century 4.5 but is added to maintain consistency between Century 4.5 and DayCent 4.5 input files. ------------------------------------------------------------------------------ FIRE.100: The FIRE.100 file used by Century version 4.5 has 11 additional parameters and 3 parameters that have had their "names" changed: FDFREM(3) - fraction of dead fine branches removed by a fire event FDFREM(4) - fraction of dead large wood removed by a fire event FRET(1,1) - fraction of C in the burned aboveground material (live shoots, standing dead, and litter) returned to the system following a fire event as charcoal in the passive SOM pool FRET(1,2) - fraction of N in the burned aboveground material (live shoots, standing dead, and litter) returned to the system following a fire event (NOTE: replaces fret(1)) FRET(1,3) - fraction of P in the burned aboveground material live shoots, standing dead, and litter) returned to the system following a fire event (NOTE: replaces fret(2)) FRET(1,4) - fraction of S in the burned aboveground material (live shoots, standing dead, and litter) returned to the system following a fire event (NOTE: replaces fret(3)) FRET(2,1) - fraction of C in the burned dead fine branch material returned to the system following a fire event as charcoal in the passive SOM pool FRET(2,2) - fraction of N in the burned dead fine branch material returned to the system following a fire event FRET(2,3) - fraction of P in the burned dead fine branch material returned to the system following a fire event FRET(2,4) - fraction of S in the burned dead fine branch material returned to the system following a fire event FRET(3,1) - fraction of C in the burned dead large wood material returned to the system following a fire event as charcoal in the passive SOM pool FRET(3,2) - fraction of N in the burned dead large wood material returned to the system following a fire event FRET(3,3) - fraction of P in the burned dead large wood material returned to the system following a fire event FRET(3,4) - fraction of S in the burned dead large wood material returned to the system following a fire event The FDFREM(3), FDFREM(4), and FRET(1,1) parameters follow the FDFREM(2) parameter. The FRET(1,2) parameter replaces the FRET(1) parameter. The FRET(1,3) parameter replaces the FRET(2) parameter. The FRET(1,4) parameter replaces the FRET(3) parameter. The remainder of the new FRET(*,*) parameters follow the FRET(1,4) parameter. The FRTSH and FNUE(*) parameters follow the FRET(3,4) parameter. The following default values are used for these parameters: FDFREM(3) - 0.30000 FDFREM(4) - 0.20000 FRET(1,1) - 0.10000 FRET(1,2) - retains value of FRET(1) from original file FRET(1,3) - retains value of FRET(2) from original file FRET(1,4) - retains value of FRET(3) from original file FRET(2,1) - 0.00300 FRET(2,2) - 0.20000 FRET(2,3) - 0.00000 FRET(2,4) - 0.00000 FRET(3,1) - 0.00300 FRET(3,2) - 0.20000 FRET(3,3) - 0.00000 FRET(3,4) - 0.00000 ------------------------------------------------------------------------------ FIX.100: The FIX.100 file used by Century 4.5 has 2 additional parameters: TEFF(4) - slope of line at inflection point PSECOC2 - controls the back flow from occluded to secondary P The PSECOC parameter has been renamed PSECOC1 and retains its original definition: PSECOC1 - controls the flow from secondary to occluded P The PSECOC2 parameter follows the PSECOC1 parameter. When running the conversion utility the PSECOC1 parameter retains the value for PSECOC and the following default value is used for PSECOC2: PSECOC2 - 0.00000 Century 4.5 uses 4 coefficients in the equation for computing the temperature effect on decomposition. The TEFF(4) parameter is added to give us the additional coefficient required to paramerterize the temperature equation. The definitions for the TEFF(*) parameters are as follows: TEFF(1) - "x" location of inflection point TEFF(2) - "y" location of inflection point TEFF(3) - step size (distance from the maximum point to the minimum point) TEFF(4) - slope of line at inflection point The TEFF(4) parameter is inserted in the FIX.100 file following the TEFF(3) parameter. When running the conversion utility the following default values are used for the TEFF(*) parameters: TEFF(1) - 15.4000 TEFF(2) - 11.7500 TEFF(3) - 29.7000 TEFF(4) - 0.03100 The PET calculation is now taking into account solar radition outside of the atmosphere and an approximated cloud cover based on temperature range. As a result of this change the FWLOSS(4) parameter in the FIX.100 file needs to be rescaled. A default value of 0.8 is now recommended for this parameter. Due to the changes in the snow melting equation the following default values will be entered for the TMELT(*) parameters: TMELT(1) - 0.00000 TMELT(2) - 0.00200 TMELT(1) retains its original definition. TMELT(2) has been redefined: TMELT(2) - coefficient used for calculating snow melt as a function of solar radiation outside the atmosphere The VLOSSG parameter is now dynamic and will be computed as a function of soil texture based on clay content. The VLOSSG parameter value read from the FIX.100 file is used as a multiplier for tuning this equation. The conversion utility will set the VLOSSG parameter value in a FIX.100 file to 1.0 so there will be no multiplicative effect. ------------------------------------------------------------------------------ TREE.100: The TREE.100 file used by Century version 4.5 has 15 additional parameters: TFRTCN(1) - maximum fraction of C allocated to fine roots under maximum nutrient stress TFRTCN(2) - minimum fraction of C allocated to fine roots with no nutrient stress TFRTCW(1) - maximum fraction of C allocated to fine roots under maximum water stress TFRTCW(2) - minimum fraction of C allocated to fine roots with no water stress MAXNP - maximum N/P ratio for leaves, used only when nelem >= 2 KMRSP(2) - the fraction of net primary production that goes to the maintenance respiration storage pool for trees FKMRSPMX(1) - maximum fraction of live leaf C that goes to maintenance respiration for trees FKMRSPMX(2) - maximum fraction of live fine root C that goes to maintenance respiration for trees FKMRSPMX(3) - maximum fraction of live fine branch C that goes to maintenance respiration for trees FKMRSPMX(4) - maximum fraction of live large wood C that goes to maintenance respiration for trees FKMRSPMX(5) - maximum fraction of live coarse root C that goes to maintenance respiration for trees NO3PREF(2) - fraction of N update that is NO3 for trees, currently not being used TLAYPG - number of soil layers used to determine water and mineral N, P, and S that are available for tree growth TMPLFF - temperature at which leaf drop will occur in a deciduous tree type, degrees C TMPLFS - temperature at which leaf out will occur in a deciduous tree type, degrees C The TFRTCN(*) and TFRTCW(*) parameters are used in the new dynamic carbon allocation routines. TFRTCN(1) is inserted into the tree parameterization following the FCFRAC(5,2) parameter followed by TFRTCN(2), TFRTCW(1), and TFRTCW(2). The TFRTCW(2) parameter and precedes the LEAFDR(1) parameter. When running the conversion utility the TFRTCN(*) and TFRTCW(*) parameters are given the following default values: TFRTCN(1) - 0.40000 TFRTCN(2) - 0.25000 TFRTCW(1) - 0.36000 TFRTCW(2) - 0.30000 The MAXNP, KMRSP(2), FKMRSPMX(1), FKMRSPMX(2), FKMRSPMX(3), FKMRSPMX(4), and FKMRSPMX(5) parameters are used in the new maintenance respiration routines. These parameters are give the following values: MAXNP - 13.5000 KMRSP(2) - 0.00000 FKMRSPMX(1) - 0.00000 FKMRSPMX(2) - 0.00000 FKMRSPMX(3) - 0.00000 FKMRSPMX(4) - 0.00000 FKMRSPMX(5) - 0.00000 The NO3PREF(2) parameter is not being used by the model currently but is included in this conversion utility for compatability with anticipated future code changes. The NO3PREF(2) parameter is given a default value of 0.50000. The MAXNP, KMRSP(2), FKMRSPMX(1), FKMRSPMX(2), FKMRSPMX(3), FKMRSPMX(4), and FKMRSPMX(5) parameters follow the SITPOT parameter. The SITPOT parameter is now dynamic and will be computed as a function of average annual precipitation. The SITPOT parameter value read from the TREE.100 file is used as a multiplier for tuning this equation. This conversion utility will set all of the SITPOT parameter values in a TREE.100 file to 1.0 so there will be no multiplicative effect. The definition for the PRDX(2) parameter has been changed and each tree option in the tree.100 file should have the value for PRDX(2) set to a default value of 0.5. New Century 4.5 PRDX(2) definition: PRDX(2) - coefficient for calculating potential monthly forest production as a function of solar radiation outside the atmosphere The PRDX(3) parameter is no longer being used and has been removed from the tree.100 file. The equation for computing tree basal area has been changed therefore BASFCT is given a a default value of 1.0. The TLAYPG parameter is added to the end of each tree option in the tree.100 file. It is given a default value of 6. The TMPLFF and TMPLFS temperature values are added to the end of each tree option in the tree.100 file. They are given default values of 7.0 and 10.0 respecitively. ------------------------------------------------------------------------------ .100: There have been three parameters added to this file. ROCK - fraction of rock in soil (0.0 - 1.0) PRECRO - the amount of monthly rainfall required in order for runoff to occur (cm) (used by monthly Century only) FRACRO - the fraction of the monthly rainfall, over PRECRO, which is lost via runoff (0.0 - 1.0) (used by monthly Century only) The ROCK parameter is added following the CLAY parameter and is used to modify AFIEL and AWILT values if SWFLAG is not equal to 0. Set this parameter value to 0.0 to run a simulation with no rock effect on field capacity and wilting point values. The PRECRO and FRACRO paramters are added following the STORMF parameter and are used in place of hard coded values for computing the runoff amount in monthly Century. The following default values are assigned to these parameters by the conversion utility: ROCK - 0.00000 PRECRO - 8.00000 FRACRO - 0.15000 The equation for computing the non-symbiotic soil N fixation has been changed. This change requires a modification of the EPNFS(*) parameter values. The following are the default values used for the EPNFS(*) parameters: EPNFS(1) - 30.0000 EPNFS(2) - 0.01000 The WD?LIG parameters are obsolete and need to be removed from the .100 file if necessary. ------------------------------------------------------------------------------ *.SCH (schedule file) changes: The user now has the option of adding comment lines to the top of a schedule file. All of the comment lines must start with a # character and must be stored at the top of the schedule file. There is no blank line permitted between the last comment line and the schedule file header line containing the start year information. Example Century 4.5 schedule file with no comment lines: 1 Starting year 2002 Last year ... Example Century 4.5 schedule file with comment lines: # comment line 1 # comment line 2 # comment line 3 1 Starting year 2002 Last year ... We have added the option to do a shift in soil pH if desired. The pH shift change requires adding additional lines to the schedule file. The pH shift is implemented in much the same manner as the CO2 effect. If the value for PHSYS as read from the schedule file is greater than 0 then the next line in the schedule file contains the start year and end year for the pH effect and then another additional line in the schedule file gives the ending pH amount. The pH in the soil will be ramped from the start value to the end value over the period of years indicated. If the pH shift is not being modeled a value of -1 should be read in for the PHSYS variable. Example Century 4.5 schedule file header excerpt with no pH shift: -1 CO2 Systems -1 pH shift 1 Initial system Example Century 4.5 schedule file header excerpt with pH shift: -1 CO2 Systems 1 pH shift 1990 1991 8.00 1 Initial system The conversion utility will modify an existing Century 4.0 schedule file to add the header line for no pH shift. We have also added an option to simulate soil surface temperature warming experiments where the soil surface temperature is warmed without an increase in the minimum and maximum air temperature values if desired. The soil surface warming option is implemented in the same manner the CO2 effect and the pH shift effect options. If the value for stsys as read from the schedule file header is greater than 0 then the next line in the schedule file header contains the start year for the soil surface warming and the following line contains the amount to warm the soil surface temperature in degrees C. Example Century 4.5 schedule file header excerpt with no temperature warming experiment: -1 CO2 Systems -1 pH shift -1 Soil warming Example Century 4.5 schedule file header excerpt with temperature warming experiment: -1 CO2 Systems -1 pH shift 1 Soil warming 1990 0.5 The conversion utility will modify an existing Century 4.0 schedule file to add the header line for no soil warming experiment. We have added options to allow the user to use a multiplier on the N additions, FERT and/or atmospheric N deposition, and/or OMAD additions to the simulation to scale these additions up and/or down as desired. The scalars are stored in the nscale.dat for FERT and/or atmospheric N deposition. The OMAD scalars are stored in the OMADin.dat file. These two files are optional and if the scalars are not used you do not need to have these files in your working directory. Valid values for the N input scalar option are: 0 - No scalar used 1 - Use scalar on FERT options only 2 - Use scalar on atmospheric N deposition only 3 - Use scalar on both FERT options and atmospheric N deposition If the value read from the schedule file header for the N input scalar is greater than 0 then the next line in the schedule file header contains the year to start reading and using the N scalar values for the nscale.dat file. Valid value for the OMAD input scalar option are: 0 - No scalar used 1 - Use OMAD scalars Example Century 4.5 schedule file header excerpt with no N input or OMAD input scalars: -1 CO2 Systems -1 pH shift -1 Soil warming 0 N input scalar option 0 OMAD input scalar option Example Century 4.5 schedule file header excerpt with N input and OMAD input scalars: -1 CO2 Systems -1 pH shift -1 Soil warming 0 N input scalar option 1975 0 OMAD input scalar option 1975 The conversion utility will modify an existing Century 4.0 schedule file to add the header lines for no N input or OMAD input scalars. The definition of the "output interval" in the block headers in the schedule files has been changed. In previous versions of the model the output interval was represented as the fraction of a year. Monthly output = 0.083 (1/12), yearly output = 1.0, output every 10 years = 10.0, etc. The output interval now represents months and must be entered as an integer value. Monthly output = 1, yearly output = 12, output every 10 years = 120, etc. The conversion utility will modify the output intervals in a schedule file to reflect this change.