# README.txt - Release Notes # # $Id: README.txt,v 5.5 2004/05/07 02:07:23 tbohn Exp $ #------------------------------------------------------------------------ Updates 7-30-2003: VIC 4.1.0 r1 (1) Added support for ASCII as well as Binary state files (NOTE: ASCII state files were added for easier editing when trying to start the model from observed state - Only Binary state files will produce identical runs if used to store and restart from the model state). Added BINARY_STATE_FILE to the global file, if TRUE state file I/O is in binary, if FALSE it is ASCII. (2) Made certain that local NOFLUX flag is set in calc_surf_energy_bal.c every time the routine is executed. (3) write_data.c: Corrected output of sub_snow variable to item [0] rather than a point - will need to decide what parts of this array are important to output. (4) Modified runoff.c so that only the top two layers are used when computing infiltration. Previously, all but the bottom layer was used. Therefore this only affects you if you tried running with more than three layers. This change was made as it makes more sense for a situation where you are trying to improve the representation of the soil column by increasing the resolution (and perhaps depth) of the soil column. (5) snow_utility.c (snow_density): Added check to keep compression from aging from exceeding the actual depth of the snowpack. (6) solve_snow.c: Added check so that MELTING flag is only TRUE if melt occurs in the melt season - currently this is defined between March 1 and October 1. Otherwise the MELTING flag can trigger rapid very early season melt. Updates 4-21-2003: Mering codes to form VIC 4.1.0 r0 ----------------------------------------------------------------------------- From comparison of LatestAdminSource and LatestTestSource Dynamic allocation of as many arrays and structures as are currently used by the VIC model cause electric fence (a memory debugging tool) to bog down/fail in the allocation process. As the allocation of memory is unlikely to be the cause of new memory errors, hard wired memory can be used instead, letting eleectric fence penetrate further into the code. alloc_atmos.c: (KAC) MEMORY_DEBUG update Modified so that dynamic allocation of the atmospheric data arrays does not occur when the debugging code is linked to the model. This makes it possible to use electric fence to debug memory errors without changing the model code. Previously, dynamic allocation of the atmospheric arrays was only skipped if VIC was configured for optimization work. vicNl_def.h: (KAC) MEMORY_DEBUG update See alloc_atmos.c. Newest version of the model had water balance errors when using distributed precipitation. Model crashes were also witnessed. Fixed errors introduced by other model updates. arno_evap.c: (KAC) DIST_PRCP fix Moved unit conversion of moist_resid outside of the distributed precipitation loop. This prevents it from being multiplied by D1 * 1000 twice for the DRY fraction of the grid cell. initialize_model_state.c: (KAC) DIST_PRCP fix Modified to initialize soil and vegetation parameters for the dry grid cell fraction, if distributed precipitation is activated. snow_intercept.c: (KAC) DIST_PRCP fix Added check of intercepted before mass balance error calculation. Since interception quantity can be greater than Wd_max when snow is present, the routine could return dew values higher than maximum in a time step when intercepted snow melted. If there is no other snow, and distributed precipitation is active this could cause the model to crash in redistribute_during_storm as it will be unable to conserve water when too much water is in the canopy. ** Make sure that all updates from surface_fluxes.c are accounted for after merge with 4.0.4beta ** ----------------------------------------------------------------------------- From comparison of LatestAdminSource (updated above) and LaurasNewestSource IceEnergyBalance.c: (LCB) LAKE_WETLAND updates SnowFlux variable renamed to qf to match the lake-ice model documentation. LAKE.h: (LCB) LAKE_WETLAND updates Modified some model parameters (need to check with Laura as to their applicability outside dissertation basins). Also updated profiles for several subroutines. SnowPackEnergyBalance.c: (KAC) OTHER Certain constant definitions have been moved to vicNl_def.h to standardize the location of model constants. This is especially useful for eliminating redundant and unused constant definitions. SnowPackEnergyBalance.c: (LCB) BLOWING_SNOW update New variables are passed to the routine and along to latent_heat_from_snow to add the effects of blowing snow to the accumulation and ablation of the snowpack. calc_surf_energy_bal.c: (LCB) BLOWING_SNOW update Modified to include the effects of blowing snow in the surface energy balance calulations. close_files.c: (LCB) LAKE_WETLAND updates Now closes the lake and wetland debugging file. full_energy.c: (LCB) BLOWING_SNOW updates Modified to handle blowing snow. full_energy.c: (LCB) LAKE_WETLAND updates Modified to output lake model variables during debugging. func_surf_energy_bal.c: (LCB) BLOWING_SNOW updates Modified to handle blowing snow. func_surf_energy_bal.c: (KAC) OTHER Modified so that the calculation of sensible heat flux so that occurs in all model versions. This eliminates a problem in WB mode where sensible heat flux was not set to 0, instead it showed the cumulative sensible heat flux from the snowpack. get_global_param.c: (LCB) BLOWING_SNOW update Added BLOWING_SNOW parameter get_global_param.c: (Jenny?) NEW_ARNO_TYPE Added parameter for reading Bart's new Arno parameters get_global_param.c: (LCB) LAKE_WETLAND updates Added PRT_LAKE parameter to output lake variables during debugging. ice_melt.c: (LCB) LAKE_WETLAND updates Modified method by which lake coverage fraction and ice height are updated? ** Check with Laura ** initialize_global.c: (LCB) LAKE_WETLAND updates Added the initialization of PRT_LAKE to the list of debugging flags. initialize_global.c: (LCB) BLOWING_SNOW update Added initialization of BLOWING_SNOW to the list of global parameters. initialize_lake.c: (LCB) LAKE_WETLAND updates Made improvements to the initialization process for lakes. ** Check with Laura ** initialize_model_state.c: (LCB) LAKE_WETLAND updates Modified to initialize lake variables. initialize_snow.c: (LCB) BLOWING_SNOW update Modified to initalize blowing_snow variable. initialize_soil.c: (LCB) LAKE_WETLAND updates Modified to initialize wetland soil moisture. initialize_veg.c: (LCB) LAKE_WETLAND updates Modified to get the maximum number of vegetation types passed to it. This allows the maximum number of vegetation types to include the wetland vegetation fraction when the lake model is active. lakes.eb.c: (LCB) LAKE_WETLAND updates Modifications were made to improve handling of snow and ice and to make the lake algorithm interact with the wetland algorithm. latent_heat_from_snow.c: (LCB) BLOWING_SNOW update Modified to handle the effects of blowing snow. make_dist_prcp.c: (LCB) LAKE_WETLAND updates Modified to allocate vegetation variables for the wetland vegetation class. make_in_and_outfiles.c: (LCB) OTHER Modified to print notification that the output fluxes file will be in a binary format. open_debug.c: (LCB) LAKE_WETLAND updates Modified to open lake model debugging file. put_data.c: (LCB) LAKE_WETLAND updates Updated output of lake variables to reflect algorithm changes. put_data.c: (LCB) BLOWING_SNOW update Added output variables for blowing snow algorithm. read_lakeparam.c: (LCB) LAKE_WETLAND updates Modified to reflect updates to the lake and wetland algorithms. read_soilparam.c: (JA) OTHER Modified to convert from Bart's new Arno parameters into the standard parameters (Dsmax, Ds, Ws, and c). read_vegparam.c: (LCB) BLOWING_SNOW update Added code to read in blowing snow parameters. snow_melt.c: (LCB) BLOWING_SNOW update Modified to handle blowing snow. soil_conduction.c (set_node_parameters): (KAC) OTHER Modified to correct differences between calculations to determine maximum node moisture and node moisture, so that nodes on the boundary between soil layers are computed the same way for both. soil_conduction.c (distribute_node_moisture_properties): (KAC) OTHER Modified to check that node soil moisture is less than or equal to maximum node soil moisture, otherwise an error is printed to the screen and the model exits. solve_snow.c: (LCB) BLOWING_SNOW update Modified to handle the effects of blowing snow. surface_fluxes.c: (LCB) BLOWING_SNOW update Modified to add the effects of blowing snow. user_def.h: (KAC) SPATIAL_SNOW Added TraceSnow to indicate the minimum depth of new snow required to reset the snow surface albedo from the ablation to the accumulation curve. vicNl.c: (LCB) LAKE_WETLAND updates Updated storage of lake water for water balance calculations. vicNl.h: (LCB,KAC,JA) Updated to reflect model changes. vicNl_def.h: (LCB,KAC,JA) Updated to reflect model changes. water_energy_balance.c: (LCB) LAKE_WETLAND updates Updated to reflect changes in algorithm structure. water_under_ice.c: (LCB) LAKE_WETLAND updates Updated to reflect changes in algorithm structure. write_data.c: (LCB) LAKE_WETLAND updates Updated output of model for lakes and wetlands algorithm. ** No lake variables are output when using LDAS format. ** write_data.c: (KAC) BLOWING_SNOW update Added additional sublimation terms to LDAS and standard snow output files. Added: CalcBlowingSnow.c: (LCB) BLOWING_SNOW update Subroutine to compute the effects of blowing snow on snowpack sublimation. wetland_energy.c: (LCB) LAKE_WETLAND updates Subroutine computes the surface energy balance for exposed wetland vegetation. ----------------------------------------------------------------------------- From comparison of LatestAdminSource (updated above) and SOURCE_4.0.4beta CalcAerodynamic.c: (KAC) CANOPY_ENERGY_BALANCE update This routine was modified to store wind speed, aerodynamics resistance, reference height, roughness lengh and displacement height for three conditions: (1) snow-free, (2) snow-covered and (3) canopy wind speed. SnowPackEnergyBalance.c: No Changes Needed StabilityCorrection.c: (KAC) OTHER Moved definition of G (gravity) to vicNl_def.h to provide a consistant location for all model constants. alloc_atmos.c: No Changes Needed arno_evap.c: No Changes Needed calc_longwave.c: No Changes Needed calc_rainonly.c: Why does version 4.0.4 check to see if MAX_SNOW_TEMP <= MIN_RAIN_TEMP, rather than justt less than as the new version does? Was this a bug or personal preference? ** Check This ** calc_surf_energy_bal.c: (KAC) CANOPY_ENERGY_BALANCE update Modified to work with the canopy energy balance updates. calc_surf_energy_bal.c: (KAC) SPATIAL_FROST update Modified to work with the spatial frost updates. calc_surf_energy_bal.c: (KAC) QUICK_SOLVE update Modified determine the minimum number of soil thermal nodes to capture the maximum amount of the surface energy flux exchange. This reduces solution time with frozen soil significantly, but increases energy balance errors. canopy_energy_bal.c: (KAC) This include changes for spatial snow and frost plus the new canopy energy balance. No notes indicate fixes made to v4.0.4 that need to be incorporated. - converted internal time step accounting to seconds from hours - added check to further restrict evaporative losses if ice content is less than wilting point, otherwise dry soils can evaporate too much if ice is present. check_files: Added lines for lake file check_state_file.c: (KAC) STATE_FILE updates Modified to work with new binary state file, fixed in version 4.0.4. close_files: Added lines for lake file compress_files.c: No changes made Modified to nice the backgrounded file compression processes. dist_prcp.c: (KAC) DIST_PRCP, TREELINE and STATE_FILE updates This will have to be carefully merged, as there are several fixes and improvements which should be maintained. Some of these include fixes to the accounting storms, updates for spatial frost and snow, updates for the state file, updates to account for the treeline. ** This will involve some extra effort, especially since distributed precipitation variables are now account for in several locations. ** --> DRY_TIME and STILL_STORM are now computed separatly for vegetation types, this needs to be incorporated into state file. frozen_soil.c: (KAC) Modified so that soil layer ice content is only calculated if the frozen soil algorithm is implemented and active in the current grid cell. full_energy.c: (KAC) Added lake algorithm, and canopy energy balance updates. Nothing appears to be needed from v4.0.4. func_surf_energy_bal.c: (KAC) updated for spatial snow and frost as well as the canopy energy balance. No important changes in v4.0.4 found. get_global_param.c: (KAC) Nothing new in v4.0.4, all additions are in the admin code. initialize_atmos.c: (KAC) Modified to initialize atmospheric pressues in Pa rather than kPa, all calculations now use Pa eliminating internal conversions. Added treeline calculations. Added output of forcing file statistics (this is in addition to the output of forcing files which was in v4.0.3). initialize_global.c: (KAC) Added initialization of lake variables, blowing snow variables and QUICK_SOLVE for frozen soil energy fluxes. initialize_model_state.c: (KAC) Updated for canopy energy balance, new model state file, and lakes and wetlands algorithm. initialize_new_storm.c: (KAC) Modified to work with spatial frozen soil. initialize_snow.c: (KAC) Modified to initialize blowing snow and spatial snow algorithm variables. make_dist_prcp.c: (LCB) Modified to include wetland variables in the new structures. make_dmy.c: Only white space changes make_in_and_outfiles.c: (KAC) Lake model file control was added mtclim42_vic.c: (KAC) Modified to compute all pressures in Pa rather than kPa. mtclim42_vic.h: (KAC) Definition of EPS constant moved to vicNl_def.h mtclim42_wrapper.c: (KAC) Changed calls to vicrerror to calls to nrerror. Now handles pressure in Pa, rather than kPa. open_state_file.c: (KAC) Updated to handle binary state file. penman.c: (KAC) Now handles pressure in Pa, rather than kPa. prepare_full_energy.c: (KAC) modified so that ice content is set to zero unless the frozen soil algorithm is implemented and active in the current grid cell. put_data.c: (KAC) modified to incorporate the effects of treeline calculations, the lake and wetland algorithm, spatial snow and frost algorithms, and the canopy energy balance. read_atmos_data.c: (KAC) v4.0.4 multiplies nrecs by NF to check for a long enough file, v.4.1.0 multiples by dt. I think new version is probably correct. read_initial_model_state.c: (KAC) Updated to handle binary state file. Need to address storm state variables! read_snowband.c: (KAC) Modified to allocate treeline variable. Will need to update to fix lake model/snow band problem! read_soilparam.c: (KAC, JA) Modified to read in spatial snow and frost parameters and to read in Bart's new Arno parameter set. read_soilparam_arc.c: (KAC) Modified to read in spatial snow and frost parameters and to read in Bart's new Arno parameter set. read_vegparam.c: (DP,KAC) Modified code to update Wdmax based on LAI values read in for the current grid cell. If LAI is not obtained from this function, then the values cacluated in read_veglib.c are left unchanged. redistribute_during_storm.c: (KAC) Modified to work with distributed snow and frozen soil. runoff.c: (KAC) Modified to handle spatial snow and soil frost. snow.h: (KAC) Added minimum SWQ for computing snow pack energy balance. Added coefficients of shortwave attenuation through the snowpack. Removed minimum SWQ for full coverage, now included in the soil files. snow_intercept.c: (KAC) Modified to handle new variables required to close the canopy energy balance. snow_melt.c: (KAC) Modified to handle partial snow cover. Modified to assure that ground heat flux is used properly in the snow surface energy balance as well as imporving the handling of energy fluxes for partial snow cover. Modified to handle blowing snow. snow_utility.c: (KAC) Moved definition of G to vicNl_def.h. soil_conduction.c: (KAC) set_node_parameters: Modified to correct differences between calculations to determine maximum node moisture and node moisture, so that nodes on the boundary between soil layers are computed the same way for both. distribute_node_moisture_propertes: Modified to check that node soil moisture is less than or equal to maximum node soil moisture, otherwise an error is printed to the screen and the model exits. estimate_layer_ice_content: Modified to find ice content in spatial frost bands. solve_snow.c: (KAC) - Added partial snow cover and advection of sensible heat from local bare patches. - Modified to pass the minimum depth of full snow cover as a variable in soil_con rather than a globally defined constant. - Fixed check of new snow accumulation for setting understory flag to use snowfall[WET] not snowfall. - Set MELTING flag to maintain melting albedo curve even during brief periods of refreezing, until a snowfall exceeds SnowThres. - Modified to handle the effects of blowing snow. - Modified to handle closed canopy energy balance. surface_fluxes.c: (KAC) - Modified to handle partial snow cover. - Modified to iterate a solution for the exchange of energy between the snowpack and the ground surface. - Modified to add the effects of blowing snow. - Fixed indexing problem for sub-daily snow model within daily water balance VIC: hour (now hidx) is incremented by 1 rather than the sub-daily time step, so the atmospheric forcing data is now properly indexed. - Indexing fix sent SNOW_STEP to calc_surf_energy_bal rather than the model time step, meaning that without snow the evaporation was computed for SNOW_STEP hours rather than a full day. This was fixed by introducing step_inc to index the arrays, while step_dt keeps track of the correct time step. svp.c: (KAC) Modified internal calculations to use kPa rather than Pa for consistancy user_def.h: (KAC) Added options for lake model, closing the canopy energy balance, computing the treeline, computing statistics from the input forcings, and controls for spatial snow and frost. vicNl.c: (KAC) - Added controls for lake model. - Updated storage of lake water for water balance calculations. - Modifed to add AboveTreeLine to soil_con_struct so that the model can make use of the computed treeline. - Modified to initialize storm parameters using the state file. - Modified to start the model by skipping records until the state file date is found. This replaces the previous method of modifying the global file start date, which can change the interpolation of atmospheric forcing data. - Modified to store wet and dry fractions when intializing water balance storage. This accounts for changes in model state initialization, which now stores wet and dry fractions rather than just averaged values. vicNl.h: (KAC) Added definitions for treeline and forcing stats subroutines and made some needed modifications to subroutine definitions due to other changes, however, other changes still need to be made. vicNl_def.h: (KAC) Modified to handle lake algorithm, blowing snow, spatial snow and frost, and treeline calculations. write_data.c: (KAC) - Made hour a variable in all output data file formats even if the model is run at a daily time step. Also modified all output files to account for new variables introduced by the spatial frost and snow algorithms, the lake algorithm and the PILPS 2e study. - Added energy fluxes to snow band output files. - Updated output of model for lakes and wetlands algorithm. Added output of blowing snow sublimation to LDAS and standard snow output files. ** No Lake Variables are included in the LDAS output format. ** - Modified LDAS SWQ output, so that it is multiplied by 10 instead of 100 before being converted to a short integer. This reduces stored value precision to 0.1, but increases the maximum storable SWQ, which was exceeded in previous LDAS simulations. - Eliminated different formats between energy balance and water balance model output. write_debug.c: (KAC) Modified to work with closed canopy energy balance. write_forcing_file.c: (KAC) Modified to output pressures, which are handled internally in kPa, as Pa for backward compatability. write_layer.c: (KAC) Modified to handle spatial soil frost. write_model_state.c: (KAC) - Rewritten to handle updates to vicNl_def.h and to write the file as binary to minimize write time and differences with simulations started with the state file. - Model is now restarted with the correct values for mu and LAST_STORM. ** Still need to account for differences with distributed precipitation flags, which now differ with vegetation - also need to check storage of lake variables, blowing snow variables and MELTING flag. ----------------------------------------------------------------------------- June 4, 2003: VIC release 4.0.4beta r2 This covers bugs found during tests with the snow algorithm. solve_snow.c: Bug found by KAC Counter for number of days since last snowfall was incremented twice in the MELTING update. This has been fixed. solve_snow.c: modification by KAC Added check so that MELTING flag is only TRUE if melt occurs in the melt season - currently this is defined between March 1 and October 1. Otherwise the MELTING flag can trigger rapid very early season melt write_model_state.c, read_initial_model_state.c, open_state_file.c, check_state_file.c: Modification by KAC Modified to handle both ASCII and BINARY state files. NOTE: ASCII mode is designed to make it easier to create a state file for initializing a point model. It includes all features of the Binary state file, but values are truncated so the resulting restart will not be identical. If you need an exact restart, use the Binary files. Also removed ice content from the state file as it is computed at the beginning of each time step, so storing its value is unnecessary. ----------------------------------------------------------------------------- April 23, 2003: VIC release 4.0.4beta r1 This covers bug fixes found by beta testers and fixed in the version of the code bundled with this file. surface_fluxes.c: (found by Ingjerd Haddeland) Indexing fix sent SNOW_STEP to calc_surf_energy_bal rather than the model time step, meaning that without snow the evaporation was computed for SNOW_STEP hours rather than a full day. This was fixed by introducing step_inc to index the arrays, while step_dt keeps track of the correct time step. ----------------------------------------------------------------------------- March 27, 2003: VIC release 4.0.4beta This release covers patches for several bugs found in 4.0.3, which were never formally released (i.e. the downloadable source code was modified, but no major announcement was made). It also includes other fixes and modifications that have been identified as being needed prior to releasing version 4.1.0, which will involve several significant changes (including lakes & wetlands, spatial snow & frost, and a closed canopy energy balance). Modifications: Snow albedo update: (found by Keith) In previous releases, the snow albedo function has been hyper sensitive to trace amounts of snowfall during the melt period. Whenever new snow falls or the cold content falls below 0, the albedo is switched from the ablation curve to the accumulation curve. This curve is then followed until the cold content exceeds 0, indicating it is in the spring melt season. This is fine when accounting for thin early season snowpacks or mid- season melt events, however, a cold snap or light dusting of snow should not reset the snowpack albedo to much higher winter values for days or weeks at a time. This release of the model monitors the state of pack with the variable MELTING. This flag keeps the snowpack on the ablation curve unless new snow- fall exceeds a threshold (TraceSnow in user_def.h) indicating that the top of the snowpack should be represented by the albedo of the new snow. Model initialization: (found by Ulysses and Keith) In previous releases, the initialization of soil layer moist[] and ice[] was within a second set of loops for band and vegetation, using the same counters. Because of the dual use of counters, initialization was not completed correctly. The primary effect of this was that thermal node values beyond the first vegetation type were not correctly initialized, which caused the model to crash during some simulations with full energy or frozen soils active. Without frozen soil, most simulations would compensate for the problem within their spin-up time, so it is unlikely that this bug impacts any simulations not employing frozen soil. Snow time step: (found by Andy, et al.) The snow algorithm needs to run sub-daily for the energy balance components to function properly. This means that for daily simulations, the snow model must be solved at a finer (sub-daily) time step. In the previous release, initialize_atmos.c stored sub-daily met data in each days variable using positions (e.g. 0,1,..8 for 3 hour data). In surface_fluxes.c the model indexed the sub-daily time steps used by the snow algorithm with hours (e.g. 0,3,6,...21 for three hour data). This means the arrays were incorrectly indexed and the resulting model simulations would be wrong. The fix implemented here has been tested under several model configurations and is deemed the official version. WARNING: There are several versions of this fix circulating, please update your code to this version - the previous fixes may not work in all circumstances! FROZEN_SOIL active flag: (found by Ed and Justin) The cause of the problem is a bug in the code that occurs when the global frozen soils flag (FROZEN_SOILS) is set to true but the individual cell frozen soil flag (FS_ACTIVE) is set to false. This causes the change in soil heat storage to be calculated incorrectly. This was fixed by adding additional conditions within frozen_soil.c and initialize_model_state.c, which verify the FS_ACTIVE is TRUE before running estimate_layer_ice_content. This avoids the problem of the soil layer ice content being set to a positive value, ignored by the rest of the model. Vapor pressure: (Keith) All internal vapor pressure calculations are now done in Pascals. Previous release versions, switched between Pa and kPa, so this simply removes the extra step. The input file format is unchanged, so there should be no change to model output (model might run slightly faster, but it is also unlikely that this will be witnessed by a normal user). Constant dew despite changing LAI: (Dave Peterson) The modification of read_vegparam.c to update LAI based on a grid cell specific value did not change the values of Wdmax. Wdmax values were computed in read_veglib.c based on the default LAI values, so they did not necessarily reflect the actually LAI values used for the grid cell. Values for Wdmax are now computed in read_vegparam.c whenever GLOBAL_LAI are provided. The effects of this change will change in magnitude based on how different the cell LAI values are from those in the default library file. DRY_TIME error: (Reinur Schnur) DRY_TIME in dist_prcp.c was incremented by the time step in hours. Then to see if the current rain was part of the same storm or the start of a new one, DRY_TIME was checked to see if it was greater than or equal to 24/dt. This compares DRY_TIME in hours to the model time step. The "/dt" has been removed, so now DRY_TIME is checked versus the hours since the last storm. State file: (KAC) *** WARNING: This may require modifications to your global file *** The state file has been modified to account for model updates. It has also been converted to write binary files - this makes them less convenient to edit, but means that model starts using the same forcing, soil and vegetation files will produce the exact same results. There has also been a slight change in how the global file is set up to restart the model. The global file should now have the same year, month, day and hour as the original global file - the VIC model will compute the number of records to skip at the beginning to reach the point where the model state was saved. This means that calculations to yield sub-daily metrological forcings from daily forcings will produce the exact same forcing values -> this also means that restarted simulations will be exactly the same as the original run. Slight variations in the model results were also introduced because the method for storing soil node depths led to the possibility of very small differences in dz_node for the restarted model. Previous versions also did not store the snowpack cold content, this meant that for restarts during winter, the snowpack albedo might start on the ablation curve (as cold content was initialized to 0 and not to a value less than 0) rather than the accumulation curve. This could lead to slight differences in the snowpack if no new snow fell and the snowpack was not melting - but after 10 years of simulations the differences were minor. As noted above the new version of the state file should allow the model to be restarted and to produce exactly the same results as the original complete result. If there are cases where this is not true, please report. If you edit the read/write model state functions - BE VERY CAREFUL to edit Nbytes to reflect any changes. COMPUTE_TREELINE: (KAC and LCB) This is an added feature which computes the treeline elevation in the current grid cell and does not include vegetation fractions with overstory in the grid cell averages for snow bands that exceed the treeline elevation. This feature was added to the model to reduce the appearance of "glaciers" in high elevation snow bands. It computes average annual July air temperatures using the temperature data from the atmospheric forcing files (WARNING - elevation of treeline may change if the period of forcing data used changes). It then lapses the average annual July air temperature to locate the elevation at which it equals 10C. This is assumed to be the treeline, so vegetation types with overstory in snow bands with average elevations higher than this, are excluded from the grid cell average variables in put_data.c. For the time being full energy and water balances are still computed for these vegetation fractions, and no attempt is made to verify that a snow band has a non-overstory vegetation type that can be expanded to represent the coverage area lost due to the exclusion of the overstory fraction. ----------------------------------------------------------------------------- August 15, 2000: VIC release 4.0.3 This release fixes a problem with the implementation of va_arg that causes run time errors on some systems. Previous releases of the code worked correctly on the LINUX and freeBSD systems where it was tested. However on some systems (including Sun Ultra-2s) character variables passed with va_arg are changed into integers so reading a character from the argument list does not produce the value sent to the routine. The character flags used by VIC to indicate if there is snow present and if the frozen soil algorithm has been activated have now been converted to integers, which should make the va_arg call work on all systems. Also fixed in this release was a check in dist_prec.c to see if it is still raining which actually used the memory address of the precipitation variable rather than the daily value in the check. MODIFIED FILES: read_atmos_data.c - Fixed input file time step check write_forcing_files.c - Added free statements for pointers calc_surf_energy_bal.c - Converted char flags to int dist_prec.c - Fixed logical statement error frozen_soil.c - Converted char flags to int func_surf_energy_bal.c - Converted char flags to int initialize_atmos.c - Added flag for output forcing vicNl.h - Converted char flags to int vicNl_def.h - Converted char flags to int ----------------------------------------------------------------------------- July 19, 2000: VIC release 4.0.2 Two new pre-processor options have been added to VIC as well as minor modifications to two subroutines. If set to TRUE the NO_REWIND pre-processor option stops the VIC model from rewinding the soil and vegetation parameter input files for each new grid cell. This reduces run times but requires that all input files are in the same order as the soil parameter file. If set TRUE the OUTPUT_FORCE pre-processor option blocks off the main model and only reads the provided forcing files. Once VIC has estimated the missing forcing parameters the full forcing data set for the defined simulation period is output to a series of gridded forcing files. The gridded forcing files are written to the RESULTS directory defined in the global control file with the prefix "full_data_". The new files are in Binary or ASCII depending on the setting of BINARY_OUTPUT. The error messages in get_global_param.c have been modified so that the correct file is referenced when telling the user to change values found in the model source code. In read_soilparam.c, the soil parameters are defined only if the current grid cell is run, otherwise the line in the file is skipped and soil_con is returned without new data values. ----------------------------------------------------------------------------- May 30, 2000: VIC release 4.0.1 Increased use of the released VIC model code has lead to the discovery of a couple of minor bugs. This release fixes those bugs as well as introducing a improved precipitation correction algorithm based on Yang et al. 1998. Unless you have encountered these problems or are trying to correct precipitation undercatch due to wind, in the VIC model, your results will not be impacted by these fixes. MODIFIED FILES: correct_precip.c - changed to WMO correction equation for NWS 8" standard gauge. full_energy.c - modified to handle WMO correction. initialize_atmos.c - modified to handle WMO correction. fixed error in estimating minimum daily temperature from sub-daily temperatures. make_in_and_outfiles.c - removed line that opened the state file again for each new grid cell. open_state_file.c - modified comments. put_data.c - modified to handle WMO correction. snow_utility.c - cleaned source code. solve_snow.c - modified to handle WMO correction. surface_fluxes.c - modified to handle WMO correction. vicNl.h - modified to handle WMO correction. vicNl_def.h - modified to handle WMO correction. REFERENCE: Yang, D., B. E. Goodison, J. R. Metcalfe, V. S. Golubev, R. Bates, T. Pangburn, and C. L. Hanson, Accuracy of NWS 8" Standard Nonrecording Precipitation Gauge: Results and Application of WMO Intercomparison, J. Atmos. Oceanic Tech., 15, 54-68, 1998. ----------------------------------------------------------------------------- Date: May 16, 2000 From: Keith Cherkauer Topic: Release of VIC 4.0.0 The code for VIC release 4.0.0 has undergone several months of tests (as VIC release 3.3.0 Beta) and has now been deemed ready for release to the general public. This document is designed to provide information concerning changes in the model between the last release version (3.2.1) and the current version. There is no formal users manual, information about how to use the current version can be found at http://www.hydro.washington.edu/Lettenmaier/Models/VIC/VIChome.html. Information about the basic model design can be found in Liang, et al. (1994), while the rewrite of the source code as well as the addition of cold season processes is described in Cherkauer and Lettenmaier (1999). The VIC macroscale hydrologic model was developed as a research tool. As such it is the users responsibility to verify that it is working correctly when applied to new situations. When using the VIC model reference should be made to Liang, et al. (1994) and Cherkauer and Lettenmaier (1999) as well as an acknowledgment that the code was received from the University of Washington. Other important papers relating to the development of the VIC model are included on the home page and in the source code. Possible bugs in the code should be reported to vicadmin@hydro.washington.edu. ALWAYS CHECK YOUR INPUT FILES! Most "bugs" are actually caused by trying to run the model with bad parameters or forcing data. The VIC model will run limited checks to find common major errors but in most cases it will attempt to run with the bad values. If after checking all of your input data you still believe you have found a bug in the model, send an e-mail including the complete output from the model as well as a description of the problem and the files necessary to run the model to recreate the code (if files are large please put a compressed tar file in ftp://ftp.ce.washington.edu/pub/HYDRO/vicadmin/TEMP). Outdated and modified versions of the code are the responsibility of the user to debug. Modifications made to the code, which may improve the general model performance, may be submitted to vicadmin@hydro.washington.edu for possible inclusion in future versions of the code. VIC release 4.0.0 represents a major change to the source code from version 3.2.1. It is strongly recommended that if you were using version 3.2.1 or earlier versions that you update with a complete copy of the new code. Major changes from release version 3.2.1 to 4.0.0: - Radiation Estimation Update: The routines to estimate shortwave and longwave radiation as well as vapor pressure from daily minimum and maximum temperature and precipitation have been updated to correspond to the algorithm described by Thornton and Running (1999). These routines provide significantly improved radiation estimates especially in regions outside the continental United States. - Model Core Update: The core of the VIC model was rewritten so that all modes of the model (water balance, energy balance, etc.) make use of the same model code. This makes it easier to modify the model and have modifications apply to sll modes, it also allows the model to run with new combinations of algorithms (i.e. full energy balance mode with the finite difference ground heat flux solution). - Soil Moisture Transport Update: The frozen and thawed sub-layers added to the model for the original frozen soil algorithm have been removed. This makes the soil drainage routine cleaner and faster. Frozen soils now estimate full layer ice contents from the ice content at each soil thermal node. Without being confined by sub-layers, the frozen soil algorithm can now be applied to regions of permafrost. - Forcing File Control Added: Version 4.0.0 moves controls of the forcing file format and data types into the global control file. The model can now handle most ASCII column and short int Binary files without writing new subroutines and recompiling the source code. - Pre-processor Options Added: There are now more option flags in the source code headers to control which parts of the model are in fact compiled. This allows the model functionality to be adjusted without the addition of computationally intensive conditional switching statements. - Model State File: With the release of version 4.0.0 separate snow and soil initialization files have been combined into a single model state file. The state file can be created outside the model for starting simulations with prescribed initial conditions, or the model state can be saved by VIC at a specified date. Note that currently there will be small differences between a full and a warm started simulation because radiation and vapor pressure are estimated using forcing data from the simulation period, not from the full dataset included in the forcing file. It also does not store wet and dry fraction information, when running with distributed precipitation the model is restarted using average soil conditions. References: Liang, X., D. P. Lettenmaier, E. F. Wood, and S. J. Burges, A simple hydrologically based model of land surface water and energy fluxes for GSMs, J. Geophys. Res., 99(D7), 14,415-14,428, 1994. Cherkauer, K. A., and D. P. Lettenmaier, Hydrologic effects of frozen soils in the upper Mississippi River basin, J. Geophys. Res., 104(D16), 19,599-19,610, 1999. Thornton, P.E. and S.W. Running, An improved algorithm for estimating incident daily solar radiation from measurements of temperature, humidity, and precipitation, Ag. For. Met., 93, 211-228, 1999. File List: CalcAerodynamic.c modify_Ksat.c Makefile mtclim42_vic.c SnowPackEnergyBalance.c mtclim42_vic.h StabilityCorrection.c mtclim42_wrapper.c alloc_atmos.c nrerror.c arno_evap.c open_debug.c calc_air_temperature.c open_file.c calc_cloud_cover_fraction.c open_state_file.c calc_longwave.c penman.c calc_rainonly.c prepare_full_energy.c calc_root_fraction.c put_data.c calc_surf_energy_bal.c read_arcinfo_ascii.c calc_veg_params.c read_atmos_data.c canopy_evap.c read_forcing_data.c check_files.c read_initial_model_state.c check_state_file.c read_snowband.c close_files.c read_soilparam.c cmd_proc.c read_soilparam_arc.c compress_files.c read_veglib.c compute_dz.c read_vegparam.c correct_precip.c redistribute_during_storm.c dist_prec.c root_brent.c estimate_T1.c runoff.c free_dist_prcp.c snow.h free_vegcon.c snow_intercept.c frozen_soil.c snow_melt.c full_energy.c snow_utility.c func_surf_energy_bal.c soil_conduction.c get_force_type.c soil_thermal_eqn.c get_global_param.c solve_snow.c global.h store_moisture_for_debug.c initialize_atmos.c surface_fluxes.c initialize_global.c svp.c initialize_model_state.c user_def.h initialize_new_storm.c vicNl.c initialize_snow.c vicNl.h initialize_soil.c vicNl_def.h initialize_veg.c vicerror.c make_cell_data.c write_atmosdata.c make_dist_prcp.c write_data.c make_dmy.c write_debug.c make_energy_bal.c write_layer.c make_in_and_outfiles.c write_model_state.c make_snow_data.c write_soilparam.c make_veg_var.c write_vegparam.c massrelease.c write_vegvar.c