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ohd.hseb.dhm.specs.ModSpecifications

Precipitation Mods

DHM precipitation Modifiations (PMODS) are a way for users to edit the hourly accumulated observed precipitation in each grid cell. Precip_mods are never applied to future precipitation. Precip_mods contain the following information


precip mod contents
.DPRECIP 1201200612z 1202200612z 1205200612z 2.0

mod file description
value in mod file meaning
.DPRECIP keyword denoting a DHM precip modification
1201200612z star date and time; when the modified observed precipitation starts (inclusive)
1202200612z end date and time; when the modified observed precipitation ends (non-inclusive)
1205200612z valid date and time; when the mod expires
2.0 the muliplier used to adjust the observed precip (i.e. values less than 1.0 are reductions in precip and vice-versa)

Has the mod expired?

DHM determines if the precip mod has expired by comparing the mod's valid date and time (i.e. when the mod was created) to the model run's date and time;
For example if the model is run at 12/02/2006 12z, then following should be true


test valid date and time
mod valid date and time model run date and time has the mod expired
12/01/2006 12z 12/02/2006 12Z yes
12/02/2006 12z 12/02/2006 12Z no
12/02/2006 13z 12/02/2006 12Z no
12/03/2006 12z 12/02/2006 12Z no

Expired Mods

When a precip mod has expired, the mod's end date and time may automatically change to the valid date and time. For example if a precip mod with a valid date and time of 12/02/2006 12z has expired, then the following should be true:

test expired mod
mod valid date and time mod end date and time mod end date and time for expired mod
12/02/2006 12z 12/01/2006 12z 12/01/2006 12z
12/02/2006 12z 12/02/2006 12z 12/02/2006 12z
12/02/2006 12z 12/03/2006 12z 12/02/2006 12z

When to Apply Mods

PMODS are only for model time steps within the mod's start and end date window.
For example, if the model is run for the period 12/02/2006 to 12/07/2006. Then the folowing should be true

test mod application
mod start date and time mod end date and time model time step date and time is mod applied
12/02/2006 12z 12/03/2006 12z 12/02/2006 18z yes
12/02/2006 12z 12/03/2006 12z 12/05/2006 18z no
12/02/2006 12z 12/03/2006 12z 12/02/2006 12z yes
12/02/2006 12z 12/03/2006 12z 12/03/2006 12z no
12/01/2006 12z 12/03/2006 12z 12/02/2006 18z yes

Rules for Modifying Values

A valid Precip_Mod lowers/increases the observed hourly accumulated precipitation in each cell by multiplying the mod value and the original cell value

apply mod with mod start date and time 12/02/2002 12z mod end date and time 12/04/2002 12z and value 1.2
original value model time step date and time new precip value()
1 12/03/2002 12z 1.2
0.1 12/03/2002 12z 0.12
0 12/03/2002 12z 0.0
2.0 12/05/2002 12z 2.0

Valid Precipitation Mods

Valid precip mods have a mod start date and time must be before the mod end date and time
test valid mod
mod start date and time mod end date and time are dates valid()
12/01/2006 12z 12/02/2006 12z yes
12/02/2006 12z 12/01/2006 12z error
12/01/2006 12z 12/01/2006 12z error

Valid precip mods have values greater than or equal to zero
test valid mod
mod value is mod value valid()
1.2 yes
0.0 yes
-1.2 error

Multiple Precipitation Mods

Multiple PMODS is also supported. Any overlapping periods result in a cumulative effect. For example, if the following mods are defined, the following should be true.

multiplePrecipMods

precip mod contents
.DPRECIP 1201200312z 1203200312z 1205200312z 2.0 .DPRECIP 1202200312z 1204200312z 1205200312z 2.0

check precip mod values
original value model time step date and time new precip value()
1 12/02/2003 06z 2.0
1 12/02/2003 12z 4.0
0.1 12/03/2003 11z 0.4
0.0 12/03/2003 11z 0.0
1.1 12/03/2003 12z 2.2
1.1 12/03/2003 18z 2.2
2.0 12/04/2003 12z 2.0
1.1 12/04/2003 18z 1.1




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Page last modified: October 28, 2011
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