module_delay (10/28/02)

    This class is used to delay a CRHM HRU variable in a user module using a time shift and a storage term.   Clark's Method is used and is implemented using the following code.

ClassClark *OurDelays;

OurDelays = new ClassClark(const float* inVar, float* outVar, const float* kstorage, const float* lag);

where:

    inVar[HRU] is the input variable to be processed,

    outVar[HRU] is the destination for the delayed output variable,

    kstorage[HRU] is the desired storage constant (days) and

    lag[HRU] is the desired time shift (hours).  The resolution is equal to the observation interval.

 

To generated the delay after every module HRU so that it can be used for a downstream HRU in the same module use:

    OurDelays->DoClark(hru);// note hru in the range (0 to HRUmax-1).

If delayed and lagged output is not used in the same module then all HRUs can be processed at once using:

    OurDelays->DoClark();

The class is destroyed using,

    delete OurDelays;

To determine the quantity still in storage before destroying the storage object use:

    float residual = OurDelays->Left(hru); // note hru in the range (0 to HRUmax-1).

Sample Application of ClassClark.

class Classdelay : public ClassModule {

public:

    Classdelay(string Name = "Qdelay", String Version = "undefined") : ClassModule(Name, Version){};

    long nhru;

// declared variables

    float *Tdelay; // °C

    ClassClark *OurDelays;

// declared parameters

    const float *Kstorage;

    const float *Lag;

// declared observations

    const float *t;

// procedures

    void decl(void);

    void init(void);

    void run(void);

    void finish(bool good);

};

void Classdelay::decl(void) {

    declvar("Tdelay", NHRU, "delayed temperature", "(°C)", &Tdelay);

    declparam("Kstorage", NHRU, "[0]", "0", "20", "Air Temperature Storage", "()", &Kstorage);

    declparam("Lag", NHRU, "[1]", "0", "96", "lag delay", "(hour)", &Lag);

    declreadobs("t", NOBS, "air temperature", "(°C)", &t);

}

void Classdelay::init(void) {

    nhru = getdim(NHRU);

    for(int hh = 0; hh < nhru; hh+) Tdelay[hh] = 0.0; // initial value

    OurDelays = new ClassClark(t, Tdelay, Kstorage, Lag);

}

void Classdelay::run(void) {

    OurDelays->DoClark();

}

void Classdelay::finish(bool good) {

    delete OurDelays;

}