Base class for a model which computes surface mass flux rate (ice thickness per time) from precipitation and temperature. More...

#include <localMassBalance.hh>

Inheritance diagram for LocalMassBalance:

[legend]

List of all members.

Public Member Functions
	LocalMassBalance (const NCConfigVariable &myconfig)
virtual	~LocalMassBalance ()
virtual PetscErrorCode	init ()
virtual PetscErrorCode	getNForTemperatureSeries (PetscScalar t, PetscScalar dt, PetscInt &N)=0
virtual PetscScalar	getPDDSumFromTemperatureTimeSeries (PetscScalar pddStdDev, PetscScalar pddThresholdTemp, PetscScalar t, PetscScalar dt_series, PetscScalar *T, PetscInt N)=0
	Count positive degree days (PDDs). Returned value in units of K day.
virtual PetscScalar	getSnowFromPrecipAndTemperatureTimeSeries (PetscScalar precip_rate, PetscScalar t, PetscScalar dt_series, PetscScalar *T, PetscInt N)=0
virtual PetscErrorCode	getMassFluxesFromPDDs (const DegreeDayFactors &ddf, PetscScalar dt, PetscScalar pddsum, PetscScalar snow, PetscScalar &accumulation_rate, PetscScalar &melt_rate, PetscScalar &runoff_rate, PetscScalar &smb_rate)=0
Protected Attributes
const NCConfigVariable &	config

Detailed Description

Base class for a model which computes surface mass flux rate (ice thickness per time) from precipitation and temperature.

This is a process model. At each spatial location, it uses a 1D array, with a time dimension, for the temperature used in melting snow or ice. At each spatial location it assumes the precipitation is time-independent.

This process model does not know its location on the ice sheet, but simply computes the surface mass balance from three quantities:

the time interval $[t,t+\Delta t]$ ,
time series of values of surface temperature at equally-spaced times in the time interval
a scalar precipation rate which is taken to apply in the time interval.

This model also uses degree day factors passed-in in DegreeDayFactors ddf, and the standard deviation pddStdDev. The latter is the standard deviation of the modeled temperature away from the input temperature time series which contains the part of location-dependent temperature cycle on the time interval.

Note:

Please avoid using config.get("...") and config.get_flag("...") calls inside those methods of this class which are called inside loops over spatial grids. Doing otherwise increases computational costs.
This base class should be more general. For instance, it could allow as input a time series for precipation rate.

Definition at line 65 of file localMassBalance.hh.

Constructor & Destructor Documentation

LocalMassBalance ( const NCConfigVariable & myconfig ) [inline]

Definition at line 67 of file localMassBalance.hh.

virtual ~LocalMassBalance ( ) [inline, virtual]

Definition at line 69 of file localMassBalance.hh.

Member Function Documentation

virtual PetscErrorCode getMassFluxesFromPDDs	(	const DegreeDayFactors &	ddf,
		PetscScalar	dt,
		PetscScalar	pddsum,
		PetscScalar	snow,
		PetscScalar &	accumulation_rate,
		PetscScalar &	melt_rate,
		PetscScalar &	runoff_rate,
		PetscScalar &	smb_rate
	)		`[pure virtual]`

Input dt is in seconds. Input pddsum is in K day. Input snow is in ice-equivalent m. Returned mass fluxes, including accumulation_rate, melt_rate, runoff_rate, and smb (= surface mass balance), are in ice-equivalent thickness per time (m s-1).

Implemented in PDDMassBalance.

Referenced by PSTemperatureIndex::update_internal().

virtual PetscErrorCode getNForTemperatureSeries	(	PetscScalar	t,
		PetscScalar	dt,
		PetscInt &	N
	)		`[pure virtual]`

Call before getMassFluxFromTemperatureTimeSeries() so that mass balance method can decide how to cut up the time interval. Most implementations will ignore t and just use dt. Input t,dt in seconds.

Implemented in PDDMassBalance, and PDDrandMassBalance.

Referenced by PSTemperatureIndex::update_internal().

virtual PetscScalar getPDDSumFromTemperatureTimeSeries	(	PetscScalar	pddStdDev,
		PetscScalar	pddThresholdTemp,
		PetscScalar	t,
		PetscScalar	dt_series,
		PetscScalar *	T,
		PetscInt	N
	)		`[pure virtual]`

Count positive degree days (PDDs). Returned value in units of K day.

Inputs T[0],...,T[N-1] are temperatures (K) at times t, t+dt_series, ..., t+(N-1)dt_series. Inputs t, dt_series are in seconds.

Implemented in PDDMassBalance, and PDDrandMassBalance.

Referenced by PSTemperatureIndex::update_internal().

virtual PetscScalar getSnowFromPrecipAndTemperatureTimeSeries	(	PetscScalar	precip_rate,
		PetscScalar	t,
		PetscScalar	dt_series,
		PetscScalar *	T,
		PetscInt	N
	)		`[pure virtual]`