Snow submodel notions

[tyralla]

This is a subissue of #188. It serves to discuss and document the unification of the parameter and sequence names of the main models' snow modules (listed in #188), as well as the parameter and sequence names of snow_cn and snow_cn_minmax.

I will continuously edit the following tables.

control parameters

(Some subarea parameters handle relative values and others handle absolute values.)

HBV	LARSIM	WHMod	WALRUS	Snow old	Snow new
NmbZones	NHRU	NmbZones	NU	-	NumberZones
SClass	-	-	-	ZLayers	NumberDivisions
ZoneArea	-	ZoneArea	-	-	ZoneArea
ZoneZ	GH	-	GL	-	ZoneHeight
TCor	KT	-	-	-	TemperatureAddend
TCAlt	ATG	-	-	GradTMean	LapseRate
TT	TGr	-	TT	-	RainSnowThreshold
TTInt	TSp	-	TI	-	RainSnowInterval
SFDist	-	-	-	-	ThroughfallDistribution
TT + DTTM = TTM)	TRefT	-	DDT	-	DegreeDayThreshold
CFMax	GTF	DegreeDayFactor	DDF	CN2	DegreeDayFactor
CFVar	-	-	-	-	DegreeDayVariability
CFR	-	-	-	-	FreezingFactor
WHC	PWMax	-	-	-	WaterCapacity
SMax	-	-	-	-	SnowpackLimit
SRed	-	-	-	-	RedistributionPaths

derived parameters

HBV	LARSIM	WHMod	WALRUS	Snow old	Snow new
RelZoneAreas	FHRU (control)	ZoneRatio	AUR (control)		ZoneAreaFraction
RelLandAreas					LandAreaFraction
ZoneAreaRatios					ZoneAreaRatio
Z	MGH	-	-	ZMean	AverageHeight
IndicesZoneZ	-	-	-	-	ZoneHeightOrder
SRedOrder	-	-	-	-	RedistributionOrder
SRedEnd	-	-	-	-	RedistributionEnd
SRedNumber	-	-	-	-	RedistributionNumber

input sequences

HBV	LARSIM	WHMod	WALRUS	Snow old	Snow new
T	TemL	Temperature	T	T	AirTemperature

state sequences

HBV	LARSIM	WHMod	WALRUS	Snow old	Snow new
SWE (factor)	WAeS	SnowPack	SP	G	Snowpack (factor)
SP	WATS	-	-	-	IceContent
WC	-	-	-	-	WaterContent

factor sequences

HBV	LARSIM	WHMod	WALRUS	Snow old	Snow new
TC	TKor	-	-	TLayer	AdjustedTemperature
FracRain	SNRatio	-	FR	1 - SolidFractionPrecipitation	RainSnowFraction
CFact	-	-	-	-	MeltingFactor

flux sequences

HBV	LARSIM	WHMod	WALRUS	Snow old	Snow new
-	SchmPot	-	PM	PotMelt	PotentialMelt
Melt	Schm	-	AM	Melt	ActualMelt
-	GefrPot	-	-	-	PotentialFreeze
Refr	Gefr	-	-	-	ActualFreeze
In_	WaDa	Ponding	RF + AM	PNetLayer	Release
SPL	-	-	-	-	IceLoss
WCL	-	-	-	-	WaterLoss
SPG	-	-	-	-	IceGain
WCG	-	-	-	-	WaterGain

aide sequences

HBV	LARSIM	WHMod	WALRUS	Snow old	Snow new
SPE	-	-	-	-	IceContentExcess
WCE	-	-	-	-	WaterContentExcess

[tyralla]

I think we should follow HydPy-Evap's naming style whenever appropriate. Many names are reusable (NmbHRU, HRUArea, etc.).

[tyralla]

I suggest unifying the terms SClass (of HBV) and ZLayers (of CemaMeige) to NmbDiv (number of divisions). This is somewhat consistent with NmbHRU. And it is a very generic term that leaves room for different meanings.

[tyralla]

Regarding Release: I do not intend to rename the different corresponding sequences of the land models. I just wanted to clarify that they all represent the same thing.

[tyralla]

I think we should follow HydPy-Evap's naming style whenever appropriate. Many names are reusable (NmbHRU, HRUArea, etc.).

I disagree with my older self and now prefer more general names, comparable to NmbDiv. I would say NmbZones and ZoneArea are better. It may not be ideal that HydPy-H, HydPy-WHMod, and HydPy-Dummy also use these terms, but "zone" is a short, clear word, and other notions such as "scope", "sector", or "field" are less understandable or already used in other contexts.

[tyralla]

I think we should follow HydPy-Evap's naming style whenever appropriate. Many names are reusable (NmbHRU, HRUArea, etc.).

I disagree with my older self and now prefer more general names, comparable to NmbDiv. I would say NmbZones and ZoneArea are better. It may not be ideal that HydPy-H, HydPy-WHMod, and HydPy-Dummy also use these terms, but "zone" is a short, clear word, and other notions such as "scope", "sector", or "field" are less understandable or already used in other contexts.

I prefer not to mix complete names and abbreviations. Hence: NumberZones, ZoneArea, NumberDivisions.

[tyralla]

I think RainSnowThreshold and RainSnowInterval are very clear and consistent. RainSnowTemperatureThreshold and RainSnowTemperatureInterval would be even more precise but appear like overkill to me. Also, the unit K will clarify what these variables are dealing with.

[tyralla]

I would prefer PrecipitationDistribution over SnowfallDistribution for SFDist because this factor affects liquid and frozen precipitation in the same way. The name SFDist made sense in HydPy-H to clarify that this parameter is only relevant for the snow module. As a HydPy-Snow parameter, this context should already be clear.

[tyralla]

ThroughfallDistribution is more precise than PrecipitationDistribution.

[tyralla]

LiquidWaterHoldingCapacity, WaterHoldingCapacity, or HoldingCapacity?

[tyralla]

I shortened two names:

• WaterHoldingCapacity -> WaterCapacity
• LiquidWaterContent --> WaterContent

[tyralla]

CFact --> MeltingFactor

A more precise name would be ActualDegreeDayFactor. Then, we should rename DegreeDayFactor to AverageDegreeDayFactor. But these names are unnecessarily long, in my opinion.