SWAT - atmosphere.daylength

Used constants in this module

mef_agri.models.atmosphere.daylength.model_swat.compute_solar_declination(doy)
Parameters:

doy (int) – n-th day of the year

Returns:

solar declination [rad]

Return type:

float

mef_agri.models.atmosphere.daylength.model_swat.compute_daylength(sd, lat)
Parameters:

  • sd (float) – solar declination [rad]

  • lat (float) – geographic latitude [rad]

Returns:

daylength [h]

Return type:

float

class mef_agri.models.atmosphere.daylength.model_swat.Daylength_V2009(**kwargs)

This model computes daylength related quantities. They are all deterministic outputs because they only depend on the site latitude.

kwargs \(\rightarrow\) mef_agri.models.base.Model

daylength()

MQ - Deterministic Output

\(a_{\textrm{dl},k}=2\cdot a_{\textrm{srh},k}\) - [R1] (equ. 1:1.1.6)

Returns:

daylength

Return type:

float

daylength_min()

MQ - Deterministic Output

\(a_{\textrm{dlmin},k}\)

Returns:

minimum daylength in a year at current site

Return type:

float

initialize(epoch)

Here, daylength_min() is computed.

Parameters:

epoch (datetime.date) – initialization epoch

solar_declination()

MQ - Deterministic Output

\(a_{\textrm{sd},k}\ [rad]\) - [R1] (equ. 1:1.1.2)

The solar declination is the earth’s latittude at which incoming solar rays are normal to the earth’s surface. It is \(0^\circ\) in the spring and fall equinox and approaches \(\pm 23.5^\circ\) (summer and winter).

Returns:

solar declination

Return type:

float

sunrise_hour()

MQ - Deterministic Output

\(a_{\textrm{srh},k}\ [h]\) - [R1] (equ. 1:1.1.4)

Returns:

hour of sunrise

Return type:

float

sunset_hour()

MQ - Deterministic Output

\(a_{\textrm{ssh},k}=-a_{\textrm{srh},k}\ [h]\) - [R1] (equ. 1:1.1.5)

Returns:

hour of sunset

Return type:

float

update(epoch)

The following computations are performed

Parameters:

epoch (datetime.date) – current evaluation epoch