EPW weather files and gendaylit

Explanations

Dayhours

((direct_norm != 0) and (diffuse_horizontal != 0))

Flags

Add up to total number of hours for which the following is true:
((direct_norm != 0) or (diffuse_horizontal != 0) or (solar_altitude > 0)). The four digits and characters are:

• Data source of direct normal irradiation
• Uncertainty of direct normal irradiation
• Data source of diffuse horizontal irradiation
• Uncertainty of diffuse horizontal irradiation

Code	Definition of data source
A	Post-1976 measured solar radiation data as received from NCDC or other sources
B	Same as "A" except the global horizontal data underwent a calibration correction
C	Pre-1976 measured global horizontal data (direct and diffuse were not measured before 1976), adjusted from solar to local time, usually with a calibration correction
D	Data derived from the other two elements of solar radiation using the relationship, global = diffuse + direct cosine (zenith)
E	Modeled solar radiation data using inputs of observed sky cover (cloud amount) and aerosol optical depths derived from direct normal data collected at the same location
F	Modeled solar radiation data using interpolated sky cover and aerosol optical depths derived from direct normal data collected at the same location
G	Modeled solar radiation data using observed sky cover and aerosol optical depths estimated from geographical relationships
H	Modeled solar radiation data using interpolated sky cover and estimated aerosol optical depths
I	Modeled illuminance or luminance data derived from measured or modeled solar radiation data
?	Source does not fit any of the above categories. Used for nighttime values and missing data

Flag	Uncertainty Range (%)
1	Not used
2	2-4
3	4-6
4	6-9
5	9-13
6	13-18
7	18-25
8	25-35
9	35-50
0	Not applicable

NegGamb

The gendaylit sky has a negative ground ambient value. No warning or error is given if this happens.

zAngle

gendaylit returned the following error: "solar zenith angle larger than 90° in fuction air_mass(): the models used are not more valid"

Clear

gendaylit returned the following error: "sky clearness or sky brightness out of range"

IrradRange

gendaylit returned the following error: "direct or diffuse irradiances out of range".

IlluRange

gendaylit returned the following error: "direct or diffuse illuminances out of range". This seems to happen when there is no diffuse horizontal irradiance, but a positive direct normal one. In theory, this would only be possible if the Earth had no atmosphere.

PosSun

No radiation at all, but the solar altitude is positive

NegIrrad

Either the direct normal or the diffuse horizontal irradiance in the EPW file is negative