pvlib.iotools.read_tmy3

pvlib.iotools.read_tmy3(filename, coerce_year=None, recolumn=True)

Read a TMY3 file into a pandas dataframe.

Note that values contained in the metadata dictionary are unchanged from the TMY3 file (i.e. units are retained). In the case of any discrepancies between this documentation and the TMY3 User’s Manual 1, the TMY3 User’s Manual takes precedence.

The TMY3 files were updated in Jan. 2015. This function requires the use of the updated files.

Parameters

• filename (str) – A relative file path or absolute file path.

• coerce_year (None or int, default None) – If supplied, the year of the index will be set to coerce_year, except for the last index value which will be set to the next year so that the index increases monotonically.

• recolumn (bool, default True) – If True, apply standard names to TMY3 columns. Typically this results in stripping the units from the column name.

Returns

• Tuple of the form (data, metadata).

• data (DataFrame) – A pandas dataframe with the columns described in the table below. For more detailed descriptions of each component, please consult the TMY3 User’s Manual (1), especially tables 1-1 through 1-6.

• metadata (dict) – The site metadata available in the file.

Notes

The returned structures have the following fields.

key	format	description
altitude	Float	site elevation
latitude	Float	site latitudeitude
longitude	Float	site longitudeitude
Name	String	site name
State	String	state
TZ	Float	UTC offset
USAF	Int	USAF identifier

field	description
Index	A pandas datetime index. NOTE, the index is timezone aware, and times are set to local standard time (daylight savings is not included)
ETR	Extraterrestrial horizontal radiation recv’d during 60 minutes prior to timestamp, Wh/m^2
ETRN	Extraterrestrial normal radiation recv’d during 60 minutes prior to timestamp, Wh/m^2
GHI	Direct and diffuse horizontal radiation recv’d during 60 minutes prior to timestamp, Wh/m^2
GHISource	See 1, Table 1-4
GHIUncertainty	Uncertainty based on random and bias error estimates see 2
DNI	Amount of direct normal radiation (modeled) recv’d during 60 mintues prior to timestamp, Wh/m^2
DNISource	See 1, Table 1-4
DNIUncertainty	Uncertainty based on random and bias error estimates see 2
DHI	Amount of diffuse horizontal radiation recv’d during 60 minutes prior to timestamp, Wh/m^2
DHISource	See 1, Table 1-4
DHIUncertainty	Uncertainty based on random and bias error estimates see 2
GHillum	Avg. total horizontal illuminance recv’d during the 60 minutes prior to timestamp, lx
GHillumSource	See 1, Table 1-4
GHillumUncertainty	Uncertainty based on random and bias error estimates see 2
DNillum	Avg. direct normal illuminance recv’d during the 60 minutes prior to timestamp, lx
DNillumSource	See 1, Table 1-4
DNillumUncertainty	Uncertainty based on random and bias error estimates see 2
DHillum	Avg. horizontal diffuse illuminance recv’d during the 60 minutes prior to timestamp, lx
DHillumSource	See 1, Table 1-4
DHillumUncertainty	Uncertainty based on random and bias error estimates see 2
Zenithlum	Avg. luminance at the sky’s zenith during the 60 minutes prior to timestamp, cd/m^2
ZenithlumSource	See 1, Table 1-4
ZenithlumUncertainty	Uncertainty based on random and bias error estimates see 1 section 2.10
TotCld	Amount of sky dome covered by clouds or obscuring phenonema at time stamp, tenths of sky
TotCldSource	See 1, Table 1-5
TotCldUncertainty	See 1, Table 1-6
OpqCld	Amount of sky dome covered by clouds or obscuring phenonema that prevent observing the sky at time stamp, tenths of sky
OpqCldSource	See 1, Table 1-5
OpqCldUncertainty	See 1, Table 1-6
DryBulb	Dry bulb temperature at the time indicated, deg C
DryBulbSource	See 1, Table 1-5
DryBulbUncertainty	See 1, Table 1-6
DewPoint	Dew-point temperature at the time indicated, deg C
DewPointSource	See 1, Table 1-5
DewPointUncertainty	See 1, Table 1-6
RHum	Relatitudeive humidity at the time indicated, percent
RHumSource	See 1, Table 1-5
RHumUncertainty	See 1, Table 1-6
Pressure	Station pressure at the time indicated, 1 mbar
PressureSource	See 1, Table 1-5
PressureUncertainty	See 1, Table 1-6
Wdir	Wind direction at time indicated, degrees from north (360 = north; 0 = undefined,calm)
WdirSource	See 1, Table 1-5
WdirUncertainty	See 1, Table 1-6
Wspd	Wind speed at the time indicated, meter/second
WspdSource	See 1, Table 1-5
WspdUncertainty	See 1, Table 1-6
Hvis	Distance to discernable remote objects at time indicated (7777=unlimited), meter
HvisSource	See 1, Table 1-5
HvisUncertainty	See 1, Table 1-6
CeilHgt	Height of cloud base above local terrain (7777=unlimited), meter
CeilHgtSource	See 1, Table 1-5
CeilHgtUncertainty	See 1, Table 1-6
Pwat	Total precipitable water contained in a column of unit cross section from earth to top of atmosphere, cm
PwatSource	See 1, Table 1-5
PwatUncertainty	See 1, Table 1-6
AOD	The broadband aerosol optical depth per unit of air mass due to extinction by aerosol component of atmosphere, unitless
AODSource	See 1, Table 1-5
AODUncertainty	See 1, Table 1-6
Alb	The ratio of reflected solar irradiance to global horizontal irradiance, unitless
AlbSource	See 1, Table 1-5
AlbUncertainty	See 1, Table 1-6
Lprecipdepth	The amount of liquid precipitation observed at indicated time for the period indicated in the liquid precipitation quantity field, millimeter
Lprecipquantity	The period of accumulatitudeion for the liquid precipitation depth field, hour
LprecipSource	See 1, Table 1-5
LprecipUncertainty	See 1, Table 1-6
PresWth	Present weather code, see 2.
PresWthSource	Present weather code source, see 2.
PresWthUncertainty	Present weather code uncertainty, see 2.

Midnight representation

The function is able to handle midnight represented as 24:00 (NREL TMY3 format, see 1) and as 00:00 (SolarAnywhere TMY3 format, see 3).

Warning

TMY3 irradiance data corresponds to the previous hour, so the first index is 1AM, corresponding to the irradiance from midnight to 1AM, and the last index is midnight of the next year. For example, if the last index in the TMY3 file was 1988-12-31 24:00:00 this becomes 1989-01-01 00:00:00 after calling read_tmy3().

Warning

When coercing the year, the last index in the dataframe will become midnight of the next year. For example, if the last index in the TMY3 was 1988-12-31 24:00:00, and year is coerced to 1990 then this becomes 1991-01-01 00:00:00.

References

1(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39)

Wilcox, S and Marion, W. “Users Manual for TMY3 Data Sets”. NREL/TP-581-43156, Revised May 2008.

2(1,2,3,4,5,6,7,8,9)

Wilcox, S. (2007). National Solar Radiation Database 1991 2005 Update: Users Manual. 472 pp.; NREL Report No. TP-581-41364.

3

SolarAnywhere file formats

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