pydaymet.pydaymet
#
Access the Daymet database for both single single pixel and gridded queries.
Module Contents#
- pydaymet.pydaymet.get_bycoords(coords, dates, coords_id=None, crs=4326, variables=None, region='na', time_scale='daily', pet=None, pet_params=None, snow=False, snow_params=None, ssl=True, to_xarray=False)#
Get point-data from the Daymet database at 1-km resolution.
This function uses THREDDS data service to get the coordinates and supports getting monthly and annual summaries of the climate data directly from the server.
- Parameters:
coords (
tuple
orlist
oftuples
) – Coordinates of the location(s) of interest as a tuple (x, y)dates (
tuple
orlist
, optional) – Start and end dates as a tuple (start, end) or a list of years[2001, 2010, ...]
.coords_id (
list
ofint
orstr
, optional) – A list of identifiers for the coordinates. This option only applies whento_xarray
is set toTrue
. If not provided, the coordinates will be enumerated.crs (
str
,int
, orpyproj.CRS
, optional) – The CRS of the input coordinates, defaults toEPSG:4326
.variables (
str
orlist
) – List of variables to be downloaded. The acceptable variables are:tmin
,tmax
,prcp
,srad
,vp
,swe
,dayl
Descriptions can be found here.region (
str
, optional) – Target region in the US, defaults tona
. Acceptable values are:na
: Continental North Americahi
: Hawaiipr
: Puerto Rico
time_scale (
str
, optional) – Data time scale which can bedaily
,monthly
(monthly summaries), orannual
(annual summaries). Defaults todaily
.pet (
str
, optional) – Method for computing PET. Supported methods arepenman_monteith
,priestley_taylor
,hargreaves_samani
, and None (don’t compute PET). Thepenman_monteith
method is based on Allen et al.[1] assuming that soil heat flux density is zero. Thepriestley_taylor
method is based on Priestley and TAYLOR[2] assuming that soil heat flux density is zero. Thehargreaves_samani
method is based on Hargreaves and Samani[3]. Defaults toNone
.pet_params (
dict
, optional) – Model-specific parameters as a dictionary, defaults toNone
. An important parameter forpriestley_taylor
andpenman_monteith
methods isarid_correction
which is used to correct the actual vapor pressure for arid regions. Since relative humidity is not provided by Daymet, the actual vapor pressure is computed assuming that the dewpoint temperature is equal to the minimum temperature. However, for arid regions, FAO 56 suggests to subtract minimum temperature by 2-3 °C to account for the fact that in arid regions, the air might not be saturated when its temperature is at its minimum. For such areas, you can pass{"arid_correction": True, ...}
to subtract 2°C from the minimum temperature for computing the actual vapor pressure.snow (
bool
, optional) – Compute snowfall from precipitation and minimum temperature. Defaults toFalse
.snow_params (
dict
, optional) – Model-specific parameters as a dictionary that is passed to the snowfall function. These parameters are only used ifsnow
isTrue
. Two parameters are required:t_rain
(deg C) which is the threshold for temperature for considering rain andt_snow
(deg C) which is the threshold for temperature for considering snow. The default values are{'t_rain': 2.5, 't_snow': 0.6}
that are adopted from https://doi.org/10.5194/gmd-11-1077-2018.ssl (
bool
, optional) – Whether to verify SSL certification, defaults toTrue
.to_xarray (
bool
, optional) – Return the data as anxarray.Dataset
. Defaults toFalse
.
- Returns:
pandas.DataFrame
orxarray.Dataset
– Daily climate data for a single or list of locations.
Examples
>>> import pydaymet as daymet >>> coords = (-1431147.7928, 318483.4618) >>> dates = ("2000-01-01", "2000-12-31") >>> clm = daymet.get_bycoords( ... coords, ... dates, ... crs="epsg:3542", ... pet="hargreaves_samani", ... ) >>> clm["pet (mm/day)"].mean() 3.713
References
- pydaymet.pydaymet.get_bygeom(geometry, dates, crs=4326, variables=None, region='na', time_scale='daily', pet=None, pet_params=None, snow=False, snow_params=None, ssl=True)#
Get gridded data from the Daymet database at 1-km resolution.
- Parameters:
geometry (
Polygon
,MultiPolygon
, orbbox
) – The geometry of the region of interest.dates (
tuple
orlist
, optional) – Start and end dates as a tuple (start, end) or a list of years [2001, 2010, …].crs (
str
,int
, orpyproj.CRS
, optional) – The CRS of the input geometry, defaults to epsg:4326.variables (
str
orlist
) – List of variables to be downloaded. The acceptable variables are:tmin
,tmax
,prcp
,srad
,vp
,swe
,dayl
Descriptions can be found here.region (
str
, optional) – Region in the US, defaults to na. Acceptable values are:na: Continental North America
hi: Hawaii
pr: Puerto Rico
time_scale (
str
, optional) – Data time scale which can be daily, monthly (monthly average), or annual (annual average). Defaults to daily.pet (
str
, optional) – Method for computing PET. Supported methods arepenman_monteith
,priestley_taylor
,hargreaves_samani
, and None (don’t compute PET). Thepenman_monteith
method is based on Allen et al.[1] assuming that soil heat flux density is zero. Thepriestley_taylor
method is based on Priestley and TAYLOR[2] assuming that soil heat flux density is zero. Thehargreaves_samani
method is based on Hargreaves and Samani[3]. Defaults toNone
.pet_params (
dict
, optional) – Model-specific parameters as a dictionary, defaults toNone
. Valid parameters are:penman_monteith
:soil_heat_flux
,albedo
,alpha
, andarid_correction
.priestley_taylor
:soil_heat_flux
,albedo
, andarid_correction
.hargreaves_samani
: None.
Default values for the parameters are:
soil_heat_flux
= 0,albedo
= 0.23,alpha
= 1.26, andarid_correction
= False. An important parameter forpriestley_taylor
andpenman_monteith
methods isarid_correction
which is used to correct the actual vapor pressure for arid regions. Since relative humidity is not provided by Daymet, the actual vapor pressure is computed assuming that the dewpoint temperature is equal to the minimum temperature. However, for arid regions, FAO 56 suggests to subtract minimum temperature by 2-3 °C to account for the fact that in arid regions, the air might not be saturated when its temperature is at its minimum. For such areas, you can pass{"arid_correction": True, ...}
to subtract 2 °C from the minimum temperature for computing the actual vapor pressure.snow (
bool
, optional) – Compute snowfall from precipitation and minimum temperature. Defaults toFalse
.snow_params (
dict
, optional) – Model-specific parameters as a dictionary that is passed to the snowfall function. These parameters are only used ifsnow
isTrue
. Two parameters are required:t_rain
(deg C) which is the threshold for temperature for considering rain andt_snow
(deg C) which is the threshold for temperature for considering snow. The default values are{'t_rain': 2.5, 't_snow': 0.6}
that are adopted from https://doi.org/10.5194/gmd-11-1077-2018.ssl (
bool
, optional) – Whether to verify SSL certification, defaults toTrue
.
- Returns:
xarray.Dataset
– Daily climate data within the target geometry.
Examples
>>> from shapely.geometry import Polygon >>> import pydaymet as daymet >>> geometry = Polygon( ... [[-69.77, 45.07], [-69.31, 45.07], [-69.31, 45.45], [-69.77, 45.45], [-69.77, 45.07]] ... ) >>> clm = daymet.get_bygeom(geometry, 2010, variables="tmin", time_scale="annual") >>> clm["tmin"].mean().compute().item() 1.361
References