Attributes

All attributes are object (instance) attributes, as opposed to class attributes. Thus, if x is an AtmQty object, the latitude attribute is x.lat.

The columns mean:

• Attribute: Name of the attribute.
• Type: The value of the string returned by the built-in method type on the attribute. All types array are Numeric arrays.
• Fixed?: If "Y" means this attribute must not change for the life of the instance. If "N", the attribute may be altered during the life of the instance. If "Y/N", in some cases this attribute must not change, while in others it may be altered (see the description).
• Description: Description of the attribute.

If an example is given in the description, it is assumed x is an AtmQty object.

Attribute	Type	Fixed?	Description
lat	array	Y	Latitude vector of the domain. Set at object instantiation via positional parameter.
lev	array	Y	Level vector of the domain, in either units of pressure levels [hPa] or isentropic levels [K]; the units of the levels are specified in the lev_type attribute. Set at object instantiation via positional parameter.
lev_type	str	Y	The level "type" given in attribute lev, and which can have the following values: "pressure": Vertical levels are in pressure coordinates and lev is in units hPa (this is the default value of lev_type). "isentropic": Vertical levels are in isentropic (constant potential temperature levels) coordinates and lev is in units K. Set at object instantiation via keyword parameter.
lon	array	Y	Longitude vector of the domain. Set at object instantiation via positional parameter.
missing	float	Y	Missing value value. Scalar. Set at object instantiation via keyword parameter; default value is 1e+20.
P_surf	float or array	N	Surface pressure [hPa]. Used to calculate altitude. Either floating point scalar or an array of shape of the tuple given by the sizes of attributes (lat, lon). Has no missing values. Value is set to None on object instantiation. The attribute value can be changed directly or via the P_surf keyword in class method alt.
p0	float	Y/N	Reference pressure used to calculate potential temperature [hPa]. Scalar. If lev_type is "isentropic", set at object instantiation via keyword parameter; default value is 1000. In this case, the attribute must not change during the life of the instance. If lev_type is "pressure", set by method theta. In this case, the attribute can change anytime theta is called.
qty_shape	tuple	Y	The shape of all qty quantities. 3-element integer tuple given by the sizes of attributes (lat, lon, lev). Set on object instantiation.
T_surf	float or array	N	Surface temperature [K]. Used to calculate altitude. Either floating point scalar or an array of shape of the tuple given by the sizes of attributes (lat, lon). Has no missing values. Value is set to None on object instantiation. The attribute value can be changed directly or via the T_surf keyword in class method alt.
qty	dict	N	Each key:value pair represents an "atmospheric quantity" and is a rank 3 Numeric array, of shape qty_shape. Example: x.qty['T'] is the rank 3 Numeric array of temperatures in the object domain. Initialized on object instantiation.

Quantities

All atmospheric quantities are stored as key:value pairs in the object (instance) attribute qty. The are added (or overwritten) to qty by the add_qty method, deleted from qty by the del_qty method, and extracted from the qty by the get_qty method. The values of the quantities are all rank 3 Numeric floating point (any precision) arrays whose domain and shape is described by attribute tuple qty_shape.

Note that not all the quantities below are currently defined in the object; some of the key names are listed here as placeholders.

Key	Units	Description
alt	m	Geopotential altitude, assuming temperature and altitude are related as described in the 1976 U.S. Standard Atmosphere.
e	hPa	Vapor pressure (with respect to over water).
eice	hPa	Saturation vapor pressure over ice.
esat	hPa	Saturation vapor pressure over water.
fc	1/s	Coriolis parameter.
gpot	m	Geopotential height.
N2	1/s2	Static stability (square of the buoyancy frequency).
p	hPa	Pressure.
pv	m2 s-1 K kg-1	Potential vorticity. If lev_type is "isentropic", this is isentropic potential vorticity.
q	kg/kg	Specific humidity.
r	kg/kg	Mixing ratio.
RH	unitless fraction	Relative humidity.
rho	kg/m3	Air density (including moisture effects).
T	K	Temperature.
theta	K	Potential temperature.
theta_e	K	Equivalent potential temperature.
T_v	K	Virtual temperature.
u	m/s	Zonal velocity.
v	m/s	Meridional velocity.
vort_rel	1/s	Relative vorticity.

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Updated: May 18, 2004 by Johnny Lin <email address>. License.