Descriptor File Structure

This file contains microphysical specifications for all hydrometeors. It includes central parameters for PSD, m-D, A-D relation and selection of scattering model for frozen hydrometeors. All values (e.g. a and b parameter for m-D relation) have to be provided in SI units.

The descriptor file consists of the following fields

field	values	description
name	string	name of the hydrometeor
as_ratio	positive float	aspect ratio of hydrometeor. <0 means oblate. Note that mie-sphere, liudb and rayleigh do not consider as_ratio when estimating the scattering properties.
liq_ice	-1, 1	Phase of hydrometeor, -1 is ice, 1 is liquid
rho_ms	positive float	Density of hydrometeor (ice only)
a_ms	positive float	‘a’ parameter of mass-size relation (ice only)
b_ms	positive float	‘b’ parameter of mass-size relation (ice only)
alpha	positive float	‘alpha’ parameter of cross section area-size relation (ice only). Only required for the advanced radar simulator.
beta	positive float	‘beta’ parameter of cross section area-size relation (ice only). Only required for the advanced radar simulator.
moment_in	0,1,2,3,12,23,13	Moment provided in input file (see below)
nbin	positive int	Number of discrete size bins (internally, always nbin+1 is used)
dist_name	str	Name of hydrometeor distribution (see table below)
p_1	float	1st parameter of hydrometeor distribution (see table below)
p_2	float	2nd parameter of hydrometeor distribution (see table below)
p_3	float	3rd parameter of hydrometeor distribution (see table below)
p_4	float	4th parameter of hydrometeor distribution (see table below)
d_1	positive float	minimum diameter
d_2	positive float	maximum diameter of size distribution (not required for mono-disperse distribution)
scat_name	string	Scattering model. For passive and active, it can be “disabled” for disabling the specific hydrometeor, “mie-sphere”, “tmatrix” (very slow), “liudb%P”, and “hongdb%P”. For active only: “rayleigh”, “rayleigh-gans”, “ss-rayleigh-gans_%k_%b”. %P is for the particle type of the Liu or the Hong database (00 to 10) as described in their publications (see PAMTRA publication), %k and %b are for the kappa and beta parameter of the self similar Rayleigh Gans approach. If not provided, default values kappa = 0.19 and beta = 0.23 are used.
vel_size_mod	string	Used model to estimate the fall velocity of hydrometeors. Can be ‘khvorostyanov01_drops’ (recommended for liquid), ‘khvorostyanov01_spheres’, ‘rogers_drops’, ‘heymsfield10_particles’ (recomended for ice and snow), ‘khvorostyanov01_particles’, ‘rogers_graupel’, ‘powerLaw_%A_%B’, ‘corPowerLaw_%A_%B’ (with pressure correction). %A and %B are teh parameters of the power law v(D) = %A*D^%B. Only required for the advanced radar simulator.
canting	float	Canting angle of hydrometeors. Only for Tmatrix and (Self similar) Rayleigh Gans. The latter accept only values of 0 and 90deg.

The complete list of options which can be used to define the PSD is given in table below. The table should be used as follows: given a distribution dist_name and a set of the parameters p_1 to p_4, moment_in describes the available choices for the moments of the PSD that have to be included in the input_file. 1 means the total number concentration, 2 the effective radius, 3 the mass concentration, 13 both number and mass concentration and so on. d_1 and d_2 describe the diameter of the smallest and largest particle considered to calculate absorption and scattering properties for a given class of hydrometeors.

dist_name	p_1	p_2	p_3	p_4	moment_in	d_1	d_2
mono	-99	-99	-99	-99	1 or 3	d_1	-99
mono	N_T	-99	-99	-99	2 or 3	-99	-99
mono_cosmo	-99	-99	-99	-99	3	-99	-99
exp	N_T	-99	-99	-99	2 or 3	d_1	d_2
exp	-99	R_eff	-99	-99	1 or 3	d_1	d_2
exp	-99	-99	N_0	-99	1, 2, or 3	d_1	d_2
exp	-99	-99	-99	-99	12, 13, or 23	d_1	d_2
exp_field_t	-99	-99	-99	-99	2 or 3	d_1	d_2
exp_field_tq	-99	-99	-99	-99	3	d_1	d_2
exp_ryan	-99	-99	-99	-99	1 or 3	d_1	d_2
logn	N_T	-99	sigma	-99	2 or 3	d_1	d_2
logn	N_T	R_eff	-99	-99	3	d_1	d_2
logn	-99	R_eff	sigma	-99	1 or 3	d_1	d_2
logn	-99	-99	sigma	-99	12, 13, or 23	d_1	d_2
mgamma	N_T	-99	mu	gamma	2 or 3	d_1	d_2
mgamma	-99	R_eff	mu	gamma	1 or 3	d_1	d_2
mgamma	-99	-99	mu	gamma	12, 13, or 23	d_1	d_2

Note that it is also possible to provide discrete vectors for particle size concentration, mass, cross section area, density, and aspect ratio. See addFullSpectra of the class pamDescriptorFile.

An exemplary descriptor_file for a simulation with two hydrometeors is given in the table below. For the first hydrometeor category named cwc_q, the log-normal distribution have been used with a sigma of 0.38, fixed for the whole simulation via the parameter p_3. Since the hydrometeor is in liquid phase, the density and the a and b parameters of the mass-size relation will be ignored. The aspect ratio and canting angle has been set to missing value (-99) because single scattering properties are calculated with Mie theory assuming spherical particles. The second hydrometeor swc_q is used to simulate snow. In this case an exponential distribution is used with a temperature dependent intercept parameter. The thermodynamic state of the atmospheric columns included in the simulation and the surface properties are provided via the input_file (IF), which can be in ascii or net-cdf format. The minimum set of parameters that has to be included for clear sky simulations are: surface temperature, longitude, latitude, date and profiles of temperature, pressure, height and relative humidity. In case of cloudy profiles, the moments of the PSD specified in the descriptor_file need to be included. The PAMTRA model gives as output TB for 2 observational heights, one is fixed at ground and the other can be specified in the IF for each profile.

name	as_ratio	liq_ice	rho_ms	a_ms	b_ms	alpha	beta	moment_in	nbin	dist_name	p_1	p_2	p_3	p_4	d_1	d_2	scat_name	vel_size_mod	canting
cwc_q	-99.	1	-99.	-99.	-99.	-99.	-99.	23	100	logn	-99.	-99.	0.38	-99.	1.e-12	1 .e-2	mie-sphere	khvorostyanov01_drops	-99.
swc_q	-99.	-1	-99.	0.038	2.0	0.3971	1.88	3	100	exp_field_t	-99.	-99.	-99.	-99.	0.51e-10	2 .e-2	mie-sphere	heymsfield10_particles	-99.