def calc_enthalpy(point_dict):
"""
Calculate the enthalpy and total water mixing ratio
for an air parcel, given a dictionary or parameters
Parameters
----------
point_dict: dictionary
dictionary with the following keys
['id','temp','rv','rl','press']
units: point letter, K kg/kg kg/kg Pa
Returns
-------
vals: named tuple
tuple with dictionary values plus rt (kg/kg) and enthalpy (J/kg)
"""
point_dict['rt'] = point_dict['rv'] + point_dict['rl']
vals = make_tuple(point_dict)
cp = c.cpd + vals.rt*c.cl
point_dict['enthalpy'] = cp*vals.temp + find_lv(vals.temp)*vals.rv
vals = make_tuple(point_dict)
return vals
def find_derivs(var_vec, the_time, cloud_tup):
"""
calcuate derivatives of var_vec
Parameters
----------
var_vec: vector(float)
vector of values to be integrated
the_time: float
timestep
cloud_tup: namedtuple
tuple of necessary coefficients
Returns
-------
deriv_vec: vector(float)
derivatives of each of var_vec
"""
# print('inside: ',var_vec)
temp, press, height = var_vec[-3:]
numrads = len(var_vec) - 3
dry_radius = cloud_tup.dry_radius
rho = press / (c.Rd * temp)
#
# find the evironmental S by water balance
#
S = Scalc(var_vec, cloud_tup)
deriv_vec = np.zeros_like(var_vec)
# dropgrow notes equaton 18 (W&H p. 170)
for i in range(numrads):
m = cloud_tup.masses[i]
if var_vec[i] < dry_radius[i]:
var_vec[i] = dry_radius[i]
Seq = cloud_tup.koehler_fun(var_vec[i], m)
rhovr = (Seq * find_esat(temp)) / (c.Rv * temp)
rhovinf = S * find_esat(temp) / (c.Rv * temp)
# day 25 drop_grow.pdf eqn. 18
deriv_vec[i] = (c.D / (var_vec[i] * c.rhol)) * (rhovinf - rhovr)
#
# moist adiabat day 25 equation 21a
#
deriv_vec[-3] = find_lv(temp) / c.cpd * wlderiv(var_vec, deriv_vec, cloud_tup) - c.g0 / c.cpd * cloud_tup.wvel
#
# hydrostatic balance dp/dt = -rho g dz/dt
#
deriv_vec[-2] = -1.0 * rho * c.g0 * cloud_tup.wvel
#
# how far up have we traveled?
#
deriv_vec[-1] = cloud_tup.wvel
return deriv_vec
def therm_calc(the_row):
rT = cloud_vars['wt']
S = the_row[-1]
temp, press,height = the_row[-4:-1]
esat = find_esat(temp)
e = S*esat
rv = c.eps*e/(press - e) #Thompkins eqn 2.20
Td = find_Td(rv,press)
thetae = find_thetaet(Td,rT,temp,press)
hm = c.cpd*temp + find_lv(temp)*rv + c.g0*height
return (thetae, hm)
