
w_to_omega
Convert vertical velocity with units (m/s) to Pa/s.
Available in version 6.2.0 and later.
Prototype
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl" ; This library is automatically loaded ; from NCL V6.2.0 onward. ; No need for user to explicitly load. function w_to_omega ( w : numeric, ; float, double, integer only p : numeric, t : numeric )
Arguments
wA variable of any dimensionality containing vertical velocity with units (m/s) Array size and shape must match p and t.
pA variable containing pressure values (Pa). Array size and shape must match omega and t.
tA variable containing temperature (K). Array size and shape must match omega and p.
Return value
A double array is returned if w is double, otherwise a float array of the same size and shape as w is returned.
Description
Converts vertical velocity (m/s), commonly denoted as w to vertical velocity (Pa/s), commonly denoted as omega. The approximate relationship used is:
rgas = 287.058 ; J/(kg-K) => m2/(s2 K) g = 9.80665 ; m/s2 rho = p/(rgas*t) ; density => kg/m3 omega = -w*rho*g ; array operation
See Also
omega_to_w, wind_direction, wind_component
Examples
Example 1: If (a) w[*], p[*] and t[*]; (b) w[*][*][*], p[*][*][*] and t[*][*][*]; (c) w[*][*][*][*], p[*][*][*][*] and t[*][*][*][*] and all have the desired units then:
oa = w_to_omega(w, p, t) ; oa[*] (Pa/s) ob = w_to_omega(w, p, t) ; ob[*][*][*] (Pa/s) oc = w_to_omega(w, p, t) ; oc[*][*][*][*] (Pa/s)
Example 2: Let w(time,lev,lat,lon) and t(time,lev,lat,lon) and plevel(lev) have units mm/day, degC and hPa, respectively.
; change units: mm/day to Pa/s w = w*/(1000.*86400.) ; 1m/1000mm, 86400s/day; (mm/day)(day/86400s)(m/1000mm) omega@units = "Pa/s t = t + 273.15 ; degC -> degK t@units = "degK" ; make p[*] conform to w[*][*][*][*] P = conform(w, p, 1) ; P(:,:,:,:) P = P*100 ; hPa -> Pa P@units = "Pa" omega = w_to_omega(w, P, t) ; omega[*][*][*][*] (Pa/s) delete(P) ; no longer needed