advection

an advection model on the sphere using a Gaussian latitutude-
lontitude grid

[Takeshi Enomoto](mailto:[email protected])

### Prerequisite

* A Fortran compiler. Tested with [g95](http://www.g95.org)
* FFTW 3.3 [home page](http://www.fftw.org/)

### Compilation

* Edit Makefile
 - FC, FFLAGS and LDFLAGS (path to libfftw3*.*)

### Tests

* go_adv: the Gaussian hill test of Ritchie (1987)
* go_adv2: tracer transport test case of Lauritzen et al., submitted to JCP

### namelists
* planet
 - planet_radius: radius of the planet
 - day_in_sec: definition of a day (s)
* grid
 - nlon: number of zonal grid points
 - nlat: number of meridional grid points (=nlon/2
 - ntrunc: truncation wave number
           quradratic grid: nlon/3-1
           linear grid: nlon/2-1
 - phi0: initial tracer distribution
     ghill: a single Gaussian hill (Ritchie 1987)
     ghill2: two Gaussian hills (Lauritzen et al.)
     cbell2: two cosine bells
     scyli2: two slotted cyliners
     ccbell2: two correlated cosine bells
 - wind: background flow
     sbody: solid body (Ritchie 1987)
     nodiv: non divergent (Lauritzen et al.)
     div: divergetn (Laurizen et al.) 
* time
 - nstep: number of steps
 - hstep: output interval
 - deltat: time step
 - etf: time filter coefficient (model=euler or nisl)
 - tau: time scale of numerical diffusion (model=euler or nisl)
 - model: advection scheme
     euler: Eulerian
     slag: semi-Lagrangian
     nisl: non-interpolating semi-Lagrangian
 - imethod: interpolation method (model=slag or nisl)
       NB. only bilin or polin2 when nisl
     bilin: bilinear
     polin2: 2D Lagrange
     linpol: 1d Lagrange (quasi-cubic of Ritchie et al. 1995)
     fd: bicubic with derivatives by finite difference 
     sph: spectral bicubic
     fdy: bicubic with zonal spectral derivatives and
          meridonal finite-difference derivatives
     spcher: Hermite with spectral derivatives in the zonal
          Lagrange in the meridional
 - imethoduv: interpolation for winds bilin or polin2
* semilag: options for semi-Lagrangian model
 - spectral: time integration in the spectral space
 - fmono: force quasi-monotonicity (Nair et al. 1999)
 - clip: limit interpolated value to between max and min
         (Ostiguy and Laprise 1990). Always T if fmono=T
 - conserve: fix global mass (Sun and Sun 2004)
* interpolate:
 - n: order of Lagrange interpolation (3 for cubic)
 - nhalo: number of halo