calc_etadot Program

Prepare input data for FLEXPART, esp. vertical velocity as etadot or etadot * dp/deta

author: L. Haimberger date: 03/2010 version: V4.0

Program calc_etadot

Prepares input data for POP model meteorological preprocessor

Calculation of etapoint on a regular $\lambda-\phi$ grid and writing U,V,ETAPOINT,T,PS,Q,SD,MSL,TCC,10U, 10V, 2T,2D,LSP,CP,SSHF,SSR, EWSS,NSSS to an output file (input and output in GRIB 1 or 2 format).
etapoint is defined as the total time derivative of ECMWF vertical coordinate eta multiplied by the derivative of pressure with respect to eta: $$\frac{\mathrm{d}\eta}{\mathrm{d}t}\frac{\partial p}{\partial \eta}$$

Version history and authors:

• 04/1994: Leopold Haimberger, Gerhard Wotawa

• 2003-05-11: Alexander Beck

• 12/2006: L. Haimberger V2.0, handle arbitrary regular grids and T799 resolution data

• 03/2010: L. Haimberger V4.0, handle GRIB edition 2 fields and T1279 resolution data

• 04-06/2019: Petra Seibert, beautify code and add FORD documentation
• 06/2020: Petra Seibert, translate some comments into English comment out writing of VERTICAL.EC

Input required:

 UNIT  FILE      PARAMETER(S)    DATA REPRESENTATION

 11    fort.11   T,U,V           regular lat-lon grid
 12    fort.12   D               regular lat-lon grid   
 13    fort.13   LNSP            spherical harmonics
 14    fort.14   SD,MSL,TCC,10U,                                
                 10V,2T,2D       regular lat-lon grid     
 16    fort.16   LSP,CP,SSHF,         
                 SSR,EWSS,NSSS   regular lat-lon grid
 17    fort.17   Q               regular lat-lon grid

Output produced:

UNIT  FILE      PARAMETER(S)      DATA REPRESENTATION

15    fort.15   `U,V,ETA,T,PS,                                  
                `Q,SD,MSL,TCC,`                                  
                `10U,10V,2T,2D,`  regular lat-lon grid         
                `LSP,CP,SSHF,`                                   
                `SSR,EWSS,NSSS`

ALLOCATE VARIABLES

Initialise Legendre transformation on the lat-lon grid

Initialisation of fields for FFT and Legendre transformation to Gaussian grid and back to phase space read LNSP in SH read u,v in SH Transforming the wind to the Gaussian grid read DIV in SH Transform horizontal divergence to the Gaussian grid Calculation of the gradient of LNSP (log of surface pressure) on Gaussian grid
Calculation of the vertical velocity on the Gaussian grid
Calculation of omega on the Gaussian grid

READING OF SURFACE PRESSURE

READING OF U,V

READING OF LNSP on grid

READING OF DIVERGENCE

Initialise Legendre transformation on the lat-lon grid. Without Gaussian grid calculation, Legendre polynomials are calculated only for one latitude, to save space

READING OF T

READING OF SPECIFIC HUMIDITY

WRITE MODEL LEVEL DATA TO fort.15