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根据http://bbs.06climate.com/forum.php?mod=viewthread&tid=9495帖子中分析等熵位涡的gs.我是利用wrf输出的资料进行计算,脚本如下,然而出现了grads闪退,有时还有出现isen函数无法识别的问题,求各位帮我看看,如何改?谢谢
'reinit'
'open d:\uprs.ctl'
'open d:\vprs.ctl'
'open d:\tkprs.ctl'
'set lon 113 122'
'set lat 28 35'
'set lev 1000 100'
'set t 1'
'define tt=tk.3'
'define u=u'
'define v=v.2'
'define pp=lev'
'define coriol=2*7.29e-5*sin(lat*3.1415/180)'
'define dudy=cdiff(u,y)/(111177*cdiff(lat,y))'
'define dvdx=cdiff(v,x)/(111177*cdiff(lon,x)*cos(lat*3.1415/180))'
'define dt=tt(z-1)*pow(1000/pp(z-1),0.286)-tt(z+1)*pow(1000/pp(z+1),0.286)'
'define dp=100*(pp(z-1)-pp(z+1))'
'define dtdp=dt/dp'
'define part1='isen(dvdx,tt,lev,300)
'define part2='isen(dudy,tt,lev,300)
'define part3='isen(dtdp,tt,lev,300)
'define pv300=-9.8*(coriol+part1-part2)*part3'
'set z 2'
'set lon 113 122'
'set lat 28 35'
'd pv300*1000000'
'printim d:\2.jpg x1024 y768 white'
function isen(field,tgrid,pgrid,tlev)
*----------------------------------------------------------------------
* Bob Hart (hart@ems.psu.edu) / PSU Meteorology
* 2/26/1999
*
* 2/26/99 - Fixed a bug that caused the script to crash on
* certain machines.
*
* GrADS function to interpolate within a 3-D grid to a specified
* isentropic level. Can also be used on non-pressure level data, such
* as sigma or eta-coordinate output where pressure is a function
* of time and grid level. Can be used to create isentropic PV surfaces
* (examples are given at end of documentation just prior to
* function.)
*
* Advantages: Easy to use, no UDFs. Disadvantages: Can take 5-20 secs.
*
* Arguments:
* field = name of 3-D grid to interpolate
*
* tgrid = name of 3-D grid holding temperature values (deg K) at each
* gridpoint.
*
* pgrid = name of 3-D grid holding pressure values (mb) at each gridpoint
* If you are using regular pressure-level data, this should be
* set to the builtin GrADS variable 'lev'.
*
* tlev = theta-level (deg K) at which to interpolate
*
* Function returns: defined grid interp holding interpolated values
*
* NOTE: YOU NEED TO INCLUDE A COPY OF THIS FUNCTION IN YOUR SCRIPT
*
* NOTE: Areas having tlev below bottom level or above upper level
* will be undefined in output field. Extrapolation is NOT
* performed!!
*
*------------------------------------------------------------------------
*
* EXAMPLE FUNCTION CALLS:
*
* Sample variables: u = u-wind in m/s
* v = v-wind in m/s
* w = vertical velocity
* t = temperature in K
* PP = pressure data in mb
*
* 1) Display vertical velocity field on 320K surface:
*
* "d "isen(w,t,PP,320)
*
* 2) Create & Display colorized streamlines on 320K surface:
*
* "define u320="isen(u,t,PP,320)
* "define v320="isen(v,t,PP,320)
* "set z 1"
* "set gxout stream"
* "d u320;v320;mag(u320,v320)"
*
* 3) Create & display a 320K isentropic PV surface:
*
* "set lev 1050 150"
* "define coriol=2*7.29e-5*sin(lat*3.1415/180)"
* "define dudy=cdiff(u,y)/(111177*cdiff(lat,y))"
* "define dvdx=cdiff(v,x)/(111177*cdiff(lon,x)*cos(lat*3.1415/180))"
* "define dt=t(z-1)*pow(1000/PP(z-1),0.286)-t(z+1)*pow(1000/PP(z+1),0.286)"
* "define dp=100*(PP(z-1)-PP(z+1))"
* "define dtdp=dt/dp"
* "define part1="isen(dvdx,t,PP,320)
* "define part2="isen(dudy,t,PP,320)
* "define part3="isen(dtdp,t,PP,320)
* "define pv320=-9.8*(coriol+part1-part2)*part3"
* "set z 1"
* "d pv320"
*
* PROBLEMS: Send email to Bob Hart (hart@ems.psu.edu)
*
*-----------------------------------------------------------------------
*-------------------- BEGINNING OF FUNCTION ----------------------------
*-----------------------------------------------------------------------
* Get initial dimensions of dataset so that exit dimensions will be
* same
"q dims"
rec=sublin(result,4)
ztype=subwrd(rec,3)
if (ztype = "fixed")
zmin=subwrd(rec,9)
zmax=zmin
else
zmin=subwrd(rec,11)
zmax=subwrd(rec,13)
endif
* Get full z-dimensions of dataset.
"q file"
rec=sublin(result,5)
zsize=subwrd(rec,9)
* Determine spatially varying bounding pressure levels for isen surface
* tabove = theta-value at level above ; tbelow = theta value at level
* below for each gridpoint
"set z 1 "zsize
"define theta="tgrid"*pow(1000/"pgrid",0.286)"
"set z 2 "zsize
"define thetam="tgrid"(z-1)*pow(1000/"pgrid"(z-1),0.286)"
"set z 1 "zsize-1
"define thetap="tgrid"(z+1)*pow(1000/"pgrid"(z+1),0.286)"
"define tabove=0.5*maskout(theta,theta-"tlev")+0.5*maskout(theta,"tlev"-thetam)"
"define tbelow=0.5*maskout(theta,thetap-"tlev")+0.5*maskout(theta,"tlev"-theta)"
* Isolate field values at bounding pressure levels
* fabove = requested field value above isen surface
* fbelow = requested field value below isen surface
"define fabove=tabove*0+"field
"define fbelow=tbelow*0+"field
"set z 1"
* Turn this 3-D grid of values (mostly undefined) into a 2-D isen layer
* If more than one layer is valid (rare), take the mean of all the
* valid levels. Not the best way to deal with the multi-layer issue,
* but works well, rarely if ever impacts output, and is quick.
* Ideally, only the upper most level would be used. However, this
* is not easily done using current GrADS intrinsic functions.
"define fabove=mean(fabove,z=1,z="zsize")"
"define fbelow=mean(fbelow,z=1,z="zsize")"
"define tabove=mean(tabove,z=1,z="zsize")"
"define tbelow=mean(tbelow,z=1,z="zsize")"
* Finally, interpolate linearly in theta and create isen surface.
* Linear interpolation in theta works b/c it scales as height,
* or log-P, from Poisson equation for pot temp.
"set z "zmin " " zmax
"define slope=(fabove-fbelow)/(tabove-tbelow)"
"define b=fbelow-slope*tbelow"
"define interp=slope*"tlev"+b"
* variable interp now holds isentropic field and its named it returned
* for use by the user.
say "Done. Newly defined variable interp has "tlev"K "field"-field."
return(interp)
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