如何運用 Ferret 來計算與分析資料?

• 指令：let

• 使用方式：

  1. 四則運算
     EX:
     let var1=(var2+var3)-var4*var5/var6

  2. 指數運算
     EX:
     let var1=var2^n (n=R)

  3. @____ 相關指令的使用

     • 平均 (@ave)

       let var1=var2[x=@ave,y=@ave,z=@ave,...]

       let var1=var2[i=@ave,j=@ave,k=@ave,...]

       let var1=var2[x=x_start:x_end@ave,y=y_start:y_end@ave,...]

       let var1=var2[i=i_start:i_end@ave,j=j_start:j_end@ave,...]

       EX:
       let sst1999=sst[t="01-jan-1999":"31-dec-1999"@ave]

     • 內插 (@lin)

       let var1=var2[x=x_axis@lin,y=y_axis@lin,z=z_axis@lin,...]

       let var1=var2[i=i_axis@lin,j=j_axis@lin,k=k_axis@lin,...]

       EX:
       let sst_ge=sst[g=ge@lin]

  4. 將散佈資料內插至格點上

     • Gaussian

       SCAT2GRIDGAUSS_XY SCAT2GRIDGAUSS_XZ SCAT2GRIDGAUSS_YZ

     • Laplace spline interpolation

       SCAT2GRIDLAPLACE_XY SCAT2GRIDLAPLACE_XZ SCAT2GRIDLAPLACE_YZ

       EX:
       Supposing that you have a random SST data file "SST_SCS.DAT" in the SCS.
       LON LAT SST
099 020 028
100 025 030
... ... ...
define axis/x=99E:124E:1 xx
define axis/y=2N:27N:1 yy
file/var="lon_sst,lat_sst,sst"/col=3/skip=1 SST_SCS.DAT
let sst_scs=SCAT2GRIDLAPLACE_XY(lon_sst,lat_sst,sst,xx,yy,.5,.5,.5,.5)