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GrADS
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我不知道这里面的频率是什么频率,是Hz吗? |
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CC*******************************************************************
CC This program is used to filter the band-pass low-frequency *
CC and is useful to analyse the low-frequency characteristics *
CC of fields.But at first,you must specify the period of the *
CC date or field will be analysed,therefore,you can use this *
CC band-pass filter program to get the data or field you want. *
CC The program is from Zhang Fengqi,May.15,1996 and noted by *
CC Chen Mingxuan in Nanjing Institute of Meteorology,Jun.21,2000 *
CC*******************************************************************
CC***********************PARAMETER TABLE***************************CC
C PERL==> The left boundary of frequency ???? *
C PERR==> The right boundary of frequency ????? *
C IX ==> The number of grids !!网格数 *
C NX ==> The length of the time series *
C If you use the monthly data,for example ,let the parameter *
C PERL=14.0,and PERR=17.0,that means you will get the 14~17. *
C The primitive file data --> P(M,N): *
C M ==> the number of grids *
C N ==> the length of time series month period filtered data *
C and field . *
C The file unit 10 is the primitive file *
C The file unit 12 is the filtered file
C !!!!CALL GRKT1 (Y,W,F,D),GRKT1 (Y,W,F,D) 是个子程序,Y,W,F,D分别为子程序的参数,call为调用它!
C******************************************************************CC
ccc Notes:Dealing with singal time series,IX omitted.
program bandpass_filter_1
parameter(PERL=30,PERR=60)
parameter(NX=10950)
DIMENSION UU(NX),WK1(NX),WK2(NX)
OPEN(10,FILE='E\fortran\for\orl2.dat',
& form='binary',status='old')
READ(10)(UU(i),i=1,NX)
CLOSE(10)
CALL FILTER(1,UU,NX,1.0,PERR,PERL,WK1,WK2)
OPEN(12,FILE='E\fortran\for\orllb.dat',
& form='binary')
WRITE(12)(UU(i),i=1,NX)
CLOSE(12)
END
C**********************SUBROUTINE FUNCTION*************************CC
cc Tis subroutine is used to get the band-pass data or files cc get 是得到
CC*****************************************************************CC
SUBROUTINE FILTER(ITIME,AA,ITX,DT,PERR,PERL,WK1,WK2)
DIMENSION AA(ITX),WK1(ITX),WK2(ITX)
AM=0.0
DO 10 I=1,ITX
10 AM=AM+AA(I)
AM=AM/FLOAT(ITX)
DO 20 I=1,ITX
20 AA(I)=AA(I)-AM
IF(ITIME.NE.1) GO TO 100
PI2=2.0*3.1415926
W1=PI2/PERL
W2=PI2/PERR
DW=2.0*ABS((SIN(W1*DT))/(1.0+COS(W1*DT))-(SIN(W2*DT))
& /(1.0+COS(W2*DT)))
DWS=2.0*ABS((SIN(W1*DT))/(1.0+COS(W1*DT))-(SIN(W2*DT))
& *(1.0+COS(W2*DT)))
B3=(2.0*DW)/(4.0+2.0*DW+DWS)
B2=(4.0-2.0*DW+DWS)/(4.0+2.0*DW+DWS)
B1=(2.0*(DWS-4.0))/(4.0+2.0*DW+DWS)
100 CONTINUE
ITIME=ITX-1
DO 70 IT=1,ITX
70 WK1(IT)=0.0
DO 80 IT=3,ITX
80 WK1(IT)=B3*(AA(IT)-AA(IT-2))-B1*WK1(IT-1)-B2*WK1(IT-2)
WK2(ITX-1)=WK1(ITX)
WK2(ITX)=WK1(ITX)
WK1(1)=AA(1)
WK1(2)=AA(2)
DO 30 IT=2,ITXM
II=ITX-IT
30 WK2(II)=B3*(WK1(II)-WK1(II+2))-B1*WK2(II+1)-B2*WK2(II+2)
DO 40 IT=1,ITX
40 AA(IT)=WK2(IT)
RETURN
END
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