Alternative small scale meteorology input to a chemical transport ...

X_CROSS(I,J) = X0 + FLOAT(I)*RESOLN !x of cross points
Y_CROSS(I,J) = Y0 + FLOAT(J)*RESOLN !y of cross points
DELTA(I,J) = (XSSTA(M) - X_CROSS(I,J))**2 !all in meters
& + (YSSTA(M) - Y_CROSS(I,J))**2
C Find the minimum distance from station to x/y grid
IF(DELTA(I,J).LT.DELTAMIN) THEN
DELTAMIN = DELTA(I,J)
IMIN = I
JMIN = J
ENDIF
ENDDO
ENDDO
C Assign grid elevation to station elevation
ELEV_STA(M) = ELEV(IMIN,JMIN)
ENDDO
C Convert station density to sea level
PWR = (GAMMA_A/GAMMA - 1.) !the factor (gamma_a/gamma-1.)
DO M=1,NSSTA
T0(M) = TEMPK(M) + GAMMA*ELEV_STA(M)
RSTA_0(M)=RHO(M)*((1.-GAMMA*ELEV_STA(M)/T0(M))**(-1.*PWR))
ENDDO
C Inverse squared distance objective analysis
C Loop over the grid points
C Note: X_CROSS(I,J) and Y_CROSS(I,J) already computed above
DO J=1,NY
DO I=1,NX
SUM_DIST2 = 0.0 !Set to zero for each cycle
RHO_0(I,J) = 0.0 !Set to zero for each cycle
RH_GRD(I,J) = 0.0 !Set to zero for each cycle
C Internal loop over the stations
C XSSTA(m),YSSTA(m) are the coordinates of sfc stations
DO M=1,NSSTA
DELTAX2 = (X_CROSS(I,J)-XSSTA(M))*
& (X_CROSS(I,J)-XSSTA(M))
DELTAY2 = (Y_CROSS(I,J)-YSSTA(M))*
& (Y_CROSS(I,J)-YSSTA(M))
D2 = (DELTAX2 + DELTAY2)
C Set minimum squared distance of 0.001
IF (D2.LE.0.001) D2 = 0.001
C Inverse square distance
DIST2 = 1./D2
SUM_DIST2 = SUM_DIST2 + DIST2
RHO_0(I,J) = RHO_0(I,J) + RSTA_0(M)*DIST2
RH_GRD(I,J) = RH_GRD(I,J)+FLOAT(IRH(M))*DIST2
ENDDO
RHO_0(I,J) = RHO_0(I,J)/SUM_DIST2
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