C $Header: /u/gcmpack/MITgcm/pkg/streamice/eta_gl_prime_streamice.F,v 1.1 2016/11/29 14:20:16 dgoldberg Exp $ C $Name: $ #include "CPP_OPTIONS.h" _RL FUNCTION ETA_GL_PRIME_STREAMICE (X, M1, M2, Y0, W) ! This function returns the derivative of ETA_GL_STREAMICE ! w.r.t. its first argument ! X: input variable ! M1: slope of y where x<0 ! M2: slope of y where x>0 ! Y0: value of y at 0 ! W: width of smoothing _RL X, M1, M2, Y0, W _RL TMP1, PI IF (X.le.-0.5*W) THEN ETA_GL_PRIME_STREAMICE = M1 ELSEIF(X.gt.0.5*W) THEN ETA_GL_PRIME_STREAMICE = M2 ELSE PI = 3.14159265358979323844D0 TMP1 = SIN (PI*X/W) ETA_GL_PRIME_STREAMICE = & 0.5*M1 * (1-TMP1) + & 0.5*M2 * (1+TMP1) ENDIF RETURN END