c======================================================================= subroutine o2cont(v,sigma,alpha,beta) 1,1 c c this routine is driven by frequency, returning only the c o2 coefficients, independent of temperature. c c ******************************************************************* c * these comments apply to the colume arrays for: * c * pbar*ubar(o2) * c * pbar*ubar(o2)*dt * c * and pbar*ubar(o2)*dt*dt where: dt=tbar-220. * c * that have been compiled in other parts of the lowtran code * c * * c * lowtran7 compatible: * c * o2 continuum subroutine for 1395-1760cm-1 * c * modified by g.p. anderson, april '88 * c * * c * the exponential temperature employed in the fascod2 algorithm * c * (see below) is not readily suitable for lowtran. therefore * c * the exponentials have been linearly expanded, keeping only the * c * linear and quadratic terms: * c * * c * exp(a*dt)=1.+ a*dt + (a*dt)**2/2. + .... * c * * c * exp(b*dt*dt)=1.+ b*dt*dt + (b*dt*dt)**2/2. + .... * c * * c * the product of the two terms is: * c * * c * (1. + a*dt + (a*a/2. + b)*dt*dt ) * c * * c * this expansion only works well for small values of x in exp(x) * c * * c * since dt = t-220., the approximation is very good until * c * t.gt.260. or dt.gt.40. at t=280, the maximum errors are still* c * less than 10% but at t=300, those errors are as large as 20% * c ******************************************************************* c c the following comments are excerpted directly from fascod2 c c this subroutine contains the rogers and walshaw c equivalent coefficients derived from the theoretical c values supplied by roland drayson. these values use c the same data as timofeyev and agree with timofeyev's results. c the data are in the form of strengths(o2so) and two c coefficients (o2a & o2b), which are used to correct for c temperature. the dependency on pressure squared c is contained in the p*wo2 part of the constant. c note that since the coefficients are for air, the c the strengths are divided by the o2 mixing ratio for c dry air of 0.20946 (this is assumed constant). c original formulation of the coefficients was by larry gordley. c this version written by earl thompson, july 1984. c c common/o2c/ o2dray(74),o2c001(74),o2s0(74),o2a(74),o2b(74), x v1o2,v2o2,dvo2,npto2 sigma =0 alpha =0 beta =0 if(v .lt. 1395) go to 30 if(v .gt. 1760) go to 30 c c call o2int(v,v1o2,dvo2,npto2,c,o2s0,a,o2a,b,o2b) c c c c old 'fascod2' temperature dependence using block data arrays c c c(j)=o2s0(i)* exp(o2a(i)*td+o2b(i)*td*td) /(0.20946*vj) c c new coefficient definitions for lowtran formulation c alpha= a beta=a**2/2.+b sigma=c/0.20946 c c new 'lowtran7' temperature dependence c c this would be the coding for the lowtran7 formulation, but c because the t-dependence is included in the amounts, only c the coefficients (sigma, alpha & beta) are being returned c c c(j)=sigma*(1.+alpha*td+beta*td*td) c 30 return end