def _calc_d(aod700, p):
p0 = <NUM_LIT><EOL>dp = <NUM_LIT:1>/(<NUM_LIT> + <NUM_LIT>*aod700)<EOL>d = -<NUM_LIT>*aod700**<NUM_LIT:2> + <NUM_LIT>*aod700 + <NUM_LIT> + dp*np.log(p/p0)<EOL>return d<EOL>
Calculate the d coefficient.