Wavelength exponent for haze scattering in the tropics as determined by photoelectric photometers

Sun photometers using narrow-band interference filters, photoelectric sensors and solid-state operational amplifiers were constructed and intensive measurements of the hazeextinction co-efficients at 0.40 and 0.60 pm wavelengths made at Poona (Lat. 18" N)over a one-year period. The most significant result obtained is that the wavelengthexponent for the haze scattering as calculated from 520 pairs of simultaneous observa-tions shows a median value of 0.5 and a mode of about 0.8. These are substantiallylower than corresponding values found in the case of middle latitude stations. Ingeneral, the exponent is correlated positively with the turbidity itself in the case of wethaze, and under conditions of very clear and dry air it assumes near zero values. Amarked diurnal variation in the value of the exponent occurs during the regimesof tropical continental air. The consequences of the prevailing lower values of u inrelation to determination of the hgstrom turbidity coefficient p in the tropics arebriefly discussed.