Effects of changes in atmospheric water vapor content on physical properties of atmospheric aerosols at a coastal station

observational results are presented on the effects of changes in the atmospheric water vapor content (W g cm(-2)) on spectral optical depth (tau(p lambda)) and the retrieved columnar size distributions of atmospheric aerosols over a natural, coastal environment obtained from simultaneous estimates of these parameters (tau(p lambda) and W) using a ground based multiwavelength solar radiometer. It is found that, during meteorologically calm periods (i.e. in the absence of any significant air mass types), the aerosol optical depths increase with increase in W,with the shorter wavelengths being more sensitive to the changes in W,compared to the near infrared (TR) wavelengths. The aerosol (columnar) size distributions, retrieved from tau(p lambda) as a function of W, are found to change from bimodal for very low values of W to unimodal for higher values of W. The mean radius and mode radii of the retrieved size distributions also increase with increase in W. (C) 1998 Elsevier Science Ltd. All rights reserved.