Statistical Model of Cloud Optical Depths in Certain Zones of the Yamal Peninsula Region Using Satellite Data

Resumo

The optical depths of summertime clouds are statistically analyzed in the region of Ob Bay in three bounded zones over “dry” areas and areas comprising large water basins. We used experimental data, obtained onboard the European satellite ENVISAT (MERIS instrument) in 2008–2011. The shape of the probability distribution functions of the optical depths in each of the zones is determined. These functions have 3–4 modes in logarithmic coordinates. The functions were fit using a set of normal logarithmic distributions with adjusted parameters, found to be well repetitive from one year to another. The water-poor western zone is characterized by three modes; and for eastern zones, with northward-flowing rivers full of relatively warm waters, the number of modes increases to four. Very likely, the additional mode at small optical depths is explained by water evaporation, followed by condensation of water vapor. It is hypothesized that a certain role in the latter case may be played by anthropogenic emissions, owing to which the number of condensation nuclei in the atmosphere is larger in the eastern than the western zone. We present the plots of the distribution functions and tables of fit parameters that define these functions. These data may be useful in calculation of radiation budget for small territories in the region of the Yamal Peninsula.