Investigations into the occurrence of evaporation ducts near Karachi

Refraction through the atmosphere is one of the propagation mechanisms of wireless signals traversing the atmosphere. Different refractive conditions can be prevalent at a particular place, height and time, depending on the weather conditions. Ducting and sub-refractive conditions can lead to Anomalous Propagation (ANAPROP). There could be evaporation ducts, surface ducts, surface-based ducts and elevated ducts. This study pertains to the first type of ducts, which are predominantly present on large sections of water. Wireless signals can get trapped in ducts and travel long distances without much loss. Any previous studies in this geographical region have not investigated the detailed statistics of evaporation ducts. This paper has used the Paulus-Jeske Method for the estimation of the height of the evaporation ducts near Karachi, using relevant meteorological data. The results of this study are compared with a historic global study into evaporation ducting as well as to another relevant study in Arabian Sea. The current investigations are indicative of seasonal trends in formation of ducts as well as a median/mean values greater than global average. The findings of this study are of vital importance for ship to ship, ship to shore, radar as well as mobile and satellite wireless communication in coastal and marine areas as these ducts have potential to anomalously affect such critical communication.