Particle backscattering variability in the coastal waters of Bay of Bengal: a case study along off Kakinada and Yanam regions

Abstract

The distribution and variability of particulate back scattering coefficient (bbp) in the Godavari basin are reported for the first time using in situ measurements. A coastal cruise was conducted in the coastal waters Off Kakinada and Yanam along the East coast of India, from 2-9 March 2012. Hyperspectral underwater radiometer was used to collect the in situ bio-optical data as function of wavelength in 21 sampling stations from the coast ( ∼10 m) to toward the open ocean ( ∼150 m). Data from these sites exhibits two orders of magnitude in bbp and covered the typical coastal and estuarine waters. The bbp at a single wavelength, i.e. 700 nm was measured with the embedded echo-VSF (Wetlabs) series sensor. In this letter, an attempt was made to: 1) describe the variability of particle bbp of estuarine coastal system using in situ measurements; 2) model the bbp from Quasi Analytical Algorithm (QAA) and verify its accuracy by comparing with in-situ measurements of bbp; and 3) examine the relationship of bbp and chlorophyll-a concentration in the coastal system. A significant relationship was observed between the in-situ and model derived bbp values. The in-situ measured bbp values vary from 0.01 to 0.065 m^-1 in this region. The relationship between chlorophyll-a concentration and the bbp has been studied. The large spread in the scatter in the chlorophyll vs. in-situ bbp infers that chlorophyll-a is a poor predictor of bbp. The relationship between chlorophyll-a concentration and the bbp shows an inverse relationship for the Godavari Estuarine waters.