Gap-Filling of Ocean Color Over the Tropical Indian Ocean Using Monte-Carlo Method

Abstract

Continuous remote-sensed daily fields of ocean color now span over two decades; however, it still remains a challenge to examine the ocean ecosystem processes, e.g., phenology, at temporal frequencies of less than a month. This is due to the presence of significantly large gaps in satellite data caused by clouds, sun-glint, and hardware failure; thus, making gap-filling a prerequisite. Commonly used techniques of gap-filling are limited to single value imputation, thus ignoring the error estimates. Though convenient for datasets with fewer missing pixels, these techniques introduce potential biases in datasets having a higher percentage of gaps, such as in the tropical Indian Ocean during the summer monsoon, the satellite coverage is reduced up to 40% due to the seasonally varying cloud cover. In this study, we fill the missing values in the tropical Indian Ocean with a set of plausible values (here, 10,000) using the classical Monte-Carlo method and prepare 10,000 gap-filled datasets of ocean color. Contrary to the previously used gap-filled datasets, the ecological indicators derived using our gap-filled datasets also quantifies uncertainty indicating the likelihood of estimates. Quantification of uncertainty is critical to address the importance of underlying datasets and hence, motivating future observations.

Recommendations of the 15th Union Finance Commission: Expectations and Realities

“…The 15th UFC fails to draw lessons from the outcome of recommendations made by the 14th UFC on vertical and horizontal devolution. The newly added dimensions of contribution towards national defence by states keeping the share of vertical devolution untouched may increase vertical imbalance (Modi, 2021). The share of prescribed 42% revenue transfers to states by the 15th UFC may be lower than the 42% share of the 14th UFC, in absolute term, due to economic slowdown, which may further increase the imbalance (Ramachandran, 2021).…”