Assessment of Accuracy of Indian Almanac for Daily Rainfall Prediction

Abstract

Background/Objectives: Modern science is able to predict various aspects of weather including rainfall, but it still does not provide high accuracy when we consider longer duration predictions in the future, which are very important for Agriculture. In countries like India, Ancient knowledge-based rainfall predictions are being made till this day. This research paper is an attempt to predict daily rainfall based on a limited implementation of rules from various Panchangs, and assessment of accuracy of these predictions in an unbiased manner. Methods: These predictions have been compared against the revalidated and actual daily rainfall data for accuracy calculation. We have assessed accuracy for overall 30 versions/test scenarios, which contain 7 versions of Traditional Maharashtrian Panchang, 8 versions of Telugu Panchang, 1 version of Saptanadi. This is followed by 4 scenarios of comparison with actual data and 4 with Hourly predictions vs data. Findings: We achieved a respectable accuracy of 81%(For Traditional Maharashtrian Panchang) and 79% (Telugu Panchang) when tested with 40 years of revalidated daily rainfall data between 1st Jan 1980 to 31st Aug 2020 across the world in India and other continents. Novelty: The comparison is based on daily rainfall accuracy which has not been seen before. Also, for the first time, we are able to prove the global applicability of the Panchang rules for precipitation prediction. This study is not intended to comment on the overall accuracy of any of the Panchangs, makes best possible combination useful to Indian farmer. We intend to make these predictions available as a website and an API to make this research directly usable. Keywords: Panchang; Conjunctions; Nakshatras; Ecliptic Longitude; Right Ascension; Rainfall Prediction; Weather Prediction