The Effect of Sunspot Weighting
Leif Svalgaard, Marco Cagnotti, Sergio Cortesi

TL;DR
This paper investigates the inflation of sunspot counts caused by Waldmeier's weighting method, quantifies the over-counting, and proposes a correction to align historical data with the Wolfer method.
Contribution
It provides an empirical model to estimate and correct the over-counting in sunspot numbers due to weighting introduced in 1947.
Findings
Sunspot counts are overestimated by 44% on average due to weighting.
A simple empirical equation accurately models the weight factor over time.
The correction allows for consistent sunspot data from 1893 onwards.
Abstract
Waldmeier in 1947 introduced a weighting (on a scale from 1 to 5) of the sunspot count made at Zurich and its auxiliary station Locarno, whereby larger spots were counted more than once. This counting method inflates the relative sunspot number over that which corresponds to the scale set by Wolfer and Brunner. Svalgaard re-counted some 60,000 sunspots on drawings from the reference station Locarno and determined that the number of sunspots reported were 'over counted' by 44% on average, leading to an inflation (measured by a weight factor) in excess of 1.2 for high solar activity. In a double-blind parallel counting by the Locarno observer Cagnotti, we determined that Svalgaard's count closely matches that of Cagnotti's, allowing us to determine the daily weight factor since 2003 (and sporadically before). We find that a simple empirical equation fits the observed weight factors well,…
Peer Reviews
No public reviews on file for this paper yet. If you reviewed it on a platform where reviews are public (OpenReview, ICLR, NeurIPS, ICML), you can paste yours below so the community can read it here.
Videos
No videos yet. Explain this paper in a talk, walkthrough, or lecture? Add one.
