Abstract
Ship present-weather reports from 1950 through 2019 are used to assess
trends in the reporting of precipitation occurrence over the global
oceans. Annual reported precipitation frequency shows statistically
significant positive trends of up to
$\sim$15\% per decade throughout most
ocean areas equatorward of 45 degrees. However, latitudes poleward of 45
degrees are dominated by negative trends, some areas of which meet the
95\% confidence threshold. Nine smaller regions were
subjectively selected for further investigation, revealing that the
observed trends, both positive and negative, are often but not always
nearly linear, with the amplitude of interannual fluctuations usually
being much larger than that expected from random sampling error alone.
The annual time series reveal that four comparatively dry areas are
associated with the largest overall positive trends, ranging from
8.3\% to 12.8\% (relative) per decade.
Trends were also computed separately for each season, revealing
remarkable overall consistency in trends across seasons.