Abstract
Prediction of changes in precipitation in upcoming years and decades
caused by global climate change associated with the greenhouse effect,
deforestation, and other anthropic perturbations is a practical and
scientific problem of high complexity and consequences. To advance
toward this challenge, we look at the daily historical record of all
available rain gauges in Colombia and at the CHIRPS database of daily
precipitation fields to estimate the HY-INT index of the intensity of
the hydrologic cycle \cite{Giorgi2011}. The index is
the product of precipitation intensity and dry spell length. Theoretical
reasons indicate that global warming should lead to increasing trends in
either factor or both. Most of the gauges and pixels do not show a
significant trend. Nevertheless, among gauges and pixels with
significant trends, the majority (70\%) exhibit a
decreasing trend. The geographic distribution of results does not agree
between gauges and CHIRPS. We obtain a majority of increasing trends
among the 10\% of the stations and 13\%
of the CHIRPS pixels with a statistically significant trend for total
annual precipitation. This result agrees with previous reports. The sign
of the trends for rainfall intensity, number of wet days, the average
and maximum length of wet runs is opposite between the two data sets. A
possible explanation is the space coverage of the two datasets. There
are very few rain gauges in the eastern part of the country, and CHIRPS,
with total coverage, shows an East-West dipole in the trends of those
variables.