Seasonality of Rainfall in Colombia
Viviana Urrea1, Andrés Ochoa1, and Oscar Mesa1
1Facultad de Minas, Departamento de Geociencias y Medio Ambiente, Universidad Nacional de Colombia Sede
Medellin, Medellin, Colombia
Abstract The knowledge of the annual cycle of rainfall is of primary concern for many socioeconomic
activities such as agricultural planning, electricity generation, and flood and other disaster management.
The annual cycle of rainfall in Colombia has been studied so far using monthly or quarterly information,
identifying zones with the unimodal regime (one wet season and one dry season) over the Caribbean, the
Amazon, and the Pacific regions and zones with the bimodal regime (two wet and two dry seasons) in the
Andes. This paper explores the annual rainfall cycle in Colombia on a daily basis using historical records of
1,706 rain gauges and the Climate Hazards Group Infrared Precipitation with Station data precipitation
data set. We found four types of annual precipitation regimes: unimodal, bimodal, mixed, and aseasonal.
The unimodal regime predominates in the low-altitude zones of the east and the north, the bimodal and
mixed regimes over the Andes mountain range, and the aseasonal in the Pacific region. These results
improve the statistical diagnosis of the spatial variability of the rainfall seasonality in Colombia. This
phenomenon, however, is still far from being fully understood in its hydroclimatic context. The annual
migration of the Intertropical Convergence Zone is not enough to explain the diversity of rainfall regimes
in Colombia. Local factors such as topography and land cover could play an important role in the
occurrence and duration of rainfall seasons.
The fluctuation between rainy and dry periods is the main expression of climate seasonality in the tropics.
For instance, eighteen studies report the occurrence of two types of rainfall regimes in Colombia, those with
one dry season and one wet season and those with two dry and two wet seasons per year (e.g., Cochrane,
1825; Hettner, 1892; Mosquera, 1866; Wright, 1839). However, there is not a clear physical mechanism to
explain them. Several authors have pointed out the meridional migration of the Intertropical Convergence
Zone (ITCZ) as the main driver of the annual cycle of Colombia's hydroclimatology (Poveda & Mesa, 1997;
Poveda et al., 2006; Snow, 1976). The general picture set by the ITCZ is affected by other phenomena as
the Chocø low-level jet (Hoyos et al., 2017; Poveda & Mesa, 2000, 1999), the Caribbean jet (Hoyos et al.,
2017; Poveda et al., 2006; Poveda & Mesa, 1999), the atmospheric rivers (Montoya et al., 2001; Poveda et al.,
2014), the presence of the Andes mountain range (Garreaud, 2009; Guhl, 1974; Pagney, 1978), the advection
from the Amazon and Orinoco basins (Martínez et al., 2011; Poveda et al., 2006), and the El Niño–Southern
Oscillation (ENSO; Poveda et al., 2006, 2001).
The diagnosis of rainfall seasonality in Colombia has been made for a century using monthly or quarterly
data, identifying unimodal regions (with one dry season and one rainy season) and bimodal regions (two dry
and two rainy seasons). In fact, it is common to describe the rainy seasons in Colombia using the December
to February, March to May, June to August, and September to November quarters (see, e.g., Espinoza Villar
et al., 2009; Guhl, 1974; Martin, 1929; Mesa et al., 1997; Snow, 1976; Trojer, 1958, 1959). This monthly based
approach has two drawbacks: (1) it forces the duration of the seasons to be integer multiples of 1 month and
(2) the changes of a season can only occur at the end of the month.
In this paper, we overcome these two drawbacks by using daily rainfall time series. We use two data sources
(section 2): (a) the rain gauge network of the National Hydrological Service of Colombia (Instituto de
Hidrología, Meteorología y Estudios Ambientales, IDEAM) and (b) the Climate Hazards Group Infrared
Precipitation with Station data (CHIRPS v2.0; Funk et al., 2015) satellite product, with a spatial resolution of
0.05◦. We use a two-step method. The first step is to estimate the number of seasons at each site. This estima-
tion is done using the fraction of the variance explained (FVE) by the annual and semiannual components
revealed by the Fourier analysis of the long-term annual average cycle (LTAC). This approach has been used
• Four types of annual rainfall regimes
were identified: unimodal, bimodal,
mixed, and aseasonal
• Unimodal regime predominates
in the north, east, and southeast;
bimodal in the Andes; and aseasonal
in the west
• Intertropical Convergence Zone
migration, the Choco and Caribbean
low-level jets, and topography are
major controls of the rain seasonality
• Supporting Information S1
Urrea, V., Ochoa, A., & Mesa, O.
(2019). Seasonality of rainfall in
Colombia. Water Resources Research,
55, 4149–4162. https://doi.org/10.
Received 14 MAY 2018
Accepted 8 APR 2019
Accepted article online 23 APR 2019
Published online 22 MAY 2019
©2019. American Geophysical Union.
All Rights Reserved.
URREA ET AL. 4149