Dry spells in the River Plata Basin: an approximation of the diagnosis of droughts using daily data

Abstract

This study addresses the dry spells observed in the La Plata Basin using daily data from 94 observation stations during sampling periods from 1900 to 2005. Dry days were defined as having less than 0.3 mm of accumulated precipitation. This definition allowed for the assessment of the dryness in the La Plata Basin and a comparison with other regions. The main purpose of this study was to analyse dry spells, especially extreme cases (meteorological droughts), and assess them on a daily basis. Trends and low frequency of droughts were analysed using a general framework to detect and compare properties of dry states based on daily and annual time scales. The trends were estimated using two different methods. Overall, the trends showed a decrease, especially in the eastern basin region during the period of 1972-1996. The results showed sporadic decreases in dry events and events of extreme dryness (droughts). Spectral structure permits an inference of low-frequency maxima and confirmed an inter-annual 2-to 3-year period of variability in drought occurrence for most of the basin. Furthermore, probabilistic distribution functions of dry spells at basin stations were analysed to confirm that they followed a geometric-binomial distribution. Additional tests were used to determine whether there was a second threshold, using the Weibull and gamma adjustment models. In order to study spatial homogeneity, the field of dry spell maxima in the basin was generated using a vector array based on the occurrence date and length of the maximum spell. Due to the dependence of spell length on the annual cycle, the longest spells were observed from April to the beginning of winter in the Argentine northwest region and in the northern and western regions of the basin. The intensity of droughts decreased in the Pampas and Mesopotamia regions. The drought of 1988 was considered to be the longest dry spell in the basin. The water deficits from this drought resulted in Argentinean economic losses of more than four billion US dollars during 1988.

An Optimized System for the Classification of Meteorological Drought Intensity with Applications in Drought Frequency Analysis

“…Latin America spans a vast range of latitudes and has a wide variety of climates. It is characterized largely by humid and tropical conditions, but important areas have been affected by ''extreme'' droughts in the past (e.g., Phillips et al 2009;Sheffield et al 2009;Zhao and Running 2010;Vargas et al 2011) and climate change projections suggest an increased frequency of such events for the region (e.g., Magrin et al 2007;Allen et al 2012). Given the significant reliance of Latin American economies on agricultural production, and the exposure of agriculture to a variable climate, there is a large concern in the region about present and future climate and climate-related impacts (Trenberth and Stepaniak 2001).…”

Analysis of Current and Future SPEI Droughts in the La Plata Basin Based on Results from the Regional Eta Climate Model

“…Several authors have focused their work on specific drought spells that occurred over certain regions within the La Plata Basin (e.g., [2][3][4][5][6][7]). Comprehensive works on droughts were mostly conducted on monthly time-scales (e.g., [3,[8][9][10][11]) and a few on daily time-scales [4,12]. In general, they showed a decrease of drought spells after the mid-1970s.…”

“…Dufek et al [16] reported a 7-9% increase in the number of warm nights and a 5%-9% decrease in the number of cold nights in most of the region during . Much literature describes severe droughts in recent years [5,6,12,[17][18][19][20].…”

Prolonged dry episodes over Northeast China during the period 1961–2012

“…The same precipitation total and number of dry days will have quite different effects when the dry days are homogenously distributed in time or concentrated in a few dry spells (Zolina et al 2013). Therefore, dry spells form a useful index being helpful for a better and more comprehensive understanding of droughts and has also been widely used all over the world (Cindric et al 2010;Deni and Jemain 2009;Deni et al 2010;Lana et al 2006;Lana et al 2008;Modarres 2010;Schmidli and Frei 2005;Vargas et al 2011). Several researches about dry spells have also been conducted over China (Gong et al 2005;Lei and Duan 2011).…”