Investigating the Temporal Variability of the Standardized Precipitation Index in Lebanon

Peter Mahfouz,Mireille Jazi,Fadi Karam,George Mitri

doi:10.3390/cli4020027

Abstract

The impact of global climate change on Lebanon’s society, environment, and economy is expected to be tremendous. Indices have been developed to help in the identification and monitoring of drought and characterization of its severity. In this context, this work aimed at assessing the temporal variability of the Standardized Precipitation Index in Lebanon for improved understanding of drought occurrence. This is expected to help in mitigation and response actions to future drought circumstances across the country. The methodology of work involved the calculation of the Standardized Precipitation Index over different time series from four regions across the country using both the Variability Analysis of Surface Climate Observations (VASClimO) gridded rainfall dataset for the period 1951–2000 and the European rainfall dataset E-OBS for the period 1950–2014. In general, higher precipitation values were recorded by the VASClimO dataset than those coming from the E-OBS dataset. Intra-annual precipitation changes showed increasing precipitation starting in September-October and decreasing precipitation starting in February. The VASClimO dataset showed a 50% increase in the frequency of severe drought conditions, while the E-OBS dataset indicated a 60% increase in the frequency of moderate drought conditions. In addition, it was observed that the winter of 2014, characterized by extreme drought conditions, was the driest in the past 56 years. Although specific years were commonly characterized by severe to extreme drought conditions with the use of both datasets, considerable differences between the two datasets were observed with respect to the identification of the degree of wet and dry conditions for some other years. Overall, trend lines for the Standardized Precipitation Index values, as derived from VASClimO and E-OBS datasets, commonly point to a relatively slight increase in drought conditions mainly in the winter-spring season; however, the situation on the ground could vary greatly given that many other environmental factors (e.g., changes in land cover) may also play an important role in affecting drought conditions.

Highlights

Climate change is expected to increase the risk of drought in some areas of the world and the risk of extreme precipitation and flooding in others [1]
Results from processing VASClimO datasets were used for studying general precipitation characteristics and analyzing trends in drought conditions for the period 1951–2000
Standardized Precipitation Index [19] (SPI) was calculated from monthly precipitation values of four center points from the gridded VASClimO and E-OBS datasets

Summary

Introduction

Climate change is expected to increase the risk of drought in some areas of the world and the risk of extreme precipitation and flooding in others [1]. As increases in droughts over low and mid-latitudes are projected [2], a decrease in summer precipitation in southern Europe and across the Mediterranean region, accompanied by rising temperatures, would inevitably lead to reduced summer soil moisture and more frequent and intense droughts [3]. In this regard, [4] found that precipitation changes under. The frequency of a drought event is usually expressed by its return period or occurrence interval, which may be defined as the average time lag between two events of the considered magnitude or larger magnitude [12]

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Conclusion