Mid-Century Changes in the Mean and Extreme Climate in the Kingdom of Saudi Arabia and Implications for Water Harvesting and Climate Adaptation

Muge Komurcu,Tariq Alshahrani,Ibtihal Alshehri,Waleed Alhayaza,C Adam Schlosser,Kenneth Strzepek,Adnan Alsaati

doi:10.3390/atmos11101068

Abstract

The Kingdom of Saudi Arabia (KSA) is a water-scarce region with a dry, desert climate, yet flood-producing precipitation events and heat extremes lead to loss of life and damages to local infrastructure, property and economy. Due to its distinctive natural and man-made spatial features (e.g., coastal features, wadis, agricultural areas) studying changes in the mean climate and extreme events requires higher-resolution climate projections than those available from the current generation of Earth System Models. Here, a high-resolution convection-permitting regional climate model is used to downscale the middle of the 21st century (2041–2050) climate projections of the Community Earth System Model (CESM) under representative concentration pathway (RCP) 8.5 and for a historical time period (2008–2017) focusing on two months (August and November) within KSA’s dry-hot and wet seasons, where extreme events have historically been observed more frequently. Downscaling of climate reanalysis is also performed for the historical time period (2008–2017) to evaluate the downscaling methodology. An increase in the intensity and frequency of precipitation events is found in August by mid-century, particularly along the mountainous western coast of KSA, suggesting potential for water harvesting. Conversely, the northern flank of the Empty Quarter experiences a noticeable reduction in mean and extreme precipitation rates during the wet season. Increasing August heat index is found to particularly make regional habitability difficult in Jeddah by mid-century.

Highlights

The Kingdom of Saudi Arabia (KSA) has a dry, hot climate with infrequent rainfall (e.g., [1]).Several studies show increasing trends in temperatures in station observations across KSA (e.g., [2,3,4,5]) as well as in gridded observational products (e.g., [6])
To evaluate our downscaling methodology, we focus on historical temperatures at 2 m and precipitation rates and compare our simulated climate fields from our Weather Research and Forecasting Model (WRF)-ERA and WRF-present-day value (PD)
In November, the negative biases are smaller in magnitude and extent along the western KSA in WRF-ERA simulations compared to August and even exhibit a narrow band of positive bias along the western coastline

Summary

Introduction

The Kingdom of Saudi Arabia (KSA) has a dry, hot climate with infrequent rainfall (e.g., [1]).Several studies show increasing trends in temperatures in station observations across KSA (e.g., [2,3,4,5]) as well as in gridded observational products (e.g., [6]). Almazroui et al (2014) investigated the trends of extreme temperatures in Saudi Arabia using observations from 27 ground-based stations for 30 years (1981–2010) and found that temperature extremes were higher in magnitude and more frequent for both cold and warm extremes during the most recent decade (1996–2010) of their analysis [4]. They reported a greater than 90% increase in the annual number of warm days and Atmosphere 2020, 11, 1068; doi:10.3390/atmos11101068 www.mdpi.com/journal/atmosphere. Combined effects of increasing temperatures and humidity pose threats to the continuation of life and daily activities of humans (e.g., [10])

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