Drought regimes in Southern Africa and how well GCMs simulate them

This study aimed to characterize present and future drought changes over eastern China using observations and Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations. We used the standardized precipitation evapotranspiration index (SPEI) to characterize droughts at the timescales of 3‐ and 12‐month. We distinguished the spatial patterns of drought regimes (DRs) using the rotated empirical orthogonal function (EOF) on the SPEI. Our results identified three DRs centered in northern China (DR1), northeastern China (DR2), and southern China (DR3). Droughts in these regimes have increased in recent decades. Most CMIP5 models reproduce at least two of the DRs. The rotated EOF results indicate that the three DRs can jointly explain 46–68% of the SPEI variance (compared with approximately 60% in the observations). Among the 33 CMIP5 models analysed in this study, 13 simulated all three DRs well and showed a strong correlation pattern (>0.5). Further analysis indicated that both the external natural and greenhouse gas forcing experiments in CMIP5 reproduced the DRs, implying that natural variability and anthropogenic activity play important roles in the formation of these DRs. With continued climate warming, the three DRs over eastern China will persist. Despite the uncertainties in drought changes that mainly depend on the potential evapotranspiration methods, climate model results suggest that droughts would be aggravated under warming scenarios. The probability of severe droughts increase by the end of the century: 33% in DR1, 25% in DR2, 34% in DR3 in RCP4.5 and almost double in RCP8.5 scenario in Thornthwaite method based SPEI estimates.

Section: Methodsmentioning

confidence: 99%

Characterizing present and future drought changes over eastern China

Chen

Sun

2017

“…Given the extensive serious impacts of drought, understanding its causes in the past and projecting future drought conditions is an important task in drought studies, and has been well received in the literature. Many recent studies have employed various drought indices and have assessed trends in drought duration or severity (Dubrovský et al, 2014;Park et al, 2014;Yu et al, 2014;Duffy et al, 2015;Madhu et al, 2015;Swain and Hayhoe, 2015), investigated the relationship of drought and climate teleconnections (Kam et al, 2014;Huang et al, 2015;Meque and Abiodun, 2015;Ujeneza and Abiodun, 2015), or evaluated the causes of a particular drought event (Griffin and Anchukaitis, 2014;Diffenbaugh et al, 2015;Mao et al, 2015;Seager et al, 2015;Williams et al, 2015;Otkin et al, 2016). Improvements in accuracy and spatial resolution of datasets as well as greater availability and accessibility to ensembles of models with more realistic physical assumptions, allows for a better assessment of drought attributes in different regions while also characterizing the uncertainty of drought projections (Barnston and Lyon, 2016).…”

Section: Introductionmentioning

confidence: 99%

Centennial drought outlook over the CONUS using NASA‐NEX downscaled climate ensemble

Ahmadalipour

Moradkhani

Svoboda

2016

Drought is a natural hazard developing slowly and affecting large areas which may have severe consequences on society and economy. Due to the effects of climate change, drought is expected to exacerbate in various regions in future. In this study, the impact of climate change on drought characteristics is assessed, and statistical methods are employed to analyse the significance of projections. This is the first study utilizing 21 recently available downscaled global climate models generated by NASA (NEX‐GDDP) to evaluate drought projections over various regions across the United States. Drought is investigated through a multi‐model dual‐index dual‐scenario approach to probabilistically analyse drought attributes while characterizing the uncertainty in future drought projections. Standardized Precipitation Index and Standardized Precipitation Evapotranspiration Index values at the seasonal scale (3 months) are used to project and analyse meteorological drought conditions from 1950 to 2099 at 0.25° spatial resolution. Two future concentration pathways of RCP4.5 and RCP8.5 are considered for this analysis. Accounting for the combined effects of precipitation and temperature variations reveals a considerable aggravation in severity and extent of future drought in the western United States and a tendency toward more frequent and intense summer droughts across the Contiguous United States.

“…However, SPI assumes a high variability of precipitation and a temporal stationary status for the other variables such as temperature, surface wind and PET, and hence, it does not define droughts/wetness based on water balance. SPI has been widely used to study moisture conditions in many basins and regions of the world, such as the Volta basin of West Africa (Oguntunde et al, 2006;Kasei et al, 2010), in South Africa (Araujo et al, 2014;Ujeneza and Abiodun, 2014); United States (Oladipio, 1985;Wu et al, 2007); Italy (Piccarreta et al, 2004;Abiodun et al, 2013b); China (Bordi et al, 2004;Du et al, 2012) and over Europe (Lloyd-Hughes and Saunders, 2002;Bordi et al, 2009;Vicente-Serrano et al, 2012). For example, Du et al (2012) applied SPI to analyse the dry and wet conditions in Hunan Province of China.…”

Section: Introductionmentioning

confidence: 99%

“…This index is currently being applied in different regions around the world (e.g. Vicente-Serrano et al, 2012;Abiodun et al, 2013aAbiodun et al, , 2013bAraujo et al, 2014;Meque and Abiodun, 2014;Ujeneza and Abiodun, 2014).…”

Section: Introductionmentioning

confidence: 99%

Analysis of long‐term dry and wet conditions over Nigeria

Oguntunde

Lischeid

Abiodun

et al. 2016

Self Cite

Information on trends and changes in moisture conditions over a region can help policymakers to develop strategies for water resources and disaster risk management. In this study, the spatiotemporal variation of moisture indices and their annual trends in Nigeria were investigated. Thornthwaite moisture index (MI), the standardized precipitation index (SPI) and the standardized precipitation‐evapotranspiration index (SPEI) were computed for 1951–2014 period. Mann–Kendall trend and Sen's slope tests were used to examine the existence of temporal and spatial changes in these indices. MI decreased with increasing latitude and values ranged from −86 in the extreme north to +62 in the eastern part of the Niger Delta. A total of 73.4% of the landscape is under conditions where water supply is generally below the evaporative demand and only 26.6% of the area falls within wet sub‐humid and humid regimes. Significant downward trends were observed for all the moisture indices in most of the zones. In general, negative trends were observed in 98.2% of the landscape for MI, 96.7% for SPI and 98.2% for SPEI, showing drying tendencies over Nigeria. Between 40 and 50% of the land area is manifesting persistent shift towards aridity. Observed trends in MI is strongly correlated with that of SPI (r = 0.805) and SPEI (r = 0.715) and correlation of 0.886 was found between changes in SPI and SPEI. Rainfall generally showed higher and significant correlations with MI and slopes of all moisture indices. This information could help policymakers to develop appropriate coping and mitigation strategies for the most vulnerable areas.