The Mesoamerican mid-summer drought: the impact of its definition on occurrences and recent changes

The mid-summer drought, veranillo or canícula, is a phenomenon experienced in many areas, including Mexico, Central America, and the Caribbean. It generally is experienced as reduced rainfall in July–August, in the middle of the typical rainy season (May–September). Many past studies have attempted to quantify changes in mid-summer drought characteristics during the recent past or for future climate projections. To do this, objective definitions of a mid-summer drought’s occurrence, strength and duration have been developed by many researchers. In this effort we adopt a recent set of definitions and examine the impact of varying these on the characterization of mid-summer droughts and the detected changes over the past four decades. We find the selection of a minimum intensity threshold has a dramatic effect on the results of both the area considered as experiencing a mid-summer drought and the changes detected in the recent historical record. The intensity chosen can affect both the magnitude and direction of changes reported in the recent observed record. Further, we find that the typical mid-summer drought pattern may not be occurring during the time it has historically; whether examining past or future changes or developing improved seasonal forecasts, the non-stationarity of its timing should be accommodated.

Prediction of Droughts in the Mongolian Plateau Based on the CMIP5 Model

Understanding the variations of future drought under climate warming can provide the basis for mitigation efforts. This study utilized the standardized precipitation evapotranspiration index (SPEI), empirical mode decomposition (EMD) and empirical orthogonal function analysis (EOF) to predict the spatiotemporal variation of future drought under the representative concentration pathway RCP4.5 and RCP8.5 scenarios within the Mongolian Plateau over the period 2020–2100. The SPEI was computed using temperature and precipitation data generated by the fifth stage of the Coupled Model Intercomparison Project (CMIP5). The results under both the RCP4.5 and RCP8.5 scenarios showed increasing changes in temperature and precipitation. Both scenarios indicated increases in drought, with those under RCP8.5 much more extreme than that under RCP4.5. Under both scenarios, the climate showed an abrupt change to become drier, with the change occurring in 2041 and 2054 for the RCP4.5 and RCP8.5 scenarios, respectively. The results also indicated future drought to be more extreme in Mongolia than in Inner Mongolia. The simulated drought pattern showed an east–west antiphase and a north–south antiphase distribution based on EOF. The frequency of drought was higher under RCP8.5 compared to that under RCP4.5, with the highest frequencies under both scenarios occurring by the end of the 21st century, followed by the mid-21st century and early 21st century. The findings of this research can provide a solid foundation for the prevention, early warning and mitigation of drought disasters within the context of climate change in the Mongolian Plateau.

Using Co-Behavior Analysis to Interrogate the Performance of CMIP5 GCMs over Southern Africa

As established in earlier research, analysis of the combined roles (co-behavior) of multiple climate processes provides useful insights into the drivers of regional climate variability, especially for regions with no singular large-scale circulation control. Here, we extend the previous study in order to examine the performance of eight models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) in representing co-behavior influence on surface expressions over southern Africa. We find that although models broadly simulate observed precipitation responses over southern Africa, they fail to produce statistically strong response signals for an important drought pattern (El Niño co-behaving with positive Antarctic Oscillation during summer) for the region. We also demonstrate that the models show statistically strong temperature response signals to co-behavior that agree well with observed responses over the region. The multimodel ensemble mean although consistent with observations shows a larger spread. By elucidating the performance of models in representing observed co-behavior of climate processes, we are able to evaluate models while establishing important information for understanding of climate variability.

Spatial and temporal variation of drought patterns over East Africa

<p>Understanding historical patterns of changes in drought is essential for drought adaptation and mitigation.<br>While the negative impacts of drought over east Africa have attracted increasing attention,<br>a comprehensive and long-term spatiotemporal assessment of drought is still lacking. Here, we provided<br>a comprehensive spatiotemporal drought pattern analysis during the period of 1964–2015 over<br>the GHA. The Standardised Precipitation-Evapotranspiration Index (SPEI) at various timescales (1 month<br>(SPEI-01), 3 month (SPEI-03), 6 month (SPEI-06), and 12 month (SPEI-12)) was used to investigate drought<br>patterns on a monthly, seasonal, and interannual basis. The results showed that despite regional differences,<br>an overall increasing tendency of the drought was observed across the GHA over the past 52 yr, with trends of<br>change of -0.0017 yr<sup>-1</sup>, -0.0036 yr<sup>-1</sup>, -0.0031 yr<sup>-1</sup>, and -0.0023 yr<sup>-1</sup> for SPEI-01, SPEI-03, SPEI-06, and<br>SPEI-12, respectively. Droughts were more frequent, persistent, and intense in Sudan and Tanzania, while<br>more severe droughts were found in Somalia, Ethiopia, and Kenya. Droughts occurred frequently before<br>the 1990 s, and then became intermittent with large-scale impacts occurred during 1973–1974, 1984–<br>1985, and 2010–2011. A turning point was also detected in 1989, with the SPEI showing a statistically significant<br>downward trend during 1964–1989 and a non-statistically significant downward trend from 1990<br>to 2015. Seasonally, droughts exhibited an increasing trend in winter, spring, and summer, but a decreasing<br>trend in autumn. The research findings have significant implications for drought adaptation and mitigation<br>strategies through identifying the hotspot regions over east Africa at various timescales. Area-specific<br>efforts are required to alleviate environmental and societal vulnerabilities to drought events.</p>

Model Runtut waktu untuk Peramalan Indeks Kekeringan Daerah Lombok Utara

PDSI is the drought index method which has good accuracy to be applied in Lombok Island. However, this method is only able to hindcast the drought without any procedure to predict the drought index in the future. So, this model aims to recognize the characteristics of drought in North Lombok for early mitigation and anticipating drought disasters purposes in this region. The results obtained from this study are that the drought pattern in North Lombok has the SARIMA model of (0,1,2) (0,1,1)12. The drought in North Lombok mainly occurs between May-October with an increasing of drought index tends for over last 20 years.

Seasonal Drought Pattern Changes Due to Climate Variability: Case Study in Afghanistan

We assessed the changes in meteorological drought severity and drought return periods during cropping seasons in Afghanistan for the period of 1901 to 2010. The droughts in the country were analyzed using the standardized precipitation evapotranspiration index (SPEI). Global Precipitation Climatology Center rainfall and Climate Research Unit temperature data both at 0.5° resolutions were used for this purpose. Seasonal drought return periods were estimated using the values of the SPEI fitted with the best distribution function. Trends in climatic variables and SPEI were assessed using modified Mann–Kendal trend test, which has the ability to remove the influence of long-term persistence on trend significance. The study revealed increases in drought severity and frequency in Afghanistan over the study period. Temperature, which increased up to 0.14 °C/decade, was the major factor influencing the decreasing trend in the SPEI values in the northwest and southwest of the country during rice- and corn-growing seasons, whereas increasing temperature and decreasing rainfall were the cause of a decrease in SPEI during wheat-growing season. We concluded that temperature plays a more significant role in decreasing the SPEI values and, therefore, more severe droughts in the future are expected due to global warming.