Improved Drought Monitoring in the Greater Horn of Africa by Combining Meteorological and Remote Sensing Based Indicators

Drought is a complex and insidious natural hazard. It is hence difficult to detect in its early stages and to monitor its spatial evolution. Defining drought is already a challenge and can be done differently by meteorologists, hydrologists or socio-economists. In each one of these research areas, various indicators were already set up to depict the development of drought. However they are usually considering only one aspect of the phenomenon. The development of integrated indicators could help to detect faster/better the onset of drought, to monitor more efficiently its evolution in time and space, and therefore to better trigger timely and appropriate actions on the field. In this study, meteorological and remote sensing based drought indicators were compared over the Greater Horn of Africa in order to better understand: (i) how they depict historical drought events ; (ii) if they could be combined into an integrated drought indicator. The meteorological indicator selected for our study is the well known Standardized Precipitation Index, SPI. This statistical indicator is evaluating the lack or surplus of precipitation during a given period of time as a function of the long-term average precipitation and its distribution. Two remote sensing based indicators were tested: the Normalized Difference Water Index (NDWI) derived from SPOT-VEGETATION and the Global Vegetation Index (VGI) derived form MERIS. The first index is sensitive to change in leaf water content of vegetation canopies while the second is a proxy of the amount and vigour of vegetation. For both indexes, anomalies were estimated using available satellite archives. Cross-correlations between remote sensing based anomalies and SPI were analysed for five land covers (forest, shrubland, grassland, sparse grassland, cropland and bare soil) over different regions in the Greater Horn of Africa. The time window for the statistical analysis was set to the rainy season, as it is the most critical period for vegetation growth. Moreover the behaviour of those indicators was also investigated during major historical droughts reported in the Emergency Database (EM-DAT) of the Centre for Research on the Epidemiology of Disasters (CRED, Leuven Belgium). Results of both analyses will be discussed during the conference.JRC.DDG.H.7-Land management and natural hazard

Extreme weather and climate in Europe

This report describes the current scientific knowledge of extreme weather and climate events in Europe for the following variables: temperature, precipitation, hail, and drought (with the following types of drought: meteorological, hydrological and soil moisture). The content summarises key literature drawn from peer reviewed journals and other sources (business and government reports), and builds upon the synthesised results presented in international assessments such as IPCC reports. It describes the recorded observations and modelled projections for extreme events including definitions, frequency, trends, spatial and temporal distribution. The report also presents an overview of the indices used to characterise extreme events as well as their main uses, before going on to describe the datasets where they are recorded, and provides information on the strengths and weaknesses of the indices and the datasets. Extra consideration is given to indices that are relevant to socio-economic impacts resulting from climate change and relevant statistical techniques for analysing extreme events. Observed changes in global climate and extreme events provide the context to the changes in extreme events observed in Europe, which are described for much of the 20th century. Modelled projections of extreme events are also given, under different emissions scenarios and time horizons, including results from regional models covering the European domain, such as EURO-CORDEX. The report is written for climate scientists, climate researchers and experts who use climate information in a professional role. There are four case studies (Appendix 2) which provide an anatomy of different recent European extreme weather/climate events including meteorological impacts and synoptic context. Observed global temperature trends show the number of warm extremes has increased and number of cool extremes has decreased over the last 100 years, and the length and frequency of summer heat waves has increased during the last century. In Europe these trends are most pronounced in the last 40 years although regional variations exist. For Europe, 2014 was the warmest year on record, although it had fewer hot days than recent years. Under future climate change with continued warming, the number of heat waves is projected to increase, along with their duration and intensity. Under all emissions scenarios, summers like the hot summer experienced in 2003 will become commonplace by the 2040s. The global trend in precipitation is generally for wetter conditions over the 20th century although changes are less temporally and spatially coherent than those observed for temperature. The general trend in precipitation for Europe in the 20th century is of increases over northern Europe and decreases over southern Europe. Extreme precipitation is becoming more intense and more frequent in Europe, especially in central and eastern Europe in winter, often resulting in greater and more frequent flooding. Since 1950 winter wet spells increased in duration in northern Europe and reduced in southern Europe, while summer wet spells became shorter in northern and eastern Europe. An increasing proportion of total rainfall is observed to fall on heavy rainfall days. Extreme precipitation (including short intense convective or longer duration frontal types) demonstrates complex variability and lacks a robust spatial pattern. Climate models project that events currently considered extreme are expected to occur more frequently in the future. For example a 1-in-20 year annual maximum daily precipitation amount is likely to become a 1-in-5 to 1-in-15 year event by the end of the 21st century in many parts of Europe. There are few ground based hail observation networks, so satellite measurements and weather models are used to identify hail forming conditions. In Europe most extreme hail events occur in the summer over Central Europe and the Alps where convective energy is greatest. Intense hail events are linked to increases in convective energy in the atmosphere observed over the last 30 years. Hailstorm projection studies, although limited to France, northern Italy and Germany, show increases in the convective conditions that lead to hail and some areas show a rise in damage days although this is not statistically significant. Recent severe droughts include Italy (1997-2002), the Baltic countries 2005-2009, the European heatwave of summer 2003, and the widespread European drought of 2011. The 1950s were prone to long, intense, Europe-wide meteorological and hydrological droughts. In northern and eastern Europe the highest drought frequency and severity was from the early 1950s to the mid-1970s. Southern and Western Europe (especially the Mediterranean) show the highest drought frequency and severity since 1990. There has been a small but continuous increase of the European areas prone to drought from the 1980s to the early 2010s. Regional climate models project a decrease in summer precipitation until 2100 of 17%. Dry periods are expected to occur 3 times more often at the end of this century and to last longer by 1 to 3 days compared to the period of 1971-2000. There is significant uncertainty associated with future projections of drought, with climate variability being the dominant source of uncertainty in observed and projected soil moisture drough

Testing two different precipitation datasets to compute the standardized precipitation index over the Horn of Africa

Severe droughts are a frequent problem for the Horn of Africa. In this article we test the possibility to use the Standardised Precipitation Index (SPI) for monitoring the availability of lack of precipitation in this region. The SPI is a statistical indicator evaluating the lack or surplus of precipitation over different time scales, thus allowing to distinguishing time-related impacts of the moisture deficit. SPI is calculated as a function of the long-term average precipitation, using continuous, long-term series of historic accumulated monthly precipitation records. The SPI for a given rainfall amount is then given in units of standard deviation from the mean of an equivalent normally distributed probability distribution function. As a consequence, wetter and drier climates and periods can be represented and monitored in the same way. For this study, the 3, 6, 9 and 12 months SPI has been calculated for the period from 1985 to 2008 over the Horn of Africa using GPCC and ERA-40 data interpolated to a 0.25 degree grid. Both SPI datasets have been compared for selected time periods by means of root mean square error, correlation coefficient and contingency tables approach. First results demonstrate the feasibility of using SPI for drought monitoring at regional scales over Africa.JRC.H.7-Land management and natural hazard

Drought Monitoring over Africa using the Standardized Precipitation Index (SPI)

The Standardised Precipitation Index (SPI) is a statistical indicator evaluating the lack or surplus of precipitation over different time scales, allowing distinguishing time-related impacts of the moisture deficit, for example on agricultural production (soil moisture), surface hydrology (run-off), groundwater, and economy. SPI is calculated as a function of the long-term average precipitation, using continuous, long-term series of historic accumulated monthly precipitation records. Since rainfall is not normally distributed for aggregation periods of less than 12 months a gamma distribution is fitted to the frequency distribution. The SPI for a given rainfall amount is then given, in units of standard deviation, by the precipitation deviation from the mean of an equivalent normally distributed probability distribution function with a zero mean and a standard deviation of one. For this study, the 3, 6, 9 and 12 months SPI has been calculated for the period from 1985 to 2008 over the Horn of Africa using GPCC and ERA-40 data. Both SPI datasets have been compared for selected time periods by means of root mean square error and correlation coefficient approach demonstrating possibilities of SPI for drought monitoring at regional scales over Africa.JRC.DDG.H.7-Land management and natural hazard

Climate change adaptation in the agriculture sector in Europe

Key messages:Climate change has an impact on European agriculture in a number of ways. Climate change has already negatively affected the agriculture sector in Europe, and this will continue in the future. Future climate change might also have some positive effects on the sector due to longer growing seasons and more suitable crop conditions. However, the number of climate extreme events negatively affecting agriculture in Europe is projected to increase. A cascade of impacts from climate change outside Europe may affect the price, quantity and quality of products, and consequently trade patterns, which in turn may affect agricultural income in Europe. Although fodder and food security in the EU will probably not be an issue, the increase in food demand could exert pressure on food prices in the coming decades.The EU strategy on adaptation to climate change and the common agricultural policy have enabled adaptation actions in the agriculture sector. The new proposed common agricultural policy for 2021-2027 has adaptation as a clear objective, which could lead to EU Member States having to increase their financing of adaptation measures in the sector.The EU Member States have defined the agriculture sector as a priority in their national adaptation strategies or national adaptation plans. Measures at national or regional levels include awareness raising, practical measures to decrease the impacts and risks of extreme weather events, or risk-sharing strategies, and developing and implementing infrastructure for irrigation and flood protection.There are opportunities for implementing a wide variety of existing measures at farm level that aim to improve the management of soils and water, which can provide benefits for adaptation, mitigation, the environment and the economy. However, adaptation at the farm level, in many cases, does not take place because of a lack of, among other things, resources for investment, policy initiatives to adapt, institutional capacity and access to adaptation knowledge. <br/

Impacts of natural hazards in Europe

Climate change has caused noticeable effects on human health in Europe, mainly as a result of extreme events, an increase in climate-sensitive diseases, and a deterioration in environmental and social conditions. Heat waves were thedeadliest extreme weather event in the period 1991–2015 in Europe.Increase in the frequency and intensity of extreme weather- and climate-related events may lead to more disastrous impacts on ecosystems and their services. Management of ecosystems can help to avoid or significantly reduce these impacts.The total reported economic losses caused by extreme weather- and climate-related events in the EEA member countries over the period 1980-2015 amount to around EUR 433 billion (in 2015 values). A large share of the total losses (70 %) has been caused by a small number of events (3 %)

4.4 Terrestrial ecosystems, soil and forests

Climate change is already affecting terrestrial ecosystems and biodiversity and is projected to become an even more important driver of biodiversity and ecosystem change in the future. Climate change will have a broad range of positive and negative impacts on biodiversity at genetic, species (e.g. plant and animal species) and ecosystem levels, including shifts in the distribution of species and ecosystems, changes in species abundance, changes in species phenology (i.e. timing of annual events) and an increased risk of extinctions for some species. This chapter describes the main projected impacts of climate change on terrestrial ecosystems, soil and forests.JRC.D.1-Bio-econom

Weather- and climate-related natural hazards in Europe

Since 2003, Europe has experienced several extreme summer heat waves. Such heat waves are projected to occur as often as every 2 years in the second half of the 21st century, under a high emissions scenario (RCP8.5). The impacts will beparticularly strong in southern Europe.Heavy precipitation events have increased in northern and north-eastern Europe since the 1960s, whereas different indices show diverging trends for south-western and southern Europe. Heavy precipitation events are projected tobecome more frequent in most parts of Europe.The number of very severe flood events in Europe has varied since 1980, but the economic losses have increased. It isnot currently possible to quantify the contribution due to increased heavy precipitation in parts of Europe compared with better reporting and land use changes.Observations of windstorm location, frequency and intensity have showed considerable variability across Europe during the 20th century. Models project an eastward extension of the North Atlantic storm track towards central Europe, with an increase in the number of cyclones in central Europe and a decreased number in the Norwegian and Mediterranean Seas.For medicanes (also termed Mediterranean Sea hurricanes), a decreased frequency but increased intensity of medicanes is projected in the Mediterranean area.Landslides are a natural hazard that cause fatalities and significant economic losses in various parts of Europe. Projected increases in temperature and changes in precipitation patterns will affect rock slope stability conditions and favour increases in the frequency of shallow landslides, especially in European mountains.The severity and frequency of droughts appear to have increased in parts of Europe, in particular in southern and south-eastern Europe. Droughts are projected to increase in frequency, duration, and severity in most of Europe, with the strongest increase projected for southern Europe.Forest fire risk depends on many factors, including climatic conditions, vegetation, forest management practices and other socio-economic factors. The burnt area in the Mediterranean region increased from 1980 to 2000; it has decreased thereafter. Projected increases in heat waves together with an expansion of the fire-prone area will increase the duration of fire seasons across Europe, in particular in southern Europe.Observational data between 1970 and 2015 show that alpine avalanches cause on average 100 fatalities every winter in the Alps. Increased temperatures are expected to lead to decreases in alpine snow cover and duration, and in turnto decreased avalanche activity below about 1 500-2 000 m elevation in spring, but increased avalanche activity above 2 000 m elevation, especially in winter.Hail is responsible for significant damage to crops, vehicles, buildings and other infrastructure. Despite improvements in data availability, trends and projections of hail events are still subject to large uncertainties owing to a lack of directobservation and inadequate microphysical schemes in numerical weather prediction and climate models.Extreme high coastal water levels have increased at most locations along the European coastline. This increase appears to be predominantly due to increases in mean local sea level rather than to changes in storm activity. Projected changes in the frequency and intensity of storm surges are expected to cause significant ecological damage, economic loss and other societal problems along low-lying coastal areas in northern and western Europe, unless additional adaptation measures are implemented