Sahelian heat waves and their impacts warning – ACASIS

Dynamics of heat waves and their atmospheric structures will be characterised from statistical and diagnostic analyses of climate databases and atmospheric reanalyses over the last 40 years. Their evolution over the last decades will be analysed with the same approach as well as their predictability at short and medium ranges from multi-models ensembles forecasts, and as well as the longer term evolution with CMIP5/AR5 climate simulations.
Origins of radiative biases in climate models will be investigated using physical diagnostics and space-time high-resolution databases as the ones produced by the AMMA project (African Monsoon Multidisciplinary Analyses). Heat wave case studies will be selected to carry out specific sensitivity experiments with a hierarchy of models in order to go from the explicitly simulated process to its parametrisation in a climate model.
From the set-up of mortality and morbidity databases from the population survey sites in Senegal and Burkina, epidemiologic models will be developed to better understand the relationships between health and heat waves intensity, in order to produce adapted biometeorologilcal indicators and thresholds.
Associated interviews will be carried out on these sites to evaluate the physiological and social vulnerability of populations to heat waves. These data will be analysed with approaches specific to social sciences.
Finally a warning system will be held on an adapted platform with meteorological services of Senegal and Burkina, and specific recommendations will be done in case of such heat wave events occurrence in association with general directions of civil and health protection.

Heat wave variability is well explained by the additive role of two mechanisms : a continuous warming probably due to anthropogenic activities for the lower frequencies, El Niño Southern Oscillation (ENSO) for shorter timescales (interannual variability). The Sahelian seasonal temperature maximum follows a El Niño event in the Pacific, that let hope to provide seasonal forecasts.
We have estiated the radiative impact of clouds and aerosols by using in-situ data and a radiative transfer model. We have prepared and begun to analyse numerous pieces of information for springs 2014, 2015 and 2010.We have also carried out the first mesoscale simulations of this case study and begun to evaluate the radiative budget of climate simulations with various configurations.
Regarding epidemiologic studies,we can notice : The over-mortality signal linked to high temperatures is weak. It could be more visible among vulnerablepopulations as very young children and old persons. Old persons mortality is increasing along the XXIth century. Death seasonality has two peaks, one in the warm and dry season and the other one in the warm and wet season. Old person mortality is strongly linked to cardiovascular diseases. The models tested on mortality-temperature link show a stronger relationship with apparent temperature.
Weekly forecast bulletins and associated briefings have been produced during spring 2015.
Two workshops with scientists of the project and institutional decision makers have been organised in Senegal and Burkina.

Regarding databases, this will be achieved by the set-up of a web interface to get demographic and climate data, and by the creation of a collaborative platform. In-situ and satellite data, as simulations outputs, relevant for the project will be implemented on the AMMA database. Meteorological ANACIM and DGM data homogeneisation will be achieved.
We will carry out the analysis of heat wave predictability by a probabilistic approach (ensembles), of heat waves characteristics and their evolution in CMIP5 models.
Modelisation will take a larger part in the next works: case study simulations and results inter-comparison, impact of new physical parametrisations in climate simulations.
The analyses of heat wave and over-mortality will be achieved by setting up statistical models of the temperature-morbidity links. We will also investigate the morbidity seasonality over more arid regions by using consultation bulletins of the health districts. Interviews using questionnaires will be carried out to study population vulnerability and adaptation strategies to cope extreme temperatures.
The acasis.sedoo.fr site will become the core of the early warning system. It must be extended to include heat wave diagnostics and risk maps that will be evaluated as the most relevant for decision makers uses. Weekly meteorological bulletins production will start again during spring 2016 and we will associate more closely the Districts Chief-Doctors of Senegal and Burkina.

Presently this is no major scientific production. Several papers are being written and will be submitted before the end of the year 2015.

While the heat wave impacts on public health have been widely addressed in developed countries especially after the intense event over West Europe during summer 2003, no effort has been made to detect them and evaluate their impacts in least developed countries, and especially Africa where the climate is warmer and adaptation capacities are low. Over West Africa preliminary interviews, climate and epidemiologic analyses show however that this problem is emerging. Moreover climate projections in this area indicate that such events should increase in frequency and intensity in the near future. However these climate models display huge biases in their mean state over this region, and recent studies highlighted large radiative and low-level temperature biases. In order to provide robust information on the future evolution of heat waves, it is necessary to reduce as much as possible these biases.

Starting from this context, the main objective of ACASIS is to set-up a pre-operational heat wave warning system over West Africa tailored to health risks of the population living in this region. This is a demonstration project focused on Senegal and Burkina where national weather services have already started developing products dedicated to weather/climate and health relationships, and where several health and demographic observatories have been operating for up to several decades. Based on qualified meteorological, climate and demographic data bases, firstly, the dynamics of the heat wave events and their atmospheric patterns will be determined, as well as their evolution over the last decades. Their predictability at short and medium ranges will be evaluated on ensembles of multi-models forecasts outputs. On a longer time scale, control simulations and climate scenarios of the CMIP5/AR5 database will be analysed and the simulated future evolution and associated uncertainty of these events will be evaluated. More precisely the processes at the origin of model radiative biases will be examined and reduced as much as possible. In parallel, epidemiologic studies associated with interviews will be conducted in the health and demographic sites in Senegal and Burkina in order to evaluate the physiologic and social vulnerability of the African population to high temperature extremes. It will allow to define tailored bio-meteorological indicators to be used in the warning system. From these outcomes and by implementing downscaling to link the synoptic scale of the heat waves to local bio-meteorological indicators, we will set-up a demonstration warning system on a “testbed” platform named MISVA, already implemented as the result of a prior collaboration between Meteo-France, OMP and ANACIM, the meteorological agency of Senegal. Based on the interviews, and with the setting of several workshops with stakeholders and public institutions, we will be able to provide specific recommendations associated to these warnings. An implementation in the Meteo-France operational system at the end of the project or after might be possible.

To carry on this project, a pluri-disciplinary consortium has been set-up gathering climatologists, physical processes specialists, meteorologists, biostatisticians, demographers, socio-economists, epidemiologists, geographers, and operational meteorological agencies. It will work through a close collaboration between French and African teams where young African researchers will be highly involved.