Search results for "ACASIS"
showing 5 items of 5 documents
Durée et fréquence des vagues de chaleur en Afrique tropicale septentrionale selon 5 indices de chaleur.
2019
Thermal extremes generate health risks that are increasingly taken into account, including in tropical Africa. This work compares the duration and the frequency of spring heat waves (HWs) in West Africa according to 5 indices: Warm Spell (WS), Heat Index (HI) with and without the relative humidity, Apparent Temperature (AT), and Excess Heat Factor (EHF). The daily relative humidity and temperature data (minimum, maximum, dew point are provided by the GSOD database for the period 1973-2014 and cover 145 stations spread over a large African area (3-24°N; 24°W-36°E). The results show that the duration of the HWs is short on the coast (3 days) and they last longer inland the continent and in th…
Durée et fréquence des vagues de chaleur en Afrique tropicale septentrionale selon 5 indices de chaleur
2019
Thermal extremes generate health risks that are increasingly taken into account, including in tropical Africa. This work compares the duration and the frequency of spring heat waves (HWs) in West Africa according to 5 indices: Warm Spell (WS), Heat Index (HI) with and without the relative humidity, Apparent Temperature (AT), and Excess Heat Factor (EHF). The daily relative humidity and temperature data (minimum, maximum, dew point are provided by the GSOD database for the period 1973-2014 and cover 145 stations spread over a large African area (3-24°N; 24°W-36°E). The results show that the duration of the HWs is short on the coast (3 days) and they last longer inland the continent and in th…
Les vagues de chaleur au Sahel : définition et principales caractéristiques spatio-temporelles (1973-2014).
2016
A definition of heat waves (HW) relevant for dry tropical regions is proposed and tested in the Sahel (i.e. duration,intensity and frequency). The Heat Index (HI derivative of Steadman’s (1979) formula) is calculated on dailydata of 145 West African stations from the GSOD database over the period 1973-2014. HWs recorded inSahelian and Sudanese climates mainly occur in boreal spring, i.e. April-May-June. They are more frequentsince 1998 (+ 8% very hot days, T90p) and they become longer (+1.2 days per decade) and more intense (from+0.3 to 0.4 ° C / decade respectively Sudanese and Sahelian climate) on the end of the period 1973-2014.
Uses and limits of thermal indices: the case of Sahel
2015
International audience; Our main goal here is to analyse extreme heat waves (HWs) in the Sahel (13°N-18°N; 16°W-30°E), using different thermal indices. In the ACASIS project funded bythe French “Agence Nationale de la Recherche”, HWs analyses are characterized forthe first time during the hottest season in the Sahel, using the Global Summary of theDay (GSOD) synoptic observations during April-May-June 1973-2013. Such extremehigh temperatures are usually defined by 3 criteria: 1/ Their low probability ofoccurrence: less than the 10% of the days. The use of absolute thresholds,associated with heat budget and physiological impacts, could be an alternative(Seneviratne et al., 2012). 2/ Their in…
Les vagues de chaleur au Sahel : caractérisation, mécanismes, prévisibilité.
2016
The mechanisms controlling Sahelian heat wave (HW) variability are examined on the period 1979-2014 using the GSOD observational database and ERA-Interim reanalyses. HW events are analyzed through all terms of the atmospheric energy balance, showing a predominant role of incoming shortwave radiation on daily maximum temperature (Tx) and atmospheric water vapor on minimum temperature (Tn). The low-frequency warming trend, not explained by the previous terms, is thought to relate to the increase of greenhouse gases concentrations, due to anthropogenic emissions. The predictability of Sahelian HW events is assessed for lead times reaching up to 15 days. The model's skill, biases and uncertaint…