Relation entre prévisions saisonnières de pluie du modèle ARPEGE et volume de crue du fleuve Niger

Le modèle ARPEGE.3 fournit fin juillet des prévisions saisonnières de pluie pour les mois de septembre et octobre sur 98 cellules de 300X300 km englobant l'Afrique de l'ouest. Ces prévisions sont soumises à une analyse en composantes principales sur 50 zones de forme, taille et position différentes. Sur chaque zone, des régressions multiples descendantes sont calculées sur la période 1979-1998 entre les huit premières composantes principales et le débit naturel de septembre-octobre du fleuve Niger à Koulikouro. Sur la majorité des zones, ces régressions sont significatives car leur coefficient de détermination a une probabilité faible d'être obtenu par hasard. Parmi les régressions à trois préviseurs, celle qui présente le meilleure calage (R²=0.577) permet de prévoir le débit à partir des prévisions pluviométriques d'une zone de 1200X1200 km centrée 1500 km au sud-est du bassin contrôlé par Koulikouro. Ce modèle à trois paramètres est validé assez correctement sur la période 1999-2006. (Résumé d'auteur

Global Impact of the COVID-19 Pandemic on Stroke Volumes and Cerebrovascular Events: One-Year Follow-up.

Declines in stroke admission, intravenous thrombolysis, and mechanical thrombectomy volumes were reported during the first wave of the COVID-19 pandemic. There is a paucity of data on the longer-term effect of the pandemic on stroke volumes over the course of a year and through the second wave of the pandemic. We sought to measure the impact of the COVID-19 pandemic on the volumes of stroke admissions, intracranial hemorrhage (ICH), intravenous thrombolysis (IVT), and mechanical thrombectomy over a one-year period at the onset of the pandemic (March 1, 2020, to February 28, 2021) compared with the immediately preceding year (March 1, 2019, to February 29, 2020). We conducted a longitudinal retrospective study across 6 continents, 56 countries, and 275 stroke centers. We collected volume data for COVID-19 admissions and 4 stroke metrics: ischemic stroke admissions, ICH admissions, intravenous thrombolysis treatments, and mechanical thrombectomy procedures. Diagnoses were identified by their ICD-10 codes or classifications in stroke databases. There were 148,895 stroke admissions in the one-year immediately before compared to 138,453 admissions during the one-year pandemic, representing a 7% decline (95% confidence interval [95% CI 7.1, 6.9]; p<0.0001). ICH volumes declined from 29,585 to 28,156 (4.8%, [5.1, 4.6]; p<0.0001) and IVT volume from 24,584 to 23,077 (6.1%, [6.4, 5.8]; p<0.0001). Larger declines were observed at high volume compared to low volume centers (all p<0.0001). There was no significant change in mechanical thrombectomy volumes (0.7%, [0.6,0.9]; p=0.49). Stroke was diagnosed in 1.3% [1.31,1.38] of 406,792 COVID-19 hospitalizations. SARS-CoV-2 infection was present in 2.9% ([2.82,2.97], 5,656/195,539) of all stroke hospitalizations. There was a global decline and shift to lower volume centers of stroke admission volumes, ICH volumes, and IVT volumes during the 1st year of the COVID-19 pandemic compared to the prior year. Mechanical thrombectomy volumes were preserved. These results suggest preservation in the stroke care of higher severity of disease through the first pandemic year. This study is registered under NCT04934020