scholarly journals Supplementary material to "Seasonal Forecasts of the Saharan Heat Low characteristics: A multi-model assessment"

2021 ◽  
Author(s):  
Cedric G. Ngoungue Langue ◽  
Christophe Lavaysse ◽  
Mathieu Vrac ◽  
Philippe Peyrille ◽  
Cyrille Flamant
Keyword(s):  
Model Assessment ◽  
Seasonal Forecasts ◽  
Supplementary Material ◽  
Heat Low

scholarly journals Seasonal forecasts of the Saharan heat low characteristics: a multi-model assessment

2021 ◽  
Vol 2 (3) ◽  
pp. 893-912
Author(s):  
Cedric G. Ngoungue Langue ◽  
Christophe Lavaysse ◽  
Mathieu Vrac ◽  
Philippe Peyrillé ◽  
Cyrille Flamant
Keyword(s):  
West African Monsoon ◽  
Seasonal Forecast ◽  
Lead Times ◽  
Model Assessment ◽  
Seasonal Forecasts ◽  
Weather Forecasts ◽  
Modes Of Variability ◽  
Forecast Models ◽  
Sahel Region ◽  
Heat Low

Abstract. The Saharan heat low (SHL) is a key component of the West African Monsoon system at the synoptic scale and a driver of summertime precipitation over the Sahel region. Therefore, accurate seasonal precipitation forecasts rely in part on a proper representation of the SHL characteristics in seasonal forecast models. This is investigated using the latest versions of two seasonal forecast systems namely the SEAS5 and MF7 systems from the European Center of Medium-Range Weather Forecasts (ECMWF) and Météo-France respectively. The SHL characteristics in the seasonal forecast models are assessed based on a comparison with the fifth ECMWF Reanalysis (ERA5) for the period 1993–2016. The analysis of the modes of variability shows that the seasonal forecast models have issues with the timing and the intensity of the SHL pulsations when compared to ERA5. SEAS5 and MF7 show a cool bias centered on the Sahara and a warm bias located in the eastern part of the Sahara respectively. Both models tend to underestimate the interannual variability in the SHL. Large discrepancies are found in the representation of extremes SHL events in the seasonal forecast models. These results are not linked to our choice of ERA5 as a reference, for we show robust coherence and high correlation between ERA5 and the Modern-Era Retrospective analysis for Research and Applications (MERRA). The use of statistical bias correction methods significantly reduces the bias in the seasonal forecast models and improves the yearly distribution of the SHL and the forecast scores. The results highlight the capacity of the models to represent the intraseasonal pulsations (the so-called east–west phases) of the SHL. We notice an overestimation of the occurrence of the SHL east phases in the models (SEAS5, MF7), while the SHL west phases are much better represented in MF7. In spite of an improvement in prediction score, the SHL-related forecast skills of the seasonal forecast models remain weak for specific variations for lead times beyond 1 month, requiring some adaptations. Moreover, the models show predictive skills at an intraseasonal timescale for shorter lead times.

scholarly journals Seasonal Forecasts of the Saharan Heat Low characteristics: A multi-model assessment

2021 ◽  
Author(s):  
Cedric G. Ngoungue Langue ◽  
Christophe Lavaysse ◽  
Mathieu Vrac ◽  
Philippe Peyrille ◽  
Cyrille Flamant
Keyword(s):  
Monsoon Season ◽  
West African Monsoon ◽  
Warming Trend ◽  
Seasonal Forecast ◽  
Model Assessment ◽  
Seasonal Forecasts ◽  
Modes Of Variability ◽  
Forecast Models ◽  
Sahel Region ◽  
Heat Low

Abstract. The Saharan Heat Low (SHL) is a key component of the West African monsoon system at synoptic scale and a driver of summertime precipitation over the Sahel region. Therefore, accurate seasonal precipitation forecasts rely in part on a proper representation of the SHL characteristics in seasonal forecasts models. This is investigated using the last versions of two seasonal forecast systems namely the SEAS5 and MF7 systems respectively from the European Center of Medium range Weather Forecasts (ECMWF) and Meteo-France. The SHL characteristics in the seasonal forecast models is assessed based on a comparison with the fifth ECMWF ReAnalysis (ERA5) for the period 1993–2016. The analysis of the modes of variability shows that the seasonal forecast models have issues with the timing of the SHL pulsations and the intensities when compared to ERA5. SEAS5 and MF7 show a cooling trend centered on the Sahara and a warming trend located in the eastern part of the Sahara, respectively. Both models tend to under-estimate the inter-annual variability of the SHL. We also show that the seasonal forecast models detect the eastward and westward shift of the SHL during the monsoon season. The use of statistical bias correction methods significantly reduces the bias in the seasonal forecast models and improves the forecast score. Despite an improvement of prediction score, the SHL-related forecast skills of SEAS5 and MF7 remain weak for a lead time beyond 1 month.

scholarly journals Supplementary material to "No Robust Evidence of Future Changes in Major Stratospheric Sudden Warmings: A Multi-model Assessment from CCMI"

2018 ◽  
Author(s):  
Blanca Ayarzagüena ◽  
Lorenzo M. Polvani ◽  
Ulrike Langematz ◽  
Hideharu Akiyoshi ◽  
Slimane Bekki ◽  
...  
Keyword(s):  
Model Assessment ◽  
Stratospheric Sudden Warmings ◽  
Supplementary Material ◽  
Robust Evidence

Therapeutic Effect of Metformin and Vitamin E Versus Prescriptive Diet in Obese Adolescents with Fatty Liver

2011 ◽  
Vol 81 (6) ◽  
pp. 398-406 ◽  
Author(s):  
Akcam ◽  
Boyaci ◽  
Pirgon ◽  
Kaya ◽  
Uysal ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Vitamin E ◽  
Fatty Liver ◽  
Liver Steatosis ◽  
Tnf Alpha ◽  
Dietary Advice ◽  
Model Assessment ◽  
Fasting Insulin ◽  
Alcoholic Fatty Liver ◽  
Obese Adolescents

Objective: The aim of the study was to determine whether metformin or vitamin E treatment for six months is effective in reducing body weight, blood pressure, and also ameliorating insulin resistance, adiponectin, and tumor necrosis factor (TNF)-alpha in obese adolescents with non-alcoholic fatty liver disease (NAFLD). Methods: Sixty-seven obese adolescents with liver steatosis (age range, 9 - 17 years) were included in the study. The metformin group received an 850-mg dose of metformin daily and the vitamin E group received 400 U vitamin E /daily, in capsule form for 6 months, plus an individually tailored diet, exercise, and behavioral therapy. Results: After 6 months later, there was a significant decline in body mass index, and fasting insulin and homeostatic model assessment (HOMA) values in all three groups. Moreover, in comparingson of changes in HOMA among the groups, the metformin- treated group showed significantly improved metabolic control and insulin sensitivity (HOMA) at the end of the study. There were no significant differences for changes of adiponectin, TNF-alpha, in all three groups after 6 months study. Conclusion: These data suggest that metformin treatment is more effective than dietary advice and vitamin E treatment in reducing insulin resistance, and also in ameliorating metabolic parameters such as fasting insulin and lipid levels, in obese adolescents having NAFLD.

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