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Zewdu T. Segele, Michael B. Richman, Lance M. Leslie, and Peter J. Lamb

; Charney and Shukla 1981 ; Xue and Shukla 1993 ; Clark and Arritt 1995 ; Clark et al. 2001 ). The surface boundary focus of the present Ethiopian study is SST. However, El Niño–Southern Oscillation (ENSO)-related “predictability barrier” in Northern Hemisphere spring (e.g., Goswami and Shukla 1991 ; Webster and Yang 1992 ; Webster et al. 1998 ) can pose a major challenge to providing seasonal rainfall forecasts two or more months in advance in the tropics ( Goddard et al. 2001 ; Korecha and

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Lisa Hannak, Peter Knippertz, Andreas H. Fink, Anke Kniffka, and Gregor Pante

short-term forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF), this study revealed positive biases in LLJ speed, negative biases in low-level cloud cover, and therefore a large overestimation of solar radiation during the day. The LLJ biases, which should also affect advection and turbulent mixing, are consistent with biases in the north–south pressure gradient due to the misrepresentation of convection in the Sahel ( Marsham et al. 2013 ). For the more recent CMIP5

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Gang Zhang, Kerry H. Cook, and Edward K. Vizy

-resolution simulations is attributed to the treatment of convection (explicit vs parameterized) and not directly to the resolution differences. With preliminary testing to select physical parameterizations that work well in the region, the regional Weather Research and Forecasting (WRF) Model ( Skamarock et al. 2008 ) accurately reproduces West African rainfall on seasonal to interannual time scales (e.g., Hagos and Cook 2007 ; Cook and Vizy 2012 ; Vizy et al. 2013 ; Crétat et al. 2014 ). Working on the synoptic

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Gang Zhang, Kerry H. Cook, and Edward K. Vizy

fields on 3-hourly intervals over West Africa. To reduce the uncertainty of using reanalysis data, other global reanalyses are also compared with MERRA, including the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR; Saha et al. 2010 ), the ECMWF interim reanalysis (ERA-Interim; Dee et al. 2011 ), and the ECMWF reanalysis from their operational forecasts for the AMMA observational campaign with AMMA radiosonde data assimilated (ECMWF-OPERA; Agustí

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M. Issa Lélé, Lance M. Leslie, and Peter J. Lamb

-Saharan drought did not appear in conjunction with unusually dry southerly surface air from the tropical Atlantic. Lamb (1983) also found that during the extremely dry year, the northward moisture flux across the Gulf of Guinea was shallow compared with the much deeper monsoon layer, during the less severe drought years. Cadet and Nnoli (1987) used one summer (1979) of the European Centre for Medium-Range Weather Forecasts (ECMWF) data to study the water vapor transport over Africa. They analyzed biweekly

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Elinor R. Martin and Chris Thorncroft

measure of low- and midlevel AEW activity and are obtained from four reanalysis products for 1979–2008: ERA-Interim (0.75°; Simmons et al. 2007 ), Climate Forecast System Reanalysis (CFSR; 0.5°; Saha et al. 2010 ), Japanese 55-year Reanalysis Project (JRA-55; 1.25°; Kobayashi et al. 2015 ), and NCEP–NCAR (2.5°; Kalnay et al. 1996 ). In addition, EKE at 850 hPa has been shown to be important for tropical cyclogenesis ( Gray 1968 ; Thorncroft and Hodges 2001 ; Hopsch et al. 2007 ). Rainfall data

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Irenea L. Corporal-Lodangco, Lance M. Leslie, and Peter J. Lamb

the winds exceed 32.78 m s −1 . The intensity classification established by the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) was adopted in this study. PAGASA is the World Meteorological Organization (WMO) designated agency for monitoring, forecasting, and archiving TCs that affect the Philippines. a. Domain and TC data source The study region encompasses latitudes 5°–25°N and longitudes 115°–135°E, shown in Fig. 1 as the black inset, and is referred to

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Kerry H. Cook and Edward K. Vizy

physical processes of the precipitation changes that are responsible for those reductions. 3. Model simulations and evaluation The National Oceanic and Atmospheric Administration (NOAA)/National Center for Atmospheric Research (NCAR) Weather Research and Forecasting (WRF; Skamarock et al. 2005 ) regional model, version 3.1.1, is used with 32 vertical levels, 90-km horizontal resolution, and a time step of 3 min. The top of the atmosphere is set at 20 hPa. Figure 2 shows the full model domain with

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