Asian summer monsoon prediction in ECMWF System 4 and NCEP CFSv2 retrospective seasonal forecasts

Abstract

The seasonal prediction skill of the Asian summer monsoon is assessed using retrospective predictions ) from the ECMWF System 4 (SYS4) and NCEP CFS version 2 (CFSv2) seasonal prediction systems. In both SYS4 and CFSv2, a cold bias of sea-surface temperature (SST) is found over the equatorial Pacific, North Atlantic, Indian Oceans and over a broad region in the Southern Hemisphere relative to observations. In contrast, a warm bias is found over the northern part of North Pacific and North Atlantic. Excessive precipitation is found along the ITCZ, equatorial Atlantic, equatorial Indian Ocean and the maritime continent. The southwest monsoon flow and the Somali Jet are stronger in SYS4, while the southeasterly trade winds over the tropical Indian Ocean, the Somali Jet and the subtropical northwestern Pacific high are weaker in CFSv2 relative to the reanalysis. In both systems, the prediction of SST, precipitation and low-level zonal wind has greatest skill in the tropical belt, especially over the central and eastern Pacific where the influence of El Nino-Southern Oscillation (ENSO) is dominant. Both modeling systems capture the global monsoon and the large-scale monsoon wind variability well, while at the same time performing poorly in simulating monsoon precipitation. The Asian monsoon prediction skill increases with the ENSO amplitude, although the models simulate an overly strong impact of ENSO on the monsoon. Overall, the monsoon predictive skill is lower than the ENSO skill in both modeling systems but both systems show greater predictive skill compared to persistence.

Global Meteorological Drought: A Synthesis of Current Understanding with a Focus on SST Drivers of Precipitation Deficits

“…In contrast, the variability of East Asian monsoon circulation is well captured (Zhou et al 2009c;Song and Zhou 2014a). A successful reproduction of the interannual EASM pattern depends highly on the Indian Ocean-western Pacific anticyclone teleconnection (Kim et al 2012;Song and Zhou 2014a,b). Finally, Zhang and Zhou (2015) note that in climate change projections, most climate models simulate increasing drought frequency and intensity over East Asia, mainly in southeastern Asia, although the models differ regarding drought patterns and severity.…”

Seasonal streamflow forecasting in the upper Indus Basin of Pakistan: an assessment of methods

“…climate model) forecasts of precipitation and temperature are often not sufficiently skilful in this region. For example, Kim et al (2012) assessed retrospective seasonal forecasts of the Asian summer monsoon from ECMWF System 4 (Molteni et al, 2011) and NCEP CFSv2 (Saha et al, 2014), finding low skill for precipitation prediction and poor simulations of the Indian summer monsoon circulation. Cash et al (2017) assessed monthly North American Multi-Model Ensemble (Kirtman et al, 2013) hindcasts initialised on 1 May for May to November for South Asia, including the mountainous areas of Afghanistan and Pakistan.…”

Skill of ECMWF system‐4 ensemble seasonal climate forecasts for East Africa

“…Seasonal forecasts provide climate outlooks from a month to over a year ahead based on the interactions of the atmosphere with slowly varying climate system components like the oceans and land surface (Thomson et al, 2006;Kim et al, 2012b;Doblas-Reyes et al, 2013;Manzanas et al, 2014). A major source of seasonal predictability is the El-Niño Southern Oscillation (ENSO) because it forces climate anomalies globally (Harrison, 2005;van Oldenborgh et al, 2005;Hoskins, 2006;Palmer, 2006;Charles et al, 2012;Doblas-Reyes et al, 2013;Manzanas et al, 2014) and is predictable with 6-12 months lead-time.…”