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Seasonal Predictions (seasonal + prediction)

Distribution by Scientific Domains

Earth and Environmental Science	85%

Selected Abstracts

Seasonal prediction of European spring precipitation from El Niño,Southern Oscillation and Local sea-surface temperatures

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2002
Benjamin Lloyd-Hughes
Abstract The extent to which European seasonal precipitation is predictable is a topic of scientific and societal importance. Although the potential for seasonal prediction is much less over Europe than in the tropics, it is not negligible. Previous studies suggest that European seasonal precipitation skill may peak in the spring (March,April,May) period, this being the season when El Niño,Southern Oscillation (ENSO) teleconnections to the North Atlantic and European sector are at their strongest. Examination of the correlation significance and temporal stability of contemporaneous and lagged ENSO links to European and North African precipitation over 98 years confirms this to be the case. The strongest ENSO links are found across the central European region (45°N,55°N,35°E,5°W). These links are symmetric with the sign of ENSO. Using a linear statistical model employing temporally stable lagged ENSO and lagged local North Atlantic sea surface temperatures as predictors, we compute the forecast skill and significance of central European spring precipitation over 30 independent years. For early March forecasts our model skill is 14,18% better than climatology, which is significant at the 95% level. Copyright © 2002 Royal Meteorological Society [source]

The role of the basic state in the ENSO,monsoon relationship and implications for predictability

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 607 2005
A. G. Turner
Abstract The impact of systematic model errors on a coupled simulation of the Asian summer monsoon and its interannual variability is studied. Although the mean monsoon climate is reasonably well captured, systematic errors in the equatorial Pacific mean that the monsoon,ENSO teleconnection is rather poorly represented in the general-circulation model. A system of ocean-surface heat flux adjustments is implemented in the tropical Pacific and Indian Oceans in order to reduce the systematic biases. In this version of the general-circulation model, the monsoon,ENSO teleconnection is better simulated, particularly the lag,lead relationships in which weak monsoons precede the peak of El Niño. In part this is related to changes in the characteristics of El Niño, which has a more realistic evolution in its developing phase. A stronger ENSO amplitude in the new model version also feeds back to further strengthen the teleconnection. These results have important implications for the use of coupled models for seasonal prediction of systems such as the monsoon, and suggest that some form of flux correction may have significant benefits where model systematic error compromises important teleconnections and modes of interannual variability. Copyright © 2005 Royal Meteorological Society [source]

On the interannual wintertime rainfall variability in the Southern Andes

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2010
M. H. González
Abstract The paper concentrates on the analysis of the interannual variability of wintertime rainfall in the Southern Andes. Besides the socio-economic relevance of the region, mainly associated with hydroelectric energy production, the study of the climate variability in that area has not received as much attention as others along the Andes. The results show that winter rainfall explains the largest percentage of regional total annuals. A principal component analysis (PCA) of the winter rainfall anomalies showed that the regional year-to-year variability is mostly explained by three leading patterns. While one of them is significantly associated with both the El Niño Southern Oscillation (ENSO), and the Southern Annular Mode (SAM), the other two patterns are significantly related to interannual changes of the sea surface temperature (SST) anomalies in the tropical Indian Ocean. Specifically, changes in the ocean surface conditions at both tropical basins induce in the atmospheric circulation the generation of Rossby wave trains that extend along the South Pacific towards South America, and alter the circulation at the region under study. The relationship between variability in the Indian Ocean and the Andes climate variability has not been previously addressed. Therefore, this result makes a significant contribution to the identification of the sources of predictability in South America with relevant consequences for future applications in seasonal predictions. Copyright © 2009 Royal Meteorological Society [source]

Identification of large scale climate patterns affecting snow variability in the eastern United States

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2008
Jennifer Morin
Abstract This study investigates dominant patterns of snow variability and their relationship to large-scale climate circulations over the eastern half of the United States. Two snowfall variables,total seasonal snowfall (TSF) and number of snow days (NSD),are examined. A principal components (PC) analysis is conducted on data from 124 snowfall stations. The leading mode of variability for both TSF and NSD is driven by the North Atlantic Oscillation (NAO). The secondary mode of variability for TSF is driven by the Pacific/North American pattern (PNA), while the secondary mode of variability for NSD is driven by a dipole pattern and is attributable to regional influences and noise. These patterns exhibit persistence, which provides prospects for seasonal predictions of snowfall variables. This research compliments and extends the work of Serreze et al(1998), who performed a PC analysis of geopotential heights during the winter season and correlated the spatial patterns of the leading modes of variability with seasonal snowfall values. Copyright © 2007 Royal Meteorological Society [source]

Thermal history regulates methylbutenol basal emission rate in Pinus ponderosa

PLANT CELL & ENVIRONMENT, Issue 7 2006
DENNIS W. GRAY
ABSTRACT Methylbutenol (MBO) is a 5-carbon alcohol that is emitted by many pines in western North America, which may have important impacts on the tropospheric chemistry of this region. In this study, we document seasonal changes in basal MBO emission rates and test several models predicting these changes based on thermal history. These models represent extensions of the ISO G93 model that add a correction factor Cbasal, allowing MBO basal emission rates to change as a function of thermal history. These models also allow the calculation of a new emission parameter Estandard30, which represents the inherent capacity of a plant to produce MBO, independent of current or past environmental conditions. Most single-component models exhibited large departures in early and late season, and predicted day-to-day changes in basal emission rate with temporal offsets of up to 3 d relative to measured basal emission rates. Adding a second variable describing thermal history at a longer time scale improved early and late season model performance while retaining the day-to-day performance of the parent single-component model. Out of the models tested, the Tamb,Tmax7 model exhibited the best combination of day-to-day and seasonal predictions of basal MBO emission rates. [source]

GIOTTO: A coupled atmosphere-ocean general-circulation model: The tropical Pacific

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 567 2000
Martin Fischer
Abstract A new coupled general-circulation model (GIOTTO) has been developed. The individual components are composed of the atmosphere model, ECHAM-4, and the ocean model, MOM (Modular Ocean Model)-1.2. The model domain is global, and no flux correction is applied. The coupling is active between 60°N and 60° S. Poleward of 60° the atmosphere is forced by the climatological sea surface temperature (SST), and the ocean is relaxed towards the climatological SST and sea surface salinity. Further, the sea-ice coverage is prescribed. The coupling interval is set to two hours to resolve the diurnal cycle. In this paper we describe the design of the model, and discuss results of a coupled 20-year integration. The representation of the mean state is realistic, although there is an overall cold SST bias of about one degree centigrade in the tropics, and a tendency to simulate a double Inter Tropical Convergence Zone. The annual cycle, as simulated in the equatorial Pacific, is too weak in the east Pacific and too strong in the warm-pool region. The phase, however, is well captured. The SST variability in the equatorial Pacific is underestimated by about 30%, and the anomalies are too confined to the equator. The main features of El Niño-Southern Oscillation (ENSO) dynamics, like propagation of heat-content anomalies, reflection of equatorial Kelvin and Rossby waves, and westerly wind bursts, however, are correctly represented by the model. A variability analysis based on empirical orthogonal functions indicates that the ENSO mechanisms are simulated correctly. The model also appears to be well balanced with a remarkably low SST drift (0.5 degC decade,1), and a realistic equatorial thermal structure. We are, therefore, confident that the model can be used for experimental seasonal predictions. [source]