TITLE

Seasonal Predictability and Spatial Coherence of Rainfall Characteristics in the Tropical Setting of Senegal

AUTHOR(S)
Moron, Vincent; Robertson, Andrew W.; Ward, M. Neil
PUB. DATE
November 2006
SOURCE
Monthly Weather Review;Nov2006, Vol. 134 Issue 11, p3248
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
This study examines space–time characteristics of seasonal rainfall predictability in a tropical region by analyzing observed data and model simulations over Senegal. Predictability is analyzed in terms of the spatial coherence of observed interannual variability at the station scale, and within-ensemble coherence of general circulation model (GCM) simulations with observed sea surface temperatures (SSTs) prescribed. Seasonal mean rainfall anomalies are decomposed in terms of daily rainfall frequency and daily mean intensity. The observed spatial coherence is computed from a 13-station network of daily rainfall during the July–September season 1961–98 in terms of (i) interannual variability of a standardized anomaly index (i.e., the average of the normalized anomalies of each station), (ii) the external variance (i.e., the fraction of common variance among stations), and (iii) the number of spatiotemporal degrees of freedom. Spatial coherence of interannual anomalies across stations is found to be much stronger for seasonal rainfall amount and daily occurrence frequency, compared with daily mean intensity of rainfall. Combinatorial analysis of the station observations suggests that, for occurrence and seasonal amount, the empirical number of spatial degrees of freedom is largely insensitive to the number of stations considered, and is between 3 and 4 for Senegal. For daily mean intensity, by contrast, each station is found to convey almost independent information, and the number of degrees of freedom would be expected to increase for a denser network of stations. The GCM estimates of potential predictability and skill associated with the SST forcing are found to be remarkably consistent with those inferred from the observed spatial coherence: there is a moderate-to-strong skill at reproducing the interannual variations of seasonal amounts and rainfall occurrence, whereas the skill is weak for the mean intensity of rainfall. Over Senegal during July–September, it is concluded that (i) regional-scale seasonal amount and rainfall occurrence frequency are predictable from SSTs, (ii) daily mean intensity of rainfall is spatially incoherent and largely unpredictable at the regional scale, and (iii) point-score estimates of seasonal rainfall predictability and skill are subject to large sampling variability.
ACCESSION #
23580163

 

Related Articles

  • Changes in the interannual SST-forced signals on West African rainfall. AGCM intercomparison. Mohino, Elsa; Rodríguez-Fonseca, Belén; Losada, Teresa; Gervois, Sébastien; Janicot, Serge; Bader, Juergen; Ruti, Paolo; Chauvin, Fabrice // Climate Dynamics;Nov2011, Vol. 37 Issue 9/10, p1707 

    Rainfall over West Africa shows strong interannual variability related to changes in Sea Surface Temperature (SST). Nevertheless, this relationship seem to be non-stationary. A particular turning point is the decade of the 1970s, which witnessed a number of changes in the climatic system,...

  • How Well Do Atmospheric General Circulation Models Capture the Leading Modes of the Interannual Variability of the Asian–Australian Monsoon? Zhou, Tianjun; Wu, Bo; Wang, Bin // Journal of Climate;Mar2009, Vol. 22 Issue 5, p1159 

    The authors evaluate the performances of 11 AGCMs that participated in the Atmospheric Model Intercomparison Project II (AMIP II) and that were run in an AGCM-alone way forced by historical sea surface temperature covering the period 1979–99 and their multimodel ensemble (MME) simulation...

  • Reply to "Comments on 'An Investigation the Relationship Between Sub-Saharan Rainfall and Global Sea Surface Temperatures'.". Semazzi, F. H. M.; Mehta, V.; Sud, Y. C. // Atmosphere -- Ocean (Canadian Meteorological & Oceanographic Soc;Mar1988, Vol. 26 Issue 1, p601 

    The article presents the response of F. H. M. Semazzi to the comments and recommendations made by M. L. Khandekar to his article "An Investigation of the Relationship Between Sub-Saharan Rainfall and Global Sea Surface Temperatures." In response to the questions raised by Khandekar, Semazzi...

  • ON CLIMATIC FLUCTUATIONS AND ENVIRONMENTAL CHANGES OF THE INDO-GANGETIC PLAINS, INDIA. Singh, Nityanand; Sontakke, N.A. // Climatic Change;Feb2002, Vol. 52 Issue 3, p287 

    Discusses the climatic fluctuations of the Indo-Gangetic Plains region (IGPR) of India. Impacts of the regional and global environmental changes; Description of the rainfall data used; Analysis of the summer monsoon rainfall fluctuation at selected stations across the IGPR; Causes of a westward...

  • Dry Spell in Monsoon Country. O'Leary, Denyse // Alternatives Journal (AJ) - Canada's Environmental Voice;Spring2003, Vol. 29 Issue 2, p6 

    Reports on climatologists Anil K. Gupta, Jonathan Overpeck and David M. Anderson's findings about the effect of climate change on the yearly rains provided by the annual Asian monsoons. Links between temperatures in North Atlantic and monsoon precipitation in Asia; Reduction in rainfall;...

  • Anomalous Rainfall over Southwest Western Australia Forced by Indian Ocean Sea Surface Temperatures. Ummenhofer, Caroline C.; Sen Gupta, Alexander; Pook, Michael J.; England, Matthew H. // Journal of Climate;Oct2008, Vol. 21 Issue 19, p5113 

    The potential impact of Indian Ocean sea surface temperature (SST) anomalies in modulating midlatitude precipitation across southern and western regions of Australia is assessed in a series of atmospheric general circulation model (AGCM) simulations. Two sets of AGCM integrations forced with a...

  • Links between rainfall variability on intraseasonal and interannual scales over western Tanzania and regional circulation and SST patterns. Mapande, A. T.; Reason, C. J. C. // Meteorology & Atmospheric Physics;May2005, Vol. 89 Issue 1-4, p215 

    This study investigates the circulation anomalies associated with the intraseasonal evolution of wet and dry years over western Tanzania (29–37° E, 11.5–4.75° S) and how the onset and withdrawal of the rainy season as well as its wet spell characteristics are modified. It is...

  • Tree-ring reconstructed rainfall variability in Zimbabwe. Therrell, Matthew D.; Stahle, David W.; Ries, Lydia P.; Shugart, Herman H. // Climate Dynamics;Jul2006, Vol. 26 Issue 7/8, p677 

    We present the first tree-ring reconstruction of rainfall in tropical Africa using a 200-year regional chronology based on samples of Pterocarpus angolensis from Zimbabwe. The regional chronology is significantly correlated with summer rainfall (November–February) from 1901 to 1948, and...

  • Assessment of a climate model to reproduce rainfall variability and extremes over Southern Africa. Williams, C. J. R.; Kniveton, D. R.; Layberry, R. // Theoretical & Applied Climatology;2010, Vol. 99 Issue 1/2, p9 

    It is increasingly accepted that any possible climate change will not only have an influence on mean climate but may also significantly alter climatic variability. A change in the distribution and magnitude of extreme rainfall events (associated with changing variability), such as droughts or...

Share

Read the Article

Courtesy of NEW JERSEY STATE LIBRARY

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics