scholarly journals Changes in the African monsoon region at medium-term time horizon using 12 AR4 coupled models under the A1b emissions scenario

2011 ◽  
Vol 12 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Bernard Fontaine ◽  
Pascal Roucou ◽  
Paul-Arthur Monerie
Keyword(s):  
Time Horizon ◽  
Monsoon Region ◽  
Medium Term ◽  
Coupled Models ◽  
African Monsoon ◽  
Emissions Scenario

scholarly journals The Capability of ENSEMBLES Models in Predicting the Principal Modes of Pan-Asian Monsoon Precipitation

2015 ◽  
Vol 28 (21) ◽  
pp. 8486-8510 ◽  
Author(s):  
Ya Gao ◽  
Huijun Wang ◽  
Dong Chen
Keyword(s):  
Asian Monsoon ◽  
Southern Oscillation ◽  
Summer Precipitation ◽  
Tropical Indian Ocean ◽  
Spatiotemporal Distribution ◽  
Monsoon Region ◽  
Coupled Models ◽  
Asian Monsoon Region ◽  
Second Mode ◽  
Ensembles Project

Abstract The predictability of the dominant modes of summer (June–September) precipitation in the pan-Asian monsoon region is evaluated based on 1-month-lead retrospective forecasts in five state-of-the-art coupled models from the ENSEMBLES project for the period 1979–2005. The results show that the models and their multimodel ensemble mean (MME) perform well in reproducing the interannual variability of the climatology and the spatiotemporal distribution of the first mode of summer precipitation in the pan-Asian monsoon region. The associated oceanic and atmospheric circulation indicators are also well captured, such as the spatiotemporal structures of the simultaneous El Niño–Southern Oscillation (ENSO) and Antarctic Oscillation in the Pacific Ocean (AAOSP). Moreover, the interannual variation of the preceding AAOSP can also be captured by some of the coupled models. For individual models, the ECMWF, Météo-France, and Met Office models exhibit better skill with respect to the first mode of summer precipitation in the pan-Asian monsoon region, which displays a tripole pattern from north to south over 80°–140°E. In addition, these models can successfully predict the intensity and location of the associated ENSO, as well as the simultaneous summer AAOSP distributions. By contrast, the prediction capabilities of the Leibniz Institute of Marine Sciences (IFM-GEOMAR) and Euro-Mediterranean Center for Climate Change (CMCC-INGV) models are relatively weaker. Furthermore, the predictions of the second mode of the summer precipitation in the pan-Asian monsoon region are investigated. Some of the ENSEMBLES models show good capability in predicting the spatiotemporal distribution of the second mode, owing to the successful prediction of the atmospheric convection activities over the tropical Indian Ocean.

scholarly journals Characterization of Model Spread in PMIP2 Mid-Holocene Simulations of the African Monsoon

2013 ◽  
Vol 26 (4) ◽  
pp. 1192-1210 ◽  
Author(s):  
Weipeng Zheng ◽  
Pascale Braconnot
Keyword(s):  
Large Scale ◽  
West African Monsoon ◽  
Heat Fluxes ◽  
Coupled Models ◽  
African Monsoon ◽  
Systematic Biases ◽  
Intercomparison Project ◽  
Basic Features ◽  
Precipitation Changes

Abstract Simulations of the West African monsoon (WAM) for the present-day climate (0 ka) and the mid-Holocene (6 ka) using the coupled models from the Paleoclimate Modelling Intercomparison Project phase 2 (PMIP2) are assessed in this study. The authors first compare the ensemble simulations with modern observations and proxy estimates of past precipitation, showing that the PMIP2 model median captures the basic features of the WAM for 0 ka and the changes at 6 ka, despite systematic biases in the preindustrial (PI) simulations and underestimates of the northward extent and intensity of precipitation changes. The model spread is then discussed based on a classification of the monsoonal convective regimes for a subset of seven coupled models. Two major categories of model are defined based on their differences in simulating deep and moderate convective regimes in the PI simulations. Changes in precipitation at 6 ka are dominated by changes in the large-scale dynamics for most of the PMIP2 models and are characterized by a shift in the monsoonal circulation toward deeper convective regimes. Consequently, changes in the total precipitation at 6 ka depend on the changes in convective regimes and the characteristics of these regimes in the PI simulations. The results indicate that systematic model biases in simulating the radiation and heat fluxes could explain the damping of the meridional temperature gradient over West Africa and thereby the underestimation of precipitation in the Sahel–Sahara region.

Evaluating the Diurnal Cycle of Precipitation Representation in West African Monsoon Region with Different Convection Schemes

2016 ◽  
pp. 169-191
Author(s):  
Xiaogang He ◽  
Hyungjun Kim ◽  
Pierre-Emmanuel Kirstetter ◽  
Kei Yoshimura ◽  
Zhongwang Wei ◽  
...  
Keyword(s):  
Diurnal Cycle ◽  
West African Monsoon ◽  
West African ◽  
Monsoon Region ◽  
African Monsoon ◽  
Diurnal Cycle Of Precipitation ◽  
Convection Schemes

scholarly journals Mathematical model and supporting algorithm to aid the sequencing and scheduling of mining with loading equipment allocation

2014 ◽  
Vol 67 (4) ◽  
pp. 379-387
Author(s):  
Arthur Andrade ◽  
Miguel Santoro ◽  
Giorgio de Tomi
Keyword(s):  
Mathematical Model ◽  
Mixed Integer Linear Programming ◽  
Time Horizon ◽  
Open Pit ◽  
Mixed Integer ◽  
Open Pit Mining ◽  
Processing Plant ◽  
Medium Term ◽  
Sequencing And Scheduling ◽  
Plant Capacity

This paper focuses on the sequencing and scheduling problem of open pit mining, with the allocation of loading equipment considering a medium-term horizon. This study considers the existence of a heterogeneous loading equipment fleet and two types of mineable material, namely ore or waste rock. For the mining of ore, the following requirements are taken under consideration: the mixture quality, a crusher, the processing plant capacity and a stockpile, called ROM stockpile. In this context, we present a mathematical model in mixed integer linear programming, supported by an algorithm that is responsible for moving the time horizon at each model run, aiming to generate mining orders resolved with optimality. Together, these orders describe the loading equipment mining plan.

scholarly journals Estimation of Weather Noise in Coupled Ocean–Atmosphere Systems Using Initialized Simulations

2016 ◽  
Vol 29 (15) ◽  
pp. 5675-5688 ◽  
Author(s):  
Jieshun Zhu ◽  
Jagadish Shukla
Keyword(s):  
Asia Pacific ◽  
Boreal Summer ◽  
Monsoon Region ◽  
Noise Variance ◽  
Coupled Models ◽  
Previous Conclusion ◽  
Atmospheric Component ◽  
Weather Noise ◽  
Ocean Atmosphere ◽  
Ensemble Mean

Abstract This study presents a new method to estimate atmospheric weather noise from coupled models, which is based on initialized simulations with a CGCM. In this method, the weather noise is estimated by removing the signal part, as determined from the coupled ensemble mean simulations. The weather noise estimated from coupled models is compared with that estimated from uncoupled AGCM simulations. The model used in this study is CFSv2. The initialized simulations start from each April during 1982–2009 paired with four members and extend for 6 months. To make a clear comparison between weather noise in coupled and uncoupled simulations, a set of uncoupled AGCM (the atmospheric component of CFSv2) simulations are conducted, which are forced by the daily mean SSTs from the above initialized CGCM simulations. The comparison indicates that, over the Asia–Pacific monsoon region where the local air–sea coupling is important, the noise variances are generally reduced as a result of air–sea coupling, as are the total and signal variances. This result stands in contrast to the results of previous studies that suggested that the noise variance for coupled and uncoupled models is the same. It is shown that the previous conclusion is simply an artifact of the assumption applied in the AGCM-based approach (i.e., the signal is the same between coupled and uncoupled simulations). In addition, the variance difference also exhibits a clear seasonality, with a larger difference over the monsoon region appearing toward boreal summer. Another set of AGCM experiments forced by the same SST suggests that the CGCM-based method generally remains valid in estimating weather noise within 2 months of its initial start.

scholarly journals Influence of ENSO on the West African Monsoon: Temporal Aspects and Atmospheric Processes

2009 ◽  
Vol 22 (12) ◽  
pp. 3193-3210 ◽  
Author(s):  
Mathieu Joly ◽  
Aurore Voldoire
Keyword(s):  
Southern Oscillation ◽  
West African Monsoon ◽  
West African ◽  
Boreal Summer ◽  
Atmospheric Response ◽  
Coupled Models ◽  
The West ◽  
African Monsoon ◽  
Enso Events ◽  
Temporal Aspects

Abstract A significant part of the West African monsoon (WAM) interannual variability can be explained by the remote influence of El Niño–Southern Oscillation (ENSO). Whereas the WAM occurs in the boreal summer, ENSO events generally peak in late autumn. Statistics show that, in the observations, the WAM is influenced either during the developing phase of ENSO or during the decay of some long-lasting La Niña events. The timing of ENSO thus seems essential to the teleconnection process. Composite maps for the developing ENSO illustrate the large-scale mechanisms of the teleconnection. The most robust features are a modulation of the Walker circulation and a Kelvin wave response in the high troposphere. In the Centre National de Recherches Météorologiques Coupled Global Climate Model, version 3 (CNRM-CM3), the teleconnection occurs unrealistically at the end of ENSO events. An original sensitivity experiment is presented in which the ocean component is forced with a reanalyzed wind stress over the tropical Pacific. This allows for the reproduction of the observed ENSO chronology in the coupled simulation. In CNRM-CM3, the atmospheric response to ENSO is slower than in the reanalysis data, so the influence on the WAM is delayed by a year. The two principal features of the teleconnection are the timing of ENSO onsets and the time lag of the atmospheric response. Both are assessed separately in 16 twentieth-century simulations of the third phase of the Coupled Model Intercomparison Project (CMIP3). The temporal aspects of the ENSO teleconnection are reproduced with difficulty in state-of-the-art coupled models. Only four models simulate an impact of ENSO on the WAM during the developing phase.

scholarly journals The Present and Future of the West African Monsoon: A Process-Oriented Assessment of CMIP5 Simulations along the AMMA Transect

2013 ◽  
Vol 26 (17) ◽  
pp. 6471-6505 ◽  
Author(s):  
Romain Roehrig ◽  
Dominique Bouniol ◽  
Francoise Guichard ◽  
Frédéric Hourdin ◽  
Jean-Luc Redelsperger
Keyword(s):  
Decadal Variability ◽  
West African Monsoon ◽  
West African ◽  
Cmip5 Models ◽  
Climate Projections ◽  
Partial Recovery ◽  
Equatorial Atlantic ◽  
Coupled Models ◽  
The West ◽  
African Monsoon

Abstract The present assessment of the West African monsoon in the models of the Coupled Model Intercomparison Project (CMIP) phase 5 (CMIP5) indicates little evolution since the third phase of CMIP (CMIP3) in terms of both biases in present-day climate and climate projections. The outlook for precipitation in twenty-first-century coupled simulations exhibits opposite responses between the westernmost and eastern Sahel. The spread in the trend amplitude, however, remains large in both regions. Besides, although all models predict a spring and summer warming of the Sahel that is 10%–50% larger than the global warming, their temperature response ranges from 0 to 7 K. CMIP5 coupled models underestimate the monsoon decadal variability, but SST-imposed simulations succeed in capturing the recent partial recovery of monsoon rainfall. Coupled models still display major SST biases in the equatorial Atlantic, inducing a systematic southward shift of the monsoon. Because of these strong biases, the monsoon is further evaluated in SST-imposed simulations along the 10°W–10°E African Monsoon Multidisciplinary Analysis (AMMA) transect, across a range of time scales ranging from seasonal to intraseasonal and diurnal fluctuations. The comprehensive set of observational data now available allows an in-depth evaluation of the monsoon across those scales, especially through the use of high-frequency outputs provided by some CMIP5 models at selected sites along the AMMA transect. Most models capture many features of the African monsoon with varying degrees of accuracy. In particular, the simulation of the top-of-atmosphere and surface energy balances, in relation with the cloud cover, and the intermittence and diurnal cycle of precipitation demand further work to achieve a reasonable realism.

scholarly journals Ultra-low clouds over the southern West African monsoon region

2011 ◽  
Vol 38 (21) ◽  
pp. n/a-n/a ◽  
Author(s):  
Peter Knippertz ◽  
Andreas H. Fink ◽  
Robert Schuster ◽  
Jörg Trentmann ◽  
Jon M. Schrage ◽  
...  
Keyword(s):  
West African Monsoon ◽  
West African ◽  
Monsoon Region ◽  
African Monsoon ◽  
Low Clouds

scholarly journals An Examination of the Failure Rate and Content Equivalency of Electronic Surrogates and the Implications for Print Equivalent Preservation

2010 ◽  
Vol 5 (4) ◽  
pp. 7 ◽  
Author(s):  
Ken Ladd
Keyword(s):  
Social Sciences ◽  
Failure Rate ◽  
Time Horizon ◽  
Additional Data ◽  
Poor Quality ◽  
Electronic Journal ◽  
Medium Term ◽  
Science Technology ◽  
The University

Objective – This study sought to determine whether evidence indicates a need to preserve print equivalent journal collections. In addition, this research aimed to provide data on the failure rate of print equivalent materials for possible digitization to replace existing poor quality or defective electronic surrogates. Methods – The project compared the content of randomly selected journal titles, volumes, and issues from seven electronic journal archives and their print equivalents held at the University of Saskatchewan Library. The archives were obtained from five separate vendors representing humanities, social sciences, science, technology, and medicine. Data were collected on the frequency and types of failure of electronic surrogates, supplemental content missing from electronic surrogates, and frequency and types of failure of print equivalent materials. Results – Across all electronic journal archives the failure rate of electronic surrogates was 7.5% for all PDF documents and 11.5% for scholarly PDF documents. For individual electronic journal archives the failure rate ranged from 0.7% to 19.5% for all PDF documents and from 0.3% to 26.5% for scholarly PDF documents. Data is presented on the failure rate of individual electronic journal archives, types of failure, and missing supplemental content. An examination of print equivalent titles found 1.7% of print scholarly articles could not be used or were not optimal for digitization. Conclusions – The study demonstrates the need for preserving print equivalent journal titles for at least the short (less than 5 years) to medium term (up to 10 years), while poorly digitized materials are identified, replaced, and digitally preserved. While electronic surrogates of image-rich scholarly papers are more likely to have quality issues, the study found some text-only PDF scholarly documents were illegible, indicating the need for caution against liberally applying this as a criterion for disposal of print equivalent titles. There is significant supplemental content absent from electronic surrogates which indicates a need for further discussion of the necessity for such information or for incorporating it into the digitization process to ensure a complete record of the print equivalent journals for future use. The failure rate of print equivalent titles for possible digitization provides additional data for discussions related to the determination of optimal overlap. It also suggests that the number of copies required for a full set of preserved journals over a specified time horizon may be greater than anticipated, unless page level validation is performed.

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