On the Angola Low Interannual Variability and Its Role in Modulating ENSO Effects in Southern AfricaSource: Journal of Climate:;2019:;volume 032:;issue 015::page 4783DOI: 10.1175/JCLI-D-18-0745.1Publisher: American Meteorological Society
Abstract: AbstractThe Angola low is a summertime low pressure system that affects the convergence of low-level moisture fluxes into southern Africa. Interannual variations of the Angola low reduce the seasonal prediction skills for this region that arise from coupled atmosphere?ocean variability. Despite its importance, the interannual dynamics of the Angola low, and its relationship with El Niño?Southern Oscillation (ENSO) and other coupled modes of variability, are still poorly understood, mostly because of the scarcity of atmospheric data and short-term duration of atmospheric reanalyses in the region. To bypass this issue, we use a long-term (3500 year) run from a 50-km-resolution global coupled model capable of simulating the summertime southern African large-scale circulation and teleconnections. We find that the meridional displacement and strength of the Angola low are moderately modulated by local sea surface temperature anomalies, especially those in proximity of the southeastern African coast, and to a lesser extent by ENSO and the subtropical Indian Ocean dipole. Comparison of the coupled run with a 1000-yr run driven by climatological sea surface temperatures reveals that the interannual excursions of the Angola low are in both cases associated with geopotential height anomalies over the southern Atlantic and Indian Ocean related to extratropical atmospheric variability. Midlatitude atmospheric variability explains almost 60% of the variance of the Angola low variability in the uncoupled run, but only 20% in the coupled run. Therefore, while the Angola low appears to be intrinsically controlled by atmospheric extratropical variability, the interference of the atmospheric response forced by sea surface temperature anomalies weakens this influence.
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contributor author | Pascale, Salvatore | |
contributor author | Pohl, Benjamin | |
contributor author | Kapnick, Sarah B. | |
contributor author | Zhang, Honghai | |
date accessioned | 2019-10-05T06:43:08Z | |
date available | 2019-10-05T06:43:08Z | |
date copyright | 5/7/2019 12:00:00 AM | |
date issued | 2019 | |
identifier other | JCLI-D-18-0745.1.pdf | |
identifier uri | http://yetl.yabesh.ir/yetl1/handle/yetl/4263205 | |
description abstract | AbstractThe Angola low is a summertime low pressure system that affects the convergence of low-level moisture fluxes into southern Africa. Interannual variations of the Angola low reduce the seasonal prediction skills for this region that arise from coupled atmosphere?ocean variability. Despite its importance, the interannual dynamics of the Angola low, and its relationship with El Niño?Southern Oscillation (ENSO) and other coupled modes of variability, are still poorly understood, mostly because of the scarcity of atmospheric data and short-term duration of atmospheric reanalyses in the region. To bypass this issue, we use a long-term (3500 year) run from a 50-km-resolution global coupled model capable of simulating the summertime southern African large-scale circulation and teleconnections. We find that the meridional displacement and strength of the Angola low are moderately modulated by local sea surface temperature anomalies, especially those in proximity of the southeastern African coast, and to a lesser extent by ENSO and the subtropical Indian Ocean dipole. Comparison of the coupled run with a 1000-yr run driven by climatological sea surface temperatures reveals that the interannual excursions of the Angola low are in both cases associated with geopotential height anomalies over the southern Atlantic and Indian Ocean related to extratropical atmospheric variability. Midlatitude atmospheric variability explains almost 60% of the variance of the Angola low variability in the uncoupled run, but only 20% in the coupled run. Therefore, while the Angola low appears to be intrinsically controlled by atmospheric extratropical variability, the interference of the atmospheric response forced by sea surface temperature anomalies weakens this influence. | |
publisher | American Meteorological Society | |
title | On the Angola Low Interannual Variability and Its Role in Modulating ENSO Effects in Southern Africa | |
type | Journal Paper | |
journal volume | 32 | |
journal issue | 15 | |
journal title | Journal of Climate | |
identifier doi | 10.1175/JCLI-D-18-0745.1 | |
journal fristpage | 4783 | |
journal lastpage | 4803 | |
tree | Journal of Climate:;2019:;volume 032:;issue 015 | |
contenttype | Fulltext |