Mechanisms of Tropical Atlantic SST Influence on North American Precipitation Variability
The dynamical mechanisms associated with the impact of year-to-year variability in tropical North Atlantic (TNA) sea surface temperatures (SSTs) on North American precipitation, during the cold and warm halves of the hydrological year (October–September) are examined. Observations indicate that duri...
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ftcolumbiauniv:oai:academiccommons.columbia.edu:10.7916/D8K07DV4 2023-05-15T13:15:09+02:00 Mechanisms of Tropical Atlantic SST Influence on North American Precipitation Variability Kushnir, Yochanan Seager, Richard Ting, Mingfang Naik, Naomi H. Nakamura, Jennifer A. 2009 https://doi.org/10.7916/D8K07DV4 English eng https://doi.org/10.7916/D8K07DV4 Climatology Hydrology Precipitation variability Ocean temperature Articles 2009 ftcolumbiauniv https://doi.org/10.7916/D8K07DV4 2019-04-04T08:06:26Z The dynamical mechanisms associated with the impact of year-to-year variability in tropical North Atlantic (TNA) sea surface temperatures (SSTs) on North American precipitation, during the cold and warm halves of the hydrological year (October–September) are examined. Observations indicate that during both seasons warmer-than-normal TNA SSTs are associated with a reduction of precipitation over North America, mainly west of 90°W, and that the effect can be up to 30% of the year-to-year seasonal precipitation RMS variability. This finding confirms earlier studies with observations and models. During the cold season (October–March) the North American precipitation variability associated with TNA fluctuations is considerably weaker than its association with ENSO. During the warm season (April–September), however, the Atlantic influence, per one standard deviation of SST anomalies, is larger than that of ENSO. The observed association between TNA SST anomalies and global and North American precipitation and sea level pressure variability is compared with that found in the output of an atmospheric general circulation model (AGCM) forced with observed SST variability, both globally and in the tropical Atlantic alone. The similarity between model output and observations suggests that TNA SST variability is causal. The mechanisms of the “upstream” influence of the Atlantic on North American precipitation are seasonally dependent. In the warm season, warmer-than-normal TNA SSTs induce a local increase in atmospheric convection. This leads to a weakening of the North Atlantic subtropical anticyclone and a reduction in precipitation over the United States and northern Mexico, associated with the anomalous southward flow there. In the cold season, a response similar to the warm season over the subtropical Atlantic is identified, but there is also a concomitant suppression of convection over the equatorial Pacific, which leads to a weakening of the Aleutian low and subsidence over western North America, similar to the impact of La Niña although weaker in amplitude. The impact of TNA SST on tropical convection and the extratropical circulation is examined by a set of idealized experiments with a linear general circulation model forced with the tropical heating field derived from the full AGCM. Article in Journal/Newspaper aleutian low North Atlantic Columbia University: Academic Commons Pacific |
institution |
Open Polar |
collection |
Columbia University: Academic Commons |
op_collection_id |
ftcolumbiauniv |
language |
English |
topic |
Climatology Hydrology Precipitation variability Ocean temperature |
spellingShingle |
Climatology Hydrology Precipitation variability Ocean temperature Kushnir, Yochanan Seager, Richard Ting, Mingfang Naik, Naomi H. Nakamura, Jennifer A. Mechanisms of Tropical Atlantic SST Influence on North American Precipitation Variability |
topic_facet |
Climatology Hydrology Precipitation variability Ocean temperature |
description |
The dynamical mechanisms associated with the impact of year-to-year variability in tropical North Atlantic (TNA) sea surface temperatures (SSTs) on North American precipitation, during the cold and warm halves of the hydrological year (October–September) are examined. Observations indicate that during both seasons warmer-than-normal TNA SSTs are associated with a reduction of precipitation over North America, mainly west of 90°W, and that the effect can be up to 30% of the year-to-year seasonal precipitation RMS variability. This finding confirms earlier studies with observations and models. During the cold season (October–March) the North American precipitation variability associated with TNA fluctuations is considerably weaker than its association with ENSO. During the warm season (April–September), however, the Atlantic influence, per one standard deviation of SST anomalies, is larger than that of ENSO. The observed association between TNA SST anomalies and global and North American precipitation and sea level pressure variability is compared with that found in the output of an atmospheric general circulation model (AGCM) forced with observed SST variability, both globally and in the tropical Atlantic alone. The similarity between model output and observations suggests that TNA SST variability is causal. The mechanisms of the “upstream” influence of the Atlantic on North American precipitation are seasonally dependent. In the warm season, warmer-than-normal TNA SSTs induce a local increase in atmospheric convection. This leads to a weakening of the North Atlantic subtropical anticyclone and a reduction in precipitation over the United States and northern Mexico, associated with the anomalous southward flow there. In the cold season, a response similar to the warm season over the subtropical Atlantic is identified, but there is also a concomitant suppression of convection over the equatorial Pacific, which leads to a weakening of the Aleutian low and subsidence over western North America, similar to the impact of La Niña although weaker in amplitude. The impact of TNA SST on tropical convection and the extratropical circulation is examined by a set of idealized experiments with a linear general circulation model forced with the tropical heating field derived from the full AGCM. |
format |
Article in Journal/Newspaper |
author |
Kushnir, Yochanan Seager, Richard Ting, Mingfang Naik, Naomi H. Nakamura, Jennifer A. |
author_facet |
Kushnir, Yochanan Seager, Richard Ting, Mingfang Naik, Naomi H. Nakamura, Jennifer A. |
author_sort |
Kushnir, Yochanan |
title |
Mechanisms of Tropical Atlantic SST Influence on North American Precipitation Variability |
title_short |
Mechanisms of Tropical Atlantic SST Influence on North American Precipitation Variability |
title_full |
Mechanisms of Tropical Atlantic SST Influence on North American Precipitation Variability |
title_fullStr |
Mechanisms of Tropical Atlantic SST Influence on North American Precipitation Variability |
title_full_unstemmed |
Mechanisms of Tropical Atlantic SST Influence on North American Precipitation Variability |
title_sort |
mechanisms of tropical atlantic sst influence on north american precipitation variability |
publishDate |
2009 |
url |
https://doi.org/10.7916/D8K07DV4 |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
aleutian low North Atlantic |
genre_facet |
aleutian low North Atlantic |
op_relation |
https://doi.org/10.7916/D8K07DV4 |
op_doi |
https://doi.org/10.7916/D8K07DV4 |
_version_ |
1766267169481424896 |