Assessing the Influence of the MJO on Strong Precipitation Events in Subtropical, Semi-Arid North-Central Chile (30°S)Source: Journal of Climate:;2012:;volume( 025 ):;issue: 020::page 7003DOI: 10.1175/JCLI-D-11-00679.1Publisher: American Meteorological Society
Abstract: nnual precipitation in subtropical, semiarid north-central Chile (30°S) during rainy years comprises a few (3?5) strong events in the fall and winter, which are presumably modulated by the Madden?Julian oscillation (MJO). Precipitation from 1979?2009 was recorded daily at three stations along the Elqui Valley. The relationship between the MJO and precipitation is investigated from two perspectives: 1) examining a MJO index (MJOI) based on the actual precipitation events and 2) examining the likelihood of precipitation based on a favorable MJOI. About 80% of the strong precipitation events at the coast in La Serena are related to an active MJO near the central equatorial Pacific. These events are often typified by broad, slow moving synoptic systems in phase with the MJO propagation. Blocking in the far southeast Pacific is associated with precipitation 75% of the time, while deep troughs make up the rest.A relationship between a MJOI and strong rainfall suggests that, though it could be used as a potential diagnostic, the number of cases where there is a favorable MJOI but no precipitation (i.e., false alarms) limits its utility. Additional criteria such as the Southern Oscillation (SO) and Antarctic Oscillation (AAO) phases were used to reject false alarms. Rejecting cases with positive values of the SO index reduced the number of false alarms from 70% to 58%, leaving about two false alarms for every correctly diagnosed event. The AAO index could not discriminate between false alarms and real cases. While a favorable MJOI increases the likelihood of precipitation in the Elqui Valley, false alarms remain problematic.
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contributor author | Juliá, Cristóbal | |
contributor author | Rahn, David A. | |
contributor author | Rutllant, José A. | |
date accessioned | 2017-06-09T17:05:41Z | |
date available | 2017-06-09T17:05:41Z | |
date copyright | 2012/10/01 | |
date issued | 2012 | |
identifier issn | 0894-8755 | |
identifier other | ams-79291.pdf | |
identifier uri | http://onlinelibrary.yabesh.ir/handle/yetl/4222054 | |
description abstract | nnual precipitation in subtropical, semiarid north-central Chile (30°S) during rainy years comprises a few (3?5) strong events in the fall and winter, which are presumably modulated by the Madden?Julian oscillation (MJO). Precipitation from 1979?2009 was recorded daily at three stations along the Elqui Valley. The relationship between the MJO and precipitation is investigated from two perspectives: 1) examining a MJO index (MJOI) based on the actual precipitation events and 2) examining the likelihood of precipitation based on a favorable MJOI. About 80% of the strong precipitation events at the coast in La Serena are related to an active MJO near the central equatorial Pacific. These events are often typified by broad, slow moving synoptic systems in phase with the MJO propagation. Blocking in the far southeast Pacific is associated with precipitation 75% of the time, while deep troughs make up the rest.A relationship between a MJOI and strong rainfall suggests that, though it could be used as a potential diagnostic, the number of cases where there is a favorable MJOI but no precipitation (i.e., false alarms) limits its utility. Additional criteria such as the Southern Oscillation (SO) and Antarctic Oscillation (AAO) phases were used to reject false alarms. Rejecting cases with positive values of the SO index reduced the number of false alarms from 70% to 58%, leaving about two false alarms for every correctly diagnosed event. The AAO index could not discriminate between false alarms and real cases. While a favorable MJOI increases the likelihood of precipitation in the Elqui Valley, false alarms remain problematic. | |
publisher | American Meteorological Society | |
title | Assessing the Influence of the MJO on Strong Precipitation Events in Subtropical, Semi-Arid North-Central Chile (30°S) | |
type | Journal Paper | |
journal volume | 25 | |
journal issue | 20 | |
journal title | Journal of Climate | |
identifier doi | 10.1175/JCLI-D-11-00679.1 | |
journal fristpage | 7003 | |
journal lastpage | 7013 | |
tree | Journal of Climate:;2012:;volume( 025 ):;issue: 020 | |
contenttype | Fulltext |