Variability of the Caribbean low-level jet during boreal winter: large-scale forcings

Maldonado, Tito; Rutgersson, Anna; Amador, Jorge A.; Alfaro, Eric J.; Claremar, Björn

doi:10.1002/joc.4472

Cited by 21 publications

(22 citation statements)

References 34 publications

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“…6a). The subsequent reduction in Caribbean moisture transport is attributed to the response of the deceleration of the CLLJ under warm ENSO conditions in winter time (Amador et al, 2006;Amador, 2008;Maldonado et al, 2015). Stronger differences are detected as the first rainy season starts, with a greatly reduced contribution from the southwest Caribbean as shown by the dark blue shading in Fig.…”

Section: Response Of Oceanic Moisture Sources To Enso Forcingmentioning

confidence: 91%

Role of moisture transport for Central American precipitation

2017

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Abstract.A climatology of moisture sources linked with Central American precipitation was computed based upon Lagrangian trajectories for the analysis period 1980-2013. The response of the annual cycle of precipitation in terms of moisture supply from the sources was analysed. Regional precipitation patterns are mostly driven by moisture transport from the Caribbean Sea (CS). Moisture supply from the eastern tropical Pacific (ETPac) and northern South America (NSA) exhibits a strong seasonal pattern but weaker compared to CS. The regional distribution of rainfall is largely influenced by a local signal associated with surface fluxes during the first part of the rainy season, whereas large-scale dynamics forces rainfall during the second part of the rainy season. The Caribbean Low Level Jet (CLLJ) and the Chocó Jet (CJ) are the main conveyors of regional moisture, being key to define the seasonality of large-scale forced rainfall. Therefore, interannual variability of rainfall is highly dependent of the regional LLJs to the atmospheric variability modes. The El Niño-Southern Oscillation (ENSO) was found to be the dominant mode affecting moisture supply for Central American precipitation via the modulation of regional phenomena. Evaporative sources show opposite anomaly patterns during warm and cold ENSO phases, as a result of the strengthening and weakening, respectively, of the CLLJ during the summer months. Trends in both moisture supply and precipitation over the last three decades were computed, results suggest that precipitation trends are not homogeneous for Central America. Trends in moisture supply from the sources identified show a marked north-south seesaw, with an increasing supply from the CS Sea to northern Central America. Long-term trends in moisture supply are larger for the transition months (March and October). This might have important implications given that any changes in the conditions seen during the transition to the rainy season may induce stronger precipitation trends.

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Section: Response Of Oceanic Moisture Sources To Enso Forcingmentioning

confidence: 91%

Role of moisture transport for Central American precipitation

2017

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“…The wind data is used to calculate the CLLJ index as in Amador (2008) and Maldonado et al (2016). Based on the methodology developed in Alfaro (2014), and also applied by Solano (2015), the daily precipitation times series are filtered using a running triangular weight average with a window of 31 days, to avoid or minimise interruptions of the MSD due to weakening of the trades and/or approaching of the ITCZ, as suggested by Ramírez (1983) and Alfaro (2014).…”

Section: T Maldonado Et Al: Interannual Variability Of the Midsummementioning

confidence: 99%

“…This tripolar setting is located in the region where the PDO develops. The PDO has shown more influence in the southern USA and northern Mexico than in Central America (Muñoz et al, 2010;Maldonado et al, 2016), and that could be the reason that its influence is observed in the second mode. The Y loadings in both cases (Fig.…”

Section: Canonical Correlation Analysismentioning

confidence: 99%

“…This hypothesis, nevertheless, does not explain the almost simultaneous occurrence of the MSD in both southern Mexico and Central America (Magaña et al, 1999). On the other hand, Herrera et al (2015) describe the origins of the MSD studying the air-sea interaction between the CLLJ (Amador, 1998(Amador, , 2008Muñoz et al, 2008;Maldonado et al, 2016) and the ocean waters in the neighbourhood of the Pacific coast. Their findings show that the CLLJ peaks in July, provokes a cooling of the SSTs over the Pacific and a westward shift of low-level moisture convergence that combined with subsidence produce the MSD.…”

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confidence: 99%

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Interannual variability of the midsummer drought in Central America and the connection with sea surface temperatures

et al. 2016

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Abstract. The midsummer drought (MSD) in Central America is characterised in order to create annual indexes representing the timing of its phases (start, minimum and end), and other features relevant for MSD forecasting such as the intensity and the magnitude. The MSD intensity is defined as the minimum rainfall detected during the MSD, meanwhile the magnitude is the total precipitation divided by the total days between the start and end of the MSD. It is shown that the MSD extends along the Pacific coast, however, a similar MSD structure was detected also in two stations in the Caribbean side of Central America, located in Nicaragua. The MSD intensity and magnitude show a negative relationship with Niño 3.4 and a positive relationship with the Caribbean low-level jet (CLLJ) index, however for the Caribbean stations the results were not statistically significant, which is indicating that other processes might be modulating the precipitation during the MSD over the Caribbean coast. On the other hand, the temporal variables (start, minimum and end) show low and no significant correlations with the same indexes.The results from canonical correlation analysis (CCA) show good performance to study the MSD intensity and magnitude, however, for the temporal indexes the performance is not satisfactory due to the low skill to predict the MSD phases. Moreover, we find that CCA shows potential predictability of the MSD intensity and magnitude using sea surface temperatures (SST) with leading times of up to 3 months. Using CCA as diagnostic tool it is found that during June, an SST dipole pattern upon the neighbouring waters to Central America is the main variability mode controlling the inter-annual variability of the MSD features. However, there is also evidence that the regional waters are playing an important role in the annual modulation of the MSD features. The waters in the PDO vicinity might be also controlling the rainfall during the MSD, however, exerting an opposite effect at the north and south regions of Central America.

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“…Wind speeds around the 925 hPa level peak twice a year, during February and July. This low‐level wind current exhibits a semiannual cycle extensively reported in previous studies [ Amador , , Amador et al ., , ; Wang , ; Amador , ; Muñoz et al ., ; Whyte et al ., ; Cook and Vizy , ; Maldonado et al ., ]. In the literature this wind current is often known as the Caribbean low‐level jet (CLLJ).…”

Section: Introductionmentioning

confidence: 99%

The role of the meridional sea surface temperature gradient in controlling the Caribbean low‐level jet

et al. 2017

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The Caribbean low‐level jet (CLLJ) is an important modulator of regional climate, especially precipitation, in the Caribbean and Central America. Previous work has inferred, due to their semiannual cycle, an association between CLLJ strength and meridional sea surface temperature (SST) gradients in the Caribbean Sea, suggesting that the SST gradients may control the intensity and vertical shear of the CLLJ. In addition, both the horizontal and vertical structure of the jet have been related to topographic effects via interaction with the mountains in Northern South America (NSA), including funneling effects and changes in the meridional geopotential gradient. Here we test these hypotheses, using an atmospheric general circulation model to perform a set of sensitivity experiments to examine the impact of both SST gradients and topography on the CLLJ. In one sensitivity experiment, we remove the meridional SST gradient over the Caribbean Sea and in the other, we flatten the mountains over NSA. Our results show that the SST gradient and topography have little or no impact on the jet intensity, vertical, and horizontal wind shears, contrary to previous works. However, our findings do not discount a possible one‐way coupling between the SST and the wind over the Caribbean Sea through friction force. We also examined an alternative approach based on barotropic instability to understand the CLLJ intensity, vertical, and horizontal wind shears. Our results show that the current hypothesis about the CLLJ must be reviewed in order to fully understand the atmospheric dynamics governing the Caribbean region.

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Variability of the Caribbean low-level jet during boreal winter: large-scale forcings

Cited by 21 publications

References 34 publications

Role of moisture transport for Central American precipitation

Role of moisture transport for Central American precipitation

Interannual variability of the midsummer drought in Central America and the connection with sea surface temperatures

The role of the meridional sea surface temperature gradient in controlling the Caribbean low‐level jet

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