A simple mechanism for the climatological midsummer drought along the Pacific coast of Central America

Karnauskas, Kristopher B.; Seager, Richard; Giannini, Alessandra; Busalacchi, Antonio J.

doi:10.1016/s0187-6236(13)71075-0

Cited by 57 publications

(87 citation statements)

References 39 publications

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“…Yet despite differences in timing and duration, the unique cool, moist core of the jet induced by the nocturnal monsoon forcing was readily distinguishable in the evolution of the 19 July jet. This signature as observed in both case studies is an extraordinary feature of TGJ in comparison to other notable gap winds such as the Central American Tehuantepec gap winds and Papagayo gap winds, which tend to be warm and dry (Magaña et al 1999;Sun and Yu 2006;Romero-Centeno et al 2007;Karnauskas et al 2013). This unique characteristic also features prominently in the impacts of the TGJ downwind.…”

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confidence: 53%

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The Tokar Gap Jet: Regional Circulation, Diurnal Variability, and Moisture Transport Based on Numerical Simulations

2015

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The structure, variability, and regional connectivity of the Tokar Gap jet (TGJ) are described using WRF Model analyses and supporting atmospheric datasets from the East African-Red Sea-Arabian Peninsula (EARSAP) region during summer 2008. Sources of the TGJ's unique quasi-diurnal nature and association with atypically high atmospheric moisture transport are traced back to larger-scale atmospheric dynamics influencing its forcing. These include seasonal shifts in the intertropical convergence zone (ITCZ), variability of the monsoon and North African wind regimes, and ties to other orographic flow patterns. Strong modulation of the TGJ by regional processes such as the desert heating cycle, wind convergence at the ITCZ surface front, and the local land-sea breeze cycle are described. Two case studies present the interplay of these influences in detail. The first of these was an ''extreme'' gap wind event on 12 July, in which horizontal velocities in the Tokar Gap exceeded 26 m s 21 and the flow from the jet extended the full width of the Red Sea basin. This event coincided with development of a large mesoscale convective complex (MCC) and precipitation at the entrance of the Tokar Gap as well as smaller gaps downstream along the Arabian Peninsula. More typical behavior of the TGJ during the 2008 summer is discussed using a second case study on 19 July. Downwind impact of the TGJ is evaluated using Lagrangian model trajectories and analysis of the lateral moisture fluxes (LMFs) during jet events. These results suggest means by which TGJ contributes to large LMFs and has potential bearing upon Sahelian rainfall and MCC development.

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supporting

confidence: 53%

“…As a result, a feedback loop between ocean and atmosphere is formed, resulting in a suppression and displacement of atmospheric deep convection and rainfall. Climate model simulations and satellite observations suggest that this may be an underlying mechanism for the midsummer drought of Central America (Karnauskas et al 2013;Romero-Centeno et al 2007). …”

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confidence: 99%

The Tokar Gap Jet: Regional Circulation, Diurnal Variability, and Moisture Transport Based on Numerical Simulations

2015

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“…Recent studies such as Karnauskas et al (2013) and Herrera et al (2015) have proposed different hypothesis about the origin of the MSD. Karnauskas et al (2013) argue that the MSD originates as a response to one single precipitation-enhancing mechanism occurring twice, contrary to a suppressing mechanism. The latitudinal dependence in the two peaks of precipitation surge as response to the biannual crossing of the solar declination, which leads to the two peaks in convective instability and hence rainfall.…”

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confidence: 99%

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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“…Furthermore, it also highlights the mid-summer drought phenomenon during the monsoon break (Asai and Fukui 1977;Ho and Wang 2002;Karnauskas et al 2013) in July. Both climatic phenomena cannot be clearly addressed by the SPI patterns.…”

Section: Climatologymentioning

confidence: 76%

Constructing a 1-km Gridded Multi-Scalar Drought Index Dataset (1960 - 2012) in Taiwan Based on the Standardized Precipitation Evapotranspiration Index-SPEI

Weng¹

2016

Terr. Atmos. Ocean. Sci.

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An index sensitive to global warming, the standardized precipitation evapotranspiration index (SPEI), is employed in this study to construct a 1-km gridded multi-scalar drought index data bank in Taiwan. A site-and scale-dependent posterior fitness assessment procedure regarding determination of the most appropriate statistical distribution is used to standardize the station's water deficit/surplus series, thereby SPEI at various time scales. Model uncertainty at different scales is evaluated and the results show that the uncertainty is higher for the shorter 10-day scale. Contrasts in the climatic means between SPEI and popular standardized precipitation index (SPI) are compared. The climatic pre-summer monsoon heating and midsummer drought phenomena are better captured by the SPEI. The established data bank, one of the data integration tasks in the Taiwan Climate Change Projection and Information Platform (TCCIP) project, is helpful in historical drought diagnostics. It also serves as the ground truth to correct model biases while using the regional model to project hydro-climate change and impact assessment, and historical baseline in the statistical downscaling while developing the statistical relationship between the general circulation model outputs and fine-scale observations. As an example of applications, the gridded SPEI at 3-month time scale is used to study the interannual variability in springtime drought. The results show that Taiwan's southwestern plains region is most vulnerable to the risk of droughts. Composite analysis reveals that possible causes of island-wide drought link to the turnabout of cold El Niño-Southern Oscillation (ENSO) phase but also to the interannual variability in Pacific Decadal Oscillation when the analysis is initiated from the regional perspective.

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A simple mechanism for the climatological midsummer drought along the Pacific coast of Central America

Cited by 57 publications

References 39 publications

The Tokar Gap Jet: Regional Circulation, Diurnal Variability, and Moisture Transport Based on Numerical Simulations

The Tokar Gap Jet: Regional Circulation, Diurnal Variability, and Moisture Transport Based on Numerical Simulations

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

Constructing a 1-km Gridded Multi-Scalar Drought Index Dataset (1960 - 2012) in Taiwan Based on the Standardized Precipitation Evapotranspiration Index-SPEI

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