Mechanisms of Summertime Subtropical Southern Indian Ocean Sea Surface Temperature Variability: On the Importance of Humidity Anomalies and the Meridional Advection of Water Vapor*

Chiodi, A. M.; Harrison, D. E.

doi:10.1175/jcli4271.1

Cited by 24 publications

(22 citation statements)

References 31 publications

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“…In the subtropical SWIO (208-108S, 508-708E), the air-sea temperature difference and relative humidity effects are positive during July(0)-January(1), especially during October(0)-December(0) when the wind effect begins to decrease (Fig. 12b), a result consistent with Chiodi and Harrison (2007). It is somewhat puzzling that both cases take place in the developing/mature phase of El Niñ o when the tropospheric warming is not yet fully developed over the TIO.…”

Section: A Possible Air Temperature and Relative Humidity Effectssupporting

confidence: 78%

“…The off-equatorial SIO is an exception, where ocean dynamics and cloud-radiative forcing are important. In the subtropical SIO, an anticyclone develops in the east during the mature phase of El Niñ o, and the associated anomalous westerlies weaken the prevailing southeast trades, giving rise to a strong warming that spans from October(0) to May(1) (Behera and Yamagata 2001;Xie et al 2002;Chiodi and Harrison 2007). Forced by observed SST over the tropical eastern Pacific, an atmospheric GCM coupled with a slab mixed layer model over the TIO captures this warming in the subtropical but not the tropical SIO (Alexander et al 2002;Lau and Nath 2003).…”

Section: Regional Characteristics Of the Warmingmentioning

confidence: 99%

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Role of Air–Sea Interaction in the Long Persistence of El Niño–Induced North Indian Ocean Warming*

et al. 2009

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El Niñ o induces a basin-wide increase in tropical Indian Ocean (TIO) sea surface temperature (SST) with a lag of one season. The north IO (NIO), in particular, displays a peculiar double-peak warming with the second peak larger in magnitude and persisting well through the summer. Motivated by recent studies suggesting the importance of the TIO warming for the Northwest Pacific and East Asian summer monsoons, the present study investigates the mechanisms for the second peak of the NIO warming using observations and general circulation models. This analysis reveals that internal air-sea interaction within the TIO is key to sustaining the TIO warming through summer. During El Niñ o, anticyclonic wind curl anomalies force a downwelling Rossby wave in the south TIO through Walker circulation adjustments, causing a sustained SST warming in the tropical southwest IO (SWIO) where the mean thermocline is shallow. During the spring and early summer following El Niñ o, this SWIO warming sustains an antisymmetric pattern of atmospheric anomalies with northeasterly (northwesterly) wind anomalies north (south) of the equator. Over the NIO as the mean winds turn into southwesterly in May, the northeasterly anomalies force the second SST peak that persists through summer by reducing the wind speed and surface evaporation. Atmospheric general circulation model experiments show that the antisymmetric atmospheric pattern is a response to the TIO warming, suggestive of their mutual interaction. Thus, ocean dynamics and Rossby waves in particular are important for the warming not only locally in SWIO but also on the basin-scale north of the equator, a result with important implications for climate predictability and prediction.

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Section: A Possible Air Temperature and Relative Humidity Effectssupporting

confidence: 78%

Section: Regional Characteristics Of the Warmingmentioning

confidence: 99%

Role of Air–Sea Interaction in the Long Persistence of El Niño–Induced North Indian Ocean Warming*

et al. 2009

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“…It has been used in many studies of midocean SST variability, including the recent study of the tropical and subtropical Indian Ocean (Chiodi andHarrison 2006, 2007). This is a now-classic model that predicts deepening of the mixed layer when the water FIG.…”

Section: Model and Datamentioning

confidence: 99%

“…This water type is appropriate for relatively clear tropical and subtropical waters. A small (2 ϫ 10 Ϫ5 m 2 s Ϫ1 ) background diffusion was applied uniformly to the water column to simulate the effects of unresolved processes, such as internal wave breaking [as was done in Chiodi andHarrison (2006, 2007)]. …”

Section: Model and Datamentioning

confidence: 99%

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Hurricane Alley SST Variability in 2005 and 2006*

Chiodi

Harrison

2008

Journal of Climate

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The North Atlantic hurricane seasons of 2005 and 2006 were dramatically different for the Gulf Coast and eastern seaboard of the United States. The 2005 hurricane season was one of the most destructive seasons in history, whereas there was limited impact in 2006. Hurricane activity had been forecast to be above normal in 2006, but it was not. One of the conspicuous differences in environmental conditions between these two years was sea surface temperature anomaly (SSTA) over a region of the western Atlantic and Caribbean (15°-30°N, 70°-40°W), which is important for hurricane formation and intensification. SSTA was more than 1.5 standard deviations warmer during the 2005 hurricane season, but it was much less in 2006 through most of its hurricane season. The intent of this study is to determine the mechanisms responsible for this SSTA difference. It is shown that the difference can be reproduced using a simple one-dimensional (1D) ocean mixed layer model forced with surface fluxes from the NCEP-NCAR reanalysis project. It is found that there are two causes of SSTA difference over this region during July through September: the first is latent heat flux variability caused by wind speed effects, and the second is nonlinear ocean warming caused by submonthly atmospheric variability. The observed SSTA difference is reproduced by our model even though solar forcing damps the observed difference, contrary to previous hypotheses.

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The influences of ENSO and the subtropical Indian Ocean Dipole on tropical cyclone trajectories in the southwestern Indian Ocean

Ash

Matyas

2010

Intl Journal of Climatology

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El Niño-Southern Oscillation (ENSO) is known to associate with variability of tropical cyclone (TC) trajectories in the southwestern Indian Ocean. However, consideration of ENSO phase alone does not account for all variability of TC tracks within this region. This study demonstrates that the subtropical Indian Ocean Dipole (SIOD) sea-surface temperature anomaly pattern is also significantly associated with variability in southwestern Indian Ocean TC tracks. Hierarchical cluster analysis is employed to group TC trajectories by their initial and final positions. Median monthly values of the Niño-3.4 index and Subtropical Dipole Index corresponding to the life cycles of TCs in each group are compared using non-parametric analysis of variance. The results suggest that both ENSO and SIOD are significantly associated with different types of southwestern Indian Ocean TC trajectories. Furthermore, significant interactions of ENSO and SIOD phases are found to influence certain types of TC tracks using contingency table tests. During simultaneous warm ENSO and negative SIOD phases, TCs moving across the southwestern Indian Ocean tend to follow more southward or southeastward tracks. During neutral or cool ENSO and positive SIOD phases, TCs moving through the southwestern Indian Ocean tend toward more westward trajectories. These findings suggest that use of an SIOD index in addition to an ENSO index could improve intraseasonal to seasonal statistical prediction of southwestern Indian basin TC activity.

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Mechanisms of Summertime Subtropical Southern Indian Ocean Sea Surface Temperature Variability: On the Importance of Humidity Anomalies and the Meridional Advection of Water Vapor*

Cited by 24 publications

References 31 publications

Role of Air–Sea Interaction in the Long Persistence of El Niño–Induced North Indian Ocean Warming*

Role of Air–Sea Interaction in the Long Persistence of El Niño–Induced North Indian Ocean Warming*

Hurricane Alley SST Variability in 2005 and 2006*

The influences of ENSO and the subtropical Indian Ocean Dipole on tropical cyclone trajectories in the southwestern Indian Ocean

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