The South Pacific Convergence Zone in three decades of satellite images

Haffke, C. M.; Magnúsdóttir, Guðrún

doi:10.1002/jgrd.50838

Cited by 37 publications

(44 citation statements)

References 28 publications

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“…Careful examination of the axis of maximum precipitation throughout the SPCZ in TRMM suggests an increased tilt of the subtropical SPCZ relative to the tropical SPCZ, consistent with the recent statistical work of Haffke and Magnusdottir (2013). In some coupled models (e.g., HadGEM2-CC) the change in tilt between the western and eastern SPCZ is drastic, but this bias is largely because the western, more tropical portion of the SPCZ is overly zonal.…”

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confidence: 80%

The Role of Tropical–Extratropical Interaction and Synoptic Variability in Maintaining the South Pacific Convergence Zone in CMIP5 Models

et al. 2015

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The South Pacific convergence zone (SPCZ) is simulated as too zonal a feature in the current generation of climate models, including those in phase 5 of the Coupled Model Intercomparison Project (CMIP5). This zonal bias induces errors in tropical convective heating, with subsequent effects on global circulation. The SPCZ structure, particularly in the subtropics, is governed by the tropical-extratropical interaction between transient synoptic systems and the mean background state. In this study, analysis of synoptic variability in the simulated subtropical SPCZ reveals that the basic mechanism of tropical-extratropical interaction is generally well simulated, with storms approaching the SPCZ along comparable trajectories to observations. However, there is a broad spread in mean precipitation and its variability across the CMIP5 ensemble. Intermodel spread appears to relate to a biased background state in which the synoptic waves propagate. In particular, the region of mean negative zonal stretching deformation or ''storm graveyard'' in the upper troposphere is displaced in CMIP5 models to the northeast of its position in reanalysis data, albeit with pronounced ('258) intermodel longitudinal spread. Precipitation along the eastern edge of the SPCZ shifts in accordance with a storm graveyard shift, and in general models with stronger storm graveyards show higher precipitation variability. Building on prior SPCZ research, it is suggested that SPCZs simulated by CMIP5 models are not simply too zonal; rather, in models the subtropical SPCZ manifests a diagonal tilt similar to observations while SST biases force an overly zonal tropical SPCZ, resulting in a more discontinuous SPCZ than observed.

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confidence: 80%

The Role of Tropical–Extratropical Interaction and Synoptic Variability in Maintaining the South Pacific Convergence Zone in CMIP5 Models

et al. 2015

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“…Here we will use the MJO phases described in Wheeler and Hendon [2004]. As in the analysis in Haffke and Magnusdottir [2013] only days with a strong MJO signal are considered so we require that the MJO index has an amplitude greater than 1. [2013] show how SPCZ activity (in terms of fraction of time present) changes during each phase of the MJO (see their Figure 8) by compositing SPCZ labels by MJO phase.…”

Section: 1002/2015jd023436mentioning

confidence: 99%

“…Recently, satellite observations have been used to greatly advance our knowledge of SPCZ behavior on a number of time scales. Our understanding of the interannual variability [Folland et al, 2002;Vincent et al, 2011;Haffke and Magnusdottir, 2013] and intraseasonal variability [Haffke and Magnusdottir, 2013] of the SPCZ has improved within the last decade. Hypothesis on SPCZ formation and maintenance have also emerged [Takahashi and Battisti, 2007;Widlansky et al, 2011;Matthews, 2012].…”

Section: Introductionmentioning

confidence: 99%

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Diurnal cycle of the South Pacific Convergence Zone in 30 years of satellite images

Haffke

Magnúsdóttir

2015

JGR Atmospheres

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A data set of three-hourly South Pacific Convergence Zone (SPCZ) location and extent, from which IR temperature within the SPCZ may be obtained, for 1980-2012, November-April is used to examine the diurnal cycle of the SPCZ. Maximum SPCZ area occurs at 15:00-18:00 local standard time (LST). Two minima in mean IR temperature are evident, one at 13:00-16:00 LST, nearly coinciding with the maximum in area, and the second in the early morning hours at 05:00-07:00 LST, when area is at a minimum. The morning minimum in mean IR temperature is associated with a peak in deep convection while the afternoon minimum is associated with a peak in midlevel clouds. On average, the morning minimum in IR temperature dominates in the tropical regions of the SPCZ, while the afternoon IR temperature minimum dominates in the subtropical regions of the SPCZ. The relative strength of the two IR temperature minima is affected by the seasonal cycle, intraseasonal variability associated with active Madden Julian Oscillation events, and interannual variability due to the El Niño Southern Oscillation. The morning IR temperature minimum becomes more dominant when the SPCZ is more frequently present or when the SPCZ is shifted toward the equator. In terms of cloud height, midlevel clouds dominate at all times in all regions of the SPCZ and peak in abundance between 15:00-18:00 LST. Low-level clouds peak near midnight and then transition to high-level clouds, which peak between 03

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“…In the afternoon the ITCZ expands in area and there is a marked increase in midlevel clouds. The Markov random field (MRF) statistical model has recently been adapted to detecting the SPCZ (Haffke and Magnusdottir 2013) during the austral summer halfyear and a similar signature in diurnal cycle is observed for the tropical part of the SPCZ (Haffke and Magnusdottir 2015).…”

Section: Introductionmentioning

confidence: 99%

Daily States of the March–April East Pacific ITCZ in Three Decades of High-Resolution Satellite Data

et al. 2016

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Zonally elongated areas of cloudiness that make up the east Pacific intertropical convergence zone (ITCZ) can take on several configurations in instantaneous observations. A novel statistical model is used to automatically assess the daily state of the east Pacific ITCZ using infrared satellite images from 1980 to 2012. Four ITCZ states are defined based on ITCZ location relative to the equator: north (nITCZ) and south (sITCZ) of the equator, simultaneously north and south of the equator (dITCZ, for double ITCZ), and over the equator (eITCZ). A fifth ITCZ state is used to classify days when no zonally elongated area of cloudiness is present (aITCZ, for absent ITCZ). The ITCZ states can occur throughout the year (except for the eITCZ, which is not present during June–October), with the nITCZ state dominating in terms of frequency of occurrence. Interannual variability of the state distribution is large. The most striking variability in ITCZ states is observed in spring. During March–April, the dITCZ state occurs on average 34% of the time, second only to the nITCZ state (39%). Composites of observed infrared temperature and precipitation by ITCZ state reveal distinct spatial configurations of cloudiness and rainfall. Strong sea surface temperature anomalies are associated only with eITCZ and sITCZ and they correspond to El Niño and La Niña, respectively. However, all five ITCZ states are associated with distinct atmospheric circulation patterns. A connection is found between the ITCZ and the South Pacific convergence zone (SPCZ), such that activity in the SPCZ is enhanced when the ITCZ is absent in the east Pacific.

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The South Pacific Convergence Zone in three decades of satellite images

Cited by 37 publications

References 28 publications

The Role of Tropical–Extratropical Interaction and Synoptic Variability in Maintaining the South Pacific Convergence Zone in CMIP5 Models

The Role of Tropical–Extratropical Interaction and Synoptic Variability in Maintaining the South Pacific Convergence Zone in CMIP5 Models

Diurnal cycle of the South Pacific Convergence Zone in 30 years of satellite images

Daily States of the March–April East Pacific ITCZ in Three Decades of High-Resolution Satellite Data

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