Circulation, Moisture, and Precipitation Relationships along the South Pacific Convergence Zone in Reanalyses and CMIP5 Models

Niznik, Matthew J.; Lintner, Benjamin R.

doi:10.1175/jcli-d-13-00263.1

Cited by 15 publications

(13 citation statements)

References 37 publications

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“…Niznik and Lintner (2013) showed that synoptic time scale changes to low-level inflow east of the SPCZ in coupled GCMs are associated with spatial shifts in precipitation consistent with observations, albeit with considerable intermodel spread in the spatial distributions of these shifts. These results implicate potential connections between low-level inflow variability and the frequency with which synoptic disturbances interact with the SPCZ.…”

Section: Introductionsupporting

confidence: 72%

“…As a basis for comparison in the relatively data-sparse South Pacific, the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR; Saha et al 2010) is used in all analyses during the 32-yr period spanning 1979-2010 (variables examined in the CMIP5 models are also available for CFSR during this period). Niznik and Lintner (2013) showed that CFSR captures the climatological position of the SPCZ well (cf. Fig.…”

Section: Methodsmentioning

confidence: 99%

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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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Section: Introductionsupporting

confidence: 72%

Section: Methodsmentioning

confidence: 99%

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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“…Seasonality in surface convergence also contributed to the region of enhanced seasonal variability in the subtropical western south Pacific. The South Pacific Convergence Zone (SPCZ) lies within this region, and the orientation and intensity of the SPCZ vary on synoptic through to interannual timescales (e.g., Matthews, 2012;Niznik and Lintner, 2013). This variability in the SPCZ then results in variability in tracer ages; e.g., when the SPCZ is shifted to the northeast from its climatological there is less rapid transport from the NH and more from SH middle latitudes, resulting in older ages.…”

Section: Seasonal Variabilitymentioning

confidence: 99%

Spatial and temporal variability of interhemispheric transport times

Yang

Waugh

et al. 2018

Atmos. Chem. Phys.

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Abstract. The seasonal and interannual variability of transport times from the northern midlatitude surface into the Southern Hemisphere is examined using simulations of three idealized "age" tracers: an ideal age tracer that yields the mean transit time from northern midlatitudes and two tracers with uniform 50-and 5-day decay. For all tracers the largest seasonal and interannual variability occurs near the surface within the tropics and is generally closely coupled to movement of the Intertropical Convergence Zone (ITCZ). There are, however, notable differences in variability between the different tracers. The largest seasonal and interannual variability in the mean age is generally confined to latitudes spanning the ITCZ, with very weak variability in the southern extratropics. In contrast, for tracers subject to spatially uniform exponential loss the peak variability tends to be south of the ITCZ, and there is a smaller contrast between tropical and extratropical variability. These differences in variability occur because the distribution of transit times from northern midlatitudes is very broad and tracers with more rapid loss are more sensitive to changes in fast transit times than the mean age tracer. These simulations suggest that the seasonalinterannual variability in the southern extratropics of trace gases with predominantly NH midlatitude sources may differ depending on the gases' chemical lifetimes.

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“…Extensive assessment studies have reported that most reanalyses display a certain level of performance in terms of their absolute values (Betts et al, 1996(Betts et al, , 1998Zhou and Wang, 2016b), interannual variability (Lin et al, 2014;Lindsay et al, 2014;Wang, 2016a, 2017a;Wang and Zeng, 2012), distributions (Gervais et al, 2014;Heng et al, 2014;Mao et al, 2010) and relationships among variables (Niznik and Lintner, 2013;Cash III et al, 2015;Zhou et al, 2017;Zhou and Wang, 2016b;Betts, 2004) over regions worldwide. However, these aspects of reanalyses still contain certain errors that restrict the general use of reanalyses, especially in climate applications.…”

Section: Introductionmentioning

confidence: 99%

On the suitability of current atmospheric reanalyses for regional warming studies over China

Zhou

Wang

2018

Atmos. Chem. Phys.

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Abstract. Reanalyses are widely used because they add value to routine observations by generating physically or dynamically consistent and spatiotemporally complete atmospheric fields. Existing studies include extensive discussions of the temporal suitability of reanalyses in studies of global change. This study adds to this existing work by investigating the suitability of reanalyses in studies of regional climate change, in which land-atmosphere interactions play a comparatively important role. In this study, surface air temperatures (T a ) from 12 current reanalysis products are investigated; in particular, the spatial patterns of trends in T a are examined using homogenized measurements of T a made at ∼ 2200 meteorological stations in China from 1979 to 2010. The results show that ∼ 80 % of the mean differences in T a between the reanalyses and the in situ observations can be attributed to the differences in elevation between the stations and the model grids. Thus, the T a climatologies display good skill, and these findings rebut previous reports of biases in T a . However, the biases in theT a trends in the reanalyses diverge spatially (standard deviation = 0.15-0.30 • C decade −1 using 1 • × 1 • grid cells). The simulated biases in the trends in T a correlate well with those of precipitation frequency, surface incident solar radiation (R s ) and atmospheric downward longwave radiation (L d ) among the reanalyses (r = −0.83, 0.80 and 0.77; p < 0.1) when the spatial patterns of these variables are considered. The biases in the trends in T a over southern China (on the order of −0.07 • C decade −1 ) are caused by biases in the trends in R s , L d and precipitation frequency on the order of 0.10, −0.08 and −0.06 • C decade −1 , respectively. The biases in the trends in T a over northern China (on the order of −0.12 • C decade −1 ) result jointly from those in L d and precipitation frequency. Therefore, improving the simulation of precipitation frequency and R s helps to maximize the signal component corresponding to regional climate. In addition, the analysis of T a observations helps represent regional warming in ERA-Interim and JRA-55. Incorporating vegetation dynamics in reanalyses and the use of accurate aerosol information, as in the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), would lead to improvements in the modelling of regional warming. The use of the ensemble technique adopted in the twentieth-century atmospheric model ensemble ERA-20CM significantly narrows the uncertainties associated with regional warming in reanalyses (standard deviation = 0.15 • C decade −1 ).

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Circulation, Moisture, and Precipitation Relationships along the South Pacific Convergence Zone in Reanalyses and CMIP5 Models

Cited by 15 publications

References 37 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

Spatial and temporal variability of interhemispheric transport times

On the suitability of current atmospheric reanalyses for regional warming studies over China

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