scholarly journals A Basic Effect of Cloud Radiative Effects on Tropical Sea Surface Temperature Variability

2020 ◽  
Vol 33 (10) ◽  
pp. 4333-4346 ◽  
Author(s):  
Ying Li ◽  
David W. J. Thompson ◽  
Dirk Olonscheck
Keyword(s):  
Atmospheric Circulation ◽  
Time Scales ◽  
Southern Oscillation ◽  
Critical Role ◽  
Surface Energy Budget ◽  
Sea Surface ◽  
Turbulent Heat ◽  
Radiative Effects ◽  
Decadal Scale ◽  
Cloud Radiative Effects

AbstractCloud radiative effects (CREs) are known to play a central role in governing the long-term mean distribution of sea surface temperatures (SSTs). Very recent work suggests that CREs may also play a role in governing the variability of SSTs in the context of El Niño–Southern Oscillation. Here, the authors exploit numerical simulations in the Max Planck Institute Earth System Model with two different representations of CREs to demonstrate that coupling between CREs and the atmospheric circulation has a much more general and widespread effect on tropical climate than that indicated in previous work. The results reveal that coupling between CREs and the atmospheric circulation leads to robust increases in SST variability on time scales longer than a month throughout the tropical oceans. Remarkably, cloud–circulation coupling leads to more than a doubling of the amplitude of decadal-scale variability in tropical-mean SSTs. It is argued that the increases in tropical SST variance derive primarily from the coupling between SSTs and shortwave CREs: Coupling increases the memory in shortwave CREs on hourly and daily time scales and thus reddens the spectrum of shortwave CREs and increases their variance on time scales spanning weeks to decades. Coupling between SSTs and CREs does not noticeably affect the variance of SSTs in the extratropics, where the effects from variability in CREs on the surface energy budget are much smaller than the effects from the turbulent heat fluxes. The results indicate a basic but critical role of CREs in climate variability throughout the tropics.

scholarly journals The nonlinear variation of drought and its relation to atmospheric circulation in Shandong Province, East China

PeerJ ◽  
2015 ◽  
Vol 3 ◽  
pp. e1289 ◽  
Author(s):  
Baofu Li ◽  
Zhongsheng Chen ◽  
Xingzhong Yuan
Keyword(s):  
Atmospheric Circulation ◽  
Decadal Variability ◽  
Southern Oscillation ◽  
Linear Trend ◽  
Pearson Correlation ◽  
Phase Changes ◽  
Drought Severity ◽  
Nonlinear Variation ◽  
Decadal Scale ◽  
Annual Scale

Considerable attention has recently been devoted to the linear trend of drought at the decadal to inter-decadal time scale; however, the nonlinear variation of drought at multi-decadal scales and its relation to atmospheric circulation need to be further studied. The linear and nonlinear variations of the Palmer drought severity index (PDSI) in Shandong from 1900 to 2012 and its relations to the Pacific decadal oscillation (PDO), El Niño-Southern Oscillation (ENSO), Siberian high (SH) and Southern Oscillation (SO) phase changes from multi-scale are detected using linear regression, the Mann–Kendall test, ensemble empirical mode decomposition (EEMD) and the Pearson correlation analysis method. The results indicate that the PDSI shows no statistically significant linear change trend from 1900 to 2012; however, before (after) the late 1950s, PDSI shows a significant upward (downward) trend (P< 0.01) with a linear rate of 0.28/decade (−0.48/decade). From 1900 to 2012, the PDSI also exhibits a nonlinear variation trend at the inter-annual scale (quasi-3 and quasi-7-year), inter-decadal scale (quasi-14-year) and multi-decadal scale (quasi-46 and quasi-65-year). The variance contribution rate of components from the inter-annual scale is the largest, reaching 38.7%, and that from the inter-decadal scale and multi-decadal scale are 18.9% and 19.0%, respectively, indicating that the inter-annual change exerts a huge influence on the overall PDSI change. The results also imply that the effect of the four atmospheric circulations (PDO, ENSO, SH, SO) on PDSI at the multi-decadal variability scale are more important than that at the other scales. Consequently, we state that PDSI variation at the inter-annual scale has more instability, while that at the inter-decadal and multi-decadal scale is more strongly influenced by natural factors.

scholarly journals A statistical and process oriented evaluation of cloud radiative effects in high resolution global models

2018 ◽  
Author(s):  
Manu Anna Thomas ◽  
Abhay Devasthale ◽  
Torben Koenigk ◽  
Klaus Wyser ◽  
Malcolm Roberts ◽  
...  
Keyword(s):  
High Resolution ◽  
Southern Oscillation ◽  
Global Climate Model ◽  
Radiant Energy ◽  
Horizontal Resolution ◽  
Radiative Effects ◽  
Resolution Model ◽  
High Resolution Model ◽  
Cloud Radiative Effects ◽  
The Impact

Abstract. This study evaluates the impact of atmospheric horizontal resolution on the representation of cloud radiative effects (CREs) in an ensemble of global climate model simulations following the protocols of the High Resolution Model Intercomparison Project (HighResMIP). We compare results from four European modelling centres, each of which provides data from "standard" and "high" resolution model configurations. Simulated radiative fluxes are compared with observation-based estimates derived from the Clouds and Earth's Radiant Energy System (CERES) dataset. Model CRE biases are evaluated using both conventional statistics (e.g. time and spatial averages) and after conditioning on the phase of two modes of internal climate variability, namely the El Niño and Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). Simulated top-of-atmosphere (TOA) and surface CREs show large biases over the polar regions, particularly over regions where seasonal sea-ice variability is strongest. Increasing atmospheric resolution does not significantly improve these biases. The spatial structure of the cloud radiative response to ENSO and NAO variability is simulated reasonably well by all model configurations considered in this study. However, it is difficult to identify a systematic impact of atmospheric resolution on the associated CRE errors. Mean absolute CRE errors conditioned on ENSO phase are relatively large (5–10 W/m2) and show differences between models. We suggest this is a consequence of differences in the parameterization of SW radiative transfer and the treatment of cloud optical properties rather than a result of differences in resolution. In contrast, mean absolute CRE errors conditioned on NAO phase are generally smaller (0–2 W/m2) and more similar across models. Although the regional details of CRE biases show some sensitivity to atmospheric resolution within a particular model, it is difficult to identify patterns that hold across all models. This apparent insensitivity to increased atmospheric horizontal resolution indicates that physical parameterizations play a dominant role in determining the behaviour of cloud-radiation feedbacks. However, we note that these results are obtained from atmosphere-only simulations and the impact of changes in atmospheric resolution may be different in the presence of coupled climate feedbacks.

scholarly journals Seasonal-to-Interannual Variability of Ethiopia/Horn of Africa Monsoon. Part I: Associations of Wavelet-Filtered Large-Scale Atmospheric Circulation and Global Sea Surface Temperature

2009 ◽  
Vol 22 (12) ◽  
pp. 3396-3421 ◽  
Author(s):  
Zewdu T. Segele ◽  
Peter J. Lamb ◽  
Lance M. Leslie
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Atmospheric Circulation ◽  
Time Scales ◽  
Time Scale ◽  
Climate System ◽  
Sea Surface ◽  
Horn Of Africa ◽  
Annual Mode ◽  
Global Sea Surface Temperature

Abstract Horn of Africa rainfall varies on multiple time scales, but the underlying climate system controls on this variability have not been examined comprehensively. This study therefore investigates the linkages between June–September Horn of Africa (especially Ethiopian) rainfall and regional atmospheric circulation and global sea surface temperature (SST) variations on several key time scales. Wavelet analysis of 5-day average or monthly total rainfall for 1970–99 identifies the dominant coherent modes of rainfall variability. Several regional atmospheric variables and global SST are then identically wavelet filtered, based on the rainfall frequency bands. Regression, correlation, and composite analyses are subsequently used to identify the most important rainfall–climate system time-scale relationships. The results show that Ethiopian monsoon rainfall variation is largely linked with annual time-scale atmospheric circulation patterns involving variability in the major components of the monsoon system. Although variability on the seasonal (75–210 days), quasi-biennial (QB; 1.42–3.04 yr), and El Niño–Southern Oscillation (ENSO; 3.04–4.60 yr) time scales accounts for much less variance than the annual mode (210 days–1.42 yr), they significantly affect Ethiopian rainfall by preferentially modulating the major regional monsoon components and remote teleconnection linkages. The seasonal time scale largely acts in phase with the annual mode, by enhancing or reducing the lower-tropospheric southwesterlies from the equatorial Atlantic during wet or dry periods. The wet QB phase strengthens the Azores and Saharan high and the tropical easterly jet (TEJ) over the Arabian Sea, while the wet ENSO phase enhances the Mascarene high, the TEJ, and the monsoon trough more locally. The effects of tropical SST on Ethiopian rainfall also are prominent on the QB and ENSO time scales. While rainfall–SST correlations for both the QB and ENSO modes are strongly positive (negative) over the equatorial western (eastern) Pacific, only ENSO exhibits widespread strong negative correlations over the Indian Ocean. Opposite QB and ENSO associations tend to characterize dry Ethiopian conditions. The relationships identified on individual time scales now are being used to develop and validate statistical prediction models for Ethiopia.

scholarly journals Fine Pattern of Natural Modes in Sea Surface Temperature Variability: 1985–2003

2008 ◽  
Vol 38 (2) ◽  
pp. 314-336 ◽  
Author(s):  
Ge Chen ◽  
Haitao Li
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Time Scales ◽  
Southern Oscillation ◽  
Oscillation Mode ◽  
Sea Surface ◽  
Spatiotemporal Pattern ◽  
Natural Mode ◽  
Unique Contribution ◽  
Natural Modes

Abstract A natural mode refers, in this study, to a periodic oscillation of sea surface temperature (SST) that is geophysically significant on a global, regional, or local scale. Using a newly developed harmonic extraction scheme by Chen, which has the advantage of being space–time decoupled and fully data adaptive, a variety of natural modes have been recovered from global monthly SST data for the period of 1985–2003. Among them, the eight most significant modes are identified as primary modes, whose spatial patterns are presented, along with their phase distributions. At seasonal time scales, a 4-month primary mode is uncovered in addition to the well-documented annual and semiannual cycles. At interannual time scales, the dominant El Niño–Southern Oscillation (ENSO) variability is found to be composed of at least five primary modes, with well-defined central periods around 18, 25, 32, 43, and 63 months. At time scales beyond ENSO, a decadal SST signal with an average period of 10.3 yr is observed. A unique contribution of this study is the derivation and presentation of fine patterns of natural SST modes and signals in joint dimensions of time, space, period, and phase, leading to several findings and conclusions that are of potential importance: 1) The degree of separability and regularity of the sub-ENSO modes is surprising, and thus reveals new details on the nature of this event. 2) The midlatitude counterparts of the equatorial interannual and decadal SST modes/signals are found in the two hemispheres with a frequency shift toward longer periods. The “shadows” of the Pacific Ocean’s ENSO modes are also observed with some detail in the Atlantic and the Indian Oceans. All of these provide direct evidence that teleconnections exist between the equatorial and extratropical oceans, as well as among the tropical Pacific, tropical Atlantic, and tropical Indian Oceans, possibly as a result of the “atmospheric bridge.” 3) A sharply opposite anisotropy is observed in the spatiotemporal pattern between the interannual modes and decadal signals, implying that they are potentially of a categorical difference in origin. 4) Locality or regionality is a fundamental feature for most of the SST modes. Treating the interannual or decadal variability as a single ENSO or Pacific decadal oscillation mode appears to be an oversimplification, and may lead to inappropriate interpretations. The results herein represent an improved knowledge of the natural variability in sea surface temperature, which will hopefully help to enhance the understanding of natural fluctuations of the global/regional climate system in the context of ocean–atmosphere interaction.

scholarly journals Weakening of the Tropical Atmospheric Circulation Response to Local Sea Surface Temperature Anomalies under Global Warming

2017 ◽  
Vol 30 (20) ◽  
pp. 8149-8158 ◽  
Author(s):  
Ping Huang ◽  
Dong Chen ◽  
Jun Ying
Keyword(s):  
Global Warming ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Atmospheric Circulation ◽  
Southern Oscillation ◽  
Atmospheric Stability ◽  
Coupled Model ◽  
Tropical Climate ◽  
Sea Surface ◽  
Sst Anomalies

Abstract In the tropics, the atmospheric circulation response to sea surface temperature (SST) anomalies is a crucial part of the tropical air–sea interaction—the primary process of tropical climate. How it will change under global warming is of great importance to tropical climate change. Here, it is shown that the atmospheric vertical circulation response to local SST anomalies will likely be weakened under global warming using 28 selected models from phase 5 of the Coupled Model Intercomparison Project. The weakening of the circulation response to SST anomalies is closely tied to the increased atmospheric stability under global warming, which increases at the same rate as the circulation response decreases—around 8% for 1 K of tropical-mean SST warming. The spatial pattern of background warming can modify—especially in the equatorial central-eastern Pacific—the spatial distribution of the changes in the circulation response. The atmospheric response to SST anomalies may increase where the local background warming is pronouncedly greater than the tropical mean. The general weakening of the atmospheric circulation response to SST anomalies leads to a decreased circulation response to the structured variability of tropical SST anomalies, such as the El Niño–Southern Oscillation and the Indian Ocean dipole. The decreased circulation response will offset some of the enhancement of the tropical rainfall response to these SST modes as a result of global-warming-induced moisture increase and also implies a decreased amplitude of the tropical air–sea interaction modes.

A Southwest Pacific Tropical Cyclone Climatology and Linkages to the El Niño–Southern Oscillation

2013 ◽  
Vol 26 (1) ◽  
pp. 3-25 ◽  
Author(s):  
Howard J. Diamond ◽  
Andrew M. Lorrey ◽  
James A. Renwick
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Atmospheric Circulation ◽  
Tropical Cyclones ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Sea Surface ◽  
Southwest Pacific ◽  
Enso Phases

Abstract The new South Pacific Enhanced Archive for Tropical Cyclones (SPEArTC) dataset provides an opportunity to develop a more complete climatology of tropical cyclones (TCs) in the southwest Pacific. Here, spatial patterns and characteristics of TCs for the 41-yr period beginning with the 1969/70 season are related to phases of the El Niño–Southern Oscillation (ENSO), taking into account the degree of ocean–atmosphere coupling. Twentieth-century reanalysis data and the coupled ENSO index (CEI) were used to investigate TC genesis areas and climate diagnostics in the extratropical transition (ETT) region at and south of 25°S during different CEI ENSO phases. This is the first study looking at CEI-based ENSO phases and the more detailed relationship of TCs to the coupling of the ocean and atmosphere during different ENSO phases. Consistent with previous findings, positive relationships exist among TCs, sea surface temperature, and atmospheric circulation. A statistically significant greater frequency of major TCs was found during the latter half of the study period (1991–2010) compared to the 1970–90 period, again consistent with the findings of other studies. Also found were significant and consistent linkages highlighting the interplay of TCs and sea surface temperature (SSTs) in the southwest Pacific basin west of 170°E and a closer connection to atmospheric circulation east of 170°E. Moreover, this study demonstrates subtle differences between a fully coupled El Niño or La Niña and atmospheric- or ocean-dominated phases, or neutral conditions.

Interdecadal Amplitude Modulation of El Niño–Southern Oscillation and Its Impact on Tropical Pacific Decadal Variability*

2013 ◽  
Vol 26 (18) ◽  
pp. 7280-7297 ◽  
Author(s):  
Tomomichi Ogata ◽  
Shang-Ping Xie ◽  
Andrew Wittenberg ◽  
De-Zheng Sun
Keyword(s):  
Amplitude Modulation ◽  
El Niño ◽  
Decadal Variability ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Sea Surface ◽  
El Nino Southern Oscillation ◽  
Pacific Decadal Variability ◽  
Decadal Scale

Abstract The amplitude of El Niño–Southern Oscillation (ENSO) displays pronounced interdecadal modulations in observations. The mechanisms for the amplitude modulation are investigated using a 2000-yr preindustrial control integration from the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1 (GFDL CM2.1). ENSO amplitude modulation is highly correlated with the second empirical orthogonal function (EOF) mode of tropical Pacific decadal variability (TPDV), which features equatorial zonal dipoles in sea surface temperature (SST) and subsurface temperature along the thermocline. Experiments with an ocean general circulation model indicate that both interannual and decadal-scale wind variability are required to generate decadal-scale tropical Pacific temperature anomalies at the sea surface and along the thermocline. Even a purely interannual and sinusoidal wind forcing can produce substantial decadal-scale effects in the equatorial Pacific, with SST cooling in the west, subsurface warming along the thermocline, and enhanced upper-ocean stratification in the east. A mechanism is proposed by which residual effects of ENSO could serve to alter subsequent ENSO stability, possibly contributing to long-lasting epochs of extreme ENSO behavior via a coupled feedback with TPDV.

scholarly journals On the Observed Relationships between Wintertime Variability in Kuroshio–Oyashio Extension Sea Surface Temperatures and the Atmospheric Circulation over the North Pacific

2018 ◽  
Vol 31 (12) ◽  
pp. 4669-4681 ◽  
Author(s):  
Samantha M. Wills ◽  
David W. J. Thompson
Keyword(s):  
Atmospheric Circulation ◽  
North Pacific ◽  
Sea Surface ◽  
Western Boundary ◽  
Turbulent Heat ◽  
Sea Surface Temperatures ◽  
The North ◽  
Surface Temperatures ◽  
The North Pacific ◽  
Sst Anomalies

Observational analyses reveal that wintertime variations in sea surface temperatures (SST) in the Kuroshio–Oyashio Extension (KOE) region of the North Pacific are associated with two distinct and robust patterns of atmospheric variability: 1) a pattern that peaks in amplitude approximately 2–3 weeks prior to large KOE SST anomalies and is consistent with atmospheric forcing of the SST field and 2) a very different pattern that lags SST anomalies in the KOE region by approximately a month. The latter pattern is dominated by low sea level pressure anomalies and turbulent heat fluxes directed into the atmosphere over warm SST anomalies and is interpreted as the transient atmospheric response to SST anomalies over the KOE region. The results contribute to a growing body of evidence that suggests variations in SSTs in the midlatitude oceans are capable of significantly influencing the large-scale atmospheric circulation, especially near western boundary currents.

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