scholarly journals Austral Spring Stratospheric and Tropospheric Circulation Interannual Variability

2011 ◽  
Vol 24 (11) ◽  
pp. 2629-2647 ◽  
Author(s):  
Eduardo Andrés Agosta ◽  
Pablo Osvaldo Canziani
Keyword(s):  
Interannual Variability ◽  
High Index ◽  
Stationary Waves ◽  
Energy Propagation ◽  
Central Pacific ◽  
Austral Spring ◽  
Circulation Patterns ◽  
Tropospheric Circulation ◽  
Phase Variability ◽  
Jet Structure

Abstract The relationship between the October (spring) total ozone column (TOC) midlatitude zonal asymmetry over the Southern Hemisphere (SH) and the stratospheric quasi-stationary wave 1 (QSW1) interannual phase variability is analyzed. Once contributions to the TOC from known global predictors, estimated with a multiregression model, are removed, the residual TOC interannual variability is observed to be dynamically coupled to the stratospheric QSW1 phase behavior. The stratospheric QSW1 interannual phase variability, when classified according to specifically designed indices, yields different circulation patterns in the troposphere and stratosphere. High (upper quartile) index values correspond to a westward rotation of the midlatitude ozone trough and the stratospheric QSW1 phase, while low (lower quartile) index values represent their eastward-rotated state. These values can be associated with statistically different tropospheric circulation patterns: a predominantly single poleward tropospheric jet structure for high index values and a predominantly double-jet structure for low index values. For the latter, there is a higher daily probability of double-jet occurrence in the troposphere and a stronger stratospheric jet. These jet structures and their daily behavior are supported by significant synoptic-scale activity anomalies over SH mid- to high latitudes as well as changes in tropospheric quasi-stationary waves 1–3. The wave activity flux (W flux) diagnosis shows the contribution of active quasi-stationary waves in the observed tropospheric anomalies associated with high and low index values. With low index values, the quasi-stationary waves lead to a self-sustaining state of the stratospheric–tropospheric coupled system. With high index values, the overall mid- to high latitude circulation is associated with wave energy propagation from the tropical central Pacific into higher latitudes. Thus, during the austral spring, there are interactions between the troposphere and stratosphere, leading to the locally well-defined upward and downward propagation of wave anomalies, that is, significant upper troposphere (UT)–lower stratosphere (LS) interactions can occur within a spring month itself.

scholarly journals Interannual Variability of Stratospheric Final Warming in the Southern Hemisphere and its Tropospheric Origin

2021 ◽  
pp. 1-59
Author(s):  
Soichiro Hirano ◽  
Masashi Kohma ◽  
Kaoru Sato
Keyword(s):  
Interannual Variability ◽  
Southern Hemisphere ◽  
Reanalysis Data ◽  
Stationary Waves ◽  
High Latitudes ◽  
Wave Source ◽  
Barotropic Model ◽  
Stratospheric Final Warming ◽  
Zonal Wavenumber ◽  
Favorable Conditions

AbstractThe relation between interannual variability of stratospheric final warming (SFW) and tropospheric circulation in the Southern Hemisphere (SH) is explored using reanalysis data and a linear barotropic model. The analysis is focused on quasi-stationary waves with zonal wavenumber 1 (s = 1 QSWs; s is zonal wavenumber), which are the dominant component of the SH extratropical planetary waves.First, interannual variability of SFW is investigated in terms of amplitudes of stratospheric and tropospheric s = 1 QSWs, and wave transmission properties of the mean flow from the late austral winter to spring. Upward Eliassen–Palm flux due to s = 1 QSWs is larger from the stratosphere down to the middle troposphere in early-SFW years than late-SFW years. More favorable conditions for propagation of s = 1 stationary waves into the stratosphere are identified in early-SFW years. These results indicate that the amplification of tropospheric s = 1 QSWs and the favorable conditions for their propagation into the stratosphere lead to the amplification of stratospheric s = 1 QSWs, and hence earlier SFWs.Next, numerical calculations using a linear barotropic model are performed to explore how tropospheric s = 1 QSWs at high latitudes amplifies in early-SFW years. By using tropical Rossby wave source and horizontal winds in the reanalysis data as a source and background field, respectively, differences in s = 1 steady responses between early- and late-SFWs are examined at high latitudes. It is suggested that the larger amplitudes of tropospheric s = 1 QSWs in early-SFW years are attributed to differences in wave propagation characteristics associated with structure of the midlatitude jets in austral spring.

scholarly journals A Comparison of Three Prolonged Periods of Heavy Rainfall over the Hawaiian Islands

2012 ◽  
Vol 51 (4) ◽  
pp. 722-744 ◽  
Author(s):  
I. M. Shiromani Jayawardena ◽  
Yi-Leng Chen ◽  
Andrew J. Nash ◽  
Kevin Kodama
Keyword(s):  
Heavy Rainfall ◽  
Large Scale ◽  
Hawaiian Islands ◽  
Hadley Circulation ◽  
Wind Component ◽  
Central Pacific ◽  
Optimal Position ◽  
Subtropical Jet ◽  
Circulation Patterns ◽  
Stormy Weather

AbstractThe anomalous circulation patterns during an unusually prolonged stormy-weather period in Hawaii from 19 February to 2 April 2006 are analyzed and are compared with those of two previously known prolonged heavy-rainfall periods (March 1951 and February 1979). The circulation patterns for these three periods are characterized by 1) a negative Pacific–North American (PNA) pattern in the midlatitudes with a blocking high southwest of the Aleutian Islands, 2) retraction and splitting of the zonal jet into a polar jet north of 50°N and a persistent subtropical jet to the south over the central Pacific Ocean, 3) an anomalous low west of the Hawaiian Islands embedded in the subtropical jet, and 4) a weaker-than-normal Hadley circulation in the mid-Pacific. The moisture advected from low latitudes by the southerly wind component east of the persistent anomalous low, combined with upward motion, provides the large-scale setting for the unusually prolonged unsettled weather across the Hawaiian Islands. For all three cases, the prolonged stormy weather started after the onset of large-scale blocking and a negative PNA pattern over the North Pacific and the occurrence of a persistent anomalous low embedded in the subtropical jet west of the Hawaiian Islands. Furthermore, the persistent low was located at the optimal position to bring moisture from the central equatorial Pacific to Hawaii. The stormy weather ceased after the midlatitude blocking pattern weakened and the anomalous low in the subtropics decayed and/or shifted westward. There are no apparent common precursors in the 2-week period prior to the prolonged stormy weather among these three cases, however.

scholarly journals Subtropical Cyclogenesis over the Central North Pacific*

2006 ◽  
Vol 21 (2) ◽  
pp. 193-205 ◽  
Author(s):  
Steven J. Caruso ◽  
Steven Businger
Keyword(s):  
Interannual Variability ◽  
North Pacific ◽  
Southern Oscillation ◽  
North Pacific Ocean ◽  
Baroclinic Instability ◽  
Cool Season ◽  
Central Pacific ◽  
Surface Development ◽  
Upper Level ◽  
Central North Pacific

Abstract The occurrence of subtropical cyclones over the central North Pacific Ocean has a significant impact on Hawaii’s weather and climate. In this study, 70 upper-level lows that formed during the period 1980–2002 are documented. In each case the low became cut off from the polar westerlies south of 30°N over the central Pacific, during the Hawaiian cool season (October–April). The objectives of this research are to document the interannual variability in the occurrence of upper-level lows, to chart the locations of their genesis and their tracks, and to investigate the physical mechanisms important in associated surface development. Significant interannual variability in the occurrence of upper-level lows was found, with evidence suggesting the influence of strong El Niño–Southern Oscillation events on the frequency of subtropical cyclogenesis in this region. Of the 70 upper-level lows, 43 were accompanied by surface cyclogenesis and classified as kona lows. Kona low formation is concentrated to the west-northwest of Hawaii, especially during October and November, whereas lows without surface development are concentrated in the area to the east-northeast of Hawaii. Kona low genesis shifts eastward through the cool season, favoring the area to the east-northeast of Hawaii during February and March, consistent with a shift in the climatological position of the trough aloft during the cool season. Consistent with earlier studies, surface deepening is well correlated with positive vorticity advection by the thermal wind. Static stability and advection of low-level moisture are less well correlated to surface deepening. These results suggest that kona low formation, to first order, is a baroclinic instability that originates in the midlatitudes, and that convection and latent-heat release play a secondary role in surface cyclogenesis.

scholarly journals Diversity of the Madden–Julian Oscillation: Initiation Region Modulated by the Interaction between the Intraseasonal and Interannual Variabilities

2021 ◽  
Vol 34 (6) ◽  
pp. 2297-2318
Author(s):  
Daisuke Takasuka ◽  
Masaki Satoh
Keyword(s):  
El Niño ◽  
El Nino ◽  
Eastern Pacific ◽  
Boreal Winter ◽  
Madden Julian Oscillation ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Sst Variability ◽  
Circulation Patterns ◽  
The Difference

AbstractAs one of the aspects of the diversity of the Madden–Julian oscillation (MJO), the modulation of initiation regions of the boreal-winter MJO is studied in terms of the relationship between intraseasonal and interannual variabilities. MJOs are categorized as those initiating in the Indian Ocean (IO), Maritime Continent (MC), and western Pacific (WP), referred to herein as IO-MJOs, MC-MJOs, and WP-MJOs, respectively. The composite analyses for each MJO category using observational data reveal that the diversity of MJO initiation regions directly results from the modulation of areas where horizontal advective premoistening efficiently occurs via intraseasonal/synoptic-scale winds. This is supported by the difference in the zonal location of equatorial intraseasonal circulations established before MJO initiation, which is related to a spatial change in background convection and associated Walker circulations forced by interannual sea surface temperature (SST) variability. Compared to IO-MJOs (favored in the climatological background on average), MC-MJOs tend to be realized under the eastern-Pacific El Niño–like condition, as a result of eastward-shifted intraseasonal convection and circulation patterns induced by background suppressed convection in the eastern MC. WP-MJOs are frequently initiated under the central-Pacific El Niño–like and positive IO dipole–like conditions, in which the WP is selectively moistened with the aid of background enhanced (suppressed) convection over the WP (the southeastern IO and the central-to-eastern Pacific). This major tendency derived from sample-limited observations is verified by a set of 15-yr numerical experiments with a global nonhydrostatic MJO-permitting model under a perpetual boreal-winter condition where observation-based SSTs are prescribed.

scholarly journals Contrasting behaviors of the atmospheric CO<sub>2</sub> interannual variability during two types of El Niños

2018 ◽  
Author(s):  
Jun Wang ◽  
Ning Zeng ◽  
Meirong Wang ◽  
Fei Jiang ◽  
Jingming Chen ◽  
...  
Keyword(s):  
Interannual Variability ◽  
El Niño ◽  
El Nino ◽  
Ecosystem Respiration ◽  
Atmospheric Co2 ◽  
Occurrence Rate ◽  
Central Pacific ◽  
Cp El Niño ◽  
El Niño Events ◽  
El Nino Events

Abstract. El Niño has two different flavors: eastern Pacific (EP) and central Pacific (CP) El Niños, with different global teleconnections. However, their different impacts on carbon cycle interannual variability remain unclear. We here compared the behaviors of the atmospheric CO2 interannual variability and analyzed their terrestrial mechanisms during these two types of El Niños, based on Mauna Loa (MLO) CO2 growth rate (CGR) and Dynamic Global Vegetation Models (DGVMs) historical simulations. Composite analysis shows that evolutions of MLO CGR anomaly have three clear differences in terms of (1) negative and neutral precursors in boreal spring of El Niño developing years (denoted as “yr0”), (2) strong and weak amplitudes, and (3) durations of peak from December (yr0) to April of El Niño decaying year (denoted as “yr1”) and from October (yr0) to January (yr1) during EP and CP El Niños, respectively. Models simulated global land–atmosphere carbon flux (FTA) is able to capture the essentials of these characteristics. We further find that the gross primary productivity (GPP) over the tropics and extratropical southern hemisphere (Trop+SH) generally dominates the global FTA variations during both El Niño types. Regionally, significant anomalous carbon uptake caused by more precipitation and colder temperature, corresponding to the negative precursor, occurs between 30° S and 20° N from January (yr0) to June (yr0), while the strongest anomalous carbon releases, due largely to the reduced GPP induced by low precipitation and warm temperature, happen between equator and 20° N from February (yr1) to August (yr1) during EP El Niño events. In contrast, during CP El Niño events, clear carbon releases exist between 10° N and 20° S from September (yr0) to September (yr1), resulted from the widespread dry and warm climate conditions. Different spatial patterns of land temperature and precipitation in different seasons associated with EP and CP El Niños account for the characteristics in evolutions of GPP, terrestrial ecosystem respiration (TER), and resultant FTA. Understanding these different behaviors of the atmospheric CO2 interannual variability along with their terrestrial mechanisms during EP and CP El Niños is important because CP El Niño occurrence rate might increase under global warming.

Euphausiids in the Coral and Tasman Seas during May 1972. II. Horizontal Distribution in relation to Circulation Patterns

1979 ◽  
Vol 30 (5) ◽  
pp. 569 ◽  
Author(s):  
FB Griffiths
Keyword(s):  
Water Mass ◽  
New Caledonia ◽  
Solomon Islands ◽  
Horizontal Distribution ◽  
Central Pacific ◽  
Circulation Patterns ◽  
Group A ◽  
Group B ◽  
High Degree ◽  
Group D

An examination of the euphausiid species collected at two stations, 20� S.,153� E. and 33� 40'S.,153� E., during May 1972 showed that 21 of the 33 epipelagic and mesopelagic species were common to both stations. This suggests a high degree of water mass continuity between these two stations. This paper discusses the horizontal distribution of 10 species, divided into four groups, who show range extensions that are related to circulation patterns in the Coral and Tasman Seas. The presence of group A animals (Thysanopoda tricuspidata, Euphausia diomedeae, E. pseudogibba, and Nematoscelis gracilis) at the southern station supports the theory that there is a southward movement of South Equatorial water from between the Solomon Islands and New Caledonia to at least 33� 44'S. This water must have passed over, or close to the continental shelf, probably as part of the East Australian Current in order for the neritic Pseudeuphausia latrifrons (group B) to be caught at the southern station. The species present in group C (Euphausia similis and Thysanoessa gregaria) indicate there had been northern transport of central Tasman water to at least 20� S., possibly along 160� E. or further east. Finally, the group D species (Euphausia brevis, Nematoscelis atlantica and N. tenella) suggest there may have been some westwards flow from the west central Pacific region, possibly during the previous June-December period.

scholarly journals Three-dimensional climatology, trends and meteorological drivers of global and regional tropospheric type-dependent aerosols: Insights from 13 years (2007–2019) of CALIOP observations

2021 ◽  
Author(s):  
Ke Gui ◽  
Huizheng Che ◽  
Yu Zheng ◽  
Hujia Zhao ◽  
Wenrui Yao ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Three Dimensional ◽  
Lower Troposphere ◽  
Distribution Patterns ◽  
Orthogonal Polarization ◽  
Aerosol Layer ◽  
Aerosol Extinction ◽  
Satellite Measurements ◽  
Central Pacific ◽  
Aerosol Extinction Coefficient

Abstract. Globally gridded aerosol extinction data from the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) during 2007–2019 are utilized to investigate the three-dimensional (3D) climatological distribution of tropospheric type-dependent aerosols, and to identify the trends in column aerosol optical depth (AOD), partitioned within different altitude regimes, and their meteorological drivers. Using detection samples of layer aerosols, we also yield a 3D distribution of the frequency-of-occurrence (FoO) of aerosol sub-types classified by CALIOP. The results show that the aerosol extinction coefficient (AEC) shows contrasting vertical distribution patterns over land and ocean, with the former possessing significant geographical dependence, while the enhancement of AEC in the latter is mainly located below 1 km. The vertical structures of the type-dependent AECs, however, are strongly dependent on altitude. When the total AOD (TAOD) is partitioned into the planetary boundary layer (PBL) and the free troposphere (FT), results demonstrate that the PBL and FT contribute 61.86 % and 38.13 %, respectively, of the global tropospheric TAOD averaged over daytime and nighttime. Yet, this CALIOP-based partitioning of the different aerosol sub-types in the PBL and FT varies significantly. Among all 12 typical regions of interest analyzed, more than 50 % of TAOD is located in the lower troposphere (0–2 km), while the contribution is less than 2 % above 6 km. In global average terms, we found the aerosol FoO averaged over all layers is 4.45 %, with the largest contribution from ‘clean marine’ (1.79 %) and the smallest from ‘clean continental’ (0.05 %). Overall, the FoO vertical structures of the aerosol layer exhibit a distribution pattern similar to that of AEC. The resulting trend analyses show that CALIOP accurately captures significant regional anomalies in TAOD, as observed in other satellite measurements and aerosol reanalysis. Our correlation analysis between meteorological factors and TAOD suggests the interannual variability of TAOD is related to the variability of precipitation (PPT), volumetric soil moisture (VSM), and wind speed (WS) in the particular regions. For instance, the positive TAOD trend over the equatorial central Pacific is mainly attributable to the increased PPT and decreased WS. In contrast, in dry convective regions dominated by dust and smoke, the interannual variability/trend in TAOD is largely modified by the VSM driven by the PPT. Additionally, we further found these significant regional correlations are more robust within the PBL and significantly weakened or even reversed within the FT. This highlights the superiority of using the TAOD partitioned within the PBL as a proxy variable for the widely applied TAOD to explore the relationships between atmospheric pollution and meteorology.

The Combined Influence of the Stratospheric Polar Vortex and ENSO on Zonal Asymmetries in the Southern Hemisphere Upper Tropospheric Circulation during Austral Spring and Summer

2021 ◽  
Author(s):  
Marisol Osman ◽  
Theodore Shepherd ◽  
Carolina Vera
Keyword(s):  
Southern Hemisphere ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Austral Spring ◽  
Stratospheric Polar Vortex ◽  
Wave Source ◽  
Weather Forecasts ◽  
Rossby Wave Source ◽  
Enso Teleconnections ◽  
Tropospheric Circulation

&lt;p&gt;The influence of El Nin&amp;#771;o Southern Oscillation (ENSO) and the Stratospheric Polar Vortex (SPV) on the zonal asymmetries in the Southern Hemisphere atmospheric circulation during spring and summer is examined. The main objective is to explore if the SPV can modulate the ENSO teleconnections in the extratropics. We use a large ensemble of seasonal hindcasts from the European Centre for Medium-Range Weather Forecasts Integrated Forecast System to provide a much larger sample size than is possible from the observations alone.&lt;/p&gt;&lt;p&gt;We find a small but statistically significant relationship between ENSO and the SPV, with El Nin&amp;#771;o events occurring with weak SPV and La Nin&amp;#771;a events occurring with strong SPV more often than expected by chance, in agreement with previous works. We show that the zonally asymmetric response to ENSO and SPV can be mainly explained by a linear combination of the response to both forcings, and that they can combine constructively or destructively. From this perspective, we find that the tropospheric asymmetries in response to ENSO are more intense when El Nin&amp;#771;o events occur with weak SPV and La Nin&amp;#771;a events occur with strong SPV, at least from September through December. In the stratosphere, the ENSO teleconnections are mostly confounded by the SPV signal. The analysis of Rossby Wave Source and of wave activity shows that both are stronger when El Nin&amp;#771;o events occur together with weak SPV, and when La Nin&amp;#771;a events occur together with strong SPV.&lt;/p&gt;

scholarly journals Climate-Driven Variability in the Southern Ocean Carbonate System

2015 ◽  
Vol 28 (13) ◽  
pp. 5335-5350 ◽  
Author(s):  
Christopher J. Conrad ◽  
Nicole S. Lovenduski
Keyword(s):  
Southern Ocean ◽  
Interannual Variability ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean Surface ◽  
Positive Trend ◽  
Central Pacific ◽  
Carbonate System ◽  
Substantial Impact ◽  
Vertical Advection

Abstract Seasonal and interannual variability in the Southern Ocean carbonate system is investigated using output from a historically forced (1948–2007) ocean general circulation model with embedded biogeochemistry. Atmospheric CO2 is fixed at preindustrial levels to investigate carbonate system variability in the absence of an anthropogenic CO2 perturbation. It is found that nearly a quarter of interannual variability in Southern Ocean Pacific sector surface carbonate ion concentration can be explained by variability in ENSO, with Pacific sector surface decreasing by 0.43 mmol m−3 per standard deviation decrease in the ENSO-3.4 index. ENSO-related variability in vertical advection of dissolved inorganic carbon (DIC) drives this relationship between ENSO and surface . It is also found that positive phases of the southern annular mode (SAM) are associated with decreased Southern Ocean surface , an association driven by SAM-related variability in vertical advection of DIC. Despite the influence of the SAM on interannual variability in surface , only 4.5% of the trend in natural Southern Ocean surface exhibits linear congruence with the trend in wind stress. Given this, the authors predict that the positive trend in the SAM will not have a substantial impact on ocean acidification. Last, ENSO is found to alter the wintertime minimum in surface . Assuming a business-as-usual acidification rate of 0.5 mmol m−3 yr−1, exacerbation of the wintertime minimum during La Niña conditions may advance the date of aragonite undersaturation within the central Pacific sector of the Southern Ocean by as much as 8 yr.

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