Journal articles: 'Large-scale atmospheric circulation'

1

Gastineau, Guillaume, Laurent Li, and Hervé Le Treut. "Some Atmospheric Processes Governing the Large-Scale Tropical Circulation in Idealized Aquaplanet Simulations." Journal of the Atmospheric Sciences 68, no. 3 (March 1, 2011): 553–75. http://dx.doi.org/10.1175/2010jas3439.1.

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Abstract The large-scale tropical atmospheric circulation is analyzed in idealized aquaplanet simulations using an atmospheric general circulation model. Idealized sea surface temperatures (SSTs) are used as lower-boundary conditions to provoke modifications of the atmospheric general circulation. Results show that 1) an increase in the meridional SST gradients of the tropical region drastically strengthens the Hadley circulation intensity, 2) the presence of equatorial zonal SST anomalies weakens the Hadley cells and reinforces the Walker circulation, and 3) a uniform SST warming causes small and nonsystematic changes of the Hadley and Walker circulations. In all simulations, the jet streams strengthen and move equatorward as the Hadley cells strengthen and become narrower. Some relevant mechanisms are then proposed to interpret the large range of behaviors obtained from the simulations. First, the zonal momentum transport by transient and stationary eddies is shown to modulate the eddy-driven jets, which causes the poleward displacements of the jet streams. Second, it is found that the Hadley circulation adjusts to the changes of the poleward moist static energy flux and gross moist static stability, associated with the geographical distribution of convection and midlatitude eddies. The Walker circulation intensity corresponds to the zonal moist static energy transport induced by the zonal anomalies of the turbulent fluxes and radiative cooling. These experiments provide some hints to understand a few robust changes of the atmospheric circulation simulated by ocean–atmosphere coupled models for future and past climates.

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Jacobeit, Jucundus, Joachim Rathmann, Aandreas Philipp, and Philip D. Jones. "Central European precipitation and temperature extremes in relation to large-scale atmospheric circulation types." Meteorologische Zeitschrift 18, no. 4 (August 1, 2009): 397–410. http://dx.doi.org/10.1127/0941-2948/2009/0390.

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Hoskins, Brian, Richard Neale, Mark Rodwell, and Gui-Ying Yang. "Aspects of the large-scale tropical atmospheric circulation." Tellus B: Chemical and Physical Meteorology 51, no. 1 (January 1999): 33–44. http://dx.doi.org/10.3402/tellusb.v51i1.16258.

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HOSKINS, BRIAN, RICHARD NEALE, MARK RODWELL, and GUI-YING YANG. "Aspects of the large-scale tropical atmospheric circulation." Tellus A 51, no. 1 (January 1999): 33–44. http://dx.doi.org/10.1034/j.1600-0870.1999.t01-1-00004.x.

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HOSKINS, BRIAN, RICHARD NEALE, MARK RODWELL, and GUI-YING YANG. "Aspects of the large-scale tropical atmospheric circulation." Tellus B 51, no. 1 (February 1999): 33–44. http://dx.doi.org/10.1034/j.1600-0889.1999.00004.x.

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Hoskins, Brian, Richard Neale, Mark Rodwell, and Gui-Ying Yang. "Aspects of the large-scale tropical atmospheric circulation." Tellus A: Dynamic Meteorology and Oceanography 51, no. 1 (January 1999): 33–44. http://dx.doi.org/10.3402/tellusa.v51i1.12287.

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7

Balcerak, Ernie. "Large-scale atmospheric circulation affects particulate matter levels." Eos, Transactions American Geophysical Union 94, no. 40 (October 1, 2013): 360. http://dx.doi.org/10.1002/2013eo400018.

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Brönnimann, Stefan, Alexander Stickler, Thomas Griesser, Andreas M. Fischer, Andrea Grant, Tracy Ewen, Tianjun Zhou, Martin Schraner, Eugene Rozanov, and Thomas Peter. "Variability of large-scale atmospheric circulation indices for the northern hemisphere during the past 100 years." Meteorologische Zeitschrift 18, no. 4 (August 1, 2009): 379–96. http://dx.doi.org/10.1127/0941-2948/2009/0389.

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9

Han, Cunbo, Slavko Brdar, Siegfried Raasch, and Stefan Kollet. "Large‐eddy simulation of catchment‐scale circulation." Quarterly Journal of the Royal Meteorological Society 145, no. 720 (March 5, 2019): 1218–33. http://dx.doi.org/10.1002/qj.3491.

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10

Li, Ying, David W. J. Thompson, and Sandrine Bony. "The Influence of Atmospheric Cloud Radiative Effects on the Large-Scale Atmospheric Circulation." Journal of Climate 28, no. 18 (September 11, 2015): 7263–78. http://dx.doi.org/10.1175/jcli-d-14-00825.1.

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Abstract The influence of clouds on the large-scale atmospheric circulation is examined in numerical simulations from an atmospheric general circulation model run with and without atmospheric cloud radiative effects (ACRE). In the extratropics of both hemispheres, the primary impacts of ACRE on the circulation include 1) increases in the meridional temperature gradient and decreases in static stability in the midlatitude upper troposphere, 2) strengthening of the midlatitude jet, 3) increases in extratropical eddy kinetic energy by up to 30%, and 4) increases in precipitation at middle latitudes but decreases at subtropical latitudes. In the tropics, the primary impacts of ACRE include 1) eastward wind anomalies in the tropical upper troposphere–lower stratosphere (UTLS) and 2) reductions in tropical precipitation. The impacts of ACRE on the atmospheric circulation are interpreted in the context of a series of dynamical and physical processes. The changes in the extratropical circulation and precipitation are consistent with the influence of ACRE on the baroclinicity and eddy fluxes of momentum in the extratropical upper troposphere, the changes in the zonal wind in the UTLS with the influence of ACRE on the amplitude of the equatorial planetary waves, and the changes in the tropical precipitation with the energetic constraints on the tropical troposphere. The results make clear that ACRE have a pronounced influence on the atmospheric circulation not only at tropical latitudes, but at extratropical latitudes as well. They highlight the critical importance of correctly simulating ACRE in global climate models.

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Ding, Y. H., and Akimasa Sumi. "Large-Scale Atmospheric Circulation Features during TOGA-COARE IOP." Journal of the Meteorological Society of Japan. Ser. II 73, no. 2B (1995): 339–51. http://dx.doi.org/10.2151/jmsj1965.73.2b_339.

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Yu, Bin, and Anthony R. Lupo. "Large-Scale Atmospheric Circulation Variability and Its Climate Impacts." Atmosphere 10, no. 6 (June 18, 2019): 329. http://dx.doi.org/10.3390/atmos10060329.

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13

Hogg, Andrew Mc C., William K. Dewar, Pavel Berloff, Sergey Kravtsov, and David K. Hutchinson. "The Effects of Mesoscale Ocean–Atmosphere Coupling on the Large-Scale Ocean Circulation." Journal of Climate 22, no. 15 (August 1, 2009): 4066–82. http://dx.doi.org/10.1175/2009jcli2629.1.

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Abstract Small-scale variation in wind stress due to ocean–atmosphere interaction within the atmospheric boundary layer alters the temporal and spatial scale of Ekman pumping driving the double-gyre circulation of the ocean. A high-resolution quasigeostrophic (QG) ocean model, coupled to a dynamic atmospheric mixed layer, is used to demonstrate that, despite the small spatial scale of the Ekman-pumping anomalies, this phenomenon significantly modifies the large-scale ocean circulation. The primary effect is to decrease the strength of the nonlinear component of the gyre circulation by approximately 30%–40%. This result is due to the highest transient Ekman-pumping anomalies destabilizing the flow in a dynamically sensitive region close to the western boundary current separation. The instability of the jet produces a flux of potential vorticity between the two gyres that acts to weaken both gyres.

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Chou, Ming-Dah, Chi-Hua Wu, and Wen-Shung Kau. "Large-Scale Control of Summer Precipitation in Taiwan." Journal of Climate 24, no. 19 (October 2011): 5081–93. http://dx.doi.org/10.1175/2011jcli4057.1.

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Taiwan is located at the western stretch of the North Pacific high pressure (NP high) ridge in boreal summer, and its climate is highly sensitive to the NP high. By grouping years of anomalously high and low summer precipitation in Taiwan, this study investigated the large-scale atmospheric circulation and the land–sea temperature contrast during these two groups of years and identified the control of summer precipitation in Taiwan. It is found that in years when summer precipitation in Taiwan is anomalously high, the western stretch of the NP high weakens. Weakening of the western stretch of the NP high induces strengthened southerly wind and enhanced vertical motion in East Asia and the western NP (EA–WNP) region, which is essentially an invigorated summer monsoon circulation. Corresponding to the invigorated circulation, precipitation increases in the southern section of the EA–WNP but decreases in the midlatitude section of the EA–WNP. It is further found that in those wet years, the land–sea temperature contrast between Asia and the surrounding seas is anomalously large and that the westerly wind in the tropical Indian Ocean and the southerly wind in the South China Sea and the subtropical East Asia are strengthened, which is an accelerated cyclonic circulation surrounding South and Southeast Asia. Coincident with the invigorated monsoon circulation in the EA–WNP region is a weakened Asian high pressure (Asian high). This is in variance with the expectation that the invigorated monsoon circulation in the EA–WNP region is related to a strengthened Asian high. The weakened Asian high is related to the weakened monsoon circulation in South and Southeast Asia. It is suggested that these unexpected results might be due to the interannual time scale of this study as opposed to either climatological or decadal scales of previous studies.

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15

Yokoyama, Chie, Edward J. Zipser, and Chuntao Liu. "TRMM-Observed Shallow versus Deep Convection in the Eastern Pacific Related to Large-Scale Circulations in Reanalysis Datasets." Journal of Climate 27, no. 14 (July 10, 2014): 5575–92. http://dx.doi.org/10.1175/jcli-d-13-00315.1.

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Abstract Over the eastern Pacific, recent studies have shown that a shallow large-scale meridional circulation with its return flow just above the boundary layer coexists with a deep Hadley circulation. This study examines how the vertical structure of large-scale circulations is related to satellite-observed individual precipitation properties over the eastern Pacific in boreal autumn. Three reanalysis datasets are used to describe differences in their behavior. The results are compared among reanalyses and three distinctly different convection periods, which are defined according to their radar echo depths. Shallow and deep circulations are shown to often coexist for each of the three periods, resulting in the multicell circulation structure. Deep (shallow) circulations preferentially appear in the mostly deep (shallow) convection period of radar echo depths. Thus, depth of convection basically corresponds to which circulation branch is dominant. This anticipated relationship between the circulation structure and depths of convection is common in all three reanalyses. Notable differences among reanalyses are found in the mid- to upper troposphere in either the time-mean state or the composite analysis based on the convection periods. Reanalyses have large variations in characteristics associated with deep circulations such as the upper-tropospheric divergence and outflows and the midlevel inflows, which are consistent with their different profiles of latent heating in the mid- to upper troposphere. On the other hand, discrepancies in shallow circulations and shallow convection are also found, but they are not as large as those in deep ones.

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16

Haidvogel, D. B., and G. Holloway. "Process Dynamics in Large-Scale Ocean-Circulation Modeling." Bulletin of the American Meteorological Society 68, no. 6 (June 1, 1987): 638–43. http://dx.doi.org/10.1175/1520-0477-68.6.638.

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17

Mantsis, Damianos F., Benjamin R. Lintner, Anthony J. Broccoli, Michael P. Erb, Amy C. Clement, and Hyo-Seok Park. "The Response of Large-Scale Circulation to Obliquity-Induced Changes in Meridional Heating Gradients." Journal of Climate 27, no. 14 (July 10, 2014): 5504–16. http://dx.doi.org/10.1175/jcli-d-13-00526.1.

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Abstract The inter- and intrahemispheric climate responses to a change in obliquity are investigated using the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1. (GFDL CM2.1). Reduced obliquity causes a weakening of the seasonal insolation contrast between the summer and winter hemispheres and a strengthening of the meridional insolation gradient within the summer hemisphere. The interhemispheric insolation change is associated with weakening of the cross-equatorial Hadley circulation and reduced heat transport from the summer hemisphere to the winter hemisphere, in both the ocean and atmosphere. In contrast, the intrahemispheric insolation change is associated with increased midlatitude summer eddy activity as seen by the increased atmospheric heat transport at those latitudes. Analysis of the zonal mean atmospheric meridional overturning circulation on isentropic surfaces confirms the increase of the midlatitude eddy circulation, which is driven by changes of sensible and latent heat fluxes, as well as changes in the stratification or distribution of entropy. It is suggested that the strengthening of this circulation is associated with an equatorward shift of the ascending branch of the winter Hadley cell.

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18

Kwon, Young-Oh, Michael A. Alexander, Nicholas A. Bond, Claude Frankignoul, Hisashi Nakamura, Bo Qiu, and Lu Anne Thompson. "Role of the Gulf Stream and Kuroshio–Oyashio Systems in Large-Scale Atmosphere–Ocean Interaction: A Review." Journal of Climate 23, no. 12 (June 15, 2010): 3249–81. http://dx.doi.org/10.1175/2010jcli3343.1.

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Abstract Ocean–atmosphere interaction over the Northern Hemisphere western boundary current (WBC) regions (i.e., the Gulf Stream, Kuroshio, Oyashio, and their extensions) is reviewed with an emphasis on their role in basin-scale climate variability. SST anomalies exhibit considerable variance on interannual to decadal time scales in these regions. Low-frequency SST variability is primarily driven by basin-scale wind stress curl variability via the oceanic Rossby wave adjustment of the gyre-scale circulation that modulates the latitude and strength of the WBC-related oceanic fronts. Rectification of the variability by mesoscale eddies, reemergence of the anomalies from the preceding winter, and tropical remote forcing also play important roles in driving and maintaining the low-frequency variability in these regions. In the Gulf Stream region, interaction with the deep western boundary current also likely influences the low-frequency variability. Surface heat fluxes damp the low-frequency SST anomalies over the WBC regions; thus, heat fluxes originate with heat anomalies in the ocean and have the potential to drive the overlying atmospheric circulation. While recent observational studies demonstrate a local atmospheric boundary layer response to WBC changes, the latter’s influence on the large-scale atmospheric circulation is still unclear. Nevertheless, heat and moisture fluxes from the WBCs into the atmosphere influence the mean state of the atmospheric circulation, including anchoring the latitude of the storm tracks to the WBCs. Furthermore, many climate models suggest that the large-scale atmospheric response to SST anomalies driven by ocean dynamics in WBC regions can be important in generating decadal climate variability. As a step toward bridging climate model results and observations, the degree of realism of the WBC in current climate model simulations is assessed. Finally, outstanding issues concerning ocean–atmosphere interaction in WBC regions and its impact on climate variability are discussed.

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19

Totz, Sonja, Stefan Petri, Jascha Lehmann, Erik Peukert, and Dim Coumou. "Exploring the sensitivity of Northern Hemisphere atmospheric circulation to different surface temperature forcing using a statistical–dynamical atmospheric model." Nonlinear Processes in Geophysics 26, no. 1 (February 18, 2019): 1–12. http://dx.doi.org/10.5194/npg-26-1-2019.

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Abstract. Climate and weather conditions in the mid-latitudes are strongly driven by the large-scale atmosphere circulation. Observational data indicate that important components of the large-scale circulation have changed in recent decades, including the strength and the width of the Hadley cell, jets, storm tracks and planetary waves. Here, we use a new statistical–dynamical atmosphere model (SDAM) to test the individual sensitivities of the large-scale atmospheric circulation to changes in the zonal temperature gradient, meridional temperature gradient and global-mean temperature. We analyze the Northern Hemisphere Hadley circulation, jet streams, storm tracks and planetary waves by systematically altering the zonal temperature asymmetry, the meridional temperature gradient and the global-mean temperature. Our results show that the strength of the Hadley cell, storm tracks and jet streams depend, in terms of relative changes, almost linearly on both the global-mean temperature and the meridional temperature gradient, whereas the zonal temperature asymmetry has little or no influence. The magnitude of planetary waves is affected by all three temperature components, as expected from theoretical dynamical considerations. The width of the Hadley cell behaves nonlinearly with respect to all three temperature components in the SDAM. Moreover, some of these observed large-scale atmospheric changes are expected from dynamical equations and are therefore an important part of model validation.

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Thompson, D. W. J., and E. A. Barnes. "Periodic Variability in the Large-Scale Southern Hemisphere Atmospheric Circulation." Science 343, no. 6171 (February 6, 2014): 641–45. http://dx.doi.org/10.1126/science.1247660.

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VASILEVSKAYA, L. N., I. A. LISINA, and D. N. VASILEVSKII. "INFLUENCE OF LARGE-SCALE ATMOSPHERIC PROCESSES ON SEASONAL RUNOFF OF LARGE SIBERIAN RIVERS." Meteorologiya i Gidrologiya, no. 10 (2021): 36–47. http://dx.doi.org/10.52002/0130-2906-2021-10-36-47.

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Based on daily runoff volumes of four large Siberian rivers (the Ob, Yenisei, Lena, and Kolyma) for 1936-2018, the regime and changes in the total annual and seasonal runoff are analyzed. High synchronous and asynchronous correlations between monthly river runoff and atmospheric circulation indices of hemispheric and regional scales are revealed. In recent decades, the total annual runoff and its variations have increased (the rate of increase is most pronounced for the Kolyma River). A change in water content within a year is heterogeneous: weak positive trends are characteristic of the spring flood runoff and the summer-autumn period, and a significant increase occurred in the winter months. High correlations with a 1-8-month shift made it possible to identify the most informative regions, the atmospheric circulation over which makes a certain contribution to the variance of river runoff.

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Juliano, Timothy W., and Zachary J. Lebo. "Linking large-scale circulation patterns to low-cloud properties." Atmospheric Chemistry and Physics 20, no. 12 (June 17, 2020): 7125–38. http://dx.doi.org/10.5194/acp-20-7125-2020.

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Abstract. The North Pacific High (NPH) is a fundamental meteorological feature present during the boreal warm season. Marine boundary layer (MBL) clouds, which are persistent in this oceanic region, are influenced directly by the NPH. In this study, we combine 11 years of reanalysis and an unsupervised machine learning technique to examine the gamut of 850 hPa synoptic-scale circulation patterns. This approach reveals two distinguishable regimes – a dominant NPH setup and a land-falling cyclone – and in between a spectrum of large-scale patterns. We then use satellite retrievals to elucidate for the first time the explicit dependence of MBL cloud properties (namely cloud droplet number concentration, liquid water path, and shortwave cloud radiative effect – CRESW) on 850 hPa circulation patterns over the northeast Pacific Ocean. We find that CRESW spans from −146.8 to −115.5 W m−2, indicating that the range of observed MBL cloud properties must be accounted for in global and regional climate models. Our results demonstrate the value of combining reanalysis and satellite retrievals to help clarify the relationship between synoptic-scale dynamics and cloud physics.

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Byrne, Michael P., and Tapio Schneider. "Atmospheric Dynamics Feedback: Concept, Simulations, and Climate Implications." Journal of Climate 31, no. 8 (March 26, 2018): 3249–64. http://dx.doi.org/10.1175/jcli-d-17-0470.1.

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AbstractThe regional climate response to radiative forcing is largely controlled by changes in the atmospheric circulation. It has been suggested that global climate sensitivity also depends on the circulation response, an effect called the “atmospheric dynamics feedback.” Using a technique to isolate the influence of changes in atmospheric circulation on top-of-the-atmosphere radiation, the authors calculate the atmospheric dynamics feedback in coupled climate models. Large-scale circulation changes contribute substantially to all-sky and cloud feedbacks in the tropics but are relatively less important at higher latitudes. Globally averaged, the atmospheric dynamics feedback is positive and amplifies the near-surface temperature response to climate change by an average of 8% in simulations with coupled models. A constraint related to the atmospheric mass budget results in the dynamics feedback being small on large scales relative to feedbacks associated with thermodynamic processes. Idealized-forcing simulations suggest that circulation changes at high latitudes are potentially more effective at influencing global temperature than circulation changes at low latitudes, and the implications for past and future climate change are discussed.

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Soden, Brian, and Eui-Seok Chung. "The Large-Scale Dynamical Response of Clouds to Aerosol Forcing." Journal of Climate 30, no. 21 (November 2017): 8783–94. http://dx.doi.org/10.1175/jcli-d-17-0050.1.

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Radiative kernels are used to quantify the instantaneous radiative forcing of aerosols and the aerosol-mediated cloud response in coupled ocean–atmosphere model simulations under both historical and future emission scenarios. The method is evaluated using matching pairs of historical climate change experiments with and without aerosol forcing and accurately captures the spatial pattern and global-mean effects of aerosol forcing. It is shown that aerosol-driven changes in the atmospheric circulation induce additional cloud changes. Thus, the total aerosol-mediated cloud response consists of both local microphysical changes and nonlocal dynamical changes that are driven by hemispheric asymmetries in aerosol forcing. By comparing coupled and fixed sea surface temperature (SST) simulations with identical aerosol forcing, the relative contributions of these two components are isolated, exploiting the ability of prescribed SSTs to also suppress changes in the atmospheric circulation. The radiative impact of the dynamical cloud changes is found to be comparable in magnitude to that of the microphysical cloud changes and acts to further amplify the interhemispheric asymmetry of the aerosol radiative forcing. The dynamical cloud response is closely linked to the meridional displacement of the Hadley cell, which, in turn, is driven by changes in the cross-equatorial energy transport. In this way, the dynamical cloud changes act as a positive feedback on the meridional displacement of the Hadley cell, roughly doubling the projected changes in cross-equatorial energy transport compared to that from the microphysical changes alone.

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Kamieniecki, Jan A., Maarten H. P. Ambaum, Robert S. Plant, and Steven J. Woolnough. "The Implications of an Idealized Large-Scale Circulation for Mechanical Work Done by Tropical Convection." Journal of the Atmospheric Sciences 75, no. 8 (July 13, 2018): 2533–47. http://dx.doi.org/10.1175/jas-d-17-0314.1.

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Abstract A thermodynamic analysis is presented of an overturning circulation simulated by two cloud-resolving models, coupled by a weak temperature gradient parameterization. Taken together, they represent two separated regions over different sea surface temperatures, and the coupling represents an idealized large-scale circulation such as the Walker circulation. It is demonstrated that a thermodynamic budget linking net heat input to the generation of mechanical energy can be partitioned into contributions from the large-scale interaction between the two regions, as represented by the weak temperature gradient approximation, and from convective motions in the active warm region and the suppressed cool region. Model results imply that such thermodynamic diagnostics for the aggregate system are barely affected by the strength of the coupling, even its introduction, or by the SST contrast between the regions. This indicates that the weak temperature gradient parameterization does not introduce anomalous thermodynamic behavior. We find that the vertical kinetic energy associated with the large-scale circulation is more than three orders of magnitude smaller than the typical vertical kinetic energy in each region. However, even with very weak coupling circulations, the contrast between the thermodynamic budget terms for the suppressed and active regions is strong and is relatively insensitive to the degree of the coupling. Additionally, scaling arguments are developed for the relative values of the terms in the mechanical energy budget.

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Armour, Kyle C., Nicholas Siler, Aaron Donohoe, and Gerard H. Roe. "Meridional Atmospheric Heat Transport Constrained by Energetics and Mediated by Large-Scale Diffusion." Journal of Climate 32, no. 12 (May 28, 2019): 3655–80. http://dx.doi.org/10.1175/jcli-d-18-0563.1.

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Abstract Meridional atmospheric heat transport (AHT) has been investigated through three broad perspectives: a dynamic perspective, linking AHT to the poleward flux of moist static energy (MSE) by atmospheric motions; an energetic perspective, linking AHT to energy input to the atmosphere by top-of-atmosphere radiation and surface heat fluxes; and a diffusive perspective, representing AHT in terms downgradient energy transport. It is shown here that the three perspectives provide complementary diagnostics of meridional AHT and its changes under greenhouse gas forcing. When combined, the energetic and diffusive perspectives offer prognostic insights: anomalous AHT is constrained to satisfy the net energetic demands of radiative forcing, radiative feedbacks, and ocean heat uptake; in turn, the meridional pattern of warming must adjust to produce those AHT changes, and does so approximately according to diffusion of anomalous MSE. The relationship between temperature and MSE exerts strong constraints on the warming pattern, favoring polar amplification. These conclusions are supported by use of a diffusive moist energy balance model (EBM) that accurately predicts zonal-mean warming and AHT changes within comprehensive general circulation models (GCMs). A dry diffusive EBM predicts similar AHT changes in order to satisfy the same energetic constraints, but does so through tropically amplified warming—at odds with the GCMs’ polar-amplified warming pattern. The results suggest that polar-amplified warming is a near-inevitable consequence of a moist, diffusive atmosphere’s response to greenhouse gas forcing. In this view, atmospheric circulations must act to satisfy net AHT as constrained by energetics.

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Widmann, M., JM Jones, and H. Von Storch. "Reconstruction of Large-Scale Atmospheric Circulation and Data Assimilation in Paleoclimatology." PAGES news 12, no. 2 (October 2004): 12–13. http://dx.doi.org/10.22498/pages.12.2.12.

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Bradbury, James A., S. Lawrence Dingman, and Barry D. Keim. "NEW ENGLAND DROUGHT AND RELATIONS WITH LARGE SCALE ATMOSPHERIC CIRCULATION PATTERNS1." JAWRA Journal of the American Water Resources Association 38, no. 5 (October 2002): 1287–99. http://dx.doi.org/10.1111/j.1752-1688.2002.tb04348.x.

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Raphael, Marilyn. "Recent, Large-Scale Changes in the Extratropical Southern Hemisphere Atmospheric Circulation." Journal of Climate 16, no. 17 (September 2003): 2915–24. http://dx.doi.org/10.1175/1520-0442(2003)016<2915:rlcite>2.0.co;2.

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Colucci, Stephen J. "Explosive Cyclogenesis and Large-Scale Circulation Changes: Implications for Atmospheric Blocking." Journal of the Atmospheric Sciences 42, no. 24 (December 1985): 2701–17. http://dx.doi.org/10.1175/1520-0469(1985)042<2701:ecalsc>2.0.co;2.

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31

Birsan, Marius-Victor, and Alexandru Dumitrescu. "Snow variability in Romania in connection to large-scale atmospheric circulation." International Journal of Climatology 34, no. 1 (February 21, 2013): 134–44. http://dx.doi.org/10.1002/joc.3671.

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32

Ceglar, Andrej, Marco Turco, Andrea Toreti, and Francisco J. Doblas-Reyes. "Linking crop yield anomalies to large-scale atmospheric circulation in Europe." Agricultural and Forest Meteorology 240-241 (June 2017): 35–45. http://dx.doi.org/10.1016/j.agrformet.2017.03.019.

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33

Bothe, Oliver, Klaus Fraedrich, and Xiuhua Zhu. "Precipitation climate of Central Asia and the large-scale atmospheric circulation." Theoretical and Applied Climatology 108, no. 3-4 (October 8, 2011): 345–54. http://dx.doi.org/10.1007/s00704-011-0537-2.

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34

Seim, Andrea, Johannes A. Schultz, Christoph Beck, Achim Bräuning, Paul J. Krusic, Caroline Leland, Oyunsanaa Byambasuren, et al. "Evaluation of Tree Growth Relevant Atmospheric Circulation Patterns for Geopotential Height Field Reconstructions for Asia." Journal of Climate 31, no. 11 (June 2018): 4391–401. http://dx.doi.org/10.1175/jcli-d-17-0164.1.

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Atmospheric circulations influence local and regional weather conditions and, thus, tree growth. To identify summer weather types relevant for tree growth, and their associated synoptic-scale circulation patterns, an atmospheric circulation tree ring index (ACTI) dataset, derived from 414 tree-ring sites across Asia spanning the period 1871–2010, was created. Modes of common variability in the ACTI dataset were compared with leading modes of observed summertime 500-hPa geopotential height. The first four ACTI modes (explaining 88% of the total variance) were associated with pressure centers over Eurasia, the tropics, and the Pacific Ocean. The high spatiotemporal resemblance between the leading circulation modes, derived from both tree rings and 500-hPa geopotential height fields, indicates a strong potential for reconstructing large-scale circulation patterns from tree rings in Asia. This would allow investigations of natural atmospheric circulation variability prior to anthropogenic climate change and provide a means to validate model simulations of climate predictions.

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Tomozeiu, R., S. Stefan, and A. Busuioc. "Winter precipitation variability and large-scale circulation patterns in Romania." Theoretical and Applied Climatology 81, no. 3-4 (February 22, 2005): 193–201. http://dx.doi.org/10.1007/s00704-004-0082-3.

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Blanc, Antoine, Juliette Blanchet, and Jean-Dominique Creutin. "Past evolution of western Europe large-scale circulation and link to precipitation trend in the northern French Alps." Weather and Climate Dynamics 3, no. 1 (March 1, 2022): 231–50. http://dx.doi.org/10.5194/wcd-3-231-2022.

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Abstract. Detecting trends in regional large-scale circulation (LSC) is an important challenge as LSC is a key driver of local weather conditions. In this work, we investigate the past evolution of western Europe LSC based on the 500 hPa geopotential height fields from 20CRv2c (1851–2010), ERA20C (1900–2010) and ERA5 (1950–2010) reanalyses. We focus on the evolution of large-scale circulation characteristics using three atmospheric descriptors that are based on analogy by comparing daily geopotential height fields to each other. They characterize the stationarity of geopotential shape and how well a geopotential shape is reproduced in the climatology. A non-analogy descriptor is also employed to account for the intensity of the centers of action. We then combine the four atmospheric descriptors with an existing weather pattern classification over the period 1950–2019 to study the recent changes in the two main atmospheric influences driving precipitation in the northern French Alps. They correspond to the Atlantic circulation pattern dominated by a zonal flow and the Mediterranean circulation pattern dominated by low-pressure anomalies over the near Atlantic, close to Portugal. Even though LSC characteristics and trends are consistent among the three reanalyses after 1950, we find major differences between 20CRv2c and ERA20C from 1900 to 1950 in accordance with previous studies. Notably, ERA20C produces flatter geopotential shapes in the beginning of the 20th century and shows a reinforcement of the meridional pressure gradient that is not observed in 20CRv2c. Over the period 1950–2019, we show that winter Atlantic circulations (zonal flows) tend to be shifted northward, and they become more similar to known Atlantic circulations. Mediterranean circulations tend to become more stationary, more similar to known Mediterranean circulations and associated with stronger centers of action in autumn, while an opposite behavior is observed in winter. Finally, we discuss the role of these LSC changes for seasonal and extreme precipitation in the northern French Alps. We show that these changes in LSC characteristics are linked to (a) the decreasing contribution of Mediterranean circulations to winter precipitation and (b) more circulations that are likely to generate extreme precipitation in autumn.

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Agel, Laurie, Vianney Lopez, Mathew Barlow, and Frank Colby. "Regional and Large-Scale Influences on Summer Ozone Levels in Southern California." Journal of Applied Meteorology and Climatology 50, no. 4 (April 2011): 800–805. http://dx.doi.org/10.1175/2010jamc2605.1.

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AbstractThe links between daily ozone levels in Southern California and atmospheric circulation at regional and large scales are examined for July–September 1994–2001. The monitoring station in Pasadena is used as the primary basis for ozone analysis; comparison with other stations validates its representativeness for Southern California. Comparing the 10% of highest-ozone days with the 10% of lowest-ozone days for Pasadena reveals a large regional difference in 700-hPa vertical velocity over Southern California, consistent with changes to the ventilation and depth of the boundary layer. Analysis of the associated changes in midlevel (500 hPa) circulation reveals near-continental-scale differences, with very large modifications in the strength and position of the North American anticyclone. These links between daily ozone levels and regional and large-scale atmospheric circulation features suggest the potential for using currently available medium-range weather forecasts in ozone prediction.

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Tromeur, Eric, and William B. Rossow. "Interaction of Tropical Deep Convection with the Large-Scale Circulation in the MJO." Journal of Climate 23, no. 7 (April 1, 2010): 1837–53. http://dx.doi.org/10.1175/2009jcli3240.1.

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Abstract To better understand the interaction between tropical deep convection and the Madden–Julian oscillation (MJO), tropical cloud regimes are defined by cluster analysis of International Satellite Cloud Climatology Project (ISCCP) cloud-top pressure—optical thickness joint distributions from the D1 dataset covering 21.5 yr. An MJO index based solely on upper-level wind anomalies is used to study variations of the tropical cloud regimes. The MJO index shows that MJO events are present almost all the time; instead of the MJO event being associated with “on or off” deep convection, it is associated with weaker or stronger mesoscale organization of deep convection. Atmospheric winds and humidity from NCEP–NCAR reanalysis 1 are used to characterize the large-scale dynamics of the MJO; the results show that the large-scale motions initiate an MJO event by moistening the lower troposphere by horizontal advection. Increasingly strong convection transports moisture into the upper troposphere, suggesting a reinforcement of the convection itself. The change of convection organization shown by the cloud regimes indicates a strong interaction between the large-scale circulation and deep convection. The analysis is extended to the complete atmospheric diabatic heating by precipitation, radiation, and surface fluxes. The wave organizes stronger convective heating of the tropical atmosphere, which results in stronger winds, while there is only a passive response of the surface, directly linked to cloud radiative effects. Overall, the results suggest that an MJO event is an amplification of large-scale wave motions by stronger convective heating, which results from a dynamic reorganization of scattered deep convection into more intense mesoscale systems.

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Guillot, Tristan. "Atmospheric Circulation of Hot Jupiters." Symposium - International Astronomical Union 202 (2004): 261–68. http://dx.doi.org/10.1017/s0074180900218032.

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About 40% of the extrasolar giant planets discovered so far have orbital distances smaller than 0.2 AU. These “hot Jupiters” are expected to be in synchronous rotation with their star. The ability to measure their radii prompts a careful reexamination of their structure. I show that their atmospheric structure is complex and that thermal balance cannot be achieved through radiation only but must involve heat advection by large-scale circulation. A circulation model inspired from Venus is proposed, involving a relatively strong zonal wind (with a period that can be as short as 1 day). It is shown that even this strong wind is incapable of efficiently redistributing heat from the day side to the night side. Temperature variations of 200 K or more are to be expected, even at pressures as large as 10 bar. As a consequence, clouds should be absent on the day side, allowing more efficient absorption of the stellar light. The global chemical composition of the atmosphere should also be greatly affected by the presence of large temperature variations. Finally, stellar tides may also be important in their ability to deposit heat at levels untouched by stellar radiation, thereby slowing further the cooling of the planets.

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Arakane, Sho, and Huang-Hsiung Hsu. "Tropical Cyclone Footprints in Long-Term Mean State and Multiscale Climate Variability in the Western North Pacific as Seen in the JRA-55 Reanalysis." Journal of Climate 34, no. 18 (September 2021): 7443–60. http://dx.doi.org/10.1175/jcli-d-20-0887.1.

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AbstractThe monsoon trough and subtropical high have long been acknowledged to exert a substantial modulating effect on the genesis and development of tropical cyclones (TCs) in the western North Pacific (WNP). However, the potential upscaling effect of TCs on large-scale circulation remains poorly understood. This study revealed the considerable contributions of TCs to the climate mean state and variability in the WNP between 1958 and 2019, characterized by a strengthened monsoon trough and weakened subtropical anticyclonic circulation in the lower troposphere, enhanced anticyclonic circulation in the upper troposphere, and warming throughout the troposphere. TCs constituted distinct footprints in the long-term mean states of the WNP summer monsoon, and their contributions increased intraseasonal and interannual variance by 50%–70%. The interdecadal variations and long-term trends in intraseasonal variance were mainly due to the year-to-year fluctuations in TC activity. The size of TC footprints was positively correlated with the magnitude of TC activity. Our findings suggest that the full understanding of climate variability and changes cannot be achieved simply on the basis of low-frequency, large-scale circulations. Rather, TCs must be regarded as a crucial component in the climate system, and their interactions with large-scale circulations require thorough exploration. The long-term dataset created in this study provides an opportunity to study the interaction between TCs and TC-free large-scale circulations to advance our understanding of climate variability in the WNP. Our findings also indicate that realistic climate projections must involve the accurate simulations of TCs.

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Han, Zixuan, Qiong Zhang, Qiang Li, Ran Feng, Alan M. Haywood, Julia C. Tindall, Stephen J. Hunter, et al. "Evaluating the large-scale hydrological cycle response within the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble." Climate of the Past 17, no. 6 (December 8, 2021): 2537–58. http://dx.doi.org/10.5194/cp-17-2537-2021.

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Abstract. The mid-Pliocene (∼3 Ma) is one of the most recent warm periods with high CO2 concentrations in the atmosphere and resulting high temperatures, and it is often cited as an analog for near-term future climate change. Here, we apply a moisture budget analysis to investigate the response of the large-scale hydrological cycle at low latitudes within a 13-model ensemble from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). The results show that increased atmospheric moisture content within the mid-Pliocene ensemble (due to the thermodynamic effect) results in wetter conditions over the deep tropics, i.e., the Pacific intertropical convergence zone (ITCZ) and the Maritime Continent, and drier conditions over the subtropics. Note that the dynamic effect plays a more important role than the thermodynamic effect in regional precipitation minus evaporation (PmE) changes (i.e., northward ITCZ shift and wetter northern Indian Ocean). The thermodynamic effect is offset to some extent by a dynamic effect involving a northward shift of the Hadley circulation that dries the deep tropics and moistens the subtropics in the Northern Hemisphere (i.e., the subtropical Pacific). From the perspective of Earth's energy budget, the enhanced southward cross-equatorial atmospheric transport (0.22 PW), induced by the hemispheric asymmetries of the atmospheric energy, favors an approximately 1∘ northward shift of the ITCZ. The shift of the ITCZ reorganizes atmospheric circulation, favoring a northward shift of the Hadley circulation. In addition, the Walker circulation consistently shifts westward within PlioMIP2 models, leading to wetter conditions over the northern Indian Ocean. The PlioMIP2 ensemble highlights that an imbalance of interhemispheric atmospheric energy during the mid-Pliocene could have led to changes in the dynamic effect, offsetting the thermodynamic effect and, hence, altering mid-Pliocene hydroclimate.

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Smith, Robin S., Clotilde Dubois, and Jochem Marotzke. "Global Climate and Ocean Circulation on an Aquaplanet Ocean–Atmosphere General Circulation Model." Journal of Climate 19, no. 18 (September 15, 2006): 4719–37. http://dx.doi.org/10.1175/jcli3874.1.

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Abstract A low-resolution coupled ocean–atmosphere general circulation model (OAGCM) is used to study the characteristics of the large-scale ocean circulation and its climatic impacts in a series of global coupled aquaplanet experiments. Three configurations, designed to produce fundamentally different ocean circulation regimes, are considered. The first has no obstruction to zonal flow, the second contains a low barrier that blocks zonal flow in the ocean at all latitudes, creating a single enclosed basin, while the third contains a gap in the barrier to allow circumglobal flow at high southern latitudes. Warm greenhouse climates with a global average air surface temperature of around 27°C result in all cases. Equator-to-pole temperature gradients are shallower than that of a current climate simulation. While changes in the land configuration cause regional changes in temperature, winds, and rainfall, heat transports within the system are little affected. Inhibition of all ocean transport on the aquaplanet leads to a reduction in global mean surface temperature of 8°C, along with a sharpening of the meridional temperature gradient. This results from a reduction in global atmospheric water vapor content and an increase in tropical albedo, both of which act to reduce global surface temperatures. Fitting a simple radiative model to the atmospheric characteristics of the OAGCM solutions suggests that a simpler atmosphere model, with radiative parameters chosen a priori based on the changing surface configuration, would have produced qualitatively different results. This implies that studies with reduced complexity atmospheres need to be guided by more complex OAGCM results on a case-by-case basis.

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Maity, Rajib, and D. Nagesh Kumar. "Basin-scale stream-flow forecasting using the information of large-scale atmospheric circulation phenomena." Hydrological Processes 22, no. 5 (2008): 643–50. http://dx.doi.org/10.1002/hyp.6630.

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Peng, Shiqiu, Lian Xie, Bin Liu, and Fredrick Semazzi. "Application of Scale-Selective Data Assimilation to Regional Climate Modeling and Prediction." Monthly Weather Review 138, no. 4 (April 1, 2010): 1307–18. http://dx.doi.org/10.1175/2009mwr2974.1.

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Abstract A method referred to as scale-selective data assimilation (SSDA) is designed to inject the large-scale components of the atmospheric circulation from a global model into a regional model to improve regional climate simulations and predictions. The SSDA is implemented through the following procedure: 1) using a low-pass filter to extract the large-scale components of the atmospheric circulation from global analysis or model forecasts; 2) applying the filter to extract the regional-scale and the large-scale components of the atmospheric circulation from the regional model simulations or forecasts; 3) assimilating the large-scale circulation obtained from the global model into the corresponding component simulated by the regional model using the method of three-dimensional variational data assimilation (3DVAR) while maintaining the small-scale components from the regional model during the assimilation cycle; 4) combining the small-scale and the assimilated large-scale components as the adjusted forecasts by the regional climate model and allowing the two components to mutually adjust outside the data assimilation cycle. A case study of summer 2005 seasonal climate hindcasting for the regions of the Atlantic and the eastern United States indicates that the large-scale components from the Global Forecast System (GFS) analysis can be effectively assimilated into the regional model using the scale-selective data assimilation method devised in this study, resulting in an improvement in the overall results from the regional climate model.

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Maslowski, W., D. C. Marble, W. Walczowski, and A. J. Semtner. "On large-scale shifts in the Arctic Ocean and sea-ice conditions during 1979−98." Annals of Glaciology 33 (2001): 545–50. http://dx.doi.org/10.3189/172756401781818978.

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AbstractResults from a regional model of the Arctic Ocean and sea ice forced with realistic atmospheric data are analyzed to understand recent climate variability in the region. The primary simulation uses daily-averaged 1979 atmospheric fields repeated for 20 years and then continues with interannual forcing derived from the European Centre for Medium-range Weather Forecasts for 1979−98. An eastward shift in the ice-ocean circulation, fresh-water distribution and Atlantic Water extent has been determined by comparing conditions between the early 1980s and 1990s. A new trend is modeled in the late 1990s, and has a tendency to return the large-scale sea-ice and upper ocean conditions to their state in the early 1980s. Both the sea-ice and the upper ocean circulation as well as fresh-water export from the Russian shelves and Atlantic Water recirculation within the Eurasian Basin indicate that the Arctic climate is undergoing another shift. This suggests an oscillatory behavior of the Arctic Ocean system. Interannual atmospheric variability appears to be the main and sufficient driver of simulated changes. The ice cover acts as an effective dynamic medium for vorticity transfer from the atmosphere into the ocean.

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Stan, Cristiana, and David M. Straus. "Is Blocking a Circulation Regime?" Monthly Weather Review 135, no. 6 (June 1, 2007): 2406–13. http://dx.doi.org/10.1175/mwr3410.1.

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Abstract The relationship between Pacific blocking and large-scale circulation regimes is investigated. The large-scale circulation regimes are obtained by cluster analysis using the k-means method and tested against significance and reproducibility. Pacific blocking is described using two different methods. In a direct approach, blocking is described by a recently developed blocking index, which is defined in terms of potential temperature anomaly on a surface of constant potential vorticity. In an indirect approach, the occurrence of extreme events is used as a proxy for blockings. Between the two methods there is a causal relationship; the direct one is an indication of the occurrence of the blocking, while the indirect one is a measure of some of the effects caused by the blocking. The results indicate that large-scale circulation regimes are related to but not necessarily tightly coupled to blocking and weather extremes in the Pacific–North America region.

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Wang, Yuqing, Shang-Ping Xie, Bin Wang, and Haiming Xu. "Large-Scale Atmospheric Forcing by Southeast Pacific Boundary Layer Clouds: A Regional Model Study*." Journal of Climate 18, no. 7 (April 1, 2005): 934–51. http://dx.doi.org/10.1175/jcli3302.1.

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Abstract A regional model is used to study the radiative effect of boundary layer clouds over the southeast Pacific on large-scale atmosphere circulation during August–October 1999. With the standard settings, the model simulates reasonably well the large-scale circulation over the eastern Pacific, precipitation in the intertropical convergence zone (ITCZ) north of the equator, and marine boundary layer stratocumulus clouds to the south. In a sensitivity experiment with the radiative effect of liquid clouds south of the equator over the eastern Pacific artificially removed, boundary layer clouds south of the equator almost disappear and precipitation in the ITCZ is reduced by 15%–20%, indicating that the stratocumulus clouds over the southeast Pacific have both local and cross-equatorial effects. Examination of the differences between the control and sensitivity experiments indicates that clouds exert a net diabatic cooling in the inversion layer. In response to this cloud-induced cooling, an in situ anomalous high pressure system develops in the boundary layer and an anomalous shallow meridional circulation develops in the lower troposphere over the equatorial eastern Pacific. At the lower branch of this shallow circulation, anomalous boundary layer southerlies blow from the boundary layer high toward the northern ITCZ where the air ascends. An anomalous returning flow (northerly) just above the cloud layer closes the shallow circulation. This low-level anomalous shallow circulation enhances the subsidence over the southeast Pacific above the cloud layer, helping to maintain boundary layer clouds and temperature inversion there. Meanwhile, the strengthened cross-equatorial flow near the surface enhances moisture convergence and convection in the ITCZ north of the equator. This in turn strengthens the local, deep Hadley circulation and hence the large-scale subsidence and boundary layer clouds over the southeast Pacific. This positive feedback therefore enhances the interhemispheric climate asymmetry over the tropical eastern Pacific.

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Hsia, Chun-Hsiung, Chang-Shou Lin, Tian Ma, and Shouhong Wang. "Tropical atmospheric circulations with humidity effects." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, no. 2173 (January 2015): 20140353. http://dx.doi.org/10.1098/rspa.2014.0353.

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The main objective of this article is to study the effect of the moisture on the planetary scale atmospheric circulation over the tropics. The modelling we adopt is the Boussinesq equations coupled with a diffusive equation of humidity, and the humidity-dependent heat source is modelled by a linear approximation of the humidity. The rigorous mathematical analysis is carried out using the dynamic transition theory. In particular, we obtain mixed transitions, also known as random transitions, as described in Ma & Wang (2010 Discrete Contin. Dyn. Syst. 26 , 1399–1417. ( doi:10.3934/dcds.2010.26.1399 ); 2011 Adv. Atmos. Sci. 28 , 612–622. ( doi:10.1007/s00376-010-9089-0 )). The analysis also indicates the need to include turbulent friction terms in the model to obtain correct convection scales for the large-scale tropical atmospheric circulations, leading in particular to the right critical temperature gradient and the length scale for the Walker circulation. In short, the analysis shows that the effect of moisture lowers the magnitude of the critical thermal Rayleigh number and does not change the essential characteristics of dynamical behaviour of the system.

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Li, Ying, David W. J. Thompson, and Yi Huang. "The Influence of Atmospheric Cloud Radiative Effects on the Large-Scale Stratospheric Circulation." Journal of Climate 30, no. 15 (August 2017): 5621–35. http://dx.doi.org/10.1175/jcli-d-16-0643.1.

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Previous studies have explored the influence of atmospheric cloud radiative effects (ACRE) on the tropospheric circulation. Here the authors explore the influence of ACRE on the stratospheric circulation. The response of the stratospheric circulation to ACRE is assessed by comparing simulations run with and without ACRE. The stratospheric circulation response to ACRE is reproducible in a range of different GCMs and can be interpreted in the context of both a dynamically driven and a radiatively driven component. The dynamic component is linked to ACRE-induced changes in the vertical and meridional fluxes of wave activity. The ACRE-induced changes in the vertical flux of wave activity into the stratosphere are consistent with the ACRE-induced changes in tropospheric baroclinicity and thus the amplitude of midlatitude baroclinic eddies. They account for a strengthening of the Brewer–Dobson circulation, a cooling of the tropical lower stratosphere, a weakening and warming of the polar vortex, a reduction of static stability near the tropical tropopause transition layer, and a shortening of the time scale of extratropical stratospheric variability. The ACRE-induced changes in the equatorward flux of wave activity in the low-latitude stratosphere account for a strengthening of the zonal wind in the subtropical lower to midstratosphere. The radiative component is linked to ACRE-induced changes in the flux of longwave radiation into the lower stratosphere. The changes in radiative fluxes lead to a cooling of the extratropical lower stratosphere, changes in the static stability and cloud fraction near the extratropical tropopause, and a shortening of the time scales of extratropical stratospheric variability. The results highlight a previously overlooked pathway through which tropospheric climate influences the stratosphere.

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Gottschalck, Jon, Paul E. Roundy, Carl J. Schreck III, Augustin Vintzileos, and Chidong Zhang. "Large-Scale Atmospheric and Oceanic Conditions during the 2011–12 DYNAMO Field Campaign." Monthly Weather Review 141, no. 12 (November 25, 2013): 4173–96. http://dx.doi.org/10.1175/mwr-d-13-00022.1.

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Abstract An international field campaign, Dynamics of the Madden Julian Oscillation (DYNAMO), took place in the Indian Ocean during October 2011–March 2012 to collect observations for the Madden–Julian oscillation (MJO), especially its convective initiation processes. The large-scale atmospheric and oceanic conditions during the campaign are documented here. The ENSO and the Indian Ocean dipole (IOD) states, the monthly mean monsoon circulation and its associated precipitation, humidity, vertical and meridional/zonal overturning cells, and ocean surface currents are discussed. The evolution of MJO events is described using various fields and indices that have been used to subdivide the campaign into three periods. These periods were 1) 17 September–8 December 2011 (period 1), which featured two robust MJO events that circumnavigated the global tropics with a period of less than 45 days; 2) 9 December 2011–31 January 2012, which contained less coherent activity (period 2); and 3) 1 February–12 April 2012, a period that featured the strongest and most slowly propagating MJO event of the campaign (period 3). Activities of convectively coupled atmospheric Kelvin and equatorial Rossby (ER) waves and their interaction with the MJO are discussed. The overview of the atmospheric and oceanic variability during the field campaign raises several scientific issues pertaining to our understanding of the MJO, or lack thereof. Among others, roles of Kelvin and ER waves in MJO convective initiation, convection-circulation decoupling on the MJO scale, applications of MJO filtering methods and indices, and ocean–atmosphere coupling need further research attention.

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Journal articles on the topic 'Large-scale atmospheric circulation'

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