Simulating the impact of the large-scale circulation on the 2-m temperature and precipitation climatology

This study aims to explore the contrasting characteristics of large-scale circulation that led to the precipitation anomalies over the northern parts of Sumatra Island. Further, the impact of varying the Asian–Australian Monsoon (AAM) was investigated for triggering the precipitation variability over the study area. The moisture budget analysis was applied to quantify the most dominant component that induces precipitation variability during the JJA (June, July, and August) period. Then, the composite analysis and statistical approach were applied to confirm the result of the moisture budget. Using the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Anaysis Interim (ERA-Interim) from 1981 to 2016, we identified 9 (nine) dry and 6 (six) wet years based on precipitation anomalies, respectively. The dry years (wet years) anomalies over the study area were mostly supported by downward (upward) vertical velocity anomaly instead of other variables such as specific humidity, horizontal velocity, and evaporation. In the dry years (wet years), there is a strengthening (weakening) of the descent motion, which triggers a reduction (increase) of convection over the study area. The overall downward (upward) motion of westerly (easterly) winds appears to suppress (support) the convection and lead to negative (positive) precipitation anomaly in the whole region but with the largest anomaly over northern parts of Sumatra. The AAM variability proven has a significant role in the precipitation variability over the study area. A teleconnection between the AAM and other global circulations implies the precipitation variability over the northern part of Sumatra Island as a regional phenomenon. The large-scale tropical circulation is possibly related to the PWC modulation (Pacific Walker Circulation).

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Impacts of Large-Scale Circulation on Urban Ambient Concentrations of Gaseous Elemental Mercury in New York, USA

10.5194/acp-2017-176 ◽

2017 ◽

Cited By ~ 1

Author(s):

Huiting Mao ◽

Dolly Hall ◽

Zhuyun Ye ◽

Ying Zhou ◽

Dirk Felton ◽

...

Keyword(s):

New York ◽

North American ◽

Large Scale ◽

Measurement Data ◽

Elemental Mercury ◽

Urban Site ◽

Large Scale Circulation ◽

Gaseous Elemental Mercury ◽

The North ◽

The Impact

Abstract. The impact of large-scale circulation on urban gaseous elemental mercury (GEM) was investigated through analysis of 2008–2015 measurement data from an urban site in New York City (NYC), New York, USA. Distinct annual cycles were observed in 2009–2010 with mixing ratios in warm seasons (i.e. spring–summer) 10–20 ppqv (~ 10 %–25 %) higher than in cool seasons (i.e. fall–winter). This annual cycle was disrupted in 2011 by an anomalously strong influence of the North American trough in that warm season and was reproduced in 2014 with annual amplitude enhanced up to ~ 70 ppqv associated with a particularly strong Bermuda High. North American trough axis index (TAI) and intensity index (TII) were used to characterize the effect of the North American trough on NYC GEM especially in winter and summer. The intensity and position of the Bermuda High had a significant impact on GEM in warm seasons supported by a strong correlation (r reaching 0.96, p

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Combined measurement of velocity and temperature in liquid metal convection

Journal of Fluid Mechanics ◽

10.1017/jfm.2019.556 ◽

2019 ◽

Vol 876 ◽

pp. 1108-1128 ◽

Cited By ~ 11

Author(s):

Till Zürner ◽

Felix Schindler ◽

Tobias Vogt ◽

Sven Eckert ◽

Jörg Schumacher

Keyword(s):

Reynolds Number ◽

Liquid Metal ◽

Large Scale ◽

Scale Up ◽

Convection Cell ◽

Small Scale ◽

Convection Flow ◽

Large Scale Circulation ◽

Large Scale Flow ◽

The Impact

Combined measurements of velocity components and temperature in a turbulent Rayleigh–Bénard convection flow at a low Prandtl number of $Pr=0.029$ and Rayleigh numbers of $10^{6}\leqslant Ra\leqslant 6\times 10^{7}$ are conducted in a series of experiments with durations of more than a thousand free-fall time units. Multiple crossing ultrasound beam lines and an array of thermocouples at mid-height allow for a detailed analysis and characterization of the complex three-dimensional dynamics of the single large-scale circulation roll in a cylindrical convection cell of unit aspect ratio which is filled with the liquid metal alloy GaInSn. We measure the internal temporal correlations of the complex large-scale flow and distinguish between short-term oscillations associated with a sloshing motion in the mid-plane as well as varying orientation angles of the velocity close to the top/bottom plates and the slow azimuthal drift of the mean orientation of the roll as a whole that proceeds on a time scale up to a hundred times slower. The coherent large-scale circulation drives a vigorous turbulence in the whole cell that is quantified by direct Reynolds number measurements at different locations in the cell. The velocity increment statistics in the bulk of the cell displays characteristic properties of intermittent small-scale fluid turbulence. We also show that the impact of the symmetry-breaking large-scale flow persists to small-scale velocity fluctuations thus preventing the establishment of fully isotropic turbulence in the cell centre. Reynolds number amplitudes depend sensitively on beam-line position in the cell such that different definitions have to be compared. The global momentum and heat transfer scalings with Rayleigh number are found to agree with those of direct numerical simulations and other laboratory experiments.

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Pacific Decadal Oscillation and recent oxygen decline in the eastern tropical Pacific Ocean

10.5194/bg-2018-16 ◽

2018 ◽

Cited By ~ 2

Author(s):

Olaf Duteil ◽

Andreas Oschlies ◽

Claus W. Böning

Keyword(s):

Pacific Ocean ◽

Pacific Decadal Oscillation ◽

Large Scale ◽

Eastern Pacific ◽

Positive Phase ◽

Biogeochemical Model ◽

Eastern Pacific Ocean ◽

Large Scale Circulation ◽

Diffusive Processes ◽

The Impact

Abstract. The impact of the positive and negative phases of the Pacific Decadal Oscillation (PDO) on the extension of the poorly oxygenated regions of the eastern Pacific ocean has been assessed using a coupled ocean circulation-biogeochemical model. We show that during a typical PDO positive phase the volume of the suboxic regions expands by 7 % in 50 years due to a slow-down of the large scale circulation related with the decrease of the intensity of the trade winds. The oxygen levels are mostly constrained by advective processes between 10° N and 10° S while the diffusive processes are dominant poleward of 10°: in a typical PDO positive phase the sluggish equatorial current system provides less oxygen into the eastern equatorial part of the basin while the oxygen transport by diffusive processes significantly decreases south of 10° S. The region located north of 10° N displays less sensitivity to the phase of the PDO as the local upwelling-related processes play a dominant role compared to the large scale circulation in setting the oxygen concentration. Our study suggests that the prevailing PDO positive conditions since 1975 may explain a significant part of the current deoxygenation occurring in the eastern Pacific Ocean.

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Is Diminishing Solar Activity Detrimental to Canadian Prairie Agriculture?

Earth & Environmental Science Research & Reviews ◽

10.33140/eesrr.03.03.13 ◽

2020 ◽

Vol 3 (3) ◽

Keyword(s):

Solar Activity ◽

Large Scale ◽

Time Frame ◽

Precipitation Pattern ◽

Canadian Prairie ◽

Canadian Prairies ◽

Temperature And Precipitation ◽

Mean Temperature ◽

Grain Yield And Quality ◽

The Impact

During the grain growing months of May-July, the mean temperature on the Canadian prairies has cooled down by 2ºC in the last 30 years. The cooling appears to be most certainly linked to diminishing solar activity as the Sun approaches a Grand Solar Minimum in the next decade or so. This cooling has led to a reduction in Growing Degree Days (GDDs) and has also impacted the precipitation pattern. The GDDs in conjunction with mean temperature and precipitation are important parameters for the growth of various grains (wheat, barley, canola etc.) on the prairies. In this study, we investigate the impact of declining GDDs and associated temperature and precipitation patterns on Prairie grain yields and quality. Our analysis shows that there has been a loss of about 100 GDDs over the time frame of 1985-2019. The loss in GDDs is also linked to some of the large-scale Atmosphere-Ocean parameters like the Pacific Decadal Oscillation (PDO), North Pacific Index (NPI) and Arctic Oscillation (AO). Our analysis suggests grain yield and quality could be significantly impacted in the coming years as solar activity continues to diminish.

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The influence of the large-scale circulation on the thermodynamic profiles in the trades from a Lagrangian perspective

10.5194/egusphere-egu2020-4859 ◽

2020 ◽

Author(s):

Leonie Villiger ◽

Franziska Aemisegger ◽

Maxi Boettcher ◽

Heini Wernli

Keyword(s):

Large Scale ◽

Surface Wind ◽

Cloud Amount ◽

Phase Changes ◽

Stable Water Isotopes ◽

Geophysical Research ◽

Large Scale Circulation ◽

Near Surface ◽

Diabatic Processes ◽

The Impact

In the tropical winter trades of the North Atlantic in the vicinity of Barbados four different mesoscale organisation patterns of clouds &#8211; sugar, gravel, flower, fish - are observed regularly. Each pattern is associated with a distinct cloud amount and radiative footprint. Therefore, the relative occurrence frequency of these patterns affects the global radiative budget. As shown by a recent study (Bony et al. 2019, Geophysical Research Letter), the occurrence of the four patterns is controlled by the near-surface wind speed and the strength of lower tropospheric instability. It is however not yet clear, whether these cloud patterns occur preferably in specific larger-scale flow configurations. These can be associated for example with upper-level wave breaking in the extratropics and different positions and strengths of low-level subtropical anticyclones.Lower tropospheric air parcels at different altitudes in the trades are expected to have different transport histories associated with distinct diabatic processes such as radiative effects, phase changes within and below clouds and turbulent mixing. The diabatic processes encountered during transport modulate the thermodynamic properties of the air parcels and therefore influence the vertical thermodynamic structure of the atmosphere in the trades.In this study, the impact of large-scale air mass advection on the thermodynamic profiles over Barbados is analysed for each of the four mesoscale organisation patterns observed during EUREC4A. The airmass transport history is characterised for different homogenous atmospheric layers. These layers are identified based on vertical pseudo-soundings above the Barbados Cloud Observatory (BCO) using ECMWF analysis data for cases where profiles agree well with independent observations from balloon soundings. The large-scale circulation within the 10 days prior to the sounding is considered for computing the trajectories of the air masses arriving in these layers. Backward trajectories are calculated with three-dimensional analysis wind fields. Thereby, the thermodynamic history and large-scale circulation configuration associated with the four cloud organisation patterns is described from a Lagrangian perspective. In addition, composites of the sea level pressure field provide information whether the four patterns co-occur with systematically differing positions and/or intensities of subtropical anticyclones. In future work, stable water isotopes will be used as observational tracers to find supportive evidence of the characterised transport history.

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Overview of current and expected seasonal climatic anomalies for the winter 2021/2022 with their possible impact on the economy, as estimated by the meteorological services of the CIS countries

Hydrometeorological research and forecasting ◽

10.37162/2618-9631-2021-4-163-176 ◽

2021 ◽

Vol 4 ◽

pp. 163-176

Author(s):

V.M. Khan ◽

◽

Keyword(s):

Air Temperature ◽

Social Life ◽

Large Scale ◽

Winter Season ◽

Northern Eurasia ◽

Temperature And Precipitation ◽

Skill Scores ◽

Cis Countries ◽

Temperature Impacts ◽

The Impact

Based on assessments of the meteorological services of the CIS countries, the skill scores of the consensus forecast for the territory of Northern Eurasia for the summer of 2021 are presented. The results of monitoring circulation patterns in the stratosphere and troposphere over the past summer season are discussed. Climate monitoring and seasonal forecasting results for the current situation are presented. A probabilistic consensus forecast for air temperature and precipitation is presented for the upcoming winter season 2021/2022 in Northern Eurasia. Possible consequences of the impact of the expected anomalies of meteorological parameters on the economy sectors and social life are discussed. Keywords: North Eurasian Climate Forum, North Eurasian Climate Center, consensus forecast, air temperature, precipitation, large-scale atmospheric circulation, hydrodynamic models, sea surface temperature, impacts

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Gradual transition from temperature to precipitation controlled regime in Rhone River discharges

10.5194/egusphere-egu2020-15757 ◽

2020 ◽

Author(s):

Carla Taricco ◽

Sara Rubinetti ◽

Enrico Arnone ◽

Davide Zanchettin ◽

Angelo Rubino ◽

...

Keyword(s):

Spectral Analysis ◽

Annual Cycle ◽

Large Scale ◽

Gradual Transition ◽

Rhône River ◽

Temporal Behaviour ◽

Temperature And Precipitation ◽

Rhone River ◽

Discharge Regime ◽

The Impact

River discharge series provide large-scale hydrological information over a broad range of timescales. Despite discharge records consist of punctual measurements, they integrate variations in snowmelting, precipitation and runoff processes over the catchment till the discharge measurement site.Discharges of the Rhone River, one of the largest rivers in Europe, have been monitored accurately during the last century at different sites. Long discharge records from seven stations along the course reveal the spatial and temporal behaviour of discharges from the source of the river to its mouth.&#160; An accurate spectral analysis of the records, performed using advanced spectral analysis methods, allow us to extract significant periodic variations in the records at different temporal scales. Then, we analyse the sensitivity of such periodic variations to evolving hydroclimate conditions, in particular focusing on the relationship between discharge and temperature and precipitation.The strong annual oscillation recorded at stations close to the source is almost entirely due to snow melting on alpine glaciers, closely resembling the temperature annual cycle. This remarkable agreement allows to consider the upstream discharges as a thermometer on the glacier region during the melting season.&#160;On the contrary, the decrease of the annual cycle going towards the mouth of the river and the contemporary growth of interannual components demonstrates the transition from a temperature to a precipitation controlled discharge regime.We will finally discuss the impact of large-scale variability patterns on the detected discharge variations and associated implications for their near-term predictability.

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Heatwaves over Europe: Identification and connection to large-scale circulation

10.5194/egusphere-egu2020-5619 ◽

2020 ◽

Author(s):

Emmanuel Rouges ◽

Laura Ferranti ◽

Holger Kantz ◽

Florian Pappenberger

Keyword(s):

High Pressure ◽

Heat Wave ◽

Crop Production ◽

Large Scale ◽

Heat Waves ◽

Early Warning Systems ◽

Temperature Threshold ◽

Large Scale Circulation ◽

Circulation Patterns ◽

The Impact

&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; Heat waves have important impacts on society and our environment. In Europe for instance, the summer of 2003 caused upwards of 40000 fatalities. They also impact the crop production, ecosystems, and infrastructures. In a warming climate, heat wave intensity and frequency are likely to increase with potentially more dramatic consequences.&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; Considering this, it is crucial to forecast such extreme events and therefore gain a better understanding of their triggering processes. The determination of these processes requires to identify heat wave patterns (timing and location) together with the correlated large-scale circulation patterns. This will enable to devise early warning systems, that could help mitigate the impact.&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; This work is part of an ongoing PhD project focusing on improving the forecast of heat waves at sub-seasonal time scale. The main objectives are to evaluate the link between large scale weather patterns and severe warm events over Europe and measure current level of predictive skill. The first part will focus on defining an objective criteria to identify heat wave events in the ERA5 reanalaysis dataset from ECMWF. The identification of heat waves depends on three main criteria: temperature threshold, spatial and temporal extension. Meaning that the temperature should exceed a defined threshold over a large enough region and for a long enough period. We will consider daily means as well as maximum and minimum values of 2m temperature. We will identify the circulation patterns (persistent high pressure systems) associated with heat wave events and analyse the key differences with persistent high pressure systems that are not associated with heat waves.&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; This work is part of the Climate Advanced Forecasting of sub-seasonal Extremes (CAFE) project, funded by the European Union&#8217;s Horizon 2020 research and innovation programme under the Marie Sk&#322;odowska-Curie grand agreement No 813844.

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Pacific Decadal Oscillation and recent oxygen decline in the eastern tropical Pacific Ocean

Biogeosciences ◽

10.5194/bg-15-7111-2018 ◽

2018 ◽

Vol 15 (23) ◽

pp. 7111-7126 ◽

Cited By ~ 4

Author(s):

Olaf Duteil ◽

Andreas Oschlies ◽

Claus W. Böning

Keyword(s):

Pacific Ocean ◽

Pacific Decadal Oscillation ◽

Large Scale ◽

Eastern Pacific ◽

Positive Phase ◽

Biogeochemical Model ◽

Eastern Pacific Ocean ◽

Large Scale Circulation ◽

Diffusive Processes ◽

The Impact

Abstract. The impact of the positive and negative phases of the Pacific Decadal Oscillation (PDO) on the extension of the poorly oxygenated regions of the eastern Pacific Ocean was assessed using a coupled ocean circulation–biogeochemical model. We show that during a “typical” PDO-positive phase the volume of the suboxic regions expands by 7 % over 50 years due to a slowdown of the large-scale circulation related to the decrease in the intensity of the trade winds. Changes in oxygen levels are mostly controlled by advective processes between 10∘ N and 10∘ S, whereas diffusive processes are dominant poleward of 10∘: in a “typical” PDO-positive phase the sluggish equatorial current system provides less oxygen to the eastern equatorial part of the basin while the oxygen transport by diffusive processes significantly decreases south of 10∘ S. The suboxic region located north of 10∘ N displays less sensitivity to the phase of the PDO as the local upwelling-related processes play a dominant role compared to the large-scale circulation in setting the oxygen concentration. Our study suggests that the prevailing PDO-positive conditions since 1975 may explain a significant part of the current deoxygenation occurring in the eastern Pacific Ocean.

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