scholarly journals Decoding the dynamic of poleward shifting climate zones using aqua-planet model simulation

2021 ◽  
Author(s):  
Hu Yang ◽  
Jian Lu ◽  
Xiaoxu Shi ◽  
Qiang Wang ◽  
Gerrit Lohmann
Keyword(s):  
Atmospheric Circulation ◽  
Ocean Circulation ◽  
Model Simulation ◽  
Surface Wind ◽  
Ocean Warming ◽  
Ocean Dynamics ◽  
Causal Mechanism ◽  
Near Surface ◽  
Climate Zones ◽  
Poleward Shift

Abstract Growing evidence implies that the atmospheric and oceanic circulation experiences a systematic poleward shift in a warming climate. However, the complexity of climate system, including the coupling between the ocean and the atmosphere, natural climate variability and land-sea distribution, tends to obfuscate the causal mechanism underlying the circulation shift. Here, using an idealized coupled aqua-planet model, we explore the mechanism of the shifting circulation, by isolating the contributing factors from the direct CO2 forcing, the indirect ocean surface warming, and the wind-stress feedback from the ocean dynamics. We find that, in contrast to direct CO2 forcing, an enhanced subtropical ocean warming plays a leading role in driving the circulation shift. This enhanced subtropical ocean warming emerges from the background Ekman convergence of surface anomalous heat in the absence of the ocean dynamical change. It expands the tropical warm water zone, causes a poleward shift of the meridional temperature gradients, hence forces a corresponding shift in the atmospheric circulation. The shift in the atmospheric circulation in turn drives a shift in the ocean circulation. Our simulations, despite being idealized, capture the main features of observed climate changes, for example, the enhanced subtropical ocean warming, poleward shift of the patterns of near-surface wind, sea level pressure, storm tracks, precipitation and large-scale ocean circulation, implying that increase in greenhouse gas concentrations not only raises the temperature, but can also systematically shift the climate zones poleward.

scholarly journals Decoding the dynamics of poleward shifting climate zones using aqua-planet model simulations

2022 ◽  
Author(s):  
Hu Yang ◽  
Jian Lu ◽  
Qiang Wang ◽  
Xiaoxu Shi ◽  
Gerrit Lohmann
Keyword(s):  
Ocean Circulation ◽  
Surface Wind ◽  
Ocean Surface ◽  
Ocean Warming ◽  
Ocean Dynamics ◽  
Causal Mechanism ◽  
Near Surface ◽  
Climate Zones ◽  
Surface Warming ◽  
Poleward Shift

AbstractGrowing evidence indicates that the atmospheric and oceanic circulation experiences a systematic poleward shift in a warming climate. However, the complexity of the climate system, including the coupling between the ocean and the atmosphere, natural climate variability and land-sea distribution, tends to obfuscate the causal mechanism underlying the circulation shift. Here, using an idealised coupled aqua-planet model, we explore the mechanism of the shifting circulation, by isolating the contributing factors from the direct CO$$_2$$ 2 forcing, the indirect ocean surface warming, and the wind-stress feedback from the ocean dynamics. We find that, in contrast to the direct CO$$_2$$ 2 forcing, ocean surface warming, in particular an enhanced subtropical ocean warming, plays an important role in driving the circulation shift. This enhanced subtropical ocean warming emerges from the background Ekman convergence of surface anomalous heat in the absence of the ocean dynamical change. It expands the tropical warm water zone, causes a poleward shift of the mid-latitude temperature gradient, hence forces a corresponding shift in the atmospheric circulation and the associated wind pattern. The shift in wind, in turn drives a shift in the ocean circulation. Our simulations, despite being idealised, capture the main features of the observed climate changes, for example, the enhanced subtropical ocean warming, poleward shift of the patterns of near-surface wind, sea level pressure, storm tracks, precipitation and large-scale ocean circulation, implying that increase in greenhouse gas concentrations not only raises the temperature, but can also systematically shift the climate zones poleward.

scholarly journals Understanding the dynamic of poleward shifting of atmospheric and oceanic circulation using aqua-planet model simulations​

2021 ◽  
Author(s):  
Hu Yang ◽  
Jian Lu ◽  
Xiaoxu Shi ◽  
Qiang Wang ◽  
Gerrit Lohmann
Keyword(s):  
Atmospheric Circulation ◽  
Ocean Circulation ◽  
Surface Wind ◽  
Ocean Warming ◽  
Ocean Dynamics ◽  
Circulation System ◽  
Oceanic Circulation ◽  
Dynamical Mechanism ◽  
Near Surface ◽  
Poleward Shift

<p>Growing evidence suggests that the oceanic and atmospheric circulation experiences a systematic poleward shift under climate change. However, due to the complexity of climate system, such as, the coupling between the ocean and the atmosphere, natural climate variability and land-sea distribution, the dynamical mechanism of such shift is still not fully understood. Here, using an idealized partially coupled ocean and atmosphere aqua-planet model, we explore the mechanism of the shifting oceanic and atmospheric circulation. We find that, in contrast to the rising GHG concentration, the subtropical ocean warming plays a dominant role in driving the shift in the circulation system. More specifically, due to background ocean dynamics, a relatively faster warming over the subtropical ocean drives a poleward shift in the atmospheric circulation. The shift in the atmospheric circulation in turn drives a shift in the oceanic circulation. Our simulations, despite being idealized, capture the main features of observed climate changes, for example, the enhanced subtropical ocean warming, poleward shift of the patterns of near-surface wind, sea level pressure, cloud, precipitation, storm tracks and large-scale ocean circulation, implying that global warming not only raises the temperature, but also systematically shifts the climate zones.​</p>

Atlantic coastal sea level variability and synoptic-scale meteorological forcing

2021 ◽  
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
Tide Gauge ◽  
Surface Wind ◽  
High Tide ◽  
The United States ◽  
Ocean Dynamics ◽  
Flood Events ◽  
Synoptic Scale ◽  
Sea Level Variability

Abstract Anomalous sea levels along the Mid- and South- Atlantic coasts of the United States are often linked to atmosphere- ocean dynamics, remote- and local- scale forcing and other factors linked to cyclone passage, winds, waves, and storm surge. Herein, we examine sea level variability along the U.S. Atlantic coast through satellite altimeter and coastal tide gauge data within the context of synoptic-scale weather pattern forcing. Altimetry, derived from sea level anomaly (SLA) data between 1993 and 2019 were compared with Self Organizing Map (SOM)-based atmospheric circulation and surface wind field categorizations to reveal spatiotemporal patterns and their inter-relationships with high water-level conditions at tide gauges. Regional elevated sea level patterns and variability were strongly associated with synergistic patterns of atmospheric circulation and wind. Recurring atmospheric patterns associated with high-tide flooding events and flood risk were identified, as were specific regional oceanographic variability patterns of SLA response. The incorporation of combined metrics of wind and circulation patterns further isolate atmospheric drivers of high tide flood events and may have particular significance for predicting future flood events over multiple spatial and temporal scales.

scholarly journals LGM climate forcing and ocean dynamical feedback and their implications for estimating climate sensitivity

2020 ◽  
Author(s):  
Jiang Zhu ◽  
Christopher J. Poulsen
Keyword(s):  
Ocean Circulation ◽  
Climate Sensitivity ◽  
Radiative Forcing ◽  
Climate Models ◽  
Model Simulation ◽  
Ice Sheets ◽  
Ocean Model ◽  
Ocean Dynamics ◽  
True Value ◽  
Climate Forcings

Abstract. Equilibrium climate sensitivity (ECS) has been directly estimated using reconstructions of past climates that are different than today’s. A challenge to this approach is that temperature proxies integrate over the timescales of the fast feedback processes (e.g. changes in water vapor, snow, and clouds) that are captured in ECS as well as the slower feedback processes (e.g. changes in ice sheets and ocean circulation) that are not. A way around this issue is to treat the slow feedbacks as climate forcings and independently account for their impact on global temperature. Here we conduct a suite of Last Glacial Maximum (LGM) simulations using the Community Earth System Model version 1.2 (CESM1.2) to quantify the forcing and efficacy of land ice sheets (LIS) and greenhouse gases (GHG) in order to estimate ECS. Our forcing and efficacy quantification adopts the effective radiative forcing (ERF) and adjustment framework and provides a complete accounting for the radiative, topographic, and dynamical impacts of LIS on surface temperatures. ERF and efficacy of LGM LIS are −3.2 W m−2 and 1.1, respectively. The larger-than-unity efficacy is caused by the relatively larger temperature changes over land and the Northern Hemisphere subtropical oceans than those in response to a doubling of atmospheric CO2. The subtropical SST response is linked to LIS-induced wind changes and feedbacks in ocean-atmosphere coupling and clouds. ERF and efficacy of LGM GHG are −2.8 W m−2 and 0.9, respectively. The lower efficacy is primarily attributed to a smaller cloud feedback at colder temperatures. Our simulations further demonstrate that the direct ECS calculation using the forcing, efficacy, and temperature response in CESM1.2 overestimates the true value in the model by 25 % due to the neglect of slow ocean dynamical feedback. This is supported by the greater cooling (6.8 °C) in a fully coupled LGM simulation than that (5.3 °C) in a slab ocean model simulation with ocean dynamics disabled. The majority (67 %) of the ocean dynamical feedback is attributed to dynamical changes in the Southern Ocean, where interactions between ocean stratification, heat transport, and sea-ice cover are found to amplify the LGM cooling. Our study demonstrates the value of climate models in the quantification of climate forcings and the ocean dynamical feedback, which is necessary for an accurate direct ECS estimation.

Recent reversal of mean wind speed and gusts across the Iberian Peninsula and its relationship with modes of climate variability, 1961-2019

2021 ◽  
Author(s):  
Eduardo Utrabo-Carazo ◽  
Cesar Azorin-Molina ◽  
Encarna Serrano ◽  
Enric Aguilar ◽  
Manola Brunet
Keyword(s):  
Wind Speed ◽  
Iberian Peninsula ◽  
Atmospheric Circulation ◽  
Weather Forecasting ◽  
Surface Wind ◽  
Wind Gust ◽  
Near Surface ◽  
Modes Of Variability ◽  
Mean Wind Speed ◽  
Mediterranean Oscillation

<p>In a context of climate change, near-surface wind speed (SWS) has received less attention than other variables such as air temperature or precipitation, despite its undeniable environmental and socio-economic impacts. Studies suggest a generalized decrease of SWS in continental surfaces located in the middle latitudes from 1979 to 2010, the so-called stilling phenomenon, and an increase in it thereafter, which has been termed reversal or recovery phenomenon. Recent studies indicate that multidecade oscillations produced by the internal variability of the climate system are responsible for both phenomena. The aim of this work is to advance in the evaluation of the multidecadal variability and causes of the stilling and reversal in the observed SWS, covering the complete 2010s decade and focusing on the Iberian Peninsula region (IP). More specifically, the particular objectives of this study are: (i) to determine for the first time the occurrence of the reversal phenomenon in the IP over the last decade(s), identifying its onset year and its magnitude; (ii) to deepen into the relation between atmospheric teleconnection indices and observed trends in SWS; and (iii) to link atmospheric circulation changes to observed SWS variability. For that purpose, homogenized series of mean wind speed and gusts will be used, as well as data from the ERA5 reanalysis (European Centre for Medium-Range Weather Forecasting). Three SWS parameters will be analysed: monthly mean SWS anomaly; monthly mean daily peak wind gust (DPWG) anomaly; and number of days in which the value of DPWG exceeds the 90th percentile of the series considered. Trends of these parameters will be calculated, as well as the correlation between them and the modes of variability that govern in the region: North Atlantic Oscillation (NAO), Mediterranean Oscillation (MO) and Western Mediterranean Oscillation. Finally, trends of these modes of variability and of other parameters dependent on atmospheric circulation (e.g., geostrophic wind) will be calculated to try to clarify the drivers of the observed changes in the SWS.</p>

Global Near-Surface Wind Speed Changes over the Last Decades Revealed by Reanalyses and CMIP6 Model Simulations

2020 ◽  
pp. 1-53
Author(s):  
Kaiqiang Deng ◽  
Cesar Azorin-Molina ◽  
Lorenzo Minola ◽  
Gangfeng Zhang ◽  
Deliang Chen
Keyword(s):  
Wind Speed ◽  
Atmospheric Circulation ◽  
Decadal Variability ◽  
Surface Wind ◽  
Coupled Model ◽  
Surface Wind Speed ◽  
Hadley Cell ◽  
Near Surface ◽  
Model Simulations ◽  
Hydrological Cycles

AbstractNear-surface (10 m) wind speed (NWS) plays a crucial role in e.g. hydrological cycles, wind energy production and air pollution, but what drives their multi-decadal changes is still unclear. Using reanalysis datasets and Coupled Model Inter-comparison Projection Phase 6 (CMIP6) model simulations, this study investigates recent trends in the annual mean NWS. The results show that the northern hemisphere (NH) terrestrial NWS experienced significant (p<0.1) decreasing trends during 1980–2010, when the southern hemisphere (SH) ocean NWS was characterized by significant (p<0.1) upward trends. However, during 2010–2019, global NWS trends shifted in their sign: NWS trends over the NH land became positive, and trends over the SH tended to be negative. We propose that the strengthening of SH NWS during 1980–2010 was associated with intensified Hadley cell over the SH, while the declining of NH land NWS could have been caused by changes in atmospheric circulation, alteration of vegetation/land-use and the accelerating Arctic warming. The CMIP6 model simulations further demonstrate that the greenhouse gas (GHG) warming plays an important role in triggering the NWS trends over the two hemispheres during 1980–2010 through modulating meridional atmospheric circulation. This study also points at the importance of anthropogenic GHG forcing and the natural Pacific Decadal Oscillation to the long-term trends and multi-decadal variability in global NWS, respectively.

scholarly journals Mechanisms shaping wind convergence under extreme synoptic situations over the Gulf Stream region

2021 ◽  
pp. 1-53
Author(s):  
Victor Rousseau ◽  
Emilia Sanchez-Gomez ◽  
Rym Msadek ◽  
Marie-Pierre Moine
Keyword(s):  
Atmospheric Circulation ◽  
Gulf Stream ◽  
Surface Wind ◽  
Vertical Mixing ◽  
Atmospheric Model ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Atmospheric Conditions ◽  
Near Surface ◽  
Wind Regimes

AbstractAir-sea interaction processes over the Gulf Stream have received particular attention over the last decade. It has been shown that sea surface temperature (SST) gradients over the Gulf Stream can alter the near surface wind divergence through changes in the marine atmospheric boundary layer (MABL). Two mechanisms have been proposed to explain the response: the Vertical Mixing Mechanism (VMM) and the Pressure Adjustment Mechanism (PAM). However, their respective contribution is still under debate. It has been argued that the synoptic perturbations over the Gulf Stream can provide more insight on the MABL response to SST fronts. We analyze the VMM and PAM under different atmospheric conditions obtained from a classification method based on the deciles of the statistical distribution of winter turbulent heat fluxes over the Gulf Stream. Lowest deciles are associated with weak air-sea interactions and anticyclonic atmospheric circulation over the Gulf Stream, whereas highest deciles are related to strong air-sea interactions and a cyclonic circulation. Our analysis includes the low and high-resolution versions of the ARPEGEv6 atmospheric model forced by observed SST, and the recently released ERA5 global reanalysis. We find that the occurrence of anticyclonic and cyclonic perturbations associated with different anomalous wind regimes can locally modulate the activation of the VMM and the PAM. In particular, the PAM is predominant in anticyclonic conditions, whereas both mechanisms are equally present in most of the cyclonic conditions. Our results highlight the role of the atmospheric circulation and associated anomalous winds in the location, strength and occurrence of both mechanisms.

scholarly journals Hurricane Sea Surface Inflow Angle and an Observation-Based Parametric Model

2012 ◽  
Vol 140 (11) ◽  
pp. 3587-3605 ◽  
Author(s):  
Jun A. Zhang ◽  
Eric W. Uhlhorn
Keyword(s):  
Ocean Circulation ◽  
Numerical Models ◽  
Surface Wind ◽  
Radial Distance ◽  
Parametric Model ◽  
Wind Vector ◽  
Near Surface ◽  
Storm Intensity ◽  
Significant Dependence ◽  
Motion Speed

Abstract This study presents an analysis of near-surface (10 m) inflow angles using wind vector data from over 1600 quality-controlled global positioning system dropwindsondes deployed by aircraft on 187 flights into 18 hurricanes. The mean inflow angle in hurricanes is found to be −22.6° ± 2.2° (95% confidence). Composite analysis results indicate little dependence of storm-relative axisymmetric inflow angle on local surface wind speed, and a weak but statistically significant dependence on the radial distance from the storm center. A small, but statistically significant dependence of the axisymmetric inflow angle on storm intensity is also found, especially well outside the eyewall. By compositing observations according to radial and azimuthal location relative to storm motion direction, significant inflow angle asymmetries are found to depend on storm motion speed, although a large amount of unexplained variability remains. Generally, the largest storm-relative inflow angles (&lt;−50°) are found in the fastest-moving storms (&gt;8 m s−1) at large radii (&gt;8 times the radius of maximum wind) in the right-front storm quadrant, while the smallest inflow angles (&gt;−10°) are found in the fastest-moving storms in the left-rear quadrant. Based on these observations, a parametric model of low-wavenumber inflow angle variability as a function of radius, azimuth, storm intensity, and motion speed is developed. This model can be applied for purposes of ocean surface remote sensing studies when wind direction is either unknown or ambiguous, for forcing storm surge, surface wave, and ocean circulation models that require a parametric surface wind vector field, and evaluating surface wind field structure in numerical models of tropical cyclones.

Recurrence Characteristics Analysis of Near-Surface Wind Speed Signal with Different Sampling Frequencies

2014 ◽  
Vol 599-601 ◽  
pp. 1605-1609 ◽  
Author(s):  
Ming Zeng ◽  
Zhan Xie Wu ◽  
Qing Hao Meng ◽  
Jing Hai Li ◽  
Shu Gen Ma
Keyword(s):  
Wind Speed ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Recurrence Plot ◽  
Sampling Frequency ◽  
Near Surface ◽  
Gas Leakage ◽  
Time Period ◽  
Characteristics Analysis ◽  
Quantification Analysis

The wind is the main factor to influence the propagation of gas in the atmosphere. Therefore, the wind signal obtained by anemometer will provide us valuable clues for searching gas leakage sources. In this paper, the Recurrence Plot (RP) and Recurrence Quantification Analysis (RQA) are applied to analyze the influence of recurrence characteristics of the wind speed time series under the condition of the same place, the same time period and with the sampling frequency of 1hz, 2hz, 4.2hz, 5hz, 8.3hz, 12.5hz and 16.7hz respectively. Research results show that when the sampling frequency is higher than 5hz, the trends of recurrence nature of different groups are basically unchanged. However, when the sampling frequency is set below 5hz, the original trend of recurrence nature is destroyed, because the recurrence characteristic curves obtained using different sampling frequencies appear cross or overlapping phenomena. The above results indicate that the anemometer will not be able to fully capture the detailed information in wind field when its sampling frequency is lower than 5hz. The recurrence characteristics analysis of the wind speed signals provides an important basis for the optimal selection of anemometer.

scholarly journals Evaluation of HRCLDAS and ERA5 Datasets for Near-Surface Wind over Hainan Island and South China Sea

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 766
Author(s):  
Yi Jiang ◽  
Shuai Han ◽  
Chunxiang Shi ◽  
Tao Gao ◽  
Honghui Zhen ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Surface Wind ◽  
Hainan Island ◽  
The South China Sea ◽  
Wind Data ◽  
The South ◽  
Near Surface ◽  
China Sea

Near-surface wind data are particularly important for Hainan Island and the South China Sea, and there is a wide range of wind data sources. A detailed understanding of the reliability of these datasets can help us to carry out related research. In this study, the hourly near-surface wind data from the High-Resolution China Meteorological Administration (CMA) Land Data Assimilation System (HRCLDAS) and the fifth-generation ECMWF atmospheric reanalysis data (ERA5) were evaluated by comparison with the ground automatic meteorological observation data for Hainan Island and the South China Sea. The results are as follows: (1) the HRCLDAS and ERA5 near-surface wind data trend was basically the same as the observation data trend, but there was a smaller bias, smaller root-mean-square errors, and higher correlation coefficients between the near-surface wind data from HRCLDAS and the observations; (2) the quality of HRCLDAS and ERA5 near-surface wind data was better over the islands of the South China Sea than over Hainan Island land. However, over the coastal areas of Hainan Island and island stations near Sansha, the quality of the HRCLDAS near-surface wind data was better than that of ERA5; (3) the quality of HRCLDAS near-surface wind data was better than that of ERA5 over different types of landforms. The deviation of ERA5 and HRCLDAS wind speed was the largest along the coast, and the quality of the ERA5 wind direction data was poorest over the mountains, whereas that of HRCLDAS was poorest over hilly areas; (4) the accuracy of HRCLDAS at all wind levels was higher than that of ERA5. ERA5 significantly overestimated low-grade winds and underestimated high-grade winds. The accuracy of HRCLDAS wind ratings over the islands of the South China Sea was significantly higher than that over Hainan Island land, especially for the higher wind ratings; and (5) in the typhoon process, the simulation of wind by HRCLDAS was closer to the observations, and its simulation of higher wind speeds was more accurate than the ERA5 simulations.

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