Moisture transport to a typical transitional climate zone in North China forced by atmospheric and oceanic internal variability under the background of global warming

Abstract Persistent extreme heat events (PEHEs) exert a more negative impact on society, including agriculture, plant phenology, power production and human health, compared to general EHEs. The temporal and spatial characteristics of summer PEHEs in eastern China were analysed based on a daily maximum temperature dataset from 759 stations over the period of 1961–2018. The results show the following: Persistent distributions of PEHEs show that they are characterized by an exponential decay with a drop in the decay rate. In terms of spatial distribution, there is an apparent regional difference in the duration of PEHEs. North China is dominated by multi-frequency and short-duration EHEs, while South China is the opposite. PEHEs in North China and the Huanghuai region mainly occur in June-July but mostly in July and August in South China. Strongly responding to global warming, the frequency and duration of PEHEs in North China have increased since the 1990s. However, the frequency of PEHEs in North China and the Huanghuai region has shown opposite trends in June-July since the beginning of the 21st century. Affected by the atmospheric circulations, the regional differences in PEHE frequency are also apparent. Since the beginning of the 21st century, the PEHEs in North China and the Huanghuai area have shown an increasing trend in August. The short-term PEHEs in the middle and lower reaches of the Yangtze River and South China increased rapidly in the 2000s, while long-term PEHEs increased in the 2010s. This study implies that attention should be paid to not only the frequency of EH days but also to the persistence of EHE which is a key characteristic of damaging EH.

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Large internal variability dominates over global warming signal in observed lower stratospheric QBO amplitude

Journal of Climate ◽

10.1175/jcli-d-21-0270.1 ◽

2021 ◽

pp. 1-43

Author(s):

Aaron Match ◽

Stephan Fueglistaler

Keyword(s):

Global Warming ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Internal Variability ◽

Dynamical Process ◽

Quasi Biennial Oscillation ◽

Amplitude Profile ◽

Biennial Oscillation ◽

Middle Stratosphere

AbstractGlobal warming projections of dynamics are less robust than projections of thermodynamics. However, robust aspects of the thermodynamics can be used to constrain some dynamical aspects. This paper argues that tropospheric expansion under global warming (a thermodynamical process) explains changes in the amplitude of the Quasi-Biennial Oscillation (QBO) in the lower and middle stratosphere (a dynamical process). A theoretical scaling for tropospheric expansion of approximately 6 hPa K−1 is derived, which agrees well with global climate model (GCM) experiments. Using this theoretical scaling, the response of QBO amplitude to global warming is predicted by shifting the climatological QBO amplitude profile upwards by 6 hPa per Kelvin of global warming. In global warming simulations, QBO amplitude in the lower- to mid-stratosphere shifts upwards as predicted by tropospheric expansion. Applied to observations, the tropospheric expansion framework suggests a historical weakening of QBO amplitude at 70 hPa of 3% decade−1 from 1953-2020. This expected weakening trend is half of the 6% decade−1 from 1953-2012 detected and attributed to global warming in a recent study. The previously reported trend was reinforced by record low QBO amplitudes during the mid-2000s, from which the QBO has since recovered. Given the modest weakening expected on physical grounds, past decadal modulations of QBO amplitude are reinterpreted as a hitherto unrecognized source of internal variability. This large internal variability dominates over the global warming signal, such that despite 65 years of observations, there is not yet a statistically significant weakening trend.

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Influence of Internal Variability and Global Warming on Multidecadal Changes in Regional Drought Severity over the Continental United States

Journal of Hydrometeorology ◽

10.1175/jhm-d-18-0167.1 ◽

2019 ◽

Vol 20 (3) ◽

pp. 411-429 ◽

Cited By ~ 1

Author(s):

Tushar Apurv ◽

Ximing Cai ◽

Xing Yuan

Keyword(s):

United States ◽

Global Warming ◽

Great Plains ◽

North Atlantic Ocean ◽

Internal Variability ◽

Drought Severity ◽

Support Vector ◽

Drought Risk ◽

Decadal Scale ◽

Near Future

Abstract Meteorological droughts in the continental United States (CONUS) are known to oscillate at the multidecadal time scale in response to the sea surface temperatures (SST) variability over the Pacific Ocean and the North Atlantic Ocean. While previous studies have focused on understanding the influence of SST oscillations on drought frequency over the CONUS, this information has not been integrated with global warming for future drought risk assessment at the decadal scale. In this study, we use the support vector machines (SVMs) to handle correlation between input variables for quantifying the influence of internal variability [Atlantic multidecadal oscillation (AMO) and Pacific decadal oscillation (PDO)] and global warming on the decadal changes in the severity of seasonal droughts over the CONUS during 1901–2015. The regional drivers of drought severity identified using SVMs are used for the assessment of decadal drought risk in the near future. We find internal variability as the dominant driver of decadal changes in drought severity in the southern and central Great Plains and global warming as the dominant driver for the southeastern and southwestern United States. In the southern Plains, the existing pattern of increasing drought severity is likely to persist in the near future if AMO and PDO remain in their positive and negative phases, respectively, while global warming is likely to contribute to increasing drought severity in the Southeast and Southwest. This study suggests an emerging role of global warming in drought risk over the southern states, where near-term climate change adaptation is necessary.

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Using a long-term climate simulation to address future changes in Western Europe precipitation regimes due to global warming

10.5194/egusphere-egu2020-7550 ◽

2020 ◽

Author(s):

Pedro M. Sousa ◽

Alexandre M. Ramos ◽

Ricardo M. Trigo ◽

Christoph C. Raible ◽

Martina Messmer ◽

...

Keyword(s):

Global Warming ◽

Moisture Transport ◽

Large Scale ◽

Western Europe ◽

Warming Trend ◽

Water Vapor Transport ◽

Climate Simulation ◽

Wet Season ◽

Precipitation Regimes

Moisture transport and Atmospheric Rivers (ARs) over the Northeastern Atlantic are a very relevant process for the inter-annual variability of precipitation over Western Europe. Based on a long-term transient simulation (850-2100CE) from the CESM model, we have showed that moisture transport towards Western Europe (using the vertically integrated horizontal water vapor transport, IVT) has been increasing significantly since pre-industrial period, in a clear association with the global warming trend. Both current and projected changes (using RCP 8.5) significantly exceed the range given by inter-annual to inter-decadal internal/external variability observed during the last millennium.We have checked the emergence of the temperature, IVT and precipitation signals in Iberia and the UK, showing that while the first two have now clearly emerged from the pre-warming state, precipitation series are still slightly below that threshold. Nevertheless, projections clearly show an increase in rainfall at higher latitudes (i in phase with a warmer and moister atmosphere); and a decrease at lower latitudes decoupled from the overall increase in moisture availability. Additionally we have explored the role played by large-scale circulation and atmospheric dynamics for these contrasting projections. Overall, results show that a poleward migration of moisture corridors and ARs explain a significant fraction of these projected trends. Based on the Clausius&#8211;Clapeyron relation we have separated the thermodynamical from dynamical changes. We also show how that a significant increase in subtropical anticyclonic activity over Iberia is responsible for: i) dynamical circulation changes; ii) a shortening of the wet season; iii) to less efficient precipitation regimes in the region. These results highlight the urge to adapt to a drying trend in Mediterranean-type climates, as a consequence of Global Warming.&#160;The financial support for this work was possible through the following FCT project: HOLMODRIVE - North Atlantic Atmospheric Patterns influence on Western Iberia Climate: From the Lateglacial to the Present [PTDC/CTA-GEO/29029/2017]

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Increased risk of near term global warming due to a recent AMOC weakening

Nature Communications ◽

10.1038/s41467-021-26370-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Rémy Bonnet ◽

Didier Swingedouw ◽

Guillaume Gastineau ◽

Olivier Boucher ◽

Julie Deshayes ◽

...

Keyword(s):

Global Warming ◽

Low Frequency ◽

Internal Variability ◽

Atlantic Meridional Overturning Circulation ◽

Meridional Overturning Circulation ◽

The Past ◽

Increased Risk ◽

Meridional Overturning ◽

Near Term ◽

New Generation

AbstractSome of the new generation CMIP6 models are characterised by a strong temperature increase in response to increasing greenhouse gases concentration1. At first glance, these models seem less consistent with the temperature warming observed over the last decades. Here, we investigate this issue through the prism of low-frequency internal variability by comparing with observations an ensemble of 32 historical simulations performed with the IPSL-CM6A-LR model, characterized by a rather large climate sensitivity. We show that members with the smallest rates of global warming over the past 6-7 decades are also those with a large internally-driven weakening of the Atlantic Meridional Overturning Circulation (AMOC). This subset of members also matches several AMOC observational fingerprints, which are in line with such a weakening. This suggests that internal variability from the Atlantic Ocean may have dampened the magnitude of global warming over the historical era. Taking into account this AMOC weakening over the past decades means that it will be harder to avoid crossing the 2 °C warming threshold.

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Greenhouse gas emissions and net global warming potential of vineyards under different fertilizer and water managements in North China

Agricultural Water Management ◽

10.1016/j.agwat.2020.106521 ◽

2021 ◽

Vol 243 ◽

pp. 106521

Author(s):

Jie Zhang ◽

Yanjie Guo ◽

Jian Han ◽

Yanzhi Ji ◽

Lijuan Zhang

Keyword(s):

Global Warming ◽

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

Global Warming Potential ◽

North China ◽

Gas Emissions ◽

Net Global Warming Potential

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Multi-scale characteristics of moisture transport during a rainstorm process in North China

Atmospheric Research ◽

10.1016/j.atmosres.2014.04.008 ◽

2014 ◽

Vol 145-146 ◽

pp. 189-204 ◽

Cited By ~ 10

Author(s):

Chengxin Wang ◽

Shouting Gao ◽

Li Liang ◽

Difei Deng ◽

Hainan Gong

Keyword(s):

Moisture Transport ◽

North China ◽

Multi Scale ◽

Scale Characteristics

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Understanding Decreases in Land Relative Humidity with Global Warming: Conceptual Model and GCM Simulations

Journal of Climate ◽

10.1175/jcli-d-16-0351.1 ◽

2016 ◽

Vol 29 (24) ◽

pp. 9045-9061 ◽

Cited By ~ 74

Author(s):

Michael P. Byrne ◽

Paul A. O’Gorman

Keyword(s):

Global Warming ◽

Relative Humidity ◽

Land Surface ◽

Moisture Transport ◽

General Circulation ◽

Stomatal Closure ◽

General Circulation Models ◽

Box Model ◽

Specific Humidity ◽

Near Surface

Abstract Climate models simulate a strong land–ocean contrast in the response of near-surface relative humidity to global warming; relative humidity tends to increase slightly over oceans but decrease substantially over land. Surface energy balance arguments have been used to understand the response over ocean but are difficult to apply over more complex land surfaces. Here, a conceptual box model is introduced, involving atmospheric moisture transport between the land and ocean and surface evapotranspiration, to investigate the decreases in land relative humidity as the climate warms. The box model is applied to simulations with idealized and full-complexity (CMIP5) general circulation models, and it is found to capture many of the features of the simulated changes in land humidity. The simplest version of the box model gives equal fractional increases in specific humidity over land and ocean. This relationship implies a decrease in land relative humidity given the greater warming over land than ocean and modest changes in ocean relative humidity, consistent with a mechanism proposed previously. When evapotranspiration is included, it is found to be of secondary importance compared to ocean moisture transport for the increase in land specific humidity, but it plays an important role for the decrease in land relative humidity. For the case of a moisture forcing over land, such as from stomatal closure, the response of land relative humidity is strongly amplified by the induced change in land surface–air temperature, and this amplification is quantified using a theory for the link between land and ocean temperatures.

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