scholarly journals Variations in Summer Extreme High-Temperature Events over Northern Asia and the Possible Mechanisms

2021 ◽  
pp. 1-69
Author(s):  
Haixu Hong ◽  
Jianqi Sun ◽  
Huijun Wang
Keyword(s):  
High Temperature ◽  
North Atlantic ◽  
Lower Troposphere ◽  
Longwave Radiation ◽  
Atmospheric Model ◽  
Asia Pacific ◽  
Soil Conditions ◽  
Northern Asia ◽  
Extreme High Temperature ◽  
The Impact

AbstractIn this study, interannual and interdecadal variations in the extreme high-temperature event (EHE) frequency over Northern Asia (NA) and the associated possible mechanisms are explored. On an interannual timescale, the first two empirical orthogonal function modes of the NA EHE frequency exhibit meridional dipole pattern (EOF1) and diagonal tripolar pattern (EOF2), respectively. The higher NA EHE frequency is related to anomalous local highs, reduced middle-low clouds and more solar radiation. The warmer ground further heats the overlying atmosphere through longwave radiation and sensible heat. The warm temperature advections in lower troposphere and the drier soil conditions also favor higher EHE frequency. Further analysis reveals that the EOF1 mode is related to the Polar-Eurasian teleconnection pattern (POL), while the EOF2 mode is associated with North Atlantic Oscillation (NAO) and Pacific-Japan/East Asia-Pacific pattern (PJ/EAP). The fitted EHE frequency based on the atmospheric factors (POL, NAO and PJ/EAP) can explain the interannual variation in the regionally averaged EHE frequency by 33.8%. Furthermore, three anomalous sea surface temperature (SST) patterns over the North Atlantic-Mediterranean Sea region and around the Maritime Continent are associated with the two EHE modes by intensifying the pronounced atmospheric teleconnections. Analysis on the simulation of five models in the Atmospheric Model Intercomparison Project experiment further confirms the impact of the pronounced SST patterns on the POL, NAO and PJ/EAP. In addition, NA EHE frequency experienced a significant interdecadal increase around the mid-1990s, which could be associated with the phase shift of the Atlantic Multidecadal Oscillation and long-term global warming trend.

scholarly journals Organic pollutants from tropical peatland fires: regional influences and its impact on lower stratospheric ozone

2020 ◽  
Author(s):  
Simon Rosanka ◽  
Bruno Franco ◽  
Lieven Clarisse ◽  
Pierre-François Coheur ◽  
Andreas Wahner ◽  
...  
Keyword(s):  
Biomass Burning ◽  
El Niño ◽  
El Nino ◽  
Stratospheric Ozone ◽  
Lower Troposphere ◽  
Atmospheric Model ◽  
Chemical Production ◽  
Global Models ◽  
Upward Transport ◽  
The Impact

Abstract. The particularly strong dry season in Indonesia in 2015, caused by an exceptional strong El Niño, led to severe peatland fires resulting in high volatile organic compound (VOC) biomass burning emissions. At the same time, the developing Asian monsoon anticyclone (ASMA) and the general upward transport in the intertropical convergence zone (ITCZ) efficiently transported the resulting primary and secondary pollutants to the upper troposphere/lower stratosphere (UTLS). In this study, we assess the importance of these VOC emissions for the composition of the lower troposphere and the UTLS, and we investigate the effect of in-cloud oxygenated VOC (OVOC) oxidation during such a strong pollution event. This is achieved by performing multiple chemistry simulations using the global atmospheric model ECHAM/MESSy (EMAC). By comparing modelled columns of the biomass burning marker hydrogen cyanide (HCN) to spaceborne measurements from the Infrared Atmospheric Sounding Interferometer (IASI), we find that EMAC properly captures the exceptional strength of the Indonesian fires. In the lower troposphere, the increase in VOC levels is higher in Indonesia compared to other biomass burning regions. This has a direct impact on the oxidation capacity, resulting in the largest regional reduction in hydroxyl radicals (OH) and nitrogen oxides (NOx). Even though an increase in ozone (O3) is predicted close to the peatland fires, particular high concentrations of phenols lead to an O3 depletion in eastern Indonesia. By employing the detailed in-cloud OVOC oxidation scheme Jülich Aqueous-phase Mechanism of Organic Chemistry (JAMOC), we find that the predicted changes are dampened and that by ignoring these processes, global models tend to overestimate the impact of such extreme pollution events. In the ASMA and the ITCZ, the upward transport leads to elevated VOC concentrations in the UTLS region, which results in a depletion of lower stratospheric O3. We find that this is caused by a high destruction of O3 by phenoxy radicals and by the increased formation of NOx reservoir species, which dampen the chemical production of O3. The Indonesian peatland fires regularly occur during El Niño years and contribute to the depletion of O3. In the time period from 2001 to 2016, we find that the lower stratospheric O3 is reduced by about 0.38 DU and contributes to about 25 % to the lower stratospheric O3 reduction observed by remote sensing. By not considering these processes, global models might not be able to reproduce this variability in lower stratospheric O3.

scholarly journals Pivotal role of the North African Dipole Intensity (NAFDI) on alternate Saharan dust export over the North Atlantic and the Mediterranean, and relationship with the Saharan Heat Low and mid-latitude Rossby waves

2016 ◽  
Author(s):  
E. Cuevas ◽  
Á. J. Gómez-Peláez ◽  
S. Rodríguez ◽  
E. Terradellas ◽  
S. Basart ◽  
...  
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Rossby Waves ◽  
Lower Troposphere ◽  
North African ◽  
Zonal Wind Anomaly ◽  
Western Sahara ◽  
The North ◽  
The Impact ◽  
Heat Low

Abstract. In this study, we revise the index that quantifies the North African Dipole Intensity (NAFDI), and explain its relationship with the Saharan Heat Low (SHL) and mid-latitude Rossby waves. We find outstanding similarities of meteorological patterns associated with the positive NAFDI and the SHL West-phase on the one hand, and with the negative NAFDI and the SHL East-Phase, on the other hand. We introduce the daily NAFDI index and the daily SHL West-East Displacement Index (SHLWEDI). The Pearson correlation coefficient between the daily SHLWEDI 1-day lagged and the daily NAFDI for the period 1980–2013 20 June–17 September is fairly high (r = 0.77). The correlation reduces to 0.69 if the SHLWEDI is not lagged. We observe that the SHL West-phase is significantly more frequent than the SHL East-phase, and that the SHL is more intense during its East-phase. We find positive aerosol optical depth (AOD) anomalies in the Western Sahara during positive NAFDI/SHL West-phase, and negative AOD anomalies in the central and eastern Sahara during negative NAFDI/SHL East-phase. A significant positive (negative) NE-SW axis AOD anomaly over the Subtropical North Atlantic for positive (negative) NAFDI is found. Remarkable patterns of positive (negative) AOD anomalies over the tropical Atlantic and the Central-Western Mediterranean during negative (positive) NAFDI are observed. The impact of mid-latitude Rossby waves on NAFDI variations depends on both the amplitude and phase of the Rossby wave at 200–300 hPa, which is quantified in this study by the daily Zonal Wind Anomaly at 300 hPa over South Morocco (ZWA300), and the penetration of the Rossby wave into the lower troposphere, quantified by the daily Omega at 500 hPa over Northwest Algeria (O500). The correlation of both ZWA300 and O500 with NAFDI is significant: 0.48 and 0.53, respectively, when we apply 5-day running means to the time series before calculating the correlation coefficients, and increases to 0.66 when a multi-linear regression is performed. The results suggest that ZWA300 drives almost one day in advance the NAFDI, whereas O500 might be ahead respect to NAFDI less than 12 hours. The power spectra of the NAFDI, SHL, ZWA300 and O500 times series in the intermediate time scale range (between 10 and 30 days) show 10 especially intense NAFDI spectral peaks, most of them also present in the SHLWEDI spectrum, finding that for many of the NAFDI/SHLWEDI peaks there is associated an O500 and/or ZWA300 peak. Our results indicate that the modes of oscillation of both the NAFDI and the SHL are driven by those mid-latitudes Rossby waves that go deep enough into the lower troposphere imposing their perturbation to the background meteorological fields. A comprehensive top-down conceptual model is introduced to explain the relationships between the NAFDI, the SHL and the mid-latitude Rossby waves and their impact in dust mobilization and transport in Northern Africa.

scholarly journals Radon activity in the lower troposphere and its impact on ionization rate: a global estimate using different radon emissions

2011 ◽  
Vol 11 (15) ◽  
pp. 7817-7838 ◽  
Author(s):  
K. Zhang ◽  
J. Feichter ◽  
J. Kazil ◽  
H. Wan ◽  
W. Zhuo ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Radioactive Decay ◽  
Lower Troposphere ◽  
Atmospheric Model ◽  
Ionization Rate ◽  
Aerosol Size Distribution ◽  
High Concentration ◽  
Near Surface ◽  
Global Estimate ◽  
The Impact

Abstract. The radioactive decay of radon and its progeny can lead to ionization of air molecules and consequently influence aerosol size distribution. In order to provide a global estimate of the radon-related ionization rate, we use the global atmospheric model ECHAM5 to simulate transport and decay processes of the radioactive tracers. A global radon emission map is put together using regional fluxes reported recently in the literature. Near-surface radon concentrations simulated with this new map compare well with measurements. Radon-related ionization rate is calculated and compared to that caused by cosmic rays. The contribution of radon and its progeny clearly exceeds that of the cosmic rays in the mid- and low-latitude land areas in the surface layer. During cold seasons, at locations where high concentration of sulfuric acid gas and low temperature provide potentially favorable conditions for nucleation, the coexistence of high ionization rate may help enhance the particle formation processes. This suggests that it is probably worth investigating the impact of radon-induced ionization on aerosol-climate interaction in global models.

scholarly journals Organic pollutants from Indonesian peatland fires: regional influences and its impact on lower the stratospheric composition

2021 ◽  
Author(s):  
Simon Rosanka ◽  
Bruno Franco ◽  
Lieven Clarisse ◽  
Pierre-François Coheur ◽  
Andreas Wahner ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Lower Troposphere ◽  
Atmospheric Model ◽  
Chemical Production ◽  
Global Atmospheric Model ◽  
Reservoir Species ◽  
Upward Transport ◽  
High Concentrations ◽  
Stratospheric Composition ◽  
The Impact

<p>In 2015, the particularly strong dry season in Indonesia, caused by an exceptional strong El Niño, led to severe peatland fires. Due to the high carbon content of peatland, these fires are characterised by high volatile organic compound (VOC) biomass burning emissions. The resulting primary and secondary pollutants are efficiently transported to the upper troposphere/lower stratosphere (UTLS) by the developing Asian monsoon anticyclone (ASMA) and the general upward transport in the intertropical convergence zone (ITCZ). In this study, we assess the importance of these VOC emissions for the composition of the lower troposphere and the UTLS by performing multiple chemistry simulations using the global atmospheric model ECHAM/MESSy (EMAC). In a first step, we find that EMAC properly captures the exceptional strength of the Indonesian fires based on the comparison of modelled columns of the biomass burning marker hydrogen cyanide (HCN) to spaceborne measurements from the Infrared Atmospheric Sounding Interferometer (IASI). In the lower troposphere, the increase in VOC levels is higher in Indonesia compared to other biomass burning regions. This directly impacts the oxidation capacity and leads to a high reduction in hydroxyl radicals (OH) and nitrogen oxides (NO<sub>x</sub>). In general, an increase in ozone (O<sub>3</sub>) is predicted close to the peatland fires. However, particular high concentrations of phenols lead to an O<sub>3</sub> depletion in eastern Indonesia. By employing the detailed in-cloud OVOC oxidation scheme Jülich Aqueous-phase Mechanism of Organic Chemistry (JAMOC), we find that the predicted changes are dampened and that by ignoring these processes, global models tend to overestimate the impact of such extreme pollution events. The upward transport in the ASMA and the ITCZ leads to elevated VOC concentrations in the UTLS region. This also results in a depletion of lower stratospheric O<sub>3</sub>. We find that this is caused by a high destruction of O<sub>3</sub> by phenoxy radicals and by the increased formation of NO<sub>x</sub> reservoir species, which dampen the chemical production of O<sub>3</sub>.</p>

scholarly journals A 10 km North American Precipitation and Land Surface Reanalysis Based on the GEM Atmospheric Model

2021 ◽  
Author(s):  
Nicolas Gasset ◽  
Vincent Fortin ◽  
Milena Dimitrijevic ◽  
Marco Carrera ◽  
Bernard Bilodeau ◽  
...  
Keyword(s):  
North American ◽  
Land Surface ◽  
Lower Troposphere ◽  
Summer Precipitation ◽  
Atmospheric Model ◽  
Dew Point ◽  
Land Data Assimilation ◽  
Precipitation Analysis ◽  
Land Data Assimilation System ◽  
The Impact

Abstract. Environment and Climate Change Canada has initiated the production of a 1980–2018, 10 km, North American precipitation and surface reanalysis. ERA-Interim is used to initialize the Global Deterministic Reforecast System (GDRS) at a 39 km resolution. Its output is then dynamically downscaled to 10 km by the Regional Deterministic Reforecast System (RDRS). Coupled with the RDRS, the Canadian Land Data Assimilation System (CaLDAS) and Precipitation Analysis (CaPA) are used to produce surface and precipitation analyses. All systems used are close to operational model versions and configurations. In this study, a 7-year sample of the reanalysis (2011–2017) is evaluated. Verification results show that the skill of the RDRS is stable over time, and equivalent to that of the current operational system. The impact of the coupling between RDRS and CaLDAS is explored using an early version of the reanalysis system which was run at 15 km resolution for the period 2010–2014, with and without the use of CaLDAS. Significant improvements are observed with CaLDAS in the lower troposphere and surface layer, especially for the 850 hPa dew point and absolute temperatures in summer. Precipitation is further improved through an offline precipitation analysis which allows the assimilation of additional observations of 24-h precipitation totals. The final dataset should be of particular interest for hydrological applications focusing on trans-boundary and northern watersheds, where existing products often show discontinuities at the border and assimilate very few – if any – precipitation observations.

scholarly journals The impact of extreme climate change on the fluctuation of electricity energy demand——Evidence from China's prefecture-level cities

2021 ◽  
Vol 260 ◽  
pp. 01014
Author(s):  
Yudong Tan ◽  
Tong Jiang ◽  
Hao Xiao ◽  
Jingyi Tang ◽  
Zhen Jia
Keyword(s):  
Climate Change ◽  
High Temperature ◽  
Low Temperature ◽  
Energy Demand ◽  
Electricity Demand ◽  
Extreme Climate ◽  
Extreme High Temperature ◽  
Residential Electricity ◽  
Negative Effect ◽  
The Impact

Climate change directly make the demand for electricity diversified and uncertain, which increase the risk of power grid operation. This paper attempts to explore the impact of extreme climate change on the fluctuation of China's electricity energy demand from the perspective of climate change. Based on the panel data of 90 prefecture-level cities in China from 1989 to 2017, the author builds an econometric model to test the impact of extreme low temperature and extreme high temperature on electricity demand. The results show that the occurrence of extreme high temperature weather has a positive effect on residential electricity demand while the emergence of extreme low temperature weather has a negative effect.

Linking the variability of PM10 in Europe to the position of the extratropical jet

2020 ◽  
Author(s):  
Carlos Ordóñez ◽  
Jose M. Garrido-Perez ◽  
Ricardo García-Herrera ◽  
David Barriopedro
Keyword(s):  
Central Europe ◽  
North Atlantic ◽  
Lower Troposphere ◽  
Time Lags ◽  
Southern Europe ◽  
Near Surface ◽  
Mean Values ◽  
Future Evolution ◽  
The Mean ◽  
The Impact

<p>We have investigated the impact of the polar jet on the winter PM<sub>10</sub> (particulate matter with aerodynamic diameter ≤ 10 μm) concentrations in Europe during a 10-year period. For this purpose, we have computed the daily latitude and strength of the jet by using reanalysis wind fields in the lower troposphere over the eastern North Atlantic (0°–15° W). Then we have extracted daily average surface PM<sub>10</sub> observations at ~440 sites from the European air quality database (AirBase).</p><p>Four preferred jet positions have been identified over the 0°–15° W sector in winter: southern (south of 41° N), central-southern (between 41° N and 51° N), central-northern (between 51° N and 63° N) and northern (north of 63° N). They exert a stronger influence than the jet strength on the mean PM<sub>10</sub> levels. Consequently, we have examined whether the full distribution of PM<sub>10</sub> and the occurrence of PM<sub>10</sub> extremes (exceedances of the local winter 95th percentiles) are also linked to the jet position.</p><p>The northern position is associated with enhanced PM<sub>10</sub> concentrations (on average ~9 μg m<sup>−3</sup> above the mean values) and threefold increases in the odds of PM<sub>10</sub> extremes over northwestern / central Europe. Comparable increases have been found in southern Europe when the jet is in its central-northern position. In both cases, the rise in the PM<sub>10</sub> concentrations is associated with blocking of the zonal flow over those regions and the impact on PM<sub>10</sub> extremes is maximised for time lags of around 1–2 days. On the other hand, the mean sea level pressure (SLP) patterns of the central-southern jet position resemble a positive phase of the winter North Atlantic Oscillation (NAO), yielding large PM<sub>10</sub> decreases (on average around −9 μg m<sup>−3</sup>) in northwestern / central Europe. Similarly, the southern jet position results in low PM<sub>10</sub> concentrations in southern Europe.</p><p>These results demonstrate that winter near-surface PM<sub>10</sub> concentrations in Europe are strongly sensitive to the jet latitude, with implications for future projections of air pollution. As there is no consensus on the future evolution of the North Atlantic jet in a warming climate, different responses among model simulations could be relevant to understand discrepancies in their climate change projections of PM<sub>10</sub> and other pollutants.</p>

The Continuum and Dynamics of Northern Hemisphere Teleconnection Patterns

2005 ◽  
Vol 62 (9) ◽  
pp. 3250-3267 ◽  
Author(s):  
Christian Franzke ◽  
Steven B. Feldstein
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
North Pacific ◽  
Low Frequency ◽  
Longwave Radiation ◽  
Alternative Interpretation ◽  
Basis Functions ◽  
Teleconnection Patterns ◽  
The Impact ◽  
The Continuum

Abstract This study presents an alternative interpretation for Northern Hemisphere teleconnection patterns. Rather than comprising several different recurrent regimes, this study suggests that there is a continuum of teleconnection patterns. This interpretation indicates either that 1) all members of the continuum can be expressed in terms of a linear combination of a small number of real physical modes that correspond to basis functions or 2) that most low-frequency patterns within the continuum are real physical patterns, each having its own spatial structure and frequency of occurrence. Daily NCEP–NCAR reanalysis data are used that cover the boreal winters of 1958–97. A set of nonorthogonal basis functions that span the continuum is derived. The leading basis functions correspond to well-known patterns such as the Pacific–North American teleconnection and North Atlantic Oscillation. Evidence for the continuum perspective is based on the finding that 1) most members of the continuum tend to have similar variance and autocorrelation time scales and 2) that members of the continuum show dynamical characteristics that are intermediate between those of the surrounding basis functions. The latter finding is obtained by examining the streamfunction tendency equation both for the basis functions and some members of the continuum. The streamfunction tendency equation analysis suggests that North Pacific patterns (basis functions and continuum) are primarily driven by their interaction with the climatological stationary eddies and that North Atlantic patterns are primarily driven by transient eddy vorticity fluxes. The decay mechanism for all patterns is similar, being due to the impact of low-frequency (period greater than 10 days) transient eddies and horizontal divergence. Analysis with outgoing longwave radiation shows that tropical convection is found to play a much greater role in exciting North Pacific patterns. A plausible explanation for these differences between the North Atlantic and North Pacific patterns is presented.

scholarly journals Strong Dependence of Wintertime Arctic Moisture and Cloud Distributions on Atmospheric Large-Scale Circulation

2019 ◽  
Vol 32 (24) ◽  
pp. 8771-8790 ◽  
Author(s):  
Tiina Nygård ◽  
Rune G. Graversen ◽  
Petteri Uotila ◽  
Tuomas Naakka ◽  
Timo Vihma
Keyword(s):  
North Atlantic ◽  
Moisture Transport ◽  
Large Scale ◽  
Strong Dependence ◽  
Longwave Radiation ◽  
The Arctic ◽  
Large Scale Circulation ◽  
The North ◽  
Downward Longwave Radiation ◽  
The Impact

Abstract This study gives a comprehensive picture of how atmospheric large-scale circulation is related to moisture transport and to distributions of moisture, clouds, and surface downward longwave radiation in the Arctic in winter. Anomaly distributions of the abovementioned variables are compared in 30 characteristic wintertime atmospheric circulation regimes, which are allocated from 15 years (2003–17) of mean sea level pressure data of ERA-Interim reanalysis applying the self-organizing map method. The characteristic circulation regimes are further related to known climate indices—the North Atlantic Oscillation (NAO), the Arctic Oscillation (AO), and Greenland blocking index—as well as to a frequent high pressure pattern across the Arctic Ocean from Siberia to North America, herein called the Arctic bridge. Effects of large-scale circulation on moisture, cloud, and longwave radiation are to a large extent occurring through the impact of horizontal moisture transport. Evaporation is typically not efficient enough to shape those distributions, and much of the moisture evaporated in the Arctic is transported southward. The positive phase of the NAO and AO increases moisture and clouds in northern Europe and the eastern North Atlantic Ocean, and a strong Greenland blocking typically increases those in the southwest of Greenland. When the Arctic bridge is lacking, the amount of moisture, clouds, and downward longwave radiation is anomalously high near the North Pole. Our results reveal a strong dependence of moisture, clouds, and longwave radiation on atmospheric pressure fields, which also appears to be important from a climate change perspective.

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