scholarly journals Contrasting impacts of two types of El Niño events on winter haze days in China's Jing-Jin-Ji region

2020 ◽  
Vol 20 (17) ◽  
pp. 10279-10293
Author(s):  
Xiaochao Yu ◽  
Zhili Wang ◽  
Hua Zhang ◽  
Jianjun He ◽  
Ying Li
Keyword(s):  
El Niño ◽  
El Nino ◽  
Eastern China ◽  
Cp El Niño ◽  
Haze Pollution ◽  
Synoptic Conditions ◽  
El Niño Events ◽  
Ep El Niño ◽  
Haze Days ◽  
El Nino Events

Abstract. El Niño events differ widely in their patterns and intensities. The regional climate anomalies caused by different types of El Niño events likely lead to various impacts on winter haze pollution in China. Based on long-term site observations of haze days in China from 1961 to 2013, this study explores the effects of eastern Pacific (EP) and central Pacific (CP) types of El Niño events on the number of winter haze days (WHDs) in China's Jing-Jin-Ji (JJJ) region and the physical mechanisms underlying WHD changes. The results show statistically significant positive and negative correlations, respectively, between WHDs in the JJJ region and EP and CP El Niño events. At most sites in the JJJ region, the average WHD increased in all EP El Niño years, with the maximum change exceeding 2.0 d. Meanwhile, the average WHD decreased at almost all stations over this region in all CP El Niño years, with the largest change being more than −2.0 d. The changes in large-scale circulations indicate obvious positive surface air temperature (SAT) anomalies and negative sea level pressure (SLP) anomalies over North China, as well as southerly wind anomalies at the middle to low troposphere over eastern China in the winters of EP El Niño years. These anomalies are conducive to increases in WHDs in the JJJ region. However, there are significant northerly and northwesterly wind anomalies at the middle to low troposphere over eastern China, as well as stronger and wider precipitation anomalies in the winters of CP El Niño years, which contribute to decreased WHDs over the JJJ region. Changes in local synoptic conditions indicate negative SLP anomalies, positive SAT anomalies, and weakened northerly winds over the JJJ region in the winters of EP El Niño years. The total occurrence frequency of circulation types conducive to the accumulation (diffusion) of aerosol pollutants is increased (decreased) by 0.4 % (0.2 %) in those winters. However, the corresponding frequency is decreased (increased) by 0.5 % (0.6 %) in the winters of CP El Niño years. Our study highlights the importance of distinguishing the impacts of these two types of El Niño events on winter haze pollution in China's JJJ region.

scholarly journals Contrasting impacts of two types of El Niño events on winter haze days in China's Jing-Jin-Ji region

2020 ◽  
Author(s):  
Xiaochao Yu ◽  
Zhili Wang ◽  
Hua Zhang ◽  
Jianjun He ◽  
Ying Li
Keyword(s):  
El Niño ◽  
El Nino ◽  
Eastern China ◽  
Cp El Niño ◽  
El Niño Event ◽  
Haze Pollution ◽  
El Niño Events ◽  
Ep El Niño ◽  
Haze Days ◽  
El Nino Events

Abstract. El Niño is a complex system with diverse distribution features and intensities. The regional climate anomalies caused by different types of El Niño event likely lead to various impacts on winter haze pollution in China. Based on long-term site observations of haze days in China from 1961 to 2013, this study explores the effects of Eastern Pacific (EP) and Central Pacific (CP) types of El Niño event on winter haze days (WHD) in China's Jing-Jin-Ji (JJJ) region and the physical mechanisms underlying WHD changes. The results show statistically significant positive and negative correlations, respectively, between WHD in the JJJ region and EP and CP El Niño events. At most sites in the JJJ region, the average WHD are increased in all EP El Niño years, with the maximum change exceeding 2.0 days. Meanwhile the average WHD are decreased at almost all stations over this region in all CP El Niño years, with the largest change being more than −2.0 days. The changes in large-scale circulations indicate obviously positive surface air temperature (SAT) anomalies and negative sea level pressure (SLP) anomalies over North China, and southerly wind anomalies at the mid-low troposphere over eastern China in the winters of EP El Niño years. These anomalies are conducive to increases in WHD in the JJJ region. However, there are significant northerly and northwesterly wind anomalies at the mid-low troposphere over eastern China, and stronger and wider precipitation anomalies in the winters of CP El Niño years, which contribute to decreased WHD over the JJJ region. Changes in local synoptic conditions indicate negative SLP anomalies, positive SAT anomalies, and weakened northerly winds over the JJJ region in the winters of EP El Niño years. The occurrence frequency of circulation types conducive to the accumulation (diffusion) of aerosol pollutants is increased (decreased) by 0.4 % (0.37 %) in those winters. However, the corresponding frequency is decreased (increased) by 0.54 % (0.56 %) in the winters of CP El Niño years. Our study highlights the importance of distinguishing the impacts of two types of El Niño events on winter haze pollution in China's JJJ region.

scholarly journals Differences in the Initiation and Development of the Madden–Julian Oscillation over the Indian Ocean Associated with Two Types of El Niño

2017 ◽  
Vol 30 (4) ◽  
pp. 1397-1415 ◽  
Author(s):  
Pang-Chi Hsu ◽  
Ting Xiao
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Radiative Heating ◽  
Madden Julian Oscillation ◽  
Cp El Niño ◽  
El Niño Events ◽  
The Indian Ocean ◽  
Ep El Niño ◽  
El Nino Events

Abstract The influences of different types of Pacific warming, often classified as the eastern Pacific (EP) and central Pacific (CP) El Niño events, on Madden–Julian oscillation (MJO) activity over the Indian Ocean were investigated. Accompanied by relatively unstable (stable) atmospheric stratification induced by enhanced (reduced) moisture and moist static energy (MSE) in the lower troposphere, strengthened (weakened) MJO convection was observed in the initiation and eastward-propagation stages during CP (EP) El Niño events. To examine the key processes resulting in the differences in low-level moistening and column MSE anomalies over the Indian Ocean associated with the two types of El Niño, the moisture and column MSE budget equations were diagnosed using the reanalysis dataset ERA-Interim. The results indicate that the enhanced horizontal advection in the CP El Niño years plays an important role in causing a larger moisture and MSE growth rate over the MJO initiation area during CP El Niño events than during EP El Niño events. The increases in horizontal moisture and MSE advection primarily result from advection by mean flow across the enhanced intraseasonal moisture and MSE gradient, as well as by intraseasonal circulation across the mean moisture and MSE gradient associated with the CP El Niño. In the eastward development stage, the enhanced preconditioning comes from positive moisture and MSE advection anomalies in the CP El Niño events. Meanwhile, the strengthened MJO-related convection over the central-eastern Indian Ocean is maintained by increased atmospheric radiative heating and surface latent heat flux during the CP El Niño compared to the EP El Niño events.

scholarly journals Impact of two different types of El Niño events on runoff over the conterminous United States

2015 ◽  
Vol 12 (9) ◽  
pp. 8977-9002
Author(s):  
T. Tang ◽  
W. Li ◽  
G. Sun
Keyword(s):  
Water Resource ◽  
El Niño ◽  
El Nino ◽  
Cmip5 Models ◽  
Great Loss ◽  
Cp El Niño ◽  
Different Types ◽  
El Niño Events ◽  
Ep El Niño ◽  
El Nino Events

Abstract. The responses of river runoff to shifts of large-scale climatic patterns are of increasing concerns to water resource planners and managers for long-term climate change adaptation. El Niño is one of the most dominant modes of climate variability that is closely linked to hydrologic extremes such as floods and droughts that cause great loss of lives and properties. However, the different impacts of the two types of El Niño-Central Pacific (CP) and Eastern Pacific (EP)-El Niño on runoff across the conterminous US (CONUS) are not well understood. This study characterizes the impacts of the CP- and EP-El Niño on seasonal and annual runoff using observed historical streamflow data from 658 reference gaging stations and NCAR-CCSM4 model. We found that surface runoff responds similarly to the two types of El Niño events in Southeast, Central, South and Western coastal regions, but differently in Northeast (NE), Pacific Northwest (PNW) and West North Central (WNC) climatic zones. Specifically, EP-El Niño events tend to bring above-average runoff in NE, WNC, and PNW throughout the year while CP-El Niño events cause below-than normal runoff in the three regions. Similar findings were also found by analyzing NCAR-CCSM4 model outputs that captured both the CP- and EP-El Niño events representing the best datasets among selected CMIP5 models. The CCSM4 model simulates lower runoff values during CP-El Niño years than those in EP-El Niño in all of the three climatic regions (NE, PNW and WNC) during 1950–1999. In the future (2050–2099), for both types of El Niño years, runoff is projected to increase over the NE and PNW regions, mainly due to increased precipitation (P). In contrast, the increase of future evapotranspiration (ET) is higher than that of future P, leading to a projected decrease in runoff over the WNC region. In addition, model analysis indicates that all of the three regions (NE, PNW and WNC) are projected to have lower runoff values during CP-El Niño years than EP-El Niño. Our study suggests that US water resources may be distributed more unevenly in space and time with more frequent and intense flood and drought events. The findings from this study have important implications to water resource management at the regional scale. Information generated from this study is useful for water resource planners to anticipate the influence of two different types of El Niño events on droughts and floods across the CONUS.

scholarly journals Intensified modulation of winter aerosol pollution in China by El Niño with short duration

2021 ◽  
Vol 21 (13) ◽  
pp. 10745-10761
Author(s):  
Liangying Zeng ◽  
Yang Yang ◽  
Hailong Wang ◽  
Jing Wang ◽  
Jing Li ◽  
...  
Keyword(s):  
Short Duration ◽  
El Niño ◽  
El Nino ◽  
Eastern China ◽  
Northeastern China ◽  
Aerosol Pollution ◽  
El Niño Events ◽  
Central Eastern ◽  
Haze Days ◽  
El Nino Events

Abstract. El Niño–Southern Oscillation (ENSO), a phenomenon of periodic changes in sea surface temperature in the equatorial central-eastern Pacific Ocean, is the strongest signal of interannual variability in the climate system with a quasi-period of 2–7 years. El Niño events have been shown to have important influences on meteorological conditions in China. In this study, the impacts of El Niño with different durations on aerosol concentrations and haze days during December–January–February (DJF) in China are quantitatively examined using the state-of-the-art Energy Exascale Earth System Model version 1 (E3SMv1). We find that PM2.5 concentrations are increased by 1–2 µg m−3 in northeastern and southern China and decreased by up to 2.4 µg m−3 in central-eastern China during El Niño events relative to the climatological means. Compared to long-duration (LD) El Niño events, El Niño with short duration (SD) but strong intensity causes northerly wind anomalies over central-eastern China, which is favorable for aerosol dispersion over this region. Moreover, the anomalous southeasterly winds weaken the wintertime prevailing northwesterly in northeastern China and facilitate aerosol transport from southern and southeast Asia, enhancing aerosol increase in northeastern China during SD El Niño events relative to LD El Niño events. In addition, the modulation effect on haze days by SD El Niño events is 2–3 times more than that by LD El Niño events in China. The aerosol variations during El Niño events are mainly controlled by anomalous aerosol accumulation/dispersion and transport due to changes in atmospheric circulation, while El Niño-induced precipitation change has little effect. The occurrence frequency of SD El Niño events has been increasing significantly in recent decades, especially after the 1940s, suggesting that El Niño with short duration has exerted an increasingly intense modulation on aerosol pollution in China over the past few decades.

scholarly journals Northern Hemisphere Stratospheric Pathway of Different El Niño Flavors in Stratosphere-Resolving CMIP5 Models

2017 ◽  
Vol 30 (12) ◽  
pp. 4351-4371 ◽  
Author(s):  
N. Calvo ◽  
M. Iza ◽  
M. M. Hurwitz ◽  
E. Manzini ◽  
C. Peña-Ortiz ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
El Niño ◽  
El Nino ◽  
Cmip5 Models ◽  
Eastern Canada ◽  
Central Pacific ◽  
Cp El Niño ◽  
El Niño Events ◽  
Ep El Niño ◽  
El Nino Events

The Northern Hemisphere (NH) stratospheric signals of eastern Pacific (EP) and central Pacific (CP) El Niño events are investigated in stratosphere-resolving historical simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), together with the role of the stratosphere in driving tropospheric El Niño teleconnections in NH climate. The large number of events in each composite addresses some of the previously reported concerns related to the short observational record. The results shown here highlight the importance of the seasonal evolution of the NH stratospheric signals for understanding the EP and CP surface impacts. CMIP5 models show a significantly warmer and weaker polar vortex during EP El Niño. No significant polar stratospheric response is found during CP El Niño. This is a result of differences in the timing of the intensification of the climatological wavenumber 1 through constructive interference, which occurs earlier in EP than CP events, related to the anomalous enhancement and earlier development of the Pacific–North American pattern in EP events. The northward extension of the Aleutian low and the stronger and eastward location of the high over eastern Canada during EP events are key in explaining the differences in upward wave propagation between the two types of El Niño. The influence of the polar stratosphere in driving tropospheric anomalies in the North Atlantic European region is clearly shown during EP El Niño events, facilitated by the occurrence of stratospheric summer warmings, the frequency of which is significantly higher in this case. In contrast, CMIP5 results do not support a stratospheric pathway for a remote influence of CP events on NH teleconnections.

scholarly journals Impact of two different types of El Niño events on runoff over the conterminous United States

2016 ◽  
Vol 20 (1) ◽  
pp. 27-37 ◽  
Author(s):  
T. Tang ◽  
W. Li ◽  
G. Sun
Keyword(s):  
Water Resource ◽  
El Niño ◽  
El Nino ◽  
Cmip5 Models ◽  
Great Loss ◽  
Cp El Niño ◽  
Different Types ◽  
El Niño Events ◽  
Ep El Niño ◽  
El Nino Events

Abstract. The responses of river runoff to shifts of large-scale climatic patterns are of increasing concerns to water resource planners and managers for long-term climate change adaptation. El Niño, as one of the most dominant modes of climate variability, is closely linked to hydrologic extremes such as floods and droughts that cause great loss of lives and properties. However, the different impacts of the two types of El Niño, i.e., central Pacific (CP-) and eastern Pacific (EP-)El Niño, on runoff across the conterminous US (CONUS) are not well understood. This study characterizes the impacts of the CP- and EP-El Niño on seasonal and annual runoff using observed streamflow data from 658 reference gaging stations and the NCAR-CCSM4 model. We found that surface runoff responds similarly to the two types of El Niño events in southeastern, central, southern, and western coastal regions, but differently in northeast (NE), Pacific northwest (PNW) and west north central (WNC) climatic zones. Specifically, EP-El Niño events tend to bring above-average runoff in NE, WNC, and PNW throughout the year while CP-El Niño events cause below-than normal runoff in the three regions. Similar findings were also found by analyzing NCAR-CCSM4 model outputs that captured both the CP- and EP-El Niño events, representing the best data set among CMIP5 models. The CCSM4 model simulates lower runoff values during CP-El Niño years than those in EP-El Niño over all of the three climatic regions (NE, PNW, and WNC) during 1950–1999. In the future (2050–2099), for both types of El Niño years, runoff is projected to increase over the NE and PNW regions, mainly due to increased precipitation (P). In contrast, the increase of future evapotranspiration (ET) exceeds that of future P, leading to a projected decrease in runoff over the WNC region. In addition, model analysis indicates that all of the three regions (NE, PNW, and WNC) are projected to have lower runoff in CP-El Niño years than in EP-El Niño years. Our study suggests that the US water resources may be distributed more unevenly in space and time with more frequent and intense flood and drought events. The findings from this study have important implications to water resource management at regional scales. Information generated from this study may help water resource planners to anticipate the influence of two different types of El Niño events on droughts and floods across the CONUS.

scholarly journals Intensified modulation of aerosol pollution in China by El Niño with short duration

2021 ◽  
Author(s):  
Liangying Zeng ◽  
Yang Yang ◽  
Hailong Wang ◽  
Jing Wang ◽  
Jing Li ◽  
...  
Keyword(s):  
Short Duration ◽  
El Niño ◽  
El Nino ◽  
Eastern China ◽  
Northeastern China ◽  
Aerosol Pollution ◽  
El Niño Events ◽  
Central Eastern ◽  
Haze Days ◽  
El Nino Events

Abstract. El Niño-Southern Oscillation (ENSO), a phenomenon of periodic changes in sea surface temperature in the equatorial central eastern Pacific Ocean, is the strongest signal of interannual variability in the climate system with a quasi-period of 2–7 years. El Niño events have been shown to have important influences on meteorological conditions in China. In this study, the impacts of El Niño with different durations on aerosol concentrations and haze days during December-January-February (DJF) in China are quantitatively examined using the state-of-the-science Energy Exascale Earth System Model version 1 (E3SMv1). We find that PM2.5 concentrations are increased by 1–2 µg m−3 in the northeastern and southern China and decreased by up to 2.4 µg m−3 in central-eastern China during El Niño events relative to the climatological means. Compared to long duration (LD) El Niño events, El Niño with short duration (SD) but strong intensity causes northerly wind anomalies over central-eastern China, which is favorable for aerosol dispersion over this region. Moreover, the anomalous southeasterly winds weaken the wintertime prevailing northwesterly in northeastern China and facilitate aerosol transport from South and Southeast Asia, enhancing aerosol increase in northeastern China during SD El Niño events relative to LD El Niño events. In addition, the modulation on haze days by SD El Niño events is 2–3 times more than that by LD El Niño events in China. The aerosol variations during El Niño events are mainly controlled by anomalous aerosol accumulation/dispersion and transport due to changes in atmospheric circulation, while El Niño-induced precipitation change has little effect. The occurrence frequency of SD El Niño events has been increasing significantly in recent decades, especially after 1940s, suggesting that El Niño with short duration have exerted increasingly intense modulation on aerosol pollution in China over the past few decades.

scholarly journals Examining the sensitivity of the terrestrial carbon cycle to the expression of El Niño

2020 ◽  
Author(s):  
Lina Teckentrup ◽  
Martin G. De Kauwe ◽  
Andrew J. Pitman ◽  
Benjamin Smith
Keyword(s):  
Carbon Cycle ◽  
El Niño ◽  
El Nino ◽  
Terrestrial Carbon ◽  
Near Surface ◽  
Terrestrial Carbon Cycle ◽  
El Niño Events ◽  
Ep El Niño ◽  
The Impact ◽  
El Nino Events

Abstract. The El Niño‐Southern Oscillation (ENSO) influences the global climate and the variability in the terrestrial carbon cycle on interannual timescales. Two different expressions of El Niño have recently been identified: (i) Central–Pacific (CP) and (ii) Eastern–Pacific (EP). Both types of El Nino are characterised by above average sea surface temperature anomalies in the respective locations. Studies exploring the impact of these expressions of El Niño on the carbon cycle have identified changes in the amplitude of the concentration of interannual atmospheric carbon dioxide (CO2) variability, as well as different lags in terrestrial CO2 release to the atmosphere following increased tropical near surface air temperature. We employ the dynamic global vegetation model LPJ–GUESS within a synthetic experimental framework to examine the sensitivity and potential long term impacts of these two expressions of El Niño on the terrestrial carbon cycle. We manipulated the occurrence of CP and EP events in two climate reanalysis datasets during the later half of the 20th and early 21st century by replacing all EP with CP and separately all CP with EP El Niño events. We found that the different expressions of El Niño affect interannual variability in the terrestrial carbon cycle. However, the effect on longer timescales was negligible for both climate reanalysis datasets. We conclude that capturing any future trends in the relative frequency of CP and EP El Niño events may not be critical for robust simulations of the terrestrial carbon cycle.

scholarly journals Examining the sensitivity of the terrestrial carbon cycle to the expression of El Niño

2021 ◽  
Vol 18 (6) ◽  
pp. 2181-2203
Author(s):  
Lina Teckentrup ◽  
Martin G. De Kauwe ◽  
Andrew J. Pitman ◽  
Benjamin Smith
Keyword(s):  
Carbon Cycle ◽  
El Niño ◽  
El Nino ◽  
Terrestrial Carbon ◽  
Near Surface ◽  
Terrestrial Carbon Cycle ◽  
El Niño Events ◽  
Ep El Niño ◽  
The Impact ◽  
El Nino Events

Abstract. The El Niño‐-Southern Oscillation (ENSO) influences the global climate and the variability in the terrestrial carbon cycle on interannual timescales. Two different expressions of El Niño have recently been identified: (i) central Pacific (CP) and (ii) eastern Pacific (EP). Both types of El Niño are characterised by above-average sea surface temperature anomalies at the respective locations. Studies exploring the impact of these expressions of El Niño on the carbon cycle have identified changes in the amplitude of the concentration of interannual atmospheric carbon dioxide (CO2) variability following increased tropical near-surface air temperature and decreased precipitation. We employ the dynamic global vegetation model LPJ-GUESS (Lund–Potsdam–Jena General Ecosystem Simulator) within a synthetic experimental framework to examine the sensitivity and potential long-term impacts of these two expressions of El Niño on the terrestrial carbon cycle. We manipulated the occurrence of CP and EP events in two climate reanalysis datasets during the latter half of the 20th and early 21st century by replacing all EP with CP and separately all CP with EP El Niño events. We found that the different expressions of El Niño affect interannual variability in the terrestrial carbon cycle. However, the effect on longer timescales was small for both climate reanalysis datasets. We conclude that capturing any future trends in the relative frequency of CP and EP El Niño events may not be critical for robust simulations of the terrestrial carbon cycle.

scholarly journals Contrasting behaviors of the atmospheric CO<sub>2</sub> interannual variability during two types of El Niños

2018 ◽  
Author(s):  
Jun Wang ◽  
Ning Zeng ◽  
Meirong Wang ◽  
Fei Jiang ◽  
Jingming Chen ◽  
...  
Keyword(s):  
Interannual Variability ◽  
El Niño ◽  
El Nino ◽  
Ecosystem Respiration ◽  
Atmospheric Co2 ◽  
Occurrence Rate ◽  
Central Pacific ◽  
Cp El Niño ◽  
El Niño Events ◽  
El Nino Events

Abstract. El Niño has two different flavors: eastern Pacific (EP) and central Pacific (CP) El Niños, with different global teleconnections. However, their different impacts on carbon cycle interannual variability remain unclear. We here compared the behaviors of the atmospheric CO2 interannual variability and analyzed their terrestrial mechanisms during these two types of El Niños, based on Mauna Loa (MLO) CO2 growth rate (CGR) and Dynamic Global Vegetation Models (DGVMs) historical simulations. Composite analysis shows that evolutions of MLO CGR anomaly have three clear differences in terms of (1) negative and neutral precursors in boreal spring of El Niño developing years (denoted as “yr0”), (2) strong and weak amplitudes, and (3) durations of peak from December (yr0) to April of El Niño decaying year (denoted as “yr1”) and from October (yr0) to January (yr1) during EP and CP El Niños, respectively. Models simulated global land–atmosphere carbon flux (FTA) is able to capture the essentials of these characteristics. We further find that the gross primary productivity (GPP) over the tropics and extratropical southern hemisphere (Trop+SH) generally dominates the global FTA variations during both El Niño types. Regionally, significant anomalous carbon uptake caused by more precipitation and colder temperature, corresponding to the negative precursor, occurs between 30° S and 20° N from January (yr0) to June (yr0), while the strongest anomalous carbon releases, due largely to the reduced GPP induced by low precipitation and warm temperature, happen between equator and 20° N from February (yr1) to August (yr1) during EP El Niño events. In contrast, during CP El Niño events, clear carbon releases exist between 10° N and 20° S from September (yr0) to September (yr1), resulted from the widespread dry and warm climate conditions. Different spatial patterns of land temperature and precipitation in different seasons associated with EP and CP El Niños account for the characteristics in evolutions of GPP, terrestrial ecosystem respiration (TER), and resultant FTA. Understanding these different behaviors of the atmospheric CO2 interannual variability along with their terrestrial mechanisms during EP and CP El Niños is important because CP El Niño occurrence rate might increase under global warming.

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