El Niño–Related Tropical Land Surface Water and Energy Response in MERRA-2

2020 ◽  
Vol 33 (3) ◽  
pp. 1155-1176 ◽  
Author(s):  
Michael G. Bosilovich ◽  
Franklin R. Robertson ◽  
Paul W. Stackhouse
Keyword(s):  
El Niño ◽  
Land Surface ◽  
Large Scale ◽  
El Nino ◽  
Lower Troposphere ◽  
Atmospheric Model ◽  
Forced Response ◽  
Shortwave Radiation ◽  
Tropical Regions ◽  
Surface Warming

AbstractAlthough El Niño events each have distinct evolutionary character, they typically provide systematic large-scale forcing for warming and increased drought frequency across the tropical continents. We assess this response in the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), reanalysis and in a 10-member-model Atmospheric Model Intercomparison Project (AMIP) ensemble. The lagged response (3–4 months) of mean tropical land temperature to El Niño warming in the Pacific Ocean is well represented. MERRA-2 reproduces the patterns of precipitation in the tropical regions, and the AMIP ensemble reproduces some regional responses that are similar to those observed and some regions that are not simulating the response well. Model skill is dependent on event forcing strength and temporal proximity to the peak of the sea surface warming. A composite approach centered on maximum Niño-3.4 SSTs and lag relationships to energy fluxes and transports is used to identify mechanisms supporting tropical land warming. The composite necessarily moderates weather-scale variability of the individual events while retaining the systematic features across all events. We find that reduced continental upward motions lead to reduced cloudiness and more shortwave radiation at the surface, as well as reduced precipitation. The increased shortwave heating at the land surface, along with reduced soil moisture, leads to warmer surface temperature, more sensible heating, and warming of the lower troposphere. The composite provides a broad picture of the mechanisms governing the hydrologic response to El Niño forcing, but the regional and temporal responses can vary substantially for any given event. The 2015/16 El Niño, one of the strongest events, demonstrates some of the forced response noted in the composite, but with shifts in the evolution that depart from the composite, demonstrating the limitations of the composite and individuality of El Niño.

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 Investigation of Aerosol Direct Effect over China under El Niño and Its Spatial Distribution Using WRF-Chem

Atmosphere ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 58
Author(s):  
Fangzhou Li ◽  
Wenshi Lin ◽  
Baolin Jiang ◽  
Jiangnan Li
Keyword(s):  
Direct Effect ◽  
El Niño ◽  
Large Scale ◽  
Water Cycle ◽  
El Nino ◽  
Shortwave Radiation ◽  
Aerosol Direct Effect ◽  
Aerosol Effect ◽  
Pollution Problem ◽  
Physical And Chemical

With rapid economic development and urbanization, the air pollution problem over China has drawn great attention. To explore the aerosol direct effect (ADE) over China, two simulations were conducted using WRF-Chem V3.5.1 in the summer of 2015. One was a control run (CTL) including aerosol effect and related physical and chemical processes, and the other one was a sensitivity simulation (SEN), the same as CTL except that aerosol-radiation interactions were turned off. The differences between two tests were analyzed, in particular over regions in South China (SC) and East China (EC). Results showed the following. (1) The large-scale circulation showed a strong El Niño signal, associated with cooling and wet anomalies over EC, while warming and dry anomalies over EC. (2) Due to ADE, there was a significant decrease in precipitation and an increase in AOD over SC and EC, albeit with different mechanisms. (3) In SC, ADE cooled the region reinforcing the El Niño impact and suppressing water vapor fluxes, which led to a more stable atmosphere and weakened water cycle. In EC, ADE caused vertical circulation anomalies opposing the El Niño impact. (4) ADE showed obvious land-sea difference in precipitation and shortwave radiation.

scholarly journals Positive relationship between seasonal Indo-Pacific Ocean wave power and SST

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sukhwinder Kaur ◽  
Prashant Kumar ◽  
Evan Weller ◽  
Ian R. Young
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Wave Power ◽  
Tropical Regions ◽  
Positive Indian Ocean Dipole ◽  
The Pacific ◽  
Sst Anomalies

AbstractThe influence of increasing sea surface temperatures (SSTs), in response to greenhouse warming, on wave power (WP) remains uncertain. Here, seasonal relationships between SST anomalies and mean and extreme WP over the Indo-Pacific Ocean are examined. Overall, seasonal WP has significantly increased over much of the Pacific, Indian, and Southern Ocean by 1.21–3.10 kW/m dec−1 over 1979–2019. Contributions from wave characteristics, namely significant wave height (SWH) and peak wave period (PWP), to changes in WP show that SWH contributes most in extra-tropical regions, and PWP most in tropical regions. Further, seasonal relationships between SST anomalies and WP indicate that increases in WP are also seen during strong El Niño years in December–February, and in-phase combinations of El Niño and positive Indian Ocean Dipole (IOD) events during June–August and September–November. Results highlight both long-term increasing SSTs and climate variability roles for inducing large-scale seasonal WP changes throughout the Indo-Pacific.

scholarly journals An Enhanced Moisture Convergence–Evaporation Feedback Mechanism for MJO Air–Sea Interaction

2008 ◽  
Vol 65 (3) ◽  
pp. 970-986 ◽  
Author(s):  
Andrew G. Marshall ◽  
Oscar Alves ◽  
Harry H. Hendon
Keyword(s):  
Large Scale ◽  
Lower Troposphere ◽  
Moisture Flux ◽  
Atmospheric Model ◽  
Ocean Model ◽  
Moisture Convergence ◽  
Shortwave Radiation ◽  
Subsequent Increase ◽  
Slab Ocean

Abstract Simulations using an atmospheric model forced with observed SST climatology and the same atmospheric model coupled to a slab-ocean model are used to investigate the role of air–sea interaction on the dynamics of the MJO. Slab-ocean coupling improved the MJO in Australia’s Bureau of Meteorology atmospheric model over the Indo-Pacific warm pool by reducing its period from 70–100 to 45–70 days, thereby showing better agreement with the 30–80-day observed oscillation. Air–sea coupling improves the MJO by increasing the moisture flux in the lower troposphere prior to the passage of active convection, which acts to promote convection and precipitation on the eastern flank of the main convective center. This process is triggered by an increase in surface evaporation over positive SST anomalies ahead of the MJO convection, which are driven by the enhanced shortwave radiation in the region of suppressed convection. This in turn generates enhanced convergence into the region, which supports evaporation–wind feedback in the presence of weak background westerly winds. A subsequent increase in low-level moisture convergence acts to further moisten the lower troposphere in advance of large-scale convection in a region of reduced atmospheric pressure. This destabilizing mechanism is referred to as enhanced moisture convergence–evaporation feedback (EMCEF) and is utilized to understand the role of air–sea coupling on the observed MJO. The EMCEF mechanism also reconciles traditionally opposing ideas on the roles of frictional wave–conditional instability of the second kind (CISK) and wind–evaporation feedback. These results support the idea that the MJO is primarily an atmospheric phenomenon, with air–sea interaction improving upon, but not critical for, its existence in the model.

scholarly journals Absorbing Aerosols and Summer Monsoon Evolution over South Asia: An Observational Portrayal

2008 ◽  
Vol 21 (13) ◽  
pp. 3221-3239 ◽  
Author(s):  
Massimo Bollasina ◽  
Sumant Nigam ◽  
K-M. Lau
Keyword(s):  
Summer Monsoon ◽  
Land Surface ◽  
Large Scale ◽  
Cloud Amount ◽  
Shortwave Radiation ◽  
Monsoon Circulation ◽  
Gangetic Plain ◽  
Surface Warming ◽  
Absorbing Aerosols

Abstract The South Asian haze builds up from December to May, is mostly of anthropogenic origin, and absorbs part of the solar radiation. The influence of interannual variations of absorbing aerosols over the Indo-Gangetic Plain in May on the Indian summer monsoon is characterized by means of an observational analysis. Insight into how the aerosol impact is generated is also provided. It is shown that anomalous aerosol loading in late spring leads to remarkable and large-scale variations in the monsoon evolution. Excessive aerosols in May lead to reduced cloud amount and precipitation, increased surface shortwave radiation, and land surface warming. The June (and July) monsoon anomaly associated with excessive May aerosols is of opposite sign over much of the subcontinent (although with a different pattern) with respect to May. The monsoon strengthens in June (and July). The analysis suggests that the significant large-scale aerosol influence on monsoon circulation and hydroclimate is mediated by the heating of the land surface, pursuant to reduced cloudiness and precipitation in May. The finding of the significant role of the land surface in the realization of the aerosol impact is somewhat novel.

scholarly journals Do biomass burning aerosols intensify drought in equatorial Asia during El Niño?

2010 ◽  
Vol 10 (8) ◽  
pp. 3515-3528 ◽  
Author(s):  
M. G. Tosca ◽  
J. T. Randerson ◽  
C. S. Zender ◽  
M. G. Flanner ◽  
P. J. Rasch
Keyword(s):  
El Niño ◽  
Land Surface ◽  
General Circulation ◽  
El Nino ◽  
Circulation Model ◽  
Radiation Budget ◽  
Shortwave Radiation ◽  
Fire Emissions ◽  
Surface Temperatures ◽  
Regional Drought

Abstract. During El Niño years, fires in tropical forests and peatlands in equatorial Asia create large regional smoke clouds. We characterized the sensitivity of these clouds to regional drought, and we investigated their effects on climate by using an atmospheric general circulation model. Satellite observations during 2000–2006 indicated that El Niño-induced regional drought led to increases in fire emissions and, consequently, increases in aerosol optical depths over Sumatra, Borneo and the surrounding ocean. Next, we used the Community Atmosphere Model (CAM) to investigate how climate responded to this forcing. We conducted two 30 year simulations in which monthly fire emissions were prescribed for either a high (El Niño, 1997) or low (La Niña, 2000) fire year using a satellite-derived time series of fire emissions. Our simulations included the direct and semi-direct effects of aerosols on the radiation budget within the model. We assessed the radiative and climate effects of anthropogenic fire by analyzing the differences between the high and low fire simulations. Fire aerosols reduced net shortwave radiation at the surface during August–October by 19.1±12.9 W m−2 (10%) in a region that encompassed most of Sumatra and Borneo (90° E–120° E, 5° S–5° N). The reductions in net shortwave radiation cooled sea surface temperatures (SSTs) and land surface temperatures by 0.5±0.3 and 0.4±0.2 °C during these months. Tropospheric heating from black carbon (BC) absorption averaged 20.5±9.3 W m−2 and was balanced by a reduction in latent heating. The combination of decreased SSTs and increased atmospheric heating reduced regional precipitation by 0.9±0.6 mm d−1 (10%). The vulnerability of ecosystems to fire was enhanced because the decreases in precipitation exceeded those for evapotranspiration. Together, the satellite and modeling results imply a possible positive feedback loop in which anthropogenic burning in the region intensifies drought stress during El Niño.

scholarly journals Do biomass burning aerosols intensify drought in equatorial Asia during El Niño?

2009 ◽  
Vol 9 (6) ◽  
pp. 23319-23348 ◽  
Author(s):  
M. G. Tosca ◽  
J. T. Randerson ◽  
C. S. Zender ◽  
M. G. Flanner ◽  
P. J. Rasch
Keyword(s):  
El Niño ◽  
Land Surface ◽  
General Circulation ◽  
El Nino ◽  
Circulation Model ◽  
Radiation Budget ◽  
Shortwave Radiation ◽  
Fire Emissions ◽  
Surface Temperatures ◽  
Regional Drought

Abstract. During El Niño years, fires in tropical forests and peatlands in equatorial Asia create large regional smoke clouds. We characterized the sensitivity of these clouds to regional drought, and we investigated their effects on climate by using an atmospheric general circulation model. Satellite observations during 2000–2006 indicated that El Niño-induced regional drought led to increases in fire emissions and, consequently, increases in aerosol optical depths over Sumatra, Borneo and the surrounding ocean. Next, we used the Community Atmosphere Model (CAM) to investigate how climate responded to this forcing. We conducted two 30 year simulations in which monthly fire emissions were prescribed for either a high (El Niño, 1997) or low (La Niña, 2000) fire year using a satellite-derived time series of fire emissions. Our simulations included the direct and semi-direct effects of aerosols on the radiation budget within the model. Fire aerosols reduced net shortwave radiation at the surface during August–October by 19.1±12.9 W m−2 (10%) in a region that encompassed most of Sumatra and Borneo (90° E–120° E, 5° S–5° N). The reductions in net radiation cooled sea surface temperatures (SSTs) and land surface temperatures by 0.5±0.3 and 0.4±0.2&deg C during these months. Tropospheric heating from black carbon (BC) absorption averaged 20.5±9.3 W m−2 and was balanced by a reduction in latent heating. The combination of decreased SSTs and increased atmospheric heating reduced regional precipitation by 0.9±0.6 mm d−1 (10%). The vulnerability of ecosystems to fire was enhanced because the decreases in precipitation exceeded those for evapotranspiration. Together, the satellite and modeling results imply a possible positive feedback loop in which anthropogenic burning in the region intensifies drought stress during El Niño.

scholarly journals Cities Exacerbate Climate Warming

Urban Science ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 27
Author(s):  
Lahouari Bounoua ◽  
Kurtis Thome ◽  
Joseph Nigro
Keyword(s):  
Surface Temperature ◽  
Land Surface ◽  
Large Scale ◽  
Climate Models ◽  
Warming Trend ◽  
Climate Mitigation ◽  
Temperature Changes ◽  
Surface Warming ◽  
The Us

Urbanization is a complex land transformation not explicitly resolved within large-scale climate models. Long-term timeseries of high-resolution satellite data are essential to characterize urbanization within land surface models and to assess its contribution to surface temperature changes. The potential for additional surface warming from urbanization-induced land use change is investigated and decoupled from that due to change in climate over the continental US using a decadal timescale. We show that, aggregated over the US, the summer mean urban-induced surface temperature increased by 0.15 °C, with a warming of 0.24 °C in cities built in vegetated areas and a cooling of 0.25 °C in cities built in non-vegetated arid areas. This temperature change is comparable in magnitude to the 0.13 °C/decade global warming trend observed over the last 50 years caused by increased CO2. We also show that the effect of urban-induced change on surface temperature is felt above and beyond that of the CO2 effect. Our results suggest that climate mitigation policies must consider urbanization feedback to put a limit on the worldwide mean temperature increase.

scholarly journals An Analysis of the Energetics of Tropical and Extra-Tropical Regions for Warm ENSO Composite Episodes

2017 ◽  
Vol 32 (1) ◽  
pp. 39-51
Author(s):  
Zayra Christine Sátyro ◽  
José Veiga
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
El Niño ◽  
Energy Production ◽  
El Nino ◽  
Southern Oscillation ◽  
Stable Condition ◽  
The Other ◽  
Tropical Regions ◽  
Using Data

Abstract This study focuses on the quantification and evaluation of the effects of ENSO (El Niño Southern Oscillation) warm phases, using a composite of five intense El Niño episodes between 1979 – 2011 on the Energetic Lorenz Cycle for four distinct regions around the globe: 80° S – 5° N (region 1), 50° S – 5° N (region 2), 30° S – 5° N (region 3), and 30° S – 30° N (region 4), using Data from NCEP reanalysis-II. Briefly, the results showed that zonal terms of potential energy and kinetic energy were intensified, except for region 1, where zonal kinetic energy weakened. Through the analysis of the period in which higher energy production is observed, a strong communication between the available zonal potential and the zonal kinetic energy reservoirs can be identified. This communication weakened the modes linked to eddies of potential energy and kinetic energy, as well as in the other two baroclinic conversions terms. Furthermore, the results indicate that for all the regions, the system itself works to regain its stable condition.

scholarly journals On the role of trend and variability in the hydroxyl radical (OH) in the global methane budget

2020 ◽  
Vol 20 (21) ◽  
pp. 13011-13022
Author(s):  
Yuanhong Zhao ◽  
Marielle Saunois ◽  
Philippe Bousquet ◽  
Xin Lin ◽  
Antoine Berchet ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Interannual Variations ◽  
Atmospheric Methane ◽  
Tropical Regions ◽  
Ch4 Emissions ◽  
Methane Budget

Abstract. Decadal trends and interannual variations in the hydroxyl radical (OH), while poorly constrained at present, are critical for understanding the observed evolution of atmospheric methane (CH4). Through analyzing the OH fields simulated by the model ensemble of the Chemistry–Climate Model Initiative (CCMI), we find (1) the negative OH anomalies during the El Niño years mainly corresponding to the enhanced carbon monoxide (CO) emissions from biomass burning and (2) a positive OH trend during 1980–2010 dominated by the elevated primary production and the reduced loss of OH due to decreasing CO after 2000. Both two-box model inversions and variational 4D inversions suggest that ignoring the negative anomaly of OH during the El Niño years leads to a large overestimation of the increase in global CH4 emissions by up to 10 ± 3 Tg yr−1 to match the observed CH4 increase over these years. Not accounting for the increasing OH trends given by the CCMI models leads to an underestimation of the CH4 emission increase by 23 ± 9 Tg yr−1 from 1986 to 2010. The variational-inversion-estimated CH4 emissions show that the tropical regions contribute most to the uncertainties related to OH. This study highlights the significant impact of climate and chemical feedbacks related to OH on the top-down estimates of the global CH4 budget.

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