Accelerated Historical and Future Warming in the Middle East and North Africa, 2024
The present study assesses the climate of the Middle East and North Africa (MENA) in detail, focu... more The present study assesses the climate of the Middle East and North Africa (MENA) in detail, focusing on the historical and future warming trends in the region. The assessment incorporates data from observations, reanalyses, and statistically downscaled climate models from the Coupled Model Intercomparison Project Phases 5 and 6. Since the pre-industrial era, the observed average climate in the MENA has warmed by 1.5°C and is on the brink of exceeding 2°C. The reanalysis data suggest that the regional warming over some MENA sub-regions is three times faster than the global average. By the end of the 21st century, the Arabian Peninsula is projected to warm to 2.6°C ± 0.57°C and 7.6°C ± 1.53°C under low and high greenhouse gas emission scenarios, respectively. Distinct warming hotspots emerge over the Arabian Peninsula and Algeria in summer and over Mauritania in West Africa and the Elburz Mountains in Iran in winter. The summer hotspot over the Arabian Peninsula has already warmed by more than 2°C and can potentially warm to approximately 9°C under the high-emission scenario. As global warming progresses to 1.5, 2.0, 3.0, and 4.0°C, the average temperature over the MENA land is projected to increase by 2.3°C ± 0.18°C, 3.0°C ± 0.22°C, 4.6°C ± 0.26°C, and 6.1°C ± 0.31°C, respectively. The 1.5, 2.0, 3.0, and 4.0°C warming levels over the MENA are expected to predate those of the global mean by two or three decades. Natural climate fluctuations also significantly influence the region's warming, contributing to temperature extremes. Plain Language Summary Warming of the Earth's climate due to anthropogenic influences is expected to continue in the future. The present study examines in detail the actual and projected temperature changes in the Middle East and North Africa (MENA) region from 1850 to the end of this century. Using the most recently available data and models, we show that the region, notably the Arabian Peninsula, is warming significantly faster than the rest of the world. The high warming rate in the central part of the Arabian Peninsula is comparable to that in the Arctic and is two to three times the global average. This finding is concerning because the Arabian Peninsula is already one of the hottest locations on Earth. Additional warming hotspots are Algeria, Mauritania, and the Elburz Mountains in Iran. Rapid warming in the MENA will considerably affect the population and may compromise habitability.
Many modelling studies suggest that the El Niño–Southern Oscillation (ENSO), in interaction with ... more Many modelling studies suggest that the El Niño–Southern Oscillation (ENSO), in interaction with the tropical Pacific background climate, will change with rising atmospheric greenhouse gas concentrations. Solar geoengineering (reducing the solar flux from outer space) has been proposed as a means to counteract anthropogenic climate change. However, the effectiveness of solar geoengineering concerning a variety of aspects of Earth's climate is uncertain. Robust results are particularly challenging to obtain for ENSO because existing geoengineering simulations are too short (typically ∼ 50 years) to detect statistically significant changes in the highly variable tropical Pacific background climate. We here present results from a 1000-year-long solar-geoengineering simulation, G1, carried out with the coupled atmosphere–ocean general circulation model HadCM3L. In agreement with previous studies, reducing the solar irradiance (4 %) to offset global mean surface warming in the model more than compensates the warming in the tropical Pacific that develops in the 4 × CO2 scenario. We see an overcooling of 0.3 ∘C and a 0.23 mm d−1 (5 %) reduction in mean rainfall over the tropical Pacific relative to preindustrial conditions in the G1 simulation, owing to the different latitudinal distributions of the shortwave (solar) and longwave (CO2) forcings. The location of the Intertropical Convergence Zone (ITCZ) in the tropical Pacific, which moved 7.5∘ southwards under 4 × CO2, is restored to its preindustrial position. However, other aspects of the tropical Pacific mean climate are not reset as effectively. Relative to preindustrial conditions, in G1 the time-averaged zonal wind stress, zonal sea surface temperature (SST) gradient, and meridional SST gradient are each statistically significantly reduced by around 10 %, and the Pacific Walker Circulation (PWC) is consistently weakened, resulting in conditions conducive to increased frequency of El Niño events. The overall amplitude of ENSO strengthens by 9 %–10 % in G1, but there is a 65 % reduction in the asymmetry between cold and warm events: cold events intensify more than warm events. Notably, the frequency of extreme El Niño and La Niña events increases by ca. 60 % and 30 %, respectively, while the total number of El Niño events increases by around 10 %. All of these changes are statistically significant at either 95 or 99 % confidence level. Somewhat paradoxically, while the number of total and extreme events increases, the extreme El Niño events become weaker relative to the preindustrial state, while the extreme La Niña events become even stronger. That is, such extreme El Niño events in G1 become less intense than under preindustrial conditions but also more frequent. In contrast, extreme La Niña events become stronger in G1, which is in agreement with the general overcooling of the tropical Pacific in G1 relative to preindustrial conditions.
Many modelling studies suggest that the El Niño Southern Oscillation (ENSO), in interaction with ... more Many modelling studies suggest that the El Niño Southern Oscillation (ENSO), in interaction with the tropical Pacific background climate, will change under rising atmospheric greenhouse gas concentrations. Solar geoengineering (reducing the solar flux from outer space) has been proposed as a means to counteract anthropogenic greenhouse-induced changes in climate. Effectiveness of solar geoengineering is uncertain. Robust results are particularly difficult to obtain for ENSO because existing geoengineering simulations are too short (typically ~50 years) to detect statistically significant changes in the highly variable tropical Pacific background climate. We here present results from a 1000-year sunshade geoengineering simulation, G1, carried out with the coupled atmosphere-ocean general circulation model HadCM3L. In agreement with previous studies, reducing the shortwave solar flux more than compensates the warming in the tropical Pacific that develops in the 4×CO2 scenario: we observe an overcooling of 0.3oC (5 %) and 0.23-mm day-1 (5 %) reduction in mean rainfall relative to preindustrial conditions in the G1 simulation. This is due to the different latitudinal distributions of the shortwave (solar) and longwave (CO2) forcings.The location of the Intertropical Convergence Zone (ITCZ) located north of equator in the tropical Pacific, which moved 7.5o southwards under 4×CO2, is also restored to its preindustrial location. However, other aspects of the tropical Pacific mean climate are not reset as effectively. Relative to preindustrial conditions, in G1 the zonal wind stress, zonal sea surface temperature (SST) gradient, and meridional SST gradient are reduced by 10 %, 11 %, and 9 %, respectively, and the Pacific Walker Circulation (PWC) is consistently weakened. The overall amplitude of ENSO strengthens by 5-8 %, but there is a 65 % reduction in the asymmetry between cold and warm events: cold events intensify more than warm events. Importantly, the frequency of extreme El Niño and La Niña events increases by 44 % and 32 %, respectively, while the total number of El Niño events increases by 12 %. Paradoxically, while the number of total and extreme events increase, the most extreme El Niño events also become weaker relative to preindustrial state while the La Niña events become stronger. That is, extreme El Niño events in G1 become less extreme than in preindustrial conditions, but extreme El Niño events become more frequent. In contrast, extreme La Niña events become stronger in G1. This is in agreement with the general overcooling of the tropical Pacific in G1 relative to preindustrial conditions, which depict a shift towards generally more La Niña-like conditions.
A study was conducted to analyse the temporal patterns of changes in forest cover area in SWAT, K... more A study was conducted to analyse the temporal patterns of changes in forest cover area in SWAT, Khyber Pakhtunkhwa, Pakistan, over the period of 2000-11 and to examine the causes of deforestation by using satellite images, population data as well as field data. The results obtained through data analysis showed that by carefully investigating the existing growth patterns in the historical and current classified satellite image datasets, the potential direction of population expansion, forest change and other land cover features in SWAT can be predicted. It was observed that forested area has decreased while the bare land area of SWAT has increased from 2000 to 2011, probably due to the urbanization trend. Urbanization also affected the other land cover features. It is concluded that the changes in the land cover of SWAT and their effect on the land can be emphasized with timely monitored land cover and land use in the form of maps. Now it is easy to update existing maps swiftly and cost effectively by using remote sensing and GIS.
In this study we investigate statistical link
between external climate forcings and modes of ocea... more In this study we investigate statistical link between external climate forcings and modes of ocean variability on inter-annual (3-year) to centennial (100-year) timescales using de-trended semi-partial-cross-correlation analysis technique. To investigate this link we employ observations (AD 1854–1999), climate proxies (AD 1600–1999), and coupled Atmosphere-Ocean-Chemistry Climate Model simulations with SOCOL-MPIOM (AD 1600–1999). We find robust statistical evidence that Atlantic multi-decadal oscillation (AMO) has intrinsic positive correlation with solar activity in all datasets employed. The strength of the relationship between AMO and solar activity is modulated by volcanic eruptions and complex interaction among modes of ocean variability. The observational dataset reveals that El Niño southern oscillation (ENSO) has statistically significant negative intrinsic correlation with solar activity on decadal to multi-decadal timescales (16– 27-year) whereas there is no evidence of a link on a typical ENSO timescale (2–7-year). In the observational dataset, the volcanic eruptions do not have a link with AMO on a typical AMO timescale (55–80-year) however the longterm datasets (proxies and SOCOL-MPIOM output) show that volcanic eruptions have intrinsic negative correlation with AMO on inter-annual to multi-decadal timescales.
The Pacific decadal oscillation has no link with solar activity, however, it has positive intrinsic correlation with volcanic eruptions on multi-decadal timescales (47–54-year) in reconstruction and decadal to multi-decadal timescales (16–32-year) in climate model simulations. We also find evidence of a link between volcanic eruptions and ENSO, however, the sign of relationship is not consistent between observations/proxies and climate model simulations.
The Modes of Ocean Variability (MOV) namely Atlantic Multidecadal Oscillation (AMO), Pacific Deca... more The Modes of Ocean Variability (MOV) namely Atlantic Multidecadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), and El Niño Southern Oscillation (ENSO) can have significant impacts on Indian Summer Monsoon Rainfall (ISMR) on different timescales. The timescales at which these MOV interacts with ISMR and the factors which may perturb their relationship with ISMR need to be investigated. We employ De-trended Cross-Correlation Analysis (DCCA), and De-trended Partial-Cross-Correlation Analysis (DPCCA) to study the timescales of interaction of ISMR with AMO, PDO, and ENSO using observational dataset (AD 1854–1999), and atmosphere–ocean–chemistry climate model simulations with SOCOL-MPIOM (AD 1600–1999). Further, this study uses De-trended Semi-Partial Cross-Correlation Analysis (DSPCCA) to address the relation between solar variability and the ISMR. We find statistically significant evidence of intrinsic correlations of ISMR with AMO, PDO, and ENSO on different timescales, consistent between model simulations and observations. However, the model fails to capture modulation in intrinsic relationship between ISRM and MOV due to external signals. Our analysis indicates that AMO is a potential source of non-stationary relationship between ISMR and ENSO. Furthermore, the pattern of correlation between ISMR and Total Solar Irradiance (TSI) is inconsistent between observations and model simulations. The observational dataset indicates statistically insignificant negative intrinsic correlation between ISMR and TSI on decadal-to-centennial timescales. This statistically insignificant negative intrinsic correlation is transformed to statistically significant positive extrinsic by AMO on 61–86-year timescale. We propose a new mechanism for Sun–monsoon connection which operates through AMO by changes in summer (June–September; JJAS) meridional gradient of tropospheric temperatures (ΔTTJJAS). There is a negative (positive) intrinsic correlation between ΔTTJJAS (AMO) and TSI. The negative intrinsic correlation between ΔTTJJAS and TSI indicates that high (low) solar activity weakens (strengthens) the meridional gradient of tropospheric temperature during the summer monsoon season and subsequently the weak (strong) ΔTTJJAS decreases (increases) the ISMR. However, the presence of AMO transforms the negative intrinsic relation between ΔTTJJAS and TSI into positive extrinsic and strengthens the ISMR. We conclude that the positive relation between ISMR and solar activity, as found by other authors, is mainly due to the effect of AMO on ISMR.
The impact of solar variability on weather and climate in central Europe is still not well unders... more The impact of solar variability on weather and climate in central Europe is still not well understood. In this paper we use a new time series of daily weather types to analyse the influence of the 11-year solar cycle on the tropospheric weather of central Europe. We employ a novel, daily weather type classification over the period 1763-2009 and investigate the occurrence frequency of weather types under low, moderate, and high solar activity level. Results show a tendency towards fewer days with westerly and west-southwesterly flow over central Europe under low solar activity. In parallel, the occurrence of northerly and easterly types increases. For the 1958-2009 period, a more detailed view can be gained from reanalysis data. Mean sea level pressure composites under low solar activity also show a reduced zonal flow, with an increase of the mean blocking frequency between Iceland and Scandinavia. Weather types and reanalysis data show that the 11-year solar cycle influences the late winter atmospheric circulation over central Europe with colder (warmer) conditions under low (high) solar activity.
The present study is an effort to deepen the
understanding of Indian summer monsoon rainfall (ISM... more The present study is an effort to deepen the understanding of Indian summer monsoon rainfall (ISMR) on decadal to multi-decadal timescales. We use ensemble simulations for the period AD 1600–2000 carried out by the coupled Atmosphere-Ocean-Chemistry-Climate Model (AOCCM) SOCOL-MPIOM. Firstly, the SOCOL-MPIOM is evaluated using observational and reanalyses datasets. The model is able to realistically simulate the ISMR as well as relevant patterns of sea surface temperature and atmospheric circulation. Further, the influence of Atlantic Multidecadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), and El Niño Southern Oscillation (ENSO) variability on ISMR is realistically simulated. Secondly, we investigate the impact of internal climate variability and external climate forcings on ISMR on decadal to multi-decadal timescales over the past 400 years. The results show that AMO, PDO, and Total Solar Irradiance (TSI) play a considerable role in controlling the wet and dry decades of ISMR. Resembling observational findings most of the dry decades of ISMR occur during a negative phase of AMO and a simultaneous positive phase of PDO. The observational and simulated datasets reveal that on decadal to multi-decadal timescales the ISMR has consistent negative correlation with PDO whereas its correlation with AMO and TSI is not stationary over time.
Effects of the Quasi-Biennial Oscillation (QBO) on tropospheric climate are not always strong or ... more Effects of the Quasi-Biennial Oscillation (QBO) on tropospheric climate are not always strong or they appear only intermittently. Studying them requires long time series of both the QBO and climate variables, which has restricted previous studies to the past 30-50 years. Here we use the benefits of an existing QBO reconstruction back to 1908. We first investigate additional, newly digitized historical observations of stratospheric winds to test the reconstruction. Then we use the QBO time series to analyse atmospheric data sets (reconstructions and reanalyses) as well as the results of coupled ocean-atmosphere-chemistry climate model simulations that were forced with the reconstructed QBO. We investigate effects related to (1) tropical-extratropical interaction in the stratosphere, wave-mean flow interaction and subsequent downward propagation, and (2) interaction between deep tropical convection and stratospheric flow. We generally find weak connections, though some are statistically significant over the 100-year period and consistent with model results. Apparent multidecadal variations in the connection between the QBO and the investigated climate responses are consistent with a small effect in the presence of large variability, with one exception: the imprint on the northern polar vortex, which is seen in recent reanalysis data, is not found in the period 1908-1957. Conversely, an imprint in Berlin surface air temperature is only found in 1908-1957 but not in the recent period. Likewise, in the model simulations both links tend to appear alternatingly, suggesting a more systematic modulation due to a shift in the circulation, for example. Over the Pacific warm pool, we find increased convection during easterly QBO, mainly in boreal winter in observation-based data as well as in the model simulations, with large variability. No QBO effects were found in the Indian monsoon strength or Atlantic hurricane frequency.
Accelerated Historical and Future Warming in the Middle East and North Africa, 2024
The present study assesses the climate of the Middle East and North Africa (MENA) in detail, focu... more The present study assesses the climate of the Middle East and North Africa (MENA) in detail, focusing on the historical and future warming trends in the region. The assessment incorporates data from observations, reanalyses, and statistically downscaled climate models from the Coupled Model Intercomparison Project Phases 5 and 6. Since the pre-industrial era, the observed average climate in the MENA has warmed by 1.5°C and is on the brink of exceeding 2°C. The reanalysis data suggest that the regional warming over some MENA sub-regions is three times faster than the global average. By the end of the 21st century, the Arabian Peninsula is projected to warm to 2.6°C ± 0.57°C and 7.6°C ± 1.53°C under low and high greenhouse gas emission scenarios, respectively. Distinct warming hotspots emerge over the Arabian Peninsula and Algeria in summer and over Mauritania in West Africa and the Elburz Mountains in Iran in winter. The summer hotspot over the Arabian Peninsula has already warmed by more than 2°C and can potentially warm to approximately 9°C under the high-emission scenario. As global warming progresses to 1.5, 2.0, 3.0, and 4.0°C, the average temperature over the MENA land is projected to increase by 2.3°C ± 0.18°C, 3.0°C ± 0.22°C, 4.6°C ± 0.26°C, and 6.1°C ± 0.31°C, respectively. The 1.5, 2.0, 3.0, and 4.0°C warming levels over the MENA are expected to predate those of the global mean by two or three decades. Natural climate fluctuations also significantly influence the region's warming, contributing to temperature extremes. Plain Language Summary Warming of the Earth's climate due to anthropogenic influences is expected to continue in the future. The present study examines in detail the actual and projected temperature changes in the Middle East and North Africa (MENA) region from 1850 to the end of this century. Using the most recently available data and models, we show that the region, notably the Arabian Peninsula, is warming significantly faster than the rest of the world. The high warming rate in the central part of the Arabian Peninsula is comparable to that in the Arctic and is two to three times the global average. This finding is concerning because the Arabian Peninsula is already one of the hottest locations on Earth. Additional warming hotspots are Algeria, Mauritania, and the Elburz Mountains in Iran. Rapid warming in the MENA will considerably affect the population and may compromise habitability.
Many modelling studies suggest that the El Niño–Southern Oscillation (ENSO), in interaction with ... more Many modelling studies suggest that the El Niño–Southern Oscillation (ENSO), in interaction with the tropical Pacific background climate, will change with rising atmospheric greenhouse gas concentrations. Solar geoengineering (reducing the solar flux from outer space) has been proposed as a means to counteract anthropogenic climate change. However, the effectiveness of solar geoengineering concerning a variety of aspects of Earth's climate is uncertain. Robust results are particularly challenging to obtain for ENSO because existing geoengineering simulations are too short (typically ∼ 50 years) to detect statistically significant changes in the highly variable tropical Pacific background climate. We here present results from a 1000-year-long solar-geoengineering simulation, G1, carried out with the coupled atmosphere–ocean general circulation model HadCM3L. In agreement with previous studies, reducing the solar irradiance (4 %) to offset global mean surface warming in the model more than compensates the warming in the tropical Pacific that develops in the 4 × CO2 scenario. We see an overcooling of 0.3 ∘C and a 0.23 mm d−1 (5 %) reduction in mean rainfall over the tropical Pacific relative to preindustrial conditions in the G1 simulation, owing to the different latitudinal distributions of the shortwave (solar) and longwave (CO2) forcings. The location of the Intertropical Convergence Zone (ITCZ) in the tropical Pacific, which moved 7.5∘ southwards under 4 × CO2, is restored to its preindustrial position. However, other aspects of the tropical Pacific mean climate are not reset as effectively. Relative to preindustrial conditions, in G1 the time-averaged zonal wind stress, zonal sea surface temperature (SST) gradient, and meridional SST gradient are each statistically significantly reduced by around 10 %, and the Pacific Walker Circulation (PWC) is consistently weakened, resulting in conditions conducive to increased frequency of El Niño events. The overall amplitude of ENSO strengthens by 9 %–10 % in G1, but there is a 65 % reduction in the asymmetry between cold and warm events: cold events intensify more than warm events. Notably, the frequency of extreme El Niño and La Niña events increases by ca. 60 % and 30 %, respectively, while the total number of El Niño events increases by around 10 %. All of these changes are statistically significant at either 95 or 99 % confidence level. Somewhat paradoxically, while the number of total and extreme events increases, the extreme El Niño events become weaker relative to the preindustrial state, while the extreme La Niña events become even stronger. That is, such extreme El Niño events in G1 become less intense than under preindustrial conditions but also more frequent. In contrast, extreme La Niña events become stronger in G1, which is in agreement with the general overcooling of the tropical Pacific in G1 relative to preindustrial conditions.
Many modelling studies suggest that the El Niño Southern Oscillation (ENSO), in interaction with ... more Many modelling studies suggest that the El Niño Southern Oscillation (ENSO), in interaction with the tropical Pacific background climate, will change under rising atmospheric greenhouse gas concentrations. Solar geoengineering (reducing the solar flux from outer space) has been proposed as a means to counteract anthropogenic greenhouse-induced changes in climate. Effectiveness of solar geoengineering is uncertain. Robust results are particularly difficult to obtain for ENSO because existing geoengineering simulations are too short (typically ~50 years) to detect statistically significant changes in the highly variable tropical Pacific background climate. We here present results from a 1000-year sunshade geoengineering simulation, G1, carried out with the coupled atmosphere-ocean general circulation model HadCM3L. In agreement with previous studies, reducing the shortwave solar flux more than compensates the warming in the tropical Pacific that develops in the 4×CO2 scenario: we observe an overcooling of 0.3oC (5 %) and 0.23-mm day-1 (5 %) reduction in mean rainfall relative to preindustrial conditions in the G1 simulation. This is due to the different latitudinal distributions of the shortwave (solar) and longwave (CO2) forcings.The location of the Intertropical Convergence Zone (ITCZ) located north of equator in the tropical Pacific, which moved 7.5o southwards under 4×CO2, is also restored to its preindustrial location. However, other aspects of the tropical Pacific mean climate are not reset as effectively. Relative to preindustrial conditions, in G1 the zonal wind stress, zonal sea surface temperature (SST) gradient, and meridional SST gradient are reduced by 10 %, 11 %, and 9 %, respectively, and the Pacific Walker Circulation (PWC) is consistently weakened. The overall amplitude of ENSO strengthens by 5-8 %, but there is a 65 % reduction in the asymmetry between cold and warm events: cold events intensify more than warm events. Importantly, the frequency of extreme El Niño and La Niña events increases by 44 % and 32 %, respectively, while the total number of El Niño events increases by 12 %. Paradoxically, while the number of total and extreme events increase, the most extreme El Niño events also become weaker relative to preindustrial state while the La Niña events become stronger. That is, extreme El Niño events in G1 become less extreme than in preindustrial conditions, but extreme El Niño events become more frequent. In contrast, extreme La Niña events become stronger in G1. This is in agreement with the general overcooling of the tropical Pacific in G1 relative to preindustrial conditions, which depict a shift towards generally more La Niña-like conditions.
A study was conducted to analyse the temporal patterns of changes in forest cover area in SWAT, K... more A study was conducted to analyse the temporal patterns of changes in forest cover area in SWAT, Khyber Pakhtunkhwa, Pakistan, over the period of 2000-11 and to examine the causes of deforestation by using satellite images, population data as well as field data. The results obtained through data analysis showed that by carefully investigating the existing growth patterns in the historical and current classified satellite image datasets, the potential direction of population expansion, forest change and other land cover features in SWAT can be predicted. It was observed that forested area has decreased while the bare land area of SWAT has increased from 2000 to 2011, probably due to the urbanization trend. Urbanization also affected the other land cover features. It is concluded that the changes in the land cover of SWAT and their effect on the land can be emphasized with timely monitored land cover and land use in the form of maps. Now it is easy to update existing maps swiftly and cost effectively by using remote sensing and GIS.
In this study we investigate statistical link
between external climate forcings and modes of ocea... more In this study we investigate statistical link between external climate forcings and modes of ocean variability on inter-annual (3-year) to centennial (100-year) timescales using de-trended semi-partial-cross-correlation analysis technique. To investigate this link we employ observations (AD 1854–1999), climate proxies (AD 1600–1999), and coupled Atmosphere-Ocean-Chemistry Climate Model simulations with SOCOL-MPIOM (AD 1600–1999). We find robust statistical evidence that Atlantic multi-decadal oscillation (AMO) has intrinsic positive correlation with solar activity in all datasets employed. The strength of the relationship between AMO and solar activity is modulated by volcanic eruptions and complex interaction among modes of ocean variability. The observational dataset reveals that El Niño southern oscillation (ENSO) has statistically significant negative intrinsic correlation with solar activity on decadal to multi-decadal timescales (16– 27-year) whereas there is no evidence of a link on a typical ENSO timescale (2–7-year). In the observational dataset, the volcanic eruptions do not have a link with AMO on a typical AMO timescale (55–80-year) however the longterm datasets (proxies and SOCOL-MPIOM output) show that volcanic eruptions have intrinsic negative correlation with AMO on inter-annual to multi-decadal timescales.
The Pacific decadal oscillation has no link with solar activity, however, it has positive intrinsic correlation with volcanic eruptions on multi-decadal timescales (47–54-year) in reconstruction and decadal to multi-decadal timescales (16–32-year) in climate model simulations. We also find evidence of a link between volcanic eruptions and ENSO, however, the sign of relationship is not consistent between observations/proxies and climate model simulations.
The Modes of Ocean Variability (MOV) namely Atlantic Multidecadal Oscillation (AMO), Pacific Deca... more The Modes of Ocean Variability (MOV) namely Atlantic Multidecadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), and El Niño Southern Oscillation (ENSO) can have significant impacts on Indian Summer Monsoon Rainfall (ISMR) on different timescales. The timescales at which these MOV interacts with ISMR and the factors which may perturb their relationship with ISMR need to be investigated. We employ De-trended Cross-Correlation Analysis (DCCA), and De-trended Partial-Cross-Correlation Analysis (DPCCA) to study the timescales of interaction of ISMR with AMO, PDO, and ENSO using observational dataset (AD 1854–1999), and atmosphere–ocean–chemistry climate model simulations with SOCOL-MPIOM (AD 1600–1999). Further, this study uses De-trended Semi-Partial Cross-Correlation Analysis (DSPCCA) to address the relation between solar variability and the ISMR. We find statistically significant evidence of intrinsic correlations of ISMR with AMO, PDO, and ENSO on different timescales, consistent between model simulations and observations. However, the model fails to capture modulation in intrinsic relationship between ISRM and MOV due to external signals. Our analysis indicates that AMO is a potential source of non-stationary relationship between ISMR and ENSO. Furthermore, the pattern of correlation between ISMR and Total Solar Irradiance (TSI) is inconsistent between observations and model simulations. The observational dataset indicates statistically insignificant negative intrinsic correlation between ISMR and TSI on decadal-to-centennial timescales. This statistically insignificant negative intrinsic correlation is transformed to statistically significant positive extrinsic by AMO on 61–86-year timescale. We propose a new mechanism for Sun–monsoon connection which operates through AMO by changes in summer (June–September; JJAS) meridional gradient of tropospheric temperatures (ΔTTJJAS). There is a negative (positive) intrinsic correlation between ΔTTJJAS (AMO) and TSI. The negative intrinsic correlation between ΔTTJJAS and TSI indicates that high (low) solar activity weakens (strengthens) the meridional gradient of tropospheric temperature during the summer monsoon season and subsequently the weak (strong) ΔTTJJAS decreases (increases) the ISMR. However, the presence of AMO transforms the negative intrinsic relation between ΔTTJJAS and TSI into positive extrinsic and strengthens the ISMR. We conclude that the positive relation between ISMR and solar activity, as found by other authors, is mainly due to the effect of AMO on ISMR.
The impact of solar variability on weather and climate in central Europe is still not well unders... more The impact of solar variability on weather and climate in central Europe is still not well understood. In this paper we use a new time series of daily weather types to analyse the influence of the 11-year solar cycle on the tropospheric weather of central Europe. We employ a novel, daily weather type classification over the period 1763-2009 and investigate the occurrence frequency of weather types under low, moderate, and high solar activity level. Results show a tendency towards fewer days with westerly and west-southwesterly flow over central Europe under low solar activity. In parallel, the occurrence of northerly and easterly types increases. For the 1958-2009 period, a more detailed view can be gained from reanalysis data. Mean sea level pressure composites under low solar activity also show a reduced zonal flow, with an increase of the mean blocking frequency between Iceland and Scandinavia. Weather types and reanalysis data show that the 11-year solar cycle influences the late winter atmospheric circulation over central Europe with colder (warmer) conditions under low (high) solar activity.
The present study is an effort to deepen the
understanding of Indian summer monsoon rainfall (ISM... more The present study is an effort to deepen the understanding of Indian summer monsoon rainfall (ISMR) on decadal to multi-decadal timescales. We use ensemble simulations for the period AD 1600–2000 carried out by the coupled Atmosphere-Ocean-Chemistry-Climate Model (AOCCM) SOCOL-MPIOM. Firstly, the SOCOL-MPIOM is evaluated using observational and reanalyses datasets. The model is able to realistically simulate the ISMR as well as relevant patterns of sea surface temperature and atmospheric circulation. Further, the influence of Atlantic Multidecadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), and El Niño Southern Oscillation (ENSO) variability on ISMR is realistically simulated. Secondly, we investigate the impact of internal climate variability and external climate forcings on ISMR on decadal to multi-decadal timescales over the past 400 years. The results show that AMO, PDO, and Total Solar Irradiance (TSI) play a considerable role in controlling the wet and dry decades of ISMR. Resembling observational findings most of the dry decades of ISMR occur during a negative phase of AMO and a simultaneous positive phase of PDO. The observational and simulated datasets reveal that on decadal to multi-decadal timescales the ISMR has consistent negative correlation with PDO whereas its correlation with AMO and TSI is not stationary over time.
Effects of the Quasi-Biennial Oscillation (QBO) on tropospheric climate are not always strong or ... more Effects of the Quasi-Biennial Oscillation (QBO) on tropospheric climate are not always strong or they appear only intermittently. Studying them requires long time series of both the QBO and climate variables, which has restricted previous studies to the past 30-50 years. Here we use the benefits of an existing QBO reconstruction back to 1908. We first investigate additional, newly digitized historical observations of stratospheric winds to test the reconstruction. Then we use the QBO time series to analyse atmospheric data sets (reconstructions and reanalyses) as well as the results of coupled ocean-atmosphere-chemistry climate model simulations that were forced with the reconstructed QBO. We investigate effects related to (1) tropical-extratropical interaction in the stratosphere, wave-mean flow interaction and subsequent downward propagation, and (2) interaction between deep tropical convection and stratospheric flow. We generally find weak connections, though some are statistically significant over the 100-year period and consistent with model results. Apparent multidecadal variations in the connection between the QBO and the investigated climate responses are consistent with a small effect in the presence of large variability, with one exception: the imprint on the northern polar vortex, which is seen in recent reanalysis data, is not found in the period 1908-1957. Conversely, an imprint in Berlin surface air temperature is only found in 1908-1957 but not in the recent period. Likewise, in the model simulations both links tend to appear alternatingly, suggesting a more systematic modulation due to a shift in the circulation, for example. Over the Pacific warm pool, we find increased convection during easterly QBO, mainly in boreal winter in observation-based data as well as in the model simulations, with large variability. No QBO effects were found in the Indian monsoon strength or Atlantic hurricane frequency.
Uploads
Papers by Abdul Malik
between external climate forcings and modes of ocean
variability on inter-annual (3-year) to centennial (100-year)
timescales using de-trended semi-partial-cross-correlation
analysis technique. To investigate this link we employ
observations (AD 1854–1999), climate proxies (AD
1600–1999), and coupled Atmosphere-Ocean-Chemistry
Climate Model simulations with SOCOL-MPIOM (AD
1600–1999). We find robust statistical evidence that Atlantic
multi-decadal oscillation (AMO) has intrinsic positive
correlation with solar activity in all datasets employed. The
strength of the relationship between AMO and solar activity
is modulated by volcanic eruptions and complex interaction
among modes of ocean variability. The observational dataset
reveals that El Niño southern oscillation (ENSO) has
statistically significant negative intrinsic correlation with
solar activity on decadal to multi-decadal timescales (16–
27-year) whereas there is no evidence of a link on a typical
ENSO timescale (2–7-year). In the observational dataset,
the volcanic eruptions do not have a link with AMO on a
typical AMO timescale (55–80-year) however the longterm
datasets (proxies and SOCOL-MPIOM output) show
that volcanic eruptions have intrinsic negative correlation
with AMO on inter-annual to multi-decadal timescales.
The Pacific decadal oscillation has no link with solar activity,
however, it has positive intrinsic correlation with volcanic
eruptions on multi-decadal timescales (47–54-year)
in reconstruction and decadal to multi-decadal timescales
(16–32-year) in climate model simulations. We also find
evidence of a link between volcanic eruptions and ENSO,
however, the sign of relationship is not consistent between
observations/proxies and climate model simulations.
understanding of Indian summer monsoon rainfall (ISMR)
on decadal to multi-decadal timescales. We use ensemble
simulations for the period AD 1600–2000 carried out by
the coupled Atmosphere-Ocean-Chemistry-Climate Model
(AOCCM) SOCOL-MPIOM. Firstly, the SOCOL-MPIOM
is evaluated using observational and reanalyses datasets.
The model is able to realistically simulate the ISMR as well
as relevant patterns of sea surface temperature and atmospheric
circulation. Further, the influence of Atlantic Multidecadal
Oscillation (AMO), Pacific Decadal Oscillation
(PDO), and El Niño Southern Oscillation (ENSO) variability
on ISMR is realistically simulated. Secondly, we investigate
the impact of internal climate variability and external
climate forcings on ISMR on decadal to multi-decadal timescales over the past 400 years. The results show that
AMO, PDO, and Total Solar Irradiance (TSI) play a considerable
role in controlling the wet and dry decades of
ISMR. Resembling observational findings most of the dry
decades of ISMR occur during a negative phase of AMO
and a simultaneous positive phase of PDO. The observational
and simulated datasets reveal that on decadal to
multi-decadal timescales the ISMR has consistent negative
correlation with PDO whereas its correlation with AMO
and TSI is not stationary over time.
between external climate forcings and modes of ocean
variability on inter-annual (3-year) to centennial (100-year)
timescales using de-trended semi-partial-cross-correlation
analysis technique. To investigate this link we employ
observations (AD 1854–1999), climate proxies (AD
1600–1999), and coupled Atmosphere-Ocean-Chemistry
Climate Model simulations with SOCOL-MPIOM (AD
1600–1999). We find robust statistical evidence that Atlantic
multi-decadal oscillation (AMO) has intrinsic positive
correlation with solar activity in all datasets employed. The
strength of the relationship between AMO and solar activity
is modulated by volcanic eruptions and complex interaction
among modes of ocean variability. The observational dataset
reveals that El Niño southern oscillation (ENSO) has
statistically significant negative intrinsic correlation with
solar activity on decadal to multi-decadal timescales (16–
27-year) whereas there is no evidence of a link on a typical
ENSO timescale (2–7-year). In the observational dataset,
the volcanic eruptions do not have a link with AMO on a
typical AMO timescale (55–80-year) however the longterm
datasets (proxies and SOCOL-MPIOM output) show
that volcanic eruptions have intrinsic negative correlation
with AMO on inter-annual to multi-decadal timescales.
The Pacific decadal oscillation has no link with solar activity,
however, it has positive intrinsic correlation with volcanic
eruptions on multi-decadal timescales (47–54-year)
in reconstruction and decadal to multi-decadal timescales
(16–32-year) in climate model simulations. We also find
evidence of a link between volcanic eruptions and ENSO,
however, the sign of relationship is not consistent between
observations/proxies and climate model simulations.
understanding of Indian summer monsoon rainfall (ISMR)
on decadal to multi-decadal timescales. We use ensemble
simulations for the period AD 1600–2000 carried out by
the coupled Atmosphere-Ocean-Chemistry-Climate Model
(AOCCM) SOCOL-MPIOM. Firstly, the SOCOL-MPIOM
is evaluated using observational and reanalyses datasets.
The model is able to realistically simulate the ISMR as well
as relevant patterns of sea surface temperature and atmospheric
circulation. Further, the influence of Atlantic Multidecadal
Oscillation (AMO), Pacific Decadal Oscillation
(PDO), and El Niño Southern Oscillation (ENSO) variability
on ISMR is realistically simulated. Secondly, we investigate
the impact of internal climate variability and external
climate forcings on ISMR on decadal to multi-decadal timescales over the past 400 years. The results show that
AMO, PDO, and Total Solar Irradiance (TSI) play a considerable
role in controlling the wet and dry decades of
ISMR. Resembling observational findings most of the dry
decades of ISMR occur during a negative phase of AMO
and a simultaneous positive phase of PDO. The observational
and simulated datasets reveal that on decadal to
multi-decadal timescales the ISMR has consistent negative
correlation with PDO whereas its correlation with AMO
and TSI is not stationary over time.