Empirical evidence for deep convection being a major source of stratospheric ice clouds over North America

Zou, Ling; Hoffmann, Lars; Grießbach, Sabine; Spang, Reinhold; Wang, Lunche

doi:10.5194/acp-21-10457-2021

Cited by 14 publications

(22 citation statements)

References 79 publications

(112 reference statements)

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“…The daily mean zonal mean tropopause data from MPTRAC are in accordance with first thermal tropopause data extracted from Global Positioning System (GPS) radio occultation observations on the same day. A more detailed description of the extraction of tropopause information with MPTRAC as well as the application of the data to identify stratospheric ice clouds is provided by Zou et al (2020Zou et al ( , 2021.…”

Section: A3 Determination Of the Tropopausementioning

confidence: 99%

Massive-Parallel Trajectory Calculations version 2.2 (MPTRAC-2.2): Lagrangian transport simulations on Graphics Processing Units (GPUs)

Hoffmann¹,

Baumeister²,

Cai³

et al. 2022

Preprint

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Lagrangian models are powerful tools to study atmospheric transport processes. However, conducting large-scaleLagrangian transport simulations with many air parcels can become numerically rather costly. In this study, we assessed the potential of exploiting graphics processing units (GPUs) to accelerate Lagrangian transport simulations. We ported the Massive-Parallel Trajectory Calculations (MPTRAC) model to GPUs using the open accelerator (OpenACC) programming model. The trajectory calculations conducted within the MPTRAC model have been fully ported to GPUs, i. e., except for feeding in the meteorological input data and for extracting the particle output data, the code operates entirely on the GPU devices without frequent data transfers between CPU and GPU memory. Model verification, performance analyses, and scaling tests of the MPI/OpenMP/OpenACC hybrid parallelization of MPTRAC have been conducted on the JUWELS Booster supercomputer operated by the Jülich Supercomputing Centre, Germany. The JUWELS Booster comprises 3744 NVIDIA A100 Tensor CoreGPUs, providing a peak performance of 71.0 PFlop/s. As of June 2021, it is the most powerful supercomputer in Europe and listed among the most energy-efficient systems internationally. For large-scale simulations comprising 100 million particles driven by the European Centre for Medium-Range Weather Forecasts’ ERA5 reanalysis, the performance evaluation showed a maximum speedup of a factor of 16 due to the utilization of GPUs compared to CPU-only runs on the JUWELS Booster. In the large-scale GPU run, about 67 % of the runtime is spent on the physics calculations, being conducted on the GPUs. Another 15 % of the runtime is required for file-I/O, mostly to read the ERA5 data from disk. Meteorological data preprocessing on the CPUs also requires about 15 % of the runtime. Although this study identified potential for further improvements of the GPU code, we consider the MPTRAC model to be ready for production runs on the JUWELS Booster in its present form. The GPU code provides a much faster time to solution than the CPU code, which is particularly relevant for near-real-time applications of a Lagrangian transport model

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Section: A3 Determination Of the Tropopausementioning

confidence: 99%

Massive-Parallel Trajectory Calculations version 2.2 (MPTRAC-2.2): Lagrangian transport simulations on Graphics Processing Units (GPUs)

Hoffmann¹,

Baumeister²,

Cai³

et al. 2022

Preprint

Self Cite

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“…Deep convection, gravity waves and sulfur dioxide (SO 2 ) emissions from volcanic eruptions can be retrieved from AIRS in wavebands at 8.1 µm, 4.3 µm and 7.3 µm, respectively (Aumann et al, 2003(Aumann et al, , 2006Hoffmann and Alexander, 2010;Hoffmann et al, 2013Hoffmann et al, , 2014aHoffmann et al, ,b, 2016. Since a constant brightness temperature (BT) threshold for deep convection detection may lead to ambiguous results at different latitudes and seasons (Hoffmann et al, 2013), temperature differences between AIRS brightness temperatures (BT AIRS ) at 1231 cm −1 (8.1 µm) and tropopause temperatures (T T P ) from ERA5 are used to detect deep convection events (Zou et al, 2021). An offset of +7 K on top of the T T P was set as the threshold to include all possible deep convection events with cloud tops near or above the tropopause, BT AIRS − T T P ≤ 7 K.…”

Section: Airs Observations Of Deep Convection Gravity Waves and Somentioning

confidence: 99%

“…The choice of the temperature threshold determines the absolute values of the occurrence frequencies of the deep convection events, but it does not fundamentally affect the spatial and temporal patterns of deep convection (Zou et al, 2021). The term "deep convection" here includes convection from storm systems and fronts, mesoscale convective systems, and mesoscale As the occurrence (coverage) of SICs associated with deep convection depends on the intensity, spatial extent, and duration of the deep convection, detection numbers of SICs and deep convection may not be the best indicator to elucidate their relations (Zou et al, 2021). Therefore, to effectively investigate the relation of SICs and deep convection, event frequency is defined in this work as the ratio of number of days in which deep convection or SICs (≥1 detection) occurs to the total number of days in a given time period over a given region.…”

Section: Airs Observations Of Deep Convection Gravity Waves and Somentioning

confidence: 99%

A global view on stratospheric ice clouds: assessment of processes related to their occurrence based on satellite observations

Zou¹,

Grießbach²,

Hoffmann³

et al. 2022

Preprint

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Abstract. Ice clouds play an important role in regulating water vapor and influencing the radiative budget in the atmosphere. In this study, stratospheric ice clouds (SICs) and stratospheric aerosols from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), deep convection and gravity waves from Atmospheric Infrared Sounder (AIRS) observations and tropopause temperature from ERA5 are analyzed to investigate their long-term variation and processes potentially related to the formation of SICs on the global scale. SICs with cloud top heights 0.25 km above the first tropopause are mainly detected over the tropical continents. SICs associated with the double tropopause events, where the cloud top is between the first and second thermal tropopause, are mostly located in midlatitudes (between 25°–60°). The seasonal cycle and the inter-annual variability of SIC frequencies from 2007 to 2019 show that high SIC frequencies are mainly observed south of the equator from November to March, and at 10° N–20° N from July to September. At mid- and high latitudes, more SICs are observed from December to May in the northern hemisphere and in the southern hemisphere during May to October. Relations between SICs and first tropopause temperature, deep convection, gravity waves, and stratospheric aerosol were analyzed, respectively, on a global scale. Positive correlations between SIC frequencies and deep convection, gravity waves, and stratospheric aerosol and an inverse correlation between SIC frequency and tropopause temperature were observed worldwide. Overlaps of high correlations/anti-correlations were detected over tropical continents, i.e., tropical South America, equatorial Africa, and western Pacific, suggesting a combined effect of tropopause temperature, deep convection, gravity waves, and stratospheric aerosol on SIC occurrence in these regions. Over Central America, North America, the Asian Monsoon, and mid- and high latitudes deep convection and gravity waves present a strong correlation with the occurrence of SICs, individually or interdependently. Regional analyses demonstrated specific relations of tropopause temperature, deep convection, gravity waves, and stratospheric aerosol with SICs at a finer scale. Low tropopause temperature and high occurrence frequency of stratospheric aerosol show strong correlations with high frequencies of SICs over the Indo-Pacific Warm Pool, tropical South America, and equatorial Africa. Deep convection and gravity waves have the strongest correlation with the occurrence frequency of SICs over the Asian Monsoon and the North American Monsoon. Gravity waves and tropopause temperature are highly correlated with SIC occurrence over South America and the northern Atlantic. Moreover, the El Niño phenomenon in 2009–2010 and 2015–2016 coincides with low SIC occurrences over the Indo-Pacific Warm Pool. High stratospheric aerosol loads related to volcanic eruptions (Puyehue-Cordón Caulle and Nabro in 2011) and wildfires (over the United States and Canada in 2017) are closely related to high occurrence frequencies of SICs. We investigated the global distribution and long-term variation of SICs and present a global view of relations between SIC occurrence and tropopause temperature, deep convection, gravity wave activity, and stratospheric aerosol. This work provides a better understanding of the physical processes and climate variability of SICs.

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“…In this study, we estimated tropopause data from more than 6.3×10 10 vertical profiles of pressure, temperature, and geopotential height of the 2009 -2018 ERA5 record. Considering the effort to process the large amount of ERA5 data, we decided to make the reanalysis tropopause data derived here available for future studies via a dedicated data repository (Hoffmann and Spang, 2021). The data repository is accessible at https://datapub.fz-juelich.de/slcs/tropopause/ (last access: 18 November 2021) or via https://doi.org/10.26165/JUELICH-DATA/UBNGI2 (last access: 18 November 2021).…”

Section: Appendix B: Comparison Of Linear and Cubic Spline Interpolation For Tropopause Determinationmentioning

confidence: 99%

“…troposphere exchange and mixing events between tropospheric and stratospheric air masses in the extra-tropical transition layer (e. g., Gettelman et al, 2011;Boothe and Homeyer, 2017), transport of water vapor from the troposphere into the stratosphere (Holton et al, 1995;Fueglistaler et al, 2009) and related effects on ozone (Anderson et al, 2012;Robrecht et al, 2021), or the formation of cirrus and convective ice clouds in the lowermost stratosphere (Spang et al, 2015;Zou et al, 2020Zou et al, , 2021.…”

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confidence: 99%

An assessment of tropopause characteristics of the ERA5 and ERA-Interim meteorological reanalyses

Hoffmann¹,

Spang²

2021

Preprint

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Abstract. The tropopause layer plays a key role in manifold processes in atmospheric chemistry and physics. Here we compare the representation and characteristics of the lapse rate tropopause according to the definition of the World Meteorological Organization (WMO) as estimated from European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data. Our study is based on ten-year records (2009 to 2018) of ECMWF's state-of-the-art reanalysis ERA5 and its predecessor ERA-Interim. The intercomparison reveals notable differences between ERA5 and ERA-Interim tropopause data, in particular on small spatiotemporal scales. The monthly mean differences of ERA5 minus ERA-Interim tropopause heights vary between −300 m at the transition from the tropics to the extratropics (near 30° S and 30° N) to 150 m around the equator. Mean tropopause temperatures are mostly lower in ERA5 than in ERA-Interim, with a maximum difference of up to −1.5 K in the tropics. Monthly standard deviations of tropopause heights of ERA5 are up to 350 m or 60 % larger than for ERA-Interim. Monthly standard deviations of tropopause temperatures of ERA5 exceed those of ERA-Interim by up to 1.5 K or 30 %. The occurrence frequencies of double tropopause events in ERA5 exceed those of ERA-Interim by up to 25 percentage points at mid latitudes. We attribute the differences between the ERA5 and ERA-Interim tropopause data and the larger, more realistic variability of ERA5 to improved spatiotemporal resolution and better representation of geophysical processes in the forecast model as well as improvements in the data assimilation scheme and the utilization of additional observations in ERA5. The improved spatiotemporal resolution of ERA5 allows for a better representation of mesoscale features, in particular of gravity waves, which affect the temperature profiles in the upper troposphere and lower stratosphere and thus the tropopause height estimates. We evaluated the quality of the ERA5 and ERA-Interim reanalysis tropopause data by comparisons with COSMIC and MetOp Global Positioning System (GPS) satellite observations as well as high-resolution radiosonde profiles. The comparison indicates an uncertainty of the first tropopause for ERA5 (ERA-Interim) of about ±150 m to ±200 m (±250 m) based on radiosonde data and ±120 m to ±150 m (±170 to ±200 m) based on the coarser resolution GPS data at different latitudes. Consequently, ERA5 will provide more accurate information than ERA-Interim for future tropopause-related studies.

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Empirical evidence for deep convection being a major source of stratospheric ice clouds over North America

Cited by 14 publications

References 79 publications

Massive-Parallel Trajectory Calculations version 2.2 (MPTRAC-2.2): Lagrangian transport simulations on Graphics Processing Units (GPUs)

Massive-Parallel Trajectory Calculations version 2.2 (MPTRAC-2.2): Lagrangian transport simulations on Graphics Processing Units (GPUs)

A global view on stratospheric ice clouds: assessment of processes related to their occurrence based on satellite observations

An assessment of tropopause characteristics of the ERA5 and ERA-Interim meteorological reanalyses

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