scholarly journals Assessing and improving cloud-height based parameterisations of global lightning flash rate, and their impact on lightning-produced NO<sub>x</sub> and tropospheric composition

2020 ◽  
Author(s):  
Ashok K. Luhar ◽  
Ian E. Galbally ◽  
Matthew T. Woodhouse ◽  
Nathan Luke Abraham
Keyword(s):  
Climate Model ◽  
Convective Cloud ◽  
Lightning Flash ◽  
Oxides Of Nitrogen ◽  
Upper Troposphere ◽  
Flash Rate ◽  
Global Average ◽  
Scaling Relationships ◽  
Tropospheric Photochemistry ◽  
Electrical Generator

Abstract. Although lightning-generated oxides of nitrogen (LNOx) account for only approximately 10 % of the global NOx source, it has a disproportionately large impact on tropospheric photochemistry due to the conducive conditions in the tropical upper troposphere where lightning is mostly discharged. In most global composition models, lightning flash rates used to calculate LNOx are expressed in terms of convective cloud-top height via the Price and Rind (1992) (PR92) parameterisations for land and ocean. We conduct a critical assessment of flash-rate parameterisations that are based on cloud-top height and validate them within the ACCESS-UKCA global chemistry-climate model using the LIS/OTD satellite data. While the PR92 parameterisation for land yields satisfactory predictions, the oceanic parameterisation underestimates the observed flash-rate density severely, yielding a global average of 0.33 flashes/s compared to the observed 9.16 flashes/s over the ocean and leading to LNOx being underestimated proportionally. We formulate new/alternative flash-rate parameterisations following Boccippio’s (2002) scaling relationships between thunderstorm electrical generator power and storm geometry coupled with available data. While the new parameterisation for land performs very similar to the corresponding PR92 one as would be expected, the new oceanic parameterisation simulates the flash-rate observations more accurately, giving a global average of 8.84 flashes/s. The use of the improved flash-rate parameterisations in ACCESS-UKCA changes the modelled tropospheric composition—global LNOx increases from 4.8 to 6.6 Tg N/yr; the ozone (O3) burden increases by 8.5 %; there is an increase in the mid- to upper-tropospheric NOx by as much as 40 ppt; a 13 % increase in the global hydroxyl (OH); a decrease in the methane lifetime by 6.7 %; and a decrease in the lower tropospheric carbon monoxide (CO) by 3–7 %. Overall, the modelled tropospheric NOx and ozone are improved compared to observations, particularly in the Southern Hemisphere and over the ocean.

scholarly journals Assessing and improving cloud-height-based parameterisations of global lightning flash rate, and their impact on lightning-produced NO<sub><i>x</i></sub> and tropospheric composition in a chemistry–climate model

2021 ◽  
Vol 21 (9) ◽  
pp. 7053-7082
Author(s):  
Ashok K. Luhar ◽  
Ian E. Galbally ◽  
Matthew T. Woodhouse ◽  
Nathan Luke Abraham
Keyword(s):  
Climate Model ◽  
Convective Cloud ◽  
Lightning Flash ◽  
Oxides Of Nitrogen ◽  
Flash Rate ◽  
Global Average ◽  
Tropospheric Photochemistry ◽  
Australian Community ◽  
Electrical Generator ◽  
Imaging Sensor

Abstract. Although lightning-generated oxides of nitrogen (LNOx) account for only approximately 10 % of the global NOx source, they have a disproportionately large impact on tropospheric photochemistry due to the conducive conditions in the tropical upper troposphere where lightning is mostly discharged. In most global composition models, lightning flash rates used to calculate LNOx are expressed in terms of convective cloud-top height via the Price and Rind (1992) (PR92) parameterisations for land and ocean, where the oceanic parameterisation is known to greatly underestimate flash rates. We conduct a critical assessment of flash-rate parameterisations that are based on cloud-top height and validate them within the Australian Community Climate and Earth System Simulator – United Kingdom Chemistry and Aerosol (ACCESS-UKCA) global chemistry–climate model using the Lightning Imaging Sensor and Optical Transient Detector (LIS/OTD) satellite data. While the PR92 parameterisation for land yields satisfactory predictions, the oceanic parameterisation, as expected, underestimates the observed flash-rate density severely, yielding a global average over the ocean of 0.33 flashes s−1 compared to the observed 9.16 flashes s−1 and leading to LNOx being underestimated proportionally. We formulate new flash-rate parameterisations following Boccippio's (2002) scaling relationships between thunderstorm electrical generator power and storm geometry coupled with available data. The new parameterisation for land performs very similarly to the corresponding PR92 one, as would be expected, whereas the new oceanic parameterisation simulates the flash-rate observations much more accurately, giving a global average over the ocean of 8.84 flashes s−1. The use of the improved flash-rate parameterisations in ACCESS-UKCA changes the modelled tropospheric composition – global LNOx increases from 4.8 to 6.6 Tg N yr−1; the ozone (O3) burden increases by 8.5 %; there is an increase in the mid- to upper-tropospheric NOx by as much as 40 pptv, a 13 % increase in the global hydroxyl radical (OH), a decrease in the methane lifetime by 6.7 %, and a decrease in the lower-tropospheric carbon monoxide (CO) by 3 %–7 %. Compared to observations, the modelled tropospheric NOx and ozone in the Southern Hemisphere and over the ocean are improved by this new flash-rate parameterisation.

scholarly journals Relationship of lightning flashes frequency with statistical characteristics of convective activity in the atmopshere

2019 ◽  
Vol 485 (1) ◽  
pp. 76-82
Author(s):  
A. V. Eliseev ◽  
A. N. Ploskov ◽  
А. V. Chernokulsky ◽  
I. I. Mokhov
Keyword(s):  
Global Warming ◽  
Climate Model ◽  
Surface Air Temperature ◽  
Convective Cloud ◽  
Statistical Characteristics ◽  
Lightning Flash ◽  
Convective Activity ◽  
Global Level ◽  
Relationship Of ◽  
The Relationship

A modification of the commonly used Price-Rind scheme for lightning flashes frequency (LFF), which can be used for calculations with large spatial and time steps, is developed. With such steps, the exponent in the relationship of LFF on convective cloud heights appears to be smaller by a factor of two over land and by one fourth over ocean in comparison to that in the original Price-Rind scheme. The modified version is implemented into the IAP RAS climate model (CM). The results of the lightning flash frequency simulations with the modified scheme agree better with the satellite data than those with the original one. In the IAP RAS CM, global warming (cooling) leads to LFF increase (decrease) in all seasons. The sensitivity of lightning flashes frequency to the surface air temperature change at the global level is estimated equal to 10%/K.

scholarly journals Atmospheric teleconnection processes linking winter air stagnation and haze extremes in China with regional Arctic sea ice decline

2019 ◽  
Author(s):  
Yufei Zou ◽  
Yuhang Wang ◽  
Zuowei Xie ◽  
Hailong Wang ◽  
Philip J. Rasch
Keyword(s):  
Sea Ice ◽  
Climate Model ◽  
Teleconnection Pattern ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Transient Eddy ◽  
Regional Ventilation ◽  
Atmospheric Teleconnection ◽  
Upper Troposphere ◽  
Arctic Sea

Abstract. Recent studies suggested significant impacts of boreal cryosphere changes on wintertime air stagnation and haze pollution extremes in China. However, the underlying mechanism of such a teleconnection relationship remains unclear. Here we used the Whole Atmosphere Community Climate Model (WACCM) to investigate dynamic processes leading to atmospheric circulation and air stagnation responses to Arctic sea ice changes. We conducted four climate sensitivity experiments by perturbing sea ice concentrations (SIC) and corresponding sea surface temperature (SST) in autumn and early winter over the whole Arctic and three sub-regions in the climate model. The results indicate different responses in the general circulation and regional ventilation to the region-specific Arctic changes, with the largest increase of both the probability (by 120 %) and the intensity (by 32 %) of air stagnation extreme events being found in the experiment driven by SIC and SST changes over the Pacific sector of the Arctic (the East Siberian and Chukchi Seas). The increased air stagnation extreme events are mainly driven by an amplified hemispheric-scale atmospheric teleconnection pattern that resembles the negative phase of the Eurasian (EU) pattern. Dynamical diagnostics suggest that convergence of transient eddy forcing in the vicinity of Scandinavia in winter is largely responsible for the amplification of the teleconnection pattern. Transient eddy vorticity fluxes dominate the transient eddy forcing and produce a barotropic anticyclonic anomaly near Scandinavia and wave-train propagation across Eurasia to the downstream regions in East Asia. The piecewise potential vorticity inversion analysis reveals that this long-range atmospheric teleconnection of the Arctic origin takes place primarily in the middle and upper troposphere. The anomalous ridge over East Asia in the middle and upper troposphere worsens regional ventilation conditions by weakening monsoon northwesterlies and enhancing temperature inversion near the surface, leading to more and stronger air stagnation and pollution extremes over eastern China in winter. Ensemble projections based on the state-of-the-art climate models in the Coupled Model Intercomparison Project Phase 6 (CMIP6) corroborate this teleconnection relationship between high-latitude environmental changes and middle-latitude weather extremes, though the tendency and magnitude vary considerably among each participating model.

scholarly journals Chemistry–climate interactions of aerosol nitrate from lightning

2017 ◽  
Vol 17 (2) ◽  
pp. 1125-1142 ◽  
Author(s):  
Holger Tost
Keyword(s):  
Climate Model ◽  
Statistical Significance ◽  
Aerosol Particles ◽  
Internal Variability ◽  
Aerosol Size Distribution ◽  
Upper Troposphere ◽  
Uncertainty Range ◽  
Mixing Ratios ◽  
Microphysical Properties ◽  
The Impact

Abstract. Lightning represents one of the dominant emission sources for NOx in the troposphere. The direct release of oxidised nitrogen in the upper troposphere does not only affect ozone formation, but also chemical and microphysical properties of aerosol particles in this region. This study investigates the direct impact of LNOx emissions on upper-tropospheric nitrate using a global chemistry climate model. The simulation results show a substantial influence of the lightning emissions on the mixing ratios of nitrate aerosol in the upper troposphere of more than 50 %. In addition to the impact on nitrate, lightning substantially affects the oxidising capacity of the atmosphere with substantial implications for gas-phase sulfate formation and new particle formation in the upper troposphere. In conjunction with the condensation of nitrates, substantial differences in the aerosol size distribution occur in the upper troposphere as a consequence of lightning. This has implications for the extinction properties of the aerosol particles and for the cloud optical properties. While the extinction is generally slightly enhanced due to the LNOx emissions, the response of the clouds is ambiguous due to compensating effects in both liquid and ice clouds. Resulting shortwave flux perturbations are of   ∼ −100 mW m−2 as determined from several sensitivity scenarios, but an uncertainty range of almost 50 % has to be defined due to the large internal variability of the system and the uncertainties in the multitude of involved processes. Despite the clear statistical significance of the influence of lightning on the nitrate concentrations, the robustness of the findings gradually decreases towards the determination of the radiative flux perturbations.

Sub-micrometer aerosol particles in the upper troposphere/lowermost stratosphere as measured by CARIBIC and modeled using the MIT-CAM3 global climate model

2012 ◽  
Vol 117 (D11) ◽  
pp. n/a-n/a ◽  
Author(s):  
Annica M. L. Ekman ◽  
Markus Hermann ◽  
Peter Groß ◽  
Jost Heintzenberg ◽  
Dongchul Kim ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Aerosol Particles ◽  
Upper Troposphere

INVESTIGATION OF RADAR AND ELECTRICAL CHARACTERISTICS OF THUNDERCLOUDS SEEDED WITH A GLACIOGENIC REAGENT IN KARNATAKA, INDIA

2021 ◽  
pp. 112-122
Author(s):  
A.A. SIN'KEVICH ◽  
◽  
B. BOE ◽  
S. PAWAR ◽  
YU. P. MIKHAILOVSKII ◽  
...  
Keyword(s):  
Network Data ◽  
Lightning Flash ◽  
Electrical Characteristics ◽  
North Caucasus ◽  
Flash Rate ◽  
Convective Clouds ◽  
The North ◽  
Lightning Detection ◽  
Karnataka State ◽  
Order Of Magnitude

Characteristics of developing convective clouds (Cu) in Karnataka state (India) during the thunderstorm formation are analyzed using weather radar and lightning detection network data. It is noted that radar characteristics of Cu which produced lightning, exceed those where lightning does not form. The study has shown that the number of negative cloud-to-ground strokes exceeds the number of positive ones by an order of magnitude. The radar characteristics of clouds in India and the North Caucasus are compared. Significant differences in lightning flash rates over the mentioned regions are registered. A low correlation is found between the supercooled volume and the flash rate of negative lightning. The paper also presents the results of studying the dynamic characteristics of four Cu seeded with a glaciogenic reagent. The thunderstorm risk is estimated for the clouds. It is shown that the seeding increases a probability of lightning events.

scholarly journals Characterising the seasonal and geographical variability in tropospheric ozone, stratospheric influence and recent changes

2019 ◽  
Vol 19 (6) ◽  
pp. 3589-3620 ◽  
Author(s):  
Ryan S. Williams ◽  
Michaela I. Hegglin ◽  
Brian J. Kerridge ◽  
Patrick Jöckel ◽  
Barry G. Latter ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Lower Stratosphere ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Data Availability ◽  
Ozone Production ◽  
Upper Troposphere ◽  
The World

Abstract. The stratospheric contribution to tropospheric ozone (O3) has been a subject of much debate in recent decades but is known to have an important influence. Recent improvements in diagnostic and modelling tools provide new evidence that the stratosphere has a much larger influence than previously thought. This study aims to characterise the seasonal and geographical distribution of tropospheric ozone, its variability, and its changes and provide quantification of the stratospheric influence on these measures. To this end, we evaluate hindcast specified-dynamics chemistry–climate model (CCM) simulations from the European Centre for Medium-Range Weather Forecasts – Hamburg (ECHAM)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model and the Canadian Middle Atmosphere Model (CMAM), as contributed to the International Global Atmospheric Chemistry – Stratosphere-troposphere Processes And their Role in Climate (IGAC-SPARC) (IGAC–SPARC) Chemistry Climate Model Initiative (CCMI) activity, together with satellite observations from the Ozone Monitoring Instrument (OMI) and ozone-sonde profile measurements from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) over a period of concurrent data availability (2005–2010). An overall positive, seasonally dependent bias in 1000–450 hPa (∼0–5.5 km) sub-column ozone is found for EMAC, ranging from 2 to 8 Dobson units (DU), whereas CMAM is found to be in closer agreement with the observations, although with substantial seasonal and regional variation in the sign and magnitude of the bias (∼±4 DU). Although the application of OMI averaging kernels (AKs) improves agreement with model estimates from both EMAC and CMAM as expected, comparisons with ozone-sondes indicate a positive ozone bias in the lower stratosphere in CMAM, together with a negative bias in the troposphere resulting from a likely underestimation of photochemical ozone production. This has ramifications for diagnosing the level of model–measurement agreement. Model variability is found to be more similar in magnitude to that implied from ozone-sondes in comparison with OMI, which has significantly larger variability. Noting the overall consistency of the CCMs, the influence of the model chemistry schemes and internal dynamics is discussed in relation to the inter-model differences found. In particular, it is inferred that CMAM simulates a faster and shallower Brewer–Dobson circulation (BDC) compared to both EMAC and observational estimates, which has implications for the distribution and magnitude of the downward flux of stratospheric ozone over the most recent climatological period (1980–2010). Nonetheless, it is shown that the stratospheric influence on tropospheric ozone is significant and is estimated to exceed 50 % in the wintertime extratropics, even in the lower troposphere. Finally, long-term changes in the CCM ozone tracers are calculated for different seasons. An overall statistically significant increase in tropospheric ozone is found across much of the world but particularly in the Northern Hemisphere and in the middle to upper troposphere, where the increase is on the order of 4–6 ppbv (5 %–10 %) between 1980–1989 and 2001–2010. Our model study implies that attribution from stratosphere–troposphere exchange (STE) to such ozone changes ranges from 25 % to 30 % at the surface to as much as 50 %–80 % in the upper troposphere–lower stratosphere (UTLS) across some regions of the world, including western Eurasia, eastern North America, the South Pacific and the southern Indian Ocean. These findings highlight the importance of a well-resolved stratosphere in simulations of tropospheric ozone and its implications for the radiative forcing, air quality and oxidation capacity of the troposphere.

scholarly journals Forecasting Lightning Threat Using Cloud-Resolving Model Simulations

2009 ◽  
Vol 24 (3) ◽  
pp. 709-729 ◽  
Author(s):  
Eugene W. McCaul ◽  
Steven J. Goodman ◽  
Katherine M. LaCasse ◽  
Daniel J. Cecil
Keyword(s):  
Numerical Models ◽  
Wrf Model ◽  
Phase Region ◽  
General Character ◽  
Lightning Flash ◽  
Flash Rate ◽  
Spatial Coverage ◽  
Physically Based ◽  
Cloud Resolving Model ◽  
Near Term

Abstract Two new approaches are proposed and developed for making time- and space-dependent, quantitative short-term forecasts of lightning threats, and a blend of these approaches is devised that capitalizes on the strengths of each. The new methods are distinctive in that they are based entirely on the ice-phase hydrometeor fields generated by regional cloud-resolving numerical simulations, such as those produced by the Weather Research and Forecasting (WRF) model. These methods are justified by established observational evidence linking aspects of the precipitating ice hydrometeor fields to total flash rates. The methods are straightforward and easy to implement, and offer an effective near-term alternative to the incorporation of complex and costly cloud electrification schemes into numerical models. One method is based on upward fluxes of precipitating ice hydrometeors in the mixed-phase region at the −15°C level, while the second method is based on the vertically integrated amounts of ice hydrometeors in each model grid column. Each method can be calibrated by comparing domain-wide statistics of the peak values of simulated flash-rate proxy fields against domain-wide peak total lightning flash-rate density data from observations. Tests show that the first method is able to capture much of the temporal variability of the lightning threat, while the second method does a better job of depicting the areal coverage of the threat. The blended solution proposed in this work is designed to retain most of the temporal sensitivity of the first method, while adding the improved spatial coverage of the second. Simulations of selected diverse North Alabama cases show that the WRF can distinguish the general character of most convective events, and that the methods employed herein show promise as a means of generating quantitatively realistic fields of lightning threat. However, because the models tend to have more difficulty in predicting the instantaneous placement of storms, forecasts of the detailed location of the lightning threat based on single simulations can be in error. Although these model shortcomings presently limit the precision of lightning threat forecasts from individual runs of current generation models, the techniques proposed herein should continue to be applicable as newer and more accurate physically based model versions, physical parameterizations, initialization techniques, and ensembles of forecasts become available.

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