Introducing new lightning schemes into the CHASER (MIROC) chemistry–climate model

• Published in: Geoscientific Model Development 2022-07, Vol.15 (14), p.5627-5650
• Main Authors: He, Yanfeng, Hoque, Hossain Mohammed Syedul, Sudo, Kengo
• Format: Article
• Language: English
• Subjects: Accuracy; Aerosols; Aircraft; Aircraft observations; Atmosphere; Atmospheric chemistry; Atmospheric models; Capes (landforms); Chemical reactions; Chemical transport; Chemistry; Climate; Climate change; Climate models; Convective available potential energy; Convective clouds; Distribution; Emissions; Evaluation; Global warming; Graupel; Height; Hydrometeors; International marketing; Lightning; Lightning activity; Lightning flashes; Modelling; Monitoring instruments; Nitrogen compounds; Nitrogen dioxide; Nitrogen oxide; Nitrogen oxides; Oxidation; Photochemicals; Potential energy; Precipitation; Predictions; Satellite observation; Spatial distribution; Surface temperature; Temperature; Tomography; Trends; Troposphere; Upper troposphere; VOCs; Volatile organic compounds; Weather; Weather forecasting
• ISSN: 1991-9603; 1991-959X; 1991-962X; 1991-9603; 1991-962X
• DOI: 10.5194/gmd-15-5627-2022

The formation of nitrogen oxides (NOx) associated with lightning activities (hereinafter designated as LNOx) is a major source of NOx. In fact, it is regarded as the dominant NOx source in the middle to upper troposphere. Therefore, improving the prediction accuracy of lightning and LNOx in chemical climate models is crucially important. This study implemented three new lightning schemes with the CHASER (MIROC) global chemical transport and climate model. The first lightning scheme is based on upward cloud ice flux (ICEFLUX scheme). The second one (the original ECMWF scheme), also adopted in the European Centre for Medium-Range Weather Forecasts (ECMWF) forecasting system, calculates lightning flash rates as a function of QR (a quantity intended to represent the charging rate of collisions between graupel and other types of hydrometeors inside the charge separation region), convective available potential energy (CAPE), and convective cloud-base height. For the original ECMWF scheme, by tuning the equations and adjustment factors for land and ocean, a new lightning scheme called the ECMWF-McCAUL scheme was also tested in CHASER. The ECMWF-McCAUL scheme calculates lightning flash rates as a function of CAPE and column precipitating ice. In the original version of CHASER (MIROC), lightning is initially parameterized with the widely used cloud-top height scheme (CTH scheme). Model evaluations with lightning observations conducted using the Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) indicate that both the ICEFLUX and ECMWF schemes simulate the spatial distribution of lightning more accurately on a global scale than the CTH scheme does. The ECMWF-McCAUL scheme showed the highest prediction accuracy for the global distribution of lightning. Evaluation by atmospheric tomography (ATom) aircraft observations (NO) and tropospheric monitoring instrument (TROPOMI) satellite observations (NO2) shows that the newly implemented lightning schemes partially facilitated the reduction of model biases (NO and NO2), typically within the regions where LNOx is the major source of NOx, when compared to using the CTH scheme. Although the newly implemented lightning schemes have a minor effect on the tropospheric mean oxidation capacity compared to the CTH scheme, they led to marked changes in oxidation capacity in different regions of the troposphere. Historical trend analyses of flash and surface temperatures predicted using CHASER (2001–2020) show that li