Lightning serves as a sensitive indicator of deep convection and cloud microphysics, yet its response to aerosol variations remains uncertain over climatologically diverse regions. We investigate the coupled influence of aerosols, convective instability and cloud microphysical processes on lightning activity across six regions of India using long-term multi-satellite, reanalysis and radiosonde datasets (2001-2023). Results show strong spatial variability, with lightning flash rate density (LFRD) maximised over the northwest and northeast India and suppressed over central and arid western regions. Seasonal analysis reveals pre-monsoon and monsoon peaks, largely following convective available potential energy (CAPE), with minor regional offsets. Aerosol optical depth (AOD) exhibits a non-linear relationship with lightning. Moderate AOD enhances lightning under high CAPE (> 1000 J/kg), whereas excessive loading (> 0.6) combined with very high CAPE (similar to 1500-2000 J/kg) suppresses activity. Importantly, these thresholds vary regionally, associated with varying aerosol-lightning coupling. Aerosol type further modulates this behaviour: biomass-burning and urban aerosols invigorate lightning by enhancing cloud liquid and ice water content in the mixed-phase region, while dust and black carbon suppress lightning via radiative warming and stabilisation. Radiosonde and ERA5 profiles confirm mid-tropospheric heating, increased stability and reduced vertical velocity under high AOD in dust and black carbon-dominated regions. This study provides the first integrated, long-term evidence over India that aerosol impacts on lightning are non-linear and region-dependent, governed by CAPE thresholds, aerosol type and thermodynamic adjustments. The findings underscore the competing roles of microphysical invigoration and radiative suppression in shaping thunderstorm electrification, offering new insights for improving lightning parameterizations in weather and climate models.

Lightning causes substantial loss of life and infrastructure damage each year. This study presents the first numerical simulation of a severe pre-monsoon thunderstorm that occurred on 23 May 2023 over the complex western Himalayan region (WHR). We evaluate the performance of four WRF microphysics (MP) schemes in simulating lightning and rainfall using ground-based lightning observations and satellite-observed rainfall data. All MP schemes capture the observed temporal variability of lightning, but with notable differences in magnitude, timing, and variability. The Morrison scheme reproduces the timing of peak lightning activity at 15:00 UTC but substantially overestimates flash rates, whereas the Thompson, WDM5, and WSM6 schemes simulate the peak 1-2 hours earlier. Spatial analysis reveals dominant lightning activity along the Himalayan foothills, which is reasonably represented by all MP schemes. During the active convective phase, Morrison and Thompson simulate enhanced cloud water mixing ratios, supporting latent heat release and sustained convection. Elevated mixing ratios of rainwater, snow, and ice further indicate active mixed-phase processes favorable for cloud electrification. Temporal and spatial evaluations show that Thompson provides the closest agreement with observed lightning variability, while Morrison exhibits higher variability and false detections. Rainfall evaluation indicates improved detection skill for WSM6 and Morrison. Overall, the results demonstrate that no single microphysics scheme consistently outperforms others for both lightning and rainfall, highlighting non-uniform model skill across processes. These findings emphasize the need for region-specific and process-oriented tuning of model physics to improve lightning and rainfall simulations over complex mountainous terrain.

The COVID-19 lockdown (March–May 2020) caused an abrupt reduction in anthropogenic emissions, providing a natural experiment to examine the influence of aerosol and meteorological conditions on lightning activity over the Indian subcontinent. This study uses satellite and ground-based observations of aerosols, lightning, thermodynamic, and cloud microphysical parameters to determine whether the decrease in lightning was driven by reduced aerosol alone or by combined meteorological influences over the climatically contrasting Northeast (NE) and Northwest (NW) regions during the pre-monsoon season. The mean AOD decreased from 0.81 to 0.68 over the NE region and from 0.23 to 0.21 over the NW region during the lockdown. Similarly, ISS-LIS flash density (FD) declined from 0.00045 to 0.00034 flashes km-2 day-1 in the NE region and from 0.00016 to 0.00012 flashes km-2 day-1 in the NW region. During the lockdown, reduced CAPE and RH likely suppressed lightning over the NE region, whereas lower temperature and large droplets weakened electrification over the NW region. GPM-DPR observations showed a reduction in reflectivity and hydrometeor diameter in the mixed-phase region during the lockdown, consistent with observed reduction in lightning. Multifunction regression analysis indicated that meteorological variables showed strong statistical associations with lightning variability, not the aerosol alone, with CAPE as the prime predictor in the NE region and 2m temperature in the NW region, while AOD shows only a weak independent association. Our results indicate that the reduction in lightning during the COVID period reflects the combined impact of aerosol and meteorological variability rather than the effect of aerosol reduction alone.

Spatio-temporal variation of lightning characteristics over North India (NI) and North-East India (NEI) during the period 2001-2014 is studied in connection with the land use land cover (LULC) and topography of the Himalaya ranges. Lightning flashes detected by Lightning Imaging Sensor (LIS) on board the Tropical Rainfall Measuring Mission (TRMM) satellite are analysed for different LULC classes measured by Moderate Resolution Imaging Spectroradiometer (MODIS) and elevation data from Shuttle Radar Topography Mission (SRTM). We observed that the annual lightning flashes are high in the NI region compared to the NEI region; with a peak during monsoon period in the NI region, whereas peaks in the NEI were found to be during pre-monsoon months. The thermodynamics parameters such as maximum temperature (MaxT), convective available potential energy (CAPE), latent heat flux (LHF) and bulk microphysics such as total cloud cover liquid water (TCCLW) and total cloud cover ice water (TCCIW) along with lightning flash rate density (LFRD) also analysed with respect to different LULC classes. The impact of LULC on lightning activity is evident in both the study regions. In the both the region, human-induced landscapes such as croplands, urban built-up areas consistently show the high lightning activity due to favourable thermodynamic and microphysical conditions. Natural landscapes such as forest, grasslands show moderate lightning activity while savannas and permanent wetlands shows high lightning activity showing that vegetation helps in maintaining high soil moisture which may play a significant role in lightning occurrences. Topography significantly influenced lightning occurrence, with higher flash rates in foothill areas due to surface heating and moisture convergence, and in Meghalaya due to orographic lifting. Lightning activity in both study regions is higher at lower altitudes (<500m) and decreases with altitude, with a more prominent decline in case of NI region. We found the positive lightning trends in areas of expanding agriculture and urbanization highlighting the role of LULC change in the lightning distribution over both the regions.

Aerosol optical depth (AOD) and cloud top temperature (CTT) decreased in the Indo-Gangetic Plains (IGP) during the COVID-19 lockdown in India from March 23/25 to May 30, 2020, compared to the same period in 2017–2019. Aerosols, convective vigour, and moisture were pivotal in influencing the lightning flash rate (LFR) across various longitudinal belts. In the arid environment of the 70–82° E belt, coarse-mode mineral particles dominated, and LFR was low and inversely correlated with AOD. However, a fivefold increase in LFR in the 82–85° E belt was associated with the formation of deep convective clouds during the lockdown. In the 85–90° E belt, LFR declined during the lockdown but increased in 2017–2019, supporting the roles of mixed-phase processes in the dry and moist environments. AOD and aerosol extinction (AE) peaked at 0.8 and 1.5–1.6, respectively, at 88° E. In the moist environment of the 90–95° E belt, the influence of heat-absorbing aerosols diminished during the lockdown. Here, the vertical development of clouds was driven by the orography of hill ranges along the India-Myanmar border, rather than thermodynamic processes. Overall, both LFR and CTT declined with longitude due to decreased anthropogenic aerosols during the lockdown. Supporting evidence from related parameters reinforces these conclusions.

In this study, the observation site Himalayan Cloud Observatory is located at the high-altitude location (30.34 N, 78.40 E, 1706 m above mean sea level) and established at Swami Ram Tirth Campus, Badshahithaul, Tehri Garhwal, Uttarakhand in the western Himalaya. We have identified and characterized the new particle formation events for 12-months period (January to December 2021) of continuous monitoring of the aerosol size distribution using NanoScan Scanning Mobility Particle Sizer. We have observed 51 new particle formation events out of 278 days of observations having 14 % frequency of new particle formation occurrence. New particle formation events were most frequent in March-April-May (pre-monsoon) and least frequent in June-July-August-September (monsoon). This trend is linked to high temperatures, strong solar radiation, and low relative humidity in pre- monsoon, which enhance the formation of low-volatility organic compounds, while in monsoon, wet scavenging reduces aerosol precursor gases. The seasonal mean of growth rate (GR 11.5-27.4 nm ), formation rate (J11.5), coagulation sink (CoagS 11.5-27.4 ) and condensation sink (CSTOT, 11.5-154 nm) during the study period were 1.27 f 0.23 nm h-1, 0.12 f 0.08 cm-3 s-1, 2.92 f 1.65 x 10-5 s-1 and 9.91 f 3.13 x 10-3 s-1 respectively. Seasonal distributions show particles within 11.5-100 nm predominantly originate from secondary emissions, while particles 100-154 nm result from both direct and nucleated process, highlighting the seasonal sources of particles at Himalayan Cloud Observatory. A significant reduction (by 25 %) found in incoming solar radiation on nonevent days limits the oxidation of precursor gases, thereby inhibiting particle formation. Polar bivariate analysis reveals that winter airmasses, transported via mountain winds from the southwest and northeast, introduce mixed particle sizes. In contrast, the localized concentration of particles with elevated GR 11.5-27.4 nm and J 11.5 during pre-monsoon highlights the role of aerosol precursors, condensable vapours, and favorable meteorological conditions, emphasizing new particle formation as the dominant particle source. Comparison with prior cloud condensation nuclei study at Himalayan Cloud Observatory reveals that new particle formation significantly supplements cloud condensation nuclei production beyond primary emissions, especially in pre-monsoon. The satellite-based observation of sulfur dioxide and formaldehyde complement and support the condensable vapours during event days at Himalayan Cloud Observatory. In summary, this research offers fresh perspectives on the characterization of new particle formation events in the Himalayan region of Uttarakhand. These insights are crucial for comprehending secondary aerosol formation processes worldwide, particularly at the process level.

Atmospheric new particle formation (NPF, via gas-to-particle conversion) occurs commonly in the troposphere which has implications for air quality, weather, and climate. Here, we comprehensively characterize NPF events at the High Altitude Cloud Physics Laboratory (HACPL) in a mountain semi-rural location, Mahabaleshwar using 2.5 years of semi-continuous measurements of ion and particle number size distributions. The occurrence frequency of NPF events was the maximum in March through May (pre-monsoon season) (22.9%) compared to other seasons. Considering all seasons at HACPL, the particle growth rates in the size range from 3 to 7 nm, 7-25 nm, and 5-25 nm varied from 0.5 to 6.9 nm h-1, 1.3-10.2 nm h-1, and 1.5-16.4 nm h-1, respectively. The formation rate of charged clusters (J+3 and J-3) are reported for the first time from India, which ranges from 3.1 to 294.4 cm-3 s- 1. The general absence of a positive correlation between the particle formation rate and the growth rate indicates that dissimilar vapors might have contributed to the formation and growth of particles. Further, the role of ions in particle formation was also reported for the first time in India, which indicates an insignificant contribution of ions to particle formation at HACPL. At higher temperatures and lower relative humidity conditions, the formation rates of neutral/charged particles are found to be higher. Overall, our results provide new insights into NPF event characterization in the Indian context which have critical importance to an improved process-level understanding of secondary aerosol formation processes globally.

The impact of a severe dust storm that originated over the Arabian Peninsula (AP) and travelled to the Indian subcontinent during 20-26 January 2022 is examined. According to the event's synoptic analysis, the Gulf of Oman, adjacent areas of Oman and Iran had strong mid-lower tropospheric westerlies because of the configuration of north-south cyclonic and anticyclonic circulation patterns generated by a sizable north-south pressure gradient. A strong westerly wind component continued down to surface level and brought large quantities of dust from the desert region of the Middle East to the Indian subcontinent. Overall, 90% of the monitoring locations over the Indian subcontinent (mostly the western region) exceeded the national tolerable level of 100 mu g m(-3) (PM10), with peaks as high as 650 mu g m(-3). Changes in optical and physical properties of aerosols varied in accordance with the dust loading, in which absorption aerosol optical depth denotes a 10% increase in absorbing aerosols. Due to the excessive cooling effect, the near-surface air temperature dropped by -6 degrees C from its daily climatology over a sizable zone of high aerosol loading. Additionally, the dust storm prolonged the winter's harshness by lowering temperatures (from pre-dust days) in some of the most severely afflicted areas to 10-12 degrees C. Changes in wind patterns at mid- and low levels have resulted in a temperature inversion (similar to 2.5 km), which prevented trapped dust particles from being diluted, which in turn increased the likelihood of a more significant decline in air quality and affecting human health/wealth.

Spatiotemporal variations of biomass burning (BB) over the Indian region using satellite-based data from the Moderate Resolution Imaging Spectroradiometer (MODIS) for the period 2003–2021 are analyzed and studied. We have used fire products with a high confidence level (≥ 80

The analysis of Tropical Rainfall Measuring Mission-Lightning Imaging Sensor (TRMM-LIS) datasets indicates that lightning distribution in Uttarakhand significantly varies with elevation, peaking in the Himalayan foothills below 1500 m and decreasing above 4000 m. Furthermore, moderate (SLI 1–2) and mild (SLI 0–1) lightning hotspots have been identified in Uttarakhand. The monthly variations in lightning flash rate density (LFRD) and surface meteorological parameters show a moderate correlation of <0.6. However, the lag of 1 to 3 months in the meteorological parameter peak values from LFRD peak values does not support the cause-and-effect relation between them. However, LFRD is better correlated (r = 0.97) with the sensible heat fluxes (SHF). We found that the product of the Bowen ratio (BR) and convective rain rate (CRR) can serve as a good representative of lightning over this region. Principal component analysis (PCA) of the data reveals a strong relationship between LFRD and SHF, BR, the product of BR and CRR, maximum surface temperature (MST), CAPE, humidity, and CRR, emphasizing the impact of strong land surface heating, air parcel buoyancy, and deep convection on lightning. Cloud base height and latent heat flux (LHF) have weak correlations with LFRD. Eigenvalue loadings analysis indicated that CAPE, MST, humidity, and CRR are dominant factors in principal component (PC) PC1, while LFRD, BR, SHF, and the product of BR and CRR are dominant factors in PC2, influencing lightning over this region. This study offers valuable insights into the lightning distribution over Uttarakhand and its relationship with meteorological, topographical, and thermodynamic variables.

Surface measurements of the atmospheric electric field at the University of Kashmir, Srinagar (34° 13′ N, 74° 83′ E, 1585 m amsl) and Gulmarg (34° 05′ N, 74° 39′ E, 2617 m amsl) in the Kashmir Valley from March 2018 to August 2020 are analyzed to understand the behavior of the electric field during fair-weather, precipitation, snowfall, and fog conditions. The maximum thunderstorm activity observed in May, June, and July is attributed to the higher amount of moisture transport by western disturbances during May followed by the monsoon wind in June and July from the Bay of Bengal and the Arabian Sea. Based on the observations, in addition to the ordinary thunderstorms, several severe convective thunderclouds associated with the positive end-of-storm oscillations and inverted dipole structured clouds are also reported and explained. In addition, the observation of raindrop-induced field and periodic oscillations (90-min) in the potential gradient are explained in terms of the impact of the charge carried by the raindrops during precipitation, splashing on the ground and suspended snowflakes in snowfall episodes.

In recent years, the studies in global electric circuit (GEC) have received additional interest because of its potential to monitor climate and its use in representing the planets electrical subsystem in Earth system models. The new tools and climate models developed recently have improved our insight not only into various atmospheric processes involved in the GEC, but also in their mutual interactions on the local and global scales. The processes occurring within the atmosphere and outside it in space have been observed to influence the Earth's electrical environment. In this article, we summarize the work done in these directions and give some recommendations for better understanding of the GEC.

In this study, the evaluation of carbonaceous fine particulate matter (C-PM) was conducted using the SAFARIndia regional model. Two emission inventories were utilized: the newly developed SAFAR inventory and the global EDGAR-HTAP inventory, both for the year 2018. The simulation aimed to capture the seasonal and spatial patterns of black carbon (BC) and organic carbon (OC) concentrations. To validate model results, surface meteorological parameters, and C-PM concentrations were compared with the MERRA reanalysis data for the Indian region. Model simulated surface C-PM concentration with SAFAR emission inventory is found to be slightly overestimated (1.10), whereas simulated results with EDGAR emission inventory is significantly underestimated as compared to MERRA data. Model-simulated meteorological parameters showed a better correlation with MERRA reanalysis. Simulated geographical patterns of seasonal mean C-PM with SAFAR emission inventory exhibit quite a better comparison with MERRA reanalysis as against EDGAR simulated results. However, some differences in the present results are visible, particularly over the IGP region, as compared to MERRA data, but they are mainly attributed to a significant difference in the special resolution of present results (much finer) as compared to coarser MERRA data. In the Indo-Gangetic Plain (IGP) region, the concentration of BCSF and OCSF (BC and OC with SAFAR emission, respectively) show the peak during the winter, followed by the post-monsoon season. Although the correlation coefficients of hourly time series of surface BCSF and OCSF concentrations with MERRA over India are high (0.92 and 0.88), the poor RMSE, is attributed mainly to different scales of resolution. The model simulated BC, and OC concentrations with SAFAR emission input capture the pattern of spatial distribution reasonably well. The present evolution of BC and OC will help to better quantify their impact on climate and atmospheric conditions over the Indian region.

In the present study, continuous ground-based SO2 monitoring has been planned over the Srinagar Garhwal Valley of Uttarakhand. The monsoon (M-2018), post-monsoon (PoM-2018), winter (W-2019), pre-monsoon (PrM-2019), and M-2019 have high SO2 concentrations (3.66 ± 2.05 μg/m3, 5.54 ± 2.23 μg/m3, 6.42 ± 1.79 μg/m3, 7.56 ± 3.53 μg/m3 6.45 ± 3.49 μg/m3) at 1900, 2000, 1800, 1900, and 1900 local time attributed mainly due to biomass burning and long-range transportation of pollutants. A drastic change in the SO2 concentration was observed from 4.81 to 17.39 μg/m3 in May 2019 with a strong correlation of 0.61 with fire counts during an extensive forest fire. Due to the wet scavenging process, Jul 2018 (1.07 ± 0.82 μg/m3) showed the lowest SO2 concentration. Temperature, humidity, and wind speed significantly correlate with SO2 in different seasons. Overall, the air quality in the SGV region is good, but it worsens during forest fires, although it still remains within satisfactory levels. HYSPLIT model trajectories, cluster, and CWT analysis indicate the transportation of air mass from the Gulf region, Sahara Desert, Pakistan, and Afghanistan to Srinagar with a significant contribution of 40.43 to 72.29

Product of Bowen ratio with the sum of precipitation rate and evaporation rate has been used as proxy to evaluate the seasonal and annual spatial distributions of lightning flash rate over South/Southeast Asian region (60–120° E, 0–40° N) with 9 models from the Coupled Model Inter-comparison Project-Phase 5 (CMIP5). The model-simulated mean LFR with each model is positively correlated with the satellite-observed LFR on both seasonal and annual scales. The satellite-observed LFR is correlated with the ensemble mean LFR of the models with a correlation coefficient of 0.93 over the region. The model-simulated LFR has also been used for projection of lightning in the late twenty-first century. Overall, the projected LFR over whole study area shows a 6.75% increase during the (2079–2088) period in high radiative forcing scenario (RCP8.5) as compared to the historic period of (1996–2005). Rise in LFR is also identified using another projected period (2051–2060) and a lower radiative forcing scenario condition (RCP4.5), though lesser in magnitude, as expected. For the projected period (2051–60) in the RCP8.5 case, LFR over the domain shows an increase of 4.3%; whereas for a lower future scenario condition (RCP4.5), it indicates a rise by 5.36% at the end of the twenty-first century. Moreover, results indicate an increase in extreme events of severe convective storms with intense lightning in mountainous dry regions at the end of the twenty-first century. It is suggested that the proxy used here is favourable for projection of LFR in this region and perhaps for the whole tropical area.

Impacts of environmental changes at Pune, India during the lockdown period imposed due to the Covid-19 pandemic, on the characteristics of the atmospheric ions and the new particle formation (i.e. the formation of molecular clusters and their subsequent growth to larger sizes) and shrinkage events have been investigated. The increase in the small and big cluster ion concentrations and the decrease in intermediate ion concentrations observed during the lockdown period have been associated with the decrease in the aerosols and precursor gases, respectively. During the NPF events, the nucleation mode particles of both polarities grow in size. However, during the unique shrinkage events observed here, particles increase in concentration but do not grow in size during the morning-to-noon period and shrink in the noon-to-evening period during the lockdown period. Simultaneously, the concentration of particles of >25 nm decrease i during the morning hours and increase during the afternoon hours .On the shrinkage event days, solar irradiance is higher and relative humidity is lower throughout the day than on the NPF/no-event days. Occurrence of shrinkage events has been proposed to be associated with the change in saturation vapour pressure of different chemical species with temperature/solar irradiance.

The Indo-Gangetic basin is one of the biggest, most populated and polluted regions in the world. Satellite- and ground-based data show strong seasonal variability of aerosol loading with a maximum during pre-monsoon (summer) season. In this study, decadal (2003–2012) variability of aerosol optical depth (AOD) derived from AERONET measurements over Kanpur is presented which indicates maximum AOD during 2003 and minimum during 2012. The aerosol size distribution (ASD) exhibits an increase in the radius and a decrease in the width of distribution. It shows an enhancement during 2003 and 2010 and diminished values during 2004, 2007, 2009 and 2011. The ASD is found to show a peak during summer season (pre-monsoon) throughout 2003–2012 only except the years 2008 and 2011. Moreover, for years 2008 and 2011 ASD showed a peak value during a monsoon month (July). Changes in the spectrum of ASD are explained in terms of surface temperature and precipitation. Seasonal variation of aerosol radiative forcing and its climatic impacts have also been discussed.

The current study is mainly focused on the monthly variation in the lightning flash rate (LFR) and related thermodynamic parameters using the data for the years 2000–2013, and the trend of lightning variation is explored. Lightning data are used from a lightning imaging sensor (LIS) and an optical transient detector (OTP) boarded on the tropical rainfall measuring mission (TRMM). Additionally, aerosol optical depth (AOD) data at 550 nm for the same period were considered from a Moderate Resolution Imaging Spectroradiometer (MODIS). The assessment of lightning and AOD using monthly data makes it difficult to study seasonal contributions, and higher-resolution (hourly) data may be more appropriate, but unfortunately, no data were available with a higher resolution than monthly. The dependency of LFR is also investigated using thermodynamic/dynamic parameters. The LFR shows a moderate correlation with a correlation coefficient of 0.56, 0.62, and 0.63 for AOD, CAPE, and vertical velocity, respectively. The increasing AOD in the pre-monsoon season is associated with higher lightning flash rates over this region. The possible sources of aerosols that cause an increase in lightning activities are identified from the classification of aerosols based on the characteristic values of the AOD and the Ångström exponent. The thermodynamic relation of the Product of Bowen ratio with the sum of the precipitation rate and evaporation rate has been used as a proxy to evaluate the lightning flash rate density over Srinagar, Uttarakhand region (78.55° E–79.05° E, 29.97° N–30.47° N), with nine models from the Coupled Model Inter-comparison Project-Phase 5 (CMIP5). The model-simulated LFR has also been used for the projection of lightning in the late 21st century, and the projected LFR over the study area shows a 7.41% increase during the (2079–2088) period as compared to the historic period (1996–2005). The results of the study region indicate caution in using any single climate variable as a proxy for projecting a change in the lightning–climate relationships in the scenario of global warming.

In the present study, the atmospheric electric field observations are reported at Gulmarg station, Kashmir (34°05′N; 74°42′E) for a period of 1 year: June 2019–May 2020. The observation site is situated in an area with high thunderstorm activity and very high radon concentration. Diurnal characteristics of PG are explained with electrode effect under summer/dry surface conditions and evaporation effect under winter/wet surface conditions associated with sunrise. The latter effect is highly responsible for the diurnal peak of PG observed in afternoon (1300 LT) hours along with the water vapour pressure under low temperature. Similarly, excess positive charges found at the electrode layer shift the diurnal peak to an earlier time ~1000–1100 LT under turbulent exchange from the surface. Therefore, the annual mean curve is the resultant of these two effects that act in different seasons. In addition, the annual diurnal variation of the potential gradient is in agreement with some other continental stations having two maxima and higher values of PG during the winter months. The secondary diurnal maximum (2000 LT) is likely due to African thunderstorm activity being reflected strongly at our measurement site. Comparison of our results with Carnegie leads to a weak correlation between the two, which is due to the difference in the nature of observation sites, while a comparison with the observations of B N Raina (August 1970–October 1973) at the same observatory reveals a similar nature of PG variation. Finally, simple correlation plots of PG with meteorological parameters and radon concentration have been shown. The results indicate that radon concentration and meteorological parameters like temperature, relative humidity in addition to water vapour pressure are important local factors influencing the surface PG measurements at our site.

Based on the large exchange of heat fluxes on the Earth's surface in the tropics, we propose that the lightning flash rate (LFR) is proportional to a product of the Bowen ratio and the sum of precipitation and evaporation rates. The proposed relationship is justified on the basis of the conversion of the kinetic energy of charging hydrometeors to the energy of flash discharges. However, the proportional relationship varies depending on the season. This product explains 90% of the variance in the monthly-averaged time series of the total LFR over our study area of 0° N-40° N and 60° E-120° E including south/southeast Asia and some part of southern China. The conversion efficiency is a maximum in the pre-monsoon season and minimum in the winter season. The total heat flux best accounts for the seasonal variation of the LFR.