Lightning Imaging Sensor Research Articles

The lightning activity associated with the dry and moist convections in the Himalayan Regions

AbstractLightning activity in the dry environment of northwest India and Pakistan (NW) and in the moist environment of northeast India (NE) has been examined from the Optical Transient Detector and Lightning Imaging Sensor data obtained from the Tropical Rainfall Measuring Mission satellite during 1995–2010. In the NW region, seasonal variation of flash rate is annual with a maximum in July but is semi‐annual with a primary maximum in April and a secondary maximum in September, in the NE region. On diurnal scale, flash rate is the maximum in the afternoons, in both the NE and NW regions. The correlation of flash rate with convective parameters, viz. surface temperature, convective available potential energy (CAPE) and outgoing long‐wave radiation is better with convective activity in the NW than in the NE region. Mean value of aerosol optical depth at 550 nm is ~ 26% higher and is highly correlated with flash rate in NW as compared to that in NE. Results indicate that CAPE is ~ 120 times more efficient in NW than in the NE region for production of lightning. The empirical orthogonal function analysis of flash rate, surface temperature, and CAPE shows that variance of lightning activity in these regions cannot be fully explained by the variance in the surface temperature and CAPE alone, and that some other factors, such as orographic lifting, precipitation, topography, etc., may also contribute to this variance in these mountainous regions. Further, the increase in CAPE due to orographic lifting in the Himalayan foothills in the NE region may contribute to ~ 7.5% increase in lightning activity. Relative roles of the thermally induced and moisture‐induced changes in CAPE are examined in these regions. This study merely raises the questions, and that additional research is required for explaining the fundamental reasons for the reported observations here.

Terrestrial gamma‐ray flashes in the Fermi era: Improved observations and analysis methods

A new data mode and new analysis methods are used to detect Terrestrial Gamma‐ray Flashes (TGFs) with the Fermi Gamma‐ray Burst Monitor (GBM) 10 times more frequently than previously. In 1037 h of observations at times and over regions for which TGFs are expected, 384 new TGFs were found in addition to the 39 TGFs and two Terrestrial Electron Beam events already detected without the new data mode and methodology. Cosmic ray showers were found to be an important background; they show characteristic signatures in the data of both GBM and the Fermi Large Area Telescope Calorimeter that enable their removal, leaving a sample estimated to consist of ≈98% TGFs. The sample includes shorter TGFs than previously found with GBM. The true duration distribution likely contains additional short TGFs because their detection by GBM is limited by detector dead time. One‐third of this sample has matches with locations from the World Wide Lightning Location Network (WWLLN)—maps of these locations show the geographic and meteorological features more clearly than maps of spacecraft locations. The intrinsic TGF rate is evaluated using the lightning rate maps of the Lightning Imaging Sensor, accounting for the detection efficiency of GBM as a function of spacecraft‐source offset, from which we estimate a global TGF rate of ≈400,000 per year. With continuous production of data in the new mode we estimate that GBM will detect ≈850 TGFs per year.

Radiated VLF energy differences of land and oceanic lightning

A global contrast between oceanic and continental lightning very low frequency energy is observed using the World Wide Lightning Location Network (WWLLN). Strokes over the ocean are found to be stronger on average than those over land with a sharp boundary along a majority of coastlines. A linear regression method is developed to account for the spatial and temporal variation of WWLLN in order to perform a multiyear and global analysis of stroke energy distributions. The results are corroborated with data from the Lightning Imaging Sensor, the Optical Transient Detector, and the Earth Networks Total Lightning Network. These systematic comparisons lead to the conclusion that there exists a strong difference in the energetics between land and ocean thunderstorms that results in a higher fraction of more powerful strokes over the oceans.

Evaluating WWLLN performance relative to TRMM/LIS

AbstractThis study evaluates 4 years (2009–2012) of World Wide Lightning Location Network (WWLLN) data relative to the Tropical Rainfall Measuring Mission Lightning Imaging Sensor (LIS). In the Western Hemisphere, between 38°N and 38°S, the WWLLN detection efficiency (DE) (of LIS flashes) steadily improves from 6% during 2009 to 9.2% during 2012. The WWLLN is approximately three times more likely to detect a LIS flash over the ocean (17.3%) than over land (6.4%), and DE values greater than 20% only occur over the oceans. An average of 1.5 WWLLN strokes occurs during each matched LIS flash, but 71.5% of matched flashes are single stroke. Matched LIS flashes have more events/groups, longer durations, and larger areas than non‐matched flashes. The close spatial proximity (11 km) and temporal proximity (+62 ms) between matched WWLLN and LIS flashes are important for Geostationary Lighting Mapper risk reduction studies that use existing networks to develop proxy data sets.

Lightning distribution with respect to the monsoon trough position during the Indian summer monsoon season

The location and shift in the position of the maximum lightning activity with respect to the position the of monsoon trough has been investigated in the region of 20°N–32°N and 75°E–95°E during the Indian summer monsoon seasons of 2002 and 2003 from the lightning imaging sensor (LIS) data from the Tropical Rainfall Measuring Mission (TRMM) satellite. The polynomial curve fitting the maximum lightning activity followed the position of the monsoon trough in both the normal monsoon and drought years. Observations of the maximal lightning activity in the TRMM‐LIS data collected during a period of 13 years, from 1998 to 2010, confirm these findings in the monsoon season. When the seasonal position of the monsoon trough moved from the plains to the submontane region of the Himalayas during a monsoon break period, the polynomial fitting of the maximum lightning activity also moved from the central Indian plains to that region. An empirical orthogonal function (EOF) analysis is applied to two different data sets of precipitation and observed high lightning flash rates over the monsoon trough region for the period of 1995–2005. The first and second components, EOF1 and EOF2, of precipitation values are out of phase with those of the flash rates. Our results imply that deep electrified convective systems during monsoon periods are responsible for the lightning activity in the monsoon trough region and that the lightning activity in this region can be used as a proxy for the location and shift of the seasonal monsoon trough.

Spatial patterns of diurnal variations in summer-season lightning activity across the tropical and subtropical regions of the Northern Hemispheric Americas

Hourly lightning data were obtained from the Tropical Rainfall Measuring Mission dataset collected through the Lightning Imaging Sensor instrument from 1998 to 2011 to analyze the diurnal pattern of lightning activity in the tropical and subtropical northern hemispheric Americas. The majority of the lightning strikes occurred over land, with relatively lower strike rates over the oceanic areas. The results of our studies showed substantial spatial variations in the time of maximum and strength of the diurnal cycle in the study area. A clockwise progression in the time of maximum was observed across most of the study area, particularly over North America where an east–west orientation was observed. The findings of our study were mainly a result of the interaction between local topography such as the Andes and Rocky mountains, and surface level atmospheric circulations. The strength of the observed diurnal cycle was greatest in the Gulf of Mexico region.

The Filtering of the Energetic Particle Noise Captured by the Geostationary Lightning Image Sensor

The Filtering of the Energetic Particle Noise Captured by the Geostationary Lightning Image Sensor

The GOES-R Geostationary Lightning Mapper (GLM)

The Geostationary Operational Environmental Satellite R-series (GOES-R) is the next block of four satellites to follow the existing GOES constellation currently operating over the Western Hemisphere. Advanced spacecraft and instrument technology will support expanded detection of environmental phenomena, resulting in more timely and accurate forecasts and warnings. Advancements over current GOES capabilities include a new capability for total lightning detection (cloud and cloud-to-ground flashes) from the Geostationary Lightning Mapper (GLM), and improved cloud and moisture imagery with the 16-channel Advanced Baseline Imager (ABI). The GLM will map total lightning activity continuously day and night with near-uniform storm-scale spatial resolution of 8km with a product refresh rate of less than 20s over the Americas and adjacent oceanic regions in the western hemisphere. This will aid in forecasting severe storms and tornado activity, and convective weather impacts on aviation safety and efficiency. In parallel with the instrument development, an Algorithm Working Group (AWG) Lightning Detection Science and Applications Team developed the Level 2 (stroke and flash) algorithms from the Level 1 lightning event (pixel level) data. Proxy data sets used to develop the GLM operational algorithms as well as cal/val performance monitoring tools were derived from the NASA Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) instruments in low Earth orbit, and from ground-based lightning networks and intensive prelaunch field campaigns. The GLM will produce the same or similar lightning flash attributes provided by the LIS and OTD, and thus extend their combined climatology over the western hemisphere into the coming decades. Science and application development along with preoperational product demonstrations and evaluations at NWS forecast offices and NOAA testbeds will prepare the forecasters to use GLM as soon as possible after the planned launch and checkout of GOES-R in late 2015. New applications will use GLM alone, in combination with the ABI, or integrated (fused) with other available tools (weather radar and ground strike networks, nowcasting systems, mesoscale analysis, and numerical weather prediction models) in the hands of the forecaster responsible for issuing more timely and accurate forecasts and warnings.

Electrically Active Convection in Tropical Easterly Waves and Implications for Tropical Cyclogenesis in the Atlantic and East Pacific

Abstract In this study, the authors investigated the characteristics of tropical easterly wave convection and the possible implications of convective structure on tropical cyclogenesis and intensification over the Atlantic Ocean and the east Pacific Ocean. Easterly waves were partitioned into northerly, southerly, trough, and ridge phases based on the 700-hPa meridional wind from the National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis dataset. Waves were subsequently divided according to whether they did or did not develop tropical cyclones (i.e., developing and nondeveloping, respectively), and developing waves were further subdivided according to development location. Finally, composites as a function of wave phase and category were created using data from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager, Precipitation Radar (PR), and Lightning Imaging Sensor as well as infrared (IR) brightness temperature data from the NASA global-merged IR brightness temperature dataset. Results suggest that the convective characteristics that best distinguish developing from nondeveloping waves vary according to where developing waves spawn tropical cyclones. For waves that develop a cyclone in the Atlantic basin, coverage by IR brightness temperatures ≤240 and ≤210 K provide the best distinction between developing and nondeveloping waves. In contrast, several variables provide a significant distinction between nondeveloping waves and waves that develop cyclones over the east Pacific as these waves near their genesis location including IR threshold coverage, lightning flash rates, and low-level (<4.5 km) PR reflectivity. Results of this study may be used to help develop thresholds to better distinguish developing from nondeveloping waves and serve as another aid for tropical cyclogenesis forecasting.

Spatial and time distribution of the flash rate over tropical Africa

The lightning flash rate over tropical Africa was analyzed using lightning data of two independent lightning detection systems, the World Wide Lightning Location Network and the Lightning Imaging Sensor. Spatial and time distributions of lightning activity were studied using different spatial and temporal scales. Results show a very localized high-lightning activity center on the west side of the Albertine Rift Mountain, located east of the Congo Basin, and substantial lightning activity in the center of the region. Both centers show low variations on the lightning activity throughout the year and a marked diurnal cycle with a maximum lightning activity in the local afternoon. A secondary lightning activity center was found over Lake Victoria, which has an annual variation similar to that of the Congo Basin lightning activity centers but does not show a marked diurnal cycle. The lightning activities observed seem to be strongly influenced by topography and are in agreement with the small temperature ranges and with the rainfall observed in the region.

Application of lightning to passive microwave convective and stratiform partitioning in passive microwave rainfall retrieval algorithm over land from TRMM

This study analyzes relationships between lightning flash rate, radar reflectivity factor (reflectivity), and passive microwave brightness temperature (Tb) for convective and stratiform precipitation over land using multiyear data from the Tropical Rainfall Measuring Mission (TRMM) satellite. A new convective and stratiform index (CSI (an estimate of convective areal fraction)) for the TRMM Microwave Imager (TMI) is developed from the analysis. Four years of TRMM TMI, Lightning Imaging Sensor (LIS), and Precipitation Radar (PR) data (2002–2005) are colocated and remapped to 0.1 and 0.05 degree grids for analysis. The scientific objective of this study is to understand the relationship between lightning and active and passive microwave precipitation observations and explore ways of using lightning information to enhance the discrimination between convective and stratiform precipitation in TMI rain rate retrieval algorithm. PR provides the reference convective and stratiform classification and is coincident with LIS which reports lightning parameters such as the occurrence (yes or no) and flash rates. Analysis of ∼14 million coincident precipitating TRMM measurements over land (i.e., excluding oceans and coasts) reveals that 6% of rain data have lightning flash rates greater than zero. For all lightning data, 60% have 0–1 fl min−1, 28% have 1–2 fl min−1, and 12% have flash rates greater than 2 fl min−1. Overall, 86.5% (13.5%) of lightning occurred in convective (stratiform) precipitation. In other words, stratiform rainfall is predominant when LIS detects no lightning, and the convective rain probability increases with increasing lightning frequency. For example, 34% of rainfall is convective for low flash rates (0–1 fl/min), whereas the convective probability increases to 99.7% for high flash rates (>=2 fl/min). This study develops a simple method that incorporates lightning into the CSI to test if lightning can help passive microwave (PM) delineate convective and stratiform precipitation. LIS lightning occurrence and flash rates (i.e., no flash, 0–1 fl/min, 1–2 fl/min, and >2 fl/min) are used to preclassify TMI Tbs into four groups of increasing convective probability. Multivariable linear regression is then applied to each group to derive the CSI. Results reveal that lightning information primarily improves the identification of highly convective rainfall by correctly shifting microwave observations previously identified as moderate to highly convective. Alternatively, the absence of lightning also helps PM to identify likely stratiform. Overall, including lightning information results in a decrease of bias error of 6% and a small increase in RMS error of 4.5% on the entire range of rainfall rates.

Disparity in the characteristic of thunderstorms and associated lightning activities over dissimilar terrains

Thunderstorms and associated lightning flash activities are studied over two different locations in India with different terrain features. Lightning imaging sensor (LIS) data from 1998 to 2008 are analyzed during the pre-monsoon months (March, April and May). The eastern sector is designated as Sector A that represents a 2° × 2° square area enclosing Kolkata (22.65°N, 88.45°E) at the centre and covering Gangetic West Bengal, parts of Bihar and Orissa whereas the north-eastern sector designated as Sector B that also represents a 2° × 2° square area encircling Guwahati (26.10°N, 91.58°E) at the centre and covering Assam and foot hills of Himalaya of India. The stations Kolkata and Guwahati are selected for the present study from Sector A and Sector B, respectively, as these are the only stations over the selected areas having Radiosonde observatory. The result of the present study reveals that the characteristics of thunderstorms over the two locations are remarkably different. Lightning frequency is observed to be higher in Sector B than Sector A. The result further reveals that though the lightning frequency is less in Sector A, but the associated radiance is higher in Sector A than Sector B. It is also observed that the radiance increases linearly with convective available potential energy (CAPE) and their high correlation reveals that the lightning intensity can be estimated through the CAPE values. The sensitivity of lightning activity to CAPE is higher at the elevated station Guwahati (elevation 54 m) than Kolkata (elevation 6 m). Moderate resolution imaging spectrometer (MODIS) data products are used to obtain aerosol optical depth and cloud top temperature and employed to find their responses on lightning radiance.

Nowcasting lightning flash rate and peak wind gusts associated with severe thunderstorms using remotely sensed TRMM-LIS data

The momentous weather hazards during the pre-monsoon season (April–May) over Kolkata (22° 32′ N, 88° 20′ E), India, is mostly due to lightning flashes and surface wind gusts associated with severe thunderstorms. A multi-layer perceptron (MLP) model is developed to forecast the lightning flash rate and peak wind gusts which accompany severe thunderstorms. Meteorological parameters derived from radiosonde weather observations from 1998 to 2009 are taken as input whereas lightning data from the Lightning Imaging Sensor (LIS) and wind gusts from a ground-based observatory are taken as the target output parameters. The skill of the MLP model is compared with the multiple linear regression (MLR) analysis method, and it is observed that the MLP model provides better and more accurate forecasts than the MLR analysis method. The results also reveal that the forecast accuracy is more for surface wind gusts than for the lightning flash rate, both during training and validation of the model. The MLP model forecast is validated with the India Meteorological Department (IMD) weather observations as well as Doppler weather radar and satellite imagery of 2008 and 2009 thunderstorms.

Optimized regional and interannual variability of lightning in a global chemical transport model constrained by LIS/OTD satellite data

Nitrogen oxides (NOx ≡ NO + NO2) produced by lightning make a major contribution to the global production of tropospheric ozone and OH. Lightning distributions inferred from standard convective parameterizations in global chemical transport models (CTMs) fail to reproduce observations from the Lightning Imaging Sensor (LIS) and the Optical Transient Detector (OTD) satellite instruments. We present an optimal regional scaling algorithm for CTMs to fit the lightning NOxsource to the satellite lightning data in a way that preserves the coupling to deep convective transport. We show that applying monthly scaling factors over ∼37 regions globally significantly improves the tropical ozone simulation in the GEOS‐Chem CTM as compared to a simulation unconstrained by the satellite data and performs equally well to a simulation with local scaling. The coarse regional scaling preserves sufficient statistics in the satellite data to constrain the interannual variability (IAV) of lightning. After processing the LIS data to remove their diurnal sampling bias, we construct a monthly time series of lightning flash rates for 1998–2010 and 35°S–35°N. We find a correlation of IAV in total tropical lightning with El Niño but not with the solar cycle or the quasi‐biennial oscillation. The global lightning NOxsource ± IAV standard deviation in GEOS‐Chem is 6.0 ± 0.5 Tg N yr−1, compared to 5.5 ± 0.8 Tg N yr−1 for the biomass burning source. Lightning NOx could have a large influence on the IAV of tropospheric ozone because it is released in the upper troposphere where ozone production is most efficient.

The reciprocal relation between lightning and pollution and their impact over Kolkata, India

Aerosol loading in the atmosphere can cause increased lightning flashes, and those lightning flashes produce NOX , which reacts in sun light to produce surface ozone. The present study deals with the effect of surface pollutants on premonsoon (April-May) lightning activity over the station Kolkata (22.65° N, 88.45° E). Seven-year (2004-2010) premonsoon thunderstorms data are taken for the study. Different parameters like aerosol optical depth and cloud top temperature from the Moderate Resolution Imaging Spectroradiometer satellite products along with lightning flash data from Tropical Rainfall Measuring Mission's (TRMM) Lightning Imaging Sensor are analyzed. Some surface pollution parameters like suspended particulate matter, particulate matter 10, nitrogen oxides (NOX), and surface ozone (O₃) data during the same period are taken account for clear understanding of their association with lightning activity. Heights of convective condensation level and lifting condensation level are collected from radiosonde observations to anticipate about cloud base. It is found that increased surface pollution in a near storm environment is related to increased lightning flash rate, which results in increased surface NOX and consequently increased surface ozone concentration over the station Kolkata.

Seasonal variations in the lightning diurnal cycle and implications for the global electric circuit

Data obtained from the Optical Transient Detector and the Lightning Imaging Sensor satellites (70° and 35° inclination low earth orbits, respectively) are used to statistically determine the number of flashes in the seasonal diurnal cycle as a function of local and universal time. These data include corrections for detection efficiency and instrument view time. They are further subdivided by season, land versus ocean, and other spatial (e.g., continents) and temporal (e.g., time of peak diurnal amplitude) categories. These statistics are then combined with analyses of high altitude aircraft observations of electrified clouds to produce the seasonal diurnal variation in the global electric circuit. Continental results display strong diurnal variation, with a lightning peak in the late afternoon and a minimum in late morning. In geographical regions dominated by large mesoscale convective systems, the peak in the diurnal curve shifts toward late evening or early morning hours. The maximum seasonal diurnal flash rate occurs in June–August, corresponding to the Northern Hemisphere summer, while the minimum occurs in December–February. Summer lightning dominates over winter activity and springtime lightning dominates over fall activity at most continental locations. Oceanic lightning exhibits minimal diurnal variation, but morning hours are slightly enhanced over afternoon. As was found earlier, for the annual diurnal variation, using basic assumptions about the mean storm currents as a function of flash rate and location (i.e., land/ocean), our seasonal estimates of the current in the global electric circuit provide an excellent match with independent measurements of the seasonal Carnegie curve diurnal variations. The maximum (minimum) total mean current of 2.4kA (1.7kA) is found during Northern Hemisphere summer (winter). Land thunderstorms supply about one half (52%) of the total global current. Ocean thunderstorms contribute about one third (31%) and the non-lightning producing ocean electrified shower clouds (ESCs) supply one sixth (15%) of the total global current. Land ESCs make only a small contribution (2%).

Erratum to: Influence of the Pacific quasi-decadal oscillation on the monsoon precipitation in Nepal

Fig. 1 a July–August climatology of precipitation (contours; mm/day) and the topography (shadings), and b annual lightning frequency between 1997 and 2002 derived from the Lightning Imaging Sensor onboard the TRMM satellite and between 1995 and 2000 by the Optical Transient Detector (Source: NASA Earth Observatory Webpage). The black dot in a marks Kathmandu, Nepal’s capital city The online version of the original article can be found under doi:10.1007/s00382-012-1376-2.

Gridded lightning climatology from TRMM-LIS and OTD: Dataset description

Gridded climatologies of total lightning flash rates observed by the spaceborne Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) instruments have been updated. OTD collected data from May 1995 to March 2000. LIS data (equatorward of about 38°) adds the years 1998–2010. Flash counts from each instrument are scaled by the best available estimates of detection efficiency. The long LIS record makes the merged climatology most robust in the tropics and subtropics, while the high latitude data is entirely from OTD. The gridded climatologies include annual mean flash rate on a 0.5° grid, mean diurnal cycle of flash rate on a 2.5° grid with 24hour resolution, mean annual cycle of flash rate on a 0.5° or 2.5° grid with daily, monthly, or seasonal resolution, mean annual cycle of the diurnal cycle on a 2.5° grid with two hour resolution for each day, and time series of flash rate over the sixteen year record with roughly three-month smoothing. For some of these (e.g., annual cycle of the diurnal cycle), more smoothing is necessary for results to be robust.The mean global flash rate from the merged climatology is 46flashess−1. This varies from around 35flashess−1 in February (austral summer) to 60flashess−1 in August (boreal summer). The peak annual flash rate at 0.5° scale is 160flkm−2yr−1 in eastern Congo. The peak monthly average flash rate at 2.5° scale is 18flkm−2mo−1 from early April to early May in the Brahmaputra Valley of far eastern India. Lightning decreases in this region during the monsoon season, but increases further north and west. An August peak in northern Pakistan also exceeds any monthly averages from Africa, despite central Africa having the greatest yearly average.

Variability of lightning activity in South/Southeast Asia during 1997–98 and 2002–03 El Nino/La Nina events

Impacts of the 1997–98 and 2002–03 ENSOs on total number of flashes and number of flash days from the LIS (Lightning Imaging Sensor) on board the Tropical Rainfall Measuring Mission satellite and on the average flash rate from the combined OTD (Optical Transient Detector) / LIS data are studied in South/Southeast Asia (8° –30°N, 60°–120°E) for the period 1998–2005. Also examined is the difference between the geographical distributions of these parameters in the El Nino period in 1998 and in the corresponding normal period in 1999. During the 1997–98 ENSO event, the number of flashes and average flash rate increase by 12% and 36%, respectively, during the El Nino period and during the La Nina period decrease by 22% and 5%, respectively, as compared to the corresponding normal periods. Similarly, during the 2002–2003 ENSO event, the number of flashes and average flash rate increase by 28% and 5% during the El Nino period in 2002 as compared to the corresponding normal period. The contrast in lightning activity between the El Nino and La Nina periods is more pronounced in Southeast Asia than in South Asia because of the southeastward shift in the convection activity during the ENSO events. In both regions, however, monthly variations of both total number of flashes and average flash rate are almost parallel to that of surface temperature. Although, the inverse relationship between the Indian Summer Monsoon Rainfall (ISMR) and El Nino broke down in 1997–98, the relationship between the El Nino and lightning maintains its normal increasing trend, indicating that the lightning activity is more sensitive to the convective activity than to rainfall on seasonal time scale. The total number of flashes and aerosol loading increase in the break‐period regime as compared to the monsoonal regime. The number of flash days in both ENSO events is higher in the EL Nino phase and lower in the La Nina phase as compared to their normal values in the subsequent years. Enhancement of lightning activity is mostly concentrated over land areas. Our results show that although diurnal variations in lightning activity can be related to the variations in surface temperature, convective adjustment induced by the corresponding ENSO phase needs to be considered for explaining the lightning activity variations on these longer time scales.

Land–sea contrast in lightning activity over the sea and peninsular regions of South/Southeast Asia

The land–sea contrast in lightning activity between three sea regions of the Arabian sea (AS), the Bay of Bengal (BB) and the Chinese sea (CS) and two land regions of the Peninsular India (PI) and the Indo-China Peninsula (IP) has been studied from the 11‐year (1995 to 2005) data obtained from the Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) on board the Tropical Rainfall Measuring Mission (TRMM) satellite. Lightning activities in different sea regions and over different peninsular regions are also compared with each other. The values of flash rate over peninsular regions (PI and IP) are 2.6 to 33 times of those over sea regions (AS, BB, CS). Although this contrast is seen throughout the year it is more dominant in the premonsoon and postmonsoon seasons. Seasonal variations of the monthly-averaged values of the average flash rate are semiannual in all regions with one maximum in April/May and another in October. The two peaks in semiannual variations are attributed to the variation in surface air temperature. In addition, the October peak may have some contribution from the unstable thermodynamic conditions during the withdrawal phase of the summer monsoon. The annual flash rate shows an increasing trend of 1.1 to 1.2 times increase in both land and sea regions in South Asia but no significant change in the regions in Southeast Asia during the 1995–2005 period. The monthly-averaged flash rates are positively correlated with the average surface temperature and convective available potential energy (CAPE) and negatively correlated with the outgoing longwave radiation (OLR), with higher correlation coefficients over peninsular regions than over the sea regions. The flashes over peninsular regions, though more frequent, are likely to be less energetic and have only 0.4 to 0.9 of the radiance that is found over the sea regions. The lowest flash rate in the AS region can be attributed to the dominance of more maritime conditions with shallower clouds in monsoon season in this region.