Lightning
Data Limitations
Historically, most lightning data have been proprietary; therefore, climatological records of the hazard are limited. However, a new NOAA satellite became operational in late 2017 and contains a significant technological advancement called the Geostationary Lightning Mapper (GLM). The GLM can detect the presence of total lightning including in-cloud, cloud-to-cloud, and cloud-to-ground. While this advancement will not provide historical lightning data, it will add to the climatological record as time goes on.
Definition and Description
A visible electrical discharge produced by a thunderstorm. The discharge may occur within or between clouds, between the cloud and air, between a cloud and the ground or between the ground and a cloud (NWS 2009).
Lightning forms from charge separation within thunderstorms, usually cumulonimbus clouds. Lightning is essentially a large spark of static electricity, similar to touching a doorknob on a dry day (although much more powerful). Most lightning forms from streamers that work their way down from the charge centers of clouds toward the ground. When it gets close to the ground, a return stroke is initiated, which we see as a flash of light. Thunder is created by a shock wave from rapid heating of the air to 18,000 degrees – hotter than the surface of the sun.
Lightning is capable of striking as far as 10 miles away from a storm. Distance can be estimated by counting the seconds between the flash and the sound of thunder. It takes 5 seconds for the shockwave to travel one mile. Lightning severity is not rated, although new detection systems allow accurate identification of lightning strikes allowing analysis of lightning frequency.
Historical Data
Lightning Climatology Tool
(1995-2019) NOAA/National Weather Service Storm Prediction CenterThis tool provides a daily and hourly lightning climatology, showing the probability of at least one cloud-to-ground (CG) lightning strike occurring each day of the year or each 1-hour or 4-hour period throughout the day. It can be used to assess the time of day and time of year with the highest probability of CG lightning.
1. Zoom in to your area of interest on the map. 2. The default map shows the daily (24-Hour) lightning probability on January 1, as indicated in the map title. To select a 1-Hour or 4-Hour climatology, hover your mouse over the Lightning tab at the top of the page and select 1-Hour or 4-Hour. To view other days or hours, move the horizontal scroll bar under the map. Note: the map title and scroll bar show hours in UTC format. 3. Click your area of interest on the map to view the probability of CG lightning occurring on that day or hour for that area. 4. Click the Time Series button within the pop-up box to view a graph of average CG lightning probability for your selected daily/hourly option. You can use this graph for a quick assessment of the time of year/day that location experiences the most CG lightning. Hover your mouse over the graph for details. Note for hourly options: the box shows local time, unlike the map title. The 4-hour graph will show the probability of at least one CG lightning strike occurring within a 4-hour window (e.g., the value for 12pm will show the probability of lightning occurring between 8am-12pm). 5. If you selected the 1-hour or 4-hour option, click the Heat Map button within the pop-up box to view a graph of 1-hour or 4-hour lightning climatology by both day of year (horizontal axis) and time of day (vertical axis). Darker colors represent a higher probability. Hover your mouse over the graph to assess what time of year and day that lightning is more likely to occur in your area.
Annual and Monthly Distributions of Cloud-to-Ground Lightning
(1996-2016)NOAA National Severe Storms Laboratory/ Cooperative Mesoscale Meteorological StudiesThese static maps show the cloud to ground lightning density (strikes per km2) over Oklahoma, averaged over the years 1996-2016. There are five maps on the website that display annual and seasonal (winter, spring, summer, and fall) densities.
1. Click on the link to access the Oklahoma Climatological Survey’s Tornadoes & Severe Storms climatology page. 2. Select lightning map(s) of choice from the following: Yearly Lighting Density, Winter Lightning Density, Spring Lighting Density, Summer Lightning Density, Fall Lightning Density. 3. Analyze your lightning frequency based on county lines.
Vaisala Annual Lightning Report
(Varies by year of report) VaisalaThis static report has been updated annually since 2017 and includes maps of average cloud-to-ground flash density and total lightning density for the previous 5-10 years in the U.S. It offers high-resolution local and county-level maps and information.
1. Click on the link to access Vaisala’s homepage. 2. In the search bar at the top of the page, type annual lightning report then click the button. 3. In the list of search results, scroll to find the most recent lightning report, such as Annual Lightning Report 2020. 4. Select your desired report and click the title to download the PDF. Scroll down the document to view U.S. Cloud-to-Ground Flash Density Maps in high resolution and aggregated by county.
Climate Change Trends
Lightning is associated with thunderstorms, so as more favorable environments for thunderstorms are expected across the United States, increases in lightning are also projected. Studies have shown an increase in lightning associated with severe storms (Schultz et al. 2011). Climate models project an increase in the frequency and intensity of severe thunderstorms (Kossin et al. 2017), therefore, lightning occurrences are likely to increase. Confidence in the projections is currently low, however, due to the isolated and sporadic nature of lightning events and limited comprehensive datasets which make it difficult to track long-term trends (Wuebbles et al. 2017a).