The GLM will provide unprecedented observations on thunderstorm evolution over most of the Americas and adjoining oceans. For the first time from high earth orbit, information will be provided from deep within the heart of thunderclouds, not from just their upper layer. The GLMS will provide continuous measurements of lightning and ice-phase precipitation. These measurements will be used to: 1. Diagnose and forecast the transient evolution of severe storm events, such as tornadoes, microbursts, hail storms and flash floods.

2. Improve mesoscale model forecasts and satellite-based retrievals of convective properties.

3. Improve forecast models through rapid-update assimilation of lightning data.

4. Examine the seasonal to inter-annual variability of storms.

For operations and applications, the GLM will contribute to:

· Predicting the onset of microbursts, hail and tornadoes. · Tracking thunderstorms and providing warnings of approaching lightning threats. · Improving airline routing around thunderstorms, improving safety, saving fuel and reducing delays. · Providing real-time weather data, improving efficiency of emergency management. · Locating lightning strikes known to cause forest fires and reducing response times · Assessing the role of thunderstorms and deep convection in global climate · Providing a new data source to improve air quality / chemistry forecasts

Using the present conceptual design, the GLM should be able to detect over 90% of the total lightning that occurs within its field of view during the day and night. It will be able to geolocate each lightning to a specific cell with timing resolution of two milliseconds. It will sample each location within its field of view continuously and distribute the lightning data in near real-time with less than one minute latency.

This presentation will discuss the physical characteristics of a conceptual GLM, describe the anticipated performance capabilities and address some of the scientific and operational capabilities that could be realized with a GLM. In addition, results from two low earth orbiting lightning sensors that use similar technology will be presented.