Lightning observations with Los Alamos sferic arrays (LASA) in Florida and the Great Plains

Since 1998, Los Alamos National Laboratory (LANL) has deployed an array of fast electric field change sensors (LASA) in New Mexico and Florida in support of LANL's satellite lightning observations. In the spring of 2004, all sensors were significantly upgraded with new electronics and data acquisition systems, and two new arrays have since been deployed. In April, 2004, an eight-station array was deployed in north-central Florida, and in April, 2005, a six-station array was deployed in the Great Plains. The Florida stations (FLN) form a relative dense array with six of them situated within an area of ~100 km diameter, whereas the Great Plains stations (GPN) form a much larger array of ~1000 km diameter and the stations are situated at Los Alamos, NM, Greenley, CO, Lincoln, NE, Norman, OK, Lubbock, TX, and Garden City, KA. All stations are connected to the local internet, and the operation, data retrieval, and software upgrade are done through the internet from Los Alamos.

To support LANL's satellite programs, LASA is configured to indiscriminately detect all field change signals produced by lightning and to capture and archive all raw waveforms. Therefore, LASA is capable of total lightning (IC and CG) detection and characterization. Each station is time-tagged with a GPS receiver, and the lightning events are geolocated by using a differential time of arrival (TOA) technique. Owe to the dense station arrangement, FLN is able to produce three dimensional (3-D) lightning locations for storms over or near the array, in addition to its long-range 2-D capability. GPN predominately produce 2-D locations except for some temporally isolated IC events for which the ionospheric reflection can be used to determine the heights of the sources.

This paper describes the operations of the new LASA arrays and reports the first one year and a half of lightning observations. We present the analysis of the array's location accuracy, minimum detectable peak current, and ratio of intracloud to cloud-to-ground flashes. Some case studies that illustrate the storm evolution, lightning classification, radar comparison, and therefore, the potential meteorological application are discussed.