LIS Science Team Meeting

(reported by Steven Goodman, steven.goodman@msfc.nasa.gov)

The LIS science team meeting was held at the Global Hydrology and Climate Center (GHCC) in Huntsville, Alabama on March 13-14, 1997. The primary objectives of the meeting were to review the status of the Lightning Imaging Sensor (LIS), discuss the status and results from the Optical Transient Detector (OTD) experiment (a LIS prototype in orbit since April 1995), review and update the LIS on-orbit calibration and validation plans, discuss the opportunities for participating in community field campaigns, review the opportunities for a geostationary lightning sensor, and conduct a "hands-on" demonstration to answer questions and provide a tutorial on the use and interpretation of OTD data and science products.

Hugh Christian (LIS PI) also reviewed the results from the lightning workshop held (immediately prior to the LIS meeting) on March 11-12 at Guntersville State Park, Alabama. The workshop was convened at the request of Robert Harriss, chief of the Mission To Planet Earth Science Division, to discuss the contribution of lightning studies to the science goals of MTPE and the U. S. Weather Research Program (USWRP). The results of this workshop were presented at NASA Headquarters to Dr. Harriss and other program managers in the science division on March 27.

Lightning Imaging Sensor Status

The LIS has been integrated on the Tropical Rainfall Measuring Mission (TRMM-1) satellite and the testing continues. The first end-to-end mission simulation was conducted successfully in November 1996. The launch minus 8 month (L-8) LIS production software delivery was made to the MSFC Distributed Active Archive Center (DAAC) in March 1997. This LIS software release will be used for the second TRMM End-to-End simulation scheduled for May.

A Memorandum of Agreement for LIS data delivery to the Japanese partners on TRMM has been completed. LIS data will be available to the science community monthly, once the data has been released from the quality assurance team. Near real-time, geolocated browse imagery will be available for download from the LIS web page on a daily basis. Special browse products will be provided to support field campaigns on request. This approach worked well in providing OTD imagery in support of the PEM (Pacific Exploratory Mission) Tropics chemistry mission. Daily OTD browse imagery and data are already being provided to Ken Pickering and Ann Thompson in support of the forthcoming (summer 1997) SASS (Subsonic Assessment) Ozone and Nitrogen Experiment (SONEX).

Optical Transient Detector Status

The OTD mission began in April 1995. The OTD, an early prototype of LIS, was flight qualified and launched as a scientific payload on the Microlab-1 satellite in a 70 degree inclination orbit at an altitude of 750 km. The OTD data have been quality assured, reprocessed, and released to the science community.

Some of the key scientific findings from the OTD mission are:

• Produced the most complete and detailed maps of the global lightning distribution ever assembled.
• The global flash rate is estimated to be 40 flashes per second, less than half of the widely accepted estimate of 100 flashes per second which dates back to 1925.
• Discovered lightning flash rate signature as possible aid in tornadic and hazardous storm warnings.
• Discovered potential lightning duration signature for continuing current discharges to ground, a key factor for the ignition of forest and wildland fires.

Two Ph.D. candidates supported by the LIS science team have recently graduated (Dennis Boccippio, MIT; Robert Solomon, U. Washington). Dr. Boccippio joined the LIS science team in Huntsville where he is analyzing the OTD data and performing on-orbit calibration and validation studies. Dr. Solomon is headed to France to collaborate on cloud electrification modeling studies.

Science Computing Facility

The LIS, OTD, and ancillary data previously archived at the MSFC DAAC (see related story in this issue of the Earth Observer) will continue to be available from the LIS SCF through the new Global Hydrology Resource Center (GHRC). The GHRC is collocated with the Global Hydrology and Climate Center (GHCC) in Huntsville, AL.

In addition to its current role in algorithm development, the LIS SCF will now operate as a PI-led solution for the data production, archive, and distribution system (formerly DAAC roles) for lightning data collected by the EOS lightning sensors, LIS and the OTD. Airborne and ground-based lightning calibration & validation data sets, as well as weather radar and SSM/I brightness temperatures (used by the LIS science team for convective storm identification and for algorithm development and validation) will continue to be available for distribution from the LIS SCF through the GHRC. All data sets will still be accessible through EOSDIS, since all data providers are interoperable with EOSDIS.

MTPE/USWRP Lightning Workshop

Hugh Christian reviewed the results from the MTPE/USWRP lightning workshop. The charge to the fourteen attendees was to discuss specific contributions of lightning observations and research to the MTPE and USWRP science goals, discuss science issues that lightning studies (space and ground based) can help address, describe their current research, describe the research that is enabled with the aid of a lightning sensor in geostationary orbit, and evaluate potential field campaigns to support LIS/OTD calibration and validation.

The attendees thought there was growing evidence that lightning is related to intense convection and the structure of the mixed phase region of clouds, perhaps serving as a proxy variable for updraft strength or as a updraft velocity threshold, rainfall regimes, and latent heating.

Scientists have observed a number of relationships between rainfall and lightning from tropical monsoon environments to extratropical continental environments. There is some evidence for interesting changes in the amount of rainfall per flash in different and changing environments. Steve Rutledge (CSU) proposed that rainfall per flash could serve as an index to define these different and changing environments. Such changes were observed in association with wave oscillations such as the Madden Julian Oscillation and in moving from moist tropical to arid environments.

Jim Dye (NCAR) reported on the strong interest within the atmospheric chemistry community for better understanding of the contribution of lightning as a major natural source (of uncertainty) of NOx. There is still a large uncertainty in the production rate per flash, the vertical distribution of the NOx produced by lightning, and the interannual variability. There is new interest in the effects that thunderstorms appear to be having on the chemistry of the tropopause and lower stratosphere.

Marcia Baker (U. Washington), John Latham (UMIST/NCAR), and Jim Weinman (GSFC) showed how lightning proxies for heating, water flux, and ice flux in clouds could be valuable as inputs to cloud and mesoscale models. Weinman showed an example of an MM5 mesoscale model run for the March 13, 1993 "Storm of the Century" in which the lightning observed over the data sparse (i.e., no radar coverage) Gulf of Mexico was merged with SSM/I and GOES-IR data to produce an improved heating rate in the model. The resulting data assimilation with the lightning data produced a better storm track and intensity forecast than was achieved using 12-hourly SSM/I and 3-hourly GOES data alone.

The group came up with a list of science issues and potential algorithms that might result from on-going lightning studies and enabled by a geostationary sensor as follows:

• Exploit appropriate lightning/rainfall correlations for heavy convective rain and flash flood events.
• Use the lightning to aid in the identification and separation of convective and stratiform precipitation areas.
• Use the lightning as gap-filling observations for improved and continuous sampling of storms in mountainous areas.
• Use lightning observations in combination with satellite and radar to describe the structure, variability, and life-cycle of mesoscale weather systems.
• Determine the nature of land vs. oceanic convection, and with respect to changing intensity of tropical storms.
• Characterize winter storms with and without lightning to improve understanding of the nature of embedded convection in snow storms.
• Improved forest and wildland fire predictability and understanding by exploiting the flash duration and amplitude as indicators of the continuing currents that ignite fires.
• Improved interpretations of storm structure, morphology, and hazardous weather from observing storms with extreme intracloud flash rates, and storms with and without ground discharges.

The observing strategy recommendations from this group are to continue the OTD observations into the TRMM time frame. These data continue to be valuable since these are the only observations of boreal forests in the northern hemisphere. During the LIS mission, efforts should include supporting the TRMM calibration and validation field campaigns, supporting the NASA chemistry field campaigns not part of TRMM, explore the lightning "proxy variable" concept with the combined TRMM sensors and ground based systems, and reach out to the modeling community to test the proxy concepts using merged data sources and model assimilation. The development of the geostationary concepts should be continued and the applicability of the data assessed. The Lightning Mapper Sensor pilot study taking place in collaboration with Lincoln Labs at the NWS office in Melbourne, FL addresses some of these proxy variable issues. Steve Goodman summarized the initial results from this project during the LIS meeting. As a community we need to refine and validate the proposed proxies for storm hazards, NOx production, and cloud variables.

Field Campaigns

The team reviewed current plans and opportunities for participating in field experiments during the TRMM-1 mission. Otto Thiele presented the status and plans for TRMM ground validation. Ed Zipser reported on the plans for airplane measurements during TRMM. Rich Blakeslee summarized the LIS calibration/validation plans. There are four primary campaign sites for focused LIS on-orbit calibration and algorithm validation:

• TExas-FLorida Gulf Coast UNderflight experiment (TEFLUN), Spring 1998
• Brazil-Rondonia during LBA, January-February 1999
• Kwajalein, Summer 1999
• Darwin, On-going since November 1995

The TEFLUN experiment would extend the area of observations currently under study by the LIS team. A comprehensive set of WSR88D radar and lightning observations are now being made in central Florida at the TRMM ground truth site in the environs of Kennedy Space Center. The LIS science team is developing a Memorandum of Agreement with Brazilian scientists to deploy and operate a small lightning network in Rondonia during the TRMM mission. It is hoped that measurements can begin by January, 1998 and thus provide some early understanding of the characteristics of thunderstorms in that region. This operation would be similar to the on-going LIS measurement program at Darwin, Australia.

Zen Kawasaki (Osaka University) discussed his results from recent field experiments and his role on the Japanese TRMM science team. He will continue collecting lightning data in Japan during the TRMM-1 project and will continue collaborating in the LIS/OTD on-orbit calibration and algorithm validation.

At Kwajalein atoll, Aeromet has been responsible for a local area lightning ground strike network. During TRMM, we are examining the possibility of upgrading the magnetic direction finder technology at Kwajalein to time of arrival technology and possibly expanding the area of coverage. During the Brazil and Kwajalein experiments in 1999, we also plan on deploying a system to map total lightning activity within the clouds. The latter system is under development by Paul Krehbiel at New Mexico Tech. Brazil and Kwajalein combined would produce the most detailed lightning observations of tropical land and oceanic storms to date.

The next LIS Science Team Meeting is planned for March 1998.