|
|
NAMMA LIDAR Atmospheric Sensing Experiment (LASE) Table of Contents
NASA's Lidar Atmospheric Sensing Experiment (LASE) system was operated during the the NASA African Monsoon Multidisciplinary Analyses (NAMMA) campaign to gather water vapor mixing ratio and aerosol scattering ratio (815 nm) profiles. Other derived parameters include: relative humidity, equivalent potential temperature, virtual potential temperature, precipitable water vapor profiles, aerosol backscatter, aerosol extinction, and aerosol optical thickness profiles (815 nm). Aerosol data are reported as Atmospheric Scattering Ratios on a logarithmic scale. Water Vapor data are reported as mixing ratios (g/kg) on both a Linear and logarithmic scale. LASE was operated from the NASA DC-8 aircraft during 14 NAMMA campaign flights between August 15 and September 12, 2006. CampaignThese data files were generated during support of the NASA African Monsoon Multidisciplinary Analyses (NAMMA) campaign, a field research investigation sponsored by the Science Mission Directorate of the National Aeronautics and Space Administration (NASA). This mission was based in the Cape Verde Islands, 350 miles off the coast of Senegal in west Africa. Commencing in August 2006, NASA scientists employed surface observation networks and aircraft to characterize the evolution and structure of African Easterly Waves (AEWs) and Mesoscale Convective Systems over continental western Africa, and their associated impacts on regional water and energy budgets. For more information about the NAMMA Campaign, go to the NAMMA web site: http://namma.nsstc.nasa.gov/ Principles of OperationNASA's Lidar Atmospheric Sensing Experiment (LASE) system is an airborne DIAL (Differential Absorption Lidar) system used to measure water vapor, aerosols, and clouds throughout the troposphere. LASE probes the atmosphere using lasers to transmit light in the 815-nm absorption band of water vapor. Pulses of laser light are fired vertically below the aircraft. A small fraction of the transmitted laser light is reflected from the atmosphere back to the aircraft and collected with a telescope receiver. The received light indicates the amount of water vapor along the path of the laser beam. The LASE program was initiated as an effort to produce an autonomous system for measuring water vapor levels from airborne and spaceborne platforms using LIDAR technology. For much more in-depth information about the LASE system, visit this web location: http://asd-www.larc.nasa.gov/lase/ASDlase.html Data Naming ConventionData are in files of the form:
Image files are of the form:
where, Data File Specifics There are two types of data files included in this dataset, and the specifics for each file are listed below. DC-8 Relative Aerosol Scattering Vertical data resolution and reporting interval is 30 m. The horizontal data reporting interval is 6 seconds (1.4 km) with horizontal averaging of 3 seconds (0.7 km). This relative aerosol measurement represents the total backscattering of aerosols and molecules divided by a molecular density profile, which was determined using a tropical molecular density profile derived from the Standard Atmosphere. The nadir and zenith measurements have been normalized to each other and combined. No corrections for molecular, water vapor or aerosol attenuation have been performed in this preliminary analysis. This file conforms to the Gaines/Hipskind "2310" format for multi-dimensional data sets. DC-8 Water Vapor Mixing Ratio (Nadir) Vertical data resolution is 330 m with a reporting interval of 30 m. The horizontal data averaging interval is 2 minutes (~28 km) with a sub-sampling (reporting) interval of 6 seconds (1.4 km). LASE measures water vapor density which is converted to water vapor mixing ratio by dividing by a molecular density profile. This analysis uses molecular density profiles from the AFGL Standard Atmosphere mid-latitude summer model for flights 1 - 9 and the tropical model for flights 10 - 16. This file conforms to the Gaines/Hipskind "2310" format for multi-dimensional data sets. The format requires stop, mid and end times for the averaging intervals without overlap. Therefore, only the mid time of the 2 minute averages is accurate. Data FormatThe LASE_NAMMA data files are stored in ASCII using Gaines-Hipskind Data Archive Format. Format specification for Data Exchange by Steve E. Gaines and R. Stephen Hipskind may be found in PDF form here: Gaines_Hipskind.pdf (The LASE data use data record format number 2310). These data can be read using the sample read software supplied below. Read SoftwareThere is a sample read program provided which works with all Gaines-Hipskind formatted LASE data sets. It is written in ANSI C, and has been successfully tested on Sun, SGI, HP, and DEC computer operating systems. This program was written as an example of how to read in the LASE data. It reads in and writes out to the screen the file header information followed by each profile's header and data. This sample program can be downloaded here: read_lase_gh.c Currently the input file name is expected to be no more than 50 characters in length. If you have changed the name of the input file to greater than 50 characters, you will need to modify this program, changing the value of the MAX_FILENAME parameter in the #define statement near the beginning of the file to be at least the maximum length needed + 1. All data files are assumed to be in the current working directory. If the files are located in another directory be sure to include the complete path with the file name. Contact InformationThe data producer is:
To order these data or for further information, please contact:
|