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ALVICE
 
 

Table Mountain facility (California)

The NASA Jet Propulsion Laboratory (JPL) Table Mountain Facility (TMF) is a unique, remote scientific and engineering facility that provides an ideal location for many research projects, including astronomy, lidar, and projects for universities. TMF's remote location, altitude, climate, and lack of light contamination in the dark sky historically makes it one of the best places in the USA for cloudless night time skies, essential for atmospheric remote sensing.
The JPL atmospheric lidar group has been designing, buliding and operating for over two decades several lidar instruments dedicated to the long term monitoring of atmospheric composition and satellite validation. The long-term high quality measurements from these lidars contribute to our understanding of our changing planet, in particular processes governing stratospheric ozone depletion and climate change.

Table Mountain Facility

Stratospheric ozone DIAL
A Differential Absorption Lidar (DIAL) has been routinely measuring stratospheric ozone (15-50 km), middle atmospheric temperature (25-90 km), and stratospheric aerosols (15-40 km) from TMF since 1988. The instrument acquired over 3000 ozone and temperature profiles. It has undergone two major upgrades in 1994 and 2001. The current system combines Rayleigh/Mie and nitrogen vibrational Raman scattering techniques, and includes 8 receiving channels (4 channels operating at the ozone-absorbed wavelengths of 308 nm and 332 nm, and 4 channels at the non-absorbed wavelengths of 355 nm and 387 nm). The combination of its channels allows ozone retrievals between 12 km and 50 km altitude, temperature retrieval between 12 km and 90 km, and aerosol backscatter ratio between 12 km and 40 km.
Instrument/dataset quick facts:
- Instrumental vertical resolution: 300 m
- Vertical range: ozone=[12,50] km; temperature=[25,90] km; aerosols=[12,40] km
- Typical temporal resolution: From 5 min to 2 hours
- Typical measurement frequency: 3-5 times per week, nighttime only
- Occasional "all-night" measurements for special studies
- Typical total number of measurements per year: 200

Tropospheric ozone DIAL
A tropospheric ozone lidar (4-25 km) also located at TMF has been operating since 1999. This DIAL system was designed in the early 1990s for the measurements of tropospheric ozone and aerosols. It was reconfigured and optimized in 1998 for tropospheric ozone exclusively. Routine data acquisition started in 1999 and the instrument has since measured over 2000 tropospheric ozone profiles. The system uses the Rayleigh/Mie scattering technique, and includes 4 receiving channels (2 channels operating at the ozone-absorbed wavelength of 289 nm and 2 channels at the weakly-absorbed wavelength of 299 nm). The tropospheric ozone DIAL pair 289/299 nm allows ozone retrievals between the altitudes of 4 km and 20 km. To extend the vertical range, the signal received from either the 308 or 355 nm (low-range) channel of the co-located stratospheric DIAL is used with the (upper range) 299 nm of the tropospheric ozone system to form a hybrid DIAL pair allowing ozone to be retrieve in the lower stratosphere (12-27 km).
Instrument/dataset quick facts:
- Instrumental vertical resolution: 75 m
- Vertical range: ozone=[4,25] km
- Typical temporal resolution: From 5-min to 2-hours
- Typical measurement frequency: 3-5 times per week, nighttime only
- Occasional "all-night" measurements for special studies
- Typical total number of measurements per year: 200

Water vapour Raman Lidar
This Raman lidar, dedicated to the measurement of upper tropospheric water vapour, was first built in 2003. It was redesigned in 2005 and 2007 in order to optimize its detection capability in the Upper Troposphere/Lower Stratosphere (~5 ppmv). Routine data acquisition started in 2005 and the instrument has since measured over 500 tropospheric water vapour profiles. The system uses the vibrational Raman scattering of the nitrogen and water vapour molecules and includes 9 receiving channels (3 Rayleigh channels at 355 nm dedicated to temperature and aerosol measurements, 3 "nitrogen" channels at 387 nm, and 3 "water vapour" channels at 407 nm). After a few signal corrections, the ratio of the lidar signals at 407 nm and 387 nm is proportional to water vapour mixing ratio. The measurements are calibrated using a calibration lamp and routine RS92 radiosonde measurements. The combination of the various channels allows water vapour retrieval from 3.5 km to 15 km.
Instrument/dataset characteristics:
- Instrumental vertical resolution: 75 m
- Vertical range: water vapour=[3.5,15] km
- Instrument temporal resolution: Typically from 5-min to 2-hours
- Typical measurement frequency: 3-5 times per week, nighttime only
- Occasional "all-night" measurements for special studies
- Typical total number of measurements per year: 200.

Addtional measurements in support of the NDACC lidars and related project
In support of the TMF water vapour Raman lidar program, a radiosonde launch program started in November 2004. Vaisala RS92 PTU radiosondes are launched from the lidar site every night when the lidar operates, i.e., four to five times per week. Humidity measurements are made using two Humicap thin-film capacitive sensors alternately heated until ambient temperature falls below -65ºC. When using smaller (200 g) balloons, the radiosonde provides temperature measurements from the ground to around 20 km, and relative humidity measurements up to about 12-15 km. When using larger balloons (500 g), the radiosonde provides temperature measurements up to around 30 km.In support of EOS-Aura satellite MLS and TES ozone validation, and as part of the IONS-06 ozonesonde network, ozonesondes were provided to JPL by NOAA, for launch from the TMF. The program started in March 2006 and more than 60 launches were made in 2006/2007. The ECC ozonesonde is interfaced with a Vaisala RS80 PTU sonde to transmit the data to the ground system.

More information can be found at the JPL Lidar Group Website

 
 
 
 
         
                                                               

19 September 2016