NASA’s Goddard Space Flight Center (GSFC) transported two lidar instruments to the NOAA facility at the Mauna Loa Observatory (MLO) on the Big Island of Hawaii, to participate in an official, extended validation campaign. This site is situated 11,141 ft. above sea level on the side of the mountain. The observatory has been making atmospheric measurements regularly since the 1950’s, and has hosted the GSFC Stratospheric Ozone (STROZ) Lidar and the GSFC Aerosol and Temperature (AT) Lidar on several occasions, most recently between November, 2012 and November, 2015. The purpose of this extended deployment was to participate in Network for the Detection of Atmospheric Composition Change (NDACC) Validation campaigns with the JPL Stratospheric Ozone Lidar and the NOAA Temperature, Aerosol and Water Vapor instruments as part of the routine NDACC Validation Protocol.
Jet Propulsion Laboratory currently operates lidar systems at Table Mountain Facility (TMF), California (34.4°N, 117.7°W at 2300m) and Mauna Loa Observatory (MLO), Hawaii (19.5°N, 155.6°W at 3400m) under the Network for the Detection of Atmospheric Composition Change (NDACC, formerly NDSC). To complement existing NDACC lidars at TMF, which acts as a primary site for inter-comparisons, a new water vapor and temperature lidar has begun routine operation with typically 3-4 nightly profiles per week. As water vapor is a key greenhouse gas, and is highly variable on annual and seasonal cycles, accurate long term measurements are necessary for predictions of climate change and to increase our understanding of the atmospheric processes it contributes to. The new TMF lidar has demonstrated high spatial and temporal resolution, with a high degree of optimization being achieved over the past year, although the authors believe further improvement may yet be possible. The lidar has been designed for accuracies of 5% up to 12km in the free troposphere with the capability to measure to the tropopause and lower stratosphere with accuracies of 1 ppm. It is anticipated that the data sets produced will be used for Aura validation and for incorporation into NDACC archives. Validation results for the optimized system are presented with intercomparisons using Vaisala RS92-K radiosondes.
The rationale and justification for aerosol and cirrus cloud observations in the equatorial region of the central Pacific are presented. The development of a small, fully automatic lidar system, powered by wind and solar energy, is discussed.
The tidal signature in the middle atmospheric thermal structure (15 - 95 km) at Mauna Loa, Hawaii, (19.5 degrees N) is investigated using more than 145 hours of nighttime lidar measurements obtained during October 3 - 16, 1996 and October 2 - 11, 1997. The daytime HRDI temperatures taken in September and October 1993 - 1997 and zonally averaged at the same latitude are also used. The nighttime lidar and daytime HRDI temperature evolution and tidal signatures are compared to the predictions of the GSWM tidal model. Agreement is found between lidar and GSWM below 60 km, and between HRDI and GSWM above 85 km. Some significant disagreement is found between 60 and 80 km altitude. In particular, a strong semidiurnal signature is observed by lidar and not predicted by GSWM. It appears that the tidal structure observed by lidar is more representative of that predicted by GSWM at 24 degrees N, suggesting a latitudinal shift between theory and observation. It is not clear whether this shift is related to an indetermination of the tidal source and/or propagation or if the observed differences are simply due to local/regional Local-Solar-Time-related oscillations obscuring the tidal signature.
Results from new observations of mesospheric temperature inversion layers using long-term lidar measurements at mid- and low-latitudes are presented. Observations of inversions above Table Mountain, California, (34.4 degrees N) and Mauna Loa, Hawaii, (19.5 degrees N) are in very good agreement with previous lidar and satellite observations. At least two distinct types of events have been observed. The winter inversions occur near 70 km altitude at midlatitudes in December-January and about 1 - 2 months laster at subtropical latitudes. The tidal signature in the middle atmospheric thermal structure has been investigated using more than 140 hours of nighttime lidar measurements at TMF during January 1997 and February 1998. The temperature profiles (30 - 85 km) revealed the presence of persistent mesospheric inversions around 65 - 70 km altitude with a clear Local-Solar-Time (LST) dependence. Also, some higher altitude inversions (80 - 85 km) have been observed at lower latitudes around the equinoxes and 1 - 2 months later at mid-latitudes. In particular the temperature minimum systematically observed at the altitude of approximately 80 km and propagating downward throughout the night might also suggest the important role played by the tides.
We describe improvements to two lidar systems for measurements of ozone and aerosols in the troposphere and lower stratosphere. These changes are primarily related to the receiver optical sub-systems and the principal topics presented are the telescopes, the ozone DIAL receiver, and the aerosol lidar receiver. The data acquisition systems were also replaced. The goals of these modifications were to increase the spatial and temporal resolution of the lidars, to extend the altitude range covered, and to improve the quality of the raw data.
Long term measurements from several lidar instruments, located at 44.0 degrees N, 40.6 degrees N, 34.4 degrees N, and 19.5 degrees N, were used to develop a new climatology of the middle atmosphere temperature. For each instrument, the measurements on every day of the year over the entire record were averaged to build a composite year of temperature profiles. The lidar climatologies were compared to the CIRA-86 model which appears to be systematically too cold between 90 and 95 km, by greater than or equal to 20 K, and possibly 6 - 8 K too warm around 80 km, making its use as a reference questionable at these altitudes. The annual and semi-annual components of the seasonal variability and the 2- to 33-day period variability were also investigated. An annual cycle with 6 - 7 K amplitude in the upper stratosphere, increasing to 15 - 20 K at 80 km, is observed at mid-latitudes. At lower latitudes, a semiannual oscillation (SAO) propagates downward from 85 to 30 km and is characterized by a stronger first cycle than the second (4 K and 2 K amplitude). The 2- to 33- day variability at mid-latitudes shows a maximum during winter around 40 km and in the mesosphere. Finally, sudden seasonal transitions, highly consistent between all instruments, have been observed, in particular in the early winter mid-latitudes with a two-step warming of the mesosphere between 65 and 85 km.
Results from dual wavelength Raman lidar observations of tropical high-altitude cirrus clouds are reported. Based on 107 hours of night-time measurements cirrus clouds were present in more than 50% of the observations at latitudes between 23.5 degrees south and 23.5 degrees north and altitudes between 11 and 16 km. Volume depolarization is found to be a sensitive parameter for the detection of subvisible cloud layers. Using Mie scattering calculations estimates of the ice water content are derived.
Attention is given to a ground-based differential absorption lidar system developed and operated at the JPL Table Mountain Facility for measurements of stratospheric ozone concentration profiles from approximately 15 to 20 km altitude. The seasonal variations observed between February 1988 and late 1990 are presented as a function of altitude. For the summer 1989 Stratospheric Ozone Intercomparison Campaign, the lidar measurements were found to agree with the average of the results obtained from seven different instruments over a 14-d period to within 5 percent over the altitude range 18 to 49 km. The status of this instrument is discussed, with emphasis on areas of improvement over the present system.
A lidar facility has been established at the Jet Propulsion Laboratory- Table Mountain Facility located at an altitude of 2300 m in the San Gabriel Mountains in Southern California. This facility is using the technique of differential absorption lidar to measure atmospheric ozone concentration profiles. Two separate systems are needed to obtain the profile from the ground up to an altitude of 45 to 50 km. A Nd:YAG-based system is described for measurements from the ground up to 1 5 to 20 km altitude, and an excimer-laser-based system for measurements from 15 km
to 45 to 50 km altitude. The systems were designed to make high-precision, long-term measurements to aid in the detection of changes in the atmospheric ozone abundance through participation in the Network of Detection of Stratospheric Change.
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