One of the goals of LIDAR scientists is to obtain long term monitoring of water vapor using Raman LIDAR [1]. Previous LIDAR research suggests that the measurement of water vapor can be improved by better analysis of the LIDAR system's calibration factor. Currently LIDAR scientists generally use radiosonde data to calibrate LIDAR data. We are using a standard lamp calibration technique to calibrate the LIDAR data to compare with the radiosonde technique in efforts to independently calibrate the LIDAR system. The lamp calibration technique we implement here involves two motion controllers scanning a halogen lamp over the aperture of a LIDAR telescope. When we compared the calibration factor of the lamp mapping technique to the radiosonde technique we found that they agreed within 5%. Using this method, we have determined a calibration of a Raman LIDAR system with accuracy in the range of 5% [2]. Future work involves obtaining temperature measurements directly from the HURL system to improve water vapor measurements. We plan to obtain the temperature directly from the LIDAR system by extracting rotational Raman cross sections using two narrow band-pass filters and taking the ratio of the two measurements. Using the lamp calibration and the temperature measurements found directly from the LIDAR we can calculate a water vapor mixing ratio that is less dependent on radiosonde data [3].

Abstract Water vapor mixing ratio retrieval using the Howard University Raman lidar is presented with emphasis on three aspects: (i) comparison of the lidar with collocated radiosondes and Raman lidar, (ii) investigation of the relationship between atmospheric state variables and the relative performance of the lidar and sonde (in particular, their poor agreement), and (iii) comparison with satellite-based measurements. The measurements were acquired during the Water Vapor Validation Experiment Sondes/Satellites 2006 campaign. Ensemble averaging of water vapor mixing ratio data from 10 nighttime comparisons with Vaisala RS92 radiosondes shows, on average, an agreement within ±10%, up to ∼8 km. A similar analysis of lidar-to-lidar data of over 700 profiles revealed an agreement to within 20% over the first 7 km (10% below 4 km). A grid analysis, defined in the temperature–relative humidity space, was developed to characterize the lidar–radiosonde agreement and quantitatively localizes regions of strong and...

We show here new results of a Raman LIDAR calibration methodology effort putting emphasis in the assessment of the cross-section ratio between water vapor and nitrogen by the use of a calibrated NIST traceable tungsten lamp. Therein we give a step by step procedure of how to employ such equipment by means of a mapping/scanning procedure over the receiving optics of a water vapor Raman LIDAR. This methodology has been independently used at Howard University Raman LIDAR and at IPEN Raman LIDAR what strongly supports its reproducibility and points towards an independently calibration methodology to be carried on within an experiment routine.

The Measurements of Humidity in the Atmosphere and Validation Experiments (MOHAVE, MOHAVE-II) inter-comparison campaigns took place at the Jet Propulsion Laboratory (JPL) Table Mountain Facility (TMF, 34.5ºN) in October 2006 and 2007 respectively. Both campaigns aimed at evaluating the capability of three Raman lidars for the measurement of water vapor in the upper troposphere and lower stratosphere (UT/LS). During each campaign, more than 200 hours of lidar measurements were compared to balloon borne measurements obtained from 10 Cryogenic Frost-point Hygrometer (CFH) flights and over 50 Vaisala RS92 radiosonde flights. During MOHAVE, fluorescence in all three lidar receivers was identified, causing a significant wet bias above 10-12 km in the lidar profiles as compared to the CFH. All three lidars were reconfigured after MOHAVE, and no such bias was observed during the MOHAVE-II campaign. The lidar profiles agreed very well with the CFH up to 13-17 km altitude, where the lidar measurements become noise limited. The results from MOHAVE-II have shown that the water vapor Raman lidar will be an appropriate technique for the long-term monitoring of water vapor in the UT/LS given a slight increase in its power- aperture, as well as careful calibration.

The Measurements of Humidity in the Atmosphere and Validation Experiments (MOHAVE, MOHAVE-II) inter-comparison campaigns took place at the Jet Propulsion Laboratory (JPL) Table Mountain Facility (TMF, 34.5(sup o)N) in October 2006 and 2007 respectively. Both campaigns aimed at evaluating the capability of three Raman lidars for the measurement of water vapor in the upper troposphere and lower stratosphere (UT/LS). During each campaign, more than 200 hours of lidar measurements were compared to balloon borne measurements obtained from 10 Cryogenic Frost-point Hygrometer (CFH) flights and over 50 Vaisala RS92 radiosonde flights. During MOHAVE, fluorescence in all three lidar receivers was identified, causing a significant wet bias above 10-12 km in the lidar profiles as compared to the CFH. All three lidars were reconfigured after MOHAVE, and no such bias was observed during the MOHAVE-II campaign. The lidar profiles agreed very well with the CFH up to 13-17 km altitude, where the lidar measurements become noise limited. The results from MOHAVE-II have shown that the water vapor Raman lidar will be an appropriate technique for the long-term monitoring of water vapor in the UT/LS given a slight increase in its power-aperture, as well as careful calibration.

Three NASA-funded field campaigns have been hosted at the Howard University Research Campus in Beltsville, MD. In each of the years 2006, 2007 and 2008, WAVES field campaigns have coordinated ozonesonde launches, lidar operations and other measurements with A-train satellite overpasses for the purposes of satellite validation. The unique mix of measurement systems, physical location and the interagency, international group of researchers and students has permitted other objectives, such as mesoscale meteorological studies, to be addressed as well. We review the goals and accomplishments of the three WAVES missions with the emphasis on the nonsatellite validation component of WAVES, as the satellite validation activities have been reported elsewhere.

The collision broadenings of the Na D lines were calculated from the transmission measurements of the vapor in sub-μTorr and μTorr regions by modeling the line shape with the Voigt profile. From the line shift, the average time between collisions is calculated. The ratio of the width to the shift is of the order of 10−4 implying that the impact approximation is valid. Expanding the line widths and shifts in powers of the product of number density and mean velocity of the atoms, the radiative transition probabilities, and the fundamental line shape constants: collision cross-sections and asymmetry of the lines are obtained. Moreover, from the line shifts and using the estimated value of the optical collision diameter obtained from the line widths, the average C3 value, over the temperature ranges the experiment covers, is calculated.

The number density and vapor pressure of atomic sodium were measured with optical method using the transmittance at the resonance of the Na D doublet transitions in the temperature range 337–511K. In these temperature ranges the calculated number densities, from the transmittance measurements, vary from 1.8×109 to 1.8×1011cm−3. The corresponding vapor pressure of the sodium ranges from 5.7×10−8 to 8.6×10−6Torr. The value of the collision broadenings that gave these results are in the range 0.045–0.38 of the Doppler width for the 3S1/2−3P1/2 resonance transition while it varies from 0.03 to 1.2 for the 3S1/2−3P3/2 transition.