http://hdl.handle.net/2122/86 2013-05-21T07:22:09Z http://hdl.handle.net/2122/7943 Title: Strato-mesospheric ozone measurements using ground-based millimeter-wave spectroscopy at Thule, Greenland Authors: Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cesaroni, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Fiorucci, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Smith, A. K.; Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA; Froidevaux, L.; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA; Mlynczak, M. G.; NASA Langley Research Center, Hampton, Virginia, USA Abstract: On January 2009 a ground-based millimeter-wave spectrometer (GBMS) was installed at Thule Air Base (76.5ºN, 68.8ºW), Greenland, for long-term winter monitoring of several stratospheric and mesospheric trace gases in the framework of the Network for the Detection of Atmospheric Composition Change. This work is aimed at characterizing the GBMS O3 vertical profiles between 35 and 80 km altitude obtained by applying the optimal estimation method to O3 pressure-broadened spectral line measurements carried out during three winters. In this altitude range, GBMS O3 retrievals are highly sensitive to variations of the atmospheric state, and their accuracy is estimated to be the larger of 11% or 0.2 ppmv. Comparisons of GBMS O3 profiles with colocated satellite-based measurements from Aura Microwave Limb Sounder (MLS) and Thermosphere Ionosphere Mesosphere Energetics and Dynamics Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) show a good agreement below 65 km altitude once the known 10%–20% high bias of SABER O3 profiles is considered, with the GBMS displaying an averaged low bias of 9% and 17% with respect to MLS and SABER. In the nighttime mesosphere, the GBMS detects the ozone tertiary maximum within 0.1 ppmv (6%) on average with respect to the convolved MLS, SABER, and global 3-D ROSE model profiles but shifts its position to lower altitudes by 4–5 km compared to the height obtained by the other three data sets. In the 50–80 km altitude range, estimates of mesospheric O3 diurnal variation obtained from the GBMS and the convolved satellite measurements agree well within the ±1 standard deviation (~ 0.6 ppmv) of the GBMS mean profile. 2012-04-12T22:00:00Z http://hdl.handle.net/2122/7539 Title: Changes in atmospheric composition discerned from long-term NDACC measurements: evolution of the winter stratosphere from Thule, Greenland, and the exceptional winters of 2008-2009 and 2010-2011. Authors: Di Biagio, C.; ENEA Centro Ricerche Casaccia - UTMEA, SP 091, via Anguillarese 301 I-00123 Roma (RM) ITALY; Bertagnolio, P. P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cacciani, M.; Sapienza Università di Roma, Piazzale Aldo Moro 2, I-00185 Roma - Italy; di Sarra, A.; ENEA Centro Ricerche Casaccia - UTMEA, SP 091, via Anguillarese 301 I-00123 Roma (RM) ITALY; Eriksen, P.; Danish Meteorological Institute, Lyngbyvej 100, DK-2100 Copenhagen E, Denmark; Fuà, D.; Sapienza Università di Roma, Piazzale Aldo Moro 2, I-00185 Roma - Italy; Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia Abstract: Several instruments are operational at Thule Air Base (76.5oN, 68.8oW) as part of the Network for Detection of Atmospheric Composition Change. A lidar was installed in 1990 and has been operational particularly during the winter season. Lidar measurements are used to derive the aerosol backscatter ratio between about 10 and 35 km, and the atmospheric temperature (T) profile from 25 up to 70 km, with a resolution of 150 m. A ground-based millimeter-wave spectrometer (GBMS) was installed at Thule in 2001, and has been operational during the winter seasons of 2001-2003 and 2009-2011. The GBMS permits to derive the atmospheric concentration profiles of different chemical species, such as O3, CO, N2O, and HNO3, between about 15 and 80 km at a resolution of 6-8 km. The Arctic winter stratosphere is characterized by a high variability, and detection of trends is particularly difficult. The evolution of the vortex and the temperatures in the lower stratosphere has a large impact on formation of Polar Stratospheric Clouds (PSC) and on the stratosphere chemical evolution. Coldest winters occurred in 1999-2000, and 2004-2005. Intensive measurement campaigns were conducted at Thule Air Base during winters 2008-2009 and 2010-2011. These two winters have been deeply different in their thermal, dynamical and chemical evolution. The 2008-2009 Arctic winter has been characterized by the most intense Sudden Stratospheric Warming (SSW) event ever observed, and the maximum of this warming was detected over Greenland. Thus, ground-based observations of the thermal structure and chemical composition of the middle atmosphere from the station at Thule Air Base have permitted to show the evolution of the phenomenon and its interactions with the dynamical structure of the polar vortex in the region of maximum warming. On the contrary, the 2010-2011 has been a very cold winter, and polar stratospheric clouds have been detected by lidar from mid-February to mid-March at Thule Air Base. This very cold winter, together with the massive formation of PSCs, has caused the record stratospheric ozone loss that is occurring in spring 2011 in the Arctic. In this study, we will present a summary of the measurements of the thermal and chemical stratospheric structure obtained at Thule Air Base between 1990 and 2011, with special attention to the two winters of 2008-2009 and 2010-2011. 2011-10-23T22:00:00Z http://hdl.handle.net/2122/7410 Title: Intercomparison between Aura MLS and ground-based millimeter-wave observations of stratospheric O3 and HNO3 from Thule (76.5° N, 68.7° W) Authors: Fiorucci, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Froidevaux, L.; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA; Santee, M.; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA; Manney, G. L.; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA Abstract: The Ground-Based Millimeter-wave Spectrometer (GBMS) measures rotational emission spectra of middle atmospheric trace gases, with a spectral window of 600 MHz tunable between approximately 230 and 280 GHz and a resolution of up to 65 kHz. It was designed and built at the State University of New York at Stony Brook in the early 90’s and since then has been regularly upgraded and operated at a variety of sites in both hemispheres, at polar and mid-latitudes. In view of a growing need for long-term data sets of stratospheric constituents, in January 2009 we resolved to establish a long-term GBMS observation site at the Arctic station of Thule Air Base (76.5°N, 68.8°W), Greenland, in order to track the long- and short-term interactions between the changing climate and the seasonal processes tied to the ozone depletion phenomenon. Since then three winter campaigns were carried out from Thule during the period January-March 2009, 2010 and 2011. Observations of O3, HNO3, CO and N2O were performed, mostly on a daily basis, except during periods characterized by poor weather conditions. In this study we compare GBMS stratospheric O3 and HNO3 measurements obtained during these three winter periods at Thule with colocated satellite observations from the Aura Microwave Limb Sounder (MLS) experiment. The Version 3.3 Aura MLS O3 and HNO3 data sets have a resolution of about 2.5 km and 3-4 km, respectively, in the stratosphere. The MLS precisions range from 0.1 to 0.6 ppmv for O3 and about 0.6-0.7 ppbv for HNO3 throughout the stratosphere. Based on preliminary comparisons with correlative data sets and on results obtained for v2.2, systematic uncertainties are estimated to lead to HNO3 measurements biases that vary between ±0.5 and ±2 ppbv and multiplicative errors of ±5 –15% throughout most of the stratosphere. Similarly, a systematic uncertainty of the order of 5-10% has been assessed for O3 data. As for the GBMS, the O3 pure rotational transition line at 276.923 GHz is observed with a ~1.5-hour integration, while the weaker HNO3 spectrum, represented by a cluster of superimposed emission lines centered at 269.1 GHz, needs about 4 hours of integration. Taking advantage of the dependence of the line broadening on atmospheric pressure, inversion techniques allow the retrieval of vertical profiles from approximately 15 to 50 km. In the past, GBMS O3 and HNO3 spectra were deconvolved using a Chahine-Twomey (C-T) and an iterative constrained Matrix Inversion (MI) technique, respectively. More recently, the GBMS retrieval algorithm has been updated to an Optimal Estimation Method (OEM) in order to conform to the standard of the NDACC microwave group, and to easily provide retrievals with a set of averaging kernels that grants more straightforward comparisons with other data sets. The nominal vertical resolution of the retrieved profiles (defined as the FWHM of averaging kernels) is ~8 km for O3 and ~ 12 km for HNO3, although the inversion technique locates the maximum of the mixing ratio profile of both species with a much better accuracy (i.e., ~ ±1 km). The 1σ uncertainty of O3 and HNO3 mixing ratio vertical profiles depends on altitude and is estimated at ~15% or 0.3 ppbv, whichever is larger. Each GBMS profile is compared to the closest MLS profile, with coincidence criteria of ±10° longitude, ±2.5° latitude and ±12 h. In order to avoid of severely compromising the comparison between GBMS and Aura MLS observations due to the much higher resolution of the satellite-derived data sets, we ‘convolved’ the MLS profiles using the GBMS averaging kernels before directly comparing the two data sets. For both species a fairly good agreement between MLS and GBMS profiles is observed, with the GBMS showing, however, a ~10-15% low bias at the mixing ratio peak. 2011-11-06T23:00:00Z http://hdl.handle.net/2122/7076 Title: Revising the retrieval technique of a long-term stratospheric HNO3 data set: from a constrained matrix inversion to the optimal estimation algorithm Authors: Fiorucci, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; de Zafra, R. L.; Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY, USA Abstract: The Ground-Based Millimeter-wave Spectrometer (GBMS) was designed and built at the State University of New York at Stony Brook in the early 1990s and since then has carried out many measurement campaigns of stratospheric O3, HNO3, CO and N2O at polar and mid-latitudes. Its HNO3 data set shed light on HNO3 annual cycles over the Antarctic continent and contributed to the validation of both generations of the satellite-based JPL Microwave Limb Sounder (MLS). Following the increasing need for long-term data sets of stratospheric constituents, we resolved to establish a long-term GMBS observation site at the Arctic station of Thule (76.5 N, 68.8 W), Greenland, beginning in January 2009, in order to track the long- and short-term interactions between the changing climate and the seasonal processes tied to the ozone depletion phenomenon. Furthermore, we updated the retrieval algorithm adapting the Optimal Estimation (OE) method to GBMS spectral data in order to conform to the standard of the Network for the Detection of Atmospheric Composition Change (NDACC) microwave group, and to provide our retrievals with a set of averaging kernels that allow more straightforward comparisons with other data sets. The new OE algorithm was applied to GBMS HNO3 data sets from 1993 South Pole observations to date, in order to produce HNO3 version 2 (v2) profiles. A sample of results obtained at Antarctic latitudes in fall and winter and at mid-latitudes is shown here. In most conditions, v2 inversions show a sensitivity (i.e., sum of column elements of the averaging kernel matrix) of 100±20% from 20 to 45 km altitude, with somewhat worse (better) sensitivity in the Antarctic winter lower (upper) stratosphere. The 1 uncertainty on HNO3 v2 mixing ratio vertical profiles depends on altitude and is estimated at 15% or 0.3 ppbv, whichever is larger. Comparisons of v2 with former (v1) GBMS HNO3 vertical profiles, obtained employing the constrained matrix inversion method, show that v1 and v2 profiles are overall consistent. The main difference is at the HNO3 mixing ratio maximum in the 20–25 km altitude range, which is smaller in v2 than v1 profiles by up to 2 ppbv at mid-latitudes and during the Antarctic fall. This difference suggests a better agreement of GBMS HNO3 v2 profiles with both UARS/ and EOS Aura/MLS HNO3 data than previous v1 profiles. 2011-07-26T22:00:00Z http://hdl.handle.net/2122/6979 Title: Water vapor sounding with the far infrared REFIR-PAD spectroradiometer from a high-altitude ground-based station during the ECOWAR campaign Authors: Bianchini, G.; Istituto di Fisica Applicata “Nello Carrara,” Consiglio Nazionale delle Ricerche, Sesto Fiorentino, Italy; Palchetti, L.; Istituto di Fisica Applicata “Nello Carrara,” Consiglio Nazionale delle Ricerche, Sesto Fiorentino, Italy; Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Fiorucci, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Di Girolamo, P.; Dipartimento di Ingegneria e Fisica dell’Ambiente, Università della Basilicata, Potenza, Italy; Di Iorio, T.; Dipartimento di Fisica, Università di Roma “La Sapienza,” Rome, Italy Abstract: The Radiation Explorer in the Far InfraRed-Prototype for Applications and Development (REFIR-PAD) spectroradiometer was operated from the Testa Grigia Italian-Alps station in March 2007 during the Earth Cooling by Water Vapour Radiation (ECOWAR) measurement campaign, obtaining downwelling radiance spectra in the 100–1100 cm−1 range, under clear-sky conditions and in the presence of cirrus clouds. The analysis of these measurements has proven that the instrument is capable of determining precipitable water vapor with a total uncertainty of 5–7% by using the far-infrared rotational band of water. The measurement is unaffected by the presence of cirri, whose optical depth can be instead retrieved as an additional parameter. Information on the vertical profiles of water vapor volume mixing ratio and temperature can also be retrieved for three altitude levels. The ability to measure the water vapor column with a simple, uncooled instrument, capable of operating continuously and with a time resolution of about 10 min, makes REFIR-PAD a very valuable instrument for meteorological and climatological studies for the characterization of the water vapor distribution. 2011-01-27T23:00:00Z http://hdl.handle.net/2122/6662 Title: Cross-calibration of UARS and Aura MLS HNO3 data sets by means of ground-based millimeter-wave Observations Authors: Fiorucci, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Froidevaux, L.; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA; Santee, M. L.; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA; De Zafra, R. L.; State University of New York, Stony Brook, NY, USA Abstract: Nitric acid (HNO3) is a major player in processes controlling the springtime depletion of polar ozone. It is the main constituent of the Polar Stratospheric Clouds (PSCs) and a primary reservoir for reactive nitrogen. Potential variations in the stratospheric circulation and temperature may alter the extent and duration of PSCs activity, influencing the future ozone levels significantly. Monitoring HNO3 and its long-term variability, especially in polar region, is then crucial for better understanding issues related to ozone decline and expected recovery. In this study we present an intercomparison between ground based HNO3 measurements, carried out by means of the Ground-Based Millimeter-wave Spectrometer (GBMS), and two satellite data sets produced by the two NASA/JPL Microwave Limb Sounder (MLS) experiments. In particular, we compare UARS MLS measurements (1991-1999) with those carried out by the GBMS at South Pole, Antarctica (90°S), Fall of 1993 and 1995. A similar intercomparison is made between Aura MLS HNO3 observations (2004 - to date) and GBMS measurements obtained during the period February 2004 - March 2007, at the mid-latitudes/high altitudes station of Testa Grigia (45.9° N, 7.7° E, elev. 3500 m), and during polar winters 2008/09 and 2009/2010 at Thule Air Base (76.5°N 68.8°W), Greenland. We assess systematic differences between GBMS and both UARS and Aura HNO3 data sets at seven potential temperature levels (θ) spanning the range 465 – 960 K. The UARS data set advected to the South Pole shows a low bias, within 20% for all θ levels but the 960 K, with respect to GBMS measurements. A very good agreement, within 5%, is obtained between Aura and GBMS observations at Testa Grigia, while larger differences, possibly due to latitude dependent effects, are observed over Thule. These differences are under further investigations but a preliminary comparison over Thule among MLS v3, GBMS, and ACE-FTS measurements suggests that GBMS measurements carried out during winter 2009 might not be reliable. These comparisons have been performed in the framework of the NASA JPL GOZCARDS project, which is aimed at developing a long-term, global data record of the relevant stratospheric constituents in the context of ozone decline. GBMS has been selected in GOZCARDS since its HNO3 dataset, although sampling different latitudes in different years, is the only one spanning a sufficiently long time interval for cross-calibrating HNO3 measurements by the UARS and Aura MLS experiments. 2010-09-26T22:00:00Z http://hdl.handle.net/2122/6416 Title: Development of A 22‐GHz ground‐based spectrometer for middle atmospheric water vapour monitoring Authors: Bertagnolio, Pietro P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Baskaradas, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Water vapour is a crucial element of the climate system. Accurate observations of stratospheric humidity are needed in the equatorial belt, where most water vapour crosses the tropopause, and in the polar regions, that are most affected by climate change trends. Satellite-based observations provide atmospheric composition data with extensive spatial and temporal coverage, but these need to be validated and integrated by ground-based networks like GAW (Global Atmospheric Watch) and NDACC (Network for Detection of Atmospheric Composition Change). This contribution presents a new ground-based spectrometer for the observation of middle atmospheric humidity profiles being currently developed at INGV - Istituto Nazionale di Geofisica e Vulcanologia. The instrument will detect the water vapour spectral line at 22.235 GHz by using the balanced beam-switching observation technique. The receiver antenna system has a parabolic mirror and a corrugated horn with an overall HPBW of 3.5°. Preliminary tests of the horn performed at the Table Mountain Facility of the Jet Propulsion Laboratory, California are presented. An uncooled GaAsFET low-noise amplifier was custom-assembled for the receiver front-end. The back-end will be a FFT spectrometer with a 1 GHz bandwidth and a 63 kHz resolution which, given the pressure broadening coefficient of the H2O line, will allow to retrieve concentration profiles from about 15 to 80 km altitude. Since the retrieval altitude range is also limited by the spectral signal-to-noise ratio and baseline artifacts, special care is taken in minimizing receiver noise temperature. Low noise temperatures will imply integration times short enough to be able to observe diurnal changes in the lower stratosphere. In order to extend unmanned operation time and limit LN2 supplies at remote stations, calibrated noise sources will be used as cold load reference on a daily basis. The control interface, which is also under development at INGV, will be based on reconfigurable hardware (USB-CPLD). Several different sites are proposed for permanent installation. Among these the GAW sites of Thule Airbase, Greenland for polar monitoring, or Mount Chacaltaya, Bolivia, for tropical tropopause observations. 2010-10-03T22:00:00Z http://hdl.handle.net/2122/6345 Title: Water vapor sounding with the far infrared REFIR-PAD spectroradiometer from a high-altitude ground-based station during the ECOWAR campaign Authors: Bianchini, G.; Istituto di Fisica Applicata “Nello Carrara” (IFAC-CNR), Sesto Fiorentino, Italy; Palchetti, L.; Istituto di Fisica Applicata “Nello Carrara” (IFAC-CNR), Sesto Fiorentino, Italy; Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Fiorucci, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Di Girolamo, P.; Dipartimento di Ingegneria e Fisica dell’Ambiente, Universit`a della Basilicata, Potenza, Italy; Di Iorio, T.; Dipartimento di Fisica, Universit`a di Roma “La Sapienza”, Roma, Italy Abstract: The REFIR-PAD spectroradiometer was operated from the Testa Grigia Italian-Alps station in March 2007 during the Earth COoling by WAter vapouR emission (ECOWAR) measurement campaign, obtaining downwelling radiance spectra in the 100-1100 cm−1 range, under clear-sky condition and in the presence of cirrus clouds. The analysis of these mea surements has proven that the instrument is capable of determining precipitable water vapor with a total uncertainty of 5–7% by using the far-infrared rotational band of water. The measurement is unaffected by the presence of cirri, whose optical depth can be instead retrieved as an additional parameter. Information on the vertical profiles of water vapor volume mixing ratio and temperature can also be retrieved for three altitude levels. The ability to measure the water vapor column with a simple, uncooled instrument, capable of operating continuously and with a time resolution of about 10 minutes makes REFIR-PAD a very valuable instrument for meteorological and climatological studies for the characterization of the water vapor distribution. 2009-12-31T23:00:00Z http://hdl.handle.net/2122/6237 Title: Evolution of temperature, O3, CO, and N2O profiles during the exceptional 2009 Arctic major stratospheric warming as observed by lidar and mm-wave spectroscopy at Thule (76.5°N, 68.8°W), Greenland. Authors: Di Biagio, C.; ENEA/UTMEA-TER, S. Maria di Galeria, Italy and Department of Earth Science, University of Siena, Siena, Italy; Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; di Sarra, A.; ENEA/UTMEA-TER, S. Maria di Galeria, Italy; de Zafra, R. L.; Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA; Eriksen, P.; Danish Meteorological Institute, Copenhagen, Denmark; Fiocco, G.; Department of Physics, “Sapienza” University of Rome, Rome, Italy; Fiorucci, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Fuà, D.; Department of Physics, “Sapienza” University of Rome, Rome, Italy Abstract: The 2009 Arctic sudden stratospheric warming (SSW) was the most intense event of this kind ever observed. Unique ground-based measurements of middle atmospheric profiles for temperature, O3, CO, and N2O obtained at Thule (76.5°N, 68.8°W), Greenland, in the period January – early March are used to show the evolution of the 2009 SSW in the region of its maximum intensity. The first sign of the SSW was detected at θ~2000 K on January 19, when a rapid decrease in CO mixing ratio took place. The first evidence of a temperature increase was observed at the same level on 22 January, the earliest date on which lidar measurements reached above ~50 km. The warming propagated from the upper to the lower stratosphere in 7 days and the record maximum temperature of 289 K was observed between 1300 and 1500 K potential temperature on 22 January. A strong vortex splitting was associated with the SSW. Stratospheric backward trajectories indicate that airmasses arriving to Thule during the warming peak underwent a rapid compression and an intense adiabatic warming of up to 50 K. The rapid advection of air from the extra-tropics was also occasionally observed to produce elevated values of N2O mixing ratio. Starting from mid-February the temperature profile and the N2O mixing ratio returned to the pre-warming values in the mid and upper stratosphere, indicating the reformation of the vortex at these levels. In late winter, vertical descent from starting altitudes of ~60 km is estimated from CO profiles to be 0.25±0.05 km/day. 2009-12-31T23:00:00Z http://hdl.handle.net/2122/5315 Title: An Intercomparison of Precipitable Water Vapor Measurements Obtained During the ECOWAR Field Campaign Authors: Fiorucci, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Di Girolamo, P.; Dipartimento di Ingegneria e Fisica dell'Ambiente, Università della Basilicata, Potenza, Italy; Esposito, F.; Dipartimento di Ingegneria e Fisica dell'Ambiente, Università della Basilicata, Potenza, Italy; Grieco, G.; Dipartimento di Ingegneria e Fisica dell'Ambiente, Università della Basilicata, Potenza, Italy; Summa, D.; Dipartimento di Ingegneria e Fisica dell'Ambiente, Università della Basilicata, Potenza, Italy; Bianchini, G.; Istituto di Fisica Applicata "Nello Carrara", IFAC-CNR, Sesto Fiorentino, Firenze, Italy; Palchetti, L.; Istituto di Fisica Applicata "Nello Carrara", IFAC-CNR, Sesto Fiorentino, Firenze, Italy; Cacciani, M.; Dipartimento di Fisica, Università di Roma "La Sapienza", Roma, Italy; Di Iorio, T.; Dipartimento di Fisica, Università di Roma "La Sapienza", Roma, Italy; Pavese, G.; Istituto di Metodologie per l’Analisi Ambientale, IMAA-CNR, Tito Scalo, Potenza, Italy; Cimini, D.; CETEMPS, Dipartimento di Fisica, Università di L’Aquila, L’Aquila, Italy; de Zafrah, R. L.; Department of Physics and Astronomy, and Institute for Terrestrial and Planetary Atmospheres, State University of New York, Stony Brook, U.S.A. Abstract: In this study we present an intercomparison of measurements of very low water vapor column content obtained with a Ground-Based Millimeter-wave Spectrometer (GBMS), Vaisala RS92k radiosondes, a Raman Lidar, and an IR Fourier Transform Spectrometer. These sets of measurements were carried out during the primary field campaign of the ECOWAR (Earth COoling by WAter vapor Radiation) project which took place on the Western Italian Alps from 3 to 16 March, 2007. 2009-03-10T23:00:00Z