scholarly journals VESPA-22: a ground-based microwave spectrometer for long-term measurements of Polar stratospheric water vapor

2017 ◽  
Author(s):  
Gabriele Mevi ◽  
Giovanni Muscari ◽  
Pietro Paolo Bertagnolio ◽  
Irene Fiorucci ◽  
Giandomenico Pace
Keyword(s):  
Water Vapor ◽  
Weather Conditions ◽  
Black Body ◽  
High Arctic ◽  
Frequency Resolution ◽  
Integration Time ◽  
Vertical Profiles ◽  
Stratospheric Water Vapor ◽  
Sensitivity Range ◽  
Half Power

Abstract. The new ground-based 22 GHz spectrometer, VESPA-22 (water Vapor Emission Spectrometer for Polar Atmosphere at 22 GHz) measures the 22.23 GHz water vapor emission line with a bandwith of 500 MHz and a frequency resolution of 31 kHz. The integration time for a measurement is of the order of hours, depending on season and weather conditions. Water vapor spectra are collected using the beam switching technique. VESPA-22 is designed to operate automatically with minimum need of maintenance; it employs an uncooled front-end characterized by a receiver temperature of about 180 K and its quasi-optical system presents a half power full beam angle of 3.5°. VESPA-22 measures also the sky opacity with a temporal resolution of two measurements an hour using the tipping curve technique. The instrument calibration is performed automatically by a noise diode; the emission temperature of this element is measured two times an hour through the observation of a black body at ambient temperature and of the sky at 60° of elevation. The retrieved profiles obtained inverting a 24-hour integration spectra present a sensitivity higher than 0.8 from about 25 to 72 km of altitude, a vertical resolution from about 12 to 23 km (depending on altitude) and an overall 1σ uncertainty between 5 and 12 %. In July 2016, VESPA-22 was installed at the THAAO (Thule High Arctic Atmospheric Observatory) located at Thule Air Base (76.5° N, 68.8° W), Greenland, and has been operating almost continuously since then, with very few interruption periods characterized by poor weather. The VESPA-22 water vapor mixing ratio vertical profiles discussed in this work cover the period from July 2016 to May 2017 and are compared with Version 4.2 of concurrent Aura/MLS (Waters et al., 2006) water vapor vertical profiles. In the sensitivity range of VESPA-22 retrievals, the intercomparison between the VESPA-22 dataset and Aura/MLS dataset convolved with VESPA-22 averaging kernels reveals a correlation coefficient of about 0.9 or higher and an average difference reaching its maximum of −6 % or −0.2 ppmv at the top of the sensitivity range.

scholarly journals VESPA-22: a ground-based microwave spectrometer for long-term measurements of polar stratospheric water vapor

2018 ◽  
Vol 11 (2) ◽  
pp. 1099-1117 ◽  
Author(s):  
Gabriele Mevi ◽  
Giovanni Muscari ◽  
Pietro Paolo Bertagnolio ◽  
Irene Fiorucci ◽  
Giandomenico Pace
Keyword(s):  
Water Vapor ◽  
Weather Conditions ◽  
Black Body ◽  
High Arctic ◽  
Frequency Resolution ◽  
Integration Time ◽  
Vertical Profiles ◽  
Stratospheric Water Vapor ◽  
Water Vapor Mixing Ratio ◽  
Beam Switching

Abstract. The new ground-based 22 GHz spectrometer, VESPA-22 (water Vapor Emission Spectrometer for Polar Atmosphere at 22 GHz) measures the 22.23 GHz water vapor emission line with a bandwidth of 500 MHz and a frequency resolution of 31 kHz. The integration time for a measurement ranges from 6 to 24 h, depending on season and weather conditions. Water vapor spectra are collected using the beam-switching technique. VESPA-22 is designed to operate automatically with little maintenance; it employs an uncooled front-end characterized by a receiver temperature of about 180 K and its quasi-optical system presents a full width at half maximum of 3.5∘. Every 30 min VESPA-22 measures also the sky opacity using the tipping curve technique. The instrument calibration is performed automatically by a noise diode; the emission temperature of this element is estimated twice an hour by observing alternatively a black body at ambient temperature and the sky at an elevation of 60∘. The retrieved profiles obtained inverting 24 h integration spectra present a sensitivity larger than 0.8 from about 25 to 75 km of altitude during winter and from about 30 to 65 km during summer, a vertical resolution from about 12 to 23 km (depending on altitude), and an overall 1σ uncertainty lower than 7 % up to 60 km altitude and rapidly increasing to 20 % at 75 km. In July 2016, VESPA-22 was installed at the Thule High Arctic Atmospheric Observatory located at Thule Air Base (76.5∘ N, 68.8∘ W), Greenland, and it has been operating almost continuously since then. The VESPA-22 water vapor mixing ratio vertical profiles discussed in this work are obtained from 24 h averaged spectra and are compared with version 4.2 of concurrent Aura/Microwave Limb Sounder (MLS) water vapor vertical profiles. In the sensitivity range of VESPA-22 retrievals, the intercomparison from July 2016 to July 2017 between VESPA-22 dataset and Aura/MLS dataset convolved with VESPA-22 averaging kernels shows an average difference within 1.4 % up to 60 km altitude and increasing to about 6 % (0.2 ppmv) at 72 km.

Inflight performance of the state-of-the-art BepiColombo MORE radio-tracking system 

2021 ◽  
Author(s):  
Paolo Cappuccio ◽  
Luciano Iess ◽  
Daniele Durante ◽  
Ivan di Stefano ◽  
Paolo Racioppa ◽  
...  
Keyword(s):  
Water Vapor ◽  
Tracking System ◽  
Weather Conditions ◽  
Integration Time ◽  
Path Delay ◽  
Noise Component ◽  
Ka Band ◽  
Range Measurements ◽  
Radio Science ◽  
Range Rate

<p>The ESA/JAXA mission BepiColombo, launched on 20 October 2018 is in cruise towards Mercury and will arrive at Mercury in 2025 to investigate its surface, interior structure and magnetosphere. The Mercury Orbiter Radio-science Experiment (MORE) onboard the Mercury Planetary Orbiter (MPO) aims at determining the gravity field, the rotational state and librations of the planet, using precise tracking of the spacecraft during its orbital phase around Mercury. Range and range-rate measurements collected during the cruise phase will be used to test the theory of general relativity starting in March 2021. The MORE experiment exploits two-way multifrequency microwave links from ESA and NASA: two downlinks in X- and Ka-band coherent with the X-band uplink and one Ka-band downlink coherent with the Ka-band uplink. The range-rate and range measurements accurately BepiColombo’s line-of-sight velocity and the round-trip light-time of the signal, respectively. The calibration of the dispersive plasma noise component through the combination of the X/X, X/Ka and Ka/Ka links and the use of water vapor radiometers to correct for the path delay due to Earth’s troposphere will result in an accuracy of ~3 µm/sec (at 1000-s integration time) on the Doppler and centimeter-level range accuracies. We report on the analysis of dedicated tests executed on range and Doppler data collected by ESA and NASA stations at X and Ka-band. The comparison of the observed noise with the predictions shows results exceeding the expectations. In particular, the 24 Mcps pseudo-noise modulation of the Ka-band carrier, enabled by MORE’s KaT transponder built by Thales Alenia Space Italia, provided two-way range measurements accurate to ~3 cm with just 4 s integration time, at a distance of 0.7 AU, September 2021, and 1.3 AU, November 2021. Under favorable weather conditions, the range rate has shown an accuracy of 25 µm/s at 10 s integration time, in line with the expected end-to-end performance. Under unfavorable weather conditions the performance was slightly over the requirements. We must remark that calibrations from water vapor radiometers were not available during these tests and only GNSS calibration were applied.</p>

scholarly journals Two-year operation of the lidar1200: from fine-scale tropospheric structures to lower stratospheric water vapor detection

2018 ◽  
Vol 176 ◽  
pp. 05015
Author(s):  
Hélène Vérèmes ◽  
Guillaume Payen ◽  
Philippe Keckhut ◽  
Valentin Duflot ◽  
Jean-Luc Baray ◽  
...  
Keyword(s):  
Water Vapor ◽  
Lower Stratosphere ◽  
Integration Time ◽  
Fine Scale ◽  
Vertical Resolution ◽  
Vapor Detection ◽  
Stratospheric Water Vapor ◽  
Frost Point ◽  
Time Period ◽  
Water Vapor Detection

The 2-year lidar water vapor database (November 2013 - October 2015) of the Maïdo Observatory (Reunion Island / 21°S,55.5°E) is now processed. The performances of the lidar in providing accurate vertical structures are shown to be good. The ability to measure quantities of a few ppmv in the lower stratosphere is demonstrated (based on Cryogenic Frost point Hygrometer sonde/lidar profiles comparisons) for a 48-hour integration time period, up to 22 km (with a vertical resolution of 1.3 km).

Hydrological Response of a Patchy High Arctic Wetland

2000 ◽  
Vol 31 (4-5) ◽  
pp. 317-338 ◽  
Author(s):  
Kathy L. Young ◽  
Ming-ko Woo
Keyword(s):  
Weather Conditions ◽  
High Arctic ◽  
Ground Ice ◽  
Ice Melt ◽  
Snow Storage ◽  
Streamflow Response ◽  
Dry Seasons ◽  
And Storage ◽  
Surface And Subsurface Flow ◽  
Present Understanding

High Arctic patchy wetlands are ecological oases in a polar desert environment and are vulnerable to climatic warming. At present, understanding of their responses to external factors (climate and terrain) is limited. This study examines a wetland located in a topographic depression maintained by seasonal snowmelt, ground ice melt and lateral inflows. The wetland is located on Cornwallis Island, Nunavut, Canada. Hydrological, climatological and soil observations were made over several summers with different weather conditions. The summers of 1996 and 1997 were cool and wet but the summer of 1998 was warm and dry. The melt in 1996 was rapid due to rain on snow events and only lasted six days. Deeper snow in 1997 prolonged the melt season to 18 days. A shallow snow-cover in 1998 and early melt depleted the snow by early June. Surface, groundwater and storage fluctuations in the wetland were dictated by snowmelt, rainfall, evaporation loss from the wetland and lateral inputs which in turn were controlled by the melting of the late-lying snow storage in the catchment. Soil factors influence the spatial variations in ground thaw which affects the surface and subsurface flow. Streamflow response of the wetland reflects a nival regime and augmentation of streamflow thoughout the summer season in all three years is supported by multiple water sources: ground ice melt and suprapermafrost water from a large late-lying snowpack. Overall, this study suggests that the survival of some patchy wetlands depends on their interaction with the surrounding basin, with a dependency probably being more important during warm and dry seasons.

scholarly journals Impacts of Ozone Changes in the Tropopause Layer on Stratospheric Water Vapor

Atmosphere ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 291
Author(s):  
Jinpeng Lu ◽  
Fei Xie ◽  
Hongying Tian ◽  
Jiali Luo
Keyword(s):  
Water Vapor ◽  
Ozone Depletion ◽  
Climate Model ◽  
Global Climate ◽  
Stratospheric Water Vapor ◽  
Radiative Processes ◽  
Low Latitudes ◽  
Cold Point ◽  
The Impact ◽  
Tropopause Temperature

Stratospheric water vapor (SWV) changes play an important role in regulating global climate change, and its variations are controlled by tropopause temperature. This study estimates the impacts of tropopause layer ozone changes on tropopause temperature by radiative process and further influences on lower stratospheric water vapor (LSWV) using the Whole Atmosphere Community Climate Model (WACCM4). It is found that a 10% depletion in global (mid-low and polar latitudes) tropopause layer ozone causes a significant cooling of the tropical cold-point tropopause with a maximum cooling of 0.3 K, and a corresponding reduction in LSWV with a maximum value of 0.06 ppmv. The depletion of tropopause layer ozone at mid-low latitudes results in cooling of the tropical cold-point tropopause by radiative processes and a corresponding LSWV reduction. However, the effect of polar tropopause layer ozone depletion on tropical cold-point tropopause temperature and LSWV is opposite to and weaker than the effect of tropopause layer ozone depletion at mid-low latitudes. Finally, the joint effect of tropopause layer ozone depletion (at mid-low and polar latitudes) causes a negative cold-point tropopause temperature and a decreased tropical LSWV. Conversely, the impact of a 10% increase in global tropopause layer ozone on LSWV is exactly the opposite of the impact of ozone depletion. After 2000, tropopause layer ozone decreased at mid-low latitudes and increased at high latitudes. These tropopause layer ozone changes at different latitudes cause joint cooling in the tropical cold-point tropopause and a reduction in LSWV. Clarifying the impacts of tropopause layer ozone changes on LSWV clearly is important for understanding and predicting SWV changes in the context of future global ozone recovery.

scholarly journals Assessment of Sampling Effects on Various Satellite-Derived Integrated Water Vapor Datasets Using GPS Measurements in Germany as Reference

2020 ◽  
Vol 12 (7) ◽  
pp. 1170 ◽  
Author(s):  
Cintia Carbajal Henken ◽  
Lisa Dirks ◽  
Sandra Steinke ◽  
Hannes Diedrich ◽  
Thomas August ◽  
...  
Keyword(s):  
Water Vapor ◽  
Pairwise Comparison ◽  
Weather Conditions ◽  
Satellite System ◽  
High Temporal Resolution ◽  
Data Sets ◽  
Frequency Distributions ◽  
Temporal Sampling ◽  
Global Navigation Satellite ◽  
Satellite Instruments

Passive imagers on polar-orbiting satellites provide long-term, accurate integrated water vapor (IWV) data sets. However, these climatologies are affected by sampling biases. In Germany, a dense Global Navigation Satellite System network provides accurate IWV measurements not limited by weather conditions and with high temporal resolution. Therefore, they serve as a reference to assess the quality and sampling issues of IWV products from multiple satellite instruments that show different orbital and instrument characteristics. A direct pairwise comparison between one year of IWV data from GPS and satellite instruments reveals overall biases (in kg/m 2 ) of 1.77, 1.36, 1.11, and −0.31 for IASI, MIRS, MODIS, and MODIS-FUB, respectively. Computed monthly means show similar behaviors. No significant impact of averaging time and the low temporal sampling on aggregated satellite IWV data is found, mostly related to the noisy weather conditions in the German domain. In combination with SEVIRI cloud coverage, a change of shape of IWV frequency distributions towards a bi-modal distribution and loss of high IWV values are observed when limiting cases to daytime and clear sky. Overall, sampling affects mean IWV values only marginally, which are rather dominated by the overall retrieval bias, but can lead to significant changes in IWV frequency distributions.

scholarly journals Effect of the Indo-Pacific Warm Pool on Lower-Stratospheric Water Vapor and Comparison with the Effect of ENSO

2018 ◽  
Vol 31 (3) ◽  
pp. 929-943 ◽  
Author(s):  
Fei Xie ◽  
Xin Zhou ◽  
Jianping Li ◽  
Quanliang Chen ◽  
Jiankai Zhang ◽  
...  
Keyword(s):  
Water Vapor ◽  
Climate Model ◽  
Southern Oscillation ◽  
Deep Convection ◽  
Warm Pool ◽  
Latent Heat Release ◽  
Stratospheric Water Vapor ◽  
Asymmetric Effects ◽  
Pacific Warm Pool ◽  
Tropopause Temperature

Abstract Time-slice experiments with the Whole Atmosphere Community Climate Model, version 4 (WACCM4), and composite analysis with satellite observations are used to demonstrate that the Indo-Pacific warm pool (IPWP) can significantly affect lower-stratospheric water vapor. It is found that a warmer IPWP significantly dries the stratospheric water vapor by causing a broad cooling of the tropopause, and vice versa for a colder IPWP. Such imprints in tropopause temperature are driven by a combination of variations in the Brewer–Dobson circulation in the stratosphere and deep convection in the troposphere. Changes in deep convection associated with El Niño–Southern Oscillation (ENSO) reportedly have a small zonal mean effect on lower-stratospheric water vapor for strong zonally asymmetric effects on tropopause temperature. In contrast, IPWP events have zonally uniform imprints on tropopause temperature. This is because equatorial planetary waves forced by latent heat release from deep convection project strongly onto ENSO but weakly onto IPWP events.

scholarly journals Features and trends in Atmospheric Trace Molecule Spectroscopy (ATMOS) version 3 stratospheric water vapor and methane measurements

2000 ◽  
Vol 105 (D18) ◽  
pp. 22713-22724 ◽  
Author(s):  
H. A. Michelsen ◽  
F. W. Irion ◽  
G. L. Manney ◽  
G. C. Toon ◽  
M. R. Gunson
Keyword(s):  
Water Vapor ◽  
Stratospheric Water Vapor

scholarly journals SPAN512: A new mid-latitude pulsar survey with the Nançay Radio Telescope

2012 ◽  
Vol 8 (S291) ◽  
pp. 375-377 ◽  
Author(s):  
Gregory Desvignes ◽  
Ismaël Cognard ◽  
David Champion ◽  
Patrick Lazarus ◽  
Patrice Lespagnol ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Large Scale ◽  
High Time ◽  
Frequency Resolution ◽  
Integration Time ◽  
Sensitivity Limit ◽  
Long Period ◽  
Large Bandwidth ◽  
L Band ◽  
Better Than

AbstractWe present an ongoing survey with the Nançay Radio Telescope at L-band. The targeted area is 74° ≲ l < 150° and 3.5° < |b| < 5°. This survey is characterized by a long integration time (18 min), large bandwidth (512 MHz) and high time and frequency resolution (64 μs and 0.5 MHz) giving a nominal sensitivity limit of 0.055 mJy for long period pulsars. This is about 2 times better than the mid-latitude HTRU survey, and is designed to be complementary with current large scale surveys. This survey will be more sensitive to transients (RRATs, intermittent pulsars), distant and faint millisecond pulsars as well as scintillating sources (or any other kind of radio faint sources) than all previous short-integration surveys.

scholarly journals A Lidar at Clermont-Ferrand—France to describe the boundary layer dynamics, aerosols, cirrus and tropospheric water vapor

2018 ◽  
Vol 176 ◽  
pp. 05047
Author(s):  
J.L. Baray ◽  
P. Fréville ◽  
N. Montoux ◽  
A. Chauvigné ◽  
D. Hadad ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Vertical Profiles ◽  
Raman Lidar ◽  
Tropospheric Aerosols ◽  
Boundary Layer Dynamics

A Rayleigh-Mie-Raman LIDAR provides vertical profiles of tropospheric variables at Clermont-Ferrand (France) since 2008, in order to describe the boundary layer dynamics, tropospheric aerosols, cirrus and water vapor. It is included in the EARLINET network. We performed hardware/software developments in order to upgrade the quality, calibration and improve automation. We present an overview of the system and some examples of measurements and a preliminary geophysical analysis of the data.

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