scholarly journals Calibration of Sun Radiometer–Based Atmospheric Water Vapor Retrievals Using GPS Meteorology

2007 ◽  
Vol 24 (6) ◽  
pp. 964-979 ◽  
Author(s):  
Amadou Idrissa Bokoye ◽  
Alain Royer ◽  
Patrick Cliche ◽  
Norm O’Neill
Keyword(s):  
Water Vapor ◽  
Signal Amplitude ◽  
Sensitivity Study ◽  
Geodetic Survey ◽  
Gps Receiver ◽  
Solar Absorption ◽  
Central Wavelength ◽  
Gps Meteorology ◽  
Absorption Channel ◽  
Calibration Tool

A study of the validation and calibration process for integrated water vapor (IWV) measurements derived from sun radiometry at the 940-nm solar absorption channel employed in the Aerosol Robotic Network (AERONET) Aerosol Canada (AEROCAN) is presented. The sun radiometer data are compared with GPS meteorology records used as a reference. Three Canadian sites from different climatic regimes covering the period 2000–04 are considered. The observations from five different sun radiometers (IWV-SUN) were processed using the initial AERONET IWV retrieval procedure (V1) whereas GPS-derived IWV (IWV-GPS) was retrieved using “GPSpace” software developed by the Geodetic Survey division of Natural Resources Canada. A sensitivity study is carried out to highlight the influence of both central wavelength and signal amplitude on the 940-nm filter characteristics, which are instrument dependent and can drift due to aging. The comparison between IWV-SUN (V1) and IWV-GPS shows an average rmse of 0.23 ± 0.11 g cm−2 (22%) and a mean bias of −0.09 ± 0.16 g cm−2 (9%). Furthermore, it is shown that the use of GPS for determining the 940-nm channel calibration constants for the solar radiometers improves IWV retrievals (rmse reduced by about 35% and bias by a factor of 3–10) without any knowledge of the 940-nm filter characteristics. These results are discussed within the context of the new AERONET IWV processing procedure (V2), which accounts for solar 940-nm region filter characteristics. The GPS receiver technique appears to be a powerful calibration tool because of its continuous observation capability, its robustness, and its operational simplicity.

scholarly journals The effects of aerosols on precipitation and dimensions of subtropical clouds: a sensitivity study using a numerical cloud model

2006 ◽  
Vol 6 (1) ◽  
pp. 67-80 ◽  
Author(s):  
A. Teller ◽  
Z. Levin
Keyword(s):  
Water Vapor ◽  
Climate Models ◽  
Cloud Model ◽  
Cloud Condensation Nuclei ◽  
Sensitivity Study ◽  
Meteorological Conditions ◽  
Dust Particles ◽  
Noticeable Effect ◽  
Convective Clouds ◽  
Ice Nuclei

Abstract. Numerical experiments were carried out using the Tel-Aviv University 2-D cloud model to investigate the effects of increased concentrations of Cloud Condensation Nuclei (CCN), giant CCN (GCCN) and Ice Nuclei (IN) on the development of precipitation and cloud structure in mixed-phase sub-tropical convective clouds. In order to differentiate between the contribution of the aerosols and the meteorology, all simulations were conducted with the same meteorological conditions. The results show that under the same meteorological conditions, polluted clouds (with high CCN concentrations) produce less precipitation than clean clouds (with low CCN concentrations), the initiation of precipitation is delayed and the lifetimes of the clouds are longer. GCCN enhance the total precipitation on the ground in polluted clouds but they have no noticeable effect on cleaner clouds. The increased rainfall due to GCCN is mainly a result of the increased graupel mass in the cloud, but it only partially offsets the decrease in rainfall due to pollution (increased CCN). The addition of more effective IN, such as mineral dust particles, reduces the total amount of precipitation on the ground. This reduction is more pronounced in clean clouds than in polluted ones. Polluted clouds reach higher altitudes and are wider than clean clouds and both produce wider clouds (anvils) when more IN are introduced. Since under the same vertical sounding the polluted clouds produce less rain, more water vapor is left aloft after the rain stops. In our simulations about 3.5 times more water evaporates after the rain stops from the polluted cloud as compared to the clean cloud. The implication is that much more water vapor is transported from lower levels to the mid troposphere under polluted conditions, something that should be considered in climate models.

scholarly journals Column water vapor determination in night period with a lunar photometer prototype

2013 ◽  
Vol 6 (1) ◽  
pp. 767-793
Author(s):  
A. Barreto ◽  
E. Cuevas ◽  
B. Damiri ◽  
P. M. Romero ◽  
F. Almansa
Keyword(s):  
Water Vapor ◽  
Comparative Study ◽  
Global Positioning System ◽  
High Mountain ◽  
Positioning System ◽  
Gps Receiver ◽  
Preliminary Results ◽  
Global Positioning ◽  
Lc Filter ◽  
Night Period

Abstract. In this paper we present the preliminary results of atmospheric column integrated water vapor (PWV) obtained with a new Lunar Cimel photometer (LC) at the high mountain Izaña Observatory in the period July–August, 2011. We have compared nocturnal PWV from LC with PWV from a Global Positioning System (GPS) receiver and nighttime radiosondes (RS92). LC data have been calibrated using the Lunar Langley Method (LLM). We complemented this comparative study using quasi-simultaneous daytime PWV from Cimel AERONET (CA), GPS and RS92. Comparison of daytime PWV from CA shows differences against GPS and RS92 up to 0.18 cm. Two different filters, with and approximate bandwidth of 10 nm and central wavelengths at 938 nm (Filter#1) and 937 nm (Filter#2), were mounted into the LC. Filter#1 is currently used in operational AERONET sunphotometers. PWV obtained with LC-Filter#1 showed an overestimation above 0.18 and 0.25 cm compared to GPS and RS92, respectively, meanwhile Filter#2, with a reduced out-of-band radiation, showed very low differences compared with the same references (≤0.03 cm). These results demonstrate the ability of the new lunar photometer to obtain accurate and continuous PWV measurements at night in addition to the notably influence of the filter's transmissivity response on PWV determination at nighttime. The use of enhanced bandpass filters in lunar photometry, which is affected by more important inaccuracies than sun-photometry, is necessary to infer PWV with similar precision than AERONET.

Retrieval of atmospheric water vapor columns from FT visible solar absorption spectra and evaluation of spectroscopic databases

2003 ◽  
Vol 82 (1-4) ◽  
pp. 133-150 ◽  
Author(s):  
Pierre-François Coheur ◽  
Cathy Clerbaux ◽  
Michel Carleer ◽  
Sophie Fally ◽  
Daniel Hurtmans ◽  
...  
Keyword(s):  
Water Vapor ◽  
Absorption Spectra ◽  
Atmospheric Water Vapor ◽  
Atmospheric Water ◽  
Solar Absorption

Water vapor isotopologues (H216O, H218O and HD16O) by ground-based FTIR spectroscopy in central Mexico

2021 ◽  
Author(s):  
Alain Zuber ◽  
Wolfgang Stremme ◽  
Adolfo Magaldi ◽  
Michel Grutter ◽  
Caludia Rivera ◽  
...  
Keyword(s):  
Water Vapor ◽  
Ftir Spectroscopy ◽  
Hydrological Cycle ◽  
Isotopic Ratio ◽  
Dew Point ◽  
Central Mexico ◽  
Isotopic Ratios ◽  
Solar Absorption ◽  
Rain Season ◽  
The Relationship

<p><span>Knowledge about water vapor isotopologues is a useful tool in the study of the hydrological cycle. Total columns of water vapor isotopologues (H</span><sub><span>2</span></sub><sup><span>16</span></sup><span>O, H</span><sub><span>2</span></sub><sup><span>18</span></sup><span>O and HD</span><sup><span>16</span></sup><span>O) are measured by ground-based solar absorption FTIR spectroscopy at Altzomoni (3985 m.a.s.l, 19.12ºN, 98.66ºW), a high altitude subtropical remote background site in central Mexico (Barthlott et al., 2017). In the contribution we present the time series of the isotopic composition of water vapor columns and profiles above central Mexico and analyze differences in the isotopic ratios of H</span><sub><span>2</span></sub><sup><span>16</span></sup><span>O, H</span><sub><span>2</span></sub><sup><span>18</span></sup><span>O and HD</span><sup><span>16</span></sup><span>O between the rain and dry seasons of the year: in the rain season, changes in the isotopic ratios might be dominated by the diurnal cycle, which correlates with the relative humidity, temperature and dew point, while isotopic ratio in the dry season might depend more on the origin of the air parcels and transportation. We discuss the hydrological cycle in central Mexico using the relationship between light and heavy isotopes, and how this relationship gives valuable information about the pathways, sources and transport.</span></p>

scholarly journals Mapping and Survey of Plasma Bubbles over Brazilian Territory

2006 ◽  
Vol 60 (1) ◽  
pp. 69-81 ◽  
Author(s):  
L. F. C. de Rezende ◽  
E. R. de Paula ◽  
I. J. Kantor ◽  
P. M. Kintner
Keyword(s):  
Ionospheric Plasma ◽  
Signal Amplitude ◽  
Gps Receiver ◽  
Tropical Regions ◽  
Plasma Irregularities ◽  
Plasma Bubbles ◽  
Receiver Array ◽  
Field Lines ◽  
Using Data ◽  
The Impact

Ionospheric plasma irregularities or bubbles, that are regions with depleted density, are generated at the magnetic equator after sunset due to plasma instabilities, and as they move upward they map along the magnetic field lines to low latitudes. To analyse the temporal and spatial evolution of the bubbles over Brazilian territory, the mapping of ionospheric plasma bubbles for the night of 17/18 March 2002 was generated using data collected from one GPS receiver array, and applying interpolation techniques. The impact on the performance of Global Navigation Satellites System (GNSS) and on the Space Based Augmentation System (SBAS) in the tropical regions of the GPS signal losses of lock and of the signal amplitude fades during ionospheric irregularities is presented.

scholarly journals The influence of snow sublimation and meltwater evaporation on <i>δ</i>D of water vapor in the atmospheric boundary layer of central Europe

2017 ◽  
Vol 17 (2) ◽  
pp. 1207-1225 ◽  
Author(s):  
Emanuel Christner ◽  
Martin Kohler ◽  
Matthias Schneider
Keyword(s):  
Water Vapor ◽  
Central Europe ◽  
Isotope Fractionation ◽  
Experimental Studies ◽  
Isotope Ratios ◽  
Sensitivity Study ◽  
Stable Water Isotopes ◽  
Uncertainty Range ◽  
Moisture Sources ◽  
Isotope Concentration

Abstract. Post-depositional fractionation of stable water isotopes due to fractionating surface evaporation introduces uncertainty to various isotope applications such as the reconstruction of paleotemperatures, paleoaltimetry, and the investigation of groundwater formation. In this study, we investigate isotope fractionation at snow-covered moisture sources by combining 17 months of observations of isotope concentration ratios [HD16O] ∕ [H216O] in low-level water vapor in central Europe with a new Lagrangian isotope model. The isotope model is capable of reproducing variations of the observed isotope ratios with a correlation coefficient R of 0.82. Observations from 38 days were associated with cold snaps and moisture uptake in snow-covered regions. Deviations between modeled and measured isotope ratios during the cold snaps were related to differences in skin temperatures (Tskin). Analysis of Tskin provided by the Global Data Assimilation System (GDAS) of the NCEP implies the existence of two regimes of Tskin with different types of isotope fractionation during evaporation: a cold regime with Tskin < Tsubl,max = −7.7 °C, which is dominated by non-fractionating sublimation of snow, and a warmer regime with Tsubl,max < Tskin < 0 °C, which is dominated by fractionating evaporation of meltwater. Based on a sensitivity study, we assess an uncertainty range of the determined Tsubl,max of −11.9 to −2.9 °C. The existence of the two fractionation regimes has important implications for the interpretation of isotope records from snow-covered regions as well as for a more realistic modeling of isotope fractionation at snow-covered moisture sources. For these reasons, more detailed experimental studies at snow-covered sites are needed to better constrain the Tsubl,max and to further investigate isotope fractionation in the two regimes.

Calibration of Sun radiometric integrated water vapor measurement using GPS meteorology

2004 ◽  
Author(s):  
Amadou I. Bokoye ◽  
Alain Royer ◽  
Richard Santer
Keyword(s):  
Water Vapor ◽  
Gps Meteorology

scholarly journals Validation of GPS atmospheric water vapor with WVR data in satellite tracking mode

2015 ◽  
Vol 33 (1) ◽  
pp. 55-61 ◽  
Author(s):  
M. Shangguan ◽  
S. Heise ◽  
M. Bender ◽  
G. Dick ◽  
M. Ramatschi ◽  
...  
Keyword(s):  
Water Vapor ◽  
Spatial Information ◽  
Microwave Radiometer ◽  
Research Centre ◽  
Gps Receiver ◽  
Ground Station ◽  
Independent Observations ◽  
Water Vapor Radiometer ◽  
Gps Station

Abstract. Slant-integrated water vapor (SIWV) data derived from GPS STDs (slant total delays), which provide the spatial information on tropospheric water vapor, have a high potential for assimilation to weather models or for nowcasting or reconstruction of the 3-D humidity field with tomographic techniques. Therefore, the accuracy of GPS STD is important, and independent observations are needed to estimate the quality of GPS STD. In 2012 the GFZ (German Research Centre for Geosciences) started to operate a microwave radiometer in the vicinity of the Potsdam GPS station. The water vapor content along the line of sight between a ground station and a GPS satellite can be derived from GPS data and directly measured by a water vapor radiometer (WVR) at the same time. In this study we present the validation results of SIWV observed by a ground-based GPS receiver and a WVR. The validation covers 184 days of data with dry and wet humidity conditions. SIWV data from GPS and WVR generally show good agreement with a mean bias of −0.4 kg m−2 and an rms (root mean square) of 3.15 kg m−2. The differences in SIWV show an elevation dependent on an rms of 7.13 kg m−2 below 15° but of 1.76 kg m−2 above 15°. Nevertheless, this elevation dependence is not observed regarding relative deviations. The relation between the differences and possible influencing factors (elevation angles, pressure, temperature and relative humidity) are analyzed in this study. Besides the elevation, dependencies between the atmospheric humidity conditions, temperature and the differences in SIWV are found.

scholarly journals Multi-Quartz Enhanced Photoacoustic Spectroscopy with Different Acoustic Microresonator Configurations

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Huadan Zheng ◽  
Xukun Yin ◽  
Lei Dong ◽  
Hongpeng Wu ◽  
Xiaoli Liu ◽  
...  
Keyword(s):  
Water Vapor ◽  
Absorption Coefficient ◽  
Photoacoustic Spectroscopy ◽  
Atmospheric Pressure ◽  
Noise Level ◽  
Signal Amplitude ◽  
Signal Enhancement ◽  
Vapor Detection ◽  
Water Vapor Detection

Acoustic microresonators were added to the recently developed multi-QTF based QEPAS spectrophone to enhance the signal amplitude. Two kinds of “on-beam” configurations were experimentally investigated in detail. The developed multi-QTF based “on-beam” spectrophone had a signal enhancement of 1.6 times compared with the traditional single QTF based “on-beam” spectrophone, with the approximate noise level. A normalized noise equivalent absorption coefficient (1σ) of 1.24 × 10−9 W·cm−1·Hz−1/2was obtained for water vapor detection at atmospheric pressure.

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