Dataset of surface water vapour density in southeast, Nigeria

Abstract. The spatio-temporal distribution of atmospheric water vapour information plays a crucial role in the establishment of modern numerical weather forecast models and description of the different weather variations. A troposphere tomographic method has been proposed considering the signal rays penetrating from the side of the area of interest to solve the problem of the low utilisation rate of global navigation satellite system (GNSS) observations. Given the method above needs the establishment of a unit scale factor model using the radiosonde data at only one location in the research area, an improved approach is proposed by considering the reasonability of modelling data and the diversity of the modelling parameters for building a more accurate unit scale factor model. The new established model is established using grid point data derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) and evenly distributed in the tomographic area, which can enhance the number of calculated initial water vapour density values with high accuracy. We validated the improved method with respect to the previous methods, as well as the result from a radiosonde using data from 12 stations from the Hong Kong Satellite Positioning Reference Station Network. The obtained result shows that the number of initial values estimated by the new model is increased by 6.83 %, while the internal and external accuracies are 0.08 and 0.24 g m−3, respectively. Integrated water vapour (IWV) and water vapour density profile comparisons show that the improved method is superior to previous studies in terms of RMS, MAE, and bias, which suggests higher accuracy and reliability.

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Evaluation of differential absorption radars in the 183 GHz band for profiling water vapour in ice clouds

10.5194/amt-2019-14 ◽

2019 ◽

Author(s):

Alessandro Battaglia ◽

Pavlos Kollias

Keyword(s):

Relative Humidity ◽

Water Vapour ◽

Vertical Resolution ◽

Differential Absorption ◽

Ice Clouds ◽

Microphysical Properties ◽

W Band ◽

Vapour Density ◽

Water Vapour Absorption ◽

The Right

Abstract. Relative humidity (RH) measurements in ice clouds are essential for determining the ice crystals growth processes and rates. A differential absorption radar (DAR) system with several frequency channels within the 183.3 GHz water vapour absorption band is proposed for measuring RH within ice clouds. Here, the performance of a DAR system is evaluated by applying a DAR simulator to A-Train observations in combination with collocated European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis. Observations from the CloudSat W-band radar and from the CALIPSO lidar are converted first into ice microphysical properties and then coupled with ECMWF temperature and relative humidity profiles in order to compute scattering properties at any frequency within the 183.3 GHz band. Self-similar Rayleigh Gans approximation is used to model the ice crystal scattering properties. The radar reflectivities are computed both for a space-borne and a ground-based DAR system by using appropriate radar receiver characteristics. Sets of multi-frequency synthetic observation of attenuated reflectivities are then used to retrieve profile of water vapour density by fitting the line shape at different levels. 10 days of A-Train observations are used to test the measurement technique performance for different combination of tones when sampling ice clouds globally. Results show that that water vapour densities can be derived with accuracies that can enable ice process studies (i.e. better than 3 %) both from a ground-based system (at the minute temporal scale and with circa 100 m vertical resolution) and from a space/airborne system (at 500 m vertical resolution and with circa 5 km integration lengths) with four tones in the right wing of the absorption line. A ground-based DAR system to be deployed at high latitude/high altitudes is highly recommended to test the findings of this work in the field.

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Evaluation of differential absorption radars in the 183 GHz band for profiling water vapour in ice clouds

Atmospheric Measurement Techniques ◽

10.5194/amt-12-3335-2019 ◽

2019 ◽

Vol 12 (6) ◽

pp. 3335-3349 ◽

Cited By ~ 5

Author(s):

Alessandro Battaglia ◽

Pavlos Kollias

Keyword(s):

Relative Humidity ◽

Water Vapour ◽

Vertical Resolution ◽

Ice Crystal ◽

Differential Absorption ◽

Ice Clouds ◽

Microphysical Properties ◽

W Band ◽

Vapour Density ◽

Water Vapour Absorption

Abstract. Relative humidity (RH) measurements in ice clouds are essential for determining ice crystal growth processes and rates. A differential absorption radar (DAR) system with several frequency channels within the 183.3 GHz water vapour absorption band is proposed for measuring RH within ice clouds. Here, the performance of a DAR system is evaluated by applying a DAR simulator to A-Train observations in combination with co-located European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis. Observations from the CloudSat W-band radar and from the CALIPSO lidar are converted first into ice microphysical properties and then coupled with ECMWF temperature and relative humidity profiles in order to compute scattering properties at any frequency within the 183.3 GHz band. A self-similar Rayleigh–Gans approximation is used to model the ice crystal scattering properties. The radar reflectivities are computed both for a space-borne and airborne and a ground-based DAR system by using appropriate radar receiver characteristics. Sets of multi-frequency synthetic observation of attenuated reflectivities are then exploited to retrieve profiles of water vapour density by fitting the line shape at different levels. A total of 10 d of A-Train observations are used to test the measurement technique performance for different combinations of tones when sampling ice clouds globally. Results show that water vapour densities can be derived at the level that can enable ice process studies (i.e. better than 3 %), both from a ground-based system (at the minute temporal scale and with circa 100 m vertical resolution) and from a space-borne system (at 500 m vertical resolution and with circa 5 km integration lengths) with four tones in the upper wing of the absorption line. Deploying ground-based DAR system at high latitudes and high altitudes is highly recommended to test the findings of this work in the field.

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X. Notes of researches on the polyammonias.—No. IX. Remarks on anomalous vapour-densities

Proceedings of the Royal Society of London ◽

10.1098/rspl.1859.0122 ◽

1860 ◽

Vol 10 ◽

pp. 596-598

Keyword(s):

Water Vapour ◽

Royal Society ◽

Ethylene Diamine ◽

Vapour Density

In a note addressed to the Royal Society at the commencement of this year, I have shown that the molecules of the diamines, like those of all other well-examined compounds, correspond to two volumes of vapour, and I have endeavoured to explain the apparent anomalous vapour-densities of the hydrated diamines by assuming that the vapour-volume experimentally obtained was a mixture of the vapour of the anhydrous base and of the vapour of water. Thus, hydrated ethylene-diamine was assumed to split under the influence of heat into anhydrous ethylene-diamine (2 vols. of vapour) and water (2 vols. of vapour). C 2 H 10 N 2 O = (C 2 H 4 )"} H 2 } H } H 2 }N 2 + H } O. The vapour-density of ethylene-diamine referred to hydrogen being 30, and that of water vapour 9, the vapour-density of a mixture of equal volumes of ethylene-diamine and water-vapour = 30 + 9/2 = 19·5, which closely agrees with the result of experiment.

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Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau

10.5194/acp-2016-8 ◽

2016 ◽

Cited By ~ 1

Author(s):

Mathieu Casado ◽

Amaelle Landais ◽

Valérie Masson-Delmotte ◽

Christophe Genthon ◽

Erik Kerstel ◽

...

Keyword(s):

Infrared Spectroscopy ◽

Surface Water ◽

Isotopic Composition ◽

Water Vapour ◽

Isotopic Fractionation ◽

Ice Cores ◽

Strong Impact ◽

Diurnal Cycles ◽

Surface Snow ◽

Dry Conditions

Abstract. Water stable isotopes in central Antarctic ice cores are critical to quantify past temperature changes. Accurate temperature reconstructions require to understand the processes controlling surface snow isotopic composition. Isotopic fractionation processes occurring in the atmosphere and controlling snowfall isotopic composition are well understood theoretically and implemented in atmospheric models. However, post-deposition processes are poorly documented and understood. To quantitatively interpret the isotopic composition of water archived in ice cores, it is thus essential to study the continuum between surface water vapour, precipitation, surface snow and buried snow. Here, we target the isotopic composition of surface snow, precipitation and water vapour at Concordia Station, where the oldest EPICA Dome C ice cores have been retrieved. While snowfall and surface snow sampling is routinely performed, accurate measurements of surface water vapour are challenging in such cold and dry conditions. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces. Two infrared spectrometers have been deployed at Concordia, allowing continuous, in situ measurements for one month in December–January 2014–2015. Comparison of the results from infrared spectroscopy with laboratory measurements of discrete samples trapped using cryogenic sampling validates the relevance of the method to measure isotopic composition in dry conditions. We observe very large diurnal cycles in isotopic composition well correlated with temperature diurnal cycles. Identification of different behaviours of isotopic composition in the water vapour associated with turbulent or stratified regime indicates a strong impact of meteorological processes in local vapour/snow interaction. Even if the vapour isotopic composition seems to be, at least part of the time, at equilibrium with the local snow, the slope of δD against δ18O prevents us from identifying a unique origin leading to this isotopic composition.

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