New parameterized model for GPS water vapor tomography

Abstract. Water vapor is the basic parameter used to describe atmospheric conditions. It is rarely contained in the atmosphere during the water cycle, but it is the most active element in rapid space–time changes. Measuring and monitoring the distribution and quantity of water vapor is a necessary task. GPS tomography is a powerful means of providing high spatiotemporal resolution of water vapor density. In this paper, a spatial structure model of a humidity field is constructed using voxel nodes, and new parameterizations for acquiring data about water vapor in the troposphere via GPS are proposed based on inverse distance weighted (IDW) interpolation. Unlike the density of water vapor that is constant within a voxel, the density at a certain point is determined by IDW interpolation. This algorithm avoids the use of horizontal constraints to smooth voxels that are not crossed by satellite rays. A prime number decomposition (PND) access order scheme is introduced to minimize correlation between slant wet delay (SWD) observations. Four experimental schemes for GPS tomography are carried out in dry weather from 2 to 8 August 2015 and rainy days from 9 to 15 August 2015. Using 14 days of data from the Hong Kong Satellite Positioning Reference Station Network (SatRef), the results indicate that water vapor density derived from 4-node methods is more robust than that derived from that of 8 nodes or 12 nodes, or that derived from constant refractivity schemes and the new method has better performance under stable weather conditions than unstable weather (e.g., rainy days). The results also indicate that an excessive number of interpolations in each layer reduce accuracy. However, the accuracy of the tomography results is gradually reduced with increases in altitude below 7000 m. Moreover, in the case of altitudes between 7000 m and the upper boundary layer, the accuracy can be improved by a boundary constraint.

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Estimating Water Vapor Using Signals from Microwave Links below 25 GHz

Remote Sensing ◽

10.3390/rs13081409 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1409

Author(s):

Kun Song ◽

Xichuan Liu ◽

Taichang Gao ◽

Peng Zhang

Keyword(s):

Water Vapor ◽

Weather Forecasting ◽

Water Cycle ◽

Correlation Coefficients ◽

Support Vector ◽

Vapor Density ◽

Measurement Resolution ◽

Sensing Model ◽

Numerical Weather Forecasting ◽

Mean Square Errors

Water vapor is a key element in both the greenhouse effect and the water cycle. However, water vapor has not been well studied due to the limitations of conventional monitoring instruments. Recently, estimating rain rate by the rain-induced attenuation of commercial microwave links (MLs) has been proven to be a feasible method. Similar to rainfall, water vapor also attenuates the energy of MLs. Thus, MLs also have the potential of estimating water vapor. This study proposes a method to estimate water vapor density by using the received signal level (RSL) of MLs at 15, 18, and 23 GHz, which is the first attempt to estimate water vapor by MLs below 20 GHz. This method trains a sensing model with prior RSL data and water vapor density by the support vector machine, and the model can directly estimate the water vapor density from the RSLs without preprocessing. The results show that the measurement resolution of the proposed method is less than 1 g/m3. The correlation coefficients between automatic weather stations and MLs range from 0.72 to 0.81, and the root mean square errors range from 1.57 to 2.31 g/m3. With the large availability of signal measurements from communications operators, this method has the potential of providing refined data on water vapor density, which can contribute to research on the atmospheric boundary layer and numerical weather forecasting.

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Diurnal changes of radio refraction

Symposium - International Astronomical Union ◽

10.1017/s0074180900065967 ◽

1979 ◽

Vol 89 ◽

pp. 163-164

Author(s):

Wilhelm J. Altenhoff

Keyword(s):

Water Vapor ◽

Prediction Accuracy ◽

Weather Conditions ◽

Diurnal Changes ◽

Vapor Density ◽

Density Data ◽

Severe Limitation ◽

Vapor Line ◽

Sky Brightness

Pathlength variations due to refraction changes in the troposphere may impose a severe limitation to VLB experiments (like random clock drifts). In connection with a VLB experiment Moran and Penfield (1976) analysed surface values of water vapor density, data of several hundred radiosonde launches and of measurements of sky brightness near the water vapor line at λ = 1.3 cm. They found that the surface values allow to estimate the pathlength to an accuracy of 5 cm in summer and 2 cm in winter. Sky brightness data give a prediction accuracy of 1.5 cm for all weather conditions, but for cloudfree conditions the accuracy was 0.3 cm.

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A New Method of GPS Water Vapor Tomography for Maximizing the Use of Signal Rays

Applied Sciences ◽

10.3390/app9071446 ◽

2019 ◽

Vol 9 (7) ◽

pp. 1446 ◽

Cited By ~ 3

Author(s):

Fei Yang ◽

Jiming Guo ◽

Junbo Shi ◽

Yinzhi Zhao ◽

Lv Zhou ◽

...

Keyword(s):

Water Vapor ◽

Density Profile ◽

Temporal Distribution ◽

Precipitable Water ◽

Absolute Error ◽

New Method ◽

Reference Station ◽

Full Potential ◽

Vapor Density ◽

Unknown Parameters

The spatio-temporal distribution of atmospheric water vapor information can be obtained by global positioning system (GPS) water vapor tomography. GPS signal rays pass through the tomographic area from different boundaries because the scope of the research region (latitude, longitude, and altitude) is designated in the process of tomographic modeling, the influence of the geographic distribution of receivers, and the geometric location of satellite constellations. Traditionally, only signal rays penetrating the entire tomographic area are considered in the computation of water vapor information, whereas those passing through the sides are neglected. Therefore, the accuracy of the tomographic result, especially at the bottom of the area, does not reach its full potential. To solve this problem, this paper proposes a new method that simultaneously considers the discretized tomographic voxels and the troposphere outside the research area as unknown parameters. This method can effectively improve the utilization of existing GPS observations and increase the number of voxels crossed by satellite signals, especially by increasing the proportion of voxels penetrated. A tomographic experiment is implemented using GPS data from the Hong Kong Satellite Positioning Reference Station Network. Compared to the traditional method, the proposed method increases the number of voxels crossed by signal rays and the utilization of the observed data by 15.14% and 19.68% on average, respectively. Numerical results, including comparisons of slant water vapor (SWV), precipitable water vapor (PWV), and water vapor density profile, show that the proposed method is better than traditional methods. In comparison to the water vapor density profile, the root-mean-square error (RMS), mean absolute error (MAE), standard deviation (SD), and bias of the proposed method are 1.39, 1.07, 1.30, and −0.21 gm−3, respectively. For the SWV and PWV comparison, the RMS/MAE of the proposed method are 10.46/8.17 mm and 4.00/3.39 mm, respectively.

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A new tropospheric tomography model combining the pixel-based and function-based models

10.5194/angeo-2018-34 ◽

2018 ◽

Cited By ~ 1

Author(s):

Yibin Yao ◽

Linyang Xin ◽

Qingzhi Zhao

Keyword(s):

Water Vapor ◽

Three Dimensional ◽

Global Navigation Satellite Systems ◽

Reference Station ◽

Continuous Change ◽

Vapor Density ◽

Spatial Continuity ◽

New Model ◽

Model Combining ◽

And Function

Abstract. As a new detection method of three-dimensional water vapor, the ground-based water vapor tomography technique using Global Navigation Satellite Systems (GNSS) observations can obtain the high spatial and temporal distribution information of tropospheric water vapor. Since the troposphere tomography was proposed, most previous studies belong to the pixel-based method, dividing the interest area into three-dimensional voxels of which the water vapor density of each voxel center is taken as the average water vapor density. However, the abovementioned method can only find the water vapor density value of the center of each voxel, which is unable to express the continuous change of water vapor in space and destroys the spatial continuity of water vapor variation. Moreover, when using the pixel-based method, too many voxels are needed to express the water vapor density, which leads to the problem of too many coefficients to be estimated. After analyzing the limitations of the traditional pixel-based troposphere tomography technique, this paper proposes a new GNSS tropospheric water vapor tomography model combining the pixel-based and function-based models for the first time. The tomographic experiences were validated using the data from 12 stations from the Hong Kong Satellite Positioning Reference Station Network (SatRef) collected between 25 March and 25 April 2014. The comparison between tomographic results and the European Centre for Medium-Range Weather Forecasts (ECMWF) data is mainly used to analyze the accuracy of the new model proposed in this paper under different conditions, for showing that this new model is superior to the traditional pixel-based model in terms of root-mean-square error (RMSE) and bias. The new model has more advantages than the traditional pixel-based model on the RMSE, especially when obtaining the water vapor in voxels without the penetration of GNSS rays, which is improved by 5.88 %. This model also solves the problem with more ease and convenience in expression.

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Airborne lidar observations of wind, water vapor, and aerosol profiles during the NASA Aeolus calibration and validation (Cal/Val) test flight campaign

Atmospheric Measurement Techniques ◽

10.5194/amt-14-4305-2021 ◽

2021 ◽

Vol 14 (6) ◽

pp. 4305-4334

Author(s):

Kristopher M. Bedka ◽

Amin R. Nehrir ◽

Michael Kavaya ◽

Rory Barton-Grimley ◽

Mark Beaubien ◽

...

Keyword(s):

Remote Sensing ◽

Optical Properties ◽

Water Vapor ◽

European Space Agency ◽

Airborne Lidar ◽

Horizontal Wind ◽

Atmospheric Conditions ◽

Spatiotemporal Resolution ◽

Wide Range ◽

Test Flight

Abstract. Lidars are uniquely capable of collecting high-precision and high spatiotemporal resolution observations that have been used for atmospheric process studies from the ground, aircraft, and space for many years. The Aeolus mission, the first space-borne Doppler wind lidar, was developed by the European Space Agency (ESA) and launched in August 2018. Its novel Atmospheric LAser Doppler INstrument (ALADIN) observes profiles of the component of the wind vector and aerosol/cloud optical properties along the instrument's line-of-sight (LOS) direction on a global scale. A total of two airborne lidar systems have been developed at NASA Langley Research Center in recent years that collect measurements in support of several NASA Earth Science Division focus areas. The coherent Doppler Aerosol WiNd (DAWN) lidar measures vertical profiles of LOS velocity along selected azimuth angles that are combined to derive profiles of horizontal wind speed and direction. The High Altitude Lidar Observatory (HALO) measures high resolution profiles of atmospheric water vapor (WV) and aerosol and cloud optical properties. Because there are limitations in terms of spatial and vertical detail and measurement precision that can be accomplished from space, airborne remote sensing observations like those from DAWN and HALO are required to fill these observational gaps and to calibrate and validate space-borne measurements. Over a 2-week period in April 2019, during their Aeolus Cal/Val Test Flight campaign, NASA conducted five research flights over the eastern Pacific Ocean with the DC-8 aircraft. The purpose was to demonstrate the following: (1) DAWN and HALO measurement capabilities across a range of atmospheric conditions, (2) Aeolus Cal/Val flight strategies and comparisons of DAWN and HALO measurements with Aeolus, to gain an initial perspective of Aeolus performance, and (3) ways in which atmospheric dynamic processes can be resolved and better understood through simultaneous observations of wind, WV, and aerosol profile observations, coupled with numerical model and other remote sensing observations. This paper provides a brief description of the DAWN and HALO instruments, discusses the synergistic observations collected across a wide range of atmospheric conditions sampled during the DC-8 flights, and gives a brief summary of the validation of DAWN, HALO, and Aeolus observations and comparisons.

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New Energy Balance, New Atmospheric Circulation and New Water Cycle in Western Mediterranean

10.5194/egusphere-egu2020-371 ◽

2020 ◽

Author(s):

Mohammed-Said Karrouk

Keyword(s):

Water Vapor ◽

Energy Balance ◽

Atmospheric Circulation ◽

Water Cycle ◽

Weather Conditions ◽

Western Mediterranean ◽

Energy Concentration ◽

Ocean Energy ◽

Thermal Distribution ◽

New Energy

The increase in the Earth's energy balance, due to the surplus of anthropogenic greenhouse gases, has created a warmer earth-based climate regime, widening the excess tropic zone to the poles. The characteristics and rhythms of this climate become unusual, with extreme weather conditions: more frequent heat and cold waves, strong gusts of wind, more severe droughts, and more frequent floods. This is the terrestrial "New Climate".This situation is characterized by a new thermal distribution: above the ocean, the situation is more in surplus energetic budget, and the land - atmosphere is negative. Warm thermal advection easily reach the Pole, as well as cold advection push deep into Western Mediterranean.This "New Ground Energy Balance" establishes an atmospheric circulation with an waving character throughout the year, including in winter, characterized by intense energy exchanges latitudinal very active between the surplus and deficit areas on the one hand, and the atmosphere, the ocean and the continent of the other.The new thermal distribution reorganizes the geography of atmospheric pressure: the ocean energy concentration is transmitted directly to the atmosphere, and the excess torque is pushed northward. The Azores anticyclone is strengthened and is a global lock by the Atlantic ridge at Greenland, which imposes on the jet stream a positive ripple, very strongly marked poleward, bringing cosmic cold advection of polar air masses winter over from Europe to Western Mediterranean. Hence the enormous meridian heat exchanges north-south-north. This is the "New" Meridian Atmospheric Circulation (MAC).This situation increases the potential evaporation of the atmosphere and provides a new geographical distribution of Moisture: the excess water vapor is easily converted by cold advection to heavy rains that cause floods or snow storms.Thus, the "New Energy Balance" creates a "New" Meridian-dominated Atmospheric Circulation, which induces excess atmospheric water vapor due to the increase in temperature. Since the hydro-atmospheric capacity has increased, the return to the ground is abundant: It is the "New Water Cycle", which accompanies the &#8220;New Energy Balance&#8221; of the Earth.

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Influence of Meteorological Conditions and Aerosol Properties on the COVID-19 Contamination of the Population in Coastal and Continental Areas in France: Study of Offshore and Onshore Winds

Atmosphere ◽

10.3390/atmos12040523 ◽

2021 ◽

Vol 12 (4) ◽

pp. 523

Author(s):

Jacques Piazzola ◽

William Bruch ◽

Christelle Desnues ◽

Philippe Parent ◽

Christophe Yohia ◽

...

Keyword(s):

Atmospheric Transport ◽

Weather Conditions ◽

Meteorological Conditions ◽

Sea Spray ◽

Atmospheric Conditions ◽

Virus Transport ◽

Virus Propagation ◽

Viral Particles ◽

The Social ◽

Aerosol Properties

Human behaviors probably represent the most important causes of the SARS-Cov-2 virus propagation. However, the role of virus transport by aerosols—and therefore the influence of atmospheric conditions (temperature, humidity, type and concentration of aerosols)—on the spread of the epidemic remains an open and still debated question. This work aims to study whether or not the meteorological conditions related to the different aerosol properties in continental and coastal urbanized areas might influence the atmospheric transport of the SARS-Cov-2 virus. Our analysis focuses on the lockdown period to reduce the differences in the social behavior and highlight those of the weather conditions. As an example, we investigated the contamination cases during March 2020 in two specific French areas located in both continental and coastal areas with regard to the meteorological conditions and the corresponding aerosol properties, the optical depth (AOD) and the Angstrom exponent provided by the AERONET network. The results show that the analysis of aerosol ground-based data can be of interest to assess a virus survey. We found that moderate to strong onshore winds occurring in coastal regions and inducing humid environment and large sea-spray production episodes coincides with smaller COVID-19 contamination rates. We assume that the coagulation of SARS-Cov-2 viral particles with hygroscopic salty sea-spray aerosols might tend to inhibit its viral infectivity via possible reaction with NaCl, especially in high relative humidity environments typical of maritime sites.

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

Remote Sensing ◽

10.3390/rs12071170 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1170 ◽

Cited By ~ 3

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.

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The influence of weather conditions on mid-field ponds situated in a reclaimed area in Sępopolska Plain

Oceanological and Hydrobiological Studies ◽

10.2478/v10009-010-0002-z ◽

2010 ◽

Vol 39 (1) ◽

Cited By ~ 1

Author(s):

Ireneusz Cymes ◽

Iwona Cymes ◽

Ewa Dragańska ◽

Sławomir Szymczyk

Keyword(s):

Weather Conditions ◽

Negative Influence ◽

Ammonium Nitrogen ◽

Water Evaporation ◽

Atmospheric Conditions ◽

Natural Reservoir ◽

Quality Of Water ◽

Water Ph ◽

Chlorine Ions ◽

Agricultural Areas

The influence of weather conditions on mid-field ponds situated in a reclaimed area in Sępopolska PlainThe investigations were conducted in northeastern Poland near Lidzbark Warmiński (54° 08" N, 20° 36" E). Five mid-field ponds situated on grasslands were chosen: four of them were dredged and deepened, and one of them remained as a natural reservoir. The aim of this paper was to assess the influence of weather conditions on the quantity and quality of water in mid-field ponds situated in agricultural areas. It was found that the quantity of water in mid-field ponds was related much more to the air temperature, which was responsible for either water evaporation or snow melting, rather than to the amount of precipitation. The reduction in the volume of water stored in the ponds during very dry years had a negative influence on its quality. During the observation period, the dredged ponds were characterized by permanent water tables, whereas the natural reservoir dried out in very dry years. Atmospheric conditions influenced the concentrations of ammonium nitrogen and calcium and chlorine ions in the studied water bodies. The volume of water retained in mid-field ponds influenced the concentrations of phosphorus and sulphates. Increased precipitation sums caused lower water pH; however in warmer periods, at increased pH and COD

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Uncertainties of ground-based microwave radiometer retrievals in zenith and off-zenith observations under snow conditions

Atmospheric Measurement Techniques ◽

10.5194/amt-10-155-2017 ◽

2017 ◽

Vol 10 (1) ◽

pp. 155-165 ◽

Cited By ~ 1

Author(s):

Wengang Zhang ◽

Guirong Xu ◽

Yuanyuan Liu ◽

Guopao Yan ◽

Dejun Li ◽

...

Keyword(s):

Relative Humidity ◽

Microwave Radiometer ◽

Retrieval Algorithm ◽

Mean Square ◽

Atmospheric Conditions ◽

Vapor Density ◽

Heavy Snowfall ◽

Snow Conditions ◽

The Impact ◽

Mean Square Errors

Abstract. This paper is to investigate the uncertainties of microwave radiometer (MWR) retrievals in snow conditions and also explore the discrepancies of MWR retrievals in zenith and off-zenith observations. The MWR retrievals were averaged in a ±15 min period centered at sounding times of 00:00 and 12:00 UTC and compared with radiosonde observations (RAOBs). In general, the MWR retrievals have a better correlation with RAOB profiles in off-zenith observations than in zenith observations, and the biases (MWR observations minus RAOBs) and root mean square errors (RMSEs) between MWR and RAOB are also clearly reduced in off-zenith observations. The biases of temperature, relative humidity, and vapor density decrease from 4.6 K, 9 %, and 1.43 g m−3 in zenith observations to −0.6 K, −2 %, and 0.10 g m−3 in off-zenith observations, respectively. The discrepancies between MWR retrievals and RAOB profiles by altitude present the same situation. Cases studies show that the impact of snow on accuracies of MWR retrievals is more serious in heavy snowfall than in light snowfall, but off-zenith observation can mitigate the impact of snowfall. The MWR measurements become less accurate in snowfall mainly due to the retrieval algorithm, which does not consider the effect of snow, and the accumulated snow on the top of the radome increases the signal noise of MWR measurements. As the snowfall drops away by gravity on the sides of the radome, the off-zenith observations are more representative of the atmospheric conditions for RAOBs.

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