TroWav Algorithm

The paper studies some determination peculiarities o f atmospheric propagation delay by the microwave-and laser distance measurements in polar regions. On the basis o f the average monthly and separate (one-time) aerological sounding data at a number o f Antarctic and Arctic stations the distribution analysis ofthe main meteorological parameters as well as o f refr activity both in space and in time is adduced. Zenith atmospheric delay fo r microwave-and laser range was estimated by the data o f these stations. A small effect o f moist component (zenith wet delay) in the Central Antarctica is noted. The values o f dry and wet components o f the zenith tropospheric delay obtained by radiosonde data and Saastamoinen and H opfield' s analytical models are cited.

The paper outlines both author’s independent research and joint, with other scientists, studies of atmospheric influences on the results of angular and electronic distance measurements in polar regions and, in particular, in Antarctica. A short description of structure peculiarities of atmospheric boundary layer is given. A special attention was given to thermal stratification and caused by it influences on the results of astrogeodetic measurements. Investigation of astronomic refraction was conducted on the basis of aerological data. An integral of refraction was computed at different zenith angles for several Antarctic and Arctic stations. Refractive anomalies were calculated by means of refraction tables. The results of the theoretical and experimental investigations of the terrestrial vertical refraction in polar regions are given. Analysis of atmospheric influences on the electronic distance measurements were carried out by means of the refraction index calculation for light-an...

With a view to difficulties with explaining the physical mechanism of solar forcing on the Earth's climate, we applied a new approach of determining and quantifying an influence of solar-related events on water vapor variability by correlating the total electron content (TEC) and precipitable water vapor (PWV), both derived from ground-based GPS observations. In this study, ionospheric TEC and atmospheric PWV values are employed as solar activity and terrestrial climate parameters, respectively. Three-year GPS data at five stations in Antarctica are analyzed on a daily mean basis. Results show significant correlation between TEC and PWV differences during storms-affected days. The high correlation between the daily mean values of TEC and PWV, both of which follow the seasonal signals and subsisting downward trend, suggests an influence of solar activity on climate variability in Antarctica. These quantities are determined by changes of the upper-atmosphere level, which varies in conformity with the zenith angle of the Sun.

Real-time national Global Positioning System (GPS) networks are being established in a number of countries for atmospheric sensing. UCAR, in collaboration with participating universities, is developing one of these networks in the United States. The network, named "SuomiNet" to honor meteorological satellite pioneer Verner Suomi, is funded by the U.S. National Science Foundation. SuomiNet will exploit the recently-shown ability of groundbased GPS receivers to make thousands of accurate upper and lower atmospheric measurements per day. Phase delays induced in GPS signals by the ionosphere and neutral atmosphere can be measured with high precision simultaneously along up to a dozen GPS ray paths in the field of view. These delays can be converted into total electron content (TEC), and integrated water vapor (if surface pressure data or estimates are available), along each GPS ray path. The resulting continuous, accurate, all-weather, real-time upper and lower atmospheric data create a variety of opportunities for atmospheric research. In this letter we describe SuomiNet, its applications, and the opportunity to coordinate national real-time GPS networks to create a global network with larger scientific and operational potential.

This short-term work characterized the upper and lower levels of the atmosphere through Global Positioning System (GPS) measurements. The observations were conducted during the 2009 equinoxes from two pairs of conjugate polar observing stations: Husafell, Iceland (HUSA) and Resolute in Nunavut, Canada (RESO) and their conjugate pairs at Scott Base (SBA) and Syowa (SYOG) in Antarctica, respectively. The total electron content (TEC), an indicator of the upper atmosphere, and the precipitable water vapor (PWV), which served as the lower atmospheric response, were retrieved and analyzed. The results reveal a good relationship between TEC and PWV at each station during the onset day of the equinoxes, whereas an asymmetrical response was observed in the beginning of and after the equinoxes. In addition, the conjugate pairs were only consistent during the autumnal equinox. Thus, the high correlation was observed following the seasonal pattern for the onset day, while strong and moderate co...

The effect of El Niño and La Niña events is a major issue in the regional climate of Southeast Asia. This study uses the Precipitable Water Vapor (PWV) values estimated from Global Navigation Satellite System (GNSS; in particular Global Positioning System, GPS) to investigate the El Niño-Southern Oscillation (ENSO) activity in the Southern coast of the South China Sea (SCS). For this study, GPS and meteorological systems are installed at the Universiti Malaysia Sabah, Kota Kinabalu (UMSK), which is located on the coast of the maritime continent. Subsequently, PWV from GPS and PWV obtained from Radiosonde, prior to the investigation of ENSO activity, are compared. To further investigate the relationship between PWV and ENSO activities, data from three additional GPS stations located along the coast of SCS during the 3-year period 2009-2011 were analyzed. The selection period considers the availability of GPS data. The obtained results show that during the increased intensity of El Niño in 2009/2010, PWV decreases and drops about 10-week later, i.e., after the sea surface temperature anomaly (SSTa) has peaked. PWV has a negative correlation with the El Niño index, which is comparable with precipitation data obtained from NASA's Tropical Rainfall Measuring Mission (TRMM). In contrast, the amount of PWV was increased during the La Niña event of 2010/2011. This observation suggests the GPS is a suitable technique for studying the ENSO activity.

Adaptive neuro-fuzzy inference system (ANFIS) is a prospective approach in modeling weather parameters based on learning from historical data used. This study presented the comparison of tropospheric precipitable water vapor (PWV) between ANFIS and Global Positioning System (GPS) for areas in Pekan, Pahang, Malaysia. The PWV value was estimated with the ANFIS model with the surface meteorological data as inputs. The accuracy of PWV from ANFIS has been validated with PWV from GPS measurements for the period of 2010. The result showed that the ANFIS PWV has a similar trend with the GPS PWV (r = 0.999 at the 99% confidence level) and found a difference of 0.024%. The PWV from ANFIS was calculated 0.035% higher compared to GPS PWV and found a similar character in two seasonal monsoons. This indicates that the PWV obtained with ANFIS model agreed very well with GPS measurements and it can be implemented to monitor atmospheric variability as well as climate change studies in the absence o...

One aspect of severe storms that can be monitored is lightning activity. There is no established and accurate model to predict the lightning occurrence and to explain their comprehensive physical mechanisms. This paper aim to monitor the lightning activity associated with water vapor changes to form convective cloud from evaporation due to solar heating. Water vapor content in term of precipitable water vapor (PWV) derived from GPS signals and the surface meteorological data is used to strengthen the GPS signals affected by the lightning. Data on November 2009 coincided with the winter monsoon (northeast monsoon) are selected, which possibly had a lot of rainfall with a high number of lightning activity. The lightning occurrence is recorded by the Surveillance et Alerte Foudre par Interférometrie Radioélectrique (SAFIR). The area for the first study is centered at radius 20 km from UKM GPS station located in Bangi, Malaysia. Results showed that major lightning activity was recorded 12 days during that month and 81% of total sample was correlated with PWV changes before the first strike, and is consistent with an increase in PWV. In most cases in that region found that the lightning activity is frequent in the afternoon between 13:00 and 18:00 local time, which preceded by PWV increase of about 5 mm. The finding suggests that the GPS data can be utilized further as a guide to predict the occurrence of lightning.

"SuomiNet," a university-based, real-time, national Global Positioning System (GPS) network, is being developed for atmospheric research and education with funding from the National Science Foundation and with cost share from collaborating universities. The network, named to honor meteorological satellite pioneer Verner Suomi, will exploit the recently shown ability of ground-based GPS receivers to make thousands of accurate upper-and lower-atmospheric measurements per day. Phase delays induced in GPS signals by the ionosphere and neutral atmosphere can be measured with high precision simultaneously along a dozen or so GPS ray paths in the field of view. These delays can be converted into integrated water vapor (if surface pressure data or estimates are available) and total electron content (TEC), along each GPS ray path. The resulting continuous, accurate, all-weather, real-time GPS moisture data will help advance university research in mesoscale modeling and data assimilation, severe weather, precipitation, cloud dynamics, regional climate, and hydrology. Similarly, continuous, accurate, all-weather, real-time TEC data have applications in modeling and prediction of severe terrestrial and space weather, detection and forecasting of low-altitude ionospheric scintillation activity and geomagnetic storm effects at ionospheric midlatitudes, and detection of ionospheric effects induced by a variety of geophysical events. SuomiNet data also have potential applications in coastal meteorology, providing ground truth for satellite radiometry, and detection of scintillation associated with atmospheric turbulence in the lower troposphere. The goal of SuomiNet is to make large amounts of spatially and temporally dense GPS-sensed atmospheric data widely available in real time, for academic research and education. Information on participation in SuomiNet is available via www.unidata.ucar.edu/suominet.

The extreme climate conditions and the sparse number of research stations in Antarctica limit the number of meteorological records over this area. Satellite radiometric measurements and ground-based GPS measurements can therefore improve the amount of available water vapour information. Combining the Zenith Total Delay (ZTD) time series from 6 Antarctic GPS stations and surface meteorological data, we have determined Precipitable Water Vapour (PW) variations with a 2-hour temporal resolution for a period of 5 years. Data from the Advanced Microwave Sounding Unit (AMSU-B) on board the NOAA-15 satellite cover most parts of Antarctica but with observations limited to merely few times a day. GPS and AMSU-B data sets are therefore complementary with respect to time and space. We present a cross validation between PW results from the two independent retrieval algorithms using one year data. Additionally, we compare the observed PW from AMSU-B and GPS with the National Centre for Environmental Prediction (NCEP) reanalysis. All three data sets are highly correlated. The mean differences between the three data sets are station dependent and vary from À1.7 to þ1.2 mm. A large part of the bias may result from pressure uncertainties affecting the GPS PW estimates. GPS and AMSU-B as independent data sources are confirmed to be accurate methods for PW estimation for the dry Antarctic atmosphere. PW results from the NCEP analysis corresponds, in general, well to the PW observations at the investigated stations along the Antarctic coast. The results obtained at the station O'Higgins differ from those of the other station. O'Higgins is located at the Antarctic Peninsula and has a more humid environment than the coast of the main Antarctic continent, which may explain the peculiar behaviour of this station.

The total mass of columnar water vapour (precipitable water, W) is an important parameter of atmospheric thermodynamic and radiative models. In this work more than 60 000 radiosonde observations from 17 aerological stations in the Baltic region over 14 years, 1989-2002, were used to examine the variability of precipitable water. A table of monthly and annual means of W for the stations is given. Seasonal means of W are expressed as linear functions of the geographical latitude degree. A linear formula is also derived for parametrisation of precipitable water as a function of two parameters-geographical latitude and surface water vapour pressure.

SuomiNet," a university-based, real-time, national Global Positioning System (GPS) network, is being developed for atmospheric research and education with funding from the National Science Foundation and with cost share from collaborating universities. The network, named to honor meteorological satellite pioneer Verner Suomi, will exploit the recently shown ability of ground-based GPS receivers to make thousands of accurate upper-and lower-atmospheric measurements per day. Phase delays induced in GPS signals by the ionosphere and neutral atmosphere can be measured with high precision simultaneously along a dozen or so GPS ray paths in the field of view. These delays can be converted into integrated water vapor (if surface pressure data or estimates are available) and total electron content (TEC), along each GPS ray path. The resulting continuous, accurate, all-weather, real-time GPS moisture data will help advance university research in mesoscale modeling and data assimilation, severe weather, precipitation, cloud dynamics, regional climate, and hydrology. Similarly, continuous, accurate, all-weather, real-time TEC data have applications in modeling and prediction of severe terrestrial and space weather, detection and forecasting of low-altitude ionospheric scintillation activity and geomagnetic storm effects at ionospheric midlatitudes, and detection of ionospheric effects induced by a variety of geophysical events. SuomiNet data also have potential applications in coastal meteorology, providing ground truth for satellite radiometry, and detection of scintillation associated with atmospheric turbulence in the lower troposphere. The goal of SuomiNet is to make large amounts of spatially and temporally dense GPS-sensed atmospheric data widely available in real time, for academic research and education. Information on participation in SuomiNet is available via www.unidata.ucar.edu/suominet.

The accuracy of Global Navigation Satellite System (GNSS), aimed to support precise positioning for aircraft navigation globally by coordinating different regional augmentation systems, is limited by the extent to which the atmospheric propagation delay of microwave signals can be ...

The effect of El Niño and La Niña events is a major issue in the regional climate of Southeast Asia. This study uses the Precipitable Water Vapor (PWV) values estimated from Global Navigation Satellite System (GNSS; in particular Global Positioning System, GPS) to investigate the El Niño-Southern Oscillation (ENSO) activity in the Southern coast of the South China Sea (SCS). For this study, GPS and meteorological systems are installed at the Universiti Malaysia Sabah, Kota Kinabalu (UMSK), which is located on the coast of the maritime continent. Subsequently, PWV from GPS and PWV obtained from Radiosonde, prior to the investigation of ENSO activity, are compared. To further investigate the relationship between PWV and ENSO activities, data from three additional GPS stations located along the coast of SCS during the 3-year period 2009-2011 were analyzed. The selection period considers the availability of GPS data. The obtained results show that during the increased intensity of El Niño in 2009/2010, PWV decreases and drops about 10-week later, i.e., after the sea surface temperature anomaly (SSTa) has peaked. PWV has a negative correlation with the El Niño index, which is comparable with precipitation data obtained from NASA's Tropical Rainfall Measuring Mission (TRMM). In contrast, the amount of PWV was increased during the La Niña event of 2010/2011. This observation suggests the GPS is a suitable technique for studying the ENSO activity.

Candidate sites of the future European Extremely Large Telescopes (E-ELT) need to be assessed and analytically compared in their observing characteristics. In the site selection process, meteorological, photometric and seeing qualities have to be studied and measured carefully. Aklim site in Morocco is one among four candidates in the ELT project. In this paper, we present meteorological studies of the Aklim site over eleven years. The meteorological parameters include wind speed and direction, relative humidity, air temperature, cloud cover and water vapour content. Most of these data are taken from the National Center for Environmental Prediction/National Center for Atmospheric Research NCEP/NCAR Reanalysis. The meteorological analysis covers the vertical profile as well as surface layer meteorology. Furthermore, in extensive literature, it has been demonstrated that the global circulation of atmospheric wind at 200 mb can be used as a criterion to establish the suitability for the development of adaptive optics techniques. By using the NOAA NCEP/NCAR reanalysis database, we analyse the monthly average wind velocity at 200 mb for eleven years period and compare with famous observatories.

Real-time national Global Positioning System (GPS) networks are being established in a number of countries for atmospheric sensing. UCAR, in collaboration with participating universities, is developing one of these networks in the United States. The network, named "SuomiNet" to honor meteorological satellite pioneer Verner Suomi, is funded by the U.S. National Science Foundation. SuomiNet will exploit the recently-shown ability of groundbased GPS receivers to make thousands of accurate upper and lower atmospheric measurements per day. Phase delays induced in GPS signals by the ionosphere and neutral atmosphere can be measured with high precision simultaneously along up to a dozen GPS ray paths in the field of view. These delays can be converted into total electron content (TEC), and integrated water vapor (if surface pressure data or estimates are available), along each GPS ray path. The resulting continuous, accurate, all-weather, real-time upper and lower atmospheric data create a variety of opportunities for atmospheric research. In this letter we describe SuomiNet, its applications, and the opportunity to coordinate national real-time GPS networks to create a global network with larger scientific and operational potential.

Real-time national global positioning system (GPS) networks are being established in a number of countries for atmospheric sensing. The authors, in collaboration with participating universities, are developing one of these networks in the United States. The proposed network, named "SuomiNet" to honor meteorological satellite pioneer Verner Suomi, is funded by the US National Science Foundation to exploit the recently shown ability of ground-based GPS receivers to make thousands of accurate upper and lower atmospheric measurements per day. Phase delays induced in GPS signals by the ionosphere and neutral atmosphere can be measured with high precision simultaneously along a dozen or so GPS ray paths in the ÿeld of view. These delays can be converted into integrated water-vapor (if surface pressure data or estimates are available) and total electron content (TEC), along each GPS ray path. The resulting continuous, accurate, all-weather, real-time GPS moisture data will help advance university research in mesoscale modeling and data assimilation, severe weather, precipitation, cloud dynamics, regional climate and hydrology. Similarly, continuous, accurate, all-weather, real-time TEC data have applications in modeling and prediction of severe terrestrial and space weather, detection and forecasting of low-latitude ionospheric scintillation activity and geomagnetic storm e ects at ionospheric mid-latitudes, and detection of ionospheric e ects induced by a variety of geophysical events. SuomiNet data also have potential applications in coastal meteorology, providing ground truth for satellite radiometry, correction of synthetic aperture radar data for crustal deformation and topography studies, and detection of scintillation associated with atmospheric turbulence in the lower troposphere. In this paper we describe SuomiNet, its applications, and the larger opportunity to coordinate national real-time GPS networks to maximize their scientiÿc and operational impact.

We describe sensing of atmospheric column water min. The Yellowstone site transmits GPS data to Boulder every 30 vapor in near real-time using the Global Positioning System sec via satellite link. This site is operated primarily to monitor (GPS). We use predicted GPS orbits for automated computation of geodetic deformation of the volcanic caldera and does not provide vertical column water vapor within 30 minutes of GPS data col-surface meteorological data. lecfion. Based on a 4 month comparison, near real-time GPS col-The real-time GPS network extends more than 1,500 km from umn water vapor agrees with radiosondes and radiometers within the Mississippi Gulf coast to Yellowstone. A network of this size 2 mm rms. Our near real-time column water vapor data are posted hourly at www. unavco. ucar. edu. They are available for assimilation in numerical weather models and for other applications. sonde and radiometer measurements. Data collection Near real-time GPS tracking data are obtained from a 16 station network in the central U.S. (Figure 1). Fifteen of the stations are operated by FSL [Gutman et al., 1994], most of them located at wind profiling (radar) sites. One station is operated in Yellowstone National Park, Wyoming, by the University of Utah. All stations use dual frequency Trimble TM SSE or SSI GPS receivers. The FSL sites transmit 30 sec GPS data, and 6 min surface meteorological data to the FSL data hub in Boulder, Colorado, every 30

"SuomiNet," a university-based, real-time, national Global Positioning System (GPS) network, is being developed for atmospheric research and education with funding from the National Science Foundation and with cost share from collaborating universities. The network, named to honor meteorological satellite pioneer Verner Suomi, will exploit the recently shown ability of ground-based GPS receivers to make thousands of accurate upper-and lower-atmospheric measurements per day. Phase delays induced in GPS signals by the ionosphere and neutral atmosphere can be measured with high precision simultaneously along a dozen or so GPS ray paths in the field of view. These delays can be converted into integrated water vapor (if surface pressure data or estimates are available) and total electron content (TEC), along each GPS ray path. The resulting continuous, accurate, all-weather, real-time GPS moisture data will help advance university research in mesoscale modeling and data assimilation, severe weather, precipitation, cloud dynamics, regional climate, and hydrology. Similarly, continuous, accurate, all-weather, real-time TEC data have applications in modeling and prediction of severe terrestrial and space weather, detection and forecasting of low-altitude ionospheric scintillation activity and geomagnetic storm effects at ionospheric midlatitudes, and detection of ionospheric effects induced by a variety of geophysical events. SuomiNet data also have potential applications in coastal meteorology, providing ground truth for satellite radiometry, and detection of scintillation associated with atmospheric turbulence in the lower troposphere. The goal of SuomiNet is to make large amounts of spatially and temporally dense GPS-sensed atmospheric data widely available in real time, for academic research and education. Information on participation in SuomiNet is available via www.unidata.ucar.edu/suominet.

Radiosonde is extensively used for understanding meteorological parameters in the vertical direction. Four typhoon events, including three landfalls (MERANTI, NEPARTAK, and MEGI) and one non-landfall (MALAKAS), were chosen in analysing the precipitable water vapour (PWV) characteristics in this study. The spatial distribution of the three radiosonde stations in Zhejiang province does not meet the requirement in analysing changes in PWV during typhoon event. Global position system (GPS) observations are an alternative method for deriving the PWV. This enables improvements in the temporal–spatial resolution of PWV computed by the radiosonde measurements. The National Centers for Environmental Prediction (NCEP) re-analysed data were employed for interpolating temperature and atmosphere pressure at the GPS antennas height. The PWV computed from GPS observations and NCEP re-analysed data were then compared with the true PWV. The maximum difference of radiosonde and GPS PWV was not more t...

Knowledge of the diurnal cycle of precipitable water vapor (PWV) is very limited due to the lack of data with sufficient temporal resolution. Currently, GPS receivers have proven to be a suitable technique to determine the PWV diurnal variations. In this study, the annual and seasonal diurnal cycles of PWV have been obtained from GPS data for ten locations over Spain. The minimum value of PWV is reached approximately at the same time at all the stations, ~0430-0530 UTC, whereas the maximum is reached in the second half of the day, but with a larger dispersion of its occurrence between stations. The annual sub-daily variability ranges from 0.41 to 1.35 mm (3-7%). The highest values are recorded at the stations on the Mediterranean coast, with a doubling of the values of the stations on the Atlantic coast or inland. The winter cycle is quite similar at all locations, whereas in summer, local effects are felt strongly, making the diurnal cycle quite different between stations. The PWV mean diurnal cycle is strongest in summer and weakest in spring, with a sub-daily variability of 1.34 and 0.66 mm respectively. Harmonic analysis shows that the first two harmonics can explain 97% of the variance. The diurnal (24h) harmonic explains 85% of the variance, has mean amplitude of 0.40 mm, and the peak time is from early afternoon to evening. The semidiurnal (12h) harmonic is weaker, with amplitude of 0.13 mm, and peak time between 0400-1000 UTC. The diurnal cycle of temperature alone would be a proxy for PWV cycle during the night, but not during daytime. The breeze regime is the main factor responsible for the phase lag between PWV and temperature cycles during daytime. No clear correlation between the daily cycle of precipitation and PWV has been found.

In this work, relatively cheap and easy to measure surface meteorological data such as ambient temperature, relative humidity, vapour pressure and dew-point temperature, had been collected from the Nigerian Meteorological Agency (NIMET). Using the analytically derivable Butler's equation, precipitable water vapour (PWV) had been estimated. For the purpose of this work, Nigeria was divided into four climatic regions and for each region empirical models of the form PWV (T) and PWV (RH) were found; where T was the surface dew-d d point temperature and RH the surface relative humidity. The empirical models found were validated against the NCEP-DOE Reanalysis II data and found to be useful in estimating precipitable water vapour.

The total mass of columnar water vapour (precipitable water, W) is an important parameter of atmospheric thermodynamic and radiative models. In this work more than 60 000 radiosonde observations from 17 aerological stations in the Baltic region over 14 years, 1989-2002, were used to examine the variability of precipitable water. A table of monthly and annual means of W for the stations is given. Seasonal means of W are expressed as linear functions of the geographical latitude degree. A linear formula is also derived for parametrisation of precipitable water as a function of two parameters-geographical latitude and surface water vapour pressure.

This paper monitors the influences of solar energetic events during the intense solar flares of October/November 2003 on precipitable water vapor (PWV) at Scott Base station, Antarctica for the period from 22 October to 7 November 2003. A PWV representing a climate variable to indicate the lower atmosphere has been responsive to the upper atmosphere is derived from the GPS signals and the surface meteorological data. The analysis results showed that the PWV and solar related events (EUV, proton and cosmic ray density) exhibited a strong relationship with regard a lag time of ~48 hours as preference time to observe the effects directly. PWV increased by about 0.15 mm observed during the Superstom, where EUV and solar protons increased ~24% and 16% respectively and the density of cosmic rays is decreased to 20%.

Sun-Earth coupling studies is one channel projections to explain certain physical mechanisms of how solar activity exerts their influences on severe weather or changes in global climate towards improved global forecast models and space weather prediction. Measurements of atmospheric precipitable water vapour (PWV) and the ionospheric total electron content (TEC) at Husafell, Arctic vantage point from satellite at L-band signals using the Global Positioning System (GPS) technology is addressed in this paper. In this study, the lower and upper atmosphere represented by PWV and TEC respectively, is employed as a climate and solar activity parameters to enlighten Sun-Earth connection. The diurnal variation of both PWV and TEC, and its possible connection to the solar activity during the September 2008 campaign are presented. Day-to-day changes both parameters and their diurnal cycle pattern measured in this region were clearly influenced by solar activity, indicates a reasonable couplin...

Klang Valley is a focal area of Malaysian economic and business activities where the local weather condition is very important to maintain its reputation. Heavy rainfall for more than an hour was reported for up to 40 and 35 mm in September and October 2013 respectively. Based on these cases, we investigated the water vapour, rainfall, surface meteorological data (surface pressure, relative humidity and temperature) and river water level. The precipitable water vapour (PWV) derived from Global Positioning System (GPS) was used to indicate the impact of the flash floods on the rainfall. We found that PWV dropped by 4 mm at 2 h before the rainfall reached 40 mm and dropped by 3 mm at 3 h before 35 mm of rainfall in the respective cases. The variation of PWV was higher for September as compared to October by about 2 mm. We suggest that rainfall phenomena can disturb GPS propagation and hence, the impact of PWV before, during and after the flash flood events at the three selected GPS st...

We analyzed the variability of global positioning system (GPS) water vapor during the 2011 La Niña events over the western Pacific Ocean. The precipitable water vapor (PWV) derived from the UMSK (Malaysia) GPS station was investigated and compared with four other selected GPS stations: NTUS (Singapore), PIMO (Philippines), BAKO (Indonesia) and TOW2 (Australia). Analysis of the correlation between PWV and the sea-surface temperature anomaly (SSTa) on a weekly basis for the three La Niña cases of January-February-March, August-September-October, and October-November-December was used as an indicator of the influence of the El Niño Southern Oscillation. A good relationship between GPS PWV and SSTa for the Niño 4 region, with correlation coefficients between-0.91 and-0.94, was observed for the August-September-October and October-November-December cases. During the 2011 La Niña events, the water vapor was seen to increase to about 8.39 mm for the October-November-December case, with decreases of about 4.20 mm for the remaining months, compared to the mean 2011 value. This implies that during these events, the precipitation in the western Pacific is increased, due to stronger easterly trade winds blowing along the eastern Pacific Ocean than along the western Pacific, and a mass of warm water moving westwards, thereby increasing the evaporation.

This paper presents the impact of La Niña events in Southeast Asian based on the precipitable water vapor (PWV) data derived from GPS measurements. Using GPS PWV data over the period of 2011 from 4 stations in Malaysia (UMSK), Singapore (NTUS), Philippines (PIMO) and Indonesia (BAKO), we quantify the correlation between PWV and the sea surface temperature anomaly (SSTa). Three cases of La Niña event has been detected. For the case of January-March, the GPS PWV and SSTa on a weekly basis observed low correlation at all stations. A moderate correlation was observed for the case of November-December. In contrast, a good relationship for PIMO and BAKO was found for the case of September, although the intensity of the event is low. From the data analysis, we can conclude that La Niña event had an impact to the Southeast Asia, primarily to the increase in atmospheric water vapor content, mainly at the end of 2011. This can lead to increase rainfall and potential risk of flooding and landslides occurred.

Real-time national global positioning system (GPS) networks are being established in a number of countries for atmospheric sensing. The authors, in collaboration with participating universities, are developing one of these networks in the United States. The proposed network, named "SuomiNet" to honor meteorological satellite pioneer Verner Suomi, is funded by the US National Science Foundation to exploit the recently shown ability of ground-based GPS receivers to make thousands of accurate upper and lower atmospheric measurements per day. Phase delays induced in GPS signals by the ionosphere and neutral atmosphere can be measured with high precision simultaneously along a dozen or so GPS ray paths in the ÿeld of view. These delays can be converted into integrated water-vapor (if surface pressure data or estimates are available) and total electron content (TEC), along each GPS ray path. The resulting continuous, accurate, all-weather, real-time GPS moisture data will help advance university research in mesoscale modeling and data assimilation, severe weather, precipitation, cloud dynamics, regional climate and hydrology. Similarly, continuous, accurate, all-weather, real-time TEC data have applications in modeling and prediction of severe terrestrial and space weather, detection and forecasting of low-latitude ionospheric scintillation activity and geomagnetic storm e ects at ionospheric mid-latitudes, and detection of ionospheric e ects induced by a variety of geophysical events. SuomiNet data also have potential applications in coastal meteorology, providing ground truth for satellite radiometry, correction of synthetic aperture radar data for crustal deformation and topography studies, and detection of scintillation associated with atmospheric turbulence in the lower troposphere. In this paper we describe SuomiNet, its applications, and the larger opportunity to coordinate national real-time GPS networks to maximize their scientiÿc and operational impact.

Global Positioning System (GPS) monitoring of Zenith Total Delay (ZTD) of the troposphere which is related to water vapor is important as it may help us in weather forecasting. The atmospheric water vapor varies according to the season and it also varies quickly on short temporal and spatial scales during stormy periods. Thus it plays a crucial role in meteorology. GPS is one of the relatively inexpensive tools available to monitor the water vapor content in the atmosphere. In the present study, the efficacy of GPS data to monitor perturbations in tropospheric water content (GPS meteorology) associated with atmospheric storms and depressions is investigated utilizing the data from a tropical region of India, recorded between 15 th October, 2010 and 27 th December, 2010 during which Southern India was affected by a few significant atmospheric events. The ZTD was estimated for this period at the NGRI operated GPS stations at Hyderabad (HYDE) and MS University, Tirunelveli (MSUN). The accuracy of GPS derived ZTD was validated from the close match 2 seen with ZTD values estimated from numerical weather modeling data. During the stormy periods there were strong variations of the ZTD. Corresponding changes in precipitable water vapor were estimated for the International GNSS Service station HYDE. The average ZTD was found to be higher near the coastal station at MSUN and less at the inland station HYDE. Most of the observed peaks in the ZTD time series were well correlated to the atmospheric events that influenced the region. The study extended to two more locations in the equatorial Indian Ocean region showed spatial variations in the ZTD values, which suggest the weakening of ZTD towards the coast. Our observations are yet another illustration for the application of GPS observations to monitor tropospheric water content variations associated with severe atmospheric events.

The total mass of columnar water vapour (precipitable water, W) is an important parameter of atmospheric thermodynamic and radiative models. In this work more than 60 000 radiosonde observations from 17 aerological stations in the Baltic region over 14 years, 1989-2002, were used to examine the variability of precipitable water. A table of monthly and annual means of W for the stations is given. Seasonal means of W are expressed as linear functions of the geographical latitude degree. A linear formula is also derived for parametrisation of precipitable water as a function of two parameters-geographical latitude and surface water vapour pressure.

The accuracy of surface meteorological measurements is vital to derive accurate Global Positioning System (GPS) Precipitable Water Vapour (PWV) data. However, in absence of surface meteorological data, data from Numerical Weather Prediction Models (NWP) are used. The accuracy of these models varies depending on the model, region, season and other climatic conditions. In this study, GPS data for derivation of PWV is collected from 13 geodetic permanent stations for the years 2013 to 2016. Five out of 13 GPS stations are equipped with meteorological sensors. The interpolated European Centre for Medium-Range Weather Forecasts (ECMWF) 5th Re-Analysis (ERA5) dataset at these locations is first validated using the meteorological data from these sensors. The assessment shows that the average root mean square errors (RMSE) of surface pressure and temperature values are about 0.72 hPa and 1.04 K respectively. PWV determined also requires information on the weighted mean temperature (T m); the T m at the 13 GPS stations was also evaluated using three methods: the temperature and humidity profiles from ERA5 (ERA5 T m), as well as the T m derived from Bevis and Yao T m-T s relationships. The T m derived from ERA5 was used as a reference to assess the errors of the Bevis and Yao T m. The comparisons show that the average RMSE values of T m derived from the two methods are 2.05 K and 2.02 K respectively. The GPS PWVs calculated using the ERA5 interpolated data (GPS ERA5 PWV) were compared to GPS PWV calculated using the sensor meteorological data (GPS MET PWV) at the 5 stations. The GPS ERA5 PWV values were used as the reference. The RMSE values of the two PWV datasets are in the range of 0.19 mm to 0.90 mm with overall average value of 0.44 mm. Also the computed ERA5 PWV data are compared to GPS ERA5 PWV at the 13 stations. ERA5 PWV values were used as the reference and the RMS errors of the two PWV values are in the range 1.35 mm to 2.25 mm with the overall average value of 1.66 mm. Regarding the seasonal variations, the stations between latitudes 4 S and 4 N and latitudes 12 S to 4 S have the highest PWV values in spring and summer while the lowest values occur in summer and winter respectively.

Problem statement: This study mainly discusses the possibility of PWV derived from GPS data for monitoring of water vapor changes during the severe flood due to heavy rainfall. There are two cases of heavy rainfall recorded during the winter monsoon in November 2009 at Kuala Krai, Kelantan. Approach: The first and second cases were sustained for 3 days from 4-6 November and 7 days from 18 until 24 November with recorded maximum daily rainfall more than 180 mm and 220 mm, respectively. However from the Malaysia Meteorology Department (MMD) report, only the second case was caused the severe flood. PWV and the surface meteorological data for both cases showed a significant response to the heavy rainfall. Results: During the severe flood, PWV was observed decreased of about 3.52 mm. Conclusion: We highlighted that the widespread and enormous cumulonimbus cloud cluster sheltered the area due to cold surge during the winter monsoon can cause the unnatural peak on PWV during the heavy rainfall.

Real-time national Global Positioning System (GPS) networks are being established in a number of countries for atmospheric sensing. UCAR, in collaboration with participating universities, is developing one of these networks in the United States. The network, named "SuomiNet" to honor meteorological satellite pioneer Verner Suomi, is funded by the U.S. National Science Foundation. SuomiNet will exploit the recently-shown ability of groundbased GPS receivers to make thousands of accurate upper and lower atmospheric measurements per day. Phase delays induced in GPS signals by the ionosphere and neutral atmosphere can be measured with high precision simultaneously along up to a dozen GPS ray paths in the field of view. These delays can be converted into total electron content (TEC), and integrated water vapor (if surface pressure data or estimates are available), along each GPS ray path. The resulting continuous, accurate, all-weather, real-time upper and lower atmospheric data create a variety of opportunities for atmospheric research. In this letter we describe SuomiNet, its applications, and the opportunity to coordinate national real-time GPS networks to create a global network with larger scientific and operational potential.

Real-time national global positioning system (GPS) networks are being established in a number of countries for atmospheric sensing. The authors, in collaboration with participating universities, are developing one of these networks in the United States. The proposed network, named "SuomiNet" to honor meteorological satellite pioneer Verner Suomi, is funded by the US National Science Foundation to exploit the recently shown ability of ground-based GPS receivers to make thousands of accurate upper and lower atmospheric measurements per day. Phase delays induced in GPS signals by the ionosphere and neutral atmosphere can be measured with high precision simultaneously along a dozen or so GPS ray paths in the ÿeld of view. These delays can be converted into integrated water-vapor (if surface pressure data or estimates are available) and total electron content (TEC), along each GPS ray path. The resulting continuous, accurate, all-weather, real-time GPS moisture data will help advance university research in mesoscale modeling and data assimilation, severe weather, precipitation, cloud dynamics, regional climate and hydrology. Similarly, continuous, accurate, all-weather, real-time TEC data have applications in modeling and prediction of severe terrestrial and space weather, detection and forecasting of low-latitude ionospheric scintillation activity and geomagnetic storm e ects at ionospheric mid-latitudes, and detection of ionospheric e ects induced by a variety of geophysical events. SuomiNet data also have potential applications in coastal meteorology, providing ground truth for satellite radiometry, correction of synthetic aperture radar data for crustal deformation and topography studies, and detection of scintillation associated with atmospheric turbulence in the lower troposphere. In this paper we describe SuomiNet, its applications, and the larger opportunity to coordinate national real-time GPS networks to maximize their scientiÿc and operational impact.

The present paper investigates precipitable water vapor (PWV) variations over the lower middle latitude Turkish region from the International GNSS Services (IGS) and Turkish Permanent GNSS Network (TPGN) observations. The diurnal, seasonal, annual, and rainfall time behavior of PWV and their relative deviations are presented covering the period from 2009 to 2017. Additionally, the predictions from Auto Regressive Moving Average (ARMA) model and ERA-Interim reanalysis datasets are analyzed to understand their effectiveness over the region. In the first observation, diurnal profile indicates maximum value of PWV over the ocean climate regions whereas minimum value is noticed over the semi-arid continental climate areas of Turkey. The seasonal maximum value of PWV is observed in June solstice followed by September equinox and the lowest value is seen in December solstice followed March equinox. The studies also cover annual variation, grand-mean of tropospheric PWV and PWV intensity from the TPGN confirming the range of PWV between 0 to 45 mm. The PWV time series during 2009 to 2017 exhibit a strong annual variation at all sites, with distinctive peaks and dips occurring approximately in summer and winter, respectively. The precipitation plots displayed a clear increasing pattern in summer but the values are less in winter. However, the annual relative deviation of PWV lies in the range of − 0.5 to 1.5 units for all stations. The highest grand-mean of PWV is registered in 2010 (~ 22 mm) whereas the lowest value is seen in 2011 (~ 11 mm). The spatial variation of PWV shows that the northern boundary of the Turkey, western part of the country and Northern Cyprus have higher magnitude of PWV while the other part of the country like Central and Eastern Turkey have the lower magnitudes of PWV. PWV analysis during the precipitation period reconfirms that the rainfall pattern is not necessary to follow the PWV time series due to interlinked atmospheric processes. However, we found the PWV predictability of ARMA model is relatively better than the ERA-Interim model. Comprehensive analysis of TPGN data over the region may complement towards a better understanding of the tropospheric dynamics, their effects and the future refinements of atmospheric models over the lower middle latitude Turkish region.

This paper presents observations of precipitable water vapor (PWV) from the Global Positioning System (GPS) signals and the surface meteorological measurements. Three stations in Antarctica that are Scott Base (SBA), Casey (CAS1), Macquarie Island (MAC1) and Syowa (SYOG) were taken as the location of observation. For analysis, the data gathered from January to December 2004 are analyzed. The PWV content for Antarctic region was obtained below 10 mm (on average) with an accuracy of 1~2 mm and its variability shows a U-profile pattern. Based on this accuracy, the PWV time series for Antarctic region can be predicted through the surface temperature measurements, which is cost effective, continuous and capable of climate monitoring.

One aspect of severe storms that can be monitored is lightning activity. There is no established and accurate model to predict the lightning occurrence and to explain their comprehensive physical mechanisms. This paper aim to monitor the lightning activity associated with water vapor changes to form convective cloud from evaporation due to solar heating. Water vapor content in term of precipitable water vapor (PWV) derived from GPS signals and the surface meteorological data is used to strengthen the GPS signals affected by the lightning. Data on November 2009 coincided with the winter monsoon (northeast monsoon) are selected, which possibly had a lot of rainfall with a high number of lightning activity. The lightning occurrence is recorded by the Surveillance et Alerte Foudre par Interférometrie Radioélectrique (SAFIR). The area for the first study is centered at radius 20 km from UKM GPS station located in Bangi, Malaysia. Results showed that major lightning activity was recorded ...

This paper presents the impact of La Niña events in Southeast Asian based on the precipitable water vapor (PWV) data derived from GPS measurements. Using GPS PWV data over the period of 2011 from four selected stations in Malaysia (UMSK), Singapore (NTUS), Philippines (PIMO) and Indonesia (BAKO), we quantify the correlation between PWV and the sea surface temperature anomaly (SSTa). Three cases of La Niña event has been detected. For the case of January-March, the GPS PWV and SSTa on a weekly basis observed with low correlation at all stations. A moderate correlation was observed for the case of November-December. In contrast, a good relationship for PIMO and BAKO was found for the case of September. From the data analysis, we can conclude that La Niña event had an impact to the Southeast Asia, primarily to the increase in atmospheric water vapor content, mainly at the end of 2011. This can lead to increase the rainfall and potential risk of flooding and landslides.

Klang Valley is a focal area of Malaysian economic and business activities where the local weather condition is very important to maintain its reputation. Heavy rainfall for more than an hour was reported for up to 40 and 35 mm in September and October 2013 respectively. Based on these cases, we investigated the water vapour, rainfall, surface meteorological data (surface pressure, relative humidity and temperature) and river water level. The precipitable water vapour (PWV) derived from Global Positioning System (GPS) was used to indicate the impact of the flash floods on the rainfall. We found that PWV dropped by 4 mm at 2 h before the rainfall reached 40 mm and dropped by 3 mm at 3 h before 35 mm of rainfall in the respective cases. The variation of PWV was higher for September as compared to October by about 2 mm. We suggest that rainfall phenomena can disturb GPS propagation and hence, the impact of PWV before, during and after the flash flood events at the three selected GPS st...

We analyzed the variability of global positioning system (GPS) water vapor during the 2011 La Niña events over the western Pacific Ocean. The precipitable water vapor (PWV) derived from the UMSK (Malaysia) GPS station was investigated and compared with four other selected GPS stations: NTUS (Singapore), PIMO (Philippines), BAKO (Indonesia) and TOW2 (Australia)

This paper presents the impact of La Niña events in Southeast Asian based on the precipitable water vapor (PWV) data derived from GPS measurements. Using GPS PWV data over the period of 2011 from 4 stations in Malaysia (UMSK), Singapore (NTUS), Philippines (PIMO) and Indonesia (BAKO), we quantify the correlation between PWV and the sea surface temperature anomaly (SSTa). Three cases of La Niña event has been detected. For the case of January-March, the GPS PWV and SSTa on a weekly basis observed low correlation at all stations. A moderate correlation was observed for the case of November-December. In contrast, a good relationship for PIMO and BAKO was found for the case of September, although the intensity of the event is low. From the data analysis, we can conclude that La Niña event had an impact to the Southeast Asia, primarily to the increase in atmospheric water vapor content, mainly at the end of 2011. This can lead to increase rainfall and potential risk of flooding and landslides occurred.

Problem statement: This study mainly discusses the possibility of PWV derived from GPS data for monitoring of water vapor changes during the severe flood due to heavy rainfall. There are two cases of heavy rainfall recorded during the winter monsoon in November 2009 at Kuala Krai, Kelantan. Approach: The first and second cases were sustained for 3 days from 4-6 November and 7 days from 18 until 24 November with recorded maximum daily rainfall more than 180 mm and 220 mm, respectively. However from the Malaysia Meteorology Department (MMD) report, only the second case was caused the severe flood. PWV and the surface meteorological data for both cases showed a significant response to the heavy rainfall. Results: During the severe flood, PWV was observed decreased of about 3.52 mm. Conclusion: We highlighted that the widespread and enormous cumulonimbus cloud cluster sheltered the area due to cold surge during the winter monsoon can cause the unnatural peak on PWV during the heavy rainfall.