Atmospheric Precipitable Water Research Articles

Resolution and Dynamical Core Dependence of Atmospheric River Frequency in Global Model Simulations

Abstract This study examines the sensitivity of atmospheric river (AR) frequency simulated by a global model with different grid resolutions and dynamical cores. Analysis is performed on aquaplanet simulations using version 4 of the Community Atmosphere Model (CAM4) at 240-, 120-, 60-, and 30-km model resolutions, each with the Model for Prediction Across Scales (MPAS) and High-Order Methods Modeling Environment (HOMME) dynamical cores. The frequency of AR events decreases with model resolution and the HOMME dynamical core produces more AR events than MPAS. Comparing the frequencies determined using absolute and percentile thresholds of large-scale conditions used to define an AR, model sensitivity is found to be related to the overall sensitivity of subtropical westerlies, atmospheric precipitable water content and profile, and to a lesser extent extratropical Rossby wave activity to model resolution and dynamical core. Real-world simulations using MPAS at 120- and 30-km grid resolutions also exhibit a decrease of AR frequency with increasing resolution over the southern east Pacific, but the difference is smaller over the northern east Pacific. This interhemispheric difference is related to the enhancement of convection in the tropics with increased resolution. This anomalous convection sets off Rossby wave patterns that weaken the subtropical westerlies over the southern east Pacific but has relatively little effect on those over the northern east Pacific. In comparison to the NCEP-2 reanalysis, MPAS real-world simulations are found to underestimate AR frequencies at both resolutions likely because of their climatologically drier subtropics and poleward-shifted jets. This study highlights the important links between model climatology of large-scale conditions and extremes.

Meteorological applications of precipitable water vapor measurements retrieved by the national GNSS network of China

In this study, the Global Navigation Satellite System (GNSS) network of China is discussed, which can be used to monitor atmospheric precipitable water vapor (PWV). By the end of 2013, the network had 952 GNSS sites, including 260 belonging to the Crustal Movement Observation Network of China (CMONOC) and 692 belonging to the China Meteorological Administration GNSS network (CMAGN). Additionally, GNSS observation collecting and data processing procedures are presented and PWV data quality control methods are investigated. PWV levels as determined by GNSS and radiosonde are compared. The results show that GNSS estimates are generally in good agreement with measurements of radiosondes and water vapor radiometers (WVR). The PWV retrieved by the national GNSS network is used in weather forecasting, assimilation of data into numerical weather prediction models, the validation of PWV estimates by radiosonde, and plum rain monitoring. The network is also used to monitor the total ionospheric electron content.

Validation of the WRF model for PWV forecasting at the Roque de los Muchachos Observatory

The atmospheric Precipitable Water Vapour content (PWV) is crucial for astronomical observations in the infrared. In this work, we have validated the Weather Research and Forecasting (WRF) mesoscale numerical model as an operational tool for PWV at Roque de los Muchachos astronomical Observatory (ORM). We used radiosonde data obtained directly at the Observatory and at the sea level. An excellent agreement between PWV model forecasts and observations was found at both verification points with a correlation above 0.9.

Precipitable Water Vapor Estimates in the Australian Region from Ground-Based GPS Observations

We present a comparison of atmospheric precipitable water vapor (PWV) derived from ground-based global positioning system (GPS) receiver with traditional radiosonde measurement and very long baseline interferometry (VLBI) technique for a five-year period (2008–2012) using Australian GPS stations. These stations were selectively chosen to provide a representative regional distribution of sites while ensuring conventional meteorological observations were available. Good agreement of PWV estimates was found between GPS and VLBI comparison with a mean difference of less than 1 mm and standard deviation of 3.5 mm and a mean difference and standard deviation of 0.1 mm and 4.0 mm, respectively, between GPS and radiosonde measurements. Systematic errors have also been discovered during the course of this study, which highlights the benefit of using GPS as a supplementary atmospheric PWV sensor and calibration system. The selected eight GPS sites sample different climates across Australia covering an area of approximately 30° NS/EW. It has also shown that the magnitude and variation of PWV estimates depend on the amount of moisture in the atmosphere, which is a function of season, topography, and other regional climate conditions.

Dynamics of Rift-Opening Calving Dominant Ice Shelves and the Analysis of its Influencing Factors

Landsat imagery of TM, ETM+ and L8 were taken as data source and the partial least-squares regression was conducted to investigate the response of dynamics of Ross Ice Shelf and Ronne-Flchner Ice Shelf belonging to rift-opening calving dominant ice shelves to the natural environmental factors. The results show that, these two ice shelves have been extending to the ocean at nearly uniform speed along each coastline. The factors influence the dynamics of ice shelves via affecting the glacier movement. Surface air temperature and surface wind velocity facilitate the extension of ice shelves. Sea surface temperature, near-surface current velocity and atmospheric precipitable water are negatively correlated with the areal changes of ice shelves along each coastline. Salinity of the ocean is influenced by the ice shelves, and is positively correlated to the areal changes.

Similar concentration of surfactants in rural and urban areas

Since surfactants are used in various products, they end up in surface and wastewater. Surfactants may therefore impact ecosystems and living organisms. Actually, only few anionic surfactants and some alkylphenols are regulated. There is no comprehensive evaluation of surfactants in the atmosphere, surfaces and waters of areas of increasing anthropic levels. Here, we measured the levels of cationic, anionic and nonionic surfactants in atmospheric precipitation, surface and run-off waters collected from urban and rural areas. Compounds were analysed by spectrophotometry. Results show that the highest contaminations of 0.058–1.3 mg/L are observed for anionic and nonionic surfactants. This finding is explained by the more frequent use of anionic and nonionic surfactants versus cationic surfactants. Results also show unexpectedly no difference of surfactant concentration between urban and rural areas.

Mars Science Laboratory relative humidity observations: Initial results.

The Mars Science Laboratory (MSL) made a successful landing at Gale crater early August 2012. MSL has an environmental instrument package called the Rover Environmental Monitoring Station (REMS) as a part of its scientific payload. REMS comprises instrumentation for the observation of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements. We concentrate on describing the REMS-H measurement performance and initial observations during the first 100 MSL sols as well as constraining the REMS-H results by comparing them with earlier observations and modeling results. The REMS-H device is based on polymeric capacitive humidity sensors developed by Vaisala Inc., and it makes use of transducer electronics section placed in the vicinity of the three humidity sensor heads. The humidity device is mounted on the REMS boom providing ventilation with the ambient atmosphere through a filter protecting the device from airborne dust. The final relative humidity results appear to be convincing and are aligned with earlier indirect observations of the total atmospheric precipitable water content. The water mixing ratio in the atmospheric surface layer appears to vary between 30 and 75 ppm. When assuming uniform mixing, the precipitable water content of the atmosphere is ranging from a few to six precipitable micrometers.Key PointsAtmospheric water mixing ratio at Gale crater varies from 30 to 140 ppmMSL relative humidity observation provides good dataHighest detected relative humidity reading during first MSL 100 sols is RH75%

A feasibility study for the construction of an atmospheric precipitable water vapor model based on the neural network technology

AbstractAs the dominant greenhouse gas in the atmosphere, water vapor not only affects global climate and weather but also plays a very important role in global heat and water cycles. Studies of precipitable water vapor (PWV) in the atmosphere are necessary to further understand the processes of disastrous weather, climate change, and the distribution of water vapor resources. However, the process of calculating PWV using radio-sounding data (RPWV) is problematic. Firstly, radio-sounding datasets often contain missing or erroneous data. Moreover, the calculations about RPWV are relatively complicated, which restricts further studies on changes of water vapor in the atmosphere. To overcome limitations associated with data derived from radio-sounding data, this paper evaluates the use of a neural network model for PWV by using reanalysis data from the National Centers for Environmental Prediction and the National Center for Atmospheric Research. A high precision neural network model was established through ...

Relationship between inter-annual variations of microwave land surface emissivity and climate factors over the desert

Microwave land surface emissivity of the Taklimakan Desert was retrieved based on AMSR- E( advanced microwave scanning radiometer-earth observing system) Leval 2A measurements and land surface and atmosphere products from GDAS( global data assimilation system) in 2008 under clear atmospheric conditions.Then,the spectral characteristics of the retrieved emissivity were classified and analyzed with respect to the soil types,and the relationships between desert emissivity annual variability and climate factors were also analyzed. The analyses indicate that the desert microwave emissivity and its annual variability are closely related to soil types.Moreover,there is a significant correlation between soil volume water content as well as land skin temperature and inter- annual variations of emissivity,which decreases with both of the two land surface parameters. Furthermore,vegetation coverage,canopy water content and surface roughness depending on the soil moisture are also the influencing factors of emissivity,and the soil moisture is restricted by both the atmospheric total precipitable water and the underlying soil type. Additionally,the surface emissivity of the desert mostly composed of sand observably decreases with the desert depth.

Trends and variability in atmospheric precipitable water over the Tibetan Plateau for 2000-2010

The trends and variations in precipitable water (PW) over the Tibetan Plateau (TP) from 2000 to 2010 are analysed using the monthly mean PW datasets from Moderate Resolution Imaging Spectroradiometer (MODIS) and ERA-Interim reanalysis of European Centre for Medium-Range Weather Forecasts (ECMWF). Three different methods (including linear fit, non-parametric and non-linear) are used to estimate PW trends and their significance. The trend patterns derived from MODIS and ECMWF are very similar except for the magnitude. Increasing trends are found in the eastern and western TP; with decreasing trends in the middle. Atmospheric water vapour is more changeable compared to the surrounding areas and large PW anomalies occur frequently in July and August over the TP. Regression analysis between monthly mean anomalies of ECMWF PW and ECMWF surface air temperature (SAT) indicates reanalyses data show larger regression slope (7.36 +/- 0.75 % K-1) over the TP than the MODIS observations (4.81 +/- 0.72 % K-1) mainly in the non-monsoon season. The comparison of the vertically integrated moisture flux and its divergence between the wettest and driest monsoon seasons indicates that the PW spatial variability in monsoon seasons over the TP is affected by the large-scale atmospheric circulation. Although the TP region is under the influence of one large-scale circulation pattern (the monsoon) and the consistent warming background, the PW trends and the relation of PW and temperature are spatially heterogeneous, which is particularly important for predicting hydrological changes in this region.

Impact of increased water vapor on precipitation efficiency over northern Eurasia

AbstractThis study investigates the relationships among water vapor, precipitation efficiency, precipitation amount, and air temperature anomalies on monthly time scales over northern Eurasia for winter and summer 2003–2010. Daily precipitation and temperature records at 505 historical stations, and atmospheric total precipitable water vapor and relative humidity data from Atmospheric Infrared Sounders, are used for analysis. Results show that higher atmospheric precipitable water associated with warmer temperature directly contributes to winter precipitation amount but has little impact on winter precipitation efficiency. However, accelerated decreasing relative humidity associated with higher temperature is the primary factor in the reduction of precipitation efficiency and precipitation amount regardless of higher precipitable water in summer. This study suggests that there are evident seasonal differences in precipitation trend associated with air temperature changes over the study region. Air temperature modifies a key atmospheric water variable that directly controls precipitation for that particular season.

The development of GPS TroWav tool for atmospheric – terrestrial studies

We have developed an efficient tool to process dual-frequency Global Positioning System (GPS) signals and the surface meteorological data, called the Tropospheric Water Vapor (TroWav) program. TroWav is a stand-alone program to compute atmospheric precipitable water vapor (PWV). The source of the program is developed using MatlabTM and the graphical user interface for the system was developed using a Visual Basic. The algorithms of the program capable to compute satellite elevation angle, Zenith Tropospheric Delay (ZTD), Zenith Hydrostatic Delay (ZHD), Zenith Wet Delay (ZWD) and mapping function. The tool is very practical and useful for sustainable atmospheric management.

Correlation between Atmospheric Water Vapor and Diurnal Temperature Range over China

Diurnal temperature range(DTR) is an important measure in studies of climate change and variability. The changes of DTR in different regions are affected by many different factors. In this study, the degree of correlation between the DTR and atmospheric precipitable water(PW) over China is explored using newly homogenized surface weather and sounding observations. The results show that PW changes broadly reflect the geographic patterns of DTR long-term trends over most of China during the period 1970–2012, with significant anticorrelations of trend patterns between the DTR and PW, especially over those regions with higher magnitude DTR trends. PW can largely explain about 40% or more(r2 ≥0.40) of the DTR changes, with a d(PW)/d(DTR) slope of-2% to-10% K-1 over most of northwestern and southeastern China, despite certain seasonal dependencies. For China as whole, the significant anticorrelations between the DTR and PW anomalies range from-0.42 to-0.75, with a d(PW)/d(DTR) slope of-6% to-11% K-1. This implies that long-term DTR changes are likely to be associated with opposite PW changes, approximately following the Clausius-Clapeyron equation. Furthermore, the relationship is more significant in the warm season than in the cold season. Thus, it is possible that PW can be considered as one potential factor when exploring long-term DTR changes over China. It should be noted that the present study has a largely statistical focus and that the underlying physical processes should therefore be examined in future work.

Deriving Solar Radiation in a Mountain Area from MODIS Information

Solar radiation has a direct influence on the air and ground temperature, indirect influence on the value of atmospheric humidity, movement of air masses and precipitations, and it is easy to understand how its evaluation is essential not only in the technological area such as for sizing solar heating and photovoltaic plants, but also in fields such as agriculture or meteorology. Nowadays, the assessment of the solar energy resources over large areas and the elaboration of solar radiation maps are conducted using satellite derived information. Among the existing methodologies, those based on parametric models to firstly estimate the clear-sky solar radiation are usual. The success of that option depends both on the accuracy of the solar radiation algorithm and the satellite derived information and on the relationship between each other.In this work, daily global solar irradiation under clear skies is estimated by means of a model which includes the horizon effects. This characteristic is important in those cases where a complex topography is present, such as mountains. The topographic information is obtained from a digital elevation model. The other inputs to the model are the atmospheric precipitable water vapour content, the Angström's turbidity coefficient and the ground albedo. Experimental values of the atmospheric precipitable water vapour content are obtained from the MODIS sensor. The two latter parameters are averaged values calculated on previous studies.Estimates by the model are compared with ground measurements obtained in fourteen radiometric stations located in a mountain zone (Sierra Nevada, Granada, Spain) recording global solar radiation, atmospheric temperature and relative humidity. Since ground experimental values of precipitable water vapour content are available, a comparison between these values and those derived from the MODIS sensor is also presented.

Global Distribution of Water Vapor and Cloud Cover—Sites for High-Performance THz Applications

Absorption of terahertz radiation by atmospheric water vapor is a serious impediment for radio astronomy and for long-distance communications. Transmission in the THz regime is dependent almost exclusively on atmospheric precipitable water vapor (PWV). Though much of the Earth has PWV that is too high for good transmission above 200 GHz, there are a number of dry sites with very low attenuation. We performed a global analysis of PWV with high-resolution measurements from the Moderate Resolution Imaging Spectrometer (MODIS) on two NASA Earth Observing System (EOS) satellites over the year of 2011. We determined PWV and cloud cover distributions and then developed a model to find transmission and atmospheric radiance as well as necessary integration times in the various windows. We produced global maps over the common THz windows for astronomical and satellite communications scenarios. Notably, we show that up through 1 THz, systems could be built in excellent sites of Chile, Greenland and the Tibetan Plateau, while Antarctic performance is good to 1.6 THz. For a ground-to-space communication link up through 847 GHz, we found several sites in the Continental United States where mean atmospheric attenuation is less than 40 dB; not an insurmountable challenge for a link.

Estimating Solar Radiation from MODIS Data

The assessment of the solar energy resources over large areas and the elaboration of solar radiation maps are nowdays conducted using satellite derived information. Among the existing methodologies, those based on parametric models to firstly estimate the clear-sky solar radiation are usual. The success of that option depends both on the accuracy of the solar radiation algorithm and the satellite derived information and on the relationship between each other.In this work, a new accurate parametric model to estimate global solar radiation under cloudless conditions is presented. Atmospheric precipitable water vapour content is the only experimental input to the model. These values are derived from the MODIS sensor, the major facility instrument on the EOS polar orbiting satellite platforms. The evaluation of the model performance has been carried on using ground measurements obtained in twelve radiometric stations located in the north face of the Sierra Nevada Natural Park in the surroundings of Huéneja (Granada), a town located in the South East of Spain in a mountain zone (Sierra Nevada, Granada, Spain). The radiometric stations record global solar radiation, atmospheric temperature and relative humidity. Since the precipitable water vapour content is also available from the ground stations, a preliminary analysis comparing both experimental data sets is also presented.

An observation campaign of precipitable water vapor with multiple GPS receivers in western Java, Indonesia

A campaign was conducted from 23 July to 5 August 2010 to measure atmospheric precipitable water vapor (PWV) using five Global Positioning System (GPS) receivers, stationed at four different locations in Jakarta and Bogor, western Java, Indonesia. Radiosondes were launched at an interval of 6 h to validate the GPS-derived PWV data. The validation resulted in a root mean square error of 2 to 3 mm in PWV. The influence of atmospheric pressure and temperature on GPS-derived PWV was evaluated. A regular semi-diurnal pressure oscillation was observed, showing an amplitude ranging from 3 to 5 hPa, which corresponds to 1.1 to 1.8 mm in PWV. A nocturnal temperature inversion layer was observed in the radiosonde profiles, which resulted in an error of about 0.5 mm in PWV. From 26 to 29 July, there was a passage of distributed rain clouds over western Java, moving southwestward from the equator toward the Indian Ocean. A second precipitation event, with scattered rain clouds forming locally near Bogor, occurred on 2 August. Both events were observed also by a C-band Doppler Radar operated near Jakarta. The highest peak of GPS-derived PWV (about 67 mm) registered during the campaign occurred on 27 July, coinciding with the distributed rainfall event. Spatial variations in the estimated PWV between the four sites were enhanced before both the analyzed rainfall events, on 27 July and 2 August. Peaks in the temporal variability of PWV were also observed in conjunction with the two events. The results indicated a relation between the space-time inhomogeneity of GPS-PWV and rainfall events in the tropics.

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

Abstract. In this paper we present the preliminary results of atmospheric column-integrated precipitable 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 quasi-simultaneous 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 between 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 onto the LC. Filter#1 is currently used in operational AERONET sun photometers. PWV obtained with LC-Filter#1 showed an overestimation above 0.18 and 0.25 cm compared to GPS and RS92, respectively, and root-mean-square errors (RMSEs) up to 0.27 cm and 0.24 cm, respectively. Filter#2, with a reduced out-of-band radiation, showed very low differences compared with the same references (≤ 0.05 cm) and RMSE values ≤ 0.08 cm in the case of GPS precise orbits. These results demonstrate the ability of the new lunar photometer to obtain accurate and continuous PWV measurements at night, and the remarkable influence of the filter's transmissivity response to 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 to AERONET.

Improved vegetation greenness increases summer atmospheric water vapor over Northern China

AbstractNorthern China is an environmentally vulnerable region with a severe water shortage. Several ecological restoration projects since the 1980s have greatly increased vegetation greenness. This study aims to assess the impacts of the changes in vegetation greenness from 1982 to 2008 on the atmospheric precipitable water (PW) over northern China during the summer seasons (June, July, and August) using reanalysis PW and satellite vegetation index data. Several statistical methods, such as linear regression (piecewise, stepwise), the Empirical Orthogonal Function, Pearson's correlation, have been used to explore the variations in and the coupling between vegetation greenness and PW. The influences of three major atmospheric circulations (the East Asian summer monsoon, the South Asian summer monsoon, and the Westerly circulation) have also been considered and excluded. The results show that summer vegetation greenness within the semi‐arid western part of northern China, including the Tibetan Plateau, is closely linked to summer PW after excluding the influences of atmospheric circulations and that vegetation accounts for as much as 30% of the total PW variance. Vegetation greenness in the central and western water‐limited regions of northern China has significant (>90% confidence level) positive impacts on summer PW. After investigating the relationships among evapotranspiration (ET), PW, and precipitation, it was concluded that strengthened ET driven by increased vegetation greenness makes a major contribution to increased PW. Different from the earlier hypothesis in the literature “only intact contiguous cover of natural forest having extensive borders with larger water bodies is able to keep land moisten up to an optimal for life level everywhere on land,” this study found that interior forest covered regions with adequate water supply can also provide an ET benefit of PW for other regions. This study demonstrates the implications of large‐scale ecological restoration projects on the hydrological cycle in arid/semi‐arid regions.

A case study of relationship between GPS PWV and solar variability during the declining phase of solar cycle 23

Water vapor plays an important role in the global climate system. A clear relationship between water vapor and solar activity can explain some physical mechanisms of how solar activity influences terrestrial weather/climate changes. To gain insight of this possible relationship, the atmospheric precipitable water vapor (PWV) as the terrestrial climate response was observed by ground-based GPS receivers over the Antarctic stations. The PWV changes analyzed for the period from 2003 to 2008 coincided with the declining phase of solar cycle 23 exhibited following the solar variability trend. Their relationship showed moderate to strong correlation with 0.45 < R2 < 0.93 (p < 0.01), on a monthly basis. This possible relationship suggests that when the solar-coupled geomagnetic activity is stronger, the Earth’s surface will be warmer, as indicated by electrical connection between ionosphere and troposphere.