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Publication date: Available online 9 May 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): D. Besliu-Ionescu, D.-C. Talpeanu, M. Mierla, G. Maris Muntean

Abstract

Coronal mass ejections (CMEs) are pieces of the puzzle that drive space weather. Numerous methods (theoretical, numerical and empirical) are being used to predict whether the CME will be geoeffective or not. We present here an attempt to predict the geoeffectiveness of a given CME using a modified version of logistic regression model proposed by Srivastava (2005), using only initial CME parameters. Our model attempts to forecast if the CME will be associated with geomagnetic storm defined by a minimum Dst value <−30 nT.

We applied this modified logistic regression model for CMEs detected by LASCO during the ascending phase of solar cycle 24 (April 1, 2010 to June 30, 2011). Although the hit rate and proportion correctness were not promising for the training CME set, we obtained good hit rates and proportion correctness for the validation set.

We expect to improve the model upon applying it to a dataset comprising an entire solar cycle.

Publication date: Available online 26 April 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Yu Zhao, Qi Feng, Aigang Lu

Abstract

A systematic investigation and greater understanding of the precipitation chemistry with respect to the altitude gradient in mountainous areas is necessary to promulgate the detrimental consequences of pollution on various ecosystems. Studies on the chemical compositions of wet precipitation were performed on the northern slopes of Mt. Taibai, Qinling Mountains, one of the highest mountains in East China, from different lateral monitoring stations (i.e., with elevations between 610 and 3511 m) over the period from 2011 to 2014. All samples were analyzed for major ions (SO42−, NO3−, Cl−, F−, NH4+, Ca2+, Mg2+, Na+, and K+). The results revealed that the total ion concentration and average measured ions concentrations in precipitation decreased with the increase of altitude in the Mt. Taibai. The concentrations of precipitation ions are always higher during non–monsoon period compared to the monsoon period, except for the altitude above 3000 m a.s.l. A negative gradient of approximately −6.58 and −34.04 μeq·L−1/100 m of the total ion concentrations was obtained during the monsoon and the non–monsoon period, respectively. NH4+ was the most promising species for completely neutralize the acidity at the altitude of 500–1000 and 3000–3500 m a.s.l., while Ca2+ was the potential species for completely neutralize the acidity at the altitude of 1000–3000 m a.s.l. The crustal–derived species (Ca2+, Mg2+, Na+, K+ and Cl−) exhibit statistically significant correlations with each other at the altitude from 500 to 2500 m a.s.l. (r = 0.31–0.91). The contributions of sea salt source and terrestrial source to SO42− and NO3− are small, which is mainly contributed by human activities. For Na+, Mg2+, and K+, there was both the contribution of the terrestrial and human activities. The inorganic pollutants (major ions such as the SO42−, NO3−, Cl−, F−, NH4+, Ca2+, Mg2+, Na+, and K+) in the Mt. Taibai appear to be derived from the regional crustal dusts, anthropogenic emissions, and the long–range transported from the sea.

Publication date: Available online 29 March 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Daniele Barroca Marra Alves, Eniuce Menezes de Souza, Tayná Aparecida Ferreira Gouveia

Abstract

GNSS (Global Navigation Satellite Systems) can provide high accuracy positioning at low cost. But, depending on the sources of error, e.g. the atmospheric effects, this accuracy can be degraded. The ionosphere is one of the most important error sources in GNSS positioning. Among several effects caused by the ionosphere, irregularities such as ionospheric scintillations are very relevant. They can cause cycle slips, degrade the positioning accuracy and, when severe enough, can even lead to a complete loss of signal lock. Brazil, in particular, is located in one of the regions most affected by ionospheric scintillations and these effects were intensified during the last solar maximum. The main goal of this paper is to evaluate the impact of scintillation effects on the degradation of positioning during the last solar maximum. Data from 2012 to 2014 of three reference stations located in different regions of Brazil was used. Statistically significant correlations were identified from Spearman's correlation coefficient. Using Odds Ratio, an effect-size statistic, it was possible to see that the chance of large discrepancies in 3D positioning coordinates could be three times greater under strong scintillation effects (S4 ≥ 1) than under moderate ones (0.5<S4<1).

Publication date: Available online 14 November 2018

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): K. Chenna Reddy, B. Premkumar

Abstract

Meteor observations with Gadanki MST radar usually detect variety of meteor echoes that includes head echoes, specular and non-specular trail echoes. Sometimes, but not always head echoes are followed by a sudden increase in signal strength amounting to many decibels at terminal end point of the trail, known as terminal flare echoes - a feature mostly observed with optical and high power large aperture (HPLA) radar systems. In this study, we report some examples of terminal flare echoes observed with Gadanki MST radar. Because these echoes provide valuable insight into the role of diffusion and plasma instabilities in the formation and evolution of meteor trail. From the observations, it has been noticed that the head echoes at higher altitudes are generating non-specular trail echoes, whereas they disintegrate as terminal flares associated with meteoroid fragmentation in lower altitudes. Although meteoroid fragmentation is a common phenomenon, but terminal flaring is a rare feature observed with Gadanki radar. A small, but non-negligible fraction of meteor events (∼2.5% of all head echo events) showed flaring apparently produced by terminal destruction of a meteoroid fragmentation along with the insights into the fragmentation and terminal flaring process.

Publication date: Available online 28 September 2018

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Peng Chen, Qinzheng Li, Yibin Yao, WanQiang Yao

Abstract

This study investigated the morphology of the Plasmaspheric Weddell Sea Anomaly (PWSA). Measurements by GPS receivers onboard COSMIC satellites were used to determine the slant total electron content (STEC) along signal propagation paths during 2007–2017, which were converted to the zenith direction using a specific plasmaspheric projection function to obtain vertical total electron content (VTEC). The characteristics of seasonal variation of the PWSA between the four seasons were examined under conditions of high and low solar activity that corresponded to values of the F10.7 index of >120 and ≤ 120, respectively. To investigate seasonal variation of plasmaspheric VTEC, maps of geographic latitude versus geographic longitude were constructed by binning the data into 5° latitudinal grids and 15° longitudinal grids. The median value of VTEC in each grid was calculated for each season under low and high solar activity conditions. The results showed that the WSA phenomenon could also be observed in the plasmasphere (altitude ≥ 800 km) as well as in the ionosphere. The anomaly is most prominent in winter under conditions of high solar activity, and it also can be found in spring and autumn, although its amplitude is relatively small. The equatorward neutral wind is the critical driver for PWSA formation. In addition, during the polar summer, high geographic latitudes are sunlit during the entire day, leading to prolonged photoionization. This is the most essential process for the existence of the nighttime maximum in the VTEC diurnal variation at the geographic latitudes of the PWSA.

Publication date: Available online 11 August 2018

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): A.R. Zahari, F.I. Romli

Abstract

Suborbital flight has progressively emerged as the potential future transport trend, whether for space tourism or other applications. While several design concepts have been explored thus far for the suborbital flight operation, one of the main lingering concerns is actually the destination of the flight. The altitude of 100 km, which is the commonly chosen destination for suborbital flight, provides an imaginary separation between air and space. The quest for this separation sparks intense debates not only in the scientific communities but also in the political circles and legal fraternities. In conjunction with that, this research aims to analyse the suborbital flight operation by using the analytical tool of Political, Economic, Social, Technological, Legal and Environmental (PESTLE) in order to discuss its implications to a nation. From the analysis, among the advantages of suborbital flight operation include the shifting of role for space development from public agency to private enterprise, creation of new industry to generate revenue, public opportunity for access to space, new, low cost and reusable technology and material and also the enhancement of atmospheric studies. On the other hand, among established disadvantages of suborbital flight operation include the absence of international consensus on the boundary between air and space, intensive capital requirement to develop new technology and infrastructure, damage to third party liability, limited track record for flight safety, lack of regulation for new industry and also the air pollution resulting from the flight activity. All in all, it can be taken that there are many advantages that suborbital flight could bring to a nation but its subsequent disadvantages have to be carefully considered as well to ensure the sustainability of its operation and industry.

Publication date: Available online 6 February 2018

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Hui Li, Chi Wang, Shengping He, Huijun Wang, Cui Tu, Jiyao Xu, Fei Li, Xiaocheng Guo

Abstract

Studies on Sun-climate connection have been carried out for several decades, and almost all of them focused on the effects of solar total irradiation energy. As the second major terrestrial energy source from outer space, the solar wind energy flux exhibits more significant long-term variations. However, its link to the global climate change is rarely concerned and remains a mystery. As a fundamental and important aspect of the Earth's weather and climate system, tropical cyclone activity has been causing more and more attentions. Here we investigate the possible modulation of the total energy flux input from the solar wind into the Earth's magnetosphere on the global tropical cyclone activity during 1963–2012. From a global perspective, the accumulated cyclone energy increases gradually since 1963 and starts to decrease after 1994. Compare to the previously frequently used parameters, e.g., the sunspot number, the total solar irradiation, the solar F10.7 irradiation, the tropical sea surface temperature, and the south oscillation index, the total solar wind energy flux input exhibits a better correlation with the global tropical cyclone activity. Furthermore, the tropical cyclones seem to be stronger with more intense geomagnetic activities. A plausible modulation mechanism is thus proposed to link the terrestrial weather phenomenon to the seemingly-unrelated solar wind energy input.

Publication date: Available online 2 February 2018

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Binod Adhikari, Nirakar Sapkota, Subodh Dahal, Binod Bhattarai, Krishna Khanal, Narayan P. Chapagain

Abstract

An EMF (electromagnetic field) is induced over an incremental area when magnetized plasma from sun interacts with the Earth's magnetic field. This phenomenon delivers a Geomagnetically Induced Current (GIC) or induces geo-electric field at the Earth's surface and in the ground. GIC and horizontal component of geomagnetic field have been studied with respect to various geomagnetic events. Particularly, we have studied four events. The first one is geomagnetically quiet period (5 October 2003), the second one is weak storm (21 October 2003), the third one is moderate storm (14 October 2003) and the last one is an intense storm (30 October 2003). By comparing the development of GIC during geomagnetic storms, we found that intense geomagnetic storms show higher development on GIC magnitude. The GIC during storm events is several times greater than that during the quiet day. AE index shows more activity in the event of 30th October than other events and GIC is also more in this event. This can be accounted to the greater geomagnetic disturbance in this case. The power ranges of higher intensity are seen at various time scales on different events. We have analysed GIC signal associated with four geomagnetic storms and found distinct periodicities at the time when H component highly perturbed. The characteristic of GIC signal demonstrates high variability with time without presence of continuous periodicities. Discrete wavelet transform (DWT) analysis reveals that whenever the geomagnetic field is perturbed, there will be high possibility of detecting GIC. The singularities present in GIC signal are due to the peak value of electrical currents system in the ionosphere and magnetosphere, and corresponding high fluctuations in H component. In this work, we explore the remarkable ability of wavelets to highlight the singularities associated with discontinuities present in the GIC.

Publication date: Available online 1 February 2018

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Shikun Lu, Hao Zhang, Xihai Li, Yihong Li, Chao Niu, Xiaoyun Yang, Daizhi Liu

Abstract

The modern science of networks has brought significant advances to our understanding of complex systems. We employ the probabilistic graphical model to build complex networks to model the global ionospheric variations. The global ionospheric maps (GIMs) of vertical total electron content (VTEC) for the 12 months in 2012 have been selected analyze the ionospheric variations from the perspective of complex network. The information flow in the networks represents the causal interactions between the ionospheric variations at different locations. The distributions of the edges' geospatial distances in the ionospheric networks show that the information flow in the ionosphere is mainly transmitted locally, almost obeying the geospatial proximity principle. The asymmetric distribution of the edges' distances probably elucidates the more efficient transmission of ionospheric variations in the westward and southward directions. The community topologies within the ionospheric networks indicate the effect of the geomagnetic field and geographical distance on the information flow in the ionosphere. The geomagnetic field has shown an enhanced effect on the meridional interaction in the ionosphere, causing the vertical community topologies within the ionospheric networks at middle and low latitudes. For the ionospheric cells located at high latitudes in GIM, the geographical distances result in the horizontal community topologies. The fractal analysis reveals the existence of self-similar structure in the ionospheric networks on the global scale. The fractality in the ionospheric information flow may indicate the reasonability of the VTEC's prediction at a certain location by spatial prediction based on the data obtained in known regions.

Publication date: Available online 31 January 2018

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Zamri Zainal Abidin, M.H. Jusoh, M. Abbas, O.S. Bolaji, A. Yoshikawa

Abstract

Magnetic records of the declination (D) component for the solar quiet year 2011–2013 obtained from Magnetic Data Acquisition System (MAGDAS) at Langkawi (Geog. Lon. 99.68∘ E, Geog. Lat. 6.30∘N), Malaysia were utilized in this study. The minutes averages were used to delineate the diurnal (Sq(D)) variation. The monthly mean (MSq(D)) and their seasonal variabilities (SVq(D)) were also analysed. The Sq(D) and their MSq(D) exhibit smooth regular occurring pattern in the month of April–September and became highly perturbed in October–March across the years. The highest positive (∼3.5 arc-min) and the negative (∼−3.0 arc-min) values were observed in August 2011 during the dawn and noon sectors. These maxima shifted to July and September in 2012 with peaks ∼3.2 and −3.0 arc-min. In 2013, the positive maximum (∼3.0 arc-min) and its negative (∼−2.5 arc-min) were again seen in August. This implies that the dawn and noon sectors of August 2011 and 2013 are strongly influenced by IHFACs and this effect shifted to July and September in 2012. IHFACs through the years flow from the winter to summer hemisphere during the noon and dusk sectors and flow in opposite direction during the dawn sector. The day-to-day magnitudes of Sq(D) and MSq(D) seems to suggest the inter-hemispheric imbalance of the ionospheric Sq current earlier established by Van Sabben as the cause of IHFACs is not strongly affected by the changes in annual solar variation. Dusk-side IHFACs were observed to be northbound in all the seasons with the exception of June solstice. The direction of IHFACs does not change except in April and November. The current intensity is not large in solstices except in August 2011 and 2013 but it shifted to July in 2012. The result further showed that the magnitude of the duskside IHFACS is determined to some extent by the strength of the noontime IHFACs. IHFACs were generally observed to be greater during the daytime than night-time hours.

Publication date: Available online 31 January 2018

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Zamri Zainal Abidin, M.H. Jusoh, M. Abbas, A. Yoshikawa

Abstract

The mantle electrical conductivity-depth structure of Malaysia was determined for the first time using solar quiet day ionospheric current (Sq) variations. Spherical harmonic analysis (SHA) was employed to separate the external and internal field contribution to the Sq variations. A transfer function was applied in estimating the conductivity-depth profile for the paired of external and internal coefficients of the SHA. We observed a downward increase in electrical conductivity with initial magnitude of 0.0065 S/m at a depth of ∼ 56 km which gradually rose to 0.0106 and 0.0140 S/m at 118 and 180 km. Subsequently, the conductivity profile rose to about 0.0228 S/m at 380 km (near the base of the upper mantle) and reached 0.0260 S/m at 435 km, after which a sharp steep increase was observed at 450 km with conductivity profile of 0.0278 S/m. Consequently, the conductivity profile increases significantly to about 0.1367 S/m at a depth of 973 km and reached its peak value 0.1975 S/m at the depth of 1097 km in the lower mantle with no indication of leveling off. An evidence of discontinuity was observed near 390–460 km and 675–746 km. A slight increase in conductivity values at depth between 150 and 300 km corresponds to the region of unusual global low velocity zone with high electrical conductivity. The conductivity profile showed a less steep increase above 450 km below which a steep increase was observed. The present profile showed the deepest penetration depth which may be attributed to the influence of equatorial electrojet current (EEJ) that is actively supported by the conductive properties of the Earth's interior within the study region.

Publication date: Available online 16 January 2018

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Yuyan Jin, Zanyang Xing, Qinghe Zhang, Yong Wang, Yuzhang Ma

Abstract

Polar cap patches are common irregularities in the polar ionosphere, where their formation and evolution can directly affect satellite navigations and communications as well as over-the-horizon radar observations, etc. However, affected by the various dynamic processes during the solar wind-magnetosphere-ionosphere coupling, there is no fully accepted formation mechanism of polar cap patches. In this paper, a statistical analysis of 345 patches at the dayside sectors during 09:00–15:00 magnetic local time (MLT), observed by EISCAT Svalbard Radar (ESR) 42 m antenna from 2010 to 2013, has been performed. The dependence of their occurrence on solar wind and interplanetary magnetic field (IMF) conditions as well as their MLT distribution has been statistically investigated. The results show that the polar cap patches are preferentially formed during southward IMF conditions. In particular, the MLT dependence of the patches presents a clear IMF By-related prenoon-postnoon asymmetry, suggesting the patch formation is clearly modulated by the IMF By polarity. Moreover, our statistical results indicate that the patches should not be caused by the variations of the solar wind dynamic pressure or the solar wind velocity. All the results indicate that the pulsed dayside magnetic reconnection is possibly a significant formation mechanism of polar cap patches.

Publication date: Available online 6 January 2018

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Hammed A. Lawal, Mark Lester, Stanley W.H. Cowley, S.E. Milan, T.K. Yeoman, Gabby Provan, Suzie Imber, A.Babatunde Rabiu

Abstract

The equatorial region of the Earth's ionosphere is one of the most complex ionospheric regions due to its interactions, instabilities, and several unresolved questions regarding its dynamics, electrodynamics, and physical processes. The equatorial ionosphere overall spans three continents with the longest region being that over the African continent. Satellite observations have demonstrated that very large differences exist in the formation of ionospheric irregularities over the African sector compared with other longitudinal sectors. This may be a consequence of the symmetric shape of the magnetic equator over the continent and the lack of variability in latitude. In this paper, we propose a science campaign to equip the African sector of the magnetic equator with ground-based instruments, specifically magnetometers and radars. The network of radars proposed is similar in style and technique to the high-latitude SuperDARN radar network, while the magnetometers will form an array along the equatorial belt. These two proposed space physics instruments will be used to study this region of the equatorial ionosphere over a long interval of time, at least one solar cycle. The deployment of an array of magnetometers (AfrequaMA) and a radar network (AfrequaRN) in the African sector of the magnetic equator is jointly called the Africa Equatorial Magnetometer Array and Radar Network (AfrequaMARN), which will provide simultaneous observations of both electric and magnetic variations over the African sector. We also examine the possible science questions such a magnetometer array and radar network would be able to address, both individually and in conjunction with other space-based and ground-based instrumentation. The proposed projects will clearly improve our understanding of the dynamics of the equatorial ionosphere and our understanding of its role in balancing the large-scale ionospheric current system, and will contribute to our ability to adequately model ionospheric and plasmaspheric densities. It will also enhance our understanding of global ionospheric processes, which will improve the space weather capabilities of the African and international space science communities.

Progress towards a probabilistic Earth system model: examining the impact of stochasticity in the atmosphere and land component of EC-Earth v3.2
Kristian Strommen, Hannah M. Christensen, Dave MacLeod, Stephan Juricke, and Tim N. Palmer
Geosci. Model Dev., 12, 3099-3118, https://doi.org/10.5194/gmd-12-3099-2019, 2019
Due to computational limitations, climate models cannot fully resolve the laws of physics below a certain scale – a large source of errors and uncertainty. Stochastic schemes aim to account for this by randomly sampling the possible unresolved states. We develop new stochastic schemes for the EC-Earth climate model and evaluate their impact on model performance. While several benefits are found, the impact is sometimes too strong, suggesting such schemes must be carefully calibrated before use.

CLIMADA v1: a global weather and climate risk assessment platform
Gabriela Aznar-Siguan and David N. Bresch
Geosci. Model Dev., 12, 3085-3097, https://doi.org/10.5194/gmd-12-3085-2019, 2019
The need for assessing the risk of weather events is ever increasing. In addition to quantification of risk today, the role of aggravating factors such as population growth and changing climate conditions matter too. We present the open-source software CLIMADA, which integrates hazard, exposure, and vulnerability to compute metrics to assess risk and to quantify socio-economic impact, and use it to estimate and contextualize the damage of hurricane Irma through the Caribbean in 2017.

Simulating precipitation radar observations from a geostationary satellite
Atsushi Okazaki, Takumi Honda, Shunji Kotsuki, Moeka Yamaji, Takuji Kubota, Riko Oki, Toshio Iguchi, and Takemasa Miyoshi
Atmos. Meas. Tech., 12, 3985-3996, https://doi.org/10.5194/amt-12-3985-2019, 2019
The JAXA is surveying the feasibility of a potential satellite mission equipped with a precipitation radar on a geostationary orbit, as a successor of the GPM Core Observatory. We investigate what kind of observation data will be available from the radar using simulation techniques. Although the quality of the observation depends on the radar specifications and the position of precipitation systems, the results demonstrate that it would be possible to obtain three-dimensional precipitation data.

A geometry-dependent surface Lambertian-equivalent reflectivity product for UV–Vis retrievals – Part 1: Evaluation over land surfaces using measurements from OMI at 466 nm
Wenhan Qin, Zachary Fasnacht, David Haffner, Alexander Vasilkov, Joanna Joiner, Nickolay Krotkov, Bradford Fisher, and Robert Spurr
Atmos. Meas. Tech., 12, 3997-4017, https://doi.org/10.5194/amt-12-3997-2019, 2019
Satellite observations depend on Sun and view angles due to anisotropy of the Earth's atmosphere and surface reflection. But most of the ultraviolet and visible cloud, aerosol, and trace-gas algorithms utilize surface reflectivity databases that do not account for surface anisotropy. We create a surface database using the GLER concept which adequately accounts for surface anisotropy, validate it with independent satellite data, and provide a simple implementation to the current algorithms.

Comparison between the assimilation of IASI Level 2 ozone retrievals and Level 1 radiances in a chemical transport model
Emanuele Emili, Brice Barret, Eric Le Flochmoën, and Daniel Cariolle
Atmos. Meas. Tech., 12, 3963-3984, https://doi.org/10.5194/amt-12-3963-2019, 2019
We examine the differences between assimilating ozone profiles retrieved from IASI or the corresponding infrared spectra in a chemical transport model. This allows the impact of the retrieval's prior information on ozone reanalyses to be quantified. We found that significant differences can arise between the two approaches, depending on the latitude. An improved O3 variability is obtained assimilating IASI radiances directly. The implications for coupled Earth system models are discussed.

Rayleigh wind retrieval for the ALADIN airborne demonstrator of the Aeolus mission using simulated response calibration
Xiaochun Zhai, Uwe Marksteiner, Fabian Weiler, Christian Lemmerz, Oliver Lux, Benjamin Witschas, and Oliver Reitebuch
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2019-274,2019
Manuscript under review for AMT (discussion: open, 0 comments)
An airborne prototype called A2D was developed for validating the Aeolus measurement principle based on realistic atmospheric signals. However, the atmospheric and instrumental variability currently limit the reliability and repeatability of the measured Rayleigh response calibration (MRRC), which is a prerequisite for accurate wind retrieval. A procedure for a simulated Rayleigh response calibration is developed and presented to resolve these limitations of the A2D Rayleigh channel MRRC.

Simulating precipitation radar observations from a geostationary satellite
Atsushi Okazaki, Takumi Honda, Shunji Kotsuki, Moeka Yamaji, Takuji Kubota, Riko Oki, Toshio Iguchi, and Takemasa Miyoshi
Atmos. Meas. Tech., 12, 3985-3996, https://doi.org/10.5194/amt-12-3985-2019, 2019
The JAXA is surveying the feasibility of a potential satellite mission equipped with a precipitation radar on a geostationary orbit, as a successor of the GPM Core Observatory. We investigate what kind of observation data will be available from the radar using simulation techniques. Although the quality of the observation depends on the radar specifications and the position of precipitation systems, the results demonstrate that it would be possible to obtain three-dimensional precipitation data.