This study shows vertical profiles and spatial distribution of upper‐air icing frequency over the tropical Americas. We estimated the in‐flight icing (IFI) over Colombia using the Current Icing ...Product‐sonde‐A algorithm over two data sets: (1) vertical soundings of temperature and relative humidity and surface station data taken at 12 Coordinated Universal Time or UTC (07 Local Time or LT) on five sites and (2) ERA5 at 00, 06, 12 and 18 UTC (19, 01, 07 and 13 LT). In either case, icing was defined for IFI values exceeding 0.01. Results show that icing tends to occur between 550 and 300 hPa (4.5 and 8.6 km altitude), with a maximum at 500–550 hPa and monotonically decreasing to zero until reaching 300 hPa. Aeronautic reports were used to evaluate the total column IFI and a layer‐based IFI detection with a probability of detection of 87% and 71%, respectively. The annual cycle of IFI is modulated by the meridional migration of the Intertropical Convergence Zone (ITCZ) with a bimodal distribution with peaks during the rainiest seasons. Spatially, IFI hotspots are found in the Pacific, the Andes Mountains and the Amazonia regions of Colombia; the northern Colombia Caribbean region show lower IFI frequency with a relative maximum collocated over the Sierra Nevada de Santa Marta mountains. The IFI exhibits a strong diurnal cycle with a high between night‐time to early morning and a low around noon.
We estimated the in‐flight icing (IFI) using the Current Icing Product ‐sonde‐A algorithm. High IFI frequency hotspots are found in the Pacific, the Andes Mountains and the Amazon regions of Colombia. The annual cycle of IFI frequencies over Colombia (part of tropical Americas) is modulated by the meridional migration of the ITCZ, which favours a bimodal distribution of highs coinciding with that of the rainy seasons. The IFI frequencies exhibit a strong diurnal cycle with high between night‐time to early morning and a low around noon.
Theoretical magnetotelluric (MT) soundings are investigated for a stratified (five-layered) Earth model consisting of two transitional layers with conductivity varying linearly with depth, and three ...homogeneous layers with constant conductivity. The analytical expressions for the tangential electric and magnetic fields as well as the surface impedance are derived in terms of Airy functions. The effect of the thicknesses of the two transitional layers and the interlayer between them on the MT responses (apparent resistivity and impedance phase) is examined in detail.
Abstract
Hundreds of supercell proximity soundings obtained for field programs over the central United States are analyzed to reconcile differences in recent studies and to refine our knowledge of ...supercell environments. The large, storm-centric observation-based dataset and high vertical resolution of the sounding data provide an unprecedented look at supercell environments. Not surprisingly, storm-relative environmental helicity (SRH) is found to be larger in tornadic soundings than in nontornadic soundings. The primary finding that departs from previous studies is that storm-relative winds contribute substantially to the larger SRH. Stronger ground-relative winds and more rightward-deviant storm motions contribute to the larger storm-relative winds for the tornadic soundings. Spatial analyses of the soundings reveal lower near-ground pressure perturbations and stronger low- to midlevel cyclonic flow for the tornadic soundings, which suggests stronger mesocyclones, perhaps explaining the more rightward-deviant motions. Differences in the mean critical angle between the tornadic and nontornadic soundings are small and do not contribute to the larger mean SRH, but the tornadic soundings do have fewer instances of smaller (<60°) critical angles. Furthermore, the critical angle is shown to be a function of azimuth from the updraft. Other results include a low-to-the-ground (~250 m on average) hodograph kink for both the tornadic and nontornadic soundings and few notable differences in thermodynamic quantities, except for the expected lower LCLs related to higher RH for the tornadic soundings, somewhat
smaller
0–3 km lapse rates in tornadic environments related to weaker/shallower capping inversions, and larger 0–3 km CAPE in near-field environments.
This paper presents an assessment of the usage of Arctic atmospheric observations in the Numerical Weather Prediction (NWP) system of the European Centre for Medium‐Range Weather Forecasts, and of ...their impact on the quality of short‐ to medium‐range forecasts. The Arctic has low coverage of conventional data north of 70°N but one of the highest levels of coverage of satellite sounding data on Earth. The impact of Arctic observations on forecast skill was assessed by performing Observing System Experiments, in which different observation types were removed from the full observing system. This assessment was complemented by an analysis of Forecast Sensitivity to Observation Impact diagnostics. To our knowledge it is the first time that comprehensive numerical experimentation has been carried out to explore the role of different Arctic observations in a state‐of‐the‐art global operational NWP system. All Arctic observations were found to have a positive impact on forecast skill in the Arctic region, with the greatest tropospheric impacts on both short‐ and medium‐range forecasts due to microwave, conventional and infrared sounding observations. Results indicate the great importance of microwave sounding data and conventional data, which are found to be the key observing systems in the summer and winter seasons, respectively. These observations were found to have positive and statistically significant impacts on forecasts not only in the Arctic but also in the midlatitude regions at longer lead times. Differences between the seasons are most likely due to problems assimilating microwave sounding observations over snow and sea ice, leading to a reduced impact in winter. There is also the suggestion of increased importance of conventional data in winter, and other factors may also play a role.
The Arctic region has a relatively sparse coverage of in‐situ atmospheric observations but the best coverage of Low Earth Orbit satellite temperature and humidity sounding observations of anywhere in the globe, as shown in the image. In this paper, we assess the impact of observations in the Arctic on Numerical Weather Predictions, through comprehensive observing system experiments in a state‐of‐the‐art NWP system. We find that the largest impacts come from satellite microwave radiances in summer and in‐situ observations in winter.
Over the past 70 years, many different components of the cryosphere have been imaged with a variety of radar systems using increasingly sophisticated processing techniques. These systems use various ...pulse lengths, signal frequencies and, in some cases, modulated signals. The increasing diversity of radar systems has created the potential for confusion due to the use of non-consistent terminology. Here we provide an overview of state-of-the-science radar technologies and suggest a simplified and unified terminology for use by the cryosphere community. We recommend a terminology that is target independent but specifies the characteristics of the signal. Following this recommendation, commercial impulse systems that penetrate the subsurface should be referred to as ground-penetrating radar (GPR), and pulse radars as radio-echo sounding (RES). Continuous-wave (CW) radar systems should be referred to as ground-penetrating CW radars. We further suggest any additional characterisation of the system be expressed using descriptors that specify the platform it is mounted on (e.g. airborne) or the frequency range (e.g. HF (high frequency)) or modulation (e.g. FM (frequency modulated)).
Recently, the groundwater became very important source for the Egyptian water balance. Therefore, assessing its quality and quantity is necessary before initiating any developmental plans using this ...resource. In this research, a new operated power plant, which is located in the coastal area of West New Damietta City, north-east of Egypt was designed to work using the coastal groundwater aquifer. Therefore, an integrated approaches of both geophysical methods and hydrochemical analysis were applied to identify the subsurface lithology, the water-bearing layers and determine the potential use of such coastal groundwater. Therefore, a total of seventeen vertical electrical soundings (VES) and five time-domain electromagnetic soundings (TEM) were performed. Moreover, groundwater samples were collected from seven existing wells to be analyzed for water quality assessment. The geophysical results identified five geoelectric layers. The first geoelectric layer has a resistivity of 1–7.9 Ω m and a thickness range of 7–9 m. The second layer has a resistivity of 0.9–4.4 Ω m and a thickness range of 7–8 m. The third layer is 10–21 m thick with a resistivity value of 0.5–2 Ω m. The fourth layer, which is thicker (29 to 42 m), has a resistivity of 0.7–3 Ω m, while the last layer has a resistivity of 1.7–9 Ω m. According to the hydrochemical analysis, the aquifer is dominated by Na–Cl water type. The brackish nature of the water is revealed by the TDS range of 7035 mg/l to 7735 mg/l. The results collected demonstrate the groundwater's quantity and quality availability for the power plant’s sustainable use.
Groundwater occurrence in continental flood basalt, where multiple lava flows separated by intertrappean and irregular patterns of lineaments govern the regional hydro-dynamics, is poorly understood. ...This necessitates a high-resolution hydrogeophysical investigation to devise an effective groundwater management plan. To enhance the knowledge and unravel the hydrogeological complexity of such systems, an integrated hydrogeophysical investigation consisting of local-scale vertical electrical soundings, ground-based transient electromagnetic soundings, relatively large-scale electrical resistivity tomography (ERT) and helicopter-borne transient electromagnetic (H-TEM) surveys was carried out in an area of the Deccan Traps (372 km
2
) near Nagpur, central India. A 14.4-km-long and almost continuous profile of ERT was conducted, with special attention to the lateral discontinuity, which was compared with the H-TEM data. The results from these studies were further supported and validated by drilling of exploratory wells at select locations, geophysical logging and pumping tests. Integration of the results successfully provided a geophysical characterization of the basalts, to develop a consistent lithological model that was finally transformed into hydrogeological sections. The pumping test (exploratory wells) derived aquifer transmissivity data that complemented the anomalies of the electrical parameters. Furthermore, the hydrogeological observations revealed that the groundwater yield is strongly correlated (
R
2
= 0.78) with the depth to the Basalt-Gondwana contact.
Russian (former Soviet) systematic studies of Antarctica by radio-echo sounding (RES) and ground-penetrating radar technique (GPR) were commenced in 1964. Since that time airborne RES surveys have ...covered about 5.5 × 106 km2 of the icy continent discovering remarkable geographic objects such as Subglacial Gamburtsev Mountains, and allowed studies of Filchner-Ronne Ice Shelf, Amery Ice Shelf and Lambert Glacier. Ground-based investigations during the 1990s and 2000s revealed the structure of the Lake Vostok area and surveyed along the Mirny to Vostok and Progress to Vostok traverse routes. GPR studies during the 2010s were to select the site for a new snow-runway at Mirny Station, with the resumption of the aviation after a 25 year hiatus.
An integrated study using geophysical method in combination with pumping tests and geochemical method was carried out to delineate groundwater potential zones in Mian Channu area of Pakistan. ...Vertical electrical soundings (VES) using Schlumberger configuration with maximum current electrode spacing (AB/2 = 200 m) were conducted at 50 stations and 10 pumping tests at borehole sites were performed in close proximity to 10 of the VES stations. The aim of this study is to establish a correlation between the hydraulic parameters obtained from geophysical method and pumping tests so that the aquifer potential can be estimated from the geoelectrical surface measurements where no pumping tests exist. The aquifer parameters, namely, transmissivity and hydraulic conductivity were estimated from Dar Zarrouyk parameters by interpreting the layer parameters such as true resistivities and thicknesses. Geoelectrical succession of five-layer strata (i.e., topsoil, clay, clay sand, sand, and sand gravel) with sand as a dominant lithology was found in the study area. Physicochemical parameters interpreted by World Health Organization and Food and Agriculture Organization were well correlated with the aquifer parameters obtained by geoelectrical method and pumping tests. The aquifer potential zones identified by modeled resistivity, Dar Zarrouk parameters, pumped aquifer parameters, and physicochemical parameters reveal that sand and gravel sand with high values of transmissivity and hydraulic conductivity are highly promising water bearing layers in northwest of the study area. Strong correlation between estimated and pumped aquifer parameters suggest that, in case of sparse well data, geophysical technique is useful to estimate the hydraulic potential of the aquifer with varying lithology.
Abstract Using an index of tropical easterly wave (TEW) activity derived from spacetime‐filtered outgoing longwave radiation, we construct composites of long‐term hourly surface meteorological ...observations and morningtime sounding data collected near San José, Costa Rica to investigate how TEWs affect the diurnal cycle of rainfall over land. Our results indicate that TEWs enhance the frequency of occurrence of rain during convectively active conditions over the course of the diurnal cycle. By contrast, rainfall conditional intensity sensitivity to TEW phase appears more nuanced, with indications that active conditions induce a slight delay in the timing of the diurnal peak intensity but a longer duration of heavier rainfall. Analysis of associated hourly surface meteorology along with sounding profiles and derived thermodynamic parameters points to both initial vertical and time‐evolving surface conditions regulating diurnal behavior, such as greater instability and higher precipitable water in morningtime profiles under active phase conditions.
Plain Language Summary Over tropical land, rainfall often follows a characteristic daily (or diurnal) cycle, with a peak in the late afternoon. This study explores how tropical easterly waves, westward‐propagating weather disturbances known to impact rainfall over many parts of the Tropics, affect the rainfall diurnal cycle at a long‐term observation site near San José, Costa Rica. Using an index of tropical easterly wave activity, and considering the diurnal cycle in terms of rainfall occurrence frequency and intensity, the results presented here indicate generally enhanced occurrence frequency over the course of the diurnal cycle during active conditions of tropical easterly waves, while intensity shows a more nuanced behavior, with active phases showing a slight lag in peak diurnal intensity with an overall lengthening of the highest intensities. Such diurnal rainfall sensitivity to tropical easterly waves is interpreted in terms of hourly surface meteorological observations and vertical profiles from morningtime soundings.
Key Points Tropical easterly wave (TEW) impact on the rainfall diurnal cycle over Costa Rica is documented in surface meteorological and sounding data Convectively active phases of tropical easterly waves are associated with increased hourly rainfall frequency of occurrence Rainfall intensity sensitivity to TEW phase is more subtle, with indications of delayed active phase peak intensity
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