Adequate Vertical Resolution Research Articles

High resolution mapping of sound speed and density with broadband echo sounders

Advances in acoustic propagation and physical oceanographic modeling necessitate improved spatiotemporal resolution of water column properties (temperature, salinity, sound speed, and density) to inform and validate models. Shipboard profiling provides adequate vertical resolution, but high-resolution horizontal sampling is expensive and time consuming. Stationary arrays generate critical long-term data sets and high vertical resolution, however, there is a trade-off between dense horizontal sampling and total spatial coverage. Towed systems provide dense coverage horizontally but lack vertical resolution in a single location. During the ONR funded New England Shelf Break Acoustics experiments in 2021, sparse shipboard CTD and expendable bathythermograph (XBT) casts were combined with backscatter measurements by shipboard broadband echo sounders to map water column physical properties of the New England Shelf Break front with high resolution vertically and horizontally. The shipboard echo sounders detected backscatter from the strong gradients of the shelf break front, physical microstructure, and internal waves present at the frontal boundary. Acoustically tracking the front between CTD casts resulted in high resolution profiles of water column properties. Acoustic propagation modeling at 500 Hz and 4 kHz was compared when using the acoustically determined water column profile and when using profiles from CTD and XBT casts alone.

Boundary-layer height and surface stability at Hyytiälä, Finland, in ERA5 and observations

Abstract. We investigate the boundary-layer (BL) height at Hyytiälä in southern Finland diagnosed from radiosonde observations, a microwave radiometer (MWR) and ERA5 reanalysis. Four different, pre-existing algorithms are used to diagnose the BL height from the radiosondes. The diagnosed BL height is sensitive to the method used. The level of agreement, and the sign of systematic bias between the four different methods, depends on the surface-layer stability. For very unstable situations, the median BL height diagnosed from the radiosondes varies from 600 to 1500 m depending on which method is applied. Good agreement between the BL height in ERA5 and diagnosed from the radiosondes using Richardson-number-based methods is found for almost all stability classes, suggesting that ERA5 has adequate vertical resolution near the surface to resolve the BL structure. However, ERA5 overestimates the BL height in very stable conditions, highlighting the ongoing challenge for numerical models to correctly resolve the stable BL. Furthermore, ERA5 BL height differs most from the radiosondes at 18:00 UTC, suggesting ERA5 does not resolve the evening transition correctly. BL height estimates from the MWR are also found to be reliable in unstable situations but often are inaccurate under stable conditions when, in comparison to ERA5 BL heights, they are much deeper. The errors in the MWR BL height estimates originate from the limitations of the manufacturer's algorithm for stable conditions and also the misidentification of the type of BL. A climatology of the annual and diurnal cycle of BL height, based on ERA5 data, and surface-layer stability, based on eddy covariance observations, was created. The shallowest (353 m) monthly median BL height occurs in February and the deepest (576 m) in June. In winter there is no diurnal cycle in BL height; unstable BLs are rare, yet so are very stable BLs. The shallowest BLs occur at night in spring and summer, and very stable conditions are most common at night in the warm season. Finally, using ERA5 gridded data, we determined that the BL height observed at Hyytiälä is representative of most land areas in southern and central Finland. However, the spatial variability of the BL height is largest during daytime in summer, reducing the area over which BL height observations from Hyytiälä would be representative.

Seismic inversion as a reliable technique to anticipating of porosity and facies delineation, a case study on Asmari Formation in Hendijan field, southwest part of Iran

Porosity and facies are two main properties of rock which control the reservoir quality and have significant role in petroleum exploration and production. Well and seismic data are the most prevalent information for reservoir characterization. Well information such as logs prepare adequate vertical resolution but leave a large distance between the wells. In comparison, three-dimensional seismic data can prepare more detailed reservoir characterization in the inter-well space. Generally, seismic data are an efficient tool for identification of reservoir structure; however, such data usable in reservoir characterization. Therefore, these two types of information were incorporated in order to obtain reservoir properties including porosity and facies in the study area. Using Multimin algorithm, petrophysical analysis was carried out for estimation of reservoir porosity. Then, an accurate post-stack inversion was accomplished to obtain the acoustic impedance volume. The results showed that the Ghar sandstone is characterized by a lower acoustic impedance compared to the high acoustic impedance Asmari Formation. Because of a relationship between acoustic impedance and reservoir properties (i.e., porosity), porosity cube calculation was performed by artificial neural network method which is a popular approach for parameter estimation in petroleum exploration. The consequences showed a good agreement between log based and seismic inversion-derived porosity. The inversion results and well logs cross-plots analyses illustrated that the Ghar member considered as a high quality zone with porosity 22 to 32 percent and the Asmari dolomite shows a low quality interval characters with porosity 1 to 6 percent. The findings of this study can help for better understanding of reservoir quality (especially porous Ghar member delineation) by lithology discrimination in the analysis of identification reservoirs and finding productive well location in Hendijan field.

A smoothing technique for improving atmospheric reconstruction for planetary entry probes

Accelerometer instruments are commonly used on planetary entry probes to determine vertical profiles of atmospheric density, pressure, and temperature. A key consideration for the design and implementation of such investigations is extending the atmospheric results to the highest altitudes possible, which requires minimizing uncertainties in measured accelerations whilst maintaining adequate vertical resolution. Since atmospheric density depends exponentially on altitude, the arithmetic mean of a subset of raw acceleration data points is a biased estimate of the true acceleration at the center of the time interval in question. This diminishes the quality of derived atmospheric properties. Here we show how this problem can be alleviated by using a specialized averaging technique that takes advantage of the inherent exponential variation in acceleration with time at atmospheric entry. This technique is demonstrated successfully on Mars Phoenix data.

Reference Upper-Air Observations for Climate: Rationale, Progress, and Plans

While the global upper-air observing network has provided useful observations for operational weather forecasting for decades, its measurements lack the accuracy and long-term continuity needed for understanding climate change. Consequently, the scientific community faces uncertainty on key climate issues, such as the nature of temperature trends in the troposphere and stratosphere; the climatology, radiative effects, and hydrological role of water vapor in the upper troposphere and stratosphere; and the vertical profile of changes in atmospheric ozone, aerosols, and other trace constituents. Radiosonde data provide adequate vertical resolution to address these issues, but they have questionable accuracy and time-varying biases due to changing instrumentation and techniques. Although satellite systems provide global coverage, their vertical resolution is sometimes inadequate and they require independent reference observations for sensor and data product validation, and for merging observations from differ...

Z-probing of optical multilayers: theory

A single optical technique is presented that allows direct and selective probing or imaging in the thickness of multilayers. It is based on tunable interferences of polarized light. Adequate vertical resolution is provided with this method.

One‐dimensional variational (1‐D Var) retrieval of temperature, water vapor, and a reference pressure from radio occultation measurements: A sensitivity analysis

A 1‐D Var retrieval study of simulated radio occultation measurements is presented. Temperature and a water vapor profile are retrieved along with a reference pressure to generate the pressure profile by applying the hydrostatic equation. High‐resolution European Center for Medium‐Range Weather Forecasts (ECMWF) atmospheric fields are used by a ray tracing tool to calculate the exact positions of the tangent point. The 1‐D atmospheric profiles following the calculated tangent point trajectory in the 3‐D ECMWF fields are used to simulate bending angle measurements with a 1‐D forward model. Assimilation of these bending angles in a 1‐D Var tool employing the same 1‐D forward model is performed. We analyze the sensitivity of the retrieval to changes in vertical resolution, horizontal smearing of the tangent point trajectory, and the assumption of hydrostatic equilibrium for a nonvertical atmospheric scan. We find that retrievals calculated without adequate vertical resolution can have significant errors in temperature and water vapor. Errors in the retrieval by assuming hydrostatic equilibrium for a nonvertical scan generally cause only minor errors in the retrieved profiles. A study into the occurrence of rays curving down toward the Earth surface indicates that about 5–10% of the profiles could experience so‐called critical refraction at altitudes between 0.5 km and 2 km in case of the applied high‐resolution ECMWF data.

Improved retrieval of tropospheric temperatures from remote measurements of thermal radiation using the adiabatic lapse rate as a constraint

Space-borne radiometers now form an important part of the global network of atmospheric observing systems which provide data for weather forecasting and studies of climate change. However, achieving adequate vertical resolution remains a problem, particularly for the retrieval of profiles of temperature and of water-vapour concentrations in the troposphere. The problem of retrieving these profiles from radiance measurements is ill-posed in that there is no unique answer-solutions may be unstable and excessively sensitive to measurement noise. A technique known as regularization may be used to stabilize the solution by biasing the retrieved profiles toward an acceptable form. Similar inverse problems occur in many areas of science and engineering. Work on image enhancement has shown that regularization which includes a constraint, such as non-negativity of the solution, can provide retrievals with improved accuracy over other regularization methods. We note that the adiabatic lapse rate provides an effective constraint on tropospheric temperature profiles and we exploit this to develop a regularization scheme for the retrieval of atmospheric temperatures. We demonstrate that the retrieved profiles are indeed more accurate than those obtained without this constraint.

Wave CISK of Equatorial Waves and the Vertical Distribution of Cumulus Heating

Abstract The dependence of Kelvin and Rossby wave CISK (conditional instability of the second kind) on the vertical distribution of cumulus heating is examined by expanding the vertical heating profile into its Fourier series with Fourier coefficients f1, f2, . . . , fN. In the standard analysis presented, N = 8 is used. The use of eight Fourier terms provides an adequate vertical resolution considering the current state of knowledge of the dependence of cumulus heating profiles on environmental conditions. The results of the analyses are illustrated in the stability diagrams in the parameter space of Fourier coefficients, showing regions of stability and instability. These results show that all Kelvin wave solutions are stable when the heating parameter e is smaller than a critical value ec, the precise value of which depends on how the Fourier coefficients, fn, decrease with n. For moderately large values of the heating parameter (say, for e ≥ 2), Kelvin wave solutions become unstable for sufficiently n...

Retrieval of Atmospheric Temperatures in the Martian Planetary Boundary Layer Using Upward-Looking Infrared Spectra

We present an algorithm for the retrieval of temperature in the planetary boundary layer (lowest few kilometers) of the martian atmosphere using upward-looking infrared spectra from a Mars lander. Temperature profiles retrieved from an orbiting or passing spacecraft do not have adequate vertical resolution to provide significant information within the planetary boundary layer. By using spectra taken from a surface lander looking upward toward zenith, and by transforming to a vertical coordinate that “stretches out” the atmosphere just above the surface where the contribution to the observed radiation peaks, we find that an efficient algorithm can be formulated with adequate vertical resolution to successfully retrieve temperature profiles that exhibit the major features of the diurnal cycle of planetary boundary layer temperatures. We expect that this technique can be extended to simultaneously retrieve the opacity, and possibly the scattering properties, of atmospheric aerosols as well. Although no upward-looking martian infrared spectra yet exist, demonstration of the abilities of a lander-based infrared spectrometer is important for the planning of future missions to Mars.

Seismic Imaging a Carbonate Reservoir: The Paris Basin Dogger: ABSTRACT

Within the Dogger project, seven partners joined forces (CGG, DHYCA, EAP, ESSO-REP, IFP, TOTAL, TRITON France) to develop an appropriate seismic acquisition, processing and interpretation methodology in order to improve the description of the main oil reservoir (30 m) lying at the top of the Dogger carbonates in the Paris Basin, at a depth of 1900 m. High-resolution 2D Vibroseismic is used to record high frequencies (up to 100 Hz) at the level of the target, and provides sufficiently adequate vertical resolution for the reflections at the top and at the base of the reservoir not to interfere. The upper frequency content of the 3D seismic (70 Hz) is more difficult to enhance. Yet the essential contribution made by the 3D is to evidence, via horizon attributes, sub-meridian lineaments corresponding to faults with throw of several meters which is too weak to be detected on vertical sections. The distribution of these faults, via which water tends to invade the reservoir, and the organization of the amplitudes at the top reservoir reflector, which seems to suggest lateral variations in porosity, are a valuable guide for setting up wells. Three-component seismic (2D-3c) and S-wave emissions did not produce any reflections beyond 30more » Hz at the level of the target which is a poor reflector (PS & SS). Only borehole seismic (VSP, offset VSP), where high frequencies are much less attenuated than with surface seismic, provides detailed imaging of the reservoir in converted mode (up to 110 Hz in PP and in PS). The combination of a continuous spatial sampling, such as that obtained in 3D, and of a Vibroseis emission adapted to frequency attenuation, such as that used in 2D, can supply useful information about the thin and discontinuous Dogger reservoir which cannot he provided by mere correlation of the borehole data.« less

Simulations of the February 1979 Stratospheric Sudden Warming: Model Comparisons and Three-Dimensional Evolution

The evolution of the stratospheric flow during the major stratospheric sudden warming of February 1979 is studied using two primitive equation models of the stratosphere and mesosphere. The United Kingdom Meteorological Office Stratosphere-Mesosphere Model (SMM) uses log pressure as a vertical coordinate. A spectral, entropy coordinate version of the SMM (entropy coordinate model, or ECM) that has recently been developed is also used. Both models produce similar successful simulations through the peak of the warming, capturing the splitting of the vortex and the development of small-scale structures, such as narrow baroclinic zones. The ECM produces a more realistic recombination and recovery of the polar vortex in the midstratosphere after the warming, due mainly to better conservation properties for Rossby-Ertel potential vorticity in this model. Another advantage of the ECM is the automatic increase in vertical resolution near baroclinic zones. Comparison of SMM simulations with forecasts performed using the University of California, Los Angeles general circulation model confirms the previously noted sensitivity of stratospheric forecasts to tropospheric forecast and emphasizes the importance of adequate vertical resolution in modeling the stratosphere. The ECM simulators provide a schematic description of the three-dimensional evolution of the polar vortex and the motion of air through it. During the warming, the two cyclonic vortices till westward and equatorward with height. Strong upward velocities develop in the lower stratosphere on the west (cold) side of a baroclinic zone as it forms over Europe and Asia. Strong downward velocities appear in the upper stratosphere on the east (warm) side, strengthening the temperature gradients. After the peak of the warming, vertical velocities decrease, downward velocities move into the lower stratosphere, and upward velocities move into the upper stratosphere. Transport calculations show that air with high ozone mixing ratios is advected toward the pole from low latitudes during the warming, and air with low ozone mixing ratios is transported to the midstratosphere from both higher and lower altitudes along the baroclinic zone in the polar regions. Trajectories of parcels moving around the vortex oscillate up and down as they move through regions of ascending and descending motions, with an overall increase in pressure in the polar regions. Tracer transport and trajectory calculations show enhanced diabatic descent in the region between cyclone and anticyclone during the warming, consistent with the temperature structure shown.

単板カラーカメラ用垂直偽色信号抑圧方式

To improve the picture quality of single-chip CCD color video cameras with line-sequential color difference signal systems, a new method of vertical false-color-signal reduction is proposed that uses the correlation of the ratio between color difference signals and luminance signals in a localized picture area and reduces the vertical false-color-signal Generally, the optical low-pass-filter is used to reduce the horizontal false-color-signal, however it is not useful to reduce the vertical false-color-signal because adequate vertical resolution cannot be obtained. Our method can reduce the vertical false-color-signal without the optical low-pass-filter Computer simulation is used to examine and verify the fundamental functions of our method It is also used to examine such things as the number of lines required for interpolation processing and to optimize operational precision.

Estimation of regional evaporation for a tallgrass prairie from measurements of properties of the atmospheric boundary layer

Regional scale latent heat flux (LE) was estimated from rawinsonde soundings of the planetary boundary layer (PBL) over the Konza tailgrass prairie in July 1986. Two approaches were used to calculate LE: similarity theory and an algebraic solution of a conservation equation for water vapor in the PBL. Nine of the soundings were complete. However, the latter five soundings only recovered data for every sixth possible level. The results were compared with estimates made by an array of nine Bowen Ratio surface stations. Similarity theory, using vertically averaged values, produced estimates that were reasonably close to the surface values. However, the use of values at the top of the PBL resulted in large overestimation of the evaporation fluxes. When complete soundings were available, the conservation equation yielded estimates which agreed very well with surface values. The agreement was reduced for incomplete soundings. This is likely related to the sensitivity of the equation to uncertainties in the height of the inversion. Overall, the conservation equation produced estimates in closest agreement with the surface stations. The results suggest that adequate vertical resolution of measured profiles is important for proper estimation of regional surface fluxes.

Tomographic resolution of mesoscale eddies in the marginal ice zone: A preliminary study

The adequacy of ocean acoustic tomography to resolve mesoscale eddies in the marginal ice zones (MIZ) in the vertical plane containing the acoustic multipaths connecting a pair of transceivers is studied using simulation inversions based on realistic eddy profiles obtained from conductivity‐temperature‐depth data. Resolution in this plane is seen to be strongly dependent upon the characteristics of the sound channel. For optimal, minimum mean square error estimators, resolution is directly related to accuracy, with better resolution implying higher accuracy. For unaided acoustic tomography (i.e., no supplementary measurements) using only non‐bottom‐interacting paths, horizontal and vertical resolution lengths of the order of 40 km and 200 m, respectively, are found in the upper water column for a transmission range of 150 km. The implication is that the horizontal resolution is marginally adequate to resolve MIZ eddies but the vertical resolution is not, since the horizontal scale of the eddies is of the same order whereas the vertical scale is much shorter. The incorporation of bottom‐reflected arrivals is found to improve resolution significantly. However, the improvement only occurs in the horizontal direction and saturates when more than 14 of these arrivals are included. Beyond this point, additional travel time observations give mostly redundant information. On the other hand, the disappearance of less stable non‐bottom‐interacting ray paths can result in a significant loss of resolution, but only vertically. The deficiency in vertical resolution is a result of the upward refracting nature of the MIZ sound channel. It is also demonstrated that the inclusion of point temperature measurements on the acoustic transceiver moorings can dramatically increase the vertical resolution of the overall system, particularly within a horizontal correlation length of the mooring. With the inclusion of satellite radiometry surface temperature measurements, adequate vertical resolution is achieved over the entire range considered.