Vertical Velocity Field Research Articles

Three-dimensional spatiotemporal wind field reconstruction based on physics-informed deep learning

In this work, a physics-informed deep learning model is developed to achieve the reconstruction of the three-dimensional (3-D) spatiotemporal wind field in front of a wind turbine, by combining the 3-D Navier–Stokes equations and the scanning LIDAR measurements. To the best of the authors’ knowledge, this is for the first time that the full 3-D spatiotemporal wind field reconstruction is achieved based on real-time measurements and flow physics. The proposed method is evaluated using high-fidelity large eddy simulations. The results show that the wind vector field in the whole 3-D domain is predicted very accurately based on only scalar line-of-sight LIDAR measurements at sparse locations. Specifically, at the baseline case, the prediction errors for the streamwise, spanwise and vertical velocity fields are 0.263 m/s, 0.397 m/s and 0.361 m/s, respectively. The prediction errors for the horizontal and vertical direction fields are 2.84° and 2.58° which are important in tackling yaw misalignment and turbine tilt control, respectively. Further analysis shows that the 3-D wind features are captured clearly, including the evolutions of flow structures, the wind shear in vertical direction, the blade-level speed variations due to turbine rotation, and the speed variations modulated by the turbulent wind. Also, the developed model achieves short-term wind forecasting without the commonly-used Taylor’s frozen turbulence hypothesis. Furthermore it is very useful in advancing other wind energy research fields e.g. wind turbine control & monitoring, power forecasting, and resource assessments because the 3-D spatiotemporal information is important for them but not available with current sensor and prediction technologies.

Convective and Turbulent Motions in Nonprecipitating Cu. Part I: Method of Separation of Convective and Turbulent Motions

AbstractAtmospheric motions in clouds and cloud surroundings have a wide range of scales, from several kilometers to centimeters. These motions have different impacts on cloud dynamics and microphysics. Larger-scale motions (hereafter referred to as convective motions) are responsible for mass transport over distances comparable with cloud scale, while motions of smaller scales (hereafter referred to as turbulent motions) are stochastic and responsible for mixing and cloud dilution. This distinction substantially simplifies the analysis of dynamic and microphysical processes in clouds. The present research is Part I of the study aimed at describing the method for separating the motion scale into a convective component and a turbulent component. An idealized flow is constructed, which is a sum of an initially prescribed field of the convective velocity with updrafts in the cloud core and downdrafts outside the core, and a stochastic turbulent velocity field obeying the turbulent properties, including the −5/3 law and the 2/3 structure function law. A wavelet method is developed allowing separation of the velocity field into the convective and turbulent components, with parameter values being in a good agreement with those prescribed initially. The efficiency of the method is demonstrated by an example of a vertical velocity field of a cumulus cloud simulated using the System for Atmospheric Modeling (SAM) with bin microphysics and resolution of 10 m. It is shown that vertical velocity in clouds indeed can be represented as a sum of convective velocity (forming zone of cloud updrafts and subsiding shell) and a stochastic velocity obeying laws of homogeneous and isotropic turbulence.

Intermittent Frontogenesis in the Alboran Sea

AbstractWe present a phenomenological description and dynamical analysis of the Alboran fronts using a realistic simulation at submesoscale resolution. The study is focused on east Alboran fronts emerging within relatively strong flows that separate from the Spanish coast into the basin interior. Despite modest lateral shifting associated with the position of the Alboran anticyclonic gyres and variations in intensity, these fronts present a similar structure and dynamical configuration as the climatological Almeria–Oran front. The statistical analysis of our solution shows that strained-induced frontogenesis is a recurrent submesoscale mechanism associated with these fronts, and the process is assessed in terms of the advective Lagrangian frontogenetic tendencies associated with buoyancy and velocity horizontal gradients. Intermittency in their strength and patterns is indicative of high variability in the occurrence of active frontogenesis in association with the secondary (overturning) circulation across the frontal gradient. As a result, we find many episodes with strong surface fronts that do not have much associated downwelling. Frontogenesis and the associated secondary circulation are further explored during two particular frontal events, both showing strong downwelling of (1) cm s−1 extending down into the pycnocline. A frontogenetic contribution of turbulent vertical momentum mixing to the secondary circulation is identified in the easternmost region during the cold season, when the dynamics are strongly influenced by the intrusion of the salty Northern Current. The background vertical velocity fields observed during the analyzed events indicate other currents in the submesoscale range, including tidal and topographic internal waves.

Towards an Understanding of the Structure of Jupiter’s Atmosphere using the Ammonia Distribution and the Transformed Eulerian Mean Theory

AbstractThe structure and stability of Jupiter’s atmosphere is analyzed using transformed Eulerian mean (TEM) theory. Utilizing the ammonia distribution derived from microwave radiometer measurements of the Juno orbiter, the latitudinal and vertical distribution of the vertical velocity in the interior of Jupiter’s atmosphere is inferred. The resulting overturning circulation is then interpreted in the TEM framework to offer speculation of the vertical and meridional temperature distribution. In the extratropics, the analyzed vertical velocity field shows Ferrel-cell-like patterns associated with each of the jets. A scaling analysis of the TEM overturning circulation equation suggests that in order for the Ferrel-cell-like patterns to be visible in the ammonia distribution, the static stability of Jupiter’s weather layer should be on the order of 1 × 10−2 s−1. In the tropics, the ammonia distribution suggests strong upward motion which is reminiscent of the rising branch of the Hadley cell where the static stability is weaker. Taken together, the analysis suggests that the temperature lapse rate in the extratropics is markedly greater than that in the tropics. Because the cloud top temperature is nearly uniform across all latitudes, the analysis suggests that in the interior of the weather layer, there could exist a temperature gradient between the tropical and extratropical regions.

GPS Imaging of Vertical Bedrock Displacements: Quantification of Two‐Dimensional Vertical Crustal Deformation in China

AbstractThe Global Positioning System (GPS) derived bedrock displacements respond to multiple geophysical effects, ranging from surface elastic loads to tectonic sources or viscoelastic uplifts stemming from Earth’s viscous mantle. In this study, the GPS‐inferred vertical crustal velocities are rigorously estimated in mainland China. We integrate the GPS vertical velocity field with Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow‐On (GFO) data, adopting an empirical Spatial Structure Function (SSF), to image tectonic deformation in mainland China with respect to the International Terrestrial Reference Frame (ITRF) 2014. We present four profiles across China, which indicate that our new robust results are superior to kriging. Furthermore, we use the GRACE/GFO products to account for elastic deformation due to surface mass changes to isolate tectonic deformation signals at GPS sites within mainland China from 2002 to 2019. By integrating GPS and GRACE/GFO measurements, our results reveal the long‐term spatial patterns of vertical tectonic motion in different blocks in mainland China. We conclude that significant steep velocity gradients occur at tectonic block boundaries that are attributable to locking and elastic strain accumulation on active block boundary faults.

Comparison of Atmospheric Vertical Motion over China in ERA-Interim, JRA-55, and NCEP/NCAR Reanalysis Datasets

Vertical motion is an important feature of the atmosphere, being closely linked to clouds and precipitation. Here, we present a comparison of the vertical velocity of air over China, with particular focus on the Tibetan Plateau, during the period 1981–2010 using three reanalysis datasets: ERA-Interim, JRA-55 and NCEP/NCAR. Analysis methods including empirical orthogonal functions analysis and correlation analysis were used to examine consistency between the datasets and their suitability in research and application in China. Our results show that the vertical velocity fields from ERA-Interim and JRA-55 are more consistent than they are with those from NCEP/NCAR. The atmospheric vertical velocity fields from NCEP/NCAR lack details compared with those obtained from ERA-Interim and JRA-55, and part of values for the upper troposphere over the ocean south of 15°N are contrary to the other datasets and the climatic reality. Therefore, use of ERA-Interim or JRA-55 may be preferable over NCEP/NCAR. The intensity of atmospheric vertical motion in the lower troposphere in JRA-55 is significantly higher than in ERA-Interim and NCEP/NCAR. In summer, the JRA-55 data are closest to the observed wind fields and the data stability best for the Tibetan Plateau region. Our results provide guidance for better application of reanalysis data and more accurate climate prediction for this region.

Reduced-order representation of stratified wakes by proper orthogonal decomposition utilizing translational symmetry

Visualizations of reduced-order representations of stratified wakes of Reynolds number $$Re \in \{5,25,100\}\times 10^3$$ are presented at a fixed internal Froude number. The reduced-order representations are constructed by applying proper orthogonal decomposition (POD) to numerical datasets that are high-resolution, three-dimensional and time-dependent. Due to the transient nature of the flow, the dynamics to be represented are highly non-stationary, posing a challenge for the effectiveness of POD. The translational symmetry inherent in the computational configuration is utilized for the POD analysis. This technique turns out to be effective in terms of improving the convergence of energy content represented by the POD modes and enhancing the interpretability of the temporal dynamics. Individual POD modes representing distinct dynamics of various scales are visualized. In the turbulent region, visualizations of the reconstructed vertical vorticity fields suggest that the dominant length scale of flow structures decreases with the modal index. For internal wave motions, visualizations of the reconstructed vertical velocity fields show the opposite trend, as the wavelength of internal waves observed in the wake’s ambient increases with the modal index. The temporal coefficients for a given mode are observed to vary minimally between $$Re = 2.5\times 10^4$$ and $$10^5$$ , suggesting a potential asymptote of the large-scale temporal dynamics in terms of Reynolds number.

Stepwise transitions in spin-up of rotating Rayleigh–Bénard convection

Abstract

Lightning Data Assimilation Scheme in a 4DVAR System and Its Impact on Very Short-Term Convective Forecasting

AbstractA proof-of-concept method for the assimilation of total lightning observations in the 4DVAR framework is proposed and implemented into the Variational Doppler Radar Analysis System (VDRAS). Its performance is evaluated for the very short-term precipitation forecasts of a localized convective event over northeastern China. The lightning DA scheme assimilated pseudo-observations for vertical velocity fields derived from observed total lightning rates and statistically computed vertical velocity profile from VDRAS analysis data. To reduce representative errors of the derived vertical velocity, a distance-weighted horizontal interpolation is applied to the input data prior to the DA. The case study reveals that although 0–2-h precipitation nowcasts are improved by assimilating lightning data alone compared to CTRL (no radar or lightning) and RAD (radar only), better results are obtained when the lightning data are assimilated with radar data simultaneously. The assimilation of both data sources results in improved dynamical consistency with enhanced updraft and latent heat as well as improved moisture distributions. Additional experiments are conducted to evaluate the sensitivity of the combined DA scheme to varied vertical velocity profiles, radii of horizontal interpolation, binning time intervals, and relationships used to estimate the maximum vertical velocity from lightning flash rates. It is shown that the scheme is robust to these variations with both radar and lightning assimilated data.

An Assessment of Global Positioning System Velocity Uncertainty in California

AbstractWe analyze data from 580 continuous global positioning system (GPS) stations in California to quantify differences in published velocity estimates from five analysis centers. Horizontal and vertical rates for individual stations can differ up to 5 mm/yr, with systematic differences in some areas comparable to deformation rates. Published velocity uncertainties vary between analysis centers and are systematically underreported in the horizontal relative to empirical uncertainties calculated from the scatter of analysis center velocities. In the vertical, published velocity uncertainties are both over and underreported and vary more widely between centers. An interpolated ensemble vertical velocity field shows high‐subsidence regions in the Central Valley and Salton Trough have the largest empirical uncertainties, while station density has a modest impact on uncertainties. Applications that rely on subcentimeter GPS accuracy should consider the possibility that formal errors published with velocity rate estimates understate true velocity uncertainties in both the horizontal and vertical.

The contemporary strain rate field in Uruguay and surrounding region – vertical velocities

This study supplements analyses of the horizontal strain rate fields in the region in and around Uruguay presented in Baxter and Smith (2020). Whilst the original study did not consider the vertical component, because of high levels of noise and discontinuities in the raw data, these effects have been minimized and appropriate analyses are presented with consideration of the uncertainties. The results show that, similarly to the horizontal strain rate field, the vertical velocity field in the region appears to have been influenced by two subduction earthquakes that occurred in Chile. The patterns of uplift and subsidence revealed by these analyses suggest influences from the underlying structure of the Rio de la Plata estuary, and perhaps the Mesopotamian region in Argentina, that may relate to enhanced seismicity in these specific areas.

Ground Deformation and Its Causes in Abbottabad City, Pakistan from Sentinel-1A Data and MT-InSAR

Land subsidence, as one of the engineering geological problems in the world, is generally caused by compression of unconsolidated strata due to natural or anthropogenic activities. We employed interferometric point target analysis (IPTA) as a multi-temporal interferometric synthetic aperture radar (MT-InSAR) technique on ascending and descending Sentinel-1A the terrain observation with progressive scans SAR (TOPSAR) images acquired between January 2015 and December 2018 to analyze the spatio-temporal distribution and cause of subsidence in Abbottabad City of Pakistan. The line of sight (LOS) average deformation velocities along ascending and descending orbits were decomposed into vertical velocity fields and compared with geological data, ground water pumping schemes, and precipitation data. The decomposed and averaged vertical velocity results showed significant subsidence in most of the urban areas in the city. The most severe subsidence was observed close to old Karakorum highway, where the subsidence rate varied up to −6.5 cm/year. The subsidence bowl profiles along W–E and S–N transects showed a relationship with the locations of some water pumping stations. The monitored LOS time series histories along an ascending orbit showed a close correlation with the rainfall during the investigation period. Comparative analysis of this uneven prominent subsidence with geological and precipitation data reflected that the subsidence in the Abbottabad city was mainly related to anthropogenic activities, overexploitation of water, and consolidation of soil layer. The study represents the first ever evidence of land subsidence and its causes in the region that will support the local government as well as decision and policy makers for better planning to overcome problems of overflowing drains, sewage system, littered roads/streets, and sinking land in the city.

Present‐Day Crustal Vertical Velocity Field for the Contiguous United States

AbstractThe study of vertical crustal motion in the contiguous United States (CONUS) has traditionally focused on the high‐amplitude deformation caused by glacial isostatic adjustment. To better understand more subtle vertical crustal motion resulting from other geophysical processes, we take advantage of the ongoing expansion of continuous Global Positioning System (GPS) networks, whose geodetic observations provide ever‐increasing accuracy and spatial resolution of surface deformation. Using position data for 2,782 GPS stations operating between 2007 and 2017, we produce a new vertical crustal velocity field for the CONUS region. We estimate our own station velocities to ensure consistent treatment of time series outliers, noise, and offsets, and we use adaptive smoothing and interpolation to account for spatially varying station density. Our velocity field reveals spatially coherent vertical features that are representative of regional tectonics, hydrologic, and anthropogenic processes. By removing the effects of modeled glacial isostatic adjustment and hydrologic loading estimated from Gravity Recovery and Climate Experiment (GRACE) data, we reduce the variance in our velocity field by36%and show residuals potentially due to geocenter motion and underlying tectonics.

On resolution sensitivity in the Community Atmosphere Model

AbstractAdvances in high‐performance computing make it possible to run atmospheric general circulation models (AGCMs) over an increasingly wider range of grid resolutions, using either globally uniform or variable‐resolution grids. In principle, this is an exciting opportunity to resolve atmospheric process and scales in a global model and in unprecedented detail, but in practice this grid flexibility is incompatible with the non‐ or weakly converging solutions with increasing horizontal resolution that have long characterized AGCMs. In the the Community Atmosphere Model (CAM), there are robust sensitivities to horizontal resolution that have persisted since the model was first introduced over thirty years ago; the atmosphere progressively dries and becomes less cloudy with resolution, and parametrized deep convective precipitation decreases at the expense of stratiform precipitation. This study documents a convergence experiment using CAM, version 6, and argues that a unifying cause, the sensitivity of resolved dynamical modes to native grid resolution, feeds back into other model components and explains these robust sensitivities to resolution. The increasing magnitudes of resolved vertical velocities with resolution are shown to fit an analytic scaling derived for the equations of motion at hydrostatic scales. This trend in vertical velocities results in an increase in resolved upward moisture fluxes at cloud base, balanced by an increase in stratiform precipitation rates with resolution. Compensating, greater magnitude subsiding motion with resolution has previously been shown to dry out the atmosphere and reduce cloud cover. Here, it is shown that both the increase in condensational heating from stratiform cloud formation and greater subsidence drying contribute to an increase in atmospheric stability with resolution, reducing the activity of parametrized convection. The impact of changing the vertical velocity field with native grid resolution cannot be ignored in any effort to recover convergent solutions in AGCMs, and, in particular, the development of scale‐aware physical parametrizations.

Airborne measurements and large-eddy simulations of small-scale gravity waves at the tropopause inversion layer over Scandinavia

Abstract. Coordinated airborne measurements were performed by two research aircraft – Deutsches Zentrum für Luft- und Raumfahrt (DLR) Falcon and High Altitude and Long Range Aircraft (HALO) – in Scandinavia during the GW-LCYCLE II (Investigation of the life cycle of gravity waves) campaign in 2016 to investigate gravity wave processes in the upper troposphere and lower stratosphere (UTLS) region. A mountain wave event was probed over southern Scandinavia on 28 January 2016. The collected dataset constitutes a valuable combination of in situ measurements and horizontal- and altitude-resolved Doppler wind lidar and water vapour measurements with the differential absorption lidar (DIAL). In situ data at different flight altitudes and downward-pointing wind lidar measurements show pronounced changes of the horizontal scales in the vertical velocity field and of the leg-averaged momentum fluxes (MFs) in the UTLS region. The vertical velocity field was dominated by small horizontal scales with a decrease from around 20 to < 10 km in the vicinity of the tropopause inversion layer (TIL). These small scales were also found in the water vapour data and backscatter data of the DIAL. The leg-averaged MF profile determined from the wind lidar data is characterized by a pronounced kink of positive fluxes in the TIL and negative fluxes below. The largest contributions to the MF are from waves with scales > 30 km. The combination of the observations and idealized large-eddy simulations revealed the occurrence of interfacial waves having scales < 10 km on the tropopause inversion during the mountain wave event. The contribution of the interfacial waves to the leg-averaged MF is basically zero due to the phase relationship of their horizontal and vertical velocity perturbations. Interfacial waves have already been observed on boundary-layer inversions but their concept has not been applied to tropopause inversions so far. Our idealized simulations reveal that the TIL affects the vertical trend of leg-averaged MF of mountain waves and that interfacial waves can occur also on tropopause inversions. Our analyses of the horizontal- and altitude-resolved airborne observations confirm that interfacial waves actually do occur in the TIL. As predicted by linear theory, the horizontal scale of those waves is determined by the wind and stability conditions above the inversion. They are found downstream of the main mountain peaks and their MF profile varies around zero and can clearly be distinguished from the MF profile of Kelvin–Helmholtz instability. Further, the idealized large-eddy simulations reveal that the presence of the TIL is crucial in producing this kind of trapped wave at tropopause altitude.

Present‐Day and Long‐Term Uplift Across the Western Transverse Ranges of Southern California

AbstractIt has been known for decades that the present‐day shortening rates across the Western Transverse Ranges (WTR) in Southern California are rapid, reaching 10–15 mm/year near the heavily populated Los Angeles area. However, only recently have geodetic measurements of vertical motion in the WTR been sufficiently dense to resolve a tectonic vertical signal. In this study, we show that much of the geodetically derived vertical velocity field in the WTR can be attributed to the interseismic signal of strain accumulation on reverse faults. We invert geodetic and geologic data for slip rate and interseismic coupling on faults using a kinematic model consisting of faults embedded in an elastic crust over an inviscid mantle. This method allows us to infer the permanent, long‐term component of vertical motions from recoverable, short‐term motions. We infer that much of the geodetically observed 3–4 mm/year of differential vertical motion across the WTR, involving subsidence along the Santa Barbara coastline and uplift of the Santa Ynez Range, can be attributed to recoverable elastic deformation associated with interseismic locking on faults dipping under the WTR. The sum of dip‐slip rates across the WTR decreases from 10.5–14.6 mm/year on the east side near Ventura, California to 5–6.2 mm/year across the western side of the Santa Barbara Channel. The total moment accumulation rate in both the Santa Barbara Channel and the combined San Fernando Valley‐LA Basin regions is equivalent to about two Mw = 7 earthquakes every 100 years.

Characteristics of Winter Haze Pollution in the Fenwei Plain and the Possible Influence of EU During 1984–2017

AbstractDuring the past few years, air pollution in the Fenwei Plain (FWP) region had obviously rebounded. In this study, we used quantitative analysis, difference analysis, and correlation analysis methods to analyze the temporal and spatial distribution and the influence of the meteorological and climatic factors on haze pollution in FWP. The results showed that on the long‐term timescale, the haze pollution had an overall upward trend during the winter of 1984–2017, and the pollution became more serious after 2000. In addition, the differences in meteorological parameters such as relative humidity, sea level pressure, temperature, vertical velocity, and wind fields near the surface between the regional haze days and the regional clean days were remarkable, indicating that the changes in these meteorological parameters had a distinct impact on haze pollution. Among several atmospheric circulations in the Northern Hemisphere mid‐high latitudes, Eurasian (EU) pattern had the most obvious influence on haze pollution via two possible pathways: First, on the interannual timescale, the evolution of EU pattern affected the changes of Siberian high and Aleutian low pressure; second, changes in EU pattern could result in changes in wind speed at 850 hPa, boundary layer height and relative humidity in the lower troposphere. All these findings may provide some help for the government to take prevention measures for haze pollution in FWP.

On the Vertical Velocity and Nutrient Delivery in Warm Core Rings

AbstractWe examine various contributions to the vertical velocity field within large mesoscale eddies by analyzing multiple solutions to an idealized numerical model of a representative anticyclonic warm core Gulf Stream ring. Initial conditions are constructed to reproduce the observed density and nutrient profiles collected during the Warm Core Rings Program. The contributions to vertical fluxes diagnosed from the numerical simulations are compared against a divergence-based, semidiagnostic equation and a generalized omega equation to better understand the dynamics of the vertical velocity field. Frictional decay alone is found to be ineffective in raising isopycnals and transporting nutrients to the upper ocean. With representative wind forcing, the magnitude of vorticity gradient–induced Ekman pumping is not necessarily larger than the current-induced counterpart on a time scale relevant to ecosystem response. Under realistic forcing conditions, strain deformation can perturb the ring to be noncircular and induce vertical velocities much larger than the Ekman vertical velocities. Nutrient budget diagnosis, together with analysis of the relative magnitudes of the various types of vertical fluxes, allows us to describe the time-scale dependence of nutrient delivery. At time scales that are relevant to individual phytoplankton (from hours to days), the magnitudes of nutrient flux by Ekman velocities and deformation-induced velocities are comparable. Over the life span of a typical warm core ring, which can span multiple seasons, surface current–induced Ekman pumping is the most effective mechanism in upper-ocean nutrient enrichment because of its persistence in the center of anticyclones regardless of the direction of the wind forcing.

Coherence of temperature and velocity superstructures in turbulent Rayleigh–Bénard flow

We investigate the interplay between large-scale patterns, so-called superstructures, in the fluctuation fields of temperature $\unicode[STIX]{x1D703}$ and vertical velocity $w$ in turbulent Rayleigh–Benard convection at large aspect ratios. Earlier studies suggested that velocity superstructures were smaller than their thermal counterparts in the centre of the domain. However, a scale-by-scale analysis of the correlation between the two fields employing the linear coherence spectrum reveals that superstructures of the same size exist in both fields, which are almost perfectly correlated. The issue is further clarified by the observation that, in contrast to the temperature, and unlike assumed previously, superstructures in the vertical-velocity field do not result in a peak in the power spectrum of $w$ . The origin of this difference is traced back to the production terms of the $\unicode[STIX]{x1D703}$ and $w$ variance. These results are confirmed for a range of Rayleigh numbers $Ra=10^{5}{-}10^{9}$ ; the superstructure size is seen to increase monotonically with $Ra$ . Furthermore, the scale distribution of the temperature fluctuations in particular is pronouncedly bimodal. In addition to the large-scale peak caused by the superstructures, there exists a strong small-scale peak. This ‘inner peak’ is most intense at a distance of $\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D703}}$ from the wall and is associated with structures of size ${\approx}10\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D703}}$ , where $\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D703}}$ is the thermal boundary layer thickness. Finally, based on the vertical coherence relative to a reference height of $\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D703}}$ , a self-similar structure is identified in the velocity field (vertical and horizontal components) but not in the temperature.

Study on the Structure of a Horizontal Shear Line over the Tibetan Plateau Based on CRA-Interim Datasets and Its Comparison with ERA-Interim Datasets

The CRA-Interim trial production of the global atmospheric reanalysis for 10 years from 2007 to 2016 was carried out by the China Meteorological Administration in 2017. The structural characteristics of the horizontal shear line over the Tibetan Plateau (TPHSL) based on the CRA-Interim datasets are examined by objectively identifying the shear line, and are compared with the analysis results of the European Centre for Medium-Range Weather Forecasts reanalysis data (ERA-Interim). The case occurred at 18UTC on July 5, 2016. The results show that both of the ERA-Interim and CRA-Interim datasets can well reveal the circulation background and the dynamic and thermal structure characteristics of TPHSL, and they have shown some similar features. The middle and high latitudes at 500 hPa are characterized by the circulation situation oftwo troughs and two ridges, and at 200 hPa, the TPHSL is located in the northeast quadrant of the South Asian High Pressure (SAHP). The TPHSL locates in the positive vorticity zone and passes through the positive vorticity center corresponding to the ascending motion. Near the TPHSL, the contours of pseudo-equivalent potential temperature (θse) tend to be intensive, with a high-value center on the south side of the TPHSL. The TPHSL can extend to 460 hPa and vertically inclines northward. There is a positive vorticity zone near the TPHSL which is also characterized by the northward inclination with the height, the ascending motion near the TPHSL can extend to 300 hPa, and the atmospheric layer above the TPHSL is stable. However, the intensities of the TPHSL's structure characteristics analyzed with the two datasets are different, revealing the relatively strong intensity of geopotential height field, vertical velocity field, vorticity field and divergence field from the CRA-Interim datasets. In addition, the vertical profiles of the dynamic and water vapor thermal physical quantities of the two datasets are also consistent in the east and west part of the TPHSL. In summary, the reliable and usable CRA-Interim datasets show excellent properties in the analysis on the structural characteristics of a horizontal shear line over the Tibetan Plateau.