Vertical Profiles Of Horizontal Wind Research Articles

Filling the Gap of Wind Observations Inside Tropical Cyclones

AbstractThe WIVERN (WInd VElocity Radar Nephoscope) mission, currently under the Phase‐0 of the ESA Earth Explorer program, promises to provide new insight in the coupling between winds and microphysics by globally observing, for the first time, vertical profiles of horizontal winds in cloudy areas. The objective of this work is to explore the potential of the WIVERN conically scanning Doppler 94 GHz radar for filling the wind observation gap inside tropical cyclones (TCs). To this aim, realistic WIVERN notional observations of TCs are produced by combining the CloudSat 94 GHz radar reflectivity observations from 2007 to 2009 with ECMWF co‐located winds. Despite the short wavelength of the radar (3 mm), which causes strong attenuation in presence of large amount of liquid hydrometeors, the system can profile most of the TCs, particularly the cloudy areas above the freezing level and the precipitating stratiform regions. The statistical analysis of the results shows that, (a) because of its lower sensitivity, a nadir pointing WIVERN would detect 75% of the clouds observed by CloudSat (45% of winds with 3 m s−1 accuracy, in comparison to CloudSat sampling of clouds), (b) but thanks to its scanning capability, WIVERN would actually provide 53 times more observations of clouds than CloudSat in TCs (30 times more observations of horizontal winds), (c) this corresponds to about 350 (200) million observations of clouds (accurate winds) every year. Such observations could be used to shed light on the physical processes underpinning the evolution of TCs and in data assimilation in order to improve numerical weather prediction.

Comparison of horizontal wind observed by wind profiler radars with ERA5 reanalysis data in Anhui, China

The wind profiler radar (WPR) network in Anhui Province in China completed the construction in 2019 to improve the warning capacity for meteorological disasters. To verify its proper performance, vertical profiles of horizontal winds were compared with ERA5 reanalysis data from January to December 2021. The results show that the WPRs demonstrate good capability in measuring atmospheric wind due to their high data collection rate (> 80%). Overall, the data availability of the WPRs decreases with increasing altitude, exceeding 90% below 3 km during the daytime without precipitation. In terms of seasonal variability, the annual mean effective detection height reaches a maximum value at 4–6 km in summer and a minimum value at approximately 2 km in winter. Comparison analyses show that the wind measurements by the WPRs show excellent agreement with the ERA5 zonal (correlation coefficient > 0.89 and standard deviation < 2.57 m/s) and meridional winds (correlation coefficient > 0.76 and standard deviation < 3.26 m/s) over most WPR stations in Anhui, China. Additionally, the biases of winds between WPR and ERA5 generally follow a Gaussian distribution pattern, most of which are all close to zero. In particular, the differences in horizontal wind between WPR and ERA5 increase with altitude, with a much lower bias present in the lower layer. In addition, due to the difference in atmospheric turbulence between day and night, statistical parameters of comparison during daytime behave better than those at night. These findings indicate that the WPR network in Anhui is capable of providing good quality wind data, laying a solid data foundation for the improvement and development of the boundary layer scheme in the future.

Development and Evaluation of a New Urban Parameterization in the Weather Research and Forecasting (WRF) Model

AbstractIn mesoscale Weather Research and Forecasting (WRF) model, several urban‐modeling options exist, such as Single‐layer Urban Canopy Model, Building Effect Parameterization, and Building Energy Model. However, these models have limitations in terms of the choice of land surface models (LSMs) and planetary boundary layer (PBL) schemes, the associated computational expenses, and other constraints. Recently, Dy et al. (2019, https://doi.org/10.1029/2018JD029333) included the urban‐momentum drag effect for wind‐speed modeling by developing a new multilayer model based on a modified nonlocal Asymmetric Convective Model version‐2 (ACM2) PBL scheme. This urban‐based ACM2 (UACM) has demonstrated a significantly improved ability over the base‐ACM2 (BACM) to predict wind speed near the urban ground surface and shown an inflection point at roof level in the vertical profile of horizontal wind. In this study, urban thermal and moisture components are introduced into the Pleim‐Xiu (PX) LSM and coupled with UACM. The diurnal variation in street, walls, and roof‐surface temperatures is modeled using the two‐layer force‐restore algorithm. Simple radiation treatment is considered to account for shadowing on streets based on the solar zenith angle and building morphology. Heat and moisture flux evolution are considered explicitly on all urban surfaces. The advantages of this novel UACM are simple formulation, more efficient execution, and its requirement for only a few fundamental urban morphological parameters. The idealized and real urban data case WRF simulations are performed over the Pearl River Delta region in southern China to test the new UACM. The computationally efficient UACM is expected to perform faster for operational forecasting runs.

Evaluation of global reanalysis winds and high‐resolution regional model outputs with the 205 MHz stratosphere–troposphere wind profiler radar observations

AbstractA stratosphere–troposphere (ST) wind profiler radar operating at a high VHF range (205 MHz) installed at Cochin (10.03°N, 76.33°E), India, provides high‐resolution winds in time and altitude extending from 315 m to 20 km. We evaluated the horizontal and vertical winds obtained from atmospheric global reanalyses (ERA5, ERA‐Interim, MERRA‐2 and NCEP) data and the high‐resolution regional model (WRF) output winds with the ST radar (STR) wind observations at Cochin. The data for one whole year, from 1 August 2018 to 31 July 2019, for 0600 UTC and 1200 UTC were used. Wind data appraisal has been carried out at 24 levels from 315 m to 18.5 km altitude for the reanalyses datasets and 29 levels for model‐simulated winds in different seasons. Vertical profiles of horizontal winds from reanalysis and model‐simulated data somewhat catch the major changes observed from STR. The zonal winds match very well with the STR, whereas meridional winds show moderate similarity. Higher correlations in zonal winds are found during the summer monsoon, whereas meridional winds show apparent likeness during winter. The ERA5, ERA‐Interim, and model‐simulated winds have better agreement with the STR winds. Observed vertical winds from STR displays large fluctuations, while the estimated vertical winds in reanalysis are highly smoothed. Vertical profiles of vertical winds from the reanalysis datasets are not uniform. The reliability of vertical winds in reanalysis and WRF model output values are dubious compared to that of the directly observed winds from STR. The study indicates that improved quality of vertical and meridional winds in reanalysis data is needed by assimilating directly observed data from the available advanced facilities.

A Modeling Study of an Atmospheric Bore Associated With a Nocturnal Convective System Over China

AbstractBores have been shown to play a role in the initiation and maintenance of mesoscale convective systems (MCSs), particularly during the night after the boundary layer stabilizes. To date, the generation, evolution, and structure of bores over China has received little attention. This study utilizes observations and simulations with the WRF‐ARW model to investigate the generation and evolution of an atmospheric bore observed over Yangtze‐Huai Plains of China. The bore was associated with a nocturnal MCS that first formed over elevated terrain. The bore was observed ahead of the MCS with a maximum lateral extension of ~100 km. The feature lasted for over 90 mins and propagated at a speed of ~13 m/s, slightly faster than the MCS. In the simulation, the bore evolved from the separating “head” of the convectively generated gravity current. The bore then continued to propagate ahead of the MCS, even after the dissipation of the feeder current, and took on the appearance of an undular bore. The bore lifted a layer of convectively unstable air above the nocturnal surface inversion, initiating new convection ahead of the MCS to help maintain the MCS. The Scorer parameter ahead of the bore revealed a low‐level wind profile with curvature of the vertical profile of horizontal wind, favoring the trapping of wave energy and the persistence of the bore. These results are generally consistent with the role of bores in the maintenance of nocturnal MCSs and emphasize the need for future studies into the relationship between bores and nocturnal MCSs over China.

Simulation study for measurement of horizontal wind profiles in the polar stratosphere and mesosphere using ground-based observations of ozone and carbon monoxide lines in the 230–250 GHz region

Abstract. Meteorological and atmospheric models are being extended up to 80 km altitude but there are very few observing techniques that can measure stratospheric–mesospheric winds at altitudes between 20 and 80 km to verify model datasets. Here we demonstrate the feasibility of horizontal wind profile measurements using ground-based passive millimetre-wave spectroradiometric observations of ozone lines centred at 231.28, 249.79, and 249.96 GHz. Vertical profiles of horizontal winds are retrieved from forward and inverse modelling simulations of the line-of-sight Doppler-shifted atmospheric emission lines above Halley station (75°37′ S, 26°14′ W), Antarctica. For a radiometer with a system temperature of 1400 K and 30 kHz spectral resolution observing the ozone 231.28 GHz line we estimate that 12 h zonal and meridional wind profiles could be determined over the altitude range 25–74 km in winter, and 28–66 km in summer. Height-dependent measurement uncertainties are in the range 3–8 m s−1 and vertical resolution ∼ 8–16 km. Under optimum observing conditions at Halley a temporal resolution of 1.5 h for measuring either zonal or meridional winds is possible, reducing to 0.5 h for a radiometer with a 700 K system temperature. Combining observations of the 231.28 GHz ozone line and the 230.54 GHz carbon monoxide line gives additional altitude coverage at 85 ± 12 km. The effects of clear-sky seasonal mean winter/summer conditions, zenith angle of the received atmospheric emission, and spectrometer frequency resolution on the altitude coverage, measurement uncertainty, and height and time resolution of the retrieved wind profiles have been determined.

Mesoscale kinematics derived from X‐band Doppler radar observations of convective versus stratiform precipitation and comparison with GPS radiosonde profiles

AbstractSingle Doppler analysis techniques known as velocity azimuth display (VAD) and volume velocity processing (VVP) are used to analyze kinematics of mesoscale flow such as horizontal wind and divergence using X‐band Doppler weather radar observations, for selected cases of convective, stratiform, and shallow cloud systems near tropical Indian sites Pune (18.58°N, 73.92°E, above sea level (asl) 560 m) and Mandhardev (18.51°N, 73.85°E, asl 1297 m). The vertical profiles of horizontal wind estimated from radar VVP/VAD methods agree well with GPS radiosonde profiles, with the low‐level jet at about 1.5 km during monsoon season well depicted in both. The vertical structure and temporal variability of divergence and reflectivity profiles are indicative of the dynamical and microphysical characteristics of shallow convective, deep convective, and stratiform cloud systems. In shallow convective systems, vertical development of reflectivity profiles is limited below 5 km. In deep convective systems, reflectivity values as large as 55 dBZ were observed above freezing level. The stratiform system shows the presence of a reflectivity bright band (~35 dBZ) near the melting level. The diagnosed vertical profiles of divergence in convective and stratiform systems are distinct. In shallow convective conditions, convergence was seen below 4 km with divergence above. Low‐level convergence and upper level divergence are observed in deep convective profiles, while stratiform precipitation has midlevel convergence present between lower level and upper level divergence. The divergence profiles in stratiform precipitation exhibit intense shallow layers of “melting convergence” at 0°C level, near 4.5 km altitude, with a steep gradient on the both sides of the peak. The level of nondivergence in stratiform situations is lower than that in convective situations. These observed vertical structures of divergence are largely indicative of latent heating profiles in the atmosphere, an important ingredient of monsoon dynamics.

Features of nocturnal low level jet (NLLJ) observed over a tropical Indian station using high resolution Doppler wind lidar

High resolution Doppler wind lidar measurements made during the period 01 April 2012 to 31 March 2014 over Pune (18°32′N, 73°51′E, 559m Above Mean Sea Level), India have been used to study Nocturnal Low Level Jet (NLLJ) occurrence and its characteristics. Vertical profiles of horizontal wind in the altitude range from 100m to 3000m (at every 50m interval) and averaged over 5min have been used to study time–height variations during local nighttime. On several occasions during nighttime the wind profiles showed a narrow region of strong wind speed below 1000m altitude from surface, suggesting the presence of the low level jet. Analysis of the data indicates that NLLJ occurs more frequently (~66%) during pre-monsoon season (March–May) and on only 14% of the nocturnal period during SW monsoon season (June-September). Mean jet core heights during pre-monsoon, monsoon, post-monsoon (October–November), and winter (December–February) seasons are found to be 687m, 691m, 593m, and 586m respectively. Seasonal mean jet core speeds during pre-monsoon and monsoon are higher than those during winter. There are some occasions during monsoon season when hourly mean jet speeds during nighttime are as high as 15–20ms−1. Horizontal wind directions in the NLLJ during different seasons are consistent with the seasonal mean flow over the tropical Indian region. Most frequently occurring jet core height is in the height range 600–700m with almost 65% of the cases having jet core heights<700m and maximum frequency of occurrence of jet speed is in the range 9–11ms−1. Large east–west temperature gradients, inertial oscillations, stability in the lower atmosphere seem to be some of the factors that play significant role in the formation and sustenance of NLLJ over the location during different seasons.

Orographic cirrus in a future climate

Abstract. A cloud resolving model (CRM) is used to investigate the formation of orographic cirrus clouds in the current and future climate. The formation of cirrus clouds depends on a variety of dynamical and thermodynamical processes, which act on different scales. First, the capability of the CRM in realistically simulating orographic cirrus clouds has been tested by comparing the simulated results to aircraft measurements of an orographic cirrus cloud. The influence of a warmer climate on the microphysical and optical properties of cirrus clouds has been investigated by initializing the CRM with vertical profiles of horizontal wind, potential temperature and equivalent potential temperature, respectively. The vertical profiles are extracted from IPCC A1B simulations for the current climate and for the period 2090–2099 for two regions representative for North and South America. The influence of additional moisture in a future climate on the propagation of gravity waves and the formation of orographic cirrus could be estimated. In a future climate, the increase in moisture dampens the vertical propagation of gravity waves and the occurring vertical velocities in the moist simulations. Together with higher temperatures fewer ice crystals nucleate homogeneously. Assuming that the relative humidity does not change in a warmer climate the specific humidity in the model is increased. This increase in specific humidity in a warmer climate results in a higher ice water content. The net effect of a reduced ice crystal number concentration and a higher ice water content is an increased optical depth. However, in some moist simulations dynamical changes contribute to changes in the ice water content, ice crystal number concentration and optical depth. For the corresponding dry simulations dynamical changes are more pronounced leading to a decreased optical depth in a future climate in some cases.

A Study of Inertia-Gravity Waves in the Middle Stratosphere Based on Intensive Radiosonde Observations

An intensive observation of the stratosphere has been made using 10 radiosondes every 3 h for the time period of 11-12 May 2006 at Shigaraki, Japan (34.85°N, 136.11°E). Horizontal wind and temperature data were successfully obtained with high accuracy in the height region up to about 36 km. The sampling time intervals are 2 s corresponding to a nominal vertical resolution of about 10 m.Two packets of wavelike fluctuations whose phases propagate downward are detected around a height of 34 km (hereafter referred to as Wave-A) and of 24 km (Wave-B) in the obtained vertical profiles of horizontal winds. Wave parameters are estimated using a hodograph analysis under an assumption that these fluctuations are due to inertia-gravity waves (IGWs). The ground-based wave periods are 11 and 21 h, the horizontal wavelengths are 850 and 900 km, and the vertical wavelengths are 6.0 and 2.6 km, for Wave-A and Wave-B, respectively. It is also shown that both IGWs propagate energy upward and northnorthwestward relative to the background wind. The validity of the assumption is confirmed by the accordance of two independent estimates of the ground-based frequency. The horizontal structure seen in the horizontal divergence field calculated from European Centre for Medium-rangeWeather Forecasts (ECMWF) operational analysis data is consistent with the estimated wave parameters.Sources of the two IGWs are examined by a ray tracing method. Both IGW rays are traced back to the level and latitude of the mid-latitude westerly jet. Detailed examination for temporal variation of the wave structure indicates that the IGWs meandered eastward slightly south of the mid-latitude jet, turned north-northwestward, ascended rapidly where the background wind direction was changed to southward, and reached the middle stratosphere over the observation site. An interesting point is that both locally-defined Rossby number and cross-stream Lagrangian Rossby number are large in the regions where the IGW packets were situated during propagation around the jet from several days. Therefore, it is likely that the IGWs were generated in the vicinity of the unbalanced westerly jet through the spontaneous adjustment processes.

Combined wind profiler-weather radar observations of orographic rainband around Kyushu, Japan in the Baiu season

Abstract. A special observation campaign (X-BAIU), using various instruments (wind profilers, C-band weather radars, X-band Doppler radars, rawinsondes, etc.), was carried out in Kyushu (western Japan) during the Baiu season, from 1998 to 2002. In the X-BAIU-99 and -02 observations, a line-shaped orographic rainband extending northeastward from the Koshikijima Islands appeared in the low-level strong wind with warm-moist airs. The weather radar observation indicated that the rainband was maintained for 11h. The maximum length and width of the rainband observed in 1999 was ~200km and ~20km, respectively. The rainband observed in 2002 was not so developed compared with the case in 1999. The Froude number averaged from sea level to the top of the Koshikijima Islands (~600m) was large (&gt;1), and the lifting condensation level was below the tops of the Koshikijima Islands. Thus, it is suggested that the clouds organizing the rainband are formed by the triggering of the mountains on the airflow passing over them. The vertical profile of horizontal wind in/around the rainband was investigated in the wind profiler observations. In the downdraft region 60km from the Koshikijima Islands, strong wind and its clockwise rotation with increasing height was observed below 3km altitude. In addition, a strong wind component perpendicular to the rainband was observed when the rainband was well developed. These wind behaviors were related to the evolution of the rainband.

Doppler Radar Wind Data Assimilation with HIRLAM 3DVAR

Abstract A Doppler radar wind data assimilation system has been developed for the three-dimensional variational data assimilation (3DVAR) scheme of the High Resolution Limited Area Model (HIRLAM). Radar wind observations can be input for the multivariate HIRLAM 3DVAR either as radial wind superobservations (SOs) or as vertical profiles of horizontal wind obtained with the velocity–azimuth display (VAD) technique. The radar wind data handling system, including data processing, quality control, and observation operators for the 3DVAR, are described and evaluated. Background error standard deviation (σb) in observation space for wind and radial wind have been estimated by the so-called randomization method. The derived values of σb are used in the quality control of observations and also in the assignment of radar wind observation error standard deviations (σo). Parallel data assimilation and forecast experiments confirm reasonably tuned error statistics and indicate a small positive impact of radar wind dat...

Mean characteristics of the spectrum of horizontal velocity in the polar summer mesosphere and lower thermosphere observed by foil chaff

Thirty-three foil chaff rockets were flown at high latitudes during the summers of 1987, 1988, and 1991.Vertical profiles of horizontal wind were obtained at high resolution (25 m) in the 67– 103 km region of the mesosphere and lower thermosphere. This resolution (at that range of altitude) is unique and provides sensitivity to more than two decades of vertical wavenumbers. This study utilizes the unique data set to present observed spectra and their mean characteristics. Average vertical wavenumber spectra indicate that there is excellent agreement with the saturated gravity wave spectral model developed by Dewan and Good (J. Geophys. Res. 91(D3) (1986) 2742) and Smith et al. (J. Atmos. Sci. 44(10) (1987) 1404), which has a slope of −3 and a spectral amplitude proportional to the buoyancy frequency squared. This excellent agreement provides further support for the saturated spectrum theory in a mean sense and suggests that saturation processes are present in the horizontal flow and act to produce turbulence. We can therefore expect that turbulence is enhanced near the polar summer mesopause. Dominant vertical wavelength obtained from the average spectra is estimated to be 12.8 km .

Comparisons of CLOVAR windprofiler horizontal winds with radiosondes and CMC regional analyses

The Canadian (London, Ontario) VHF Atmospheric Radar (CLOVAR) windprofiler radar near London, Ontario is a relatively new tool for atmospheric wind measurements (Hocking, 1994, 1997a). In order to verify its proper performance, vertical profiles of horizontal winds were compared with other wind estimates available during the period January 1996 to November 1997. Comparisons with co‐located radiosonde flights (a series of 29 flights in May–June 1996, and another of 8 flights in May–July 1997) showed excellent agreement between the two techniques. In addition, comparisons with horizontal winds measured by routine radiosonde balloons launched some 180 km south‐west of London, at White Lake (Detroit), and some 210 km east of London at Buffalo Airport, showed good agreement, considering the meteorological differences which would be expected at these ranges. A further comparison between winds measured with the radar, and winds extracted for London from Canadian Meteorological Centre (CMC) regional analyses, showed very good agreement. These favourable intercomparisons have verified that the CLOVAR is a reliable tool for observing horizontal winds, and have provided interesting insight into the CMC model.

Analysis techniques for the recovery of winds and backscatter coefficients from a multiple-channel incoherent Doppler lidar

The University of Michigan has developed an incoherent-detection Doppler lidar system that continuously measures vertical profiles of horizontal winds and aerosol backscatter. An overview of the instrument is given, followed by a description of improvements that have been made to control the system stability. Most notably, an active feedback system has been implemented to improve the laser frequency stability. A detailed forward model of the instrument is developed that includes many subtle effects, such as detector nonlinearity. A nonlinear least-squares inversion method is then described that permits the recovery of Doppler shift and aerosol backscatter without requiring assumptions about the molecular component of the signal. Examples of wind and aerosol backscatter profiles are shown to illustrate the capabilities of the fitting method.

Saturated Gravity Wave Spectrum in the Polar Summer Lower Thermosphere Observed by Foil Chaff during Campaign “Sodium 88”

Abstract Ten vertical profiles of horizontal winds have been measured at high resolution (25 m) in the range from 85 to 103 km during the sodium campaign in summer 1988 at Andenes, northern Norway (69°N). The purposes of this study are to examine the hypothesis that the vertical wavenumber spectrum is controlled by saturation processes and to identify the mechanisms that contribute to saturation of the atmospheric motion spectrum within the observed height range. An analysis of vertical wavenumber spectra and vertical wind shears of the ten horizontal wind measurements is presented. Our results indicate a rather good agreement between the observed and predicted velocity spectra in both amplitude and slope for vertical wavelengths up to about 12.8 km. (This wavelength is given by the height interval covered by the experiment.) Very large wind shears, as high as 40–90 m s−1 km−1, are observed to be present at various heights, and at certain heights the shears even exceed 100 m s−1 km−1. Such strong wind she...

Winds Measured by a UHF Doppler Radar and Rawinsondes: Comparisons Made on Twenty-Six Days (August-September 1977) at Arecibo, Puerto Rico

Abstract Vertical profiles of horizontal winds in the lower stratosphere and upper troposphere were measured by the UHF Doppler radar at Arecibo, Puerto Rico (18.35°N, 66.75°W) on 26 days in August and September 1977. On comparing these with horizontal winds measured by routine rawinsonde balloons launched some 80 km east of Arecibo, fairly good agreement between every wind profile can be seen. Most of the difference between the two sets of measurements in the lower stratosphere is shown to be caused by the experimental error of the rawinsonde, while the spatial and/or temporal variations in the wind field seem to dominate the difference in the upper troposphere.

High-Altitude Infrared Radar Wind Measurements

A vertical profile of horizontal wind has been measured to better than 0.5 m s−1 accuracy up to 8 km altitude by measuring the Doppler frequency shift of aerosols with the Firepond infrared radar.

Winds Derived from Radar Measurements in the Arctic Troposphere and Stratosphere

Abstract Using the Chatanika radar near Fairbanks, Alaska, vertical profiles of horizontal wind extending over an altitude range of about 2 to 23 km have been measured. These profiles agree in detail with simultaneous rawinsonde measurements made nearby. The radar also measures vertical motion, a capability which the rawinsonde does not have. Since the radar technique can monitor the winds with good spatial and temporal resolution, the Chatanika radar is an excellent facility for studying various dynamic processes in the troposphere and stratosphere of the Arctic.

Dropwindsonde Instrumentation for Weather Reconnaissance Aircraft

Abstract A windfinding dropsonde instrumentation system is described, with examples of its operational use in the GARP Atlantic Tropical Experiment conducted during the summer of 1974. Deployed from an aircraft flying typically at ∼10 km altitude, the dropsonde transmits vertical profiles of horizontal wind, pressure, temperature and humidity while descending on a parachute at ∼5 m s−1. The temperature sensor in the dropsonde is a 95-mil bead thermistor, the humidity sensor a standard carbon strip hygristor, and the pressure sensor an improved aneroid cell. Winds are determined by tracking the sonde using the 13.6 kHz Omega navigation signals received by an Omega receiver and retransmitted over a telemetry link. The telemetered data from a dropsonde are received, and recorded on-board the aircraft, using a computerized system configured to permit processing of two sondes descending simultaneously (one operating on 404.5 MHz, the other on 405.5 MHz).