Winds in the Lower Cloud Level on the Nightside of Venus from VIRTIS-M (Venus Express) 1.74 μm Images

The horizontal wind velocity vectors at the lower cloud layer were retrieved by tracking the displacement of cloud features using the 1.74 µm images of the full Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS-M) dataset. This layer was found to be in a superrotation mode with a westward mean speed of 60–63 m s−1 in the latitude range of 0–60° S, with a 1–5 m s−1 westward deceleration across the nightside. Meridional motion is significantly weaker, at 0–2 m s−1; it is equatorward at latitudes higher than 20° S, and changes its direction to poleward in the equatorial region with a simultaneous increase of wind speed. It was assumed that higher levels of the atmosphere are traced in the equatorial region and a fragment of the poleward branch of the direct lower cloud Hadley cell is observed. The fragment of the equatorward branch reveals itself in the middle latitudes. A diurnal variation of the meridional wind speed was found, as east of 21 h local time, the direction changes from equatorward to poleward in latitudes lower than 20° S. Significant correlation with surface topography was not found, except for a slight decrease of zonal wind speed, which was connected to the volcanic area of Imdr Regio.

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Assessment of the ERA-Interim Winds Using High-Altitude Stratospheric Balloons

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-16-0137.1 ◽

2017 ◽

Vol 74 (6) ◽

pp. 2065-2080 ◽

Cited By ~ 7

Author(s):

Fabrice Duruisseau ◽

Nathalie Huret ◽

Alice Andral ◽

Claude Camy-Peyret

Keyword(s):

Wind Speed ◽

High Altitude ◽

Middle Atmosphere ◽

Meridional Wind ◽

Horizontal Wind ◽

Quasi Biennial Oscillation ◽

Wind Variability ◽

Wind Measurements ◽

Biennial Oscillation ◽

Balloon Measurements

Abstract This study focuses on the ability of ERA-Interim to represent wind variability in the middle atmosphere. The originality of the proposed approach is that wind measurements are deduced from the trajectories of zero-pressure balloons that can reach high-stratospheric altitudes. These balloons are mainly used to carry large scientific payloads. The trajectories of balloons launched above Esrange, Sweden, and Teresina, Brazil, from 2000 to 2011 were used to deduce zonal and meridional wind components (by considering the balloon as a perfect tracer at high altitude). Collected data cover several dynamical conditions associated with the winter and summer polar seasons and west and east phases of the quasi-biennial oscillation at the equator. Systematic comparisons between measurements and ERA-Interim data were performed for the two horizontal wind components, as well as wind speed and wind direction in the [100, 2]-hPa pressure range to deduce biases between the model and balloon measurements as a function of altitude. Results show that whatever the location and the geophysical conditions considered, biases between ERA-Interim and balloon wind measurements increase as a function of altitude. The standard deviation of the model–observation wind differences can attain more than 5 m s−1 at high altitude (pressure P < 20 hPa). A systematic ERA-Interim underestimation of the wind speed is observed and large biases are highlighted, especially for equatorial flights.

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Intercomparisons of Tropospheric Wind Velocities Measured by Multi-Frequency Wind Profilers and Rawinsonde

Atmosphere ◽

10.3390/atmos12101284 ◽

2021 ◽

Vol 12 (10) ◽

pp. 1284

Author(s):

Zhao-Yu Chen ◽

Yen-Hsyang Chu ◽

Ching-Lun Su

Keyword(s):

Wind Speed ◽

Three Dimensional ◽

Meridional Wind ◽

Horizontal Wind ◽

Wind Component ◽

Horizontal Wind Speed ◽

Order Of Magnitude ◽

Wind Velocities ◽

Mean Square Difference ◽

Wind Profilers

Concurrent measurements of three-dimensional wind velocities made with three co-located wind profilers operated at frequencies of 52 MHz, 449 MHz, and 1.29 GHz for the period 12–16 September 2017 are compared for the first time in this study. The velocity–azimuth display (VAD) method is employed to estimate the wind velocities. The result shows that, in the absence of precipitation, the root mean square difference (RMSD) in the horizontal wind speed velocities U and wind directions D between different pairs of wind profilers are, respectively, in the range of 0.94–0.99 ms−1 and 7.7–8.3°, and those of zonal wind component u and meridional wind component v are in the respective ranges of 0.91–1.02 ms−1 and 1.1–1.24 ms−1. However, the RMSDs between wind profilers and rawinsonde are in the range of 2.89–3.26 ms−1 for horizontal wind speed velocity and 11.17–14.48° for the wind direction, which are around 2–3 factors greater than those between the wind profilers on average. In addition to the RMSDs, MDs between wind profilers and radiosonde are around one order of magnitude larger than those between wind profilers. These results show that the RMSDs, MDs, and Stdds between radars are highly consistent with each other, and they are much smaller than those between radar and rawinsonde. This therefore suggests that the wind profiler-measured horizontal wind velocities are much more reliable, precise, and accurate than the rawinsonde measurement.

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Wind Retrieval Algorithms for the IWRAP and HIWRAP Airborne Doppler Radars with Applications to Hurricanes

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-13-00140.1 ◽

2014 ◽

Vol 31 (6) ◽

pp. 1189-1215 ◽

Cited By ~ 19

Author(s):

Stephen R. Guimond ◽

Lin Tian ◽

Gerald M. Heymsfield ◽

Stephen J. Frasier

Keyword(s):

Wind Speed ◽

Least Squares ◽

Meridional Wind ◽

Solution Procedure ◽

Measured Data ◽

Horizontal Wind ◽

Random Errors ◽

Dual Frequency ◽

Horizontal Wind Speed ◽

Hurricane Wind

Abstract Algorithms for the retrieval of atmospheric winds in precipitating systems from downward-pointing, conically scanning airborne Doppler radars are presented. The focus is on two radars: the Imaging Wind and Rain Airborne Profiler (IWRAP) and the High-Altitude IWRAP (HIWRAP). The IWRAP is a dual-frequency (C and Ku bands), multibeam (incidence angles of 30°–50°) system that flies on the NOAA WP-3D aircraft at altitudes of 2–4 km. The HIWRAP is a dual-frequency (Ku and Ka bands), dual-beam (incidence angles of 30° and 40°) system that flies on the NASA Global Hawk aircraft at altitudes of 18–20 km. Retrievals of the three Cartesian wind components over the entire radar sampling volume are described, which can be determined using either a traditional least squares or variational solution procedure. The random errors in the retrievals due to the airborne radar geometry and noise in the Doppler velocities are evaluated using both an error propagation analysis with least squares theory and a numerical simulation of a hurricane. These analyses show that the vertical and along-track wind errors have strong across-track dependence with values ranging from 0.25 m s−1 at nadir to 2.0 and 1.0 m s−1 at the swath edges, respectively. The average across-track wind errors are ~2.5 m s−1 or 7% of the hurricane wind speed. For typical rotated figure-four flight patterns through hurricanes, the zonal and meridional wind speed errors are ~1.5–2.0 m s−1. Evaluations of both retrieval methods show that the variational procedure is generally preferable to the least squares procedure. Examples of measured data retrievals from IWRAP during an eyewall replacement cycle in Hurricane Isabel (2003) and from HIWRAP during the development of Tropical Storm Matthew (2010) are shown. Comparisons of IWRAP-measured data retrievals at nadir to flight-level data show errors of ~2.0 m s−1 for vertical winds and ~4.0 m s−1 for horizontal wind speed (~7% of the hurricane wind speed). Additional sources of error, such as hydrometeor fall speed uncertainties and a small height offset in the comparisons, are likely responsible for the larger vertical wind errors when compared to the simulated error analyses.

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Characteristics of Stratospheric Winds over Jiuquan (41.1°N, 100.2°E) Using Rocketsonde Data in 1967–2004

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-16-0014.1 ◽

2017 ◽

Vol 34 (3) ◽

pp. 657-667 ◽

Cited By ~ 2

Author(s):

Z. Sheng ◽

J. W. Li ◽

Y. Jiang ◽

S. D. Zhou ◽

W. L. Shi

Keyword(s):

Zonal Wind ◽

Middle Atmosphere ◽

Correlation Coefficients ◽

Meridional Wind ◽

Horizontal Wind ◽

Cycle Period ◽

Observation Data ◽

Wind Fields ◽

Zonal Winds ◽

Model Research

AbstractStratospheric winds play a significant role in middle atmosphere dynamics, model research, and carrier rocket experiments. For the first time, 65 sets of rocket sounding experiments conducted at Jiuquan (41.1°N, 100.2°E), China, from 1967 to 2004 are presented to study horizontal wind fields in the stratosphere. At a fixed height, wind speed obeys the lognormal distribution. Seasonal mean winds are westerly in winter and easterly in summer. In spring and autumn, zonal wind directions change from the upper to the lower stratosphere. The monthly zonal mean winds have an annual cycle period with large amplitudes at high altitudes. The correlation coefficients for zonal winds between observations and the Horizontal Wind Model (HWM) with all datasets are 0.7. The MERRA reanalysis is in good agreement with rocketsonde data according to the zonal winds comparison with a coefficient of 0.98. The sudden stratospheric warming is an important contribution to biases in the HWM, because it changes the zonal wind direction in the midlatitudes. Both the model and the reanalysis show dramatic meridional wind differences with the observation data.

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A Wind Study of Venus’s Cloud Top: New Doppler Velocimetry Observations

Atmosphere ◽

10.3390/atmos12010002 ◽

2020 ◽

Vol 12 (1) ◽

pp. 2

Author(s):

Ruben Gonçalves ◽

Pedro Machado ◽

Thomas Widemann ◽

Francisco Brasil ◽

José Ribeiro

Keyword(s):

Spatial Variability ◽

Local Time ◽

Zonal Wind ◽

Meridional Wind ◽

Space Mission ◽

Horizontal Wind ◽

Doppler Velocimetry ◽

Middle Latitudes ◽

Wind Velocities ◽

Wind Stability

At Venus’s cloud top, the circulation is dominated by the superroration, where zonal wind speed peaks at ∼100 ms−1, in the low-to-middle latitudes. The constraining of zonal and meridional circulations is essential to understanding the mechanisms driving the superrotation of Venus’s atmosphere, which are still poorly understood. We present new Doppler velocimetry measurements of horizontal wind velocities at Venus’s cloud top, around 70 km altitude. These results were based on March 2015 observations at the Canada–France–Hawaii Telescope (CFHT, Mauna Kea, Hawaii), using ESPaDOnS. The Doppler velocimetry method used has already successfully provided zonal and meridional results in previous works led by P. Machado and R. Gonçalves, proving to be a good reference ground-based technique in the study of the dynamics of Venus’s atmosphere. These observations were carried out between 27 and 29 March 2015, using the Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) which provides simultaneous visible-near IR spectra from 370 to 1050 nm, with a spectral resolution of 81000 allowing wind field characterization in the scattered Franuhofer solar lines by Venus’s cloud top on the dayside. The zonal velocities are consistent with previous results while also showing evidence of spatial variability, along planetocentric latitude and longitude (local-time). The meridional wind circulation presents a notably constant latitudinal structure with null velocities at lower latitudes, below 10∘ N–S, and peak velocities of ∼30 ms−1, centered around 35∘ N–S. The uncertainty of the meridional wind results from ground observations is of the same order as the uncertainty of meridional wind retrieved by space-based observations using cloud-tracking, as also shown by previous work led by R. Gonçalves and published in 2020. These March 2015 measurements present a unique and valuable contribution to the study of horizontal wind at the cloud top, from a period when Doppler velocimetry was the only available method to do so, since no space mission was orbiting Venus between Venus Express ending in January 2015 and Akatsuki’s orbit insertion in December 2015. These results from new observations provide (1) constraints on zonal wind temporal and spatial variability (latitude and local time), (2) constraints on the meridional wind latitudinal profile, (3) additional evidence of zonal and meridional wind stability for the period between 2011 and 2015 (along previous Doppler results) (4) further evidence of the consistency and robustness of our Doppler velocimetry method.

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Doppler wind lidar activities at Cabauw

10.5194/ems2021-136 ◽

2021 ◽

Author(s):

Steven Knoop ◽

Fred Bosveld ◽

Marijn de Haij ◽

Arnoud Apituley

Keyword(s):

Wind Speed ◽

Wind Profile ◽

Continuous Wave ◽

Wind Farms ◽

Data Availability ◽

Horizontal Wind ◽

Horizontal Wind Speed ◽

Low Clouds ◽

Wind Measurements ◽

Wind Lidar

Atmospheric motion and turbulence are essential parameters for weather and topics related to air quality. Therefore, wind profile measurements play an important role in atmospheric research and meteorology. One source of wind profile data are Doppler wind lidars, which are laser-based remote sensing instruments that measure wind speed and wind direction up to a few hundred meters or even a few kilometers. Commercial wind lidars use the laser wavelength of 1.5 &#181;m and therefore backscatter is mainly from aerosols while clear air backscatter is minimal, limiting the range to the boundary layer typically.We have carried out a two-year intercomparison of the ZephIR 300M (ZX Lidars) short-range wind lidar and tall mast wind measurements at Cabauw [1]. We have focused on the (height-dependent) data availability of the wind lidar under various meteorological conditions and the data quality through a comparison with in situ wind measurements at several levels in the 213m tall meteorological mast. We have found an overall availability of quality-controlled wind lidar data of 97% to 98 %, where the missing part is mainly due to precipitation events exceeding 1 mm/h or fog or low clouds below 100 m. The mean bias in the horizontal wind speed is within 0.1 m/s with a high correlation between the mast and wind lidar measurements, although under some specific conditions (very high wind speed, fog or low clouds) larger deviations are observed. This instrument is being deployed within North Sea wind farms.Recently, a scanning long-range wind lidar Windcube 200S (Leosphere/Vaisala) has been installed at Cabauw, as part of the Ruisdael Observatory program [2]. The scanning Doppler wind lidars will provide detailed measurements of the wind field, aerosols and clouds around the Cabauw site, in coordination with other instruments, such as the cloud radar.[1] Knoop, S., Bosveld, F. C., de Haij, M. J., and Apituley, A.: A 2-year intercomparison of continuous-wave focusing wind lidar and tall mast wind measurements at Cabauw, Atmos. Meas. Tech., 14, 2219&#8211;2235, 2021[2] https://ruisdael-observatory.nl/

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Comparison of Large Eddy Simulations of a convective boundary layer with wind LIDAR measurements

Advances in Science and Research ◽

10.5194/asr-8-83-2012 ◽

2012 ◽

Vol 8 (1) ◽

pp. 83-86 ◽

Cited By ~ 5

Author(s):

J. G. Pedersen ◽

M. Kelly ◽

S.-E. Gryning ◽

R. Floors ◽

E. Batchvarova ◽

...

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Geostrophic Wind ◽

Large Eddy Simulations ◽

Horizontal Wind ◽

Convective Boundary ◽

Horizontal Wind Speed ◽

Large Eddy ◽

Lidar Measurements ◽

Wind Lidar

Abstract. Vertical profiles of the horizontal wind speed and of the standard deviation of vertical wind speed from Large Eddy Simulations of a convective atmospheric boundary layer are compared to wind LIDAR measurements up to 1400 m. Fair agreement regarding both types of profiles is observed only when the simulated flow is driven by a both time- and height-dependent geostrophic wind and a time-dependent surface heat flux. This underlines the importance of mesoscale effects when the flow above the atmospheric surface layer is simulated with a computational fluid dynamics model.

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Development of an in situ Acoustic Anemometer to Measure Wind in the Stratosphere for SENSOR

10.5194/amt-2021-76 ◽

2021 ◽

Author(s):

Song Liang ◽

Hu Xiong ◽

Wei Feng ◽

Yan Zhaoai ◽

Xu Qingchen ◽

...

Keyword(s):

Wind Speed ◽

Meridional Wind ◽

Floating Platform ◽

Level Flight ◽

Subsequent Publication ◽

Wind Measurements ◽

Commercial Off The Shelf ◽

Solar Storms ◽

Acoustic Anemometer

Abstract. The Stratospheric Environmental respoNses to Solar stORms (SENSOR) campaign investigates the influence of solar storms on the stratosphere. This campaign employs a long-duration zero-pressure balloon as a platform to carry multiple types of payloads during a series of flight experiments in the mid-latitude stratosphere from 2019 to 2022. This article describes the development and testing of an acoustic anemometer for obtaining in situ wind measurements along the balloon trajectory. Developing this anemometer was necessary, as there is no existing commercial off-the-shelf product, to the authors' knowledge, capable of obtaining in situ wind measurements on a high-altitude balloon or other similar floating platform in the stratosphere. The anemometer is also equipped with temperature, pressure, and humidity sensors from a Temperature-Pressure-Humidity measurement module, inherited from a radiosonde developed for sounding balloons. The acoustic anemometer and other sensors were used in a flight experiment of the SENSOR campaign that took place in the Da chaidan District (95.37° E, 37.74° N) on 4 September 2019. The zonal and meridional wind speed observations, which were obtained during level flight at an altitude exceeding 20 km, are presented. This is the first time that in situ wind measurements were obtained during level flight at this altitude. In addition to wind speed measurements, temperature, pressure, and relative humidity measurements during ascent are compared to observations from a nearby radiosonde launched four hours earlier. Further analysis of the wind data will presented in a subsequent publication. The problems experienced by the acoustic anemometer during the 2019 experiment show that the acoustic anemometer must be improved for future experiments in the SENSOR campaign.

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The Temporal Autocorrelation Structure of Sea Surface Winds

Journal of Climate ◽

10.1175/jcli-d-11-00698.1 ◽

2012 ◽

Vol 25 (19) ◽

pp. 6684-6700 ◽

Cited By ~ 13

Author(s):

Adam H. Monahan

Keyword(s):

Wind Speed ◽

Zonal Wind ◽

Large Scale ◽

Strong Dependence ◽

Meridional Wind ◽

Sea Surface ◽

Small Scale ◽

Wind Component ◽

Temporal Autocorrelation ◽

Vector Wind

Abstract The temporal autocorrelation structures of sea surface vector winds and wind speeds are considered. Analyses of scatterometer and reanalysis wind data demonstrate that the autocorrelation functions (acf) of surface zonal wind, meridional wind, and wind speed generally drop off more rapidly in the midlatitudes than in the low latitudes. Furthermore, the meridional wind component and wind speed generally decorrelate more rapidly than the zonal wind component. The anisotropy in vector wind decorrelation scales is demonstrated to be most pronounced in the storm tracks and near the equator, and to be a feature of winds throughout the depth of the troposphere. The extratropical anisotropy is interpreted in terms of an idealized kinematic eddy model as resulting from differences in the structure of wind anomalies in the directions along and across eddy paths. The tropical anisotropy is interpreted in terms of the kinematics of large-scale equatorial waves and small-scale convection. Modeling the vector wind fluctuations as Gaussian, an explicit expression for the wind speed acf is obtained. This model predicts that the wind speed acf should decay more rapidly than that of at least one component of the vector winds. Furthermore, the model predicts a strong dependence of the wind speed acf on the ratios of the means of vector wind components to their standard deviations. These model results are shown to be broadly consistent with the relationship between the acf of vector wind components and wind speed, despite the presence of non-Gaussian structure in the observed surface vector winds.

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Direct radiative effect of the Russian wildfires and its impact on air temperature and atmospheric dynamics during August 2010

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-1999-2014 ◽

2014 ◽

Vol 14 (4) ◽

pp. 1999-2013 ◽

Cited By ~ 34

Author(s):

J. C. Péré ◽

B. Bessagnet ◽

M. Mallet ◽

F. Waquet ◽

I. Chiapello ◽

...

Keyword(s):

Optical Properties ◽

Wind Speed ◽

Eastern Europe ◽

Air Temperature ◽

Air Entrainment ◽

Atmospheric Dynamics ◽

Horizontal Wind ◽

Satellite Measurements ◽

Near Surface ◽

Aerosol Plume

Abstract. In this study, we investigate the shortwave aerosol direct radiative forcing (ADRF) and its feedback on air temperature and atmospheric dynamics during a major fire event that occurred in Russia during August 2010. The methodology is based on an offline coupling between the CHIMERE chemistry-transport and the Weather Research and Forecasting (WRF) models. First, simulations for the period 5–12 August 2010 have been evaluated by using AERONET (AErosol RObotic NETwork) and satellite measurements of the POLarization and Directionality of the Earth's Reflectance (POLDER) and the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) sensors. During this period, elevated POLDER aerosol optical thickness (AOT) is found over a large part of eastern Europe, with values above 2 (at 550 nm) in the aerosol plume. According to CALIOP observations, particles remain confined to the first five kilometres of the atmospheric layer. Comparisons with satellite measurements show the ability of CHIMERE to reproduce the regional and vertical distribution of aerosols during their transport from the source region. Over Moscow, AERONET measurements indicate an important increase of AOT (340 nm) from 0.7 on 5 August to 2–4 between 6 and 10 August when the aerosol plume was advected over the city. Particles are mainly observed in the fine size mode (radius in the range 0.2–0.4 μm) and are characterized by elevated single-scattering albedo (SSA) (0.95–0.96 between 440 and 1020 nm). Comparisons of simulations with AERONET measurements show that aerosol physical–optical properties (size distribution, AOT, SSA) have been well simulated over Moscow in terms of intensity and/or spectral dependence. Secondly, modelled aerosol optical properties have been used as input in the radiative transfer code of WRF to evaluate their direct radiative impact. Simulations indicate a significant reduction of solar radiation at the ground (up to 80–150 W m−2 in diurnal averages over a large part of eastern Europe due to the presence of the aerosol plume. This ADRF causes an important reduction of the near-surface air temperature between 0.2 and 2.6° on a regional scale. Moscow has been affected by the aerosol plume, especially between 6 and 10 August. During this period, aerosol causes a significant reduction of surface shortwave radiation (up to 70–84 W m−2 in diurnal averages) with a moderate part (20–30%) due to solar absorption within the aerosol layer. The resulting feedbacks lead to a cooling of the air up to 1.6° at the surface and 0.1° at an altitude of 1500–2000 m (in diurnal averages), that contribute to stabilize the atmospheric boundary layer (ABL). Indeed, a reduction of the ABL height of 13 to 65% has been simulated during daytime in presence of aerosols. This decrease is the result of a lower air entrainment as the vertical wind speed in the ABL is shown to be reduced by 5 to 80% (at midday) when the feedback of the ADRF is taken into account. However, the ADRF is shown to have a lower impact on the horizontal wind speed, suggesting that the dilution of particles would be mainly affected by the weakening of the ABL development and associated vertical entrainment. Indeed, CHIMERE simulations driven by the WRF meteorological fields including this ADRF feedback result in a large increase in the modelled near-surface PM10 concentrations (up to 99%). This is due to their lower vertical dilution in the ABL, which tend to reduce model biases with the ground PM10 values observed over Moscow during this specific period.

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