Strong Horizontal Wind Research Articles

Physical quantity characteristics of severe aircraft turbulence near convective clouds over Australia

Using FY–2G satellite data, Aircraft Meteorological Data Relay (AMDAR) downlink data, and the fifth generation European Centre for Medium–Range Weather Forecasts (ECMWF) atmospheric reanalysis of the global climate (ERA5) dataset, we analyzed the circulation, thermal, and dynamic characteristics of the convective aircraft turbulence over Australia in the Southern Hemisphere. The results show that the near-convective clouds turbulence (NCCT) in the Southern Hemisphere mostly occurred in front of deep warm high–pressure ridges in mid–latitude regions and on the left side of the axis of the subtropical westerly jet stream. The isotherms in this area were relatively dense (i.e., large gradients), and the wind speed was high, with strong horizontal and/or vertical cyclonic wind shear. In addition, the NCCT usually occurred near the zero–divergence or zero–vorticity line and in areas with large vertical wind speed gradients. There were also strong vertical and horizontal wind shears in this area, which could easily trigger severe turbulence. Furthermore, the NCCT in the Southern Hemisphere mostly occurred at the intersection of cold and warm temperature advections (i.e., near the zero–temperature advection line), and the turbulence point was located near the high–altitude frontal zone where there was a strong gradient of cold and warm advections. There was temperature inversion with pseudo–equivalent potential temperatures in the middle and lower troposphere on the warmer side of the turbulence point. The unstable stratification of cold air at the top and warm air at the bottom was conducive to triggering convection from the ground, forming strong convective clouds, and causing severe turbulence.

Water Vapor Lidar Observation and Data Assimilation for a Moist Low-Level Jet Triggering a Mesoscale Convective System

Abstract We conducted field observations using two water vapor Raman lidars (RLs) in Kyushu, Japan, to clarify the characteristics of a moist low-level jet (MLLJ), which plays a fundamental role in the formation and maintenance of mesoscale convective systems (MCSs). The two RLs observed the inside and outside of an MLLJ, providing moisture to an MCS with local heavy precipitation on 9 July 2021. Our observations revealed that the MLLJ contained large amounts of moisture below the convective mixing layer height of 1.6 km. The large amount of moisture in the MLLJ might be intensified by low-level convergences and/or water vapor buoyancy facilitated by strong horizontal wind. We conducted four data assimilation experiments: CNTL that assimilated Japan Meteorological Agency operational observation data and three other experiments that ingested the lidar-derived vertical moisture profiles as well as the operational observation data. The experiments assimilating lidar-derived vertical moisture profiles caused intensification and southwestward extensions of the low-level convergence zone, resulting in local heavy precipitation at lower latitudes in experiments assimilating lidar-derived moisture profiles than in CNTL. All three experiments ingesting vertical moisture profiles generally produced better 9-h precipitation forecasts than CNTL, implying that the assimilation of vertical moisture profiles could be well suited for numerical weather prediction of local heavy precipitation. Moreover, the experiment assimilating both of the two RL sites’ data reproduced better forecast fields than experiments assimilating a single RL site’s data, implying that data assimilation of vertical moisture profiles at multiple RL sites enables us to improve initial conditions compared to a single RL site. Significance Statement Moist low-level jets (MLLJs) are moisture-rich airflows in the low-level atmosphere that play an important role in developing mesoscale convective systems and local heavy rainfall. To better understand the mechanisms affecting the development of local heavy rainfall events and to improve our ability to forecast them, studying the moisture structures in MLLJs is important. We succeeded in observing an MLLJ in western Japan using water vapor Raman lidars (RLs), which obtained vertical moisture profiles, and revealed details of vertical moisture structures in the MLLJ. We also performed data assimilation experiments to examine the impact of assimilating vertical moisture profiles observed by the RLs. The results showed that the assimilation of the moisture data improved the forecasting of local heavy rainfall.

Lifetimes of metastable windy states in two-dimensional Rayleigh–Bénard convection with stress-free boundaries

Two-dimensional horizontally periodic Rayleigh–Bénard convection between stress-free boundaries displays two distinct types of states, depending on the initial conditions. Roll states are composed of pairs of counter-rotating convection rolls. Windy states are dominated by strong horizontal wind (also called zonal flow) that is vertically sheared, precludes convection rolls and suppresses heat transport. Windy states occur only when the Rayleigh number $Ra$ is sufficiently above the onset of convection. At intermediate $Ra$ values, windy states can be induced by suitable initial conditions, but they undergo a transition to roll states after finite lifetimes. At larger $Ra$ values, where windy states have been observed for the full duration of simulations, it is unknown whether they represent chaotic attractors or only metastable states that would eventually undergo a transition to roll states. We study this question using direct numerical simulations of a fluid with a Prandtl number of 10 in a layer whose horizontal period is eight times its height. At each of seven $Ra$ values between $9\times 10^6$ and $2.25\times 10^7$ we have carried out 200 or more simulations, all from initial conditions leading to windy convection with finite lifetimes. The lifetime statistics at each $Ra$ indicate a memoryless process with survival probability decreasing exponentially in time. The mean lifetimes grow with $Ra$ approximately as $Ra^4$ . This analysis provides no $Ra$ value at which windy convection becomes stable; it might remain metastable at larger $Ra$ with extremely long lifetimes.

Air‐Sea Heat Fluxes Associated With Convective Cold Pools

AbstractHigh‐resolution air‐sea observations collected by a suite of remotely‐piloted uncrewed surface vehicles (USV) provide new insight on surface latent and sensible heat fluxes associated with convective cold pools over the eastern Pacific Intertropical Convergence Zone (ITCZ). Convective cold pools are linked to isolated, heavily precipitating cells over the ocean that yield downdrafts of evaporatively‐cooled air that spreads out horizontally in all directions and are characterized by strong air temperature gradients and horizontal wind speeds. Cold pool frontal signatures are identified based on air temperature depression criteria of −1.5°C in 10 min or less, resulting in a total of 276 events observed within the eastern Pacific ITCZ across 590 total seadays of data from 10 drones over the course of 3 years. Composite analysis reveals enhanced latent and sensible heat fluxes from the ocean to the atmosphere immediately following the frontal passage, and a decomposition of the bulk flux formulas indicates that variations in latent heat flux are largely influenced by the anomalous wind field (i.e., the cold pool gust front) acting on the mean background air‐sea moisture gradient, while variations in sensible heat flux are largely influenced by the mean background wind acting on the anomalous air‐sea temperature gradient (i.e., the cold pool temperature front). High‐frequency variations in wind speed and velocity are further explored in the context of “gustiness” and averaging intervals used in bulk flux algorithms. A case study is also presented for a convective cold pool event captured by a traveling mesoscale network, or mesonet, of USVs.

Regional PM2.5 pollution confined by atmospheric internal boundaries in the North China Plain: Analysis based on surface observations

There are plenty of mesoscale meteorological discontinuities in the atmosphere, acting as atmospheric internal boundaries (AIBs). In conjunction with the atmospheric boundary layer in the vertical direction, they form confined three-dimensional structures that significantly affect air pollution. However, the role of AIBs in regional pollution has not been systematically elucidated. Based on surface observations, this study investigates PM2.5 pollution distributions under the forcing of various AIBs in the North China Plain. A total of 98 regional pollution episodes are identified during the autumn and winter of 2014–2020, and are further classified according to the impact of AIBs. In the pollution formation-maintenance stage, there are three categories. The frontal category (with a frequency of 41%), including the frontal trough type and frontal inverted trough type, displays the most polluted air masses along the mountains. The frontal AIB defines the lateral border of the pollution zone and forms a frontal inversion above, creating a closed and stable structure wherein the highest concentration of PM2.5 accumulates. The wind shear category (29%) is decided by the dynamic convergence AIB, which causes lighter PM2.5 pollution with diverse spatial patterns corresponding to west-southwest shear, southeast-east shear, and south-north shear. The topographic obstruction category (14%) presents as a narrow arc-shaped pollution belt at the foot of the windward mountains, resulting from the cold air damming AIB with dynamical obstruction and thermal stratification. Pollution diffuses in three ways: northwest, west, and northeast, respectively. The first one is the strongest and most frequent (42%), with both strong horizontal wind and vertical mixing. The second category is relatively rare (17%), characterized by foehn-induced active vertical ventilation. The last one is frequent (41%), but relatively weak, mainly relying on horizontal diffusion. Some evolution details of the AIB affecting PM2.5 pollution are also illustrated by a typical case.

Meteorological aspects of the atypical seasonal lightning distribution at the Gaisberg tower

The seasonal lightning distribution at the Gaisberg tower in Austria is very different from the distribution observed in a circular ring with a radius of 2 to 10 km around the tower. The distribution in the circular ring shows the typical peak during the convective season. In contrast, we find a bimodal distribution with a peak in early spring and late fall at the tower. By selecting two cases representing these two situations, the differences in the meteorological setting are discussed.Lightning events observed solely at the Gaisberg tower are characterized by strong horizontal winds in the lower layers of the atmosphere from the northwest sector. This direction represents the open window from the Gaisberg towards the foreland, meaning there are no mountains upstream, and the flow can reach the Gaisberg unhindered. Cases of this type occur mainly during the cold season but are not limited to it.In contrast, lightning events at the tower and in its vicinity are typical for convective events with low horizontal wind speed in the lower layers and occur mainly during the convective season.

GPM-CO observations of Medicane Ianos: Comparative analysis of precipitation structure between development and mature phase

The present work exploits the satellite measurements from the NASA/JAXA Global Precipitation Measurement Core Observatory (GPM-CO) active and passive microwave sensors to analyze the precipitation structure of the most intense Mediterranean Hurricane (Medicane) on record, named Ianos, which swept across the Ionian Sea between 14 and 18 September 2020. Two GPM-CO overpasses, available during Ianos development and tropical-like cyclone (mature) phase, are analyzed in detail. GPM Microwave Imager measurements are used to carry out a comparative analysis of the medicane precipitation structure and microphysics processes between the two phases. The GPM-CO Dual-frequency Precipitation Radar overpass, available for the first time during a medicane mature phase, provides key measurements and products to analyze the 3D precipitation structure in the rainbands, offering further evidence of the main precipitation microphysics processes inferred from the passive microwave measurement analysis. Substantial difference in the rainband precipitation structure is observed, with deeper convection and stronger updraft features during development than at the mature phase, when also shallow precipitation/warm rain processes are observed in the inner region around the medicane eye. These features play a key role to explain the substantial drop in lightning activity during Ianos mature phase. Graupel-ice electrification process is inhibited due to the combined effect of strong horizontal wind and the observed limited growth of graupel. The study demonstrates the value of the GPM-CO not only to characterize Medicane Ianos precipitation structure and microphysics processes with unprecedented detail, but also to provide evidence of its exceptional intensity, tropical-like characteristics during its mature phase, and its similarities with tropical cyclones.

Experimental Study of Downburst Wind Flow over a Typical Three-Dimensional Hill

To achieve a comprehensive understanding of a three-dimensional (3D) wind field and the speed-up phenomenon in a downburst wind flow over a 3D hilly terrain, a succession of laboratory tests utilizing 12 hill models with cosine-squared cross-section was conducted using a physical downburst simulator with a jet diameter of 0.6 m. By placing the models in the strong horizontal wind region and the strong vertical wind region, the corresponding wind profiles for both the horizontal and vertical velocities were measured. It was found that the wind flowed predominantly over the crest of the hill in the case of low hills, whereas wind flow around the hill body became increasingly pronounced as the hill height increased. In addition, the speed-up region, where the horizontal wind velocity exceeds the impinging jet velocity, was identified, and found to move from the crest to the two sides of the hill as the hill height increased. Accordingly, the most significant topographic multipliers of all locations on the hill might appear at the crest, the hill foot, or elsewhere, depending largely on the hill height. Among all cases, the maximum topographic multiplier was 1.12, and occurred at the ridge, while the ratio of hill height to jet height was 5/12. Additionally, empirical equations are presented to facilitate the determination of wind loads induced by a downburst flow over an isolated hill.

Correction to raindrop size distributions measured by PARSIVEL disdrometers in strong winds

Particle Size and Velocity (PARSIVEL) disdrometers have been widely applied in studies of the precipitation microphysics of tropical cyclones (TCs). However, few studies have focused on the accuracy of PARSIVEL data in the strong-wind environments induced by TCs. This work examines the performance of PARSIVEL under strong horizontal-wind conditions using data collected from four typhoon field experiments in China during 2014–2018. Observational data from a PARSIVEL disdrometer is compared to a collocated automatic weather station (AWS) onboard a mobile observation vehicle. It is shown that the integral rain rate derived from PARSIVEL is smaller than the AWS data, and the underestimation increases gradually with wind speed. This bias results partly from measurement errors of raindrop diameter and fall velocity due to the drifting and tilting of raindrops as they fall. The bias is particularly prominent in the case of large raindrops (>4 mm) in strong horizontal wind. To account for the canting and incidence angles of raindrops entering the sampling area, a wind-adjusted quality control (QC) method is developed by adding a correction module that complements existing QC methods. The validation of the corrected disdrometer data against AWS data demonstrates that this modified QC method presents a remarkable improvement for the wind-dependent underestimation of rain rates from PARSIVEL. For instance, when the wind speed exceeds 14 m s−1, the mean error in rain rate derived from PARSIVEL for 5 min of rainfall with (without) the complementary correction module in QC procedures is −11.8% (−22.4%), in comparison with the AWS data.

Large‐Scale Dune Aurora Event Investigation Combining Citizen Scientists' Photographs and Spacecraft Observations

AbstractRecently, citizen scientist photographs led to the discovery of a new auroral form called “the dune aurora” which exhibits parallel stripes of brighter emission in the green diffuse aurora at about 100 km altitude. This discovery raised several questions, such as (i) whether the dunes are associated with particle precipitation, (ii) whether their structure arises from spatial inhomogeneities in the precipitating fluxes or in the underlying neutral atmosphere, and (iii) whether they are the auroral manifestation of an atmospheric wave called a mesospheric bore. This study investigates a large‐scale dune aurora event on 20 January 2016 above Northern Europe. The dunes were observed from Finland to Scotland, spanning over 1,500 km for at least 4 h. Spacecraft observations indicate that the dunes are associated with particle precipitation and reveal the presence of a temperature inversion layer below the mesopause during the event, creating suitable conditions for mesospheric bore formation. The analysis of a time lapse of pictures by a citizen scientist from Scotland leads to the estimate that, during this event, the dunes propagate toward the west‐southwest direction at about 200 m s−1, presumably indicating strong horizontal winds near the mesopause. These results show that citizen science and dune aurora studies can fill observational gaps and be powerful tools to investigate the least‐known region of near‐Earth space at altitudes near 100 km.

Lagrangian trajectories at the outflow of tropical cyclones

AbstractRecent observations from the upper levels of tropical cyclones show the development of a Low engulfed by a larger High. The impact of such a geopotential map on the dynamics of the outflow is studied by analysing the Lagrangian trajectories of air parcels. The geopotential is modelled by the hydrostatic sum of two, oppositely signed, Gaussians: a warm core and a near‐surface low that together reproduce the relevant features of the observed tropical cyclones. Assuming a time‐independent and axisymmetric geopotential map, the dynamics is described by an integrable, two degrees‐of‐freedom, angular momentum conserving, Hamiltonian system with a single non‐dimensional parameter. The steady states of this system bifurcate when the geopotential amplitude increases above a threshold where the single elliptic fixed‐point becomes hyperbolic surrounded by a pair of elliptic fixed‐points. A gradient balance prevails near the elliptic points while an inertial balance occurs at the radius of maximum geopotential, where the hyperbolic (unstable) point is located. The divergence of trajectories around this hyperbolic point implies the existence of strong horizontal wind divergence. A gradient non‐balance region emerges in the steady state (radius, geopotential amplitude) map and this region expands with the increase of geopotential amplitude which implies that higher angular momentum values are required for trajectories to transition from high to low. A transformation of the (radius, radial velocity) variables to action‐angle variables yields an approximate expression for the tangential drift (long‐time average of the tangential speed) that estimates the tangential winds. The analysis is extended numerically to the case of warm core offset, where the two Gaussians have different centres.

Horizontal Vortex Tubes near a Simulated Tornado: Three-Dimensional Structure and Kinematics

Supercell thunderstorms can produce a wide spectrum of vortical structures, ranging from midlevel mesocyclones to small-scale suction vortices within tornadoes. A less documented class of vortices are horizontally-oriented vortex tubes near and/or wrapping about tornadoes, that are observed either visually or in high-resolution Doppler radar data. In this study, an idealized numerical simulation of a tornadic supercell at 100 m grid spacing is used to analyze the three-dimensional (3D) structure and kinematics of horizontal vortices (HVs) that interact with a simulated tornado. Visualizations based on direct volume rendering aided by visual observations of HVs in a real tornado reveal the existence of a complex distribution of 3D vortex tubes surrounding the tornadic flow throughout the simulation. A distinct class of HVs originates in two key regions at the surface: around the base of the tornado and in the rear-flank downdraft (RFD) outflow and are believed to have been generated via surface friction in regions of strong horizontal near-surface wind. HVs around the tornado are produced in the tornado outer circulation and rise abruptly in its periphery, assuming a variety of complex shapes, while HVs to the south-southeast of the tornado, within the RFD outflow, ascend gradually in the updraft.

The Effect of 3D Transport-induced Disequilibrium Carbon Chemistry on the Atmospheric Structure, Phase Curves, and Emission Spectra of Hot Jupiter HD 189733b

Abstract On hot Jupiter exoplanets, strong horizontal and vertical winds should homogenize the abundances of the important absorbers CH4 and CO much faster than chemical reactions restore chemical equilibrium. This effect, typically neglected in general circulation models (GCMs), has been suggested to explain discrepancies between observed infrared light curves and those predicted by GCMs. On the nightsides of several hot Jupiters, GCMs predict outgoing fluxes that are too large, especially in the Spitzer 4.5 μm band. We modified the SPARC/MITgcm to include disequilibrium abundances of CH4, CO, and H2O by assuming that the CH4/CO ratio is constant throughout the simulation domain. We ran simulations of hot Jupiter HD 189733b with eight CH4/CO ratios. In the more likely CO-dominated regime, we find temperature changes ≥50–100 K compared to the simulation for equilibrium chemistry across large regions. This effect is large enough to affect predicted emission spectra and should thus be included in GCMs of hot Jupiters with equilibrium temperatures between 600 and 1300 K. We find that spectra in regions with strong methane absorption, including the Spitzer 3.6 and 8 μm bands, are strongly impacted by disequilibrium abundances. We expect chemical quenching to result in much larger nightside fluxes in the 3.6 μm band, in stark contrast to observations. Meanwhile, we find almost no effect on predicted observations in the 4.5 μm band, because the changes in opacity due to CO and H2O offset each other. We thus conclude that disequilibrium carbon chemistry cannot explain the observed low nightside fluxes in the 4.5 μm band.

Simulation of atmospheric dispersion of airborne effluent releases at a tropical coastal site under sea-breeze circulation and internal boundary layer development

In this study the impact of land–sea breeze circulation and internal boundary layer (IBL) on the atmospheric dispersion of airborne effluent releases at the tropical coastal site Kalpakkam is simulated using mesoscale model WRF and Lagrangian particle dispersion model FLEXPART. Simulations with WRF are conducted for typical days in different seasons, i.e., 3 May 2011 (summer), 20 Sep 2010 and 20 Jun 2011 (southwest monsoon). Two K-based non-local turbulence closures (YSU, ACM) and two TKE-based local closures (MYNN, MYJ) in WRF are tested for simulating the sea breeze and IBL. Observations from a 50-m meteorological tower, GPS Sonde, and a Doppler SODAR are used for validation. Simulations indicate that the synoptic flow largely influences the characteristics of the sea breeze at the site. Results show that the sea breeze is more predominant with early onset and it is characterized by deep inland penetration, strong horizontal and vertical winds and is associated with formation of a deep IBL relative to monsoon with opposing large-scale flow. The YSU non-local diffusion scheme and the higher order local TKE closure (MYNN) simulated the sea breeze and IBL characteristics in good agreement with observations. Dispersion simulations with a hypothetical tracer release using FLEXPART showed relatively high ground-level concentrations during IBL formation in the daytime and during stable off-shore flow condition in the morning time. The coupled mesoscale dispersion model could simulate the plume trajectory and buildup of concentrations during sea-breeze time by realistically simulating the winds and mixed-layer characteristics at the coastal site.

Vertical fine structure and time evolution of plasma irregularities in the Es layer observed by a high-resolution Ca+ lidar

The vertical fine structures and the time evolution of plasma irregularities in the sporadic E (Es) layer were observed via calcium ion (Ca+) density measurements using a resonance scattering lidar with a high time-height resolution (5 s and 15 m) at Tachikawa (35.7°N, 139.4°E) on December 24, 2014. The observation successfully provided clearer fine structures of plasma irregularities, such as quasi-sinusoidal height variation, localized clumps, “cats-eye” structures, and twist structures, in the sporadic Ca+ ({{text{Ca}}^{+}}_{text{s}}) layers at around 100 km altitude. These fine structures suggested that the Kelvin–Helmholtz instabilities occurred in the neutral atmosphere whose density changed temporarily or spatially. The maximum Ca+ density in the {{text{Ca}}^{+}}_{text{s}} layer was two orders of magnitude smaller than the maximum electron density estimated from the critical frequency (foEs) simultaneously observed by the ionosonde at Kokubunji (35.7°N, 139.5°E). A strong positive correlation with a coefficient of 0.91 suggests that Ca+ contributes forming the Es layer as well as major metallic ions Fe+ and Mg+ in the lower thermosphere. Moreover, the formation of a new {{text{Ca}}^{+}}_{text{s}} layer at 110 km and the upward motions of the {{text{Ca}}^{+}}_{text{s}} layers at 100 km and 110 km were observed before the local sunrise and just after the sunrise time at the conjugation point. Although the presence or absence of a causal relationship with the sunrise time was not clear, a possible explanation for the formation and the upward motions of the {{text{Ca}}^{+}}_{text{s}} layers was the occurrence of strong horizontal wind, rather than the enhancement of the eastward electric field.

Nocturnal surface ozone enhancement over Portugal during winter: Influence of different atmospheric conditions

Four distinct nocturnal surface ozone (NSO) enhancement events were observed, with NSO concentration exceeding 80μg/m3, at multiple ozone (O3) monitoring stations (32 sites) in January, November and December between year 2000–2010, in Portugal. The reasonable explanation for the observed bimodal pattern of surface ozone with enhanced NSO concentration during nighttime has to be transport processes, as the surface ozone production ceases at nighttime. Simultaneous measurements of O3 at multiple stations during the study period in Portugal suggest that horizontal advection alone cannot explain the observed NSO enhancement. Thus, detailed analysis of the atmospheric conditions, simulated with the Weather Research and Forecasting (WRF) model, were performed to evaluate the atmospheric mechanisms responsible for NSO enhancement in the region. Simulations revealed that each event occurred as a result of one or the combination of different atmospheric processes such as, passage of a cold front followed by a subsidence zone; passage of a moving surface trough, with associated strong horizontal wind speed and vertical shear; combination of vertical and horizontal transport at the synoptic scale; formation of a low level jet with associated vertical mixing below the jet stream. The study confirmed that large-scale flow pattern resulting in enhanced vertical mixing in the nocturnal boundary layer, plays a key role in the NSO enhancement events, which frequently occur over Portugal during winter months.

WHIRL WIND DETECTION AND IDENTIFICATION IN INDONESIA UTILIZING SINGLE POLARIZATION DOPPLER WEATHER RADAR VOLUMETRIC DATA

Abstract. Whirl wind occurrence frequency in Indonesia tends increasing in the last five years. Geospatial data from National Agency for Disaster Management (BNPB) recorded 72 cases with the impact of the two victims died, ten injured, 485 people were evacuated, and 1285 buildings were destroyed at period of January-June 2015. Based on the impact, early warning through remote sensing by using single polarization Doppler weather radar is need to be efforted. Whirl wind detection is done by identifying the characteristic pattern of the rotating convective cloud system by hook echo, analyzing the exsistance of vortex and rotation, and the strength of turbulence. The results show horizontal wind profile with a rotational pattern at CAPPI (V) and HWIND (V) by the altitude of 0.5 km, strong turbulence through product CAPPI (W) 0.5 km ranged of 1.75-2.05 ms-1, the vertical wind profile by product VVP (V) with a maximum value updraft reaches more than 20 knots at a 100-200 meters height, strong horizontal wind shear through HSHEAR (V) and CAPPI (HSHEAR) altitude of 0.5 km with a range of 6.23 to 10.12 ms-1/km. SWI and SSA show that the cloud base height is very low ranged from 200-600 meters with a maximum reflectivity reached 61.5 dBZ by top cloud height reached 14 km, while the product CAPPI (Z) 0.5 km and CMAX (Z) is very difficult to identify patterns hook echo. The results of remote sensing are very representative with the physical properties of whirl wind even whirl wind in a smaller scale.

WHIRL WIND DETECTION AND IDENTIFICATION IN INDONESIA UTILIZING SINGLE POLARIZATION DOPPLER WEATHER RADAR VOLUMETRIC DATA

Whirl wind occurrence frequency in Indonesia tends increasing in the last five years. Geospatial data from National Agency for Disaster Management (BNPB) recorded 72 cases with the impact of the two victims died, ten injured, 485 people were evacuated, and 1285 buildings were destroyed at period of January-June 2015. Based on the impact, early warning through remote sensing by using single polarization Doppler weather radar is need to be efforted. Whirl wind detection is done by identifying the characteristic pattern of the rotating convective cloud system by hook echo, analyzing the exsistance of vortex and rotation, and the strength of turbulence. The results show horizontal wind profile with a rotational pattern at CAPPI (V) and HWIND (V) by the altitude of 0.5 km, strong turbulence through product CAPPI (W) 0.5 km ranged of 1.75-2.05 ms-1, the vertical wind profile by product VVP (V) with a maximum value updraft reaches more than 20 knots at a 100-200 meters height, strong horizontal wind shear through HSHEAR (V) and CAPPI (HSHEAR) altitude of 0.5 km with a range of 6.23 to 10.12 ms-1/km. SWI and SSA show that the cloud base height is very low ranged from 200-600 meters with a maximum reflectivity reached 61.5 dBZ by top cloud height reached 14 km, while the product CAPPI (Z) 0.5 km and CMAX (Z) is very difficult to identify patterns hook echo. The results of remote sensing are very representative with the physical properties of whirl wind even whirl wind in a smaller scale.

大气重力波引起的偶发钠层研究

The sporadic sodium layers(SSL) caused by atmospheric gravity waves over Langfang(39N, 116E) is studied by using the sodium fluorescence Doppler lidar and the meteor radar detection data of the near space environment comprehensive exploration station, Chinese Academy of Sciences. Firstly, the phase relationship between the atmospheric horizontal wind and vertical wind field was calculated and analyzed by the atmospheric gravity wave equation. Secondly, the SSL caused by atmospheric gravity waves was analyzed by the experimental data of the sodium fluorescence lidar and the meteor radar. The results show that the accumulation and joint action of the strong horizontal wind shear and vertical wind field direction caused by the atmospheric gravity wave increases the density of sodium atoms and form the SSL.

大气重力波引起的偶发钠层研究

The sporadic sodium layers(SSL) caused by atmospheric gravity waves over Langfang(39N, 116E) is studied by using the sodium fluorescence Doppler lidar and the meteor radar detection data of the near space environment comprehensive exploration station, Chinese Academy of Sciences. Firstly, the phase relationship between the atmospheric horizontal wind and vertical wind field was calculated and analyzed by the atmospheric gravity wave equation. Secondly, the SSL caused by atmospheric gravity waves was analyzed by the experimental data of the sodium fluorescence lidar and the meteor radar. The results show that the accumulation and joint action of the strong horizontal wind shear and vertical wind field direction caused by the atmospheric gravity wave increases the density of sodium atoms and form the SSL.