The purpose of this paper is to introduce a new chaotic oscillator. Although different chaotic systems have been formulated by earlier researchers, only a few chaotic systems exhibit chaotic ...behaviour. In this work, a new chaotic system with chaotic attractor is introduced. It is worth noting that this striking phenomenon rarely occurs in respect of chaotic systems. The system proposed in this paper has been realized with numerical simulation. The results emanating from the numerical simulation indicate the feasibility of the proposed chaotic system. More over, chaos control, stability, diffusion and synchronization of such a system have been dealt with.
In this study, we have examined the characteristics of high‐frequency gravity waves (5–50 min periodicity) over a tropical region using the mesosphere‐stratosphere‐troposphere (MST) radar installed ...at Gadanki (13.5°N, 79.2°E), India. The MST radar (53 MHz) was operated continuously for ∼15.5 h during 1700–0840 LT on 2–3 June 2005. During this period, a strong unstable wind shear region existed above the tropical easterly jet at the height of tropopause. This has provided an excellent opportunity to study the characteristics of internal atmospheric high‐frequency (∼15–40 min periodicity) gravity waves, generated in the boundary layer and passing through the shear layer. The study reveals the generation of higher‐frequency (5–15 min periodicity) gravity waves from this strong shear region and their vertical propagation both below up to a few kilometers and above the shear layer (∼0.5 km thick). These waves showed upward propagation even above 20 km in the lower stratosphere, indicating that unstable shear layers are the important source of momentum and energy fluxes that contribute significantly to the middle atmospheric dynamics in terms of gravity waves. Further, a close association was also observed between the dissipating gravity waves and the distinctly enhanced signal‐to‐noise ratio and Doppler spectral width of the MST radar echoes. The present observation of radiation of high‐frequency gravity waves that propagate vertically upward from a strong wind shear region located immediately below a highly stratified layer is in accordance with the “direct mechanism” explained by nonlinear numerical simulation studies. For the first time, the present study illustrates the existence of layers of polarized refractive index structures in the heights of 10–15 km.
Long-period modulations are shown in aerosol optical depth measured by the Microtops II Sun photometer over a high-altitude site the central Himalayan region (Nainital, 29.4° N, 79.5° E, 1958 m ...a.m.s.l.) for the first time. Fourier analysis of aerosol optical depth showed dominant 25–45 day oscillations observed in MODerate-resolution Imaging Spectro radiometer data. Further, a Hovmiller diagram showed westward (northward) propagation at a different longitude (latitude), confirming that the modulations are associated with Rossby waves. It is also shown that the Rossby wave amplitude causes an additional warming of 4.16 ± 0.98 W m−2 over the observational site. Hence, the present study illustrates the importance of wave-induced aerosol dynamics and the corresponding radiative effects.
Using MST Radar located at the Indian tropical station of Gadanki (13.5°N, 79.2°E; near the eastern coast of India), studies have been made on the characteristics of inertia‐gravity waves generated ...in the lower troposphere during deep depression developed over the Bay of Bengal on 20–24 June 2007. Filtering and the hodograph analyses of horizontal winds indicate that the low‐pressure system has generated inertia gravity waves, propagating outward from the core of the depression. Strong enhancement of radar reflectivity (SNR) in the heights of ∼4–7 km for a few days around 22 June 2007 and the upward propagation of gravity wave energy above this height range indicate that the source of the waves is located at ∼4–7 km. This is in agreement with earlier theoretical expectations. The vertical and horizontal wavelengths of gravity waves are found to be ∼2.2 km and ∼240 km respectively in the troposphere.
In this study, for the first time, planetary wave signatures in ionospheric Total Electron Content (TEC) retrieved from global positioning service (GPS), mesospheric wind and temperature at low ...latitude station has been identified during January–February 2009. Our investigations revealed that planetary waves with 3–5 days periodicity characterized as ultrafast Kelvin (UFK) waves caused by stratospheric warming event during January 2009. The UFK waves are observed to be propagated from lower atmosphere to ionosphere. The UFK perturbations during SSW event are discussed in the light of current understanding of role of non linear interaction of planetary waves to modulate low latitude ionosphere.
•Generation of UFK waves in low-latitude ionospheric TEC.•UFK wave signatures during Sudden Stratospheric warming event.•Vertical and Lateral Propagation characteristics of UFK waves.
A Doppler lidar was installed at Manora Peak, Nainital (29.4°N; 79.2°E; 1958 amsl) to estimate mixing layer height for the first time by using vertical velocity variance as basic measurement ...parameter for the period September–November 2011. Mixing layer height is found to be located ~0.57±0.1 and 0.45±0.05km AGL during day and nighttime, respectively. The estimation of mixing layer height shows good correlation (R2>0.8) between different instruments and with different methods. Our results show that wavelet co-variance transform is a robust method for mixing layer height estimation.
•Estimation of mixing layer height over Central Himalayan region for the first time.•Diurnal variation of mixing layer height over a high altitude site.•Mixing layer height estimation by using three different instruments and different methods.
This study reports characteristics of inertia‐gravity waves (IGWs) in the atmospheric boundary layer during the passage of Tropical Cylone‐03B, using the Doppler Sound Detection and Ranging (SODAR) ...observations at the Indian tropical station of Gadanki (13.45°N, 79.2°E; near the east coast of India). Wavelet analysis of horizontal winds indicates significant wave motion (˜60 h) near the characteristic inertial period. The hodograph analysis of the filtered winds shows an anti‐cyclonic turning of horizontal wind with height and time, indicating the presence of IGW. This study finds important implications in boundary layer dynamics during the passage of tropical cyclones.
Doppler Lidar and Multi-Filter Rotating Shadowband Radiometer (MFRSR) observations are utilized to show wave like signatures in aerosol optical depth (AOD) during daytime boundary layer evolution ...over the Himalayan region. Fourier analysis depicted 60–80min periods dominant during afternoon hours, implying that observed modulations could be plausible reason for the AOD forenoon–afternoon asymmetry which was previously reported. Inclusion of wave amplitude in diurnal variation of aerosol radiative forcing estimates showed ~40% additional warming in the atmosphere relative to mean AOD. The present observations emphasize the importance of wave induced variations in AOD and radiation budget over the site.
•Wave like signatures in aerosol optical depth over the central Himalayan region.•60–80min period oscillations dominant during afternoon hours.•Inclusion of wave amplitude in diurnal variation of aerosol radiative forcing.•Additional warming (cooling) in the atmosphere (surface) due to wave dynamics.
This paper deals with the investigation of long-term variability of atmospheric dust over the United Arab Emirates (UAE). The climatology of dust episodes (dust events, dust storms, and severe dust ...storms) is compiled based on the hourly observations and synoptic codes recorded at four different stations over UAE between the years 1983–2014. The diurnal, temporal, monthly, and inter-annual variations of dust episodes and their relation with the mean wind speed, maximum wind speed, and temperature are discussed. Dust episodes show a clear diurnal variation in all the stations. The duration of dust storms is large compared to dust events. For instance, dust events over the UAE persist for 2–5 h while dust storms last for about 5–11 h. Dust storms also show clear seasonal variability with the maximum occurring during winter and the minimum during summer whereas most of the dust events occur during the months of March and April. The inter-annual variation of dust events shows a significant decrease while dust storms depict a moderate increase over the UAE. The synoptic scale climatology of all dust storms is also analyzed and shows changes in wind direction to the south-west prior to 2 days of the dust storm generation. The climatology of wind direction and wind speed during the dust episode indicates that 90% of dust episodes are coming from the southwest direction. These observed results are discussed in light of the current global warming scenarios with a special emphasis on the role of dust episodes on the regional enhancement of temperature.
•The dust episodes show a clear diurnal variation over the UAE.•The dust events (dust storms) over the UAE persist for 6–14 (2–5) hours.•99% of dust episodes are coming from southwest direction.•Dust storms shows an increasing trend over the UAE.•Maximum number of dust storms occurs during the winter than summer.
Hight-resolved observations of vertical winds remain nearly non-existing over the Himalayas, despite of anticipated crucial role of vertical motions in transporting pollution across the Himalayan ...hills. The present study analyze the vertical wind observations from surface to 1 km above ground level over Manora Peak (29.4° N; 79.5° E; 1958 m amsl) in the Himalaya performed using a Doppler Lidar during the Ganges Valley Aerosol Experiment (GVAX). Vertical wind exhibited a pronounced diurnal variability at Manora Peak comprising of upward motions during the daytime (05–10 UT) and downward motions during nighttime typical of a mountain-valley system. Mean vertical wind speeds are observed to be varying from −0.8 to +0.8 ms−1 during the study period with a variance of 0.1–1.5 m2s-2, which is attributed to the thermally driven turbulence. Mean vertical winds are observed to be stronger in the Doppler Lidar profiles above Manora Peak (−0.8 to 0.8 ms−1) as compared to near surface measurements at this station using an ultrasonic anemometer (−0.4 to 0.4 ms−1), and low altitude stations in India. Daytime vertical wind speeds are observed to be higher during pre-monsoon (0.81 ms−1), as compared to post-monsoon (0.24 ms−1) and winter (0.33 ms−1). Average Black Carbon (BC) concentrations are significantly higher during strong upward vertical winds, which indicates efficient transport of polluted air mass from low-altitude regions to the Himalaya. Weather Research and Forecasting (WRF) model reproduces the observed diurnal pattern in the vertical wind at the observation site however the model underestimates the variability.
•Vertical wind dynamics over the Himalaya using Doppler Lidar.•A pronounced mountain-valley wind system observed in the vertical wind observations over the site.•Weather Research and Forecasting (WRF) model reproduces the observed diurnal pattern in vertical wind at the observation site.
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