Characteristics of turbulence in the troposphere and lower stratosphere over the Indian Peninsula

Sunilkumar, S. V.; Muhsin, M.; Parameswaran, K.; Ratnam, M. Venkat; Ramkumar, Geetha; Rajeev, K.; Murthy, B. V. Krishna; Namboodiri, Krishnan; Subrahmanyam, K. V.; Kumar, Karanam Kishore; Das, Siddarth Shankar

doi:10.1016/j.jastp.2015.07.015

Cited by 36 publications

(45 citation statements)

References 48 publications

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“…In Birner et al () and Zhang et al (), the mean shear is obtained from the tropopause‐relative coordinates, while the temporal and zonal mean shown in Figure is calculated on conventional coordinates. On the other hand, the largest instantaneous shear values at the tropopause from the simulation is comparable with observations: the simulated shears at the equator (Figure c) reach 50 ms −1 km −1 , which is in good agreement with radionsonde measurements in tropical region (Trivandrum) (Sunilkumar et al, ). At 45° N (Figure d), the simulated shears can reach 25 ms −1 km −1 , nearly twice as large as the reported mean values of summer months.…”

Section: Results and Analysismentioning

confidence: 99%

“…Statistics of the simulated large wind shear at the mesopause compare well with statistics from lidar observations at Ft. Collins (Yue et al, ). At the tropopause, wind shear peaks are observed both at tropical latitudes (Sunilkumar et al, ) and midlatitudes (Birner et al, ; Zhang et al, ). The simulated wind shears show similar peaks, although the mean shear values are somewhat less than the mean observed values.…”

Section: Discussion and Summarymentioning

confidence: 99%

“…Slightly larger peak shear values (∼20 ms −1 km −1 ) above the tropopause were obtained from an analysis of radiosonde measurements at another midlatitude station (Boise, Idaho) by Zhang et al (). At tropical latitudes, radiosonde analysis by Sunilkumar et al () found that the average wind shear above the tropical tropopause layer (TTL) is 24 ms −1 km −1 at Trivandrum and 19 ms −1 km −1 at Gadanki during summer monsoon months, with short‐term values up to 45 ms −1 km −1 and 30 ms −1 km −1 , respectively.…”

Section: Introductionmentioning

confidence: 99%

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Large Wind Shears and Their Implications for Diffusion in Regions With Enhanced Static Stability: The Mesopause and the Tropopause

Liu

2017

JGR Atmospheres

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The NCAR Whole Atmosphere Community Climate Model, with a quasi‐uniform horizontal resolution of ∼25 km and a vertical resolution of 0.1 scale height, produces large vertical shear of horizontal wind with peaks around the mesopause and the tropical and midlatitude tropopause. In these regions, the static stability also reaches peak values and therefore allows large vertical shears before the onset of dynamical instability. The wind shear peaks near the mesopause and the tropopause from the simulation compare well with those identified in observations, including the magnitude, latitudinal dependence, and large shear statistics. By analyzing the probability density functions of the wind shears and their dependence on the zonal scales, it is found that smaller scale processes, likely gravity waves, contribute significantly to the large shears and may play a dominant role in producing the largest shears. Climatological tidal waves have secondary contribution to the large winds and shears, but spectral analysis suggests that they can modulate wind shear perturbations by gravity waves in the mesosphere and lower thermosphere. Implications for tracer transport and mixing in these regions are explored by estimating diffusion coefficients based on the root‐mean‐square winds, shears, and corresponding spatial scales from model results.

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Section: Results and Analysismentioning

confidence: 99%

Section: Discussion and Summarymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Large Wind Shears and Their Implications for Diffusion in Regions With Enhanced Static Stability: The Mesopause and the Tropopause

Liu

2017

JGR Atmospheres

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“…Based on radiosonde observations, Sunilkumar et al . [] demonstrated that static instability (convective instability) dominates below 15 km and dynamic instability (induced by vertical shear of horizontal wind) dominates above 15 km. These instabilities are capable of generating small‐scale turbulence in this region.…”

Section: Resultsmentioning

confidence: 99%

“…Simultaneous GPS radiosonde launches are carried out from Trivandrum and Gadanki, at 3‐hourly intervals for three consecutive days (to have ~24 profiles) in each month for a period of 40 months from December 2010 to March 2014 as part of the tropical tropopause dynamics (TTD) experiment [ Ratnam et al , ; Sunilkumar et al , ] under Climate and Weather of the Sun‐Earth System (CAWSES) India Phase II program. Trivandrum is located in the peninsular India, very near to the Arabian Sea Coast.…”

Section: Methodsmentioning

confidence: 99%

Boundaries of tropical tropopause layer (TTL): A new perspective based on thermal and stability profiles

et al. 2017

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The structure of tropical tropopause layer (TTL) is delineated based on static stability criteria. It is defined as the region extending from the level of minimum static stability to the level of maximum static stability. The static stability and dynamic instability steadily increase from the base to the top of the TTL. Radiosonde data from three tropical stations and Constellation Observing System for Meteorology, Ionosphere, and Climate GPS radio occultation (COSMIC) data over the tropics are used for this investigation. This study suggests that in terms of stability, the TTL can further be considered as a composite of three sublayers: a bottom layer (BL), a middle layer (ML), and an upper layer (UL) embedded between the potential temperatures ~350–360 K, ~360–380 K, and 380–420 K, respectively. While the BL is significantly influenced by frequent convective outflows, the influence of convection declines across the ML. Ozone and water vapor mixing ratios show a discernible change in their gradients across these sublayers. Occurrences of small‐scale turbulence and cirrus are maximum in the BL and decrease in the ML and UL. Longitudinally, the BL is broad and the ML and UL are narrow over the deep convective cores. Strength of static stability in the UL (BL) is relatively strong (weak) centered about the equator, with pronounced features over the deep convective regions. These features of static stability centered about the equator in the BL could be attributed to the convective outflows in the troposphere and that in the UL to the dynamic and radiative processes in the upper troposphere and lower stratosphere.

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Seasonal and Diurnal Variations of Tropical Tropopause Layer (TTL) Over the Indian Peninsula

et al. 2017

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Seasonal and diurnal variations in the thermal structure of the troposphere and lower stratosphere with special reference to the tropical tropopause layer (TTL) are studied using data from 3 h interval radiosonde launches carried out simultaneously from Trivandrum (8.5°N, 76.9°E) and Gadanki (13.5°N,79°E) during December 2010 to March 2014. TTL is defined as the region extending from the level of minimum stability (LMinS) to the level of maximum stability (LMaxS). Above the cold point tropopause (CPT), temperature showed warm anomaly (4–5 K) during summer monsoon (June–September) and cold anomaly (up to −4 K) during winter (December–February). The temperature in the troposphere showed a clear diurnal variation (±0.5 K) with a cold anomaly during early morning and warm anomaly during the day in all the seasons. At Gadanki, the diurnal temperature anomaly in the lower stratosphere showed its phase propagating downward with time, whereas at Trivandrum such variations are not clearly evident. At diurnal timescales, the TTL showed significant variations at LMinS (0.5–1.5 km/5–7 K) and smaller variations at CPT (0.2–0.5 km/2–3 K). In general, the amplitude of the diurnal component is greater than the semidiurnal component for all the TTL parameters, and these amplitudes are relatively larger at Trivandrum than at Gadanki. The observed diurnal variations could be the manifestation of tidal oscillations and/or due to the influence of local convection. Correlation analysis between different TTL parameters indicated a slow transition from a governing adiabatic process in the TTL base to a diabatic process at the TTL top.

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Characteristics of turbulence in the troposphere and lower stratosphere over the Indian Peninsula

Cited by 36 publications

References 48 publications

Large Wind Shears and Their Implications for Diffusion in Regions With Enhanced Static Stability: The Mesopause and the Tropopause

Large Wind Shears and Their Implications for Diffusion in Regions With Enhanced Static Stability: The Mesopause and the Tropopause

Boundaries of tropical tropopause layer (TTL): A new perspective based on thermal and stability profiles

Seasonal and Diurnal Variations of Tropical Tropopause Layer (TTL) Over the Indian Peninsula

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