MST radar and radiosonde observations of inertia‐gravity wave climatology over tropical stations: Source mechanisms

Ratnam, M. Venkat; Babu, A. Narendra; Rao, V. Ramgopal; Rao, Sandhya; Rao, D. Narayana

doi:10.1029/2007jd008986

Cited by 50 publications

(70 citation statements)

References 33 publications

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“…A clear annual oscillation can be noticed in both zonal and meridional velocities. Similar variations are also observed by the MST radar located at the same site in between 4 and 20 km (Ratnam et al, 2008;Basha and Ratnam, 2009;Debashis Nath et al, 2009). …”

Section: Background Meteorological Conditions Obtained During the Balsupporting

confidence: 68%

Assessment of GPS radiosonde descent data

et al. 2014

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Abstract. Radiosondes are widely used to obtain basic meteorological parameters such as pressure (P ), temperature (T ), relative humidity (RH) and horizontal winds during the balloon ascent up to the altitude of balloon burst, usually ∼ 32-35 km. Data from the radiosondes released from Gadanki (13.5 • N, 79.2 • E), a tropical station in India, have been collected during the ascent and during the descent as well without attaching any parachute or its equivalent since the year 2008. In the present study an attempt has been made to characterize the radiosonde descent data with the main objective of exploring its usefulness and reliability for scientific purposes. We compared the data obtained during ascent and descent phases of the same sounding. The mean differences in T , RH and horizontal winds between ascent and descent data are found to be small and are sometimes even within the uncertainty of the measurements and/or expected diurnal variation itself. The very good consistency observed between the ascent and the descent data shows that one more profile of the meteorological parameters can be constructed within 3 h of time of balloon launch practically at no additional cost. Further checks are done by utilizing the 3-hourly radiosonde observations collected during the Tropical Tropopause Dynamics campaigns conducted at Gadanki. In the process of checking the consistency between the radiosonde ascent and descent data, several new findings are arrived at and are reported in this study. In general, it has taken more than half an hour for the balloon to reach the ground from the burst altitude. It is also observed that the fall velocity is close to 10 m s −1 near the surface. Finally, it is suggested to record the observations also when the balloon is descending as this information is useful for scientific purposes.

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Section: Background Meteorological Conditions Obtained During the Balsupporting

confidence: 68%

Assessment of GPS radiosonde descent data

et al. 2014

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“…A clear annual oscillation can be noticed in both zonal and meridional velocities. Similar variations are also observed by the MST radar located at the same site between 4 and 20 km (Venkat Ratnam et al, 2008;Basha and Ratnam, 2013;Nath et al, 2009). Monthly mean OLR around Gadanki at 17:30 LT is shown in Fig.…”

Section: Background Meteorological Conditionssupporting

confidence: 65%

Cloud vertical structure over a tropical station obtained using long-term high-resolution radiosonde measurements

et al. 2018

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Abstract. Cloud vertical structure, including top and base altitudes, thickness of cloud layers, and the vertical distribution of multilayer clouds, affects large-scale atmosphere circulation by altering gradients in the total diabatic heating and cooling and latent heat release. In this study, longterm (11 years) observations of high-vertical-resolution radiosondes are used to obtain the cloud vertical structure over a tropical station at Gadanki (13.5 • N, 79.2 • E), India. The detected cloud layers are verified with independent observations using cloud particle sensor (CPS) sonde launched from the same station. High-level clouds account for 69.05 %, 58.49 %, 55.5 %, and 58.6 % of all clouds during the premonsoon, monsoon, post-monsoon, and winter seasons, respectively. The average cloud base (cloud top) altitudes for low-level, middle-level, high-level, and deep convective clouds are 1.74 km (3.16 km), 3.59 km (5.55 km), 8.79 km (10.49 km), and 1.22 km (11.45 km), respectively. Singlelayer, two-layer, and three-layer clouds account for 40.80 %, 30.71 %, and 19.68 % of all cloud configurations, respectively. Multilayer clouds occurred more frequently during the monsoon with 34.58 %. Maximum cloud top altitude and cloud thickness occurred during the monsoon season for single-layer clouds and the uppermost layer of multiple-layer cloud configurations. In multilayer cloud configurations, diurnal variations in the thickness of upper-layer clouds are larger than those of lower-layer clouds. Heating and cooling in the troposphere and lower stratosphere due to these cloud layers are also investigated and peak cooling (peak warming) is found below (above) the cold-point tropopause (CPT) altitude. The magnitude of cooling (warming) increases from single-layer to four-or more-layer cloud occurrence. Further, the vertical structure of clouds is also studied with respect to the arrival date of the Indian summer monsoon over Gadanki.

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“…Further, as it assumes monochromatic waves, it is not always applicable in the real atmosphere. Notwithstanding this limitation, with this method, convection and vertical shear have been identified as the possible sources of the observed medium and low-frequency GWs in the troposphere and lower stratosphere over many places (e.g., Venkat Ratnam et al, 2008). It becomes difficult to apply this method for GWs that are observed in the mesosphere and lower thermosphere (MLT) region, where simultaneous measurements of temperatures (with wind) would not be available.…”

Section: Introductionmentioning

confidence: 99%

“…Over the Indian region, several studies (Venkat Ratnam et al, 2008, and references therein) have been carried out for extracting GW parameters using various instruments (MST radar, radiosondes, lidar and satellite observations). In a few studies (Kumar, 2006(Kumar, , 2007Dhaka et al, 2002;Venkat Ratnam et al, 2008;Debashis Nath et al, 2009;Dutta et al, 2009;Leena et al, 2012a, b), possible sources in the troposphere for their generation are identified which include convection, wind shear and topography.…”

Section: Introductionmentioning

confidence: 99%

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

et al. 2015

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Abstract. Sources and propagation characteristics of highfrequency gravity waves observed in the mesosphere using airglow emissions from Gadanki (13.5 • N, 79.2 • E) and Hyderabad (17.5 • N, 78.5 • E) are investigated using reverse ray tracing. Wave amplitudes are also traced back, including both radiative and diffusive damping. The ray tracing is performed using background temperature and wind data obtained from the MSISE-90 and HWM-07 models, respectively. For the Gadanki region, the suitability of these models is tested. Further, a climatological model of the background atmosphere for the Gadanki region has been developed using nearly 30 years of observations available from a variety of groundbased (MST radar, radiosondes, MF radar) and rocket-and satellite-borne measurements. ERA-Interim products are utilized for constructing background parameters corresponding to the meteorological conditions of the observations. With the reverse ray-tracing method, the source locations for nine wave events could be identified to be in the upper troposphere, whereas for five other events the waves terminated in the mesosphere itself. Uncertainty in locating the terminal points of wave events in the horizontal direction is estimated to be within 50-100 km and 150-300 km for Gadanki and Hyderabad wave events, respectively. This uncertainty arises mainly due to non-consideration of the day-to-day variability in the tidal amplitudes. Prevailing conditions at the terminal points for each of the 14 events are provided. As no convection in and around the terminal points is noticed, convection is unlikely to be the source. Interestingly, large (∼ 9 m s −1 km −1 ) vertical shears in the horizontal wind are noticed near the ray terminal points (at 10-12 km altitude) and are thus identified to be the source for generating the observed highphase-speed, high-frequency gravity waves.

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MST radar and radiosonde observations of inertia‐gravity wave climatology over tropical stations: Source mechanisms

Cited by 50 publications

References 33 publications

Assessment of GPS radiosonde descent data

Assessment of GPS radiosonde descent data

Cloud vertical structure over a tropical station obtained using long-term high-resolution radiosonde measurements

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

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