Diurnal variation of ducts observed over a tropical station, Gadanki, using high‐resolution GPS radiosonde observations

Abstract

A comprehensive study on diurnal variation of ducting using high vertical and temporal resolution radiosonde measurements over the Indian tropical region, Gadanki (13.5°N, 79.2°E), was presented. The diurnal variation of ducts was examined statistically based on both the refractivity and modified refractivity using 3-hourly radiosonde soundings obtained during October 2010 to March 2014 as a part of tropical tropopause dynamics (TTD) campaigns conducted under Climate and Weather of Sun Earth System (CAWSES) India Phase II program. Strong diurnal variation in the altitude of occurrence of the duct has been found and is at maximum altitude (~2.5 km) during 11-17 LT. Interestingly, it is found that the occurrence of duct altitude closely follows the boundary layer altitude. Diurnal variation of duct altitude is maximum during postmonsoon followed by winter, monsoon, and minimum in premonsoon. However, duct strength is maximum during winter followed by premonsoon, postmonsoon, and minimum in monsoon. Duct thickness is found to be varying between 0.4 km and 1 km diurnally with the highest thickness during the winter season. Strong diurnal and seasonal variation in the percentage occurrence of the ducts was found with the highest percentage of ducts observed during winter (77%) followed by postmonsoon (51%), premonsoon (44%), and monsoon (10%). All the characteristics of ducts during all the seasons are maximum at 14 LT due to the high solar irradiance over Gadanki from 11 to 17 LT. The minimum frequency being trapped has been investigated and found that wave trapping occurs for the radars with frequencies 56-438 MHz over this station.

Improved boundary layer height measurement using a fuzzy logic method: Diurnal and seasonal variabilities of the convective boundary layer over a tropical station

“…Due to the complex terrain surrounding the radar site, the LLJs are strong during night hours generating strong wind shears and associated strong turbulence. This type of deep nocturnal boundary layer (boundary layer from sunset to sunrise referred to as NBL) has also been observed by Basha and Venkat Ratnam [2009] and Manjula et al [2016] over this region . Stull [1988] also reported that the NBL height is mostly dictated by the radiative cooling at the surface, by the strength of eventually present LLJs and associated turbulence, and residual layer.…”

The Statistical Characteristics of Atmospheric Ducts Observed Over Stations in Different Regions of American Mainland Based on High-Resolution GPS Radiosonde Soundings

“…The phenomenon is caused by the gradient in refractivity with regard to altitude. Many meteorological processes are associated with it, like temperature inversion, moisture inversion, the subsidence of air masses, and the passing of cold air over warm land (Manjula et al, 2016).…”

Analysis of the Atmospheric Duct Existence Factors in Tropical Cyclones Based on the SHAP Interpretation of Extreme Gradient Boosting Predictions

“…Therefore, the data from GPS dropsondes, aircraft and radiosondes were used in the literature. Manjula et al analyzed the diurnal variation of atmospheric ducts in different seasons and the ducts characteristics contrast between different seasons in Gadanki [10]. Zhao et al [11] used radiosonde data on the balloons by ship to detect the ducts occurrence in 2013, and they concluded that the probability of ducts in the South China Sea is about 75% during 2010-2012.…”