Properties of inertia-gravity waves in the lowermost stratosphere as observed by the PANSY radar over Syowa Station in the Antarctic

Abstract

Abstract. Inertia-gravity waves (IGWs) are an important component for the dynamics of the middle atmosphere. However, observational studies needed to constrain their forcing are still insufficient especially in the remote areas of the Antarctic region. One year of observational data (January to December 2013) by the PANSY radar of the wind components (vertical resolution of 150 m and temporal resolution of 30 min) are used to derive statistical analysis of the properties of IGWs with short vertical wavelengths ( ≤ 4 km) and ground-based periods longer than 4 h in the lowermost stratosphere (height range 10 to 12 km) with the help of the hodograph method. The annual change of the IGWs parameters are inspected but no pronounced year cycle is found. The year is divided into two seasons (summer and winter) based on the most prominent difference in the ratio of Coriolis parameter (f ) to intrinsic frequency (ω) distribution. Average of f/ω for the winter season is 0.40 and for the summer season 0.45 and the average horizontal wavelengths are 140 and 160 km respectively. Vertical wavelengths have an average of 1.85 km through the year. For both seasons the properties of IGWs with upward and downward propagation of the energy are also derived and compared. The percentage of downward propagating waves is 10.7 and 18.4 % in the summer and winter season respectively. This seasonal change is more than the one previously reported in the studies from mid-latitudes and model-based studies. It is in agreement with the findings of past radiosonde data-based studies from the Antarctic region. In addition, using the so-called dualbeam technique, vertical momentum flux and the variance of the horizontal perturbation velocities of IGWs are examined. Tropospheric disturbances of synoptic-scale are suggested as a source of episodes of IGWs with large variance of horizontal perturbation velocities, and this is shown in a number of cases.

Rayleigh/Raman lidar observations of gravity wave activity from 15 to 70 km altitude over Syowa (69°S, 40°E), the Antarctic

“…GW observations have been performed in the lower, middle, and upper atmospheres of the Antarctic by satellites [ Baumgaertner and McDonald , ; Alexander et al ., ; Liu et al ., ], in situ (i.e., radiosondes [ Allen and Vincent , ; Yoshiki and Sato , ]), and by ground‐based instruments (i.e., lidars [ Yamashita et al ., ; Alexander et al ., ; Chen et al ., ; Kaifler et al ., ; Lu et al ., ; Chen et al ., ; Zhao et al ., ] and radars [ Dowdy et al ., ; Shibuya et al ., ; Mihalikova et al ., ]). However, most of these observations have a limited range of observable height.…”

Quasi-12 h inertia–gravity waves in the lower mesosphere observed by the PANSY radar at Syowa Station (39.6° E, 69.0° S)

“…A plausible generation mechanism of inertia-gravity waves in the upper stratosphere is spontaneous radiation from the polar night jet (e.g., Sato and Yoshiki, 2008). It is also worth noting that observational studies show high percentages of downward gravity wave propagation in the polar stratosphere compared to those found at low and middle latitudes (e.g., Yoshiki and Sato, 2000;Guest et al, 2000;Moffat-Griffin et al, 2013;Murphy et al, 2014;Mihalikova et al, 2016). To confirm this possibility, we examined fluctuation characteristics and background zonal winds of the upper stratosphere.…”

A Statistical Study of Inertia Gravity Waves in the Lower Stratosphere Over the Arctic Region Based on Radiosonde Observations

“…Based on profiles of wind and temperature from radiosonde and radar observations, hodograph method derived from the IGW polarization equation is extensively applied to analyze IGW propagation (Huang et al, ; Nath et al, ; Mihalikova et al, ; Moffat‐Griffin et al, , ; Ratnam et al, ; Vincent & Alexander, ; Wang et al, ; Zhang & Yi, , ). In particular, when a large‐amplitude IGW propagates in a background field with weak shear and slow temporal variation, hodograph method is regarded as an accurate technique.…”

“…For example, sheared wind field causes not only energy exchange between GWs and the background flow by means of the work due to Reynolds stress but also GW filtering or reflection phenomenon due to the Doppler effect (Hines, ; Huang et al, , ; Walterscheid, ). In the past several decades, a large number of studies revealed the geographical and seasonal variability of GW source, propagation, structure, and spectrum based on radiosonde (Nath et al, , ; Pfenninger et al, ; Vincent & Alexander, ; Wang et al, ; Yoshiki & Sato, ; Zhang & Yi, , ; Zhang et al, ), radar (Mihalikova et al, ; Nastrom & Eaton, ; Ratnam et al, ; Riggin et al, , ; Sato et al, ), lidar (Alexander et al, ; Hu et al, ; Huang et al, ; B. Kaifler et al, ; T. Li et al, ; Lu et al, ; Wilson et al, ; Xu et al, ; Yuan et al, ), airglow imager (Hickey et al, ; Hickey et al, ; Z . Li et al, ; Nielsen et al, ; Snively et al, ; Swenson & Mende, ; Yue et al, , ), rocketsonde (Eckermann et al, ; Hamilton, ), and satellite (Alexander et al, ; Alexander & Rosenlof, ; Ern et al, ; Wright et al, ; Wu & Waters, ; Yamashita et al, ) measurements.…”

“…For example, sheared wind field causes not only energy exchange between GWs and the background flow by means of the work due to Reynolds stress but also GW filtering or reflection phenomenon due to the Doppler effect (Hines, 1991;Huang et al, 2008Huang et al, , 2010Walterscheid, 2000). In the past several decades, a large number of studies revealed the geographical and seasonal variability of GW source, propagation, structure, and spectrum based on radiosonde (Nath et al, 2009(Nath et al, , 2010Pfenninger et al, 1999;Vincent & Alexander, 2000;Wang et al, 2005;Yoshiki & Sato, 2000;Zhang & Yi, 2005Zhang et al, 2012), radar (Mihalikova et al, 2016;Nastrom & Eaton, 2006;Ratnam et al, 2008;B. Kaifler et al, 2015;T.…”