Quasi-two-day wave in the lower atmosphere over Hyderabad during summer of 2009

Abstract

Abstract. The characteristics of the quasi-2-day wave (QTDW) in the lower atmosphere (1–50 km) has been investigated using wind and temperature data obtained from India Meteorological Department (IMD), Hyderabad (17.4° N, 78.5° E) and ECMWF Re-Analysis (ERA-interim) data for (18° N, 78° E) which is the nearest grid to the location of observation. Wind and temperature data of IMD between 15 May and 24 September 2009 in the altitude range of 1–25 km have been used for the present study. Simultaneous ERA data of wind and temperature for the same period between the pressure levels of 1–1000 mb have been analyzed for 2-day wave activity. Appreciable amplitudes of the wave (~2–3 m s−1) could be observed in both IMD and ERA datasets of winds. The thermal amplitude maximum is ~1.5 K in the lower stratosphere (IMD). Amplitudes obtained from ERA data are found to be less than those obtained from IMD measurements. Maximum wind amplitudes (1.5–2 m s−1) are observed in the UTLS region and in the upper stratosphere between 35–45 km. Peak value of temperature oscillation in the upper stratosphere is ~1 K. Wavelet analyses show systematic bursts of QTDW during the summer solstice with a gap of ~5–8 days. The striking similarity between the results of IMD and ERA data can be appreciated. The squared-coherence values between the two datasets in terms of cross-spectral amplitudes are found to be highly significant for 2-day wave in the lower atmosphere.