Four‐decadal climatological intercomparison of rocketsonde and radiosonde with different reanalysis data: results from Thumba Equatorial Station

Abstract

Four decades of climatological data on winds from 0 to 65 km measured over the Thumba Equatorial Rocket Launching Station (TERLS) (8.53°N, 76.87°E), a low‐latitude equatorial station in India, are compared with four global reanalysis datasets. The observations are made using balloon‐borne experiments (0–35 km) and rocket soundings (20–65 km) from 1970 to 2013. Reanalysis data compared well with the real‐time observations below the tropopause and less well above it in both the wind components (zonal and meridional). The average correlation coefficient between observations and reanalysis is found to be 0.9 for zonal wind from the surface to 30 km and 0.6 for meridional wind from the surface to 15 km. The amplitude of the semi‐annual oscillation (SAO), annual oscillation (AO), and Quasi‐Biennial Oscillation (QBO) are reproduced well in the four reanalysis datasets. The QBO amplitude maximum around 20–30 km altitude is systematically underestimated by all the reanalyses compared to the observations.

Assessment of vertical air motion among reanalyses and qualitative comparison with very-high-frequency radar measurements over two tropical stations

“…Advances have also been made with respect to soil hydrology and snow in land surface models. The detail of the model is given in Dee et al (2011). We use 6-hourly vertical velocities from the ERAi from 1995 to 2015.…”

“…This estimation gives a general view of the distribution of ascending and descending motion on the synoptic scale within the quasi-geostrophic framework (Tanaka and Yatagai, 2000; Jagannadha Rao et al, 2003). Reanalyses evaluate the vertical pressure velocity (omega) using indirect estimation (e.g., Dee et al, 2011). Any reanalysis products assimilate as much as 107 observations per day, which is inclusive of both conventional (radiosonde, tower, aircrafts, wind profilers (wherever possible), etc.)…”

“…However, reanalyses combine both observations and model outputs to produce systematic variation in the atmospheric state (e.g., Fujiwara et al, 2017). It is to be noted that the w provided by any reanalysis data center is estimated indirectly from the horizontal wind components and temperature, which itself has mismatch among various reanalysis data (e.g., Das et al, 2016;Kawatani et al, 2016). Thus, this can possibly induce the discrepancy in the estimated w among various reanalyses.…”

The Role of the Phase of QBO in Modulating the Influence of the SSW Effect on the Equatorial Ionosphere

“…The choice of the pressure level is not only based on the previous studies across the globe but also on the QBO observations over the present study location, Trivandrum. In a recent study dealing with the intercomparison of Rocketsonde and Radiosonde with different reanalysis data over Trivandrum, Das et al (2015) have shown that the QBO amplitude show peak around ~30 km corresponding to 10-hPa level. The lower level, that is, 50 hPa (~19 km) is in the lower most altitude of the equatorial stratosphere, which is very near to the source region of the atmospheric waves.…”

Stratospheric intrusion into the troposphere during the tropical cyclone Nilam (2012)

“…The model resolution is 0.5° × 0.667°. The MERRA reanalysis is found to be comparable with the observations over the Indian tropical region (Das et al , ). These products are specifically designed to support chemistry and stratosphere transport modelling.…”