Observational evidence of the relationship between the tropical tropopause and tropical easterly jet streams over the Indian monsoon region

Abstract

This paper presents the first quantitative relationship between the cold point tropopause (CPT) and tropical easterly jet (TEJ) using radiosonde observations over Gadanki (13.45° N, 79.2° E) during the Indian summer monsoon season 2006–2014. CPT and TEJ peak altitudes ($H_{\mathrm{CPT}}\text{and}{H}_{\mathrm{TEJ}}$) show amalgams of two categories of variability on the day-to-day scale. In category1 $H_{\mathrm{TEJ}}$ occurs close to $H_{\mathrm{CPT}}$ and they show in-phase variation. While in Category2 $H_{\mathrm{TEJ}}$ occurs far apart from $H_{\mathrm{CPT}}$ and they do not show any relationship. For Category1 $H_{\mathrm{CPT}}$ and $H_{\mathrm{TEJ}}$ are strongly correlated (0.70), as well as $H_{\mathrm{CPT}}$ and $T_{\mathrm{CPT}}$ (CPT temperature) are moderately anticorrelated (−0.55) significant at a 95% confidence level, indicating the dominance of adiabatic processes. Whereas in Category2 $H_{\mathrm{CPT}}$ and $T_{\mathrm{CPT}}$ are not significantly anti-correlated. Thus, when TEJ and CPT are close to each other, it may serve as an indicator for the prevalence of the synoptic-scale effect.