Characteristics of the multiple tropopauses in the tropics

In a previous work (Mehta et al., 2011. J. Geophys. Res. 116, D20105, doi:10.1029/2011JD016637), we emphasized the limitations of the WMO definition of multiple tropopauses (MTs) which was based on the lapse rate in identifying them sometimes, and provided an alternate method called cold point method, to delineate the MTs over the tropics effectively. In the present work we described the detailed characteristics of the MTs over the tropics identified using the cold point method. We have used COSMIC GPS RO data obtained during August 2006–August 2008 and radiosonde data from 5 stations during 1999–2008 in the ±15° latitude for the present study. There is a marked latitudinal variation within the tropics in the MTs and cold point tropopause (CPT) in different seasons. These MTs can occur both above and below the CPT. The saturation water vapor mixing ratio corresponding to the lower tropopause (MTs which occur below CPT) from November to May is in general ∼3ppmv indicating dry conditions even below the CPT altitude. The latitudinal variation of altitudes of the MTs and CPT showed quite different features. We also examined the role of equatorial waves in the occurrence of MTs. This wave mechanism could explain the MT occurrences that are in groups but not in the individual cases suggesting other mechanisms could also exist. ► Characteristics of the MTs over tropics and causative mechanisms presented. ► There is a marked latitudinal variation in MTs and CPT in different seasons. ► The SWVMR at LT is ∼3ppmv indicating dry conditions below the CPT. ► Wave mechanism could explain MTs that occur only in groups.