CLIMATOLOGY AND INTERANNUAL VARIABILITY OF INTERTROPICAL CONVERGENCE ZONE IN THE EASTERN PACIFIC

Abstract

Characteristics of the Intertropical Convergence Zone (ITCZ) in the eastern Pacific are derived from the monthly mean wind convergence of ERS-QuikSCAT fields for 1991-2004. Its climatology is computed over 1999-2004, and compared with those derived from monthly sea surface temperature, atmospheric water vapor, cloud liquid water, and rain rate from the Tropical Rain Measuring Mission (TRMM, 1999-2004). Preliminary results indicated an excellent relationship between wind convergence and TRMM data for the northern branch of ITCZ (NITCZ). However, none of the TRMM fields show, as the ERS-QuikSCAT fields does the southern branch of ITCZ (SITCZ). Therefore, an especial emphasis is given over SITCZ, for instance only shown in wind convergence, with a permanent characteristic, although with a wide and narrow cover during February-March and October-November, respectively. TRMM data only shows the SITCZ during February to April. We extend the analysis to interannual time scales, with a particular emphasis on El Nino-Southern Oscillation cycle. The analysis of the ERS-QuikSCAT fields shows that during El Nino events both NITCZ and SITCZ are united in the first months and SITCZ disappear in the rest, whereas during la Nina, the SITCZ tends to strength and permanence throughout the year