Identification and separation of Mount Pinatubo and El Nino-Southern Oscillation land surface temperature anomalies

Empirical data analyses are performed to detect and separate the signals of the volcanic eruption and El Nino events in the observed surface air tempe rature (SAT) anomalies over land for the 2 years following the Pinatubo eru ption. Composite analyses of surface temperatures for the 1950-1997 period, excluding the 2 years following each of the three major volcanic eruptions , Agung, El Chichon, and Pinatubo, show that the distribution of SAT anomal ies over most land areas for the El Nino composite is opposite to that for the La Nina composite. The pattern of SAT anomalies changes from season to season. This feature is more prominent over North America than over the oth er continents. Singular value decomposition analyses show that following th e Pinatubo eruption, El Nino signals were weak over Eurasia but relatively strong over the other continents. Over North America, the 1991-1992 El Nino event contributed more than 50% to the observed surface cooling of about - 1.0 degreesC in June, July, and August 1992. Globally averaged, the maximum cooling over land with the El Nino-Southern Oscillation signals removed is -0.5 degreesC in September, October, and November 1992 and September, Octo ber, and November 1993.