MAUNA LOA

Trends

The NOAA/CMDL observatory at Mauna Loa, Hawaii, U.S.A., has obtained a nearly continuous AOD anomaly record, with values missing for only 8 months (the most recent in 1982) during 1977-92. The predominant features are the large increases in AOD that followed the volcanic eruptions of El Chichón (Mexico, 1982) and Pinatubo (Philippines, 1991). The maximum AOD anomaly following the El Chichón eruption (0.20 in July 1982) was the highest recorded for this event at any of the four NOAA/CMDL sites and is essentially equal to the maximum recorded at this site (0.19 in August 1991) following the eruption of Pinatubo. However, the decay to background values appeared to be much slower after the Pinatubo event; AOD anomalies 1 year after Pinatubo were about twice those 1 year after El Chichón. The AOD anomaly record at Mauna Loa also shows an annual cycle, with a maximum usually in May. This cycle appears to be largely the result of the seasonal arrival of Asian desert dust, which is carried over Mauna Loa by westerly winds prevailing in the region during spring.

After the annual cycle and the volcanic events are removed from the AOD anomaly record, no evidence of any long-term trend remains.

Mauna Loa
Hawaii, U.S.A.
Barren volcanic mountain slope
19° 32' N, 155° 35' W
3397 m above MSL

Mauna Loa Optical Depth Graph

• Monthly aerosol optical depth anomalies at Mauna Loa