From Mauna Loa, Hawaii, lidar data on 2 December showed a sharp decline in aerosols between 21 and 25 km altitudes (figure 35), the zone where increased concentrations were observed in November. Data later in December showed aerosols returning to that altitude range.

Figure 35. Lidar data from Hawaii and Virginia, showing altitudes of aerosol layers. Note that some layers have multiple peaks. Backscattering ratios are for the ruby wavelength of 0.69 µm. Integrated values show total backscatter, expressed in steradians-1, integrated over 300-m intervals from 16-33 km at Mauna Loa and from the tropopause to 30 km at Hampton. Because of probable cirrus layers at 14-17 km on 30 December at Mauna Loa and 11.1-12.8 km on 22 December at Hampton, data are integrated from 17.1 and 13 km, respectively. If different, altitudes of maximum backscattering ratios and coefficients are shown for each layer at Mauna Loa.

On 30 December, NE-SW bands of clouds about 500 km long and 250 km apart were seen in the vicinity of Hawaii on infrared weather satellite imagery. Cloud altitudes could not be determined from the satellite data. They looked like gravity waves in cirrus, and may have caused the very sharp peak detected by lidar that night between 14 and 17 km (tropopause altitude was 16.5 km). Lidar profiles from Hampton, VA in late December and early January were similar to the 4 December data, unlike the complex layers observed in November.

Information Contacts: Thomas DeFoor, Mauna Loa Observatory, P.O. Box 275, Hilo, HI 96720 USA; William Fuller, NASA Langley Research Center, Hampton, VA 23665 USA.