Abstract
Abstract. Vertical profiles of aerosol extinction coefficients were measured by a micro-pulse lidar at Naqu (31.5° N, 92.1° E; 4508 m a.m.s.l.), a meteorological station located on the central part of the Tibetan Plateau during summer 2011. Observations show a persistent maximum in aerosol extinction coefficients in the upper troposphere–lower stratosphere (UTLS). These aerosol layers were generally located at an altitude of 18–19 km a.m.s.l., 1–2 km higher than the tropopause, with broad layer depth ranging approximately 3–4 km and scattering ratio of 4–9. Daily averaged aerosol optical depths (AODs) of the enhanced aerosol layers in UTLS over the Tibetan Plateau varied from 0.007 to 0.030, in agreement with globally averaged levels of 0.018 ± 0.009 at 532 nm from previous observations, but the percentage contributions of the enhanced aerosol layers to the total AOD over the Tibetan Plateau are higher than those observed elsewhere. The aerosol layers in UTLS wore off gradually with the reducing intensity of the Asian monsoon over the Tibetan Plateau at the end of August. The eruption of Nabro volcano on 13 June 2011 is considered an important factor to explain the enhancement of tropopause aerosols observed this summer over the Tibetan Plateau.
Highlights
Aerosols in the upper troposphere–lower stratosphere (UTLS) play an important role in the global/regional climate system and the geochemical cycle (Hanson et al, 1994; Borrmann et al, 1997; Solomon et al, 1997)
We find a persistent maximum in aerosol extinction coefficients in the UTLS within the anticyclone, and show that such aerosol accumulation can be linked to the eruption of Nabro volcano
At nighttime (21:00–07:00 LST), aerosol enhancements were detected at relative constant altitudes from 17.0 to 18.5 km (a.m.s.l.) due to the higher signal to noise ratios (SNRs) of lidar compared with the daytime
Summary
Aerosols in the upper troposphere–lower stratosphere (UTLS) play an important role in the global/regional climate system and the geochemical cycle (Hanson et al, 1994; Borrmann et al, 1997; Solomon et al, 1997). Appearance of cold tropopause in the upper troposphere (possibly in the lower stratosphere ) has been considered an important factor to explain the enhancement of tropopause aerosols observed in summer over the plateau (Kim et al, 2003) This observational fact is important from the point view of heterogeneous reactions on aerosol surfaces since gas-to-particle conversion processes are generally more active in low temperatures. We find a persistent maximum in aerosol extinction coefficients in the UTLS within the anticyclone, and show that such aerosol accumulation can be linked to the eruption of Nabro volcano
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
