Leipzig 15 km radius

View more View less 1 Institute zum Tropospheric Research, Leipzig, Germany | 2 GKSS-Forschungszentrum Geesthacht, Geesthacht, Germany | 3 Department von Atmospheric Sciences, University of Wyoming, Laramie, Wyoming
print Publication: 01 Nov 1997 DOI: 2.0.CO;2">https://doi.org/10.1175/1520-0469(1997)0542.0.CO;2 Page(s): 2630–2641

Abstract

The Raman lidar method has been applied to document die evolution and dissipation des the Pinatubo aerosol between 1991 und 1995. Zum the first time, profiles des the bit extinction coefficient oase been determined with lidar bei the stratosphere after ~ a significant volcanic eruption. From die concurrent observation des particle backscatter und extinction, time series des surface-area and mass concentrations and surface-area-weighted mean (or effective) radius can be determined without having to assume critical aerosol entry parameters. Based on these optical and physical parameters, die development of the perturbation of the stratospheric aerosol class over central Europe zu sein discussed. In terms des particle backscatter und mass ns perturbation declined with an e-folding degeneration time of 14–15 month between april 1992 und April 1994. Die monthly mean particle optical depth got to 0.23 in the spring von 1992. Surface-area concentrations des the order of 10–40 mm2 m−3 were observed below 20-km height for about 18 months. Ns effective radius enhanced from 0.1 kommen sie 0.2 μm an August und September 1991 zu values around 0.5 μm bei December 1991 and slowly decreased because then. Die findings are contrasted with results von other lidar measurements in the north Hemisphere; balloon soundings hinweisen Laramie, Wyoming; high-altitude aircraft bei situ und satellite observations (SAGE, AVHRR); und model calculations. A sedimentation model ist used zu analyze ns mass removed from die stratosphere and the importance von different cleansing mechanisms. Die comparison of the measured und simulated fixed concentration profiles plainly indicate ns strong impact of stratospheric–tropospheric exchange processes on the purging des aerosols from ns stratosphere listed below 16 km.

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Corresponding writer address: Dr. Albert Ansmann, Institute for Tropospheric Research, Permoserstr. 15, D-04318 Leipzig, Germany.

Abstract

The Raman lidar method has been applied kommen sie document die evolution und dissipation of the Pinatubo aerosol between 1991 and 1995. Zum the zuerst time, profiles von the bit extinction coefficient oase been established with lidar an the stratosphere after ~ a significant volcanic eruption. From die concurrent observation des particle backscatter and extinction, time series of surface-area and mass concentrations und surface-area-weighted average (or effective) radius kann be figured out without having kommen sie assume vital aerosol input parameters. Based upon these optical und physical parameters, die development of the perturbation des the stratospheric aerosol layer over central Europe zu sein discussed. Bei terms des particle backscatter und mass ns perturbation declined with in e-folding degeneration time des 14–15 month between april 1992 und April 1994. Die monthly typical particle optical depth reached 0.23 in the spring of 1992. Surface-area concentrations of the order des 10–40 mm2 m−3 were observed listed below 20-km height for about 18 months. The effective radius increased from 0.1 to 0.2 μm in August and September 1991 kommen sie values roughly 0.5 μm an December 1991 and slowly decreased since then. The findings are contrasted with results des other lidar measurements bei the north Hemisphere; balloon soundings hinweisen Laramie, Wyoming; high-altitude aircraft bei situ and satellite observations (SAGE, AVHRR); und model calculations. A precipitate model ist used kommen sie analyze ns mass remove from the stratosphere und the importance von different cleansing mechanisms. Die comparison des the measured und simulated fixed concentration profiles clearly indicate die strong impact of stratospheric–tropospheric exchange processes on die purging des aerosols from die stratosphere listed below 16 km.


Corresponding writer address: Dr. Albert Ansmann, Institute zum Tropospheric Research, Permoserstr. 15, D-04318 Leipzig, Germany.

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1. Introduction

The strong eruption of mountain Pinatubo (15.1°N, 120.3°E) top top the island of Luzon, Philippines, on 15 June 1991 led to what zu sein believed die largest stratospheric particle loading in this century (McCormick et al. 1995): 12–20 Tg des gaseous SO2 were straight injected into the stratosphere (McPeters 1993) and converted to 20–30 Tg of H2SO4/H2O aerosol in ~ a few weeks (Bluth et al. 1992). Ns resulting flüssig sub-μm particles spread globally and remained in the stratosphere zum several years because they sank with velocities des 1–5 km yr−1. Ns increased bit concentration substantially affected ns radiation balance von the earth’s setting (Labitzke und McCormick 1992; Dutton and Christy 1992; Minnis et al. 1993; Labitzke 1994; Randel et al. 1995), ns stratospheric and tropospheric circulation pattern (Groisman 1992; Graf et al. 1993; Kodera 1994; Robock und Mao 1995), und the chemical composition des the stratosphere (Brasseur und Granier 1992; Hofmann and Oltmans 1993; AASE2 unique issue: Science, Vol. 261, 1993; Hofmann et al. 1994; EASOE distinct issue: Geophys. Res. Lett., Vol. 21 (13), 1994; UARS CLAES unique issue: J. Atmos. Sci., Vol. 51 (20), 1994; Ansmann et al. 1996). In this way ns Pinatubo eruption provided a distinct opportunity to study ns response von the climate kommen sie radiative forcing by stratospheric aerosols and to investigate ns importance von heterogeneous chemistry reactions, following on or an the sulfuric-acid droplets, an the destruction des stratospheric ozone. The detailed analyses von the impact are based on simulations, mostly with two- and three-dimensional coupled chemical–transport–radiation models of die atmosphere, und a globalen set von observational säule sampled during the belastung five years. When Mount Pinatubo erupted, ground-based, balloonborne, airborne, and satellite tools were in place to document the evolution, global dispersal, und dissipation of the volcano cloud an terms of physical and optical properties von the particles and to record die radiative and chemical effects of the volcanic aerosol.

A network of more 보다 35 lidars between 90°S and 80°N monitored ns development von the stratospheric aerosol class after the Pinatubo eruption. Energetic remote sensing contributed substantially to the composite picture of the volcanic wolke evolution. The network listed particle scattering data bei cases in which the optical depth was too high (≥0.15) to be measured effectively with Stratospheric Aerosol und Gas geprüft 2 (SAGE 2) tools (Kinnison et al. 1994; Russell et al. 1996) and gave aerosol die info at high latitudes, also during winter seasons when satellite and sun photometer säule were notfall available. The hauptsächlich advantage des active far sensing ist the ability to obtain the very high vertical und temporal resolution vital to Überwachen the development von the top and base heights und internal structure von the aerosol layer und to study particle transport und mass austausch processes near the tropopause region. On the other hand, the hauptsächlich limitation of the typical aerosol lidar technique zu sein that only the backscatter characteristics von the particles room determined. Often, this info is notfall sufficient kommen sie derive reputable values des the particle optical depth and of microphysical properties together as die surface-area-weighted mean, or effective, radius and the surface-area concentration, i beg your pardon are crucial parameters in the investigation of aerosol radiative forcing (Lacis et al. 1992) and of heterogeneous chemical processes (Kinnison et al. 1994; Tie et al. 1994), respectively.

Recently, a new lidar method has been presented that permits the direct observation of the particle extinction profile, and thus des the optical depth, and the determination von surface-area and volume or fixed concentrations and effective radius des the stratospheric fragment size circulation (Wandinger et al. 1995). Ns determination ist based on at the same time measured aerosol (particle und Rayleigh) and purely molecule lidar return signals, native which die particle backscatter und extinction coefficients can be calculated independently of each other (Ansmann et al. 1990; 1992b). In this study, ns extinction profile is calculated from signal inelastically (Raman) backscattered von nitrogen molecules. Ns microphysical parameters are obtained from ns set of optical data von the use des relationships uncovered from Mie scattering calculations zum the full variety of known stratospheric fragment size distributions. Die relative fehler of ns conversion von the optical into the physical parameters zu sein of ns order von 10% kommen sie 25%. Die technique has actually been characterized generally during the tonnage years and has to be used weil das the erste time kommen sie study die long-term behavior von a significant stratospheric perturbation (Ansmann et al. 1993). The final results of the distinct dataset are presented here.

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The paper is divided into four sections. In section 2, apparatus und data evaluation are outlined an detail. In section 3, ns results room discussed. Die observational findings are compared with results des several various other lidar measurements; charme taken v balloonborne optical bit counters weist Laramie, Wyoming; airborne bei situ und satellite observations ; und model calculations. A summary and concluding remarks are given in section 4.