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NASA NTRS1992

Lidar Observations of the Pinatubo Stratospheric Aerosol Cloud over Frascati, Italy

The Pinatubo eruption of June 1991 introduced large plumes into the local stratosphere. On several occasions, volcanic gases and particles reached altitudes of about 30 km, and spread towards the west. A lidar system has been operating to monitor the evolution of the stratospheric aerosol cloud. The backscattering ratio profiles of eight different measurements were chosen to summarize the most significant occurrences of the event. Since the beginning of the winter planetary wave activity, the Pinatubo cloud integrated backscatter exceeded El Chichon's. In this context, the perturbation generated by El Chichon can only be assumed as a lower limit of the one which will follow the Pinatubo eruption. Observations of the event are still in progress.

Congeduti, Fernando↗
NASA NTRS1995

Evolution of the Pinatubo volcanic aerosol column above Pasadena, California observed with a mid-infrared backscatter lidar

The evolution of the volcanic debris plume originating from the June 1991 eruption of Mt. Pinatubo has been monitored since its genesis using a ground-based backscatter lidar facility sited at the Jet Propulsion Laboratory (JPL). Both absolute and relative pre- and post-Pinatubo backscatter observations are in accord with Mie scattering projections based on measured aerosol particle size distributions reported in the literature. The post-Pinatubo column-integrated backscatter coefficient peaked approximately 400 days after the eruption, and the observed upper boundary of the aerosol column subsided at a rate of approximately 200 m/mon.

Tratt, David M.↗
NASA NTRS1994

The post-pinatubo evolution of stratospheric aerosol surface area density as inferred from SAGE 2

Following the eruption of Mount Pinatubo in June of 1991, the aerosol mass loading of the stratosphere increased from -1 Mt to approximately 30 Mt. This change in aerosol loading was responsible for numerous radiative and chemical changes observed within the stratosphere. As a result, the ability to quantify aerosol properties on a global basis during this period is important. Aerosol surface area density is a critical parameter in governing the rates of heterogeneous reactions, such as ClONO2 plus H2O yields HNO3 plus HOCl, which influence the stratospheric abundance of ozone. Following the eruption of Mt. Pinatubo, measurements by the Stratospheric Aerosol and Gas Experiment (SAGE 2) indicated that the stratospheric aerosol surface area density increased by as much as a factor of 100. Using SAGE 2 multi-wavelength aerosol extinction data, aerosol surface area density as well as mass are derived for the period following the eruption of Mt. Pinatubo through the present.

Poole, L. R.↗
NASA NTRS1995

Comparing Simultaneous Stratospheric Aerosol and Ozone Lidar Measurements with SAGE 2 Data after the Mount Pinatubo Eruption

Stratospheric aerosol and ozone profiles obtained simultaneously from the lidar station at the University of L'Aquila (42.35 deg N, 13.33 deg E, 683 m above sea level) during the first 6 months following the eruption of Mount Pinatubo are compared with corresponding nearby Stratospheric Aerosol and Gas Experiment (SAGE) 2 profiles. The agreement between the two data sets is found to be reasonably good. The temporal change of aerosol profiles obtained by both techniques showed the intrusion and growth of Pinatubo aerosols. In addition, ozone concentration profiles derived from an empirical time-series model based on SAGE 2 ozone data obtained before the Pinatubo eruption are compared with measured profiles. Good agreement is shown in the 1991 profiles, but ozone concentrations measured in January 1992 were reduced relative to time-series model estimates. Possible reasons for the differences between measured and model-based ozone profiles are discussed.

Yue, G. K.↗
NASA NTRS1993

The Atmospheric Impact of the 1991 Mount Pinatubo Eruption

The 1991 eruption of Pinatubo produced about 5 cubic kilometers of dacitic magma and may be the second largest volcanic eruption of the century. Eruption columns reached 40 kilometers in altitude and emplaced a giant umbrella cloud in the middle to lower stratosphere that injected about 17 megatons of SO2, slightly more than twice the largest yielded by the 1982 eruption of El Chichon, Mexico. The SO2 formed sulfate aerosols that produced the largest perturbation to the stratospheric aerosol layer since the eruption of Krakatau in 1883. The aerosol cloud spread rapidly around the Earth in about 3 weeks and attained global coverage by about 1 year after the eruption. Peak local midvisible optical depths of up to 0.4 were measured in late 1992, and globally averaged values were about 0.1 to 0.15 for 2 years. The large aerosol cloud caused dramatic decreases in the amount of net radiation reaching the Earth's surface, producing a climate forcing that was two times stronger than the aerosols of El Chichon. Effects on climate were an observed surface cooling in the northern hemisphere of up to 0.5 to 0.6 C, equivalent to a hemispheric-wide reduction in net radiation of 4 watts per square meter and a cooling of perhaps as large as -0.4 C over large parts of the earth in 1992-93. Climate models seem to have predicted the cooling with a reasonable degree of accuracy. The Pinatubo climate forcing was stronger than the opposite warming of either the El Nino event or anthropogenic greenhouse gases in the period 1991-93. As a result of the presence of the aerosol particles, midlatitude ozone concentrations reached their lowest levels on record during 1992-93, the southern hemisphere 'ozone hole' increased in 1992 to an unprecedented size and ozone depletion rates were observed to be faster than ever before recorded. The atmospheric impact of the Pinatubo eruption has been profound, and it has sparked a lively interest in the role that volcanic aerosols play in climate change. This event has shown that a powerful eruption providing a 15 to 20 megaton release of SO2 into the stratosphere can produce sufficient aerosols to offset the present global warming trends and severely impact the ozone budget.

Self, Stephen↗
NASA NTRS1994

Comparison of the Dispersion of the Mt. Pinatubo and El Chichon Stratospheric Aerosol Clouds

Insights into stratospheric transport and the climatic effects of large volcanic eruptions can be obtained by studying the dispersion of two of the largest volcanic eruptions this century, Mt. Pinatubo and El Chichon. Although both eruptions were located between 15 and 20 N latitude, and occurred either in spring or early summer (April vs June), the two volcanic clouds evolved differently in terms of dispersion of the volcanic aerosols. The El Chichon cloud stayed essentially confined to between 30 N and the equator until fall season following the eruption, whereas the Mt. Pinatubo cloud spread more rapidly into the southern hemisphere. Three dimensional stratospheric interactive tracer simulations for the particular years of the eruptions are reported. Radiative heating of the volcanic clouds due to upwelling IR radiation from the troposphere is important for understanding the dispersion of the volcanic aerosols, especially for Mt. Pinatubo. However, radiative heating alone does not explain the qualitative difference in meridional dispersion of the two volcanic clouds. The rate at which the aerosol clouds are sheared apart by wind shear limits the effectiveness of the radiative heating in producing meridional dispersion, and the wind shear is a function of the particular year of each eruption.

Young, R. E.↗
NASA NTRS2001

Did the Eruption of the Mt. Pinatubo Volcano Affect Cirrus Properties?

Some observations suggest that the volcanic aerosols produced by the Mt. Pinatubo eruption may have altered cirrus properties. We look for evidence that such modification of cirrus is extensive enough to be climatically significant by comparing three satellite-based cirrus datasets produced by the ISCCP (International Satellite Cloud Climatology Project) analysis, the 'split-window' analysis, and 3I analysis. Since the former two have not been compared in detail before, we conduct such a comparison here. When applied to AVHRR (Advanced Very High Resolution Radiometer) data, both the ISCCP and split-window analyses identify about 0.2 - 0.3 cirrus cloud amount in tropical latitudes; however, there are detailed differences of classification for about half of these clouds. The discrepancies are attributed to the simplified assumptions made by both methods. The latter two datasets are derived from infrared radiances, so they are much less sensitive to volcanic aerosols than the ISCCP analysis. After the Mt. Pinatubo eruption, the ISCCP results indicate a dramatic decrease of thin cirrus (cloud top pressure less than 440 mb and visible optical thickness less than 1.3) over ocean, accompanied by a comparable increase of altocumulus and cumulus clouds; over land, there are no significant changes. In contrast, results from the split-window and 3I analyses show little change in thin cirrus amount over either ocean or land that is associated with the volcanic eruption. The ISCCP results can, therefore, be understood as a misclassification of thin cirrus because the additional reflected sunlight by the volcanic aerosol makes the cirrus clouds appear to be optically thicker. Examination of the split-window signature and the infrared emissivities from 3I show no significant change in infrared emissivity (or optical thickness). These results indicate that the Mt. Pinatubo volcanic aerosol did not have a significant systematic effect on tropical cirrus properties, but rather produced only temporary, local effects. Hence, these results indicate that there was no significant climate feedback produced by aerosol-cirrus-radiative interactions.

Luo, Zhengzhao↗
NASA NTRS2018

Mt. Pinatubo's Impacts on the GEOS Forecasting System

The eruption of Mount Pinatubo in June 1991 had dramatic effects on the global climate, introducing a sudden and extreme forcing on the radiative budget. In this presentation we analyze the effects of the Mt. Pinatubo eruption on the seasonal forecast performed with Goddard Earth Observing System (GEOS), an Earth System Model that includes a bulk aerosol model coupled to radiation and an interactive ocean.We performed three ten-member ensembles of 12-month simulations (June 1991-May 1992). These simulations were performed with a 0.5 longitude by 0.5 latitude horizontal resolution. Out of the three ensembles, one excludes the eruption, representing the control experiment. The other two ensembles include the eruption of Mt. Pinatubo, varying in the effective radius of the volcanic sulfate: one assumed the effective radius to be equal to 0.35 micron (as for tropospheric aerosol) and the other has the effective radius set to 0.6 micron (closer to natural observation). Through the analysis of the aerosol forcing results derived from the two assumptions, we can show how this forcing acts on the seasonal forecast system. In particular, we will focus on the impacts to the surface and ocean temperatures and precipitation.

Mukherjee, Nikita↗
DOE OSTI2024

Validating a microphysical prognostic stratospheric aerosol implementation in E3SMv2 using observations after the Mount Pinatubo eruption

Abstract. This paper describes the addition of a stratospheric prognostic aerosol (SPA) capability – developed with the goal of accurately simulating sulfate aerosol formation and evolution in the stratosphere – in the Department of Energy (DOE) Energy Exascale Earth System Model, version 2 (E3SMv2). The implementation includes changes to the four-mode Modal Aerosol Module microphysics in the stratosphere to allow for larger particle growth and more accurate stratospheric aerosol lifetime following the Pinatubo eruption. E3SMv2-SPA reasonably reproduces stratospheric aerosol lifetime, burden, aerosol optical depth, and top-of-atmosphere flux when compared to remote sensing observations. E3SMv2-SPA also has close agreement with the interactive chemistry–climate model CESM2-WACCM (Community Earth System Model version 2–Whole Atmosphere Community Climate Model) – which has a more complete chemical treatment – and the observationally constrained, prescribed volcanic aerosol treatment in E3SMv2. Global stratospheric aerosol size distributions identify the nucleation and growth of sulfate aerosol from volcanically injected SO2 from both major and minor volcanic eruptions from 1991 to 1993. The modeled aerosol effective radius is consistently lower than satellite and in situ measurements (max differences of ∼ 30 %). Comparisons with in situ size distribution samples indicate that this simulated underestimation in both E3SMv2-SPA and CESM2-WACCM is due to overly small accumulation and coarse-mode aerosols 6–18 months post-eruption, with E3SMv2-SPA simulating ∼ 50 % of the coarse-mode geometric mean diameters of observations 11 months post-eruption. Effective radii from the models and observations are used to calculate offline scattering and absorption efficiencies to explore the implications of smaller simulated aerosol size for the Pinatubo climate impacts. Scattering efficiencies at wavelengths of peak solar irradiance (∼ 0.5 µm) are 10 %–80 % higher for daily samples in models relative to observations through 1993, suggesting higher diffuse radiation at the surface and a larger cooling effect in the models due to the smaller simulated aerosol; absorption efficiencies at the peak wavelengths of outgoing terrestrial radiation (∼ 10 µm) are 15 %–40 % lower for daily samples in models relative to observations, suggesting an underestimation in stratospheric heating in the models due to the smaller simulated aerosol. These potential biases are based on aerosol size alone and do not take into account differences in the aerosol number. The overall agreement of E3SMv2-SPA with observations and its similar performance to the well-validated CESM2-WACCM makes E3SMv2-SPA a viable alternative to simulating climate impacts from stratospheric sulfate aerosols.

Brown, Hunter York (ORCID:0000000218147874)↗
NASA NTRS1992

Raman Lidar Measurements of Pinatubo Aerosols over Southeastern Kansas During November-december 1991

The eruptions of the Philippine volcano Pinatubo during June 1991 produced large amounts of stratospheric aerosols that could significantly affect earth's climate as well as trigger stratospheric ozone depletion through heterogeneous chemical reactions. Information regarding the physical and optical properties of these aerosols is required to quantify those effects. By measuring both the elastically backscattered signal and the inelastic signal produced by Raman scattering from nitrogen molecules, Raman lidar can provide some of this information. In this presentation we discuss Raman lidar measurements of the scattering ratio, backscattering, extinction, extinction/backscattering ratio, and optical thickness of the Pinatubo aerosols over southeastern Kansas made on 10 nights during November and December, 1991. The Raman lidar developed at GSFC is a trailer-based system which uses an XeF excimer laser to transmit light at 351 nm. The light backscattered by molecules and aerosols at this wavelength is detected as well as Raman scattered light from water vapor, nitrogen, and oxygen molecules. Since background skylights interfere with the detection of the Raman signals the data discussed in this paper were acquired only at night.

Ferrare, R. A.↗
NASA NTRS1992

Lidar Observations of Stratospheric Aerosol Layer After the Mt. Pinatubo Volcanic Eruption

The volcano Mt. Pinatubo located on the Luzon Island, Philippines, had explosively erupted on June 15, 1991. The volcanic eruptions such as volcanic ash, SO2 and H2O reached into the stratosphere over 30 km altitude by the NOAA-11 satellite observation and this is considered one of the biggest volcanic eruptions in this century. A grandiose volcanic eruption influences the atmosphere seriously and causes many climatic effects globally. There had been many impacts on radiation, atmospheric temperature and stratospheric ozone after some past volcanic eruptions. The main cause of volcanic influence depends on stratospheric aerosol, that stay long enough to change climate and other meteorological conditions. Therefore it is very important to watch stratospheric aerosol layers carefully and continuously. Standing on this respect, we do not only continue stratospheric aerosol observation at Tsukuba but also have urgently developed another lidar observational point at Naha in Okinawa Island. This observational station could be thought valuable since there is no lidar observational station in this latitudinal zone and it is much nearer to Mt. Pinatubo. Especially, there is advantage to link up these two stations on studying the transportation mechanism in the stratosphere. In this paper, we present the results of lidar observations at Tsukuba and Naha by lidar systems with Nd:YAG laser.

Nagai, Tomohiro↗
NASA NTRS1992

Interpretation of DIAL Measurements of Lower Stratospheric Ozone in Regions with Pinatubo Aerosols

The influence of volcanic aerosols on stratospheric ozone is a topic of current interest, especially with the June 15, 1991 eruption of Mt. Pinatubo in the Philippines. Lidar has been used in the past to provide aerosol profiles which could be compared with ozone profiles measured using ozonesondes to look for coincidences between volcanic aerosols and ozone decreases. The differential absorption lidar (DIAL) technique has the advantages of being able to measure ozone and aerosol profiles simultaneously as well as being able to cover large geographical regions rapidly. While there are problems associated with correcting the ozone profiles for the presence of aerosols, the corrections can be made reliably when the wavelengths are closely spaced and the Bernoulli method is applied. The DIAL measurements considered in this paper are those obtained in the tropical stratosphere in January 1992 during the Airborne Arctic Stratospheric Expedition (AASE-II). The determination of ozone profiles in the presence of Pinatubo aerosols is discussed in a companion paper.

Grant, William B.↗
NASA NTRS1992

Three-wavelength Lidar Measurements of Pinatubo Aerosol and Its Optical Properties

Enhanced stratospheric aerosols due to Mt. Pinatubo eruption have been measured using a YAG laser-based three wavelength lidar and a YAG laser-based large-scale lidar. Temporal variation of the integrated backscatter coefficient derived from the backscatter coefficient profiles were obtained. The present paper describes some results of optical properties analysis using lidar data obtained since Dec., 1991 when the main body of aerosols started to appear over Japan. The derived properties of the Pinatubo aerosols are extinction to backscatter ratios, wavelength dependencies of backscatter coefficients and extinction coefficients, and optical thickness. The analysis is based on the assumption of similarity in backscatter profiles for three wavelengths which are derived from lidar signals using the Fernald equation with assumed extinction to backscatter ratios.

Sasano, Y.↗
NASA NTRS1992

L625 Lidar Measurements of Pinatubo Volcanic Cloud at Hefei

The Pinatubo volcano erupted violently between June 9-17, 1991. This eruption was much larger than the El Chichon volcanic eruption in April, 1982. Because of the effects on the global environment, much attention was focused on the measurements of the volcanic cloud. The 84 scattering-ratio profiles of the volcanic cloud have been obtained by our L625 lidar system. The conclusions from studies of the data are: (1) Pinatubo volcanic cloud was present over Hefei after 40 days from eruption; (2) the peak scattering ratio varied violently in July and August of 1991; (3) the height of the peak scattering ratio is between about 18 to 25 km; and (4) since August 28, 1991, the optical depth was about one order of magnitude larger than before the eruption.

Hu, Huanling↗
NASA NTRS1992

Latitudinal survey of spectral optical depths of the Pinatubo volcanic cloud - Derived particle sizes, columnar mass loadings, and effects on planetary albedo

Airborne measurements are examined of spectral optical depths, radiative fluxes, and scattered radiation fields during the NASA Caribbean mission (July 7-14, 1991) to characterize the Pinatubo volcanic cloud. The latitudinal and spectral dependence are reported of the volcanic cloud's optical depth. From these measurements moments of the particle-size distribution are determined. The change in planetary albedo induced by the volcanic cloud is calculated for the range of measured optical depths with the objective of assessing the impact on the solar radiation budget. Mid-visible optical depths higher than 0.4 were observed, placing the Pinatubo stratospheric cloud among the thickest ever measured. The latitudinal distribution of extinction shows that by July 7, 1991 the volcanic cloud had extended to 30 deg N. The effective particle radius was determined to be between 0.18 and 0.35 micron with a corresponding columnar mass loading between 35 and 80 mag/sq m.

Valero, Francisco P. J.↗
NASA NTRS1992

Differential SO2 column measurements of the Mt. Pinatubo volcanic plume

Differential SO2 column measurements of the Mt. Pinatubo volcanic plume were made from a NASA Electra aircraft flying in the Caribbean in July, 1991. The mean column content of the volcanic plume in the Caribbean was 25 micro-atm m (2.5 Dobson units) with periods of over 100 micro-atm m observed. The data indicate that an aerosol absorption or scattering effect occurs for long slant paths (low sun-elevation angles) and that 41 micro-atm m (an average obtained for 1-2 airmasses) is more representative of a true column average. Dispersion of the initial cloud from Mt. Pinatubo and a one-month SO2-to-sulfate conversion-time constant are in good agreement with the column contents found here.

Hoff, Raymond M.↗
NASA NTRS1992

Potential climate impact of Mount Pinatubo eruption

The GISS global-climate model is used to make a preliminary estimate of Mount Pinatubo's climate impact. Assuming the aerosol optical depth is nearly twice as great as for the 1982 El Chichon eruption, the model forecasts a dramatic but temporary break in recent global warming trends. The simulations indicate that Pinatubo occurred too late in the year to prevent 1991 from becoming one of the warmest years in instrumental records, but intense aerosol cooling is predicted to begin late in 1991 and to maximize late in 1992. The predicted cooling is sufficiently large that by mid 1992 it should even overwhelm global warming associated with an El Nino that appears to be developing, but the El Nino could shift the time of minimum global temperature into 1993. The model predicts a return to record warm levels in the later 1990s. The effect is estimated of the predicted global cooling on such practical matters as the severity of the coming Soviet winter and the dates of cherry blossoming next spring.

Hansen, James↗
NASA NTRS1993

Changes in stratospheric ozone and temperature due to the eruptions of Mt. Pinatubo

The paper investigates the impact of the Mt. Pinatubo eruptions on the total column ozone measured from the Nimbus 8 TOMS and the NOAA-11 SBUV/2 spectrometers. Within a few months after the eruptions, the total column ozone decreased by 5-6 percent in the tropics, 3-4 percent at midlatitudes, and 6-9 percent at high latitudes in the Northern Hemisphere. After the effects of quasi-biennial oscillations and interannual variability are taken into account, the decrease in the column ozone attributed to volcanic eruptions at these latitudes may not be more than 2-4 percent. The most noticeable effect on the Pinatubo eruptions, as observed during the El Chichon period, is the breakdown of the phase relation between ozone and temperature. This is attributed to additional heating in the lower stratosphere caused by volcanic aerosols.

Chandra, S.↗