Murali Natarajan

NASA, Langley Research Center · Science Directorate

The Asian Tropopause Aerosol Layer (ATAL) represents an accumulation of aerosol in the upper troposphere and lower stratosphere associated with the Asian Summer Monsoon. Here we simulate the ATAL for summer 2013 with the GEOS‐Chem chemical transport model and explore the likely composition of ATAL aerosols and the relative contributions of regional...

We describe and show results from a series of field campaigns using balloon-borne instruments launched from India and Saudi Arabia during the summers 2014-2017 to study the nature, formation and impacts of the Asian Tropopause Aerosol Layer (ATAL). The campaign goals were to i) characterize the optical, physical and chemical properties of the ATAL,...

Volcanic eruptions are important causes of natural variability in the climate system at all time scales. Assessments of the climate impact of volcanic eruptions by climate models almost universally assume that sulfate aerosol is the only radiatively active volcanic material. We report satellite observations from the Cloud-Aerosol Lidar with Orthogo...

The Asian tropopause Aerosol Layer (ATAL) is a seasonal aerosol feature occurring in the Upper Troposphere and Lower Stratosphere (UTLS) above Asia during the Summer Asian Monsoon. Vertically resolved aerosol backscatter profiles from the Cloud-Aerosol Lidar and Infrared Pathfinder satellite Observation (CALIPSO) mission and extinction profiles fro...

We use the Mars Weather Research and Forecasting (MarsWRF) general circulation model to simulate the atmospheric structure corresponding to the landing location and time of the Mars Exploration Rovers (MER) Spirit (A) and Opportunity (B) in 2004. The multiscale capability of MarsWRF facilitates high-resolution nested model runs centered near the la...

Satellite observations have shown that the Asian Summer Monsoon strongly influences the upper troposphere and lower stratosphere (UTLS) aerosol morphology through its role in the formation of the Asian Tropopause Aerosol Layer (ATAL). Stratospheric Aerosol and Gas Experiment II solar occultation and Cloud-Aerosol Lidar and Infrared Pathfinder Satel...

We use nighttime measurements from the Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, together with a Lagrangian trajectory model, to study the initial dispersion of volcanic aerosol from the eruption of Mt. Nabro (Ethiopia/Eritrea) in June 2011. The Nabro eruption reached the upper troposphere and lower stra...

Version 6 ozone profiles for 1978-1979 from the Limb Infrared Monitor of the Stratosphere experiment on the NIMBUS 7 satellite (or LIMS v6) are assimilated into an updated version of the GEOS-5 model of NASA. First, an assimilation study is carried out using GEOS-5 version 7.2 (v7.2) and solar backscatter ultraviolet (SBUV) version 8.6 ozone profil...

We use nighttime measurements from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, together with a Lagrangian trajectory model, to study the initial dispersion of volcanic aerosol from the eruption of Mt. Nabro (Ethiopia/Eritrea) in June 2011. The Nabro eruption reached the lower stratosphere directly, and...

Arctic ozone depletion events (ODEs) are caused by halogen catalyzed ozone loss. In situ chemistry, advection of ozone-poor air mass, and vertical mixing in the lower troposphere are important factors affecting ODEs. To better characterize the ODEs, we analyze the combined set of surface, ozonesonde, and aircraft in situ measurements of ozone and b...

Arctic ozone depletion events (ODEs) are due to catalytic ozone loss driven by halogen chemistry. The presence of ODEs is affected not only by in situ chemistry but also by transport including advection of ozone-poor air mass and vertical mixing. To better characterize the ODEs, we analyze the combined set of surface, ozonesonde, and aircraft in si...

Simulations of tropospheric ozone and carbonaceous aerosol distributions, conducted with the Real-time Air Quality Modeling System (RAQMS), are used to study the effects of major outbreaks of fires that occurred in three regions of Asia, namely Thailand, Kazakhstan, and Siberia, during spring 2008. RAQMS is a global scale meteorological and chemica...

We use ozone and carbon monoxide measurements from the Tropospheric Emission Spectrometer (TES), model estimates of Ozone, CO, and ozone pre-cursors from the Real-time Air Quality Modeling System (RAQMS), and data from the NASA DC8 aircraft to characterize the source and dynamical evolution of ozone and CO in Asian wildfire plumes during the spring...

Long-range transport of ozone precursor species and carbonaceous aerosols emitted by wildfires may affect the atmospheric composition and regional climate far away from the location of the fires. Major outbreaks of fires occurred in 3 areas of Asia, Kazakhstan, Siberia, and Thailand, during the spring of 2008. Satellite and aircraft-based observati...

Emissions from subsonic aircraft can have potential impact on radiatively-important gas phase and particulate components in the upper troposphere/lower stratosphere and their precursors. These include CO2,O3, CH4, water, sulfate and soot aerosols, contrails and cirrus clouds. In particular, emissions of NOx induces production of O3 (positive radiat...

We use ozone (O3) and carbon monoxide (CO) satellite measurements from the Tropospheric Emission Spectrometer (TES), simulations from the Real-time Air Quality Modeling System (RAQMS) and aircraft data from the NASA DC8 aircraft to characterize the chemical and dynamical evolution of Asian wildfire plumes during the spring ARCTAS campaign 2008. On...

The quality of the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) nitric acid (HNO3) and nitrogen dioxide (NO2) profiles and distributions of 1978/1979 is described after their processing with an updated, Version 6 (V6) algorithm and subsequent archival in 2002. Estimates of the precision and accuracy of both of those species are develop...

We examine tropospheric ozone production and loss in Thailand, Kazakhstan and Siberian fire plumes transported over Northern Pacific during spring 2008 ARCTAS campaign. We used collocated O3 and CO profiles as measured by the Tropospheric Emission Spectrometer (TES), Regional Air Quality Modeling System (RAQMS) and ozone from the Airborne UV Differ...

The quality of the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) nitric acid (HNO₃) and nitrogen dioxide (NO₂) profiles and distributions of 1978/1979 are described after their processing with an updated, Version 6 (V6) algorithm and subsequent archival in 2002. Estimates of the precision and accuracy of both of th...

This report describes the quality of the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) water va- por (H2O) profiles of 1978/79 that were processed with a Version 6 (V6) algorithm and archived in 2002. The V6 pro- files incorporate a better knowledge of the instrument atti- tude for the LIMS measurements along its orbits, leading to impr...

Consistency analysis is conducted between satellite derived BrO measurements and in situ observations of bromine compounds and ozone during the spring-phase of the NASA ARCTAS experiment and the NOAA ARCPAC experiment. A regional 3-D chemical transport model (REAM) is also used in this study to investigate the ozone depletion events observed by air...

We examine tropospheric ozone production and loss in Siberian fire plumes transported over Northern Pacific during spring 2008 ARCTAS campaign using collocated O3 and CO profiles as measured by the Tropospheric Emission Spectrometer (TES) and ozone from the Airborne UV Differential Absorption Lidar (DIAL). High CO concentrations, over 200 ppbv, are...

This report describes the quality of the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) water vapor (H2O) profiles of 1978/79 that were processed with a Version 6 (V6) algorithm and archived in 2002. The V6 profiles incorporate a better knowledge of the instrument attitude for the LIMS measurements along its orbits, leading to improvemen...

Current climate change scenarios predict increases in biomass burning in terms of increases in fire frequency, area burned, fire season length and fire season severity, particularly in boreal regions. Climate and weather control fire danger, which strongly influences the severity of fire events, and these in turn, feed back to the climate system th...

Sharp gradients in concentrations near sunrise/sunset conditions can lead to asymmetric distribution of species along the line of sight (LOS) in a solar occultation experiment. Model derived correction factors have been used for stratospheric NO and NO2 retrievals in HALOE and ATMOS experiments. Mesospheric ozone also exhibits such inhomogeneity al...

We evaluate Aura Microwave Limb Sounder version 2.2 measurements of O3, HCl, and H2O with version 19 HALOE observations using a model-assisted, noncoincident intercomparison technique. Air parcels in the Langley Research Center Lagrangian chemistry and transport model (LCTM) are initialized from HALOE observations made during three different 3-week...

The Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) radiance profile dataset of 1978/79 was reconditioned and reprocessed to Version 6 (V6) profiles of temperature and species that are improved significantly over those from Version 5 (V5). The LIMS V6 dataset was archived for public use in 2002. Improvements for its ozone include: (1) a m...

1] Global ozone analyses, based on assimilation of stratospheric profile and ozone column measurements, and NOy predictions from the Real-time Air Quality Modeling System (RAQMS) are used to estimate the ozone and NOy budget over the continental United States during the July–August 2004 Intercontinental Chemical Transport Experiment–North America (...

The Nimbus 7 LIMS experiment obtained daily distributions of ozone from late October 1978 through late May 1979 and with good vertical resolution and spatial sampling along its orbital tangent tracks. The historic LIMS Version 5 (V5) dataset was archived in 1982. Studies of those data revealed detailed information about the roles of chemistry and t...

Solar occultation measurement of atmospheric species with short photochemical lifetimes poses some difficulties if sharp gradients are present in the species concentrations near sunrise/sunset conditions. These photochemically induced variations introduce asymmetries in the species distribution along the line of sight that need to be taken into acc...

Significant perturbations to the odd nitrogen mixing ratios in the high latitude upper stratosphere are seen in the Halogen Occultation Experiment (HALOE) data during April, 2004. Sunrise observation of 99.1 ppbv of NOx (NO + NO2) at 68N represents the largest NOx measured near 2 hPa. Examination of potential vorticity maps indicates that these hig...

The Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) experiment operated for just over 7 months in 1978/1979, as planned. Its version 5 (V5) dataset was archived for public use in 1983. Subsequently, several important improvements were realized about the LIMS instrument, its forward radiance model, and the line parameters (from HITRAN 92 o...

The NASA Langley Research Center and University of Wisconsin Regional Air Quality Modeling System (RAQMS) is used to estimate the tropospheric ozone budget over east Asia during the NASA Global Tropospheric Experiment (GTE) Transport and Chemical Evolution over the Pacific (TRACE-P) mission. The computed ozone budget explicitly accounts for stratos...

The LaRC Lagrangian Chemical Transport Model (LaRC LCTM) is used to simulate the kinematic and chemical evolution of an ensemble of trajectories initialized from Halogen Occultation Experiment (HALOE) and Polar Ozone and Aerosol Measurement (POAM) III atmospheric soundings over the SAGE III-Ozone Loss and Validation Experiment (SOLVE) campaign peri...

Recently reprocessed LIMS dataset has been used with a contemporary photochemical model to study the balance between photochemical production and destruction of ozone in the upper stratosphere. Model results corresponding to January 1979 indicate that the ozone deficit is less than 15% in the pressure range of 5 to 0.5 mb between 50°S and 50°N lati...

Mesospheric nitric oxide as observed by the Halogen Occultation Experiment (HALOE) and calculated by the Langley Research Center two-dimensional chemical transport model are compared on a daily and collocated basis for the period 920101 through 971231. Results show excellent agreement when energetic electron precipitation (EEP) from the outer trapp...

Intermittent high-speed solar wind streams impinging on the Earth's magnetosphere lead to space weather events which are manifested by a variety of processes. Among these processes is the acceleration of electrons, within the outer trapping region of the magnetosphere, with energies between 1 keV and 10 Mev. The precipitation of these electrons int...

Recent observational studies have demonstrated a linkage between the Sun and the Earth, driven by the tenuous high speed solar wind streams emanating from solar coronal holes. This linkage extends from the Sun through the near-space environment and the atmosphere to the lower stratosphere. It varies with time scales that range from days to decades....

The NASA Langley Research Center Interactive Modeling Project for Atmospheric Chemistry and Transport (IMPACT) model has been used to examine the response of the middle atmosphere to a large tropical stratospheric injection of sulfate aerosol, such as that following the June 1991 eruption of Mount Pinatubo. The influence of elevated aerosol on hete...

NASA Reference Publication 1292 [Prather and Remsberg, 1993] contains reports of the stratospheric model simulations of NOy for 1980, when the effects of volcanic aerosols on the partitioning of NOy should have been minimal. Those model runs included heterogeneous chemistry on background aerosols. Model values of NO2 and HNO3 were compared with tho...

Several middle atmospheric simulations have been carried out from January 1979 to December 1997 including most effects important to stratospheric O3. Results of these simulations for several species and species ratios have been compared in detail with observations made by the Halogen Occultation Experiment, the Polar Ozone and Aerosol Measurement I...

The stratospheric chemical characteristics of the NASA Langley Research Center Interactive Modeling Project for Atmospheric Chemistry and Transport model are evaluated. We focus on species relevant to stratospheric ozone including the main constituents of the odd nitrogen and inorganic chlorine families. Model-derived chemical climatologies resulti...

Model derived sensitivities of O3 near 40 km to solar UV flux changes (11-year and 27-day) fall within the range 0.36-0.55 with S11y ≈ S27d. These sensitivities derived from observations have been reported to be 0.91 and 0.39-0.46, respectively. This discrepancy appears to be due to long-term (2-10 years) fluctuations in stratospheric NO2 in the 19...

An analysis is carried out of the effects on middle atmospheric NOy and Oa of a coronal mass ejection (CME) event which occurred on May 12, 1997, and which is coupled with observed solar wind fluctuations. Observations of electron fluxes by instruments aboard the SAMPEX and N OAA 12 satellites indicate large enhancements of magnetospheric electron...

An analysis has been carried out of the effects of energetic electron precipitation (EEP) on stratospheric NOy, NO2, and O3. Solar wind observations used together with precipitating electron fluxes observed aboard TIROS spacecraft show a close relationship between the long- and short-term fluctuations in the solar wind and EEP over a period of 16 y...

Observations made by the HALOE instrument aboard UARS show very low stratospheric ozone in the Arctic and Antarctic summers of 1992 and 1993 [Park and Russell, 1994]. Large longitudinal variability is seen in ozone between 8 and 45 mb, poleward of 60° during late summer. This paper examines the cause of this variability using isentropic trajectory...

Satellite data show large declines in global (4.5%) and midlatitude (10%) ozone in the mid-1980s and during 1992 and 1993. Analyses of ozone, temperature, and aerosol records and two-dimensional chemical transport simulations have been carried out to develop an understanding of the causes of these changes. Simulations include contemporary homogeneo...

Simulations using SAMPEX and HALOE data suggest that NOy produced by thermospheric processes and by relativistic electron precipitation in the mesosphere and lower thermosphere have been important to stratospheric NOy and O3 during the austral spring in 1994. The relative importance of the two NOy sources is discussed. The results are supported by...

Observations of electron fluxes made by the PET and LICA instruments aboard SAMPEX have been used with NO measurements made by HALOE aboard UARS to provide evidence of mesospheric and lower thermospheric NO formation due to precipitating electrons. Results indicate significant NO increases from 70 to 120 km which are associated with the occurrence...

Simulations using SAMPEX and HALOE data suggest that NO_y produced by thermospheric processes and by relativistic electron precipitation in the mesosphere and lower thermosphere have been important to stratospheric NO_y and O_3 during the austral spring in 1994. The relative importance of the two NO_y sources is discussed. The results are supported...

In his paper, Aikin investigates the hypothesis that high latitude O3 distributions near 1 mbar are modified by the precipitation of relativistic electrons. The authors of this comment believe that Aikin's results are based on an incomplete analysis and contain misperceptions regarding studies done by the authors. Aikin's reply follows this comment...

This paper compares atmospheric total odd nitrogen and ozone computed with two different advective wind fields, one using climatological averages of ozone and temperature to obtain monthly averaged horizontal and vertical winds and the other using measurements from the LIMS instrument. Calculations using the former data show stronger poleward and d...

The photochemical partitioning of stratospheric odd chlorine and odd nitrogen is examined utilizing diurnal model calculations and data from the ATMOS experiment. This experiment, conducted during April-May 1985, employed a solar occultation method to obtain vertical profiles of temperature and various other trace constituents at 30 deg N and 48 de...

Using electron count rate data at geostationary orbit, daily energy spectra, extending from 30 keV to 15 MeV, have been developed for trapped relativistic electrons at 6.6 R{sub E}. These spectra have been used to model the flux of these electrons into the atmosphere at 120 km. Energy deposition calculations permit daily sources of HO{sub x} and NO...

Archived Stratospheric Aerosol and Gas Experiment (SAGE, SAGE 2) and Solar and Backscattered Ultraviolet (SBUV) data are used to examine lower stratospheric Oâ variations at 50° latitude in both hemispheres. These data indicate that from 1979 to 1985, 73-90% of the total Oâ changes have occurred below approximately 25 km in altitude. Significant O...

The authors examine in this paper the consistency of stratospheric ozone photochemistry using data from ATMOS and LIMS experiments. The ATMOS experiment measured vertical profiles of important trace constituents and temperature in the stratosphere during 1985. These observations have been used to constrain the levels of odd nitrogen and odd chlorin...

Analyses of stratospheric nitrogen dioxide distributions as measured by four different satellite experiments indicate midlatitude increases of up to 75 percent during the 1979-84 period. These increases are attributed to enhanced upper atmospheric formation of odd nitrogen during solar cycle 21 with downward transport to the stratosphere. The incre...

Photochemical calculations along 'diabatic trajectories' in the meridional phase are used to search for the cause of the dramatic springtime minimum in Antarctic column ozone. The results indicate that the minimum is principally due to catalytic destruction of ozone by high levels of total odd nitrogen. Calculations suggest that these levels of odd...

The present investigation has the objective to make use of the limb infrared monitor of the stratosphere (LIMS) data set in conducting stratospheric photochemical studies. A description of the data is provided. The data are utilized in a zero-dimensional model incorporating the relevant chemistry. The chemical reaction scheme considered is a subset...

The limb infrared monitor of the stratosphere, stratospheric and mesospheric sounder, and solar backscatter ultraviolet satellite measurements of stratospheric T, O3, NO2, HNO3, H2O, CH4, and solar flux are used in conjunction with a zero-dimensional, stratospheric, photochemical model to infer distributions of other constituents. For periods in Oc...

Reasonable lower-limit estimates of the latitude-altitude distribution of stratospheric NO(x) for December 1978 and March 1979 are presented. The lower-limit estimates are based on nighttime measurements of NO2 and HNO3 taken by the LIMS instrument aboard the NIMBUS 7 satellite. It is shown that the estimates do not depend upon model calculations o...

LIMS, SAMS, SBUV and in-situ data have been used to infer species not measured but which are of photochemical interest, e.g., O(3P), O(1D), NO, N2O5, OH, HO2, ClO and HCl. (LIMS = limb infrared monitor of the stratosphere; SAMS = stratospheric and mesospheric sounder; and SBUV = solar backscattered ultraviolet instrument.) Production and loss of od...

LIMS data at vernal equinox conditions are used to study the photochemistry of the upper stratosphere. The results indicate, and it has been recently reported, that with the use of recommended reaction rates, current models underestimate ozone mixing ratio by 20-40 percent. For ozone, good agreement with data is realized with the modification of si...

Nimbus 7 LIMS data and a photochemical model are used to show that the observed sharp latitudinal gradients in stratospheric wintertime NO2 are consistent with the conversion of NO2 to N2O5 at high latitudes. This conversion, and the sharp gradients, are brought about by the interaction between transport and photochemistry. Calculated variations sh...

The coupling that exists between infrared opacity changes and tropospheric (and to a lesser extent stratospheric) chemistry is explored in considerable detail, and the effects arising from various perturbations are examined. The studies are carried out with a fully coupled one-dimensional radiative-convective-photochemical model (RCP) that extends...

In the past, it was generally assumed that the early atmosphere of the Earth contained appreciable quantities of methane (CH4) and ammonia (NH3). This was the type of atmosphere believed to be the most suitable environment for chemical evolution, the nonbiological formation of complex organic molecules, the precursors of living systems. Photochemic...

In the past, it was generally assumed that the early atmosphere of the Earth contained appreciable quantities of methane (CH4) and ammonia (NH3). This was the type of atmosphere believed to be the most suitable environment for chemical evolution, the nonbiological formation of complex organic molecules, the precursors of living systems. Photochemic...

The effects of combined CO2 and CFCl3 and CF2Cl2 time-dependent scenarios on atmospheric O3 and temperature are described; the steady-state levels of O3 and surface temperature, to which the chlorofluoromethane scenario tends in the presence of twice and four time ambient CO2, are examined; and surface temperature changes, caused by the combined ef...

A one-dimensional radiative-convective photochemical model has been used to examine the response of stratospheric and total ozone to perturbations in the solar flux. The model considers a detailed chemical reaction mechanism; vertical transport is parameterized through eddy diffusion coefficients. The temperature profile is calculated using a radia...

Experiments have been carried out to investigate the time-dependent effects of combined releases of CO2 and chlorofluoromethanes (CFM) on stratospheric ozone and temperature. The analysis also examines the effects of steady-state variations in CFM, CO2, and solar UV flux levels on surface temperature and latitudinal temperature distribution. Result...

Ozone (O3) is a key atmospheric gas in considerations of the photochemistry/chemistry of the paleoatmosphere, chemical evolution, and the origin and evolution of life. The photochemistry/chemistry of atmospheric O3 in the paleoatmosphere is investigated using a one-dimensional photochemical model that includes the chemistry of oxygen, nitrogen, hyd...

The effect of long-term (11-year solar cycle) solar UV variability on stratospheric chemical and thermal structure has been studied using a time-dependent one-dimensional model. Previous studies have suggested substantial variations in local and total ozone, and in stratospheric thermal structure from solar minimum to solar maximum. It is shown her...

Measurement of short-lived photochemically-produced species in the stratosphere by solar occultation is difficult because the rapid variation of such species near the terminator introduces ambiguities in interpreting the measured absorption in terms of meaningful atmospheric abundances. These variations produce tangent path concentrations that are...

Evidence is presented which suggests that trends in the ozone concentration and stratospheric temperature, reported between the early 1960's and 1976, are to a large extent due to solar ultraviolet flux variability associated with the 11-year solar cycle. Radiative-convective-photochemical simulations of ozone and temperature variations have been m...

Thesis--State University of New York at Stony Brook. Includes bibliographical references (leaves 51-57).

A reprocessing of the Nimbus 7 LIMS Level 2 dataset (its Version 6 or V6 profiles) is now complete. The revised algorithm employs a number of changes that affect its temperature T(p) and species profiles. Comparisons with the archived (Version 5 or V5) dataset show that the V6 temperatures are warmer in the mesosphere and in better agreement with c...