Hal Maring

Accurate Monitoring of Terrestrial Aerosols and Total Solar Irradiance: Introducing the Glory Mission

The NASA Glory mission is intended to facilitate and improve upon long-term monitoring of two key forcings influencing global climate. One of the missions principal objectives is to determine the global distribution of detailed aerosol and cloud properties with unprecedented accuracy, thereby facilitating the quantification of the aerosol direct and indirect radiative forcings. The other is to continue the 28-yr record of satellite-based measurements of total solar irradiance from which the effect of solar variability on the Earths climate is quantified. These objectives will be met by flying two state-of-the-art science instruments on an Earth-orbiting platform. Based on a proven technique demonstrated with an aircraft-based prototype, the Aerosol Polarimetry Sensor (APS) will collect accurate multiangle photopolarimetric measurements of the Earth along the satellite ground track within a wide spectral range extending from the visible to the shortwave infrared. The Total Irradiance Monitor (TIM) is an ...

Chemical and physical characteristics of nascent aerosols produced by bursting bubbles at a model air‐sea interface

inorganic aerosol constituents were similar to those in ambient air. Ca 2+ was significantly enriched relative to seawater (median factor = 1.2). If in the form of CaCO3, these enrichments would have important implications for pH-dependent processes. Other inorganic constituents were present at ratios indistinguishable from those in seawater. Soluble organic carbon (OC) was highly enriched in all size fractions (median factor for all samples = 387). Number size distributions exhibited two lognormal modes. The number production flux of each mode was linearly correlated with bubble rate. At 80% RH, the larger mode exhibited a volume centroid of 5-mm diameter and included 95% of the inorganic sea-salt mass; water comprised 79% to 90% of volume. At 80% RH, the smaller mode exhibited a number centroid of 0.13-mm diameter; water comprised 87% to 90% of volume. The median mass ratio of organic matter to sea salt in the smallest size fraction (geometric mean diameter = 0.13 mm) was 4:1. These results support the hypothesis that bursting bubbles are an important global source of CN and CCN with climatic implications. Primary marine aerosols also influence radiative transfer via multiphase processing of sulfur and other climate-relevant species.

Chemical mass closure and assessment of the origin of the submicron aerosol in the marine boundary layer and the free troposphere at Tenerife during ACE-2

The organic, inorganic, mineral content and mass concentration of the submicron aerosol were measured in June−July 1997 on Tenerife in the marine boundary layer (MBL) and the free troposphere (FT). Aerosol size distributions were measured simultaneously at the same sites. The submicron aerosol mass concentrations derived from the chemical composition and calculated from the number size distributions agreed within the experimental uncertainties both in the MBL (±47%) and the FT (±75%). However, the analytical uncertainties in the concentration of organic compounds (OC) for the average sample collected in the MBL (-97, +77%) and the FT (±74%) were high. The average contribution of aerosol various components to the submicron aerosol mass were calculated for different air masses. The absolute uncertainties in these contributions were calculated by adding random uncertainties quadratically and possibly systematic errors in a conservative way. In the unperturbed MBL, the aerosol average composition (± the absolute uncertainty in the contribution) was 37 (-3, +9)% for non-sea-salt SO42-+ NH4+, 21 (-2, +10)% for sea-salt, and 20 (-7, +11)% OC (N=19). In the unperturbed FT, OC and SO42- accounted for 43 (±20)% and 32 (-5, +3)% of the submicron aerosol mass, respectively (N=15). Considering these aerosol compositions, we suggest that the source for the FT aerosol could be the transport of continental aerosol through precipitating convective clouds. A simple budget calculation shows, that in background conditions, the MBL and FT aerosol compositions are consistent with the hypothesis that the MBL aerosol is formed by the dilution of continental aerosol by FT air, modified by deposition and condensation of species of oceanic origin. Dramatic continental aerosol outbreaks were observed in both the MBL and the FT. The aerosol outbreaks in the MBL were due to transport of polluted air masses from Europe. They were characterized mainly by increases in SO42-+ NH4+, making up 75 (-5, +19)% of the submicron aerosol mass. The aerosol outbreaks in the FT were due to advection of desert dust, probably mixed with pollution aerosol.

Preface to special section on East Asian Studies of Tropospheric Aerosols: An International Regional Experiment (EAST‐AIRE)

daily mean surface solar radiation by � 30–40 W m � 2 , but barely changed solar reflection at the top of the atmosphere. Aerosol loading, particle size and composition vary considerably with location and season. The MODIS AOD data from Collection 5 (C5) agree much better with ground data than earlier releases, but considerable discrepancies still exist because of treatments of aerosol SSA and surface albedo. Four methods are proposed/adopted to derive the SSA by means of remote sensing and in situ observation,

INDOEX aerosol: A comparison and summary of chemical, microphysical, and optical properties observed from land, ship, and aircraft

converged on values of about 3.8 ± 0.3 m 2 g � 1 , providing a firm constraint upon the description and modeling of haze optical properties. MSE values trended lower with more dilute haze but became more variable in clean air or regions of low concentrations. This cross-platform comparison resolved a number of measurement differences but also revealed that regional characterization from different platforms results in differences linked to variability in time and space. This emphasizes the need to combine such efforts with coordinated satellite and modeling studies able to characterize large-scale regional structure and variability. These comparisons also indicate that ‘‘closure’’ between chemical, microphysical, and optical properties across platforms to better than about 20% will require significant improvements in techniques, calibration procedures, and comparison efforts. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0394 Atmospheric Composition and Structure: Instruments and techniques; KEYWORDS: INDOEX, data comparison, optical properties, chemistry, microphysics, size distributions

Effect of relative humidity on light scattering by mineral dust aerosol as measured in the marine boundary layer over the tropical Atlantic Ocean

Using an integrating nephelometer, we measured aerosol light scattering during a month-long experiment conducted in April 1994 on Barbados, West Indies (13.17°N, 59.43°W). Concurrent measurements of aerosol composition showed that the trade wind aerosol mass was alternatively dominated by sea salt and by mineral dust transported from North Africa. Dust concentrations ranged from 0.9 to 257 μg m−3, and sea salt ranged from 9.4 to 29 μg m−3. Nonsea-salt sulfate (nss SO4=) was generally a minor component with concentrations ranging from 0.5 to 4.2 μg m−3. We obtained hygroscopic growth factors (HGF) by calculating the ratio of the aerosol scattering coefficient (ASC) measured at ambient relative humidity (RH), which ranged from 67% to 83%, to the ASC measured with the sample air stream heated so as to reduce the RH to under 40%. Over the course of the experiment, HGF ranged from 1.13 to 1.69, with lower values corresponding to high dust concentration periods. By a variety of procedures, including the chemical apportioning of ASC, we derived the HGF for mineral dust; depending on the technique used, values ranged from 1.0 to 1.1. In contrast, we obtain for sea salt an HGF of 1.8±0.2, a value consistent with previously reported measurements. The low HGF values obtained for dusty periods suggest that only minor amounts of hygroscopic materials are associated with dust. Consequently, the radiative properties of North African dust in the atmosphere will be relatively insensitive to RH changes.

Chemical, microphysical, and radiative effects of Indian Ocean aerosols

Received 19 April 2002; revised 2 August 2002; accepted 6 August 2002; published 14 December 2002. [1] Extensive and long-term multistation measurements of aerosol properties and radiative fluxes were carried out in the haze plume off the South Asian continent. These experiments are carried out at Kaashidhoo Climate Observatory (KCO) (4.95� N, 73.5� E), Minicoy (8.5� N, 73.0� E), and Trivandrum (8.5� N, 77.0� E). In addition, the top of the atmosphere fluxes were measured simultaneously by the CERES radiation budget instrument. Long-term observations (more than 15 years) over Trivandrum show that there is a gradual increase in aerosol visible optical depth from � 0.2 in 1986 to � 0.4 in 1999. Pre- and post-monsoon aerosol characteristics are examined to study the seasonal variations. The impact of aerosols on short-wave radiation budget is estimated using direct observations of solar radiation using several independent ground-based radiometers and satellite data as well as from modeled aerosol properties. It was observed that ‘‘excess absorption’’ is not needed to model diffuse fluxes. The lower atmospheric heating due to absorbing aerosols was as high as � 20 W m � 2 which translates to a heating rate perturbation of � 0.5� K/day. The effect of aerosol mixing state (internally and externally) on aerosol forcing appears to be negligible. A sensitivity study of the effect of aerosols over land in contrast to that over the ocean shows an enhancement in lower atmosphere heating by about 40% simultaneous with a reduction of � 33% in surface cooling. Increasing sea-surface winds increase aerosol cooling due to increased sea salt aerosol concentrations, which can partly offset the heating effect due to absorbing aerosols. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 1610 Global Change: Atmosphere (0315, 0325); 1704 History of Geophysics: Atmospheric sciences; 4801 Oceanography: Biological and Chemical: Aerosols (0305); KEYWORDS: aerosols, radiative forcing, climate, chemical composition

Planning, implementation and scientific goals of the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field mission

The Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field mission based at Ellington Field, Texas, during August and September 2013 employed the most comprehensive airborne payload to date to investigate atmospheric composition over North America. The NASA ER-2, DC-8, and SPEC Inc. Learjet flew 57 science flights from the surface to 20 km. The ER-2 employed seven remote sensing instruments as a satellite surrogate and eight in situ instruments. The DC-8 employed 23 in situ and five remote sensing instruments for radiation, chemistry, and microphysics. The Learjet used 11 instruments to explore cloud microphysics. SEAC4RS launched numerous balloons, augmented Aerosol RObotic NETwork, and collaborated with many existing ground measurement sites. Flights investigating convection included close coordination of all three aircraft. Coordinated DC-8 and ER-2 flights investigated the optical properties of aerosols, the influence of aerosols on clouds, and the performance of new instruments for satellite measurements of clouds and aerosols. ER-2 sorties sampled stratospheric injections of water vapor and other chemicals by local and distant convection. DC-8 flights studied seasonally evolving chemistry in the Southeastern U.S., atmospheric chemistry with lower emissions of NOx and SO2 than in previous decades, isoprene chemistry under high and low NOx conditions at different locations, organic aerosols, air pollution near Houston and in petroleum fields, smoke from wildfires in western forests and from agricultural fires in the Mississippi Valley, and the ways in which the chemistry in the boundary layer and the upper troposphere were influenced by vertical transport in convective clouds.

Urban aerosol radiative properties: Measurements during the 1999 Atlanta Supersite Experiment

calculated with a Mie code yielding Eap = 9.5 ± 1.5 m 2 g 1 , while EC mass summed from the impactor stages in comparison to measured sap gives Eap = 9.3 ± 3.2 m 2 g 1 .M ie light-scattering calculations using inputs of measured mass and EC size distributions give geometric mean light scattering and absorption Dp = 0.54 and 0.13 mm, respectively, and show the dominance of the submicrometer diameter particles to light extinction in the urban environment. Based on the measured aerosol optical depth in Atlanta, da (500 nm) = 0.44 ± 0.22, and other radiative measurements, a best estimate of the average direct aerosol radiative forcing at the top of the atmosphere (a measure of the climate significance) is F= 11 ± 6 W m 2 in Atlanta. This value is an order of magnitude greater than global mean estimates for aerosols underscoring the influence of aerosol particles on radiative transfer in the urban environment. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0394 Atmospheric Composition and

Saharan dust transport to the Caribbean during PRIDE: 2. Transport, vertical profiles, and deposition in simulations of in situ and remote sensing observations

We simulate Saharan dust transport during the Puerto Rico Dust Experiment (June-July 2000) with a three-dimensional aerosol transport model driven by assimilated meteorology. The model does a reasonable job of locating the dust plume as it emerges from Africa but transports it somewhat farther south in the western North Atlantic Ocean than is seen in satellite imagery. The model is able to simulate low-level, uniformly mixed, and elevated vertical dust layer profiles over Puerto Rico similar to observations made in PRIDE. We determine that the variability in the dust vertical profile across the North Atlantic Ocean is most strongly associated with descent of the dust by sedimentation and downward vertical winds during transit rather than low-level transport directly from source regions. Wet removal plays a key role in modulating this process. Assuming our dust is 3.5% iron by mass, we estimate July 2000 iron deposition into the North Atlantic Ocean to be between 0.71 and 0.88 Tg, which is consistent with estimates derived from observed surface dust mass concentrations. We estimate that if annual dust deposition remains constant at five times our July 2000 estimates, there is an accumulation of 1 m of sediment from Saharan dust over the Florida peninsula every one million years.