ISSN:0886-6236    

DOI:10.1029/GB004i002p00119

年代:1990

数据来源: WILEY

摘要:

The 1988 Global Change Expedition/Coordinated Air‐Sea Experiment/Western Atlantic Ocean Experiment (GCE/CASE/WATOX) was a multifaceted research program designed to study atmospheric and oceanic processes affecting the biogeochemical cycles of carbon, nitrogen, sulfur, and trace metals in the North Atlantic Ocean region. Field work included (1) a 49‐day research cruise aboard NOAA shipMt. Mitchell(Global Change Expedition) from Norfolk, Virginia, to Bermuda, Iceland, the Azores, and Barbados, (2) eight flights of the NOAA King Air research aircraft, four off the Virginia Capes and four near Bermuda (CASE/WATOX), and (3) a research cruise aboard the yachtFleurtienear Bermuda (WATOX). Objectives of GCE/CASE/WATOX were (1) to examine processes controlling the mesoscale distributions of productivity, chlorophyll, and phytoplankton growth rates in Atlantic surface waters, (2) to identify factors controlling the distribution of ozone in the North Atlantic marine boundary layer, and (3) to estimate the contributions of sources on surrounding continents to the biogeochemical cycles of sulfur, nitrogen, and trace metals over the North Atlantic region during the boreal summer season. The individual papers in this and the next two issues of Global Biogeochemical Cycles provide details on the results and analyses of the individual measurement efforts. This paper provides a brief overview of GCE/CASE/WA

ISSN:0886-6236    

DOI:10.1029/GB004i002p00121

年代:1990

数据来源: WILEY

摘要:

During the summer of 1988, a team of scientists aboard the NOAA shipMt. Mitchelland the NOAA King Air aircraft investigated the spatial distributions of sulfur, nitrogen, and related species and their interactions over the North Atlantic Ocean. In support of these measurements, meteorological data from the National Meteorological Center and from rawinsonde data obtained from the ship were archived and back trajectories were calculated. A summary of the meteorological conditions during the cruise is presented using synoptic maps, soundings, cross sections, and isobaric and isentropic back trajectories. Since day‐to‐day variability of the synoptic situation was generally small, one representative day was chosen to illustrate the overall meteorology. During the cruise, three synoptic regimes were encountered: (1) north of the polar front, (2) under the Bermuda/Azores high, and (3) under the Intertropical Convergence Zone (ITCZ). Soundings from three different days illustrate these regimes. Boundary layer depth and cloud layers were also estimated from all the soundings. Cross sections of temperature, wind, and relative humidity describing the vertical structure of the atmosphere along the cruise show the general day‐to‐day uniformity except near the polar front and near the ITCZ boundary. The back trajectories show general air flow patterns and the land mass source regions of air reaching the ship within three days. For parts of the cruise, air reached the ship from North America, Iceland or Greenland, Africa, and South

ISSN:0886-6236    

DOI:10.1029/GB004i002p00133

年代:1990

数据来源: WILEY

摘要:

We developed a high‐resolution technique to measure major reactive trace gases and the chemical composition of size‐segregated aerosols in the troposphere as part of the 1988 Global Change Expedition/Coordinated Air‐Sea Experiment/Western Atlantic Ocean Experiment. We sampled air over the western North Atlantic Ocean from the NOAA King Air research aircraft and NOAA shipMt. Mitchellduring July. Our system used filter packs containing an upstream, 90‐mm quartz filter to collect particles followed by two 90‐mm rayon filters impregnated with 10% K2C03‐10% glycerol to collect alkaline reactive gases. Paired filter packs were exposed when the aircraft sampled the boundary layer. An upstream cyclone with a 50% aerodynamic cut radius of approximately 0.4 μm removed large particles from one of the filter‐pack inlets. Air was sampled at an average rate of 0.12 m3STP min−1for the fine filter packs and 0.26 m3STP min−1for the total over intervals of 45 min to 90 min. Particulate‐phase concentrations of major anions (SO42−, CH3SO3−, NO3−, Cl−) and organic species (HCOOt[HCOO−and HCOOH] and CH3COOt[CH3COO−and CH3COOH]) were measured by gradient elution ion chromatography; base cations (Ca2+, Mg2+, Na+, K+) by atomic‐absorption spectroscopy; NH4+by automated colorimetry; and H+by glass electrode. We quantified SO2, HNO3, and HCl using two isocratic ion chromatography methods. This technique provided higher signal‐to‐noise ratios allowing increased temporal and spatial resolution, pH determination of particulate‐phase filter extracts, and

ISSN:0886-6236    

DOI:10.1029/GB004i002p00151

年代:1990

数据来源: WILEY

摘要:

As a part of the Global Change Expedition/Coordinated Air‐Sea Experiment/Western Atlantic Ocean Experiment (GCE/CASE/WATOX), size distributions of marine aerosols were measured at two altitudes of about 2750 and 150 m above sea level (asl) over the size range 0.1 ∼ 32 μm. Lognormal fitting was applied to the corrected aerosol size spectra to determine the volume and surface area size distributions of the CASE‐WATOX marine aerosols. Each aerosol size distribution was fitted with three lognormal distributions representing fine‐, large‐, and giant‐particle modes. Water volume fraction and dry particle size of each aerosol size distribution were also calculated using empirical formulas for particle size as a function of relative humidity and particle type. Because of the increased influence from anthropogenic sources in the continental United States, higher aerosol volume concentrations were observed in the fine‐particle mode near‐shore off the east coast; 2.11 and 3.63 μm3cm−3for free troposphere (FT) and marine boundary layer (MBL), compared with the open‐sea Bermuda area values; 0.13 and 0.74 μm3cm−3for FT and MBL. The large‐particle mode exhibits the least variations in volume distributions between the east coast and open‐sea Bermuda area, having a volume geometric median diameter (VGMD) between 1.4 and 1.6 μm and a geometric standard deviation between 1.57 and 1.68. For the giant‐particle mode, larger VGMD and volume concentrations were observed for marine aerosols nearshore off the east coast than in the open‐sea Bermuda area because of higher relative humidity and higher surface wind speed conditions. Wet VGMD and aerosol water volume concentrations at 15 m asl ship level were determined by extrapolating from those obtained by analysis of the CASE‐WATOX aircraft aerosol data. Abundance of aerosol water in the MBL serves as an important pathway for heterogeneous conversion

ISSN:0886-6236    

DOI:10.1029/GB004i002p00165

年代:1990

数据来源: WILEY

摘要:

During the 1988 Global Change Expedition/Coordinated Air‐Sea Experiment/Western Atlantic Ocean Experiment (GCE/CASE/WATOX) joint effort, research was conducted to determine elemental concentrations in atmospheric aerosol particles near Bermuda, to construct a three‐level (15, 150, and 2600 m ASL) vertical profile of these concentrations, and to ascertain the source of the particles. Samples were collected by the NOAA King Air aircraft and NOAA shipMt. Mitchellon July 24–28, 1988. Concentration determinations were made for 16 elements through the use of an X ray fluorescence instrument designed for analysis of small‐mass samples. A layering effect was found; concentrations of several elements at 150 m were more than twice their respective concentrations at 15 m and 2600 m. Enrichment factors, V/Mn ratio, and correlations between concentrations suggest a Saharan mineral source, despite air mass back trajectories that show no direct continental input for up to 10 days prior to sample collection. Estimated total mineral aerosol concentrations at 15 m, 150 m, and 2600 m are 1.5, 4.1, and 2.1

ISSN:0886-6236    

DOI:10.1029/GB004i002p00179

年代:1990

数据来源: WILEY

摘要:

We present results from the Global Change Expedition/ Coordinated Air‐Sea Experiment/Western Atlantic Ocean Experiment (GCE/CASE/WATOX) research cruise conducted from July to September 1988 in the North Atlantic Ocean aboard the NOAA shipMt. Mitchell. We examine the correlations between measurements of aerosol black carbon (BC, a tracer for combustion emissions), radon 222 (Rn, a tracer for natural emissions from land masses), and calculated isentropic back trajectories from the ship's position during two portions of the cruise that circled the North Atlantic Ocean. The results suggest four distinct categories of origin of the sampled air mass, with trajectories connecting back to different geographical areas: case A, trajectories from inhabited land, with the air mass containing strongly correlated BC and Rn; case B, trajectories from uninhabited (far northern) land, with Rn but little BC; case C, contaminated marine air, with little Rn but moderate BC, correlated with observations of combustion sources (other ships, etc.) in the vicinity; and case D, air masses of remote marine origin, with low BC and low Rn content. The requirements of the trajectory analyses lead to an improved understanding of the transport pathways across the ocean. We conclude that real‐time measurements of aerosol black carbon and radon, coupled with timely meteorological analyses, can be a powerful indicator of air mass origin both retrospectively and during the course of an experiment to assist in the scheduling of other measureme

ISSN:0886-6236    

DOI:10.1029/GB004i002p00189

年代:1990

数据来源: WILEY

摘要:

Measurements of tropospheric H2O2and O3concentrations were made over the Atlantic Ocean near the U.S. east coast (southeast of Newport News, Virginia) and near Bermuda during July 1988 with an instrumented aircraft. Oxidant concentrations were high (O3up to 100 parts per billion by volume (ppbv) and H2O2up to 2.5 ppbv) near the U.S. east coast at low altitude but decreased rapidly with increasing offshore distance to concentrations comparable to those measured near Bermuda. O3concentrations observed near Bermuda at low altitude were 14–22 ppbv, comparable to those reported for remote subtropical marine locations. O3concentrations increased with altitude (up to 2.6 km); high‐altitude concentrations were 30–80 ppbv. H2O2concentrations near Bermuda varied by a factor of 2, 0.7–1.5 ppbv, from day to day, but were nearly constant at all altitudes during individual flights. Because a high‐pressure system centered over the western Atlantic Ocean limited eastward advection of continental air toward Bermuda, these concentrations are assumed to be typical of mid‐latitude marine air du

ISSN:0886-6236    

DOI:10.1029/GB004i002p00201

年代:1990

数据来源: WILEY

摘要:

Ozone mixing ratios observed on a cruise from the east coast of North America to Bermuda, to Iceland, to the Azores and terminating in Barbados in a boreal summer exhibit wide variability. Increases above a North Atlantic background of 10–20 ppbv appear to be associated with transport from terrestrial systems. In the central gyre of the North Atlantic and in the tropical North Atlantic, ozone mixing ratios below 10 ppbv are commonly observed when the air being sampled does not have a recent (10 days) history of terrestrial input. Carbon monoxide mixing ratios within the boundary layer vary latitudinally from an average of 124 ppbv in the westerlies to 88 ppbv in the tropical North Atlantic. Variability in the distribution of CO appears to be dominated by transport from terrestrial source region

ISSN:0886-6236    

DOI:10.1029/GB004i002p00215

年代:1990

数据来源: WILEY