Formation of spring warm water southwest of the Philippine Islands: Winter monsoon wake effects

From satellite observations and the reanalysis data, the late spring formation of warm water with temperature higher than 30 °C to the southwest of the Philippine Islands (8–18°N, 115–120°E) is investigated. Our analysis suggests that the blockage of the winter monsoon by the Philippine Islands results in this “Luzon warm water” (LWW) to the southwest of the Luzon Island and the “Vietnam cold tongue” (VCT) to the southeast of the Vietnam coast during winter and early spring in the South China Sea (SCS). The VCT is formed by the southward cold advection by the western boundary current and surface heat loss in the SCS. During the winter monsoon, the LWW first forms due to weak winds southwest of the Philippine Islands and the countering effect of warm Ekman advection against cold geostrophic advection. In spring its temperature exceeds 30 °C (LWW30), helped by strong solar radiation and the winter monsoon wake effect lee of the Philippine Islands. With the winter monsoon weakening, LWW30 extends southwestward in late spring but disappears quickly after the summer monsoon onset. Reduced latent heat flux in the winter monsoon wake is the dominant factor for the spring fast warming southwest of the Philippine Islands.Both VCT and LWW persist from winter to early spring as the Philippine Islands block the winter monsoon. Their interannual variations are correlated with the variation of the LWW30 since the blockage of the winter monsoon by the Philippine Islands modifies surface latent heat flux and ocean advection from winter to early spring. These results strongly suggest that the LWW30 is a result of land–sea–winter monsoon interaction.     

Small-particle concentration fluctuations at a coastal site

Aerosol size spectra (d=10 nm–10 μm) were measured with an electrical aerosol spectrometer (EAS) at Mace Head on the west coast of Ireland. Several small aerosol particle (diameter 10–32 nm) concentration bursts were observed during the measurement period. Relationships between the events, air mass trajectories, tide height, and meteorological parameters are examined. Series of bursts were observed when a spectral transformation due to subsequent particle growth from 10 to 56–100 nm can be identified in an Eulerian experiment. Particle growth rates of between 1 and 3 nm/h were determined. These bursts appear in cold and comparatively clean arctic or polar air masses with temperature and relative humidity fluctuations, and do not correlate with low tide in some cases. These episodes, similar to those frequently found in the continental boundary layer, are thought to occur over a wide area and, for clear detection, require stable airflow for a few days. Elevated small-particle concentration events are more common during low tide or shortly after, and are typically associated with low wind speeds. Here, the increased shore exposure during low tide is thought to influence the nucleation and the subsequent growth of these aerosol particles. The occurrences of the bursts are found to depend on local wind direction. The highest d=10–32 nm particle concentrations appeared for wind sectors furthest from the tidal regions when the wind direction was 150–160°(south-easterly). Most of the events occurred during daytime when solar irradiation is most intense.     

The climate of the coast and fog zone in the Tarapacá Region, Atacama Desert, Chile

In the Atacama Desert, the narrow littoral plain and the adjacent mountain range have a unique climate. This area is locally called the “coastal desert with abundant cloudiness”, and extends from the coastline up to an elevation of 1000 m. The climate is designated as being BWn according to Köppen's Climate Classification as adapted for Chile. In the original classification the acronym (Bn) is used for foggy environments. Toward the east a “normal desert” climate (BW) is found. This is known as one of the most extreme deserts of the world. In the BWn areas there are meteorological differences between low and high elevation zones. The climate of the coastal plains and the mountains is described in this paper in order to show that there is an area where the climate differs from those classified as BWn and BW in the Chilean Climate Classification. This area is located between 650 and 1200 m a.s.l. and contains several fog oases or lomas vegetation, rich in biodiversity and endemism.The weather is warmer near sea level, with an annual average temperature of 18 °C. At high elevation sites like Alto Patache, the temperature decreases at a rate of 0.7 °C for every 100-m increase in altitude. The average annual minimum temperature often approaches 1 °C in winter, while the mean annual temperature range is significant (8.3 °C in Los Cóndores). The mean monthly relative humidity in Alto Patache is over 80%, except during the summer months. During autumn, winter and spring high elevation fog is present in the study area at altitudes ranging from 650 m up to 1060 m, giving annual water yields of 0.8 to 7 L m^− 2 day^− 1. If vegetation is used as an indicator, the foggy zone lies between 650 m a.s.l. and 1200 m a.s.l. About 70% of the mountain range experiences the foggy climate, as opposed to the coastal plains that are characterized by a cloudy climate.     

The evolution of Pinatubo aerosols in the Arctic stratosphere during 1994–2000

Balloon-borne aerosol measurements were performed with an optical particle counter between 1994 and 2000 at Ny-Ålesund (79°N), Svarbard. Throughout the observation period, continuous decay was found in the concentrations of particles with 0.4–0.6 μm in radius in the Arctic stratosphere, suggesting that Pinatubo aerosols remained even at the end of the 1990s. The decay rate was clearly higher for larger particle sizes, and higher at higher altitude (e-folding time of 970–526 days), suggesting a gravitational sedimentation effect. For smaller particles with R<0.4 μm, slight increases in concentration with time were found, which agreed with the measurements at mid-latitude. The sulfate mass mixing ratio in the Arctic stratosphere before 1998 showed values higher than those at middle latitude, while values were almost the same in both regions after 1998. A possible explanation of the latitudinal difference is a time lag (of 0.5–1 year) in the arrival of Pinatubo aerosols in the Arctic.     

The remarkable wide range spatial scaling of TRMM precipitation

The advent of space borne precipitation radar has opened up the possibility of studying the variability of global precipitation over huge ranges of scale while avoiding many of the calibration and sparse network problems which plague ground based rain gage and radar networks. We studied 1176 consecutive orbits of attenuation-corrected near surface reflectivity measurements from the TRMM satellite PR instrument. We find that for well-measured statistical moments (orders 0 < q < 2) corresponding to radar reflectivities with dBZ < 57 and probabilities > 10^− 6, that the residuals with respect to a pure scaling (power law) variability are remarkably low: ± 6.4% over the range 20,000 km down to 4.3 km. We argue that higher order moments are biased due to inadequately corrected attenuation effects. When a stochastic three — parameter universal multifractal cascade model is used to model both the reflectivity and the minimum detectable signal of the radar (which was about twice the mean), we find that we can explain the same statistics to within ± 4.6% over the same range. The effective outer scale of the variability was found to be 32,000 ± 2000 km. The fact that this is somewhat larger than the planetary scale (20,000 km) is a consequence of the residual variability of precipitation at the planetary scales. With the help of numerical simulations we were able to estimate the three fundamental parameters as α ≈ 1.5, C₁ = 0.63 ± 0.02 and H = 0.00 ± 0.01 (the multifractal index, the codimension of the mean and the nonconservation parameter respectively). There was no error estimate on α since although α = 1.5 was roughly the optimum value, this conclusion depended on assumptions about the instrument at both low and high reflectivities. The value H = 0 means that the reflectivity can be modeled as a pure multiplicative process, i.e. that the reflectivity is conserved from scale to scale. We show that by extending the model down to the inner “relaxation scale” where the turbulence and rain decouple (in light rain, typically about 40 cm), that even without an explicit threshold, the model gives quite reasonable predictions about the frequency of occurrence of perceptible precipitation rates.While our basic findings (the scaling, outer scale) are almost exactly as predicted twenty years ago on the basis on ground based radar and the theory of anisotropic (stratified) cascades, they are incompatible with classical turbulence approaches which require at least two isotropic turbulence regimes separated by a meso-scale “gap”. They are also incompatible with classical meteorological phenomenology which identifies morphology with mechanism and breaks up the observed range 4 km–20 000 km into several subranges each dominated by different mechanisms. Finally, since the model specifies the variability over huge ranges, it shows promise for resolving long standing problems in rain measurement from both (typically sparse) rain gage networks and radars.     

Aerosol radiative properties in the semiarid Western United States

Characterization of aerosol optical properties, such as aerosol optical depth, Angstrom exponent, and volume size distribution at the semiarid site of Tombstone Arizona (31°23′N, 110°05′W, 1408 m) will be presented for one annual cycle. In this region, extensive observations of selected optical parameters such as aerosol optical depth (AOD) have been made in the past and reported on in the literature. Less is known about other optical characteristics that are important in climate modeling and remote sensing. New observational techniques and inversion methods allow for the expansion of the earlier information. Observations have been taken with a state of the art sun photometer for a 1-year period and their analysis will be presented here. Monthly mean AODs at 500 nm were found to be in the range of 0.03–0.12; the monthly mean Angstrom exponent ranged from 0.9 to 1.6, being higher in spring and summer and lower in late fall and winter. Volume size distributions exhibit clear dominance of smaller particles, with a gradual increase in size from winter to spring and into summer. Annual variation of the radii of the smaller and the larger particles ranged between 0.05–0.4 and 4–8 μm, respectively. Radiance measurements at 940 nm were used to estimate precipitable water. The retrieved values compared within limits of uncertainty with independently derived estimates from the National Center for Environmental Prediction (NCEP) regional weather forecast model. An interesting outcome from this study was the consistency found in aerosol optical depths as observed in this study and those derived about two decades ago.     

One year measurements of aerosol optical properties over an urban coastal site: Effect on local direct radiative forcing

We present results of direct aerosol radiative forcing over a French Mediterranean coastal zone based on one year of continuous observations of aerosol optical properties during 2005–2006. Monthly-mean aerosol optical depth at 440 nm ranged between 0.1 and 0.34, with high Angstrom coefficient (α > 1.2). The single scattering albedo (at 525 nm) estimated at the surface ranged between 0.7 and 0.8, indicating significant absorption. The presence of aerosols over the Mediterranean zone during summer decreases the shortwave radiation reaching the surface by as much as 26 ± 3.9 W m^− 2, and increases the top of the atmosphere reflected radiation by as much as 5.2 ± 1.0 W m^− 2. The shortwave atmospheric absorption translates to an atmospheric heating of 2.5 to 4.6 K day^− 1. Concerted efforts are needed for investigating the possible impact of the increase in heating rate on the maintenance of heat-waves frequently occurring over this coastal region during summer time.     

Carbonaceous materials in size-segregated atmospheric aerosols from urban and coastal-rural areas at the Western European Coast

A high-volume cascade impactor, equipped with a PM10 inlet, was used to collect size-segregated aerosol samples during the summer of 2004 at two Portuguese locations: a coastal-rural area (Moitinhos) and an urban area (Oporto). Concentrations of airborne particulate matter (PM), total carbon (TC), organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) were determined for the following particle size ranges: < 0.49, 0.49–0.95, 0.95–3.0, and 3.0–10 µm. The total PM mass concentrations at the urban and coastal-rural sites ranged from 22.8 to 79.6 μg m^− 3 and 19.9 to 28.2 μg m^− 3, respectively, and more than 56% of the total aerosol mass was found in the fractions below 3.0 μm. At both locations the highest concentrations of OC and EC were found in the submicrometer size range. The regional variability for the OC and EC concentrations, with the highest concentrations being found in the urban area, was related to the contribution of local primary sources (mostly traffic emissions). It was also verified an enrichment of the small size particles in WSOC, representing on average 37.3(± 12.4)% and 59.7(± 18.0)% of OC in the very fine aerosol at the coastal-rural and urban areas, respectively. The amount of secondary OC calculated by the minimum OC/EC ratio method indicates that secondary organic aerosol formation was important throughout the study at both sites. The obtained results suggest that long-range transport and favourable summer conditions for photochemical oxidation are key factors determining secondary OC formation in the coastal-rural and urban areas. The ultraviolet absorption properties of the chromophoric constituents of the WSOC fractions were also different among the different particle size ranges and also between the two sampling locations, thus suggesting the strong impact of the diverse emission sources into the composition of the size-segregated organic aerosol.     

Condensed water in tropical cyclone “Oliver”, 8 February 1993

On February 8, 1993, the NASA DC-8 aircraft profiled from 10,000 to 37,000 feet (3.1–11.3 km) pressure altitude in a stratified section of tropical cyclone “Oliver” over the Coral Sea northeast of Australia. Size, shape and phase of cloud and precipitation particles were measured with a 2-D Greyscale probe. Cloud/ precipitation particles changed from liquid to ice as soon as the freezing level was reached near 17,000 feet (5.2 km) pressure altitude. The cloud was completely glaciated at −5°C. There was no correlation between ice particle habit and ambient temperature. In the liquid phase, the precipitation-cloud drop concentration was 4.0 × 10³ m⁻³, the geometric mean diameter D_g=0.5−0.7 mm, and the liquid water content 0.7−1.9 g m⁻³. The largest particles anywhere in the cloud, dominated by fused dendrites at concentrations similar to that of raindrops (2.5 × 10³ m⁻³) but a higher condensed water content (5.4 g m⁻³ estimated) were found in the mixed phase; condensed water is removed very effectively from the mixed layer due to high settling velocities of the large mixed particles. The highest number concentration (4.9 × 10⁴ m⁻³), smallest size (D_g=0.3−0.4 mm), largest surface area (up to 2.6 × 10² cm² m⁻³ at 0.4−1.0 g m⁻³ of condensate) existed in the ice phase at the coldest temperature (−40°C) at 35,000 feet (10.7 km). Each cloud contained aerosol (haze particles) in addition to cloud particles. The aerosol total surface area exceeded that of the cirrus particles at the coldest temperature. Thus, aerosols must play a significant role in the upscattering of solar radiation. Light extinction (6.2 km⁻¹) and backscatter (0.8 sr⁻¹ km⁻¹) was highest in the coldest portion of the cirrus cloud at the highest altitude.     

Atmospheric nuclei in the remote free-troposphere

During May-June of 1990 an extensive flight series to survey aerosol present in the upper-troposphere was undertaken aboard the NASA DC-8 as part of the CLObal Backscatter Experiment (GLOBE). About 50,000 km were characterized between 8–12 km altitude and between 70°N and 58°S. Aerosol with diameters greater than 3nm were counted and sized with a combination of condensation nuclei counters and optical particle counters. Aerosol number and mass concentrations were separately identified with regard to both refractory and volatile components. Regions of the free-troposphere with the lowest mass concentrations were generally found to have the highest number concentrations and appeared to be effective regions for new particle production. These new particle concentrations appear inversely related to available aerosol surface area and their volatility suggests a sulfuric acid composition. The long lifetime of these new particles aloft can result in their growth to sizes effective as CN and CCN that can be mixed throughout the troposphere.     

An improved Lorentzian technique for evaluating resonance characteristics of the Earth-ionosphere cavity

The effectiveness of various formulations of the Lorentzian procedure for estimating Schumann resonance (SR) characteristics of the Earth-ionosphere waveguide from transient electromagnetic signals is tested in the limits of a simplified, spherically uniform model of the resonator. It is shown that the major improvement, in comparison with the “classic” Lorentzian formulation, is achieved by consideration of the intra-modal phase interference. The effect of the “limited frequency dispersion” inherent in the “classic” Lorentzian approach – that is of substantial importance at the lowest SR modes – can be effectively neutralized by interpolating the values for the propagation parameter between the adjacent modal frequencies. Several practical aspects of applying the Lorentzian procedure to transient signals are also discussed.     

Comment on “Glory phenomenon informs of presence and phase state of liquid water in cold clouds” by Anatoly N. Nevzorov

In a recent publication “Glory phenomenon informs of presence and phase state of liquid water in cold clouds” Nevzorov [Nevzorov, A., 2006. Glory phenomenon informs of presence and phase state of liquid water in cold clouds. Atmospheric Research 82, 367–378] claims that “the convincing evidence has been provided that this sort of glory forms as a first-order bow from spherical particles with a refractive index of 1.81–1.82 and diameter over 20 μm”. This is a highly unusual finding because the refractive index of liquid water and ice is between 1.30 and 1.35 in the visible spectral range. The author concludes that “once more corroboration is gained […] of droplets of liquid water in specific phase state referred to amorphous water, or A-water”. Here we show that the phenomena described by the author are easily explained assuming liquid water with a refractive index of 1.33 and a realistic droplet size distribution with an effective radius of around 10 μm. We conclude that this type of observations does not corroborate the existence of amorphous water in the atmosphere. In a recent publication we showed how to quantitatively derive cloud optical thickness, effective droplet radius, and even the width of the size distribution from observations of the glory [Mayer, B., Schröder, M., Preusker, R., Schüller, L., 2004. Remote sensing of water cloud droplet size distributions using the backscatter glory: a case study. Atmospheric Chemistry and Physics 4, 1255–1263].     

Scavenging of atmospheric ions and aerosols by drifting snow in Antarctica

Measurements of the small-, intermediate-, and large-ion concentrations and the air–earth current density along with simultaneous measurements of the concentration and size distribution of aerosol particles in the size ranges 4.4–163 nm and 0.5–20 μm diameter are reported for a drifting snow period after the occurrence of a blizzard at a coastal station, Maitri, Antarctica. Ion concentrations of all categories and the air–earth current simultaneously decrease by approximately an order of magnitude as the wind speed increases from 5 to 10 ms^− 1. The rate of decrease is the highest for large ions, lowest for small ions and in-between the two for intermediate ions. Total aerosol number concentration decreases in the 4.4–163 nm size range but increases in the 0.5–20 μm size range with wind speed. The size distribution of the nanometer particles shows a dominant maximum at ~ 30 nm diameter throughout the period of observations and the height of the maximum decreases with wind speed. However, larger particles show a maximum at ~ 0.7 μm diameter but the height of the maximum increases with increasing wind speed. The results are explained in terms of scavenging of atmospheric ions and aerosols by the drifting snow particles.     

Influence of the total atmospheric optical depth and cloud cover on solar irradiance components

Broadband solar irradiance data obtained in the spectral range 400–940 nm at Kwangju, South Korea from 1999–2000 have been analyzed to investigate the effects of cloud cover and atmospheric optical depth on solar radiation components. Results from measurements indicate that the percentage of direct and diffuse horizontal components of solar irradiance depend largely on total optical depth (TOD) and cloud cover. During summer and spring, the percentages of diffuse solar irradiance relative to the global irradiance were 5.0% and 4.9% as compared to 2.2% and 3.0% during winter and autumn. The diffuse solar irradiance is higher than the direct in spring and summer by 24.2%, and 40.6%, respectively, which may largely be attributed to the attenuation (scattering) of radiation by heavy dust pollution and large cloud amount. In cloud-free conditions with cloud cover ≤2/10, the fraction of the direct and diffuse components were 66.0% and 34.0%, respectively, with a mean daily global irradiance value of 7.92±2.91 MJ m⁻² day⁻¹. However, under cloudy conditions (with cloud cover ≥8/10), the diffuse and direct fractions were 97.9% and 2.2% of the global component, respectively. The annual mean TOD under cloudless conditions (cloud cover≤2/10) yields 0.74±0.33 and increased to as much as 3.15±0.67 under cloudy conditions with cloud amount ≥8/10. An empirical formula is derived for estimating the diffuse and direct components of horizontal solar irradiance by considering the total atmospheric optical depth (TOD). Results from statistical models are shown for the estimation of solar irradiance components as a function of TOD with sufficient accuracy as indicated by low standard error for each solar zenith angle (SZA).     

Observational study of surface ozone at an urban site in East China

In this study, we present the observational data of near surface ozone and some meteorological parameters during 2004, at an urban site (36°42′ N, 117°08′ E, 34.5 m a.s.l.) of Jinan, China. Hourly ozone concentrations exceeding the standard value of China, 100 ppbv, were observed for 65 h (in 23 days) from April to October, and values exceeding US NAAQS (National Ambient Air Quality Standard) for 1 h ozone, 120 ppbv, were observed for 15 h (in 7 days) from late May to early July. Ozone formation presented the phenomenon of “weekend effect”, especially in summer. Monthly variation of ozone coincided with temperature except for July and August. The low ozone levels in July and August may be due to the short sunshine duration and much rainfall during this period. Among these meteorological parameters, daily averaged ozone shows a significant correlation with temperature (r = 0.66) in the year and with relative humidity (r = − 0.75) in summer. Throughout the year, high ozone concentrations were mainly associated with the wind from 180 to 247.5°, while high ozone concentration seemed to have no obvious correlation with a given wind direction in summer. An anomalous nocturnal high ozone episode during 23–25 May 2004 was investigated. Growth fractions of ozone during the nighttime episode were 62.2% and 71.1% for 23 and 24 May, respectively. Synoptic analysis shows that favorable synoptic condition had presumably elevated the background ozone level in this region. Backward trajectory analysis shows that the increase of ozone concentration and the relatively constant high ozone concentrations during the night of May 23 might originate from the transport of ozone rich air mass above boundary layer. Transport of ozone from Yangtze Delta and East Central China might be a significant process for the high ozone level during night May 24 at Jinan.     

Seasonal surface ocean circulation and dynamics in the Philippine Archipelago region during 2004–2008

The dynamics of the seasonal surface circulation in the Philippine Archipelago (117°E–128°E, 0°N–14°N) are investigated using a high-resolution configuration of the Regional Ocean Modeling System (ROMS) for the period of January 2004–March 2008. Three experiments were performed to estimate the relative importance of local, remote and tidal forcing. On the annual mean, the circulation in the Sulu Sea shows inflow from the South China Sea at the Mindoro and Balabac Straits, outflow into the Sulawesi Sea at the Sibutu Passage, and cyclonic circulation in the southern basin. A strong jet with a maximum speed exceeding 100 cm s⁻¹ forms in the northeast Sulu Sea where currents from the Mindoro and Tablas Straits converge. Within the Archipelago, strong westward currents in the Bohol Sea carry the surface water of the western Pacific (WP) from the Surigao Strait into the Sulu Sea via the Dipolog Strait. In the Sibuyan Sea, currents flow westward, which carry the surface water from the WP near the San Bernardino Strait into the Sulu Sea via the Tablas Strait.These surface currents exhibit strong variations or reversals from winter to summer. The cyclonic (anticyclonic) circulation during winter (summer) in the Sulu Sea and seasonally reversing currents within the Archipelago region during the peak of the winter (summer) monsoon result mainly from local wind forcing, while remote forcing dominates the current variations at the Mindoro Strait, western Sulu Sea and Sibutu passage before the monsoons reach their peaks. The temporal variations (with the mean removed), also referred to as anomalies, of volume transports in the upper 40 m at eight major Straits are caused predominantly by remote forcing, although local forcing can be large during sometime of a year. For example, at the Mindoro Strait, the correlation between the time series of transport anomalies due to total forcing (local, remote and tides) and that due only to the remote forcing is 0.81 above 95% significance, comparing to the correlation of 0.64 between the total and local forcing. Similarly, at the Sibutu Passage, the correlation is 0.96 for total versus remote effects, comparing to 0.53 for total versus local forcing. The standard deviations of transports from the total, remote and local effects are 0.59 Sv, 0.50 Sv, and 0.36 Sv, respectively, at the Mindoro Strait; and 1.21 Sv, 1.13 Sv, and 0.59 Sv at the Sibutu Passage. Nonlinear rectification of tides reduces the mean westward transports at the Surigao, San Bernardino and Dipolog Straits, and it also has non-negligible influence on the seasonal circulation in the Sulu Sea.     

Seasonal variation of particulate polycyclic aromatic hydrocarbons associated with PM10 in Guangzhou, China

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in the urban atmosphere. An investigation on seasonal variation of PAHs in the urban atmosphere of Guangzhou, China was conducted in this study. 112 PM10 (particulate matter with aerodynamic diameter < 10 μm) samples were collected at two sites between June 2002 and June 2003. PAHs were analyzed with GC–MS (gas chromatography–mass spectrometry). The result showed that PAHs exhibit distinct seasonal variation. The seasonal concentration for the ∑PAHs ranged from 8.11 to 106.26 ng m^− 3. The average ∑PAHs measured were highest in winter and lowest in summer. The PAHs distribution patterns were similar within each season at two sites. 5–6 ring PAHs were the abundant compounds, which accounted for 65–90% of ∑PAHs and benzo [b + k] fluoranthene dominated in four seasons. The PAHs concentration and distribution pattern fluctuated greatly in winter for the cold air current. Based on the different temperature in winter, the samples were split into two groups. PM10 and the abundance of the PAHs in winter-1 (temperature, 12–22 °C) were much greater than in winter-2 (temperature, 8–12 °C). In winter-1 benzo [b + k] fluoranthene and Indeno [1, 2, 3] pyrene dominated while chrysene and benzo [b + k] fluoranthene dominated in winter-2. Meteorological conditions such as wind speed and temperature had a strong influence on the seasonal variation. Potential sources of PAHs were identified using the molecular diagnostic ratios between PAHs. Results showed fossil fuel combustion may be the major source of PAHs at the two sites.     

Resources of the ionized atmosphere as an aerosol source

The potential resources on the ion-stimulated syntheses effects of aerosol particles of lower troposphere in test sites in the arctic, mountain, arid and forest areas as the function of irradiation time and gas-precursor concentration were experimentally and theoretically evaluated. The dust-free outdoor air was irradiated with an ionization current of 10^− 6 A by α-rays from isotope ²³⁹Pu. The total output of radiolytic aerosols (RA) with a diameter of 3–1000 nm was found to be 0.05–0.1 molecules per 1 eV of absorbed radiation, while the physical upper limit is 0.25–0.4 molecules/eV. In an interval of exposition time from 6 to 800 s (adsorbed energy is 3 · 10¹²–10¹⁴ eV/cm³) the RA mass concentration at different sites was increased from 1–10 to 50–500 μg/m³. According to the liquid chromatography data the major RA material is the H₂O/HNO₃ solution with acid concentration  25%. The used physical model presents new aerosols as a product from small and intermediate ion association through formation of neutral clusters and describes adequately some of the peculiarities in field experiment data. Introducing SO₂, NH₃, and also hydrochloric, nitric and sulphuric acid vapours with concentration 0.1–1 mg/m³ in the irradiated air stimulated an increase of mass aerosol concentration by a factor of 8–30. The mean size also decreased by a factor of 3–5. These facts allowed us to expect that the chemical composition of radiolytic aerosols generated in outdoor air would noticeably differ after addition of the gas-precursors.     

Aerosol over the Southern Ocean

In a first attempt to assess a proposed climatic change feedback process involving cloud condensation nuclei (CCN) and cloud albedo, CCN concentrations N as a function of supersaturation S were measured on a voyage from latitude 43 to 65°S in October–November 1988. The usual relationship N=CS^k, with k=0.5 and C a constant was a fair apprraximation for S in the range 0.3–0.7% implying that CCN concentrations should largely determine cloud drop concentrations and hence albedo for clouds with S in that range. South of latitude 50°S and at smaller S,k was 1 or larger on average, which would lead to reduced dependence of albedo on CCN for the relevant clouds. N varied very widely for separations of the order of 100 km or 6 hours in time, particularly when the sea was partly ice-covered, suggesting strong local influences. During a large increase in N 60°S, unaccompanied by an increase in condensation nuclei (CN), cloud drops grew more rapidly than usual. In a subsidiary experiment particles were collected and examined by transmission electron microscopy. For particles less than 0.2 μm diameter, 80–90% appeared to consist of ammonium sulfate, the remainder being sea salt or an unknown substance which was more liquid and heat-resistant. Dialysis showed that the sulfate particles contained a few percent of insoluble material. Particles which formed cloud drops in vapours other water, were also studied. Comparison of these and water CCN and the rates of droplet suggested that the water insoluble portion of the particles was ethanol-soluble and surface-active. CN concentrations decreased by a factor of about 2 between 43 and 65°S, a change closely paralleled by ethanol CCN concentrations.     

The Kuroshio Current System as a jet and twin “relative” recirculation gyres embedded in the Sverdrup circulation

By analyzing the results of a realistic ocean general circulation model (OGCM) and conducting a series of idealized OGCM experiments, the dynamics of the Kuroshio Current System is examined. In the realistic configuration, the Kuroshio Current System is successfully simulated when the horizontal resolution of OGCMs is increased from 1/2° to 1/10°. The difference between the two experiments shows a jet, the model’s Kuroshio Extension, and a pair of cyclonic and anticyclonic, “relative,” recirculation gyres (RRGs) on the northern and southern flanks of the jet. We call them recirculation gyres because they share some features with ordinary recirculation gyres in previous studies, and we add the adjective “relative” to emphasize that they may not be apparent in the total field. Similar zonal jet and RRGs are obtained also in the idealized model with a rectangular basin and a flat bottom with a horizontal resolution of 1/6°. The northern RRG is generated by the injection of high potential vorticity (PV) created in the viscous sublayer of the western boundary current, indicating the importance of a no-slip boundary condition. Since there is no streamline with such high PV in the Sverdrup interior, the eastward current in the northern RRG region has to lose its PV anomaly by viscosity before connecting to the interior. In the setup stage this injection of high PV is carried out by many eddies generated from the instability of the western boundary current. This high PV generates the northern RRG, which induces the separation of the western boundary current and the formation of the zonal jet. In the equilibrium state, the anomalous high PV values created in the viscous sublayer are carried eastward in the northern flank of the zonal jet. The southern RRG is due to the classical Rhines–Young mechanism, where low PV values are advected northward within the western boundary inertial sublayer, and closed, PV-conserving streamlines form to the south of the Kuroshio Extension, allowing slow homogenization of the low PV anomalies. The westward-flowing southern branch of this southern RRG stabilizes the inertial western boundary current and prevents its separation in the northern half of the Sverdrup subtropical gyre, where the western boundary current is unstable without the stabilizing effect of the southern RRG. Therefore, in the equilibrium state, the southern RRG should be located just to the north of the center of the Sverdrup subtropical gyre, which is defined as the latitude of the Sverdrup streamfunction maximum. The zonal jet (the Kuroshio Extension) and the northern RRG gyre are formed to the north of the southern RRG. This is our central result. This hypothesis is confirmed by a series of sensitivity experiments where the location of the center of the Sverdrup subtropical gyre is changed without changing the boundaries of the subtropical gyre. The locations of the zonal jets in the observed Kuroshio Current System and Gulf Stream are consistent as well. Sensitivities of the model Kuroshio Current System are also discussed with regard to the horizontal viscosity, strength of the wind stress, and coastline.