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During an upwelling event the cold bottom-water is brought to the sea surface. This cools the atmosphere from below and the stratification becomes more stable. When the atmosphere is more stable the turbulence is reduced and, as a consequence, so are the turbulent fluxes. This study is investigating four periods of upwelling from the Östergarnsholm-site, in the Baltic Sea east of Gotland, during the summer of 2005. The air measurements are taken at a tower at the southernmost tip of Östergarnsholm while the measurements in the water are from a buoy moored 1 km south-southeast of the tower. During all the upwelling events the wind is south-westerly, along the coast of Gotland. This means that the buoy is not within the flux footprint area and is perhaps not always representative of what happens there. All the periods show a stabilization of the atmosphere as the SST (Sea Surface Temperature) decreases. The heat fluxes, especially the latent heat flux, decreases as the SST decreases. The amount of CO2 in the atmosphere, in the summer, is usually higher than the amount in the surface water of the seas because the oceans are a net sink of CO2. The air-sea flux of CO2 is to a large extent controlled by this difference. Therefore the flux of CO2 is usually directed to the sea. The deep-water contains more CO2 than the surface water because the phytoplankton near the surface removes CO2 through photosynthesis. The deep-water is also colder and can solve more CO2. During an upwelling event this CO2-rich water is brought to the surface. As an upwelling event progresses the difference in CO2-concentration between the air and the sea is reduced, sometimes reversed, and the flux decreases. This is what happens in three of the investigated periods in this study. During the fourth period a counter gradient flux is observed. / När en uppvällning inträffar förs kallt djupvatten upp till havsytan. Det kalla vattnet kyler atmosfären nedifrån, något som leder till mer stabil skiktning. När atmosfären blir mer stabilt skiktad dämpas turbulensen och det medför att de turbulenta flödena också avtar. I den här studien analyseras fyra perioder med uppvällning. Mätningarna kommer från Östergarnsholm, öster om Gotland, under sommaren 2005. Mätningarna i luften är tagna från en mast vid Östergarnsholms södra udde. Mätningarna i vattnet kommer från en boj som är förankrad 1 km sydsydöst om masten. Vid samtliga uppvällnings-perioder i den här studien är vinden sydvästlig (längs Gotlandskusten). Det betyder att bojen inte befinner sig inom flödenas footprint-area och dess mätningar är kanske inte hela tiden representativa för vad som händer i footprint-arean. Samtliga undersökta perioder visar på en stabilisering av atmosfären då havsytans temperatur avtar. Värmeflödena, i synnerhet det latenta värmeflödet, avtar i samband med att temperaturen i havsytan sjunker. Halten av CO2 i atmosfären är vanligtvis högre än halten i havens ytvatten (under sommaren) eftersom de är en nettosänka för CO2 globalt sett. CO2-flödet mellan havsytan och atmosfären styr till en stor del av denna skillnaden i CO2-halt. Det innebär att CO2-flödet är riktat neråt, mot havet. Havens djupvatten innehåller mer CO2 därför att växtplankton nära ytan reducerar CO2-halten genom fotosyntesen. Djupvattnet är också kallare och kan därför lösa mer CO2. Under en uppvällning förs detta CO2-rika vatten upp till ytan. När en uppvällning fortskrider minskar skillnaden i CO2-halt mellan hav och atmosfär (ibland kan CO2-halten i ytvattnet även komma att överstiga atmosfärens halt) och flödet avtar. Tre av perioderna i den här studien visar på ett avtagande flöde. Den fjärde perioden uppvisar ett flöde motriktat CO2-gradienten.

The turbulence structure over the sea was studied with the emphasis on humidity. The data sets used came from the island of Östergarnsholm outside Gotland in the Baltic Sea. The study included spectral and quadrant analyses of the wind, temperature and humidity parameters from one measuring level. The wave state of the sea was deduced from data from a wave rider buoy anchored 4 km from the site.Two turbulence instruments for humidity were compared, the MIUU instrument (hot wire) and an open pass infrared gas analyser from LI-COR. The comparison showed that the LI-COR instrument resolved the high frequency fluctuations of the humidity better. The unstable cospectra of the sensible and latent heat fluxes were studied and categorised. It was found that many cospectra have two or more maxima. The higher frequency maxima gained influence when the stratification became near neutral.The quadrant analyses showed that the structures of humidity flux were similar to those of the heat flux. The sources of the flux were studied using different ratios. The ratio between events of moist updrafts and dry downdrafts were extensively studied. It was shown that the events of moist updrafts were more dominating during swell than during growing sea. When the results of the spectral and quadrant analyses were combined, it was shown that the smaller sized eddies of heat dominate the events of warm updrafts and that the large eddies dominate the cold downdrafts. The bulk transfer number for moisture, the Dalton number (CE), was found to be almost constant with stratification for unstable runs. The mean value was calculated to (1.0±0.3)·10-3. / Målet för denna studie var turbulensstrukturer över hav med särskild tonvikt på fuktigheten. I denna studie har använts observationer från en mast på ön Östergarns-holm, strax öster om Gotland. Arbetet innefattar spektral- och kvadrantanalys av vind, temperatur och fuktighet från en mätnivå. Havets aktuella tillstånd mättes med en vågboj förtöjd 4 km från masten. Två turbulensinstrument för fuktighet jämfördes, MIUU-instrumentet (varmtråds-instrument) och ett instrument från företaget LI-COR som mäter infraröd absorption. Jämförelsen visade att LI-COR-instrumentet löser upp de högfrekventa fuktighets-fluktuationerna bättre. Instabila cospektra för sensibelt och latent värmeflöde studerades och kategoriserades. Det visade sig att många cospektra hade två eller flera maxima. Det högfrekventa maximumet fick ökad betydelse när skiktningen blev nära neutral. Kvadrantanalyserna visade att strukturerna för värme- och fuktighetsflödet är liknande. Källan för flödena studerades med hjälp av olika kvoter. Av särskilt intresse var kvoten mellan tillfällen med fuktiga uppvindar och torra nedvindar. Det visade sig att tillfällen med fuktiga uppvindar var mer dominerande vid dyning än vid upp-byggande vågor. När resultaten från spektral- och kvadrantanalysen kombinerades, visade det sig att de små virvlarna med värme dominerar vid tillfällen med varma uppvindar och att de stora virvlarna dominerar vid kalla nedvindar. Utbyteskoefficienten CE för fuktighet, även kallad Dalton-talet, är nästan konstant för de instabila fallen. Medelvärdet av CE beräknades till (1,0±0,3)·10-3.

The marine boundary layer (MBL) is the region where energy, momentum and masses are exchanged between the ocean surface and the free troposphere. The lack of observations with high vertical resolution over the ocean significantly restricts the understanding of the complex physical processes that occur inside the MBL. The relatively short vertical extent of the MBL (average about 1~2 km) and the frequent cloudiness at its top make probing the MBL extremely difficult from the space. Several features of the Global Positioning System (GPS) radio occultation (RO) technique suggest that it has a great potential for sensing the MBL. These features include global coverage, high vertical resolution, and the ability of GPS signals to penetrate clouds.Over moist marine areas, a large negative moisture gradient often exists across the thermal inversion capping the MBL, which can cause super-refraction (SR) or ducting. A large number of high-resolution soundings have shown that SR occurs about 90% of the time in a year over the subtropical and tropical oceans and even 50% at high-latitudes during the summer. In the presence of SR, the reconstruction of refractivity from RO data becomes an ill-posed inverse problem, i.e., a given RO bending angle profile is consistent with a continuum (an infinite number) of refractivity profiles. The standard Abel retrieval gives the minimum refractivity solution of the continuum and thus produces the largest negative bias, consistent with a negative bias that is often present in the retrieved refractivity profiles in the moist lower troposphere. Simulation studies indicate a large variation of the negative refractivity biases (could be over -15%). The impact of diffraction effects and the open-loop receiver tracking on the bending angle and refractivity retrievals are assessed. A novel approach is developed and tested to reconstruct the vertical refractivity structure within and below the SR layer, which yields a much-improved retrieval, especially below the SR layer (less than 0.5% error). Such a reconstruction method should greatly enhance our ability to measure the MBL globally using the GPS RO technique as well as to improve the MBL parameterizations used in weather and climate models.

Glancing angle laser induced fluorescence was used to monitor the kinetics of the photodegradation of chlorophyll at the surface of various salt solutions. The loss was measured using varying wavelengths of actinic radiation in the presence and absence of gas phase ozone. The loss rate of illuminated chlorophyll was faster on salt water surfaces than fresh water surfaces, both in the presence and absence of ozone. On salt water surfaces, the dependence of the loss rate on [O3(g)] was different under illuminated conditions than in the dark. This was further investigated by measuring the excitation spectra and the dependence of chlorophyll loss on the concentration of salts at the salt water surface. The possible production of reactive halogen atoms is the likely reason for the observed enhancement. The following results provide evidence of photosensitized oxidation of halogen anions, in the UV-visible range of the spectrum, resulting in halogen atom release.

Glancing angle laser induced fluorescence was used to monitor the kinetics of the photodegradation of chlorophyll at the surface of various salt solutions. The loss was measured using varying wavelengths of actinic radiation in the presence and absence of gas phase ozone. The loss rate of illuminated chlorophyll was faster on salt water surfaces than fresh water surfaces, both in the presence and absence of ozone. On salt water surfaces, the dependence of the loss rate on [O3(g)] was different under illuminated conditions than in the dark. This was further investigated by measuring the excitation spectra and the dependence of chlorophyll loss on the concentration of salts at the salt water surface. The possible production of reactive halogen atoms is the likely reason for the observed enhancement. The following results provide evidence of photosensitized oxidation of halogen anions, in the UV-visible range of the spectrum, resulting in halogen atom release.

Airborne aerosols are crucial atmospheric constituents that are involved in global climate change and human life qualities. Understanding the nature and magnitude of aerosol-cloud-precipitation interactions is critical in model predictions for atmospheric radiation budget and the water cycle. The interactions depend on a variety of factors including aerosol physicochemical complexity, cloud types, meteorological and thermodynamic regimes and data processing techniques. This PhD work is an effort to quantify the relationships among aerosol, clouds, and precipitation on both global and regional scales by using satellite retrievals and aircraft measurements. The first study examines spatial distributions of conversion rate of cloud water to rainwater in warm maritime clouds over the globe by using NASA A-Train satellite data. This study compares the time scale of the onset of precipitation with different aerosol categories defined by values of aerosol optical depth, fine mode fraction, and Ångstrom Exponent. The results indicate that conversion time scales are actually quite sensitive to lower tropospheric static stability (LTSS) and cloud liquid water path (LWP), in addition to aerosol type. Analysis shows that tropical Pacific Ocean is dominated by the highest average conversion rate while subtropical warm cloud regions (far northeastern Pacific Ocean, far southeastern Pacific Ocean, Western Africa coastal area) exhibit the opposite result. Conversion times are mostly shorter for lower LTSS regimes. When LTSS condition is fixed, higher conversion rates coincide with higher LWP and lower aerosol index categories. After a general global view of physical property quantifications, the rest of the presented PhD studies is focused on regional airborne observations, especially bulk cloud water chemistry and aerosol aqueous-phase reactions during the summertime off the California coast. Local air mass origins are categorized into three distinct types (ocean, ships, and land) with their influences on cloud water composition examined and implications of wet deposition discussed. Chemical analysis of cloud water samples indicates a wide pH range between 2.92 and 7.58, with an average as 4.46. The highest pH values were observed north of San Francisco, coincident with the strongest land mass influence (e.g. Si, B, and Cs). Conversely, the lowest pH values were observed south of San Francisco where there is heavy ship traffic, resulting in the highest concentrations of sulfate, nitrate, V, Fe, Al, P, Cd, Ti, Sb, P, and Mn. The acidic cloud environment with influences from various air mass types can affect the California coastal aquatic ecosystem since it can promote the conversion of micronutrients to more soluble forms. Beyond characterization of how regional air mass sources affect cloud water composition, aircraft cloud water collection provides precious information on tracking cloud processing with specific species such as oxalic acid, which is the most abundant dicarboxylic acid in tropospheric aerosols. Particular attention is given to explore relationship between detected metals with oxalate aqueous-phase production mechanisms. A number of case flights show that oxalate concentrations drop by nearly an order of magnitude relative to samples in the same vicinity with similar environmental and cloud physical conditions. Such a unique feature was consistent with an inverse relationship between oxalate and Fe. In order to examine the hypothesis that oxalate decreasing is potentially related to existing of Fe, chemistry box model simulations were conducted. The prediction results show that the loss of oxalate due to the photolysis of iron oxalato complexes is likely a significant oxalate sink in the study region due to the ubiquity of oxalate precursors, clouds, and metal emissions from ships, the ocean, and continental sources.

Measurements of turbulent fluxes (momentum, sensible heat, latent heat and CO2) at two different heights were studied from data of a tower at Ostergarnsholm Island (Baltic Sea) during one week, while calculations using bulk formulations of fluxes were done with measurements in the tower and in two buoys moored at different locations. Different behaviors are found for the different fluxes. Measured latent heat flux shows higher correlation with calculations than measured sensible heat flux. For the CO2 flux, this relation was not found. Also all measured fluxes at the tower agree better with calculations when they are done under unstable conditions, meaning that the tower is better measuring the area where the measurements are taken in the buoys (near the tower). The studied period includes an upwelling and a high horizontal surface heterogeneity was found during most of the periods. It was seen using the comparison between calculated and measured fluxes and also using satellite images of the studied site. The footprint area is the area at some distance upwind from the tower where the surface conditions are influencing the measurements of the flux of some quantity at certain height in the tower, and this footprint area is continuously changing because its highly dependence with the stratification. Since during all the period the stratification was changing from slightly stable to slightly unstable conditions, the surface heterogeneity can also be seen in the variability of measured fluxes at different heights. One important conclusion in the study is that calculations of the fluxes using bulk formulations may not be useful when high variability of different parameters (as sea surface temperature and pCO2w ) is expected, as for example during upwelling situations and near coast, where the phytoplankton can significantly influence the concentration of CO2 at the surface. A wide study is done, including meteorological and oceanographic parameters, fluxes, comparisons, relations with parameters, transfer coefficients, dependences with the stratification and satellite images. / Mätningar av flöden (impuls, värme, vattenånga och CO2) vid två olika höjder studerades med data från en mast på ön Östergarnsholm (i Östersjön) under en vecka, beräkningar av flödena gjordes med mätningar av atmosfäriska parametrar från samma mast samt data från två bojar på två olika platser. Man fann olika beteenden för de beräknade och uppmätta flödena. Direkt (sensibelt) värme visade högre korrelation mellan beräkningar och uppmätta sensibla värmeflöden . För CO2- flödet fann man inte detta samband. För alla flödena överensstämmer mätningarna bättre med beräknade flöden när de är gjorda under instabila förhållanden, vilket betyder att under dessa förhållanden representerar mätningarna i masten bättre området där bojarna är placerade. Den studerade perioden inkluderar en period med upvällning (upwelling) och en hög horisontell variabilitet i ytparametrar under den största delen av denna period. Detta visades genom jämförelser mellan de beräknade och de uppmätta flödena och även genom satellitmätningar. Det område uppvind masten där ytan påverkar flöden uppmätta i masten på en viss nivå kallas ”footprint area”, och denna footprint area förändras kontinuerligt på grund av det stora beroendet av skiktningen i atmosfären. Eftersom skiktningen under hela perioden förändrades från något stabilt till något instabilt, kan ytvariabiliteten även ses i variationen av uppmätta flöden på olika höjder. En viktig slutsats i studien är att beräkningar av flödena som görs med standardformler inte bör användas vid förhållanden med hög horisontell och vertikal variation av olika parameter (som havsytetemperatur och pCO2w), som till exempel under uppvällningssituationer och nära kusten, där phytoplankton markant kan påverka koncentrationen av CO2 vid ytan. Studien inkluderar meteorologiska, oceanografiska parametrar, flöden, samband med parametrar, överförings koefficienter, beroende av stabilitet och satellitbilder. / Flujos turbulentos (momento, calor sensible, calor latente y CO2) en 2 alturas diferentes fueron estudiadas usando medidas de una torre en la Isla de Östergarnsholm (Mar Báltico) durante una semana. Los flujos también fueron calculados usando formulaciones con medidas de la torre y de dos boyas ancladas en diferentes localizaciones. Diferentes características para los distintos flujos fueron encontradas. El flujo de calor latente muestra una relación más alta con los cálculos que el flujo de calor sensible. No se encontró esta relación para el flujo de CO2. También, todos los flujos medidos en la torre coinciden mejor con los flujos calculados cuando estos son hechos bajo condiciones de estratificación inestable, significando que la torre mide mejor el área donde son cogidas las medidas en las boyas (cerca de la torre). El periodo estudiado incluye un afloramiento costero y se encontró una alta heterogeneidad horizontal en la superficie del mar durante la mayoría de los periodos. Esto fue estudiado usando las comparaciones entre flujos calculados y medidos y también usando imágenes de satélite. El footprint area puede ser definido como el área a una distancia desde la torre hacia donde sopla el viento donde las condiciones de la superficie influyen las medidas del flujo de alguna cantidad en la torre, y este footprint area está continuamente cambiando debido a su alta dependencia con la estratificación. Durante todo el periodo la estratificación estuvo cambiando desde ligeramente estable a ligeramente inestable, y por ello la heterogeneidad de la superficie puede ser vista en la variabilidad de los flujos medidos a diferentes alturas. Una conclusión importante en este estudio es que los cálculos de los flujos usando formulaciones podrían no ser útiles cuando se espera una alta variabilidad de los diferentes parámetros (temperatura superficial del mar y pCO2w), como por ejemplo durante situaciones de afloramiento y también cerca de costa, donde el fitoplancton puede influenciar significativamente la concentración de CO2 en la superficie. Se presenta un amplio estudio, incluyendo parámetros meteorológicos y oceanográficos, comparaciones de flujos, relaciones con parámetros, coeficientes de transferencia, dependencias con la estratificación e imágenes de satélite.

京都大学 / 0048 / 新制・論文博士 / 博士(理学) / 乙第13108号 / 論理博第1556号 / 新制||理||1620(附属図書館) / (主査)准教授 重 尚一, 教授 余田 成男, 教授 石川 裕彦 / 学位規則第4条第2項該当 / Doctor of Science / Kyoto University / DGAM