<p> The Intertropical Convergence Zone (ITCZ) is a feature that results from the ocean-atmosphere interactions in the tropics around the world. The ITCZ is characterized by surface wind convergence, tall storm clouds, and it forms a belt of high time-averaged precipitation around the globe. The ITCZ undergoes seasonal migrations between 5&deg;S and 15&deg;N roughly following the subsolar point on Earth with the seasons, with a mean annual position located slightly above the Equator, between 2&deg; and 5&deg;N. </p><p> This study tested the hypothesis that there was a northward shift in the median position of the ITCZ in the first decade of the 2000&rsquo;s relative to the 1900&rsquo;s. This hypothesis has been posed in the literature given a weakening in the intensity of the Trade Winds observed in the southern Caribbean Sea during the first decade of the 2000&rsquo;s, with concomitant ecological impacts due to weakening in coastal wind-driven upwelling. The hypothesis was tested by analyzing variations in the monthly latitudinal position of the ITCZ over the Atlantic Ocean relative to the median position computed for the period 1987&ndash;2011. The position of the ITCZ was derived from satellite-derived ocean surface wind measurements collected from 1987 to 2011. A Mann-Kendall analysis and a Monte Carlo simulation were used to test for trends in the median cross-basin latitudinal position of the ITCZ. The study included an analysis of regional changes across the tropical central Atlantic (50&deg;W to 15&deg;W), the Western Atlantic (50&deg;W to 30&deg;W), and the Eastern Atlantic (30&deg;W to 15&deg;W) within the tropics. The results show a slight southward trend in the median position of the ITCZ over the central Atlantic and also in the Eastern Atlantic in the first decade of the 2000&rsquo;s relative to the 1990&rsquo;s. While this trend is barely significant, it is likely simply due to interannual variation in the average annual position of the ITCZ. </p><p> The data were also examined for the timing and persistence of a double ITCZ in the Atlantic. The double ITCZ over the Atlantic appeared every year in February or March, with the largest separation between the northern and southern branches of the ITCZ observed in June and July. </p><p> The possible effects of changes in the average latitudinal position of the ITCZ on the upwelling in the Cariaco Basin (southeastern Caribbean Sea off Venezuela) were also examined. Anomalies of the median of the latitudinal position of the ITCZ in the Atlantic were compared with anomalies of in-situ temperature collected during the 1990&rsquo;s and the first decade of the 2000&rsquo;s by the CARIACO Ocean Time-Series program and with anomalies of satellite SST (from the Advanced Very High Resolution Radiometer satellite; AVHRR) from 1995 to 2016. Correlation analysis were performed between anomalies of water temperatures at various depths and anomalies of satellite SST with anomalies of the monthly mean ITCZ position with lags up to 3 months for the time series, and also just for the Cariaco basin upwelling months (December-April). </p><p> For the whole Cariaco time series there were no significant correlations between the anomalies of the ITCZ position and anomalies in subsurface temperatures in the Cariaco Basin. However, during the upwelling period, the central Atlantic and Western Atlantic ITCZ position anomalies were directly correlated with Cariaco Basin temperature anomalies with no-lag (r = 0.20), and the central and Eastern Atlantic ITCZ position anomalies were inversely correlated with Cariaco Basin temperatures (r ~ -0.22 to -0.28) with ITCZ leading Cariaco temperatures by 3 months. However, these correlations were low, indicating that other factors than the position of ITCZ latitudinal position play bigger role on the Cariaco basin upwelling variability. </p><p> Interannual variability in oceanographic and meteorological characteristics of the Atlantic Ocean are expected as a result of large-scale changes in other regions of the world, including due to changes such as the El Ni&ntilde;o Southern Oscillation (ENSO) and the Atlantic Multidecadal Oscillation (AMO). Six oceanic-atmospheric variables are used to monitor ENSO over the tropical Pacific, while the AMO is determined by monitoring SST over the Atlantic. Correlations with lags of up to &plusmn; 6 months were conducted with those climate indices and the anomalies of the median monthly latitudinal position of the ITCZ. Significant direct correlations with ENSO (Multivariate ENSO Index) were seen in the Atlantic and Western Atlantic (r = 0.15), with ENSO leading the position of the ITCZ anomalies by 3 months. This implies that within three months after an El Ni&ntilde;o event (warm ENSO anomaly in the Pacific) the ITCZ over the mid-Atlantic and Western Atlantic Ocean tends to shift to a more northerly position. The AMO also had a direct influence on the anomalies of the ITCZ position (r = 0.13) in the Central and the Western Atlantic, with the AMO leading ITCZ anomalies by 1 month (i.e. a warming of the North Atlantic led to a northward shift in the ITCZ one month later). Correlations between AMO and the ITCZ anomalies in the Eastern Atlantic were also direct but with no lag. Although significant, these correlations were low. </p><p> An inverse correlation (~ -0.35) was found between ENSO and anomalies of water temperature of the Cariaco Basin. ENSO lagged ocean temperature anomalies by 3 to 4 months for both the whole Cariaco time series and for the upwelling months of CARIACO data. Correlations with AMO were direct (~ 0.4); for the whole time series AMO led Cariaco temperature anomalies by 3 months, but for the upwelling months AMO lagged Cariaco temperature anomalies by one month.</p>

A survey of Myxosporidia in teleosts from the South-Western coast of England demonstrated the widespread occurrence of these parasites. Infection in selected fish species was related to age, sex and seasonal migration of the host. Structural studies of Myxobolus exiguus and Myxidium incurvatum were undertaken in order to investigate sporogenesis, parasite development and the host-parasite interface. Of particular note was the intimate association between parasite and host cells, the structure of the surface layers in Myxobolus exiguus and Myxidium incurvatum, and the occurrence of epithelioid cells in developmental stages of Myxobolus exiguus. Myxobolus exiguus was transmitted experimentally in mullet, and aspects of the mode of infection, including exsporulation, were studied in this and other species, including those with coelozoic development patterns. Experiments designed to simulate the gut biotope identified the action of trypsin and mechanical fracture as important exsporulation factors in Myxobolus exiguus. The release of spores and their dispersal and survival outside the host were investigated, and the possible existence of intermediate transport hosts discussed. Pathological effects of histozoic and coelozoic myxosporidian infection were examined in selected hosts. Fibroblastic encapsulation of plasmodia, and hyperplasia, characterised intestinal and branchial infections of Myxobolus exiguus in mullet, and cystic replacement of renal tissue was associated with Myxidium giardi infection in eels. Biliary myxosporidiosis caused chronic irritation and fibrosis of the gall bladder wall, increased bile viscosity and discolouration. Incidence, periodicity and severity of various Myxosporidian infections are discussed with regard to their disease potential and possible impact on commercially-important teleost species.

No description available.

The vertical structure in the coastal marine atmosphere has been investigated using data from aircraft measurements performed along the Blekinge coast. The present data are from the third of October 1990. The main feature is fairly homogeneous horizontal conditions and a subceeing boundary layer which lowers from 600 meters down to about 50 meters during the day. The turbulence were found to be in a decreasing state. The turbulence parameters were normalized using normal stationary scaling, in order to compare with other results.

Conclusions In this work we have used a multiple linear regression model, to see how different predictors are correlated to each other, and how they are correlated to temperature and precipitation in the southern part of Sweden. The correlation between the large and small indices vary over the year, but both cases show an increase in correlation during the winter. The MoVa index and the ViGö index are much better correlated than what the NAO and the KaUp indices are. One possible explanation for this can be the much shorter distace between the lines MoVa and ViGö in the latitudinal direction, compared to the distance in the longitudinal direction between NAO and KaUp. The correlation between the predictors and the predictands, temperature and precipitation, vary between different stations. The south-north predictors, NAO and KaUp, show different signs concerning the temperature in the summer. This is remarkable, but one should have in mind, that the correlation coefficient between the two is very low during the summer months. To recieve a good approximation concerning the precipitation amount by using this multiple regression model, it’s almost enough to use the mean pressure predictor, because the other predictors are very low or not even significant, except for some stations. The NAO predictor is only significant for a few months concerning precipitation. It should also be mentioned, that the model shows a lower amount of precipitation than what is observed when we are talking about great amounts of precipitation.  Finally, this regression model is based on pressure differences or just the mean pressure. This means, that the model doesn’t take into account such phenomena as convective clouds, local rain or thunder storms, subsidence inversions, sea breeze effects, etc.

The turbulence structure in a stable boundary layer over ice has been studied. Data from the Bothnian Bay, measured during the BASIS field campaign in February/March 1998, have been used. Turbulence as well as wind- and temperature profiles were measured at three sites. The sites were Umeå at the Swedish East Coast, Kokkola at the Finnish West Coast and the ship R/V Aranda outside the Finnish coast.  Turbulence parameters are studied in terms of their stability dependence. At stronger stability σu/u*, σv/u* and σw/u* all increase with stability. At near neutral stratification σw/u* increases with height. A linear dependence of the pressure gradient scale ln(zf/u*) is seen for σw/u* in the interval 0&lt;z/L&lt;0.1. σw/σu  first increases and then decreases with stability in agreement with earlier results. From the results it is concluded that the turbulence structure in the stable boundary layer over ice follows the Monin-Obukhov similarity theory. In some of the studied parameters the results from the Umeå site deviate from the other two. Since Umeå has a larger measuring height (10 m) than the other two (2 and 3.5 m) the conclusion is drawn that the surface layer height is lower than 10 m.  Data from the Umeå site has been used to study atmospheric phenomena that develop over the marginal ice zone. During two days two phenomena were observed that were triggered by the temperature difference between ice and water - a stable internal boundary layer and an ’ice breeze’ similar to the land breeze. The development of the internal boundary layer has been studied by using an expression for internal boundary layer height. A criterion earlier used to forecast the sea breeze has been shown to be suitable also for the ’ice breeze’.

Two days with bora has been numerically analysed, using a three dimensional hydrostatic mesoscale model developed at the Department of Meteorology, Uppsala University. The two simulated days, 22 March and 15 April 1982, have been compared to aircraft measurements done during the ALPEX-SOP in 1982. The model area was the northeastern shore of the Adriatic Sea. The bora on 15 April was easier to simulate than the one on 22 March, mostly due to the fact that this bora was shallower than the one on 22 March, and since the used model is developed for mesoscale studies, it works better with smaller scales (on the mesoscale). The simulations show that the bora character is a function of both time and space, for example changes in turbulence intensity. Three dimensional effects play an important role, for example channeling effects, which was also confirmed by the simulations. Compared to measurements, the model simulates the two days well, especially 15 April. All the significant features of the bora wind were well simulated, the wind speed maximum at the ridge crest, the descent of isotherms and isolines of specific humidity downstream the crest, channeling effects etc. The turbulence was not always present just above the ridge crest, but at some times and some places it was well simulated. The most difficult variables to simulate was the specific humidity and the potential temperature.

Detta examensarbete har utförts för att bestämma fördelningen av blixtnedslag i Sverige. En databas med blixtdata för åren 1987-1994 har använts. Antalet blixtar per 100 km2 och månad har beräknats, de högsta medelvärdena är 10 blixtnedslag och dessa erhålles under juli månad. Andelen positiva blixtar har även undersökts och funnits variera beroende av latitud och temperatur. Under vintermånaderna är andelen positiva blixtnedslag större än under sommarmånaderna.

Syftet med studien är att finna korrelation mellan olika meteorologiska parametrar. För att göra detta har data insamlade av avdelningen Försök och Prov, vid flygvapnets väderskola, använts. Mätningarna som använts här är gjorda på Kostabasen i Småland från den 13 oktober 1993 till den 25 april 1994. Insamling har skett med den så kallade Bas90-vagnen. Studien är begränsad till atmosfärens gränsskikt. Gränsskiktet kan delas in i två delar, ett ytskikt närmast marken samt ett övergångsskikt ovanför detta. Då luft flödar över en ny typ av yta bildas ett internt gränsskikt. Utgående ifrån mätningarna har grafer ritats och analyserats. Med hjälp av minsta kvadrat metoden har enkla uttryck för korrelationen tagits fram och jämförts med mätdata. Korrelationer mellan följande parametrar har undersökts: • molnbas - vindhastighet och vindriktning • molnbas - stabilitet • molnbas - fuktighet, med och utan nederbörd • molnbas - sikt Bäst korrelation erhölls mellan molnbas och relativ fuktighet där ett tydligt samband erhölls. Korrelationen mellan molnbas och de övriga parametrarna var mycket sämre. Mellan molnbas och stabilitet erhölls ingen korrelation.

I den här studien analyseras gränsskiktshöjdens betydelse för hastighetsfältet i ytskiktet, med hjälp av Monin-Obukhovs (MO) similaritetsteori. Studien genomfördes för att verifiera tidigare resultat från en Large-Eddy simulering av Khanna och Brasseur (1995) som tyder på att hastighetsfältet inte bara beror på z/L utan även har ett starkt beroende av gränsskiktshöjden. Genom att använda mastmätningar och sonderingar från Marsta studeras hastighetsfältet och speciellt den dimensionslösa vindgradienten (Φm) och de normaliserade hastighetsvarianserna i horisontalled och vertikalled. Det visar sig att båda parametrarna är beroende av gränsskiktshöjden. Resultatet från studien är att MOs similaritetsteori inte gäller för hastighetsfältet vid instabil skiktning vilket är samma resultat som antyddes i Khanna och Brasseurs (1995) studie. Detta tyder på att de storskaliga rörelserna i gränsskiktet påverkar ytskiktet mer än vad som tidigare varit känt.