East African precipitation is characterized by a dry annual mean climatology compared to other deep tropical land areas and a bimodal annual cycle with the major rainy season during March–May (MAM; often called the ‘‘long rains’’) and the second during October–December (OND; often called the ‘‘short rains’’). To explore these distinctive features, ERA-Interim data are used to analyze the associ...

Aerosol formation over the Boreal forest in Hyytiälä, Finland: monthly frequency and annual cycles – the roles of air mass characteristics and synoptic scale meteorology E. D. Nilsson and M. Kulmala Stockholm University, Department of Applied Environmental Science, 10691 Stockholm, Sweden University of Helsinki, Department of Physical Sciences, P.O. Box 64, 00014 Helsinki, Finland Received: 29 ...

Quantitative long-term measurements of VOC concentrations by PTR-MS: annual cycle at a boreal forest site T. M. Ruuskanen, R. Taipale, J. Rinne, M. K. Kajos, H. Hakola, and M. Kulmala University of Helsinki, Department of Physics, P.O. Box 68, 00014 University of Helsinki, Finland Finnish Meteorological Institute, P.O. Box 503, 00101 Helsinki, Finland Received: 19 September 2008 – Accepted: 20 ...

A two level quasi-geostrophic model for zonally averaged conditions has been integrated for a period of a few years. The model is forced by Newtonian heating and has internal and surface friction. The interaction between the zonal flow and the eddies is simulated through the use of exchange coefficients for the transports of quasi-geostrophic potential vorticity and sensible heat. The results o...

Influenza disease impacts every year up to 10% of the world's population, i.e. up to 500 millions of people. The international surveillance network organised by WHO allows the detection of important antigenic variation of the virus in humans but also animals (especially birds and pigs). Epidemiological data are summarised twice a year in two meetings (one in February, the other in September) al...

A central hypothesis of ecological immunology is that immune defences are traded off against competing physiological and behavioural processes. During energetically demanding periods, birds are predicted to switch from expensive inflammatory responses to less costly immune responses. Acute phase responses (APRs) are a particularly costly form of immune defence, and, hence, seasonal modulations ...

[1] A near-global ocean state estimate over the period 1992–2004 is used to study the mean seasonal cycle in sea level z. The state estimate combines most available observations, including all the altimetric missions, with a general circulation model in an optimization procedure. The annual cycle tends to be larger than the semi-annual one, except in tropical regions. For global mean z, annual ...