Sirje Keevallik

BALTEX—an interdisciplinary research network for the Baltic Sea region

BALTEX is an environmental research network dealing with the Earth system of the entire Baltic Sea drainage basin. Important elements include the water and energy cycle, climate variability and change, water management and extreme events, and related impacts on biogeochemical cycles. BALTEX was founded in 1993 as a GEWEX continental-scale experiment and is currently in its second 10 yr phase. Phase I (1993–2002) was primarily dedicated to hydrological, meteorological and oceanographic processes in the Baltic Sea drainage basin, hence mostly dealt with the physical aspects of the system. Scientific focus was on the hydrological cycle and the exchange of energy between the atmosphere, the Baltic Sea and the surface of its catchment. The BALTEX study area was hydrologically defined as the Baltic Sea drainage basin. The second 10 yr phase of BALTEX (Phase II: 2003–12) has strengthened regional climate research, water management issues, biogeochemical cycles and overarching efforts to reach out to stakeholders and decision makers, as well as to foster communication and education. Achievements of BALTEX Phase II have been the establishment of an assessment report of regional climate change and its impacts on the Baltic Sea basin (from hydrological to biological and socio-economic), the further development of regional physical climate models and the integration of biogeochemical and ecosystem models. BALTEX features a strong infrastructure, with an international secretariat and a publication series, and organizes various workshops and conferences. This article gives an overview of the BALTEX programme, with an emphasis on Phase II, with some examples from BALTEX-related research.

Winds in the Gulf of Riga from QuikSCAT and ground-based measurements

This article presents an overview of marine winds in the Gulf of Riga, measured by the SeaWinds instrument on the Quick Scatterometer (QuikSCAT) satellite during the whole lifetime period of the satellite, i.e. 1999–2009. The data were collected with a resolution of 12.5 km during the satellite overflights at 02–04 UTC and 16–18 UTC and referenced to the height of 10 m. The quality of the data was carefully checked, and necessary adjustment was applied to remove the contaminated recordings. Wind speed and direction were compared with those registered on the islands of Kihnu and Ruhnu. It has been shown that allowing lenient filtering of rain-contaminated data derives larger wind speed estimates but increases considerably the quantity of data, allowing separate analysis of the northern and southern parts of the gulf. Wind speed in the northern part is slightly higher, the wind roses for the early morning measurements are similar, but those for the evening measurements show that in spring and summer, the most frequent winds in the southern part are northwesterly and in the northern part are westerly. Wind speed measured on the islands is less than that estimated from the satellite even in the case when rain contamination is removed through application of strict criteria. Wind roses measured at Kihnu are practically similar to those estimated from satellites for the northern part of the gulf in the evening but show some differences during the early morning. In winter, ground-based measurements show maximal frequency of southerly winds, and satellite measurements show southwesterly winds. In spring, the secondary maximum in the wind rose shows northwesterly winds in ground-based records and easterly winds in satellite measurements. Ground-based wind directions are well correlated with those measured by the satellite showing correlation coefficients of over 0.9. For wind speed, this quantity is somewhat lower, i.e. around 0.6.