Century-long variability and trends in daily precipitation characteristics at three Finnish stations

Long-term variations and trends in a wide range of statistics for daily precipitation characteristics in terms of intensity, frequency and duration in Finland were analysed using precipitation records during 1908e2008 from 3 meteorological stations in the south(Kaisaniemi),centre(Kajaani) and north(Sodankyl€a). Although precipitation days in northern part were more frequent than in central and southern parts, daily precipitation intensity in the south was generally higher than those in the centre and north of the country. Annual sum of very light precipitation(0 mm < daily precipitation long-term 50 th percentile of daily precipitation more than 0 mm) significantly( p < 0.05) decreased over time,with the highest rate in northern Finland. These decreasing trends might be the result of significant increases in frequency of days with very light precipitation at all the stations, with the highest and lowest rates in northern and southern Finland, respectively. Ratio of annual total precipitation to number of precipitation days also declined in Finland over 1908e2008, with a decreasing north to south gradient. However, annual duration indices of daily precipitation revealed no statistically significant trends at any station. Daily precipitation characteristics showed significant relationships with various well-known atmospheric circulation patterns(ACPs). In particular, the East Atlantic/West Russia(EA/WR)pattern in summer was the most influential ACP negatively associated with different daily precipitation intensity, frequency and duration indices at all three stations studied.

Past and Future Changes in Climate and Water Resources in the Lancang–Mekong River Basin: Current Understanding and Future Research Directions

The Lancang–Mekong River(LMR)is an important transboundary river that originates from the Qinghai–Tibet Plateau,China and flows through six nations before draining into the South China Sea.Knowledge about the past and future changes in climate and water for this basin is critical in order to support regio-nal sustainable development.This paper presents a comprehensive review of the scientific progress that has been made in understanding the changing climate and water systems,and discusses outstanding challenges and future research opportunities.The existing literature suggests that:①The warming rate in the Lancang–Mekong River Basin(LMRB)is higher than the mean global warming rate,and it is higher in its upper portion,the Lancang River Basin(LRB),than in its lower portion,the Mekong River Basin(MRB);②historical precipitation has increased over the LMRB,particularly from 1981 to 2010,as the wet season became wetter in the entire basin,while the dry season became wetter in the LRB but drier in the MRB;③in the past,streamflow increased in the LRB but slightly decreased in the MRB,and increases in streamflow are projected for the future in the LMRB;and④historical streamflow increased in the dry season but decreased in the wet season from 1960 to 2010,while a slight increase is projected during the wet season.Four research directions are identified as follows:①investigation of the impacts of dams on river flow and local communities;②implementation of a novel water–energy–food–ecology(WEFE)nexus;③integration of groundwater and human health management with water resource assessment and management;and④strengthening of transboundary collaboration in order to address sustainable development goals(SDGs).

Evaluation of six gauge-based gridded climate products for analyzing long-term historical precipitation patterns across the Lancang-Mekong River Basin

Freshwater plays a vital role in global sustainability by improving human lives and protecting nature.In the Lancang-Mekong River Basin(LMRB),sustainable development is principally dependent upon precipitation that predominantly controls freshwater resources availability required for both life and livelihood of~70 million people.Hence,this study comprehensively analyzed long-term historical precipitation patterns(in terms of trends,variability,and links to climate teleconnections)throughout the LMRB as well as its upper(Lancang River Basin,LRB)and lower(Mekong River Basin,MRB)parts employing six gauge-based gridded climate products:Asian Precipitation Highly-Resolved Observational Data Integration Towards Evaluation of Water Resources(APHRODITE),Climate Prediction Center(CPC),Climate Research Unit(CRU),Global Precipitation Climatology Center(GPCC),Precipitation Reconstruction over Land(PRECL),and University of Delaware(UDEL).Accordingly,annual and seasonal(dry and wet)precipitation time series were calculated for three study periods:century-long outlook(1901-2010),mid-past(1951-2010),and recent decades(1981-2010).However,the role of climate teleconnections in precipitation variability over the LMRB was only identified during their available temporal coverages:mid-past and recent decades.The results generally showed that:(i)both annual and seasonal precipitation increased across all three basins in 1981-2010;(ii)wet and dry seasons got drier and wetter,respectively,in all basins in 1951-2010;(iii)all such changes were fundamentally attributed to increases in precipitation variability on both annual and seasonal scales over time;(iv)these variations were most strongly associated with the Pacific Decadal Oscillation(PDO),Atlantic Multi-decadal Oscillation(AMO)and East Pacific/North Pacific(EP/NP)pattern in the LMRB and the MRB during 1951-2010,but with the North Sea-Caspian Pattern(NCP)and the Southern Annular Mode(SAM)in the LRB;(v)such relationships got stronger in 1981-2010,while the Southern Oscillation Index(SOI)became the most influential teleconnection for dry season precipitation variability across all basins;and(vi)GPCC(APHRODITE)provided the most reliable gauge-based gridded precipitation time series over the LMRB for the years before(after)1951.These findings lay a foundation for further studies focusing on water resources and sustainable development in the LMRB.