This project seeks to improve our understanding of the processes that modulate precipitation intensity, distribution, and type in mountainous regions in order to better distinguish between natural and climate change related variations. The research focuses on developing a 10-year climatology of moderate and heavy precipitation based on high-quality radar measurements within the European Alps.
Through the use of four-dimensional radar observations in conjunction with operational sounding analysis, Global Positioning System (GPS) derived water vapor fields, water vapor satellite images, and European Center for Medium Range Weather Forecast (ECMWF) reanalysis maps, the project will i) analyze the characteristics and four-dimensional structure of precipitation as well as determine time-space variations of precipitation within five regions with highly differentiated climate conditions, ii) determine the role of synoptic-scale atmospheric circulation and upstream conditions on the precipitation characteristics, and iii) determine seasonal and annual variability of precipitation characteristics, atmospheric circulation, and upstream conditions. Furthermore, the 10-yr precipitation climatology will be compared to rain-gauge and satellite observations, and regional climate model results for the Swiss Alps and other mountain areas around the World. The research will advance the knowledge about precipitation variations related to weather and climate.
The broader impacts of this project includes (i) the understanding of potential changes in precipitation intensity, frequency, and snow-rain distribution by monitoring precipitation and estimating changes in precipitation characteristics as being an important tool for policy makers and climate researchers to assess various future climate scenarios, (ii) the training of a graduate student, and (iii) wide dissemination of results and findings in conferences and refereed literature. The principal investigator will include the results into the university teaching curriculum and will give talks to non-research community as part of outreach efforts.
This project was aimed to improve our understanding of the processes that modulate precipitation intensity, distribution, and type in mountainous regions in order to better distinguish between natural and climate change related variations. The research focuses on developing an 11-yr (2000-2011) climatology of moderate and heavy precipitation based on high-quality radar measurements within the European Alps. Through the use of four-dimensional radar observations in conjunction with operational sounding analysis, GPS-derived water vapor fields, water vapor satellite images, and ECMWF reanalysis maps, the project i) analyzed the characteristics and four-dimensional structure of precipitation as well as determine time-space variations of precipitation within five regions with highly differentiated climate conditions, ii) determined the role of synoptic-scale atmospheric circulation and upstream conditions on the precipitation characteristics, and iii) determined seasonal, annual, and decadal variability of precipitation characteristics, atmospheric circulation, and upstream conditions and relate the results to long-term rain gauge analysis. Surface precipitation characteristics have been used to validate global climate model simulations and estimate future precipitation for seven Swiss river basins. The developed method provides an alternative approach to statistical and dynamic downscaling in order to predict future changes in precipitation characteristics. Although the research focused on the European Alps, results and methods can be applied to any mountain region around the World. The research proposed herein was designed to advance the knowledge about precipitation variations related to weather and climate. Major findings can be summarized as: In the European Alps, the summer season has the highest total daily precipitation and the strongest trend towards increasing total precipitation. Decrease in precipitation in the Alps has not been observed between 2000-2011. Daily synoptic-scale weather patterns are associated with total daily precipitation and high precipitation rate events, i.e., change in synoptic weather pattern as a result of a changing climate will most likely lead to a change in total daily precipitation and high precipitation rate. For instance, linking different climate scenarios to precipitation in the Alps via the synoptic weather pattern showed that the scenario with the strongest predicted increase in temperature shows the strongest decrease in precipitation in Swiss river basins (decreases of approximately 10-15% in total decadal precipitation). The analysis of vertical structure of precipitation systems revealed very distinct seasonal structure with storms having higher vertical extend (~10 km MSL) in summer (i.e., are more convective) compared to winter (~5 km MSL) storms. No trend in changes in vertical structure can be observed between 2004 and 2011. However, 3-day average surface temperature is related to precipitation vertical structure and surface precipitation characteristics for precipitation events, i.e., vertical structure of precipitation might change, when surface temperatures increase. Radar-observed vertical structure of precipitation combined with re-analysis data showed that radar-observed vertical structure of precipitation correlates with synoptic pattern, integrated water vapor flux, atmospheric stability, and vertical profiles of temperature, moisture, and wind. A generalized linear model (GLM), developed as part of this effort, provides expected values for the vertical extent and magnitude of radar reflectivity and predicts storm vertical structure type with 79% overall accuracy. The ability of the GLM to reproduce storm types shows the potential for using GLMs as a link between lower-resolution global model data and high-resolution precipitation observations. The broader impacts of this project included (i) the understanding of potential changes in precipitation intensity, frequency, and snow-rain distribution by monitoring precipitation and estimating changes in precipitation characteristics as being an important tool for policy makers and climate researchers to assess various future climate scenarios, (ii) the training of a graduate student, who used to work as part of his Ph.D. thesis, and (iii) wide dissemination of results and findings in conferences and refereed literature. The principle investigator included the results into the university teaching curriculum and gave talks to non-research community as part of outreach efforts. Data and algorithms are freely available to the research community.
