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CLIMATE MODEL PRECIPITATION TREND ANALYSIS IN THE 20 TH CENTURY

CLIMATE MODEL PRECIPITATION TREND ANALYSIS IN THE 20 TH CENTURY. Karen Rivas Key Acknowledgements: Xubin Zeng & Koichi Sakaguchi UA/NASA Space Grant Symposium April 21, 2012. Questions. Based on climate models how will global mean precipitation change?

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CLIMATE MODEL PRECIPITATION TREND ANALYSIS IN THE 20 TH CENTURY

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  1. CLIMATE MODEL PRECIPITATION TREND ANALYSIS IN THE 20TH CENTURY Karen Rivas Key Acknowledgements: Xubin Zeng & Koichi Sakaguchi UA/NASA Space Grant Symposium April 21, 2012

  2. Questions • Based on climate models how will global mean precipitation change? • How reliable are climate models in comparison with observational data in the past ~100 years?

  3. Approach and Methods • Analyze various climate model precipitation trends • Analyze observational precipitation trends from two distinct set of data • Draw conclusions from comparison of model precipitation trends and observational trends

  4. Climate Models • “Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice.” • The use of climate models ranges from studying earth weather dynamics, to making predictions about future climate. • Model accounts for incoming and outgoing energy due to electromagnetic radiation

  5. Data Analyzed • Models: • NCAR-CCSM-4 21st Century Projections (future) • NASA-GISS-E2-R 21stCentury Projections (future) • NCAR-CCSM-4 20thCentury Hindcasts (past) • NASA-GISS-E2-R 20thCentury Hindcasts (past) As used in the coming IPCC Report • Observational Data: • Global Land Precipitation, • Climatic Research Unit (CRU)

  6. Analysis Techniques Global mean precipitation is used to calculate: • change over ~100 year periods • respective change in 10-year windows Blue: Global mean annual precipitation from GISS E2-R Green: Linear fits for different 10-year periods

  7. Results Global Average Annual Precipitation (mm/year) and its Change over Historical Period 1900-1998

  8. Results Comparison between Models and CRU data for 10 year windows from Historical Period

  9. Future Projections Annual precipitation (black) and 10-year linear fits (colors) Change of annual precipitation rate (mm/year) over the whole 20th and 21st centuries

  10. Conclusion • Over the entire 20th century observational global mean precipitation has slightly increased • Over the entire 21st century both models project an increase in global mean precipitation • For the 10 year timescale, trend is highly variable and the model performance is poor for the 20th century.

  11. Future Studies • Look at smaller spatial scales • Look at longer temporal scale • Look at more models

  12. Thank You Karen Rivas Department of Chemical and Environmental Engineering University of Arizona April 21, 2012 Tucson, Arizona

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