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Influence of soil moisture feedback on seasonal climate variation

Nir Krakauer Department of Civil Engineering, CCNY nkrakauer@ccny.cuny.edu ‏. Influence of soil moisture feedback on seasonal climate variation. Soil moisture feedback. soil moisture. P → E → P P → E → –T → (+/–)P. Previous work.

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Influence of soil moisture feedback on seasonal climate variation

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  1. Nir Krakauer Department of Civil Engineering, CCNY nkrakauer@ccny.cuny.edu ‏ Influence of soil moisture feedback on seasonal climate variation

  2. Soil moisture feedback soil moisture P → E → P P → E → –T → (+/–)P

  3. Previous work • Observational studies: more precipitation when soil is already moist (e.g. Findell & Eltahir, WRR 1997)‏ • Model studies of this correlation (e.g. GLACE, Koster et al., Science 2004)‏ • Combining the two: “correct” soil moisture model initialization leads to better forecasts (e.g. Dirmeyer, J Climate 2000)‏

  4. Questions • Does soil moisture feedback make droughts longer or bigger, and where? More generally, what is the impact of soil moisture feedback on space and time correlation scales? • Potential applications: seasonal drought prediction, impact of land management on climate.

  5. Model experiments • GISS ModelE GCM • DYNA run: 1951-1980, prescribed SST • CLIM run: same initial and boundary conditions, but soil moisture set to seasonal climatology from DYNA

  6. Correlation lengths Decay length of correlation between seasonal climate anomalies in the E-W direction

  7. Correlation times Correlation coefficient between MAM and JJA means

  8. Impact of soil moisture feedback on interannual variability (DYNA – CLIM)‏

  9. Impact on correlation lengthsDYNA - CLIM

  10. Impact on inter-season correlations

  11. and on P-T correlation

  12. Conclusions • Soil moisture feedback couples anomalies in temperature and precipitation and increases seasonal persistence. It has a quantifiable impact on the space and time scales of climate variability, which can be compared to observational datasets • Additional runs can address • Role of soil moisture feedback in multiyear droughts like the 1930s Dust Bowl • Land management (e.g. to increase soil moisture capacity) as modulating soil moisture feedback

  13. Possible summer research topics • Principal component analysis of fluctuations in global water-cycle data sets over the last 30 years (cloudiness, atmosphere water vapor, precipitation, temperature)‏ • Amplitude of dry/wet periods on a continental scale • Patterns in streamflow over dry periods (with M. Temimi)‏

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