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Land Impacts on Clouds, Water Vapor, and Rainfall at Continental Scales

This study examines the impact of continents on large-scale hydrological cycles, focusing on cloud, water vapor, and rainfall patterns. Using 5 years of NASA Terra and 3 years of NASA Aqua MODIS observations, TRMM observations, and global precipitation analysis, the study assesses how land affects these variables at continental scales. The findings show that landmass enhances seasonality of clouds, water vapor, and rainfall, while decreasing cloud fraction and liquid cloud effective radius. This research provides valuable insights for evaluating reanalysis and model simulations.

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Land Impacts on Clouds, Water Vapor, and Rainfall at Continental Scales

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  1. Observed Land Impacts on Clouds, Water Vapor, and Rainfall at Continental Scales Menglin Jin Department of Atmospheric & Oceanic Science University of Maryland, College Park Michael D. King Earth-Sun Exploration Division NASA Goddard Space Flight Center Greenbelt, Maryland January 5, 2006 MODIS Science Team Meeting

  2. 1. Scientific Questions: How do the continents affect large-scale hydrological cycles? How important can one continent be to the climate system? • 2. Data Sets Used: • 5-years of NASA Terra MODIS observations; • 3-year NASA Aqua MODIS observations; • TRMM observations; • Global Precipitation Climatology Project (GPCP); global precipitation analysis; • NCEP reanalysis; • to assess the land impacts on clouds, rainfall, and water vapor at continental scales.

  3. 3. Why Continental Scale? - Importance of Continental Scale • Features at continental scale is index of land impact on climate • Continental scale is critical in testing the accuracy of GCM • Coe, M.T. (2000, J. of Climate), • Jin, M. et al. (1997 J. of Climate) • Few studies focus on continental scale With knowledge of local/global features, can we extend to know the features at continental scale? Answer: No. As climate system is nonlinear

  4. Cloud Features at Various Spatial Scales Knowing other scales cannot ensure understanding at continental scale

  5. 5 year averaged Cloud Optical Thickness

  6. Land Impacts on Cloud Optical Thickness

  7. Continent Impacts on Cloud Optical Thickness

  8. Probability Density Function Globe Northern Hemisphere

  9. Temporal Variations of PDF for Cloud Optical Thickness land ocean

  10. MODIS Cloud Fraction Daytime Ocean Only (90°N-90°S, 180°E-180°W) Ocean Land Average Land 0.693 0.536 Seasonal range 0.04 0.11

  11. MODIS Cloud Fraction Daytime

  12. MODIS Cloud Fraction Daytime Ocean Only Land Only

  13. MODIS Cloud Effective Radius Ice clouds Liquid water clouds

  14. Cirrus Fraction Land enlarges seasonality of cirrus fraction

  15. Column Water Vapor Land enlarges seasonality, and reduces the absolute value of water vapor

  16. Probability Density Function

  17. Monthly rainfall for Northern Hemisphere, North America,and Eurasia. Continents have larger rainfall seasonality

  18. Mechanisms for Land Impacts on Clouds Mechanism 1. Surface Temperature Difference Mechanism 2. Temperature Seasonality Difference

  19. Summary • MODIS observations are extremely useful. • Land mass enhances seasonality of clouds, water vapor, and rainfall • Land decreases the liquid cloud effective radius, cloud fraction, and water vapor • Need More Work on providing • insightful statistics • physical interpretation

  20. MODIS Column Water Vapor NCEP Reanalysis Water Vapor MODIS is valuable to evaluate Reanalysis and model simulations

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