Transcript Document
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 January5, 2006 MODIS Science Team Meeting 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. 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 Cloud Features at Various Spatial Scales Knowing other scales cannot ensure understanding at continental scale 5 year averaged Cloud Optical Thickness Land Impacts on Cloud Optical Thickness Continent Impacts on Cloud Optical Thickness Probability Density Function Temporal Variations of PDF for Cloud Optical Thickness land ocean MODIS Cloud Fraction Daytime Ocean Only (90°N-90°S, 180°E-180°W) Ocean Average Land 0.693 0.536 Land Seasonal range 0.04 0.11 MODIS Cloud Fraction Daytime MODIS Cloud Fraction Daytime Ocean Only Land Only MODIS Cloud Effective Radius Ice clouds Liquid water clouds Cirrus Fraction Land enlarges seasonality of cirrus fraction Column Water Vapor Land enlarges seasonality, and reduces the absolute value of water vapor MODIS Column Water Vapor NCEP Reanalysis Water Vapor MODIS is valuable to evaluate Reanalysis and model simulations Probability Density Function Monthly rainfall for Northern Hemisphere, North America,and Eurasia. GPCP Data Continents have larger rainfall seasonality Summary • MODIS observations are extremely useful in understanding land impacts on global climate. • 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