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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