Simulate Urban-induced Climate Change Via EOS Observations and Land Surface Model Dr. Menglin Jin,...
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Simulate Urban-induced Climate ChangeVia
EOS Observations and Land Surface Model
Dr. Menglin Jin,
Meteorology Dept, U
University of Maryland, College Park
Dr. Christa D. Peters-Lidard
NASA GSFC
Acknowledgements – Funded by NASA EOSIDS and NASA GSFC DDF
December 2003
Outline:
1. Rationale and Objectives2. How to simulate urban3. Observed Modifications of Urbanization Regions4. Model Results for urban physical processes5. Summary and future direction
Dr. Menglin Jin Univ. of Maryland, College Park
1. Rationale and Objectives
Dr. Menglin Jin Univ. of Maryland, College Park
Basic idea: Optimally combine satellite data into urban model. Satellite observations can help (a) better identify urban featuresand (b) improve model’s surface parameters
Problem: Land surface models coupled for GCM or regional models, do not simulate urban. For example, NCAR Community Land Model (CLM), NASA land model, GSFC land surface model, etc
Needs: Need to know what is urban how to simulate urban
Simulating urbanization in GCM/RCM is important to understand, project, and predict urban impacts on climate change
Objectives: Develop urban scheme in land surface model
Dr. Menglin Jin Univ. of Maryland, College Park
Question 1: Is urban region important enough for us to simulate in a GCM?
•(a) Is urban region big/significant enough?•(b) Are urban physical processes unique enough?
Question 2: How to simulate urbanization?
Dr. Menglin Jin Univ. of Maryland, College Park
Human Density of 1998
(Source: Ame. Association for the Advancement of Science)
•1000 household can make Tair higher about 2ºC than surround regions (Oke , 1976, Torok et al. 2002)
MODIS Observed Urban and Built-up
Dr. Menglin Jin Univ. of Maryland, College Park
(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0
2. How to Simulate Urban?
Land Surface Energy Budget:
Dr. Menglin Jin Univ. of Maryland, College Park
(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0
2. How to Simulate Urban?
Urbanization Modifies Surface Energy Budget:
Dr. Menglin Jin Univ. of Maryland, College Park
(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0
2. How to Simulate Urban?
Urbanization Modifies Surface Energy Budget:
Urban add new physical processes
50km
3.1 Urbanization changes surface temperature (Tskin)
Urban heat island effectDaytime Nighttime
50km 50km
MODIS
Comparison of skin temperaturefor urban and nearby forests
MODIS
Cities have higher Tskin
than forests
The decrease of urban albedo is mainly caused by the decrease of reflectance at NIR
NIR
VIS
Albedo
Urban region
Zonal Averages from MODIS
Urban albedo is lower than that of cropland
Urban emissivity is lower than that of cropland
Dr. Menglin Jin Univ. of Maryland, College Park
3.5. Urbanization changes atmospheric conditions
MODIS Aerosol Optical Depth
Total solar radiation decreased by aerosol= 20Wm-2
(Based on model of Ming-Dah Chou of NASA GSFC)
Aerosol decreases surface insolation
Dr. Menglin Jin Univ. of Maryland, College Park
(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0
SH, LE, and G cannot be directly observed from satellite. Need to use model framework to examine
their changes.
Dr. Menglin Jin Univ. of Maryland, College Park
Conceptual NCAR CLM-Urban Model
Urban model type:
water
Bare soilOriginal trees
Road/Building roofs SuburbanHuman-grassUrban-water body
If land coverIs urban
y n
Existing CLM Urban scheme
Dr. Menglin Jin Univ. of Maryland, College Park
MODIS15_A2 Leaf Area Index (LAI) over Houston regions
Dr. Menglin Jin Univ. of Maryland, College Park
Table for properties modified for Case 1 run
variable Control run Case1 run
LAI
Albedo-shortwave
Albedo-visible
emissivity
Heat capacity
Soil moisture
1.5 0.5
Control run – 0.25
Control run – 0.15
0.920.96
1.5*control run
Set as zero at first layer
4. CLM-urban model results
Urban increase ground temperatureby 1-3ºC, with the largest increase occurring at local daytime
Ground Temperature
4.2 CLM-urban model results
Urban increases land surface 2m surface air temperature,• at a lower rate than its effects on ground temperature/skin temperature•maximum at nighttime!
Surface air temperature
4.3 CLM-Urban Model Results
Urban increase of SH can be as high as 15Wm-2, with maximum at local afternoon.
Dr. Menglin Jin Univ. of Maryland, College Park
Summary
1. Satellite observations are extremely useful for understanding and simulating urbanization in climate models.
2. Urbanization needs to be included in GCM’s land surface model, in order to accurately reflect human impacts on global land climate system.
3. We need more accurate urban land cover, building density, and population information for simulating urban in global and regional scales.