Transcript Document

Simulate Urban-induced Climate Change
Via
EOS Observations and Land Surface Model
Dr. Menglin Jin,
Meteorology Dept, U
University of Maryland, College Park
Dr. Christa D. Peters-Lidard
NASA GSFC
December 2003
Acknowledgements – Funded by NASA EOSIDS and NASA GSFC DDF
Outline:
1.
2.
3.
4.
5.
Rationale and Objectives
How to simulate urban
Observed Modifications of Urbanization Regions
Model Results for urban physical processes
Summary and future direction
Dr. Menglin Jin
Univ. of Maryland, College Park
1. Rationale and Objectives
Simulating urbanization in GCM/RCM is important to understand,
project, and predict urban impacts on climate change
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
Objectives: Develop urban scheme in land surface model
Needs: Need to know what
is urban
how to simulate urban
Basic idea: Optimally combine satellite data into urban model.
Satellite observations can help (a) better identify urban features
and (b) improve model’s surface parameters
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)
Dr. Menglin Jin
Univ. of Maryland, College Park
MODIS Observed Urban and Built-up
•1000 household can make Tair higher about 2ºC than surround regions
(Oke , 1976, Torok et al. 2002)
2. How to Simulate Urban?
Land Surface Energy Budget:
(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0
Dr. Menglin Jin
Univ. of Maryland, College Park
2. How to Simulate Urban?
Urbanization Modifies Surface Energy Budget:
(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0
Dr. Menglin Jin
Univ. of Maryland, College Park
2. How to Simulate Urban?
Urbanization Modifies Surface Energy Budget:
(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0
Urban add new physical processes
Dr. Menglin Jin
Univ. of Maryland, College Park
3.1 Urbanization changes surface temperature (Tskin)
MODIS
Urban heat island effect
Daytime
Nighttime
50km
50km
50km
3.2 MODIS Observed Global urban heat island effect
Dr. Menglin Jin
Univ. of Maryland, College Park
Comparison of skin temperature
for urban and nearby forests
MODIS
Cities have higher Tskin
than forests
3.3 Urbanization changes surface albedo (MODIS)
Dr. Menglin Jin
Univ. of Maryland, College Park
Urban region
NIR
Albedo
VIS
The decrease of urban albedo is mainly caused by
the decrease of reflectance at NIR
3.4 Urbanization changes surface emissivity (MODIS)
50km
50km
Zonal Averages from MODIS
Urban albedo is lower than
that of cropland
Urban emissivity is lower
than that of cropland
3.5. Urbanization changes atmospheric conditions
MODIS Aerosol Optical Depth
Dr. Menglin Jin
Univ. of Maryland, College Park
Aerosol decreases surface insolation
Total solar radiation decreased by aerosol
= 20Wm-2
(Based on model of Ming-Dah Chou of NASA GSFC)
(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
water
If land cover
Is urban
y
Existing CLM
Dr. Menglin Jin
n
Urban scheme
Urban model type:
Bare soil
Original trees
Road/Building roofs
Suburban
Human-grass
Urban-water body
Univ. of Maryland, College Park
Use MODIS observed surface properties into model
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
MODIS11_L2 Emissivity_BAND 32 over Houston regions
Dr. Menglin Jin
Univ. of Maryland, College Park
Table for properties modified for Case 1 run
variable
LAI
Control run
1.5
Case1 run
0.5
Albedo-shortwave
Control run – 0.25
Albedo-visible
Control run – 0.15
emissivity
0.96
0.92
Heat capacity
1.5*control run
Soil moisture
Set as zero at first layer
Dr. Menglin Jin
Univ. of Maryland, College Park
4. CLM-urban model results
Ground Temperature
Urban increase ground temperature
by 1-3ºC, with the largest increase
occurring at local daytime
4.2 CLM-urban model results
Surface air temperature
Urban increases land surface 2m surface air temperature,
• at a lower rate than its effects on ground temperature/skin temperature
•maximum at nighttime!
4.3 Urban Model Results
Absorbed Solar Radiation
Urban absorbs more
Solar radiation
4.3 CLM-Urban Model Results
Urban increase of SH can be
as high as
15Wm-2, with maximum at
local afternoon.
4.3 CLM-Urban Model Results
Urban increase upward
longwave radiation
4.3 CLM-Urban Model Results
Urban reduces ground flux
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.
Dr. Menglin Jin
Univ. of Maryland, College Park