simulate urban-induced climate change via eos observations and land surface model dr. menglin jin,...

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


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


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?


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


(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0

2. How to Simulate Urban?

Land Surface Energy Budget:




Urbanization Modifies Surface Energy Budget:




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


3.2 MODIS Observed Global urban heat island effect

Comparison of skin temperaturefor urban and nearby forests

MODIS

Cities have higher Tskin

than forests


3.3 Urbanization changes surface albedo (MODIS)

The decrease of urban albedo is mainly caused by the decrease of reflectance at NIR

NIR

VIS

Albedo

Urban region

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

Total solar radiation decreased by aerosol= 20Wm-2

(Based on model of Ming-Dah Chou of NASA GSFC)

Aerosol decreases surface insolation



SH, LE, and G cannot be directly observed from satellite. Need to use model framework to examine

their changes.


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


Use MODIS observed surface properties into model


MODIS15_A2 Leaf Area Index (LAI) over Houston regions


MODIS11_L2 Emissivity_BAND 32 over Houston regions


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 Urban Model Results

Urban absorbs more Solar radiation

Absorbed Solar Radiation

4.3 CLM-Urban Model Results

Urban increase of SH can be as high as 15Wm-2, with maximum at local afternoon.


Urban increase upwardlongwave radiation


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.

simulate urban-induced climate change via eos observations and land surface model dr. menglin jin,...

Documents

urban model

urban scheme

urban impacts

urban features

modis urban albedo

urban simulating urbanization

menglin jin

land surface model slide