Impact of Urbanization on US Surface Climate

The Role of Vegetation

Ping Zhang1,2, Lahouari Bounoua1 , Kurtis Thome1, and Robert Wolfe1

1. NASA’s Goddard Space Flight Center 2. ESSIC, University of Maryland, College Park

2015 Tree Summit Dec 18, 2015

Basics

Energy

Surface Runoff Carbon Sequestration

Background Ecology Matters

•Cities in forested areas have much larger heat islands than cities in arid areas.

•Cities in grassy or agricultural areas are somewhere in the middle

Size Matters

City: Lynchburg, VA Philadelphia, PA Pop: 7000 1563000 Size: 29 km2 (11.2mi2) 790 km2 (11.2mi2) Heat Island:5.5 C (9.9F) 11.7 C (21.1F)

Not a surprise: Bigger cities have bigger heat islands!

Development Pattern Matters

Urban area: 355 km2(137 mi2)

Tree cover at rural: 84% UHI=12 C (21.6 F) Providence

Urban area: 320 km2 (124 mi2)

Tree cover at rural: 15% UHI=7 C (12.6 F) Buffalo

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Impervious Surface Area

% o

f T

ota

l U

rban

Pix

els

Providence

Buffalo

Shape Matters

Syracuse Area:152 km2

58.7mi2 UHI: 10.6C 19 F

Harrisburg Area:152 km2

58.7 mi2 UHI: 7.6 C 13.7 F

• Use Area to Perimeter ratio (A/P ratio) to characterize the shape and the degree of cohesion of each urban area

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Impervious Surface Area

% o

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Harrisburg

Syracuse

MODIS 1km NDVI

NLCD 30m

% impervious

Croplands

Impervious

FVC in a CMG (0.05 Deg.)

MODIS 1km LC

Fractional ndvi in a CMG (0.05 Deg.)

Combining Landsat and MODIS

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EN EB DB MF OS WS GL CL IS BS

CL

IS

WS GL

DB

MF

The Simple Biosphere model, developed in the Biospheric Sciences Laboratory code 618

Land Surface Model-SiB2

Surface laye

Root Zone

Recharge Zone

etc rc

2rb

rd

rsoil

Ec

ea

em

Ec + Eg

Eg

ra

L

Rn

P

+Wleaf

Wc

Wthro Wdrip

-Wrun

Wg

W1

W3

W2

-Wdrain

Um Tm

eci

egi

egs

z2

z1

d1

d2

d3

Canopy

Air Space

SiB2 Transfer pathway for Latent Heat

S

Water Balance

Energy Balance

Tc

Urban Heat Island

Baltimore

Washington

Surface Runoff

City DJF

Mean

JJA

Mean

Annual

Mean

Atl

anta

Precipitation 2.71 3.52 2.85

Surf

ace

runoff

Urban 1.69 62.4 1.67 47.0 1.58 55.4

MF 0.12 4.4 0.11 3.1 0.11 3.9

Was

hin

gto

n

DC

Precipitation 1.85 3.70 2.38

Su

rfac

e

run

off

Urban 0.95 51.4 1.67 45.0 1.17 49.2

BD 0.04 2.2 0.57 15.4 0.24 10.1

Carbon Lost

• About 1.4% of the current GPP is lost due to urbanization.

Trees are helpful

1. Mitigation of Heat 2. Reduction of flush floods 3. Sequestration of CO2

Thanks!

2015 Tree Summit Dec 18, 2015