University of Houston IMAQS MM5 Meteorological Modeling for Houston-Galveston Area Air Quality...

University of HoustonIMAQS

MM5 Meteorological Modeling for Houston-Galveston Area Air Quality Simulations

Daewon W. Byun

Bonnie ChengUniversity of Houston

Institute for Multidimensional Air Quality Studies (IMAQS)


Objectives:Study the effects of land use and land cover modification on the urban heat island development and on the air quality in the Houston-Galveston metropolitan area.

Methods:

•Improve meteorological simulations by applying better physics (today’s presentation)•Incorporate most up-to-dated detailed land use and land cover data (on-going)


• Land-sea breeze circulation is influenced by land surface processes

• It controls the surface sensible/latent heat & momentum fluxes

• They in turn influence PBL structure and convective processes

• The land surface characteristics like topography, soil moisture and land use and land cover need to be described better.

Land Surface Process


• Meteorological simulations for the HGA provided by the Texas A&M (Dr. John Nielsen-Gammon) accurately predict maximum temperatures and reproduce the large-scale temperature patterns using slab land-surface model.

• The model performance is good, but is less successful for the PBL heights in rural areas.

• To better understand Houston high ozone problem, and to understand the impact of urban vegetation, we need to use LSM with better physics

Previous Work


How to model the land-surface processes in Mesoscale models?

(1) Force-restore 2-layer energy balance model with a constant temperature

substrate (specified in INTERP the daily average surface temperature tuned to represent diurnal cycle best)

(2) 5-Layer slab modelAdded multiple soil layers to represent heat conduction to

the Force-restore model (3) Comprehensive land surface model with vegetation


• Ground heat budget model with multiple layers (5)• Improved version of a 2-layer force-restore surface

energy balance model• Couples surface momentum, heat, and moisture

fluxes• But, no treatment of evapotranspiration• No moisture diffusion in the soil layer

Predict temperature at 5-soil layers.1, 2, 4, 8, 16 cm thick

Current TAMU Base Simulation UsesSimple “5-layer” slab model


• Current LU/LC data used in MM5 simulation: USGS ~1-km resolution.

• Higher resolution of LU/LC data now becomes available

• Dominant LU/LC algorithm used in MM5 does not allow mosaic LU/LC land-surface processes (unless the code is modified)

• The question is how to make best MM5 land-surface simulations if our LU/LC data is limited by the current data

Modeling Land Surface Process


How to better model the land-surface processes?

• Use comprehensive land-surface model• NOAH LSM (N:National Center for Environmental

Prediction; O: Oregon State University; A: Air Force; H: Hydrological Research Lab.) (Ek et al., 2001).

• 4-layers (10, 30, 60, and 100 cm thick)• Predicts soil temperature, soil water, canopy water, and

snow/ice• Central difference of the NOAH from slab model is stomatal

resistance and transpiration formulation


http://www.mmm.ucar.edu/wrf/workshop/2003/WRF_Session2/LSM_Fei/Slide1.html

http://www.mmm.ucar.edu/wrf/workshop/2003/WRF_Session2/LSM_Fei/Slide14.html

Urban : 10 sites Rural : 18 sitesdominant landuse data used in MM5

Stephen Stetsen, GEMPete Smith, Texas Forest Service

Design of Meteorological Simulation: S1(SLAB)

• First, (Base case): MM5 simulation coupled with the slab soil model (case S1). Soil moisture was increased in the urban area to make it wetter; decreased in the rural area make it drier.

Name Category

108 and 36 km (default)

12km 4km

08/22~08/26 08/26~08/28 08/28~09/02

Urban 1 10 10 30 20 20

Dryland 2 30 20 20 20 10

Cropland 5 25 15 20 15 10

Grassland 7 15 10 30 10 10

Deciduous forest 11 30 30 20 25 15

Evergreen forest

14 30 20 10 20 10(Soil moisture value (%), Dr. Nielsen-Gammon, J. W., 2002)

• S1 simulation is provided by TAMU.

University of HoustonIMAQSConfiguration of MM5 simulations

• Analysis nudging for d1,d2,d3; observation nudging(wind vector)for d4

• d1, d2 2way nesting; d3,d4 continuous one-way nesting • MRF PBL Parameterization • Dudhia explicit moisture scheme • RRTM radiation scheme• Slab land-surface model (LSM)

D2

D3D4

D1

Simulation time: Aug. 22~Sep.02, 2000

Domain X (km) Y (km) Z

1 108 108 43

2 36 36 43

3 12 12 43

4 4 4 43

D4

Design of Meteorological Simulation: S2(NOAH)

• Experiment #2: Use the recently developed NOAH Land Surface Model (NOAH LSM) (EK, 2001) with identical inputs and model configurations as in S1 case except using different land-surface parameterizations (S2).

S1 (TAMU) S2

LSM SLAB NOAH

Treatment of

Soil Moisture

(SM)

Increased SM in urban area

Decreased SM in rural area (Dr. Nielsen-Gammon, 2002)

SM is internally updated with the recent precipitation and

runoff processes

Scattered Diagram of 2-m Temp

Scattered diagram of 2-m temperature with (a) S1; (b) S2 simulations.

(a) (b)

Observed/Predicted Windspeed (S1--SLAB)

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CST

10m WS,WD from metstat program (Emery, 2001)

Averaged over the CAMS sites

Summary of problems with the MM5/NOAH simulation with default parameters.

1. Simulated daytime temperature too high, and nighttime temperature too low at urban sites.

2. The urban area was treated as if totally covered with impervious surfaces. Therefore, we have large diurnal variations in temp and very low latent/sensible heat flux ratio.

3. At rural sites, we have no daytime temperature bias, but serious nighttime temperature bias.

4. Serious delays in the development of diurnal wind speed build up – related to #3?

5. Initially, we thought it were soil moisture problem, but …?

Vegetation Parameters in LSMVegetation Parameters

USGS

27,1, 'ALBEDO Z0 SHDFAC NROOT RS RGL HS SNUP LAI MAXALB'

1, .15, 1.00, .10, 1, 200., 999., 999.0, 0.04, 4.0, 40., 'Urban'

2, .19, .07, .80, 3, 40., 100., 36.25, 0.04, 4.0, 64., Dryland Cropland

3, .15, .07, .80, 3, 40., 100., 36.25, 0.04, 4.0, 64., 'Irrigated Cropland

4, .17, .07, .80, 3, 40., 100., 36.25, 0.04, 4.0, 64., Dryland/Irrigated'

5, .19, .07, .80, 3, 40., 100., 36.25, 0.04, 4.0, 64., 'Cropland/Grassland

6, .19, .15, .80, 3, 70., 65., 44.14, 0.04, 4.0, 60., 'Cropland/Woodland'

7, .19, .08, .80, 3, 40., 100., 36.35, 0.04, 4.0, 64., 'Grassland'

8, .25, .03, .70, 3, 300., 100., 42.00, 0.03, 4.0, 69., 'Shrubland'

9, .23, .05, .70, 3, 170., 100., 39.18, 0.035, 4.0, 67., 'Shrubland/Grass'

10, .20, .86, .50, 3, 70., 65., 54.53, 0.04, 4.0, 45., 'Savanna'

11, .12, .80, .80, 4, 100., 30., 54.53, 0.08, 4.0, 58., 'Broadleaf Forest'

12, .11, .85, .70, 4, 150., 30., 47.35, 0.08, 4.0, 54.,'Needleleaf Forest'

13, .11, 2.65, .95, 4, 150., 30., 41.69, 0.08, 4.0, 32., 'Broadleaf Forest'

14, .10, 1.09, .70, 4, 125., 30., 47.35, 0.08, 4.0, 52.,'Needleleaf Forest'

15, .12, .80, .80, 4, 125., 30., 51.93, 0.08, 4.0, 53., 'Mixed Forest‘

: : : : : : : : : : : :

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Parameters that determine evapotranspiration

S1 (TAMU) S2 S3

LSM SLAB NOAH NOAH

Treatment of

Soil Moisture

Increase SM in urban area;

Decrease SM in rural area;

(Dr. Nielsen-Gammon, J. W., 2002)

Add canopy moisture (CM) in urban area

Design of Meteorological Simulation

• Question: How to treat the evapotranspiration from 20% tree/vegetation coverage when the current dominant category of USGS 25-LU/LC is used?

• Experiment S3: We added new anthropogenic canopy water source in the urban area in the NOAH LSM to reflect Houston’s 20% urban vegetation and thus reduce the daytime temperature bias.

Addition of Canopy Moisture

is intercepted canopy water content

is green vegetation fraction

is input total precipitation

canopy evaporation

If exceeds S (maximum canopy capacity: 0.5 mm), the excess precipitation or drip, reaches the ground.

ucfc EEDPt

W

cW

f

P

cE

cW

D

uE is the anthropogenic contribution to the canopy water content. A reasonable value 3x10-6 (meter of available water per second) was picked for the simulation (* need to be justified).

Surface (2-m) Temp Analysis

Urban

Rural

• Now, temperature simulations at urban areas improved, not much change at rural sites.

• Minimum temperature problem still exists both urban and rural sites

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urban_avg S1 S2 S3

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rural_avg S1 S2 S3

CST

Scattered Diagram of 2-m Temp

Scattered diagram of 2-m temperature with (a) S2; (b) S3 simulations.

(a) (b)

Wind Profiler Sites (TexAQS-2000)

PBL Height Analysis from S1, S2 and S3 simulations on Aug. 25Profiler PBL ht. from NOAA/FSL

CST

S3_Aug. 25 PBl ht(m)

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PBL Height Analysis from S1, S2 and S3 simulations on Aug. 27


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MM5 sensitivity test continued tocorrect min. temperature problem

a. Test emissivity value for different LU categories

(original emissivity in NOAH =1.0)

Name Category Emissivity

Dryland 2 0.98

Cropland 5 0.95

Grassland 7 0.95

Evergreen forest 14 0.95


Test case with modified emissivity: at a few sites we see imbalance between the energy budget and PBL growth, which results in abnormally high surface temperatures simulated

To improve minimum temperature bias --- test


MM5 sensitivity test continued tocorrect min. temperature problem

Fei Chen modification for urban LU parameters

a. Change heat capacity from 3.0E06 to 2.0E06 (J/m^3/K)

b. Thermal conductivity equals 3.24 (W/m/K)

c. Change RSMIN from 200 to 300 (s/m)

But, max. temperature problem for urban LU comes back at 4-km simulation even with the added canopy water.

We consider changes in items “a” and “c” may cause this problem

z

TK

zt

TC )()(

)(C

)(K


With modified land use parameters to reflect urban vegetation better ( in particular, heat capacity change is the key in fixing min. temperature) (12-km result, Fei-Chen urban mod)


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urban_avg S1 S2 Fei_modify

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2-m temperature

Lower bias problem was resolved in the urban area but maximum temp is still too high.

Rural min. temp problem still existing

Fei Chen urban LU modification


2-m temperature

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urban_avg S1 Fei_mod UH_mod

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rural_avg S1 Fei_mod UH_mod

Fei Chen urban LU Mod. + Canopy moisture + Emissivity change

Some improvement, but Still some problem.


Original Fei_mod UH_mod-I(Fei_mod+ CM + EM)

12 km Min : low bias in R;U

Max : high bias in U

Min : low bias in R


No min and max bias but somewhat increased PBL hts on Aug. 30 and 31

4 km Min : low bias in R;U


Min : low bias in R



(R: rural areas; U: urban areas)

2-m temperature result

More sensitivity test to fix high max. temperature bias in Urban area at 4-km resolution


2-m temperature

Fei Chen urban LU mod (thermal conductivity only) + Canopy moisture + Emissivity change

Improved over others

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urban_avg S1 Fei_mod UH_mod

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rural_avg S1 Fei_mod UH_mod

Urban CAMS site average

Rural CAMS site average

University of HoustonIMAQS2-m temperature;

4-km domain

Fei Chen urban LU Modification (heat capacity only), + Canopy water + rural Emissivity change

Summary of MM5/NOAH simulation with added urban canopy moisture.

1. Original NOAH/USGS data for HGA: Urban area was treated as if it were totally covered with impervious surface. Therefore, we have large diurnal variations in temp and very low latent/sensible heat flux ratio in urban areas.

2. Bias in daytime temperature mostly fixed with added canopy water for the urban LU.

3. Min. temperature bias at urban sites was fixed with the heat capacity modification and by emissivity at rural sites

Additional analysis & work needed

1. Need to look at development of daytime wind speed build up.

2. Moisture advection needed to be looked at.

3. Compare with other “sensitivity” studies

-- satellite surface temperature nudging (UAH & TAMU)

-- modified PBL algorithm, etc (ATMET)

-- Kiran’s GEM?

Future MM5 work at IMAQS

• Continue to test MM5/NOAH

need to continue to improve meteorological simulations especially for August 30 and 31 for wind development and moisture advection

• Use improve land use and land cover data

- compare w/ TCEQ LU/LC used for biogenic emissions

- develop methods to incorporate fractional LU/LC effects

• Future study will focus on the urban canopy parameterization (UCP) in meteorological modeling. By implementing the urban canopy parameterization into MM5, the meteorological simulation will be expected to have more accurate results on urban area simulation.

University of HoustonIMAQS12-km CMAQ results

Urban : 10 sites Rural : 18 sitesdominant landuse data used in MM5

University of HoustonIMAQS12-km CMAQ results

University of Houston IMAQS MM5 Meteorological Modeling for Houston-Galveston Area Air Quality...

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