TSD-1a 

Meteorological Modeling of 2002 using Penn State/NCAR 

5th Generation Mesoscale Model (MM5) 

Bureau of Air Quality Analysis and Research 

Division of Air Resources 

New York State Department of Environmental Conservation 

Albany, NY 12233 

January 10, 2008 
Meteorological Modeling using Penn State/NCAR 5th Generation Mesoscale Model 

(MM5)

Version 3.6 of MM5 was used to generate annual 2002 meteorology for the Mid-Atlantic 

Northeast Visibility Union (MANE-VU) through the Modeling Committee of Ozone 

Transport Commission (OTC). Prof. Dalin Zhang of the University of Maryland (UMD) 

performed the MM5 simulations in consultation with NYSDEC staffs. The model was 

applied in Lambert conformal map projection and utilized MPP Version developed for 

clusters. The two-way nested domain consisted of a coarse (36km) and fine (12km) mesh 

corresponding to 149x129 and 175x175 grids, respectively, in this application (see Figure 

1). 

The Lambert projection used in this work followed the Regional Planning Organization 

(RPO) national domain setup with the center at (40oN, 97oW) and parallels at 33oN and 

45oN. Map projection parameters in reference to the projection center point are as 

follows: Southwest corner for the 36 km grid is at (-2664km, -2304km) and the northeast 

corner at (2664km, 2304km). In the case of the 12km grid, the southwest corner is at 

(252km, -900km) and the northeast corner at (2340km, 1188km). In the vertical direction, 

the terrain following σ-coordinate system was used with the pressure at each σ-level 

determined from a reference state that is estimated using the hydrostatic equation from a 

given sea-level pressure and temperature with a standard lapse rate. There are 30 

unevenly spaced σ levels, giving 29 vertical layers, with higher resolution within the 

planetary boundary layer (PBL). The σ levels are: 

1.0000, 0.9974, 0.9940, 0.8980, 0.9820, 0.9720, 0.9590, 0.9430, 0.9230, 0.8990, 

0.8710, 0.8390, 0.8030, 0.7630, 0.7180, 0.6680, 0.6180, 0.5680, 0.5180, 0.4680, 

0.3680, 0.3180, 0.2680, 0.2180, 0.1680, 0.1230, 0.0800, 0.0400, 0.0000 

The surface layer was set at about 10m, the level at which surface winds were typically 

observed, and the model top was set at 50hPa with a radiative top boundary condition. 

The time steps for the 36km and 12km domains were 75 and 25 seconds, respectively. 

The important model physics options used for this MM5 simulation include: 

• Kain-Fritsch (1993) convective scheme for both 36- and 12-km domains 

• Explicit moisture scheme (without the mixed phase) containing prognostic 

equations for cloud water (ice) and rainwater (snow) (Dudhia 1989; Zhang 1989) 

• Modified version of the Blackadar planetary boundary layer (PBL) scheme 

(Zhang and Anthes 1982; Zhang and Zheng 2004) 

• Simple radiative cooling scheme (Grell et al. 1994) 

• Multi-layer soil model to predict land surface temperatures using the surface 

energy budget equation (Dudhia 1996) 

Note that the Blackadar PBL scheme has been modified in order to correct the phase shift 

of surface wind speed and temperature diurnal cycle, following a study that compared 

five different PBL schemes: the Gayno-Seaman TKE scheme (Shafran et al. 2000), Burk2 
Thompson (1989), Blackadar (Zhang and Anthes 1982), MRF (Hong and Pan 1996), and 

Mellor-Yamada-Jajic (Mellor and Yamada 1974; Jajic 1990, 1994). The details of the 

study can be found at Zhang and Zheng (2004). 

Nudging Processes 

The MM5 provides options for nudging observations for each domain during the model 

integration process (Stauffer and Seaman, 1990; Stauffer et al. 1991). The Eta analyses of 

upper-air winds, temperature and water-vapor mixing ratio as well as their associated surface 

fields were used for nudging every 6 hours, and the Eta surface wind fields blended with 

surface wind observations were used to nudge every 3 hours. While only the surface winds 

were nudged, their influences could extend into the PBL as well (see Stauffer et al. 1991). 

Based on UMD’s prior experience in numerical experiments, the following nudging 

coefficients have been used: 

• Upper-air wind fields: 5. 0E-4s-1 for Domain 1 (36km), and 2. 5E-4s-1 for Domain 2 

(12km); 

• Upper-air temperature fields: 1.0E-5s-1 for both Domains; 

• Surface winds: 5. 0s-1E-4s-1 for Domain 1, and 2.5E-4s-1 for Domain 2; and 

• Surface temperature and moisture: not nudged due to instability consideration. 

ASSESSMENT

National Weather Service (NWS) and CASTNet data – Surface temperature, Wind 

Speed, and Humidity 

NWS (TDL) and CASTNet (www.epa.gov/castnet/) surface measurements of 

temperature, wind speed, and humidity (note there were no humidity measurements for 

CASTNet) were used to compare with the MM5 outputs. The evaluation was performed 

with METSTAT program developed by Environ Corporation 

(www.camx.com/files/metstat.15feb05.tar.gz) When comparing to NWS data, the 

METSTAT interpolates the first layer MM5 (at 10m height) temperature and humidity 

data to a height of 2m, the level that corresponds to the NWS measurement of these 

parameters, but no interpolation was made for wind speed and direction. In the case of 

CASTNet surface measurements, no interpolations were made as CASTNet data were 

reported at 10m height. In this analysis, no exclusion was made for calm conditions. The 

reported calm winds (zero wind speed measured) were treated as is in this evaluation 

effort. The METSTAT calculated standard statistical measures – average, bias, error and 

index of agreement between the measured and predicted parameters. Table 1 summarizes 

the MM5 average bias for each month for wind speed, wind direction, temperature, and 

humidity by comparing data from NWS and CASTNet networks. The humidity data is 

only available for NWS network. In general, there is no systematic bias between winter 

and summer seasons for MM5 in terms of wind speed, wind direction and temperature. 

However, MM5 showed dry bias in the summer and wet bias in the winter when 

compared with humidity data from NWS. 

3 
Figure 2a and 2b display the time series comparison of wind speed between MM5 and 

measured data from NWS and CASTNet networks for winter months (January, February 

and December) and summer months (June, July and August), respectively. MM5 

underpredicted NWS and overpredicted CASTNet daytime peak wind speed, while MM5 

appears to track quite well the nighttime wind speed minimum for CASTNet and 

overpredicted nighttime wind speed minimum for the NWS data. MM5 performed quite 

well in capturing magnitude and diurnal timing for temperature from both NWS and 

CASTNet data (Figures 3a and 3b). It should be pointed out that there are differences in 

how the meteorological information is collected and reported by the two networks and as 

computed in MM5. The CASTNet measurements are based on hourly averaged wind 

speed while NWS reports 2min average at 10min before the hour, whereas MM5 

predictions are reflective of the last time-step of the hour of computation. In the case of 

humidity (Figure 4), MM5 tracked the NWS observed humidity trend well, but exhibits 

dry bias for summer season and wet bias for winter season and misses the observed semidiurnal cycles. Comparisons for the whole year of 2002 including bias and root mean 

square error from both NWS and CASTNet are available on request from NYSDEC. 

The above assessment is based on domain-wide averages to provide an overall response 

of the model. Another way of assessing the model is to examine the spatial distribution of 

correlation between the measured and predicted parameters at each monitor. Figures 5a 

and 5b display such a comparison for wind speed and temperature over winter months 

and summer months, respectively. For the wind speed (Figure 5a), the correlation is in 

the range of 0.8 to 0.9 for winter months and 0.7 to 0.8 for summer months. For the 

temperature (Figure 5b), the correlation is above 0.95 for summer months, slightly higher 

than winter months. The correlation for humidity (Figure 5c) is in the range of 0.8 to 0.9 

for both winter and summer months. These correlations indicate that MM5 simulation 

has captured both the diurnal and synoptic scale variations. Detailed plots of this 

comparison are available on request from NYSDEC. 

Vertical Profiler – Winds 

The Wind-Profiler network measurements along the U. S. East Coast (www.madisfsl.org/cap) were used to evaluate the vertical profiles from MM5. There are twelve 

wind-profiler measurement stations from which data were available for comparison. For 

convenience of comparison, the wind-profiler measurements were interpolated to the 

MM5 vertical levels. The approach used was simple interpolation between two adjacent 

wind-profiler layers to the MM5 vertical level, and was limited to that reported by the 

profiler measurement. The focus of the comparison was to assess if MM5 was able to 

capture the measured vertical structure, and for this we used the observed Low Level Jet 

(LLJ) as an indicator. The comparison was performed for June, July and August 2002. In 

general it is found that MM5 captures the profiler measured vertical wind field structure 

reasonably well. Figure 6 displays an example of the MM5 and wind profiler comparison 

for the August 2002 episode at Richmond, VA and Concord, NH. MM5 predicted weaker 

LLJ winds compared to those based on the wind-profiler measurements. The detailed 

plots of this comparison are available on request from NYSDEC. 

4 
Cloud Cover – Satellite cloud image 

Cloud information derived from satellite image data 

(www.atmos.umd.edu/~srb/gcip/webgcip.htm) were used to assess the MM5 prediction 

of cloud cover. The 0.5o

 by 0.5o resolution of the satellite data were interpolated into the 

12km MM5 grid for comparison. The MM5 total cloud fraction was estimated by MCIP 

based on the MM5’s low cloud, middle cloud and high cloud predictions. In general, 

MM5 seems to capture the satellite cloud pattern well but underestimates the satellite 

cloud fraction (see Figure 7a and 7b as examples), which may in part be due to the coarse 

resolution of the satellite cloud data. 

Precipitation comparison 

The monthly total observed precipitation data were constructed from 1/8-degree daily 

precipitation analysis data (http://data.eol.ucar.edu/codiac/dss/id=21.093) produced by 

Climate Prediction Center, based on 7,000-8,000 hourly/6-hourly gauge reports and 

radar). The MM5 monthly total precipitation was estimated from the MM5 predicted 

convective and non-convective rainfall and summed up for each month. In general, MM5 

captured the observed spatial patterns (see examples of Figures 8a and 8b). For winter 

months, MM5 performed well for February (Figure 8a) but underpredicted for 

November. For the summer months, MM5 performed well for May and September, but 

no so well for June, July and August (See Figure 8b), that may reflect the summertime 

convective rain activities are not captured by MM5. 

Calm Conditions 

Calm conditions are defined as observed wind speed of zero knots and wind direction as 

0o. It would be useful to assess how MM5 performs under observed calm conditions, 

because of potential pollutant buildup that could occur under such conditions. Table 2a 

and 2b list the summary of the percentage of calm condition at each hour for the February 

and August 2002, respectively from the NWS data within the 12km domain. It is apparent 

from the Table that the calm conditions occur primarily during the night and early 

morning hours, from 23Z (7 p.m. EDT) to 15Z (11 a.m. EDT) with a peak at around 10Z 

(6 a.m. EDT). August had much higher percentage of calm condition than February. To 

assess MM5 performance, the observed and MM5 predicted wind speeds were divided 

into calm and non-calm according to observed wind speed. In general MM5 

underpredicted the observed non-calm conditions for both February and August (Table 2a 

and 2b). Figure 9 displays such a comparison of the MM5 predicted wind speed to the 

observed wind speed under the calm and non-calm conditions for the month of August 

2002. For the “calm” group, the average wind speed for MM5 varies from 1 m/s during 

the night and early morning hours and over 1.5 m/s during the day. MM5 is overpredicting during observed calm wind conditions. There are local minima every 3 hours, 

due to the surface observed wind speed nudging in MM5. In contrast under the non-calm 

conditions, MM5 underpredicts by about 0.5 m/s for all hours with noticeable local 

maximum happening at the nudging hours. The MM5 nudging process would pull 

5 
predictions toward the measured data, while the underprediction of MM5 for the noncalm conditions may due to the adopted PBL scheme in this simulation. 

Summary 

In this study, we performed an assessment of the MM5 simulation to measured data, both 

with the surface measurement networks as well as with information from the vertical 

wind profilers and satellite cloud images. While there are no specific recommended 

procedures identified for this assessment, similar approaches have been used elsewhere 

(Dolwick 2005, Baker 2004, and Johnson 2004). Traditionally, the NWS surface 

measurements are used for such a comparison. Since NWS data had been used through 

nudging processes in developing the MM5 simulation, the comparisons should not be far 

removed from each other. In this study, we extended the evaluation by using CASTNet 

measurements that were not used in the nudging of MM5 simulation. Thus comparison 

with CASTNet data provides for an independent assessment and should complement the 

comparison with NWS data. We also compared the MM5 results with the wind profiler 

data and cloud data derived from satellite images to diagnose if the MM5 simulation is 

yielding the right dynamics in the vertical. The analyses shows that in general, the 

performance of the MM5 is reasonable both at the surface and in the vertical, thereby 

providing confidence in the use of these data in the CMAQ simulations. 

 

References 

Baker, K. 2004: www.ladco.org/tech/photo/photochemical.html

Burk, S. D. and W. T. Thompson, 1989: A vertically nested regional numerical weather 

prediction model with second-order closure physics. Mon. Wea. Rev., 117, 2305–2324. 

Dudhia, J., 1989: Numerical study of convection observed during the winter monsoon 

experiments using a mesoscale two-dimensional model. J. Atmos. Sci., 46, 3077–3107. 

Dudhia, J., 1996: A multi-layer soil temperature model for MM5. Preprints, 6th Annual 

MM5 Users Workshop, Boulder, CO. 

Dolwick, P. 2005: 

http://cleanairinfo.com/modelingworkshop/presentations/MPE_Dolwick.pdf

Grell, G. A., J. Dudhia, and D. R. Stauffer 1994: A description of the fifth-generation 

Penn State/NCAR Mesoscale Model (MM5). NCAR Tech. Note NCAR/TN-398 1 STR, 

122 pp. 

Hong, S.-H., and H.-L. Pan, 1996: Nonlocal boundary layer vertical diffusion in a 

medium-range forecast model. Mon. Wea. Rev., 124, 2322–2339. 

Jajic, Z. I., 1990: The step-mountain coordinate: Physical package. Mon. Wea. Rev., 

118, 1429-1443. 

6 
Jajic, Z. I., 1994: The step-mountain Eta coordinate model: Further development of the 

convection, viscous sublayer and turbulent closure schemes. Mon. Wea. Rev., 122, 927-

945. 

Johnson, M. 2004: www.ladco.org/tech/photo/photochemical.html

Kain, J.S., and J.M. Fritsch, 1993: Convective parameterization for mesoscale models: 

The Kain-Fritsch scheme Cumulus Parameterization. Meteor. Monogr., 46, Amer. 

Meteor. Soc., 165-170. 

Mellor, G.L., and T. Yamada, 1974: A hierarchy of turbulence closure models for 

planetary boundary layers. J. Atmos. Sci., 31, 1791–1806. 

Shafran, P.C., N.L. Seaman, and G.A. Gayno, 2000: Evaluation of numerical 

predictions of boundary layer structure during the Lake Michigan ozone study. J. Appl. 

Meteor., 39, 412-426. 

Stauffer, D. R., N. L. Seaman and F. S. Binkowski 1991: Use of four-dimensional data 

assimilation in a limited-area mesoscale model. Part II: Effects of data assimilation 

within the planetary boundary layer. Mon. Wea. Rev., 119, 734-754. 

Stauffer, D.R. and N.L. Seaman, 1990: Use of four-dimensional data assimilation in a 

limited-area mesoscale model. Part I: Experiments with synoptic-scale data. Mon. 

Wea. Rev., 118, 1250-1277. 

Zhang, D.-L., 1989: The effect of parameterized ice microphysics on the 

simulation of vortex circulation with a mesoscale hydrostatic model. Tellus, 41A, 132-

147. 

Zhang, D.-L, and R. A. Anthes, 1982: A high-resolution model of the planetary 

boundary layer-sensitivity tests and comparisons with SESAME-79 data. J. Appl. 

Meteor., 21, 1594–1609. 

Zhang, D.-L, and W.-Z. Zheng, 2004: Diurnal cycles of surface winds and temperatures 

as simulated by five boundary-layer parameterizations. J. Appl. Meteor., 43, 157-169. 

7 
Table 1: Average bias of wind speed, wind direction, temperature, and humidity of MM5 

in comparing with observed data from TDL and CASTNet networks for each month in 

2002 

Month Wind Speed 

(TDL / CASTNet) 

Wind Direction 

(TDL / CASTNet) 

Temperature 

(TDL / CASTNet) 

Humidity 

TDL 

January -0.53 / 0.34 3.12 / 2.54 -1.18 / -1.25 0.45 

February -0.56 / 0.31 3.31 / 0.88 -1.00 / -0.65 0.48 

March -0.59 / 0.31 3.48 / 1.93 -0.72 / -0.35 0.52 

April -0.55 / 0.38 3.61 / 2.49 -0.48 / -0.52 0.52 

May -0.52 / 0.44 3.53 / 2.33 -0.18 / 0.67 -0.02 

June -0.56 / 0.28 3.89 / 3.33 -0.12 / 1.03 -0.33 

July -0.58 / 0.31 3.62 / 1.44 -0.34 / 0.34 -0.55 

August -0.61 / 0.24 2.74 / 2.34 -0.42 / 0.32 -0.23 

September -0.54 / 0.30 3.31 / 3.01 -0.54 / 0.76 0.03 

October -0.56 / 0.32 2.81 / 1.39 -0.79 / -0.56 0.15 

November -0.57 / 0.37 2.28 / 2.35 -1.35 / -1.25 0.34 

December -0.59 / 0.39 3.41 / 2.69 -1.20 / -1.17 0.34 

8 
Table 2a: Measured calm and non-calm occurrences over the modeling domain during 

February 2002 based on NWS data 

Hour 

(UTC) 

Obs 

Not 

Calm 

Obs 

Calm 

Obs 

Total 

Percent 

Calm 

(%) 

TDL 

Avg 

WinSpd 

Not 

Calm 

MM5 

Avg 

WinSpd 

Not 

Calm 

0 17266 2711 19977 13.6 4.28 3.84 

1 17270 3324 20594 16.1 4.30 3.82 

2 17051 3421 20472 16.7 4.30 3.75 

3 16878 3499 20377 17.2 4.32 3.79 

4 16401 3513 19914 17.6 4.33 3.78 

5 16127 3532 19659 18.0 4.28 3.75 

6 15914 3645 19559 18.6 4.26 3.81 

7 15841 3703 19544 18.9 4.23 3.75 

8 15784 3783 19567 19.3 4.20 3.71 

9 15752 3857 19609 19.7 4.19 3.73 

10 15630 3932 19562 20.1 4.18 3.70 

11 15911 4020 19931 20.2 4.16 3.72 

12 16451 4104 20555 20.0 4.21 3.82 

13 16844 3891 20735 18.8 4.28 3.86 

14 17779 2945 20724 14.2 4.62 4.00 

15 18741 1822 20563 8.9 4.98 4.37 

16 18740 1337 20077 6.7 5.21 4.66 

17 19079 1106 20185 5.5 5.38 4.83 

18 19158 954 20112 4.7 5.46 4.93 

19 19380 880 20260 4.3 5.49 4.91 

20 19545 883 20428 4.3 5.47 4.75 

21 19648 859 20507 4.2 5.33 4.46 

22 19576 1027 20603 5.0 5.03 4.02 

23 18941 1772 20713 8.6 4.57 3.79 

9 
Table 2b: Measured calm and non-calm occurrences over the modeling domain during 

August 2002 based on NWS data 

Hour 

(UTC) 

Obs 

Not 

Calm 

Obs

Calm 

Obs 

Total 

Percent 

Calm 

(%) 

TDL 

Avg 

WinSpd

Not 

Calm 

MM5 

Avg 

WinSpd

Not 

Calm 

0 18209 3924 22133 17.7 3.14 2.56 

1 16531 6026 22557 26.7 2.85 2.45 

2 15604 6929 22533 30.8 2.79 2.33 

3 14983 7245 22228 32.6 2.81 2.33 

4 14309 7540 21849 34.5 2.80 2.28 

5 14073 7735 21808 35.5 2.79 2.24 

6 13934 7949 21883 36.3 2.78 2.29 

7 13792 8040 21832 36.8 2.76 2.23 

8 13542 8273 21815 37.9 2.75 2.22 

9 13542 8385 21927 38.2 2.74 2.28 

10 13708 8591 22299 38.5 2.72 2.25 

11 14139 8693 22832 38.1 2.74 2.25 

12 15297 7690 22987 33.5 2.89 2.33 

13 17336 5192 22528 23.0 3.14 2.41 

14 18522 3439 21961 15.7 3.39 2.63 

15 18755 2617 21372 12.2 3.60 2.98 

16 19169 2015 21184 9.5 3.79 3.15 

17 19555 1617 21172 7.6 3.97 3.22 

18 19982 1430 21412 6.7 4.08 3.38 

19 20149 1389 21538 6.4 4.16 3.43 

20 20565 1288 21853 5.9 4.14 3.41 

21 20518 1383 21901 6.3 4.06 3.41 

22 20672 1556 22228 7.0 3.88 3.12 

23 20231 2292 22523 10.2 3.56 2.74 

10
Figure 1: OTC MM5 modeling domain with areal extent of 12km and 36km grids 

11
W in d S p eed - T D L

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Figure 2a: Wind speed comparison for winter months - January, February, and 

December, 2002. The upper panel is the comparison between MM5 and NWS data, and 

the lower panel is the comparison between MM5 and CASTNet data. 

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Figure 2b: Wind speed comparison for summer months - June, July, and August, 2002. 

The upper panel is the comparison between MM5 and NWS data, and the lower panel is 

the comparison between MM5 and CASTNet data. 

13
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Figure 3a: Temperature comparison for winter months - January, February, and 

December, 2002. Upper panel is the comparison between MM5 and NWS data, and the 

lower panel is the comparison between MM5 and CASTNet data. 

14
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Figure 3b: Temperature comparison for summer months - June, July, and August, 2002. 

The upper panel is the comparison between MM5 and NWS data, and the lower panel is 

thew comparison between MM5 and CASTNet data. 

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Figure 4: Humidity comparison for winter months - January, February, and December, 

2002, (top panel), and summer months - June, July, and August, 2002 (bottom panel). 

16
Figure 5a: Spatial correlation estimates between MM5 and NWS data for wind speed 

for winter months – January to March, 2002 (top panel) and summer months - 

May to September, 2002 (bottom panel). 

17
Figure 5b: Spatial distribution of correlation coefficients for Temperature between 

 MM5 and NWS data for winter months – January to March, 2002 (top panel), 

 and summer months - May to September, 2002 (bottom panel). 

18
Figure 5c: Spatial distribution of correlation coefficients for Humidity between 

 MM5 and NWS data for winter months – January to March, 2002 (top panel), 

 and summer months - May to September, 2002 (bottom panel). 

19
Richmond, VA 

igure 6: MM5 and Wind profiler comparison for August 6 to 17, 2002 at Richmond, VA 

nd Concord, NH. The upper and lower panes at each station are for MM5 and profiler, 

respectively. The abscissa represents day and the ordinate the height (m). 

Concord, NH 

F

a

20
Figure 7a: Observed Satellite and MM5 cloud images for August 14, 2002 at 0700 EST 

21
Figure 7b: Observed Satellite and MM5 cloud images for January 24, 2002 at 1200 EST 

22
Figure 8a: Measured and MM5 predicted precipitation over the domain for the month of 

February 2002. 

23
Figure 8b: Measured and MM5 predicted precipitation over the domain for the month of 

August 2002 

24
0

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TIME

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MM5AvgNC

MM5AvgC

Figure 9: Comparison of averaged wind speed between MM5 and observed under calm 

(C) and non-calm (NC) conditions. 

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