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Numerical Experimental Analysis Data for the Year of 2002

Da-Lin Zhang and Shunli Zhang

Department of Atmospheric and Oceanic Science, University of Maryland

College Park, MD 20742

Tel. (301) 405-2018; Email: dalin@atmos.umd.edu

1. Introduction

A total of 128 numerical experiments, in 3-day segments, for the year of 2002 (i.e.,

from 0000 UTC 14 December 2001 to 0000 UTC 1 January 2003) have been conducted 

on our newly purchased Cluster using the nested-grid (36/12 km) Version 3.6 of the

PSU/NCAR mesoscale model (i.e., MM5). The NCEP’s Eta analysis with 40-km

resolution was used to initialize the model integrations and specify the outmost lateral

boundary conditions. To minimize the influence of model errors but retain as many 

mesoscale circulations as possible, the dynamical nudging or four-dimensional data

assimilation (FDDA) technique was adopted to include observations of the surface winds

and upper-level meteorological information. More attention was paid to the accuracy of

surface winds due to their important roles in ozone transport. The model integrations

were re-initialized every 3.5 days, allowing a 12-h period for the model spin-up (i.e., the

first 12-h data could be truncated in the application of the datasets). Hourly model

outputs were archived for the period of 12.5 months. This four-dimensional high

resolution (in time and space) analysis dataset so assimilated was generated for air quality

modeling and for regional haze studies. These integrations yielded a total of 830 Gbytes

analysis data.

2. Model description

The Version 3.6 of MM5 with a Lambert conformal map projection, an MPP

Version developed for clusters, was used for this project. The (x, y) dimensions of the

coarse (36 km) and fine (12 km) mesh domains are 149 x 129 and 175 x 175,

respectively. The vertical discretion uses terrain-following σ-coordinates, but the pressure

at the σ-levels are 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 uneven σ levels, giving 29 layers, with higher resolution in the

planetary boundary layer (PBL). The σ levels are placed at the following values:

1.000, 0.9974, 0.994, 0.989, 0.9820, 0.972, 0.959, 0.943, 0.923, 0.8990,

0.871, 0.839, 0.803, 0.763, 0.718, 0.668, 0.618, 0.568, 0.518, 0.468, 0.418,

0.368, 0.318, 0.268, 0.218, 0.168, 0.123, 0.080, 0.040, 0.00

The surface layer is defined at an altitude of about 10 m, the level at which surface winds

are typically observed. The model top is set at 50 hPa with a radiative upper boundary

condition. The time steps for the 36 km and 12 km resolution domains are 75 and 25

seconds, respectively.

Figs. 1 and 2 show the nested-grid (36/12 km) domain and the fine-mesh domain,

respectively, that were used for this project.

Domain 1 is centered at 400N latitude and 970W longitude with a grid size of 36 

km, and it covers the U.S. continents, Mexico, Canada, the Gulf of Mexico, and part of

the East Pacific and West Atlantic oceans.
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Fig. 1 The coarse-mesh (36 km) domain. Fig. 2 The fine-mesh (12-km) domain.

Domain 2 uses a grid size of 12 km, and it covers the northeastern, central and

southeastern US as well as Southeastern Canada.

The important model physics of the MM5 used for this project include:

(i) The latest version of the Kain-Fritsch (1993) convective scheme was used for

both 36- and 12-km resolution domains;

(ii) An explicit moisture scheme (without the mixed phase) containing prognostic

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

(iii) A modified version of the Blackadar planetary boundary layer (PBL) scheme

(Zhang and Anthes 1982; Zhang and Zheng 2004);

(iv) A simple radiative cooling scheme (Grell et al. 1997);

(v) A 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 reproduce the

diurnal cycles of surface winds and temperatures, after performing a comparative study

of the following five different PBL schemes: the Gayno-Seaman TKE scheme (Shafran et

al. 2000), Burk-Thompson (1989), Blackadar (Zhang and Anthes 1982), MRF (Hong and 

Pan 1996), and Miller-Yamada-Jajić (Miller and Yamada 1974; Jajić 1990, 1994). These

changes are given as follows (see Zhang and Zheng 2004 for more detail):

• K-coefficient is determined by the Richardson number according to Zhang and

Anthes (1982), where the critical Richardson number is set to be 0.25. In addition, the

mixing length is set to be the thickness of the model layer.

• Use of potential temperature rather than virtual potential temperature to calculate

the bulk Richardson number Rb.

3. Nudging Processes

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

course of model integration (Stauffer and Seaman 1990; Stauffer et al. 1991). The Eta
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analyses of upper-air winds, temperature and water-vapor mixing ratio as well as their

associated surface fields, were nudged every 6 hours, and the higher-resolution surface

wind field was nudged every 3 hours. While only the surface winds were nudged, their

influences could be extended into the PBL (see Stauffer et al. 1991).

Based on our previous experience with many numerical experiments, the following

nudging coefficients have been used:

• Upper-air wind fields: 5.0E-4 for Domain 1, and 2.5E-4 for Domain 2;

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

• Surface winds: 5.0E-4 for Domain 1, and 2.5E-4 for Domain 2; and

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

4. Model initialization

The model is initialized with NCEP's Eta model analysis (ds609.2) as a first guess

that is then enhanced by observations at upper levels and the surface.

(i) NCEP’s ADP global upper-air observations (NCAR archive ds353.4) are used to

further enhance the upper-level Eta analysis.

(ii) The following two sets of surface observations have been introduced into the

model initial state to improve the Eta analysis of surface wind fields:

• The NCEP’s ADP global surface wind observations (NCAR archive ds464.0):

This dataset provides 6-hourly surface observations over land (i.e., at 0000, 0600, 1200,

1800 UTC) in one stream, and 3-hourly (i.e., at 0300, 0900, 1500, 2100 UTC) over both 

land and ocean surfaces in another stream.

• The TDL’s U.S. and Canadian surface observations (NCAR archive ds472.0): This

dataset provides hourly surface observations over the U.S. and Canadian regions.

The Eta model analysis has a domain covering the entire U.S. continents with a 40-

km horizontal resolution. It includes the following types of observations:

• Rawinsonde mass and wind;

• Piball winds;

• Dropwindsondes;

• Wind profiles;

• Surface land temperature and moisture;

• Oceanic surface data (ship and buoys);

• Aircraft winds;

• Satellite cloud-drift winds;

• Oceanic TOVS thickness retrievals;

• GOES and SSM/I precipitable water retrievals.

The Cressman objective analysis option was used to enhance the Eta analysis.

However, we analyzed the results and found that it still could not reproduce the right

diurnal cycle of surface winds and temperatures. Thus, we repeated the Cressman

procedures three more times to enhance the surface analyses. Results indicate that this

procedure significantly improved the results.
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Note that (i) because of the initial model spin-up, we recommend that the first 12-h

model integration of each run be discarded; and (ii) because the synoptic-scale upper-air

winds and temperatures were nudged, the flow fields above the PBL might contain less

smaller-scale features (e.g., in low-level jets, mountain-forced perturbations and etc.).

5. Data Archive

As mentioned above, we have conducted a total of 128 experiments, in 3-day 

segments, from 0000 UTC 14 December 2001 to 0000 UTC 1 January 2003. The

following table lists the experiments and their corresponding integration periods:

Exp. # Period Exp. # Period

1 00/15/12-00/18/12*01 2 00/18/12-12/21/12*01

3 00/21/12-00/24/12*01 4 00/24/12-00/27/12*01

5 00/27/12-00/30/12*01 6 00/30/12-00/02/01*02

7 00/02/01-00/05/01*02 8 00/05/01-00/08/01*02

9 00/08/01-00/11/01*02 10 00/11/01-00/14/01*02

11 00/14/01-00/17/01*02 12 00/17/01-00/20/01*02

13 00/20/01-00/23/01*02 14 00/23/01-00/26/01*02

15 00/26/01-00/29/01*02 16 00/29/01-00/01/02*02

17 00/01/02-00/04/02*02 18 00/04/02-00/07/02*02

Exp. # Period Exp. # Period

19 00/07/02-00/10/02*02 20 00/10/02-00/13/02*02

21 00/13/02-00/16/02*02 22 00/16/02-00/19/02*02

23 00/19/02-00/22/02*02 24 00/22/02-00/25/02*02

25 00/25/02-00/28/02*02 26 00/28/02-00/03/03*02

27 00/03/03-00/06/03*02 28 00/06/03-00/09/03*02

29 00/09/03-00/12/03*02 30 00/12/03-00/15/03*02

31 00/15/03-00/18/03*02 32 00/18/03-00/21/03*02

33 00/21/03-00/24/03*02 34 00/24/03-00/27/03*02

35 00/27/03-00/30/03*02 36 00/30/03-00/02/04*02

37 00/02/04-00/05/04*02 38 00/05/04-00/08/04*02

39 00/08/04-00/11/04*02 40 00/11/04-00/14/04*02

41 00/14/04-00/17/04*02 42 00/17/04-00/20/04*02

43 00/20/04-00/23/04*02 44 00/23/04-00/26/04*02

45 00/26/04-00/29/04*02 46 00/29/04-00/02/05*02

47 00/01/05-00/04/05*02 48 00/04/05-00/07/05*02

49 00/07/05-00/10/05*02 50 00/10/05-00/13/05*02

51 00/13/05-00/16/05*02 52 00/16/05-00/19/05*02

53 00/19/05-00/22/05*02 54 00/22/05-00/25/05*02

55 00/25/05-00/28/05*02 56 00/28/05-00/31/05*02

57 00/31/05-00/03/06*02 58 00/03/06-00/06/06*02

59 00/06/06-00/09/06*02 60 00/09/06-00/12/06*02

61 00/12/06-00/15/06*02 62 00/15/06-00/18/06*02

63 00/18/06-00/21/06*02 64 00/21/06-00/24/06*02

65 00/24/06-00/27/06*02 66 00/27/06-00/30/06*02
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67 00/30/06-00/03/07*02 68 00/03/07-00/06/07*02

69 00/06/07-00/09/07*02 70 00/09/07-00/12/07*02

71 00/12/07-00/15/07*02 72 00/15/07-00/18/07*02

73 00/18/07-00/21/07*02 74 00/21/07-00/24/07*02

75 00/24/07-00/27/07*02 76 00/27/07-00/30/07*02

77 00/30/07-00/02/08*02 78 00/02/08-00/05/08*02

79 00/05/08-00/08/08*02 80 00/08/08-00/11/08*02

81 00/11/08-00/14/08*02 82 00/14/08-00/17/08*02

83 00/17/08-00/20/08*02 84 00/20/08-00/23/08*02

85 00/23/08-00/26/08*02 86 00/26/08-00/29/08*02

87 00/29/08-00/01/09*02 88 00/01/08-00/04/09*02

89 00/04/09-00/07/09*02 90 00/07/09-00/10/09*02

91 00/10/09-00/13/09*02 92 00/13/09-00/16/09*02

93 00/16/09-00/19/09*02 94 00/19/09-00/22/09*02

95 00/22/09-00/25/09*02 96 00/25/09-00/28/09*02

97 00/28/09-00/01/10*02 98 00/01/10-00/04/10*02

99 00/04/10-00/07/10*02 100 00/07/10-00/10/10*02

101 00/10/10-00/13/10*02 102 00/13/10-00/16/10*02

103 00/16/10-00/19/10*02 104 00/19/10-00/22/10*02

Exp. # Period Exp. # Period

105 00/22/10-00/25/10*02 106 00/25/10-00/28/10*02

107 00/28/10-00/31/10*02 108 00/31/10-00/03/11*02

109 00/03/11-00/06/11*02 110 00/06/11-00/09/11*02

111 00/09/11-00/12/11*02 112 00/12/11-00/15/11*02

113 00/15/11-00/18/11*02 114 00/18/11-00/21/11*02

115 00/21/11-00/24/11*02 116 00/24/11-00/27/11*02

117 00/27/11-00/30/11*02 118 00/30/11-00/03/12*02

119 00/03/12-00/06/12*02 120 00/06/12-00/09/12*02

121 00/09/12-00/12/12*02 122 00/12/12-00/15/12*02

123 00/15/12-00/18/12*02 124 00/18/12-00/21/12*02

125 00/21/12-00/24/12*02 126 00/24/12-00/27/12*02

127 00/27/12-00/30/12*02 128 00/30/12-00/02/01*03

The datasets listed above include the MM5 outputs from Domain 1 (36 km) and

Domain 2 (12 km), the analysis data used for FDDA, and initial and lateral boundary

conditions. If necessary, any of the experiments listed above could be re-run. The MM5 

outputs include the three-dimensional fields of temperature, horizontal winds, vertical

motion, pressure perturbations, moisture, cloud water/rain water/ice water/snow water

mixing ratio, and radiation tendency; and the two-dimensional fields of the map-scale

factor, longitude and latitude, Coriolis parameter, land use category, terrain height, PBL

depth, accumulated convective/non-convective precipitation, surface sensible/latent heat

flux. A FORTRAN program to read the datasets has also been included.

6. Acknowledgments
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This project was funded by Maryland’s Department of Environment (MDE) and

Northeast States for Coordinated Air Use Management, Inc. (NESCAUM). New York

State Department of Environmental Conservation (NYDEC) has evaluated the MM5’s

performance with TDL and CASTNet measurements for the summer-season episodes of

6 – 16 August 2002 before the production of a complete 5-month simulation from 1 May 

to 30 September 2002. Similarly, NESCAUM evaluated the MM5 simulations of 23 – 29

January 2002 before the simulation of the winter-season episodes and the remaining

annual model simulations. We are very grateful to Gopal Sistla, Mike Ku, and Winston

Hao of NYSDEC, and Shan He and Gary Kleiman of NESCAUM for their careful

evaluations of the MM5 performance.

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