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Publication Number: FHWA-RD-03-092
Date: May 2006

Verification of LTPP Virtual Weather Stations Phase I Report: Accuracy and Reliability of Virtual Weather Stations

Task 1: Obtain and Summarize Climatic Data

Verification of LTPP Virtual Weather Stations Phase I Report: Accuracy and Reliability of Virtual Weather Stations

TASK 1: OBTAIN AND SUMMARIZE CLIMATIC DATA

Data Sources

Climatic data needed for the conduct of this project were obtained from various sources and collected into several working databases. Five sources of information were used in this study as follows.

SMP Daily Temperature and Precipitation

The daily temperature and precipitation data for seasonal monitoring sections were taken from the DataPave 2.0 software on CD-ROM. The daily temperature and precipitation data were stored in the SMP_ATEMP_RAIN_DAY table. There were data for 63 SMP sites in this table.

IMS Virtual Weather Estimates in Climatic Module

The monthly and yearly climatic summaries for VWS in the LTPP database were also extracted from DataPave 2.0. The monthly temperature data were stored in table CLM_VWS_TEMP_ MONTH, which contained data for 880 SPS and GPS sites. The daily VWS data, which are kept offline, were obtained from LTPP program customer service (CLM_VWS_DATA_DAILY table).

Automated Weather Stations

Onsite weather stations are installed at several SPS–1, –2, and –8 sites. Data from these weather stations were available in the AWS module of the database included in DataPave 2.0. The daily temperature and precipitation data were extracted from the AWS_DAILY_DATA table, which contained data for 35 SPS sites.

Operating Weather Stations (OWS)

OWS data, stored offline, were obtained from LTPP program customer service and were used in this project (owsdaily.txt file). This file contained daily temperature, precipitation, humidity, and wind data for up to five OWS near each GPS section or SPS site.

National Climatic Data Center Cooperative Data

The weather station data for 1994 through 1996 from the NCDC cooperative program were used to verify daily temperature and precipitation estimates. Data for more than 8000 weather stations existed in this database.

Summary Climatic Databases

After obtaining the needed data files, data were extracted for the desired time period and locations, and were combined into several user-friendly databases for further analysis. Four summary databases were initially developed as explained below.

VWS Daily Database

A database was developed that contained VWS daily data for SMP and AWS sites. The database contained the climatic parameters listed in table 1 (except for the mean daily temperature and snowfall). This database, which contained data for 58 SMP sections (table 2) and 24 AWS sites (table 3) was used for verification of the precision and bias of the VWS data in the LTPP database.

 

Table 1. Climatic data elements included in owsdaily.txt data file.
Data Element Variable Name Units
Daily mean air temperature MEAN_DAY_TEMP ºC
Daily maximum air temperature MAX_DAY_TEMP ºC
Daily minimum air temperature MIN_DAY_TEMP ºC
Daily maximum relative humidity MAX_DAY_HUM %
Daily minimum relative humidity MIN_DAY_HUM %
Daily precipitation DAY_PRECIPITATION mm
Daily snowfall DAY_SNOWFALL mm
Daily mean windspeed MEAN_DAY_WIND_SPD m/s
Daily maximum gust windspeed MAX_DAY_WIND_SPD m/s

mm – millimeters
m/s – meters/second

NCDC Daily Database

A database was developed from the NCDC cooperative weather station data for daily maximum and minimum temperature and precipitation. This database contained data for more than 8000 weather stations and was used for verification of the accuracy of estimated climatic data and for investigating factors affecting VWS estimates.

SMP Daily Database

This database contained daily SMP climatic data, and VWS estimates and OWS data for up to five nearby weather stations. It included maximum and minimum temperatures and precipitation for 58 SMP sections (table 2). The database was used to verify VWS calculations for SMP sites and to study factors affecting climatic estimates for a site.

 

Table 2. List of SMP sections used in this study.
No. State Code SHRP ID Installation Date No. State Code SHRP ID Installation Date
1 1 0101 24-Jul-95 30 32 0204 09-Oct-96
2 1 0102 25-Jul-95 31 33 1001 14-Oct-93
3 4 0113 15-Aug-95 32 35 1112 05-Apr-94
4 4 0114 16-Aug-95 33 36 0801 22-Aug-95
5 4 0215 24-Aug-95 34 36 4018 27-Oct-93
6 4 1024 21-Aug-95 35 37 1028 17-May-95
7 6 3042 12-Jul-95 36 40 4165 29-Mar-94
8 8 1053 01-Jul-93 37 42 1606 09-Aug-95
9 9 1803 19-Aug-93 38 46 0804 14-Jul-94
10 10 0102 04-Oct-95 39 46 9187 18-Jul-94
11 13 1005 07-Aug-95 40 48 1060 30-Nov-93
12 13 1031 02-Aug-95 41 48 1068 01-Nov-93
13 13 3019 31-Jul-95 42 48 1077 25-Oct-93
14 16 1010 30-Sep-93 43 48 1122 22-Nov-93
15 18 3002 07-Sep-95 44 48 3739 06-Dec-93
16 20 4054 24-Aug-95 45 48 4142 08-Nov-93
17 23 1026 15-Sep-93 46 48 4143 17-Nov-93
18 24 1634 11-May-95 47 49 1001 05-Aug-93
19 25 1002 01-Sep-93 48 49 3011 03-Aug-93
20 27 1018 24-Aug-93 49 50 1002 06-Oct-93
21 27 1028 08-Sep-93 50 51 0113 23-Oct-95
22 27 4040 21-Sep-93 51 51 0114 23-Oct-95
23 27 6251 14-Sep-93 52 53 3813 18-Jul-95
24 28 1016 18-Jul-95 53 56 1007 10-Aug-93
25 28 1802 20-Jul-95 54 83 1801 12-Oct-93
26 30 8129 12-Aug-92 55 83 3802 14-Oct-93
27 31 0114 07-Aug-95 56 87 1622 22-Sep-93
28 31 3018 10-Aug-95 57 89 3015 29-Sep-93
29 32 0101 08-Oct-96 58 90 6405 06-Oct-93

AWS Daily Database

A database similar to the SMP daily database was developed for the AWS data. This database had data for 24 sites (table 3) and was used to verify VWS data for sections equipped with AWS.

 

Table 3. List of AWS sites used in the analysis.
No. AWS ID Installation Date Latitude, degrees Latitude, minutes Longitude, degrees Longitude, minutes Elevation, meters
1 010101 07-Feb-95 32 36 85 15 46
2 040100 16-Feb-95 35 24 114 16 1122
3 040200 21-Jul-94 33 27 112 43 334
4 050113 09-May-95 35 42 90 34 14
5 080200 15-Sep-95 39 58 104 44 1552
6 100100 15-Nov-95 38 49 75 26 14
7 120101 11-Jun-96 26 31 80 41 57
8 200100 06-Aug-96 37 36 99 16 737
9 200200 07-Aug-96 38 59 96 59 342
10 300800 17-Nov-94 46 8 112 53 1221
11 310100 07-Aug-96 40 5 97 36 542
12 320200 19-May-95 40 43 117 2 1417
13 350101 21-Sep-95 32 40 107 4 1373
14 350801 09-Aug-96 32 11 108 18 1689
15 360800 22-Nov-95 42 21 77 53 79
16 370200 04-Aug-94 35 50 80 16 233
17 380200 13-Jan-95 46 52 97 13 298
18 390200 08-Sep-94 40 22 83 4 765
19 460800 24-Oct-96 45 55 100 24 569
20 480801 02-Oct-96 30 46 96 23 101
21 490800 18-Nov-96 40 33 111 8 1977
22 510100 26-Oct-95 36 39 79 21 198
23 530200 05-Apr-95 47 3 118 25 557
24 530800 05-May-95 46 16 117 52 551

Data Completeness

The available climatic data in DataPave 2.0 were reviewed to assess the adequacy and completeness of the data, and to identify the areas where the quality and quantity of LTPP climatic data can be improved. This review resulted in identification of missing or incomplete climatic data in the LTPP database.

Seasonal Monitoring Program Climatic Data

Some climatic data are collected as part of the SMP. Air temperature is collected on an hourly basis and is summarized for the day. The daily summary includes mean air temperature and minimum and maximum air temperature. Total daily precipitation is also recorded at the end of the day.

Table 4 presents the number of days of available data for minimum and maximum air temperature and the total precipitation for 68 SMP installations. Some LTPP sections have more than one SMP installation since sensors are reinstalled after each overlay. The installation date for each construction event and the first and last date of reported data (SMP_DATE) are also included in table 4. The following are some general observations regarding SMP data completeness:

  • Most SMP installations provided sufficient climatic data for this analysis.
  • There typically is more precipitation than air temperature data.
  • Some SMP sites were missing significant temperature data (e.g., sections 131031-2, 133019-1, and 390204-1).
  • Data for sections 370201-1, 370205-1, 370208-1, and 370212-1 were suspect.
  • Data feedback reports outlining the problems in detail were submitted to the LTPP program.

Automated Weather Station Data

Table 5 presents counts of data for 8 different climatic parameters presently collected from 35 AWS installations. The following are some observations on data completeness:

  • With few exceptions, the AWS installations provided sufficient data for analysis.
  • The precipitation data for section 190100 are completely missing. The windspeed data are also deficient.
  • Precipitation data are deficient for section 260100.
  • Some of the precipitation and almost half of the wind and solar radiation data are missing for section 260200.
  • Precipitation data from 8/14/96 to 8/26/97 are missing for section 530200.

 

Table 4. Counts of available SMP climatic data in DataPave 2.0.
SHRP ID
Const. No.
GPS_SPS Experiment
_No.
Install_
Date
Beginning
SMP_Date
Ending
SMP_Date
Days of
Data
Days of
Min_Air_
Temper-
ature
Days of
Max_Air_
Temper-
ature
Days of
Total_Rain
010101-1 S 1 07/24/95 07/24/95 11/16/98 725 684 684 725
010102-1 S 1 07/25/95 07/25/95 11/20/98 820 816 816 820
040113-1 S 1 08/15/95 08/15/95 11/16/98 645 628 628 645
040114-1 S 1 08/16/95 08/17/95 11/17/98 678 673 673 678
040215-1 S 2 08/24/95 10/13/95 11/19/98 653 647 647 653
041024-1 G 1 08/21/95 08/28/95 11/18/98 669 663 663 669
063042-1 G 3 07/12/95 07/12/95 11/23/98 643 637 637 643
081053-1 G 1 07/01/93 10/15/93 09/25/97 873 869 869 873
091803-1 G 1 08/19/93 01/20/94 10/15/97 826 823 823 815
100102-1 S 1 10/04/95 11/18/95 06/07/99 904 899 899 867
131005-1 G 1 08/07/95 08/08/95 11/17/98 787 783 783 787
131031-1 G 1 08/02/95 08/02/95 10/16/96 344 342 342 344
131031-2 G 6S 05/31/97 10/15/97 09/13/98 303 210 210 303
133019-1 G 3 07/31/95 07/31/95 04/27/98 554 355 355 554
161010-1 G 1 09/30/93 10/22/93 05/11/97 749 744 664 749
183002-1 G 3 09/07/95 09/07/95 06/15/98 486 482 482 486
204054-1 G 4 08/24/95 08/24/95 11/18/98 577 526 526 577
231026-1 G 1 09/15/93 12/17/93 06/25/95 556 555 555 556
231026-2 G 6B 09/26/96 10/15/96 10/20/97 350 348 348 350
241634-1 G 2 05/11/95 05/13/95 04/07/98 822 817 817 822
251002-1 G 1 09/01/93 01/18/94 10/14/97 862 859 859 862
271018-1 G 1 08/24/93 09/23/93 08/28/94 291 289 289 291
271018-2 G 1 08/29/94 08/29/94 09/07/97 881 738 738 881
271028-1 G 1 09/08/93 09/09/93 09/09/97 1318 1314 1314 1318
274040-1 G 4 09/21/93 09/21/93 09/08/97 932 921 921 932
276251-1 G 1 09/14/93 09/14/93 09/09/97 1226 1219 1219 1226
281016-1 G 2 07/18/95 07/18/95 10/18/96 459 458 458 459
281802-1 G 2 07/20/95 07/20/95 11/12/98 803 797 797 803
308129-1 G 1 08/12/92 08/31/93 09/30/97 925 922 922 925
310114-1 S 1 08/07/95 08/07/95 11/17/98 615 604 604 615
313018-1 G 3 08/10/95 08/10/95 11/16/98 596 590 590 596
320101-1 S 1 10/08/96 11/10/96 09/09/97 287 284 284 287
320204-1 S 2 10/09/96 11/09/96 09/08/97 303 302 302 303
331001-1 G 1 10/14/93 12/28/93 10/21/97 925 923 923 925
351112-1 G 1 04/05/94 06/20/94 09/08/97 565 560 560 565
360801-1 S 8 08/22/95 09/26/95 03/25/99 910 906 906 902
364018-2 G 4 10/27/93 12/30/93 10/13/97 926 923 923 926
370201-1 S 2 10/18/93 08/04/94 02/22/99 1302 98* 98* 1302*
370205-1 S 2 10/18/93 09/23/94 02/22/99 1142 98* 98* 1142*
370208-1 S 2 10/17/93 06/24/97 02/22/99 369 98* 98* 369*
370212-1 S 2 10/17/93 09/23/94 02/22/99 1066 98* 98* 1066*
371028-1 G 1 05/17/95 05/18/95 10/19/98 906 900 900 906
390204-1 S 2 07/20/95 02/10/98 05/17/99 400 60 60 400
404165-1 G 2 03/29/94 03/29/94 09/10/97 752 748 748 752
421606-1 G 4 08/09/95 08/10/95 10/26/98 782 780 780 782
460804-1 S 8 07/14/94 07/14/94 09/21/97 679 673 673 679
469187-2 G 1 07/18/94 07/18/94 09/22/97 609 600 600 609
481060-1 G 1 11/30/93 11/30/93 09/29/97 828 807 807 828
481068-1 G 1 11/01/93 12/16/93 09/16/97 846 844 844 846
481077-1 G 1 10/25/93 12/15/93 09/15/97 867 865 865 867
481122-1 G 1 11/22/93 01/25/94 06/15/97 674 670 670 674
483739-1 G 1 12/06/93 12/06/93 09/25/94 294 293 293 294
483739-2 G 1 09/26/94 09/26/94 01/29/95 126 126 126 126
483739-3 G 1 01/30/95 01/30/95 09/30/97 444 442 442 444
484142-1 G 4 11/08/93 11/09/93 09/25/97 840 835 835 840
484143-1 G 4 11/17/93 02/15/94 09/24/97 719 714 714 719
491001-1 G 1 08/05/93 11/04/93 05/03/95 442 436 436 442
493011-1 G 3 08/03/93 11/02/93 09/21/97 875 870 870 875
501002-1 G 1 10/06/93 01/12/94 10/22/97 903 901 901 851
510113-1 S 1 10/23/95 10/25/95 04/19/99 814 809 809 814
510114-1 S 1 10/23/95 01/25/96 06/04/99 802 796 796 802
533813-1 G 3 07/18/95 07/28/95 12/08/98 735 699 701 735
561007-1 G 1 08/10/93 10/19/93 06/18/97 756 672 672 756
831801-1 G 1 10/12/93 11/12/93 04/04/99 1619 1588 1588 1619
833802-1 G 3 10/14/93 10/14/93 11/05/98 908 900 900 908
871622-1 G 1 09/22/93 12/13/93 10/29/97 893 890 890 893
893015-1 G 3 09/29/93 12/15/93 11/05/97 1184 1067 1067 1184
906405-1 G 1 10/06/93 10/06/93 09/18/97 794 789 789 794

Data marked with an asterisk (*) appears to be unusable.

Table 5. Counts of AWS collected data for selected climatic parameters.
AWS_ID Installation
Date
From Date To Date Days of
Min
_Day
_Temp.
Days of
Max
_Day
_Temp.
Days of
Total
Day
_Precip.
Days of
Min
_Day
_Humidity
Days of
Max
_Day
_Humidity
Days of
Mean
_Day_
Wind
_SPD
Days of
Max
_Day_
Wind
_SPD
Days of
Mean
_Day
_Solar
10101 2/7/1995 2/7/1995 3/31/1998 1147 1147 1149 1072 1072 1147 1147 1147
40100 2/16/1995 5/4/1995 11/30/1998 1306 1306 1307 1304 1304 1306 1306 1306
40200 7/21/1994 7/21/1994 11/30/1998 1592 1592 1594 1590 1590 1592 1592 1592
50113 5/9/1995 5/10/1995 8/31/1998 1186 1186 1188 1118 1118 1186 1186 1186
50803 9/25/1997 9/25/1997 8/31/1998 339 339 341 339 339 339 339 339
05A601 5/20/1997 5/21/1997 4/30/1998 343 343 345 304 304 343 343 343
80200 9/15/1995 9/15/1995 11/30/1998 1163 1163 1043 1150 1150 1163 1163 1163
100100 11/15/1995 11/15/1995 11/30/1998 1110 1110 1083 1111 1111 1071 1071 1111
120101 6/11/1996 6/12/1996 2/28/1998 620 620 623 599 599 620 620 620
190100* 3/4/1997 3/5/1997 9/30/1998 575 575 0* 573 480 403* 403* 575
190200 3/3/1997 3/3/1997 5/21/1998 444 444 445 444 444 444 444 444
200100 8/6/1996 8/6/1996 7/31/1998 724 724 725 724 721 724 724 724
200200 8/7/1996 8/7/1996 7/31/1998 723 723 724 723 716 723 723 723
220113 10/14/1997 10/14/1997 8/31/1998 249 249 305 249 249 249 249 249
260100* 9/4/1996 2/27/1997 9/30/1998 580 580 398* 580 558 580 580 580
260200* 9/5/1996 7/26/1997 9/30/1998 432 432 343* 432 423 236* 236* 236*
300100 5/20/1998 5/20/1998 11/30/1998 194 194 195 194 194 193 193 194
300800 11/17/1994 11/18/1994 11/30/1998 1473 1473 1246 1473 1473 1473 1473 1473
310100 8/7/1996 8/7/1996 8/31/1998 754 754 755 754 754 754 754 754
320200 5/19/1995 5/19/1995 11/30/1998 1272 1272 1274 1268 1268 1272 1272 1272
350101 9/21/1995 9/27/1995 1/31/1998 847 847 848 847 847 833 833 847
350801 8/9/1996 8/10/1996 1/31/1998 530 530 533 528 528 530 530 530
360800 11/22/1995 11/22/1995 10/31/1998 1059 1059 1060 1059 1059 1055 1055 1059
370200 8/4/1994 8/4/1994 7/31/1997 1008 1008 1010 1008 987 1002 1002 981
370800 3/10/1998 3/11/1998 5/31/1998 82 82 82 82 82 82 82 82
380200 1/13/1995 1/13/1995 9/30/1998 1046 1046 1048 1046 1007 1046 1046 1046
390200 9/8/1994 9/8/1994 8/31/1998 1179 1179 1182 1179 1094 1179 1179 1179
400113 5/29/1997 5/29/1997 12/31/1997 216 216 217 210 210 216 216 216
460800 10/24/1996 10/24/1996 9/30/1998 706 706 707 706 704 620 620 706
480113 8/26/1997 8/26/1997 2/28/1998 186 186 187 186 186 186 186 186
480801 10/2/1996 10/2/1996 2/28/1998 513 513 437 470 470 513 513 513
490800 11/18/1996 11/18/1996 11/30/1998 742 742 743 740 740 742 742 742
510100 10/26/1995 10/26/1995 8/31/1998 970 970 963 970 924 964 964 970
530200* 4/5/1995 4/5/1995 11/30/1998 1335 1335 958* 1320 1320 1335 1335 1335
530800 5/5/1995 7/18/1995 11/30/1998 1231 1231 1232 1223 1223 1231 1231 1231
Total   7/21/1994 11/30/1998 27876 27876 26290 27575 27248 27352 27352 27654

*Identifies deficient data.

LTPP VWS Estimates in Climatic Module

Monthly data for selected VWS parameters were reviewed for completeness. Different temperature, precipitation, humidity, and windspeed data provided with DataPave 2.0 were considered. Table 6 includes a list of VWS parameters that were reviewed.

 

Table 6. List of selected VWS climatic parameters reviewed for data completeness.
IMS Table IMS Field Abbreviation
CLM_VWS_TEMP_MONTH MIN_MON_TEMP_AVG Temp_Min
MAX_MON_TEMP_AVG Temp_Max
DAYS_BELOW_0_C_MONTH Temp_Cold
DAYS_ABOVE_32_C_MONTH Temp_Hot
FREEZE_INDEX_MONTH Temp_FI
FREEZE_THAW_MONTH Temp_FT
CLM_VWS_PRECIP_MONTH TOTAL_MON_PRECIP PRC_Total
WET_DAYS_MONTH PRC_Wet
TOTAL_SNOWFALL_MONTH PRC_Snow
CLM_VWS_HUMIDITY_MONTH MIN_MON_HUM_AVG Humid_Min
MAX_MON_HUM_AVG Humid_Max
CLM_VWS_WIND_MONTH MEAN_MON_WIND_AVG Wind_Mean
MAX_MON_WIND_SPD Wind_Max

GPS Data Counts

The Administration module of the LTPP database contains an Experiment_Section table that is considered the master control section for the database. All test sections are supposed to have entries in the table. The table thus is both a source of data and provides a cross check on data from other areas of the database. For GPS sections, the link between the VWS climatic tables and the Experiment_Section table is fairly complete. Table 7 shows total data counts (in months) for selected parameters listed in table 6. Out of the 790 GPS sections currently in the Experiment_Section table, 788 sections had VWS data; however, data for 2 GPS sections could not be located. These sections (both GPS–1) are listed in table 8. One GPS section (section 481094), also listed in table 9, had VWS estimates, but was not listed in the Experiment_Section table.

Table 7 shows that 788 GPS sections had adequate temperature and precipitation data. There are slightly more data for precipitation than for temperature (211,523 and 211,458 months, respectively). Humidity and windspeed data, on the other hand, were missing for more than 40 percent of the sections. Minimum and maximum humidity were missing for 328 sections, average windspeed was missing for 310 sections, and maximum windspeed was missing for 348 sections. For the sections that had humidity and windspeed data, the average number of records per section was almost half of the temperature and precipitation data. This indicates that these data are incomplete during the data collection period.

 

Table 7. Record count of selected parameters for 788 GPS sections.
Parameter Total Records (months of data) Number of GPS Sections With Data Average Months of Data per Section
Temp_Min 211,458 788 268
Temp_Max 211,458 788 268
Temp_Cold 211,458 788 268
Temp_Hot 211,458 788 268
Temp_FI 211,458 788 268
Temp_FT 211,458 788 268
PRC_Total 211,523 788 268
PRC_Wet 211,523 788 268
PRC_Snow 211,523 788 268
Humid_Min 71,893 460 156
Humid_Max 71,893 460 156
Wind_Mean 68,963 478 144
Wind_Max 93,336 440 212

 

Table 8. GPS sections and SPS sites without VWS estimates.
Experiment Type Experiment No. LTPP ID
GPS 1 481061
1 901802
SPS 8 370800
1 550100
2 550200
8 550800
9 55C900
9 81A900
9 89A900

 

Table 9. Sections with VWS data but not in the Experiment_Section table.
Experiment Type Experiment No. LTPP ID
GPS unknown 481094
SPS 4 32B400
6 470600
9 50900
9 90900
9 120900
9 180900
9 200900
9 270900
9 280900
9 310900
9 350900
9 370900
9 390900
9 480900
9 550900, 55A900, 55B900

SPS Data Counts

For SPS sites, the link between the VWS climatic data and the Experiment_Section table is not direct. The CLM_SITE_VWS_LINK table is designed to provide the link between the VWS data and other tables. However, this table currently only includes data for GPS sections and SPS control sections. Expanding this table to other SPS sections (noncontrol sections and SPS sections that are linked to GPS) can significantly improve the VWS data accessibility for SPS.

Out of the 200 SPS sites that are represented in the Experiment_Section table, 120 sites are linked to GPS through the SPS_GPS_Link table. Data for these sections are the same as the GPS data. Data for seven SPS sites were not located. These sections are listed in table 8. The data counts for the other 74 SPS sites are listed in table 10. There is also one site that is both linked to GPS and has VWS data (VWS_ID 340900 linked to GPS section 341011). SPS sections listed in table 9 had VWS data, but were not listed in the Experiment_Section table. These data were not included in this review since pertinent data could not be located.

As with the GPS data, almost half of these SPS sites were missing humidity and windspeed data. The average months of data per section for these data were about 40 percent less than the temperature data, indicating incomplete coverage.

 

Table 10. Record count for selected parameters for 74 SPS sites.
Parameter Total Records (months of data) Number of SPS Sites With Data Average Months of Data per Section
Temp_Min 18,332 74 248
Temp_Max 18,332 74 248
Temp_Cold 18,332 74 248
Temp_Hot 18,332 74 248
Temp_FI 18,332 74 248
Temp_FT 18,332 74 248
PRC_Total 18,336 74 248
PRC_Wet 18,336 74 248
PRC_Snow 18,336 74 248
Humid_Min 5,822 39 149
Humid_Max 5,822 39 149
Wind_Mean 5,842 42 139
Wind_Max 6,814 34 200

Data Coverage and Adequacy

Climatic data coverage was calculated from the first and last month of climatic data for a section and shows the maximum number of years of climatic data available for every section. Table 11 shows the distribution of years of climatic data for 862 GPS sections and SPS sites. This table shows that about half of the sections (408 sections) have between 16 and 20 years of climatic data, while the other half of the sections have more than 20 years of data. The most extensive data are for the SPS site (ID 810500), with more than 56 years of data. Two GPS sections (ID 541640 and ID 134111), each with about 13 years of data, have the least data.

Data adequacy was only evaluated to identify the quantity of the missing data in the LTPP database and is not relevant to the analysis of the data. Data adequacy for each parameter is assessed by the percentage of the available data for the period covered. This value is derived by dividing the number of months of available data by the number of months of data coverage. Table 12 includes the distribution of data adequacy for GPS and SPS sections for different climatic parameters. The precipitation data for all 862 sections cover the entire data period (100 percent adequacy) for all parameters. For temperature parameters, 859 sections were 100 percent complete, while 3 sections had data for 95 percent of the covered period. Humidity data for 363 sections and mean windspeed for 342 sections were missing (not available), and the remaining data had less than 80 percent adequacy (no section had data for the entire data coverage). The maximum windspeed was missing for 388 sections; however, about 15 percent of the sections were 100 percent complete, while another 15 percent were 95 percent complete.

 

Table 11. Distribution of years of climatic data for GPS and SPS sections.
Years of Climatic Data (Coverage) Number of Sections
From To GPS SPS All
12 16 2 0 2
16 20 356 52 408
20 24 124 1 125
24 28 136 8 144
28 32 63 8 71
32 36 50 2 52
36 40 30 1 31
40 44 13 1 14
44 48 7 0 7
48 52 7 0 7
52 56 0 0 0
56 60 0 1 1
All   788 74 862

 

Table 12. Distribution of data coverage for different climatic parameters.

Adequacy,
% of
coverage

Temperature-Related Parameters Precipitation Humidity and Windspeed
Temp
_Min
Temp
_Max
Temp
_Cold
Temp
_Hot
Temp
_FI
Temp
_FT
PRC
_Total
PRC
_Wet
PRC
_Snow
Humid
_Min
Humid
_Max
Wind
_Mean
Wind
_Max
0 0 0 0 0 0 0 0 0 0 363 363 342 388
5 0 0 0 0 0 0 0 0 0 1 1 13 7
10 0 0 0 0 0 0 0 0 0 2 2 12 4
15 0 0 0 0 0 0 0 0 0 2 2 1 4
20 0 0 0 0 0 0 0 0 0 2 2 1 2
25 0 0 0 0 0 0 0 0 0 3 3 3 1
30 0 0 0 0 0 0 0 0 0 5 5 13 1
35 0 0 0 0 0 0 0 0 0 8 8 21 3
40 0 0 0 0 0 0 0 0 0 13 13 38 3
45 0 0 0 0 0 0 0 0 0 44 44 28 10
50 0 0 0 0 0 0 0 0 0 65 65 51 11
55 0 0 0 0 0 0 0 0 0 42 42 35 8
60 0 0 0 0 0 0 0 0 0 44 44 37 13
65 0 0 0 0 0 0 0 0 0 25 25 23 20
70 0 0 0 0 0 0 0 0 0 22 22 26 17
75 0 0 0 0 0 0 0 0 0 35 35 36 37
80 0 0 0 0 0 0 0 0 0 186 186 182 29
85 0 0 0 0 0 0 0 0 0 0 0 0 23
90 0 0 0 0 0 0 0 0 0 0 0 0 38
95 3 3 3 3 3 3 0 0 0 0 0 0 140
100 859 859 859 859 859 859 862 862 862 0 0 0 103

Data Quality

The number of weather stations on which VWS estimates are based is related to the quality of the estimated data since better estimates are made from five weather stations rather than a single weather station. This fact was demonstrated by comparing different estimates (refer to the discussions for table 27).

Table 13 shows the average number of contributing weather stations for each VWS table. Data in table 13 show that the temperature and precipitation estimates are generally made based on data from more than the four closest weather stations. The humidity and windspeed estimates, however, are based on data from a single weather station.

 

Table 13. Total record counts and number of contributing weather stations for AWS estimates.
IMS Table Total Records
(months of data)
Average Number of
Contributing Weather
Stations
CLM_VWS_TEMP_MONTH 233,846 4.5
CLM_VWS_PRECIP_MONTH 233,915 4.6
LM_VWS_HUMIDITY_MONTH 79,722 1.0
CLM_VWS_WIND_MONTH 118,406 1.0
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