Screen Interhouly Temperature Ranges

Description

It is important to be able to detect undocumented discontinuities in a time series of temperature data that would indicate a potential change in the observing methodology. This tool allows for the visual and statistical analysis of the range between morning and afternoon temperature observations in the historical period relative to the same observations in the modern temperature record. All modern hourly temperature data are extrapolated to the top of the hour, solar time, and sunrise/sunset as required so comparisons between historical and modern records are as compatible as possible.

Discussion of the Output Data
The calculated interhourly temperature ranges in the modern period are summarized at the top of the output file on a monthly basis under “Modern Interhourly Temperatures” (minimum, 5th percentile, mean, 95th percentile, and maximum values are output). These values are then utilized to assess the daily interhourly temperature ranges in the historical period, which are output under “Historical Interhourly Temperatures”. A flag is generated if the daily historical range falls below the 5th percentile or exceeds the 95th percentile. There are four possible flags:

HOB Tools also generates monthly time series plots of the daily historical interhourly temperature range through time (e.g., Fig. 1). July is plotted by default because any abrupt shifts in the time series are easier to detect in the summer due to the smaller temperature variance. Plots of other months can be displayed by choosing the appropriate month from the drop-down list box next to “Displayed Month” and pressing the “Plot” button (Fig. 1). The modern maximum range (red), modern mean range (green), and modern minimum range (blue) are also plotted, so the historical period can be visually assessed with respect to the modern (Fig. 1). The top line of title text for the graph is the same as the “Output File Header” specified by the user.

Figure 1. This plot shows the daily range in temperature from 6 a.m. to 1 p.m. at Manhattan, Kansas, during July in the historical period. Note the jump in the time series at 1883/84 (circled in red), which suggests that a change in the exposure and/or observing methodology occurred. In this case, metadata indicated that temperature observations were recorded by a different observer at a different location within Manhattan beginning in 1884.

Historical Input

Historical Temperature File
Select the historical temperature data to analyze by clicking on "Browse" and navigating to the proper file.

Historical Input Data Format
Year / Month / Day / Data

Each "/" is a tab (i.e., data should be tab-delimited). Missing Data should be denoted as "-99".

Temperature Units
Select the proper temperature units for the historical data.

Historical Start Row
This input is the row number where the main data to be processed begin in the historical temperature file selected above. An example of how row numbers are entered is shown in Figure 2 located in the Running HOB Tools topic.

Columns to Compare to Modern Data
Enter the two columns of hourly temperature data in the historical dataset that will be compared to the modern data. An example of how column numbers are entered is shown in Figure 2 located in the Running HOB Tools topic. These two columns must "match" with the selected hours in the “Modern Input” section as shown in Figure 2 (see also "Times to Compare to Historical Data" below).

Figure 2. The column numbers of the historical fixed hourly temperatures (i.e., “Columns to Compare to Modern Data”) must agree with the selected “Times to Compare to Historical Data.” In this example, column number 4 in the historical dataset must correspond to 6 a.m. temperatures (red) and column number 5 must correspond to 1 p.m. temperatures (purple). Neither sunrise nor sunset is selected in this example, so the “Sunrise/Sunset File” and “Sunrise/Sunset Start Row” areas are disabled.

Modern Input

Modern Temperature File
Select the modern temperature data to analyze by clicking on "Browse" and navigating to the proper file.

Modern Input Data Format
Year / Month / Day / 1 a.m. / 2 a.m. / … / 11 p.m. / 12 a.m. / Maximum / Minimum

Each "/" is a tab (i.e., data should be tab-delimited). The “…” denoted above represents 3 a.m. through 10 p.m. Missing data should be denoted as “-99”.

Temperature Units
Select the proper temperature units for the modern data.

Modern Start Row
This input is the row number where the main data to be processed begin in the modern temperature file selected above. An example of how row numbers are entered is shown in Figure 2 located in the Running HOB Tools topic.

Top of the Hour Correction (minutes)
Enter the number of minutes prior to the top of the hour when observations were recorded in the modern temperature record. The default entry is 20 minutes, which was typical of many U.S. stations prior to the establishment of the Automated Surface Observing System (ASOS).

Solar Time Correction (minutes)
Enter the solar time correction in minutes. This allows HOB Tools to extrapolate standard time zones to solar time, so modern observations can be more directly compared to the historical observations recorded prior to the development of standard time zones. If no solar time correction is required, a value of zero can be entered and no correction will be performed.

Times to Compare to Historical Data
Select the two times in the modern dataset that will be compared to the historical data. These two selected hours must "match" with the column numbers entered in the “Historical Input” section as shown in Figure 2 (see also "Columns to Compare to Modern Data" above).

Sunrise/Sunset File
If sunrise and/or sunset is selected as one of the "Times to Compare to Historical Data" above, then the modern hourly temperature data will need to be extrapolated to sunrise and/or sunset. HOB Tools will then enable this input area, so the sunrise/sunset data file can be selected. Sunrise and sunset observations are available from the United States Naval Observatory website.

Sunrise/Sunset Input Data Format
If only sunrise is selected:

If only sunset is selected:

If both sunrise and sunset are selected:

Each "/" is a tab (i.e., data should be tab-delimited). Missing data should be denoted as “-99”. These data must start and end on the same day as the modern hourly temperature data input above.

Sunrise/Sunset Start Row
This input is the row number where the main data to be processed begin in the sunrise/sunset data file selected above. An example of how row numbers are entered is shown in Figure 2 located in the Running HOB Tools topic. This field will only be enabled if sunrise or sunset is selected as one of the "Times to Compare to Historical Data" above.

Output

Output File
Select the file where the numerical results will be stored.

Output File Header
Information entered here will be output in the first line of the output file.