Compute Precipitation Totals

Description

This tool analyzes daily or monthly precipitation data to create time series of total precipitation amounts and precipitation days. These analyses can be run during specific months or during a specific range of months (e.g., seasonal, annual).

Discussion of the Output Data
If an analysis is performed during a range of months that encompass two years, then the year reported in the output file will be that associated with the end month (i.e., if the start month is December and the end month is February, then a mean precipitation value associated with 1872 in the output file will be the mean precipitation from December 1871-February 1872). Any missing data encountered by HOB Tools during any precipitation analysis results in a flag (including error bars). The number of flags is reported in the output file, and any result other than zero should be checked to determine if the missing data impact the results. If error bars are included, then those will be summed along exactly like the precipitation data for output.

Precipitation Input

Input File
Select the precipitation data to analyze by clicking on "Browse" and navigating to the proper file.

Input Data Format
If precipitation data are daily:

If precipitation data are monthly:

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

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

Precipitation Data Column
This input is the column number where the precipitation data are located in the input file selected above. An example of how column numbers are entered is shown in Figure 2 located in the Running HOB Tools topic.

Precipitation Data Type
Select whether the precipitation data are in daily format or in monthly format.

Input Error Bars
Place a check in the box to include +/- error bars in the conversion. It is expected that this error encompasses only one column and is symmetrical about the precipitation value (i.e., an error value of 1.5 means +/- 1.5). HOB Tools assumes that if error bars are included, then the precipitation are in monthly format.

Error Column Number
If "Input Error Bars" is checked, then this field will be enabled. This input is the column number where the +/- error bars are located in the input file selected above. An example of how column numbers are entered is shown in Figure 2 located in the Running HOB Tools topic.

Customize Totals

Compute By Month
This computation type is selected by default, and will perform the analysis by months that are checked by the user. If "Jan" and "Feb" are checked, then the analysis will be run twice--once for January data and once for February data. If "Monthly" has been selected under "Precipitation Data Type" above, then this computation type will be disabled.

Compute By Range
Selecting this computation type will enable the "Start Month" and "End Month" fields, which will allow for the analysis to be performed across a range of months (e.g., seasonal, annual). For example, to analyze Northern Hemispheric winter, select the start month as "December" and the end month as "February."

Values to Include in Total
Options here control how HOB Tools sums precipitation amounts and precipitation days. If "Daily" has been selected under "Precipitation Data Type" above, then HOB Tools will sum precipitation days in addition to amounts that are greater than the value displayed next to "Precipitation Amounts >". Undercount is a common bias in historical precipitation data (Mock 1991, 2000), and analysis of thresholds can assist in quantifying such bias. HOB Tools also allows a special value, "-1," to denote a day when measurable precipitation occurred (more than a trace) but no amount was reported. This method accounts for observers who did not record a precipitation amount until the end of an event (e.g., the observer notes the rain started on the 13th but did not end until the 14th and records a 2-day total on the 14th). It also accounts for observers who only reported whether or not precipitation occurred. Removing the check from the box "Include -1 Values" will force HOB Tools to ignore -1 values in precipitation day counts. By default, "Precipitation Amounts >" is set to 0.00 and "Include -1 Values" is checked so all amounts will be counted and any "-1" values will be added to the count of precipitation days.

Precipitation 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.