Options Selection

What can this tool do? Determine the likelihood of recovering a precipitation deficit or reaching a precipitation threshold during some future period based on historic station data. Read more

Station (choose on map)

Stations shown on map are from the Global Historic Climate Network (GHCN) and have records beginning in 1920 or prior and running through present. These stations are suggested for analysis as several major droughts are captured in the record, though not all stations shown have a complete record. Station metadata can be explored here: WRCC COOP data

Alternatively, any GHCN station ID may be entered manually in the "station selected" field. Consult the link above to acquire a station ID or explore GHCN stations using WRCC's SCENIC interface.



Date Range Selection:

Dates may be input by hand or selected by clicking on the calendar icon. Longer periods generally provide more useful information.

The first two dates ("From", "To") cover a past period over which precipitation accumulation occurred. We refer to this as the "observed" period. A precipitation surplus or deficit can be calculated for this period.

The third date specifies the end of the future period of interest (period between "To" and "ending"). We refer to this as the "recovery" period. For the specified recovery period, all like periods within the station’s record are utilized to assess the range of possible precipitation accumulations.

Start date (From: ) can be up to 7 years prior to the current date and cannot be later than the current date.
Mid-date (To: ) must be current date or prior.
End date (ending: ) must be later than today and within 7 years following the current date.

Missing days: Specify number of missing days allowed in each period in station’s record corresponding to specified future "recovery" period. This option applies only if “observed” or “analog” data options are chosen

Data Options:

There are three data options that can be used to calculate probability density functions and cumulative distribution functions for precipitation at a station and to calculate likelihood of recovering a precipitation deficit or reaching a threshold.

1) Observed data in station record: Use sums of precipitation observations from each period in the stations record equal to the specified future "recovery" period to build precipitation distributions.

2) Random daily samples: Build 1,000 “synthetic periods” equal to the length of the specified future "recovery" period by taking random daily samples from the station’s data. Example: if the future period specified were Jan 1-March 31 at a station with a record 1920-present, samples might be sums of precipitation values for days as follows:
Sample 1: Jan 1 1994 + Jan 2 1937 + Jan 3 1976 + ... + Mar 30 1942 + Mar 31 2009
Sample 2: Jan 1 1966 + Jan 2 2001 + Jan 3 2010 + ... + Mar 30 1949 + Mar 31 1951
on through sample 1,000.

3) Analog periods: For date ranges in the station’s record that are equal to the date range specified for the observed period (From/To), “analog periods” are defined as those periods where precipitation total is within +/- 1, 2, or 3 deciles of the current observed period precipitation value as specified by the user. The distribution generated is built from the periods of those particular years/periods that correspond to the future "recovery" period specified.




Define analog periods as those with precipitation totals decile(s) of the current accumulation period total.

Graphics Options:

Spaghetti plot: Generates a graph showing precipitation accumulation for observed period attached to all precipitation traces for the selected future "recovery" period to create a plume of possible outcomes by the end of the future "recovery" period. Based on observed data in station record only.

Probability density function: Generate a probability density function for precipitation totals in a station’s record corresponding to the specified future "recovery" period and using the data option chosen. Each bar’s height represents the likelihood of precipitation values within the corresponding 1-inch bin specified on the x-axis. PDF is normalized such that area of bars is equal to 1.

Cumulative distribution function: Generate a CDF for precipitation totals in a station’s record corresponding to the specified future period and using the data option chosen.




Analysis Options:

There are two analyses that can be performed. Results of the selected analysis will be displayed below the generated graph(s).

1) Amelioration: Calculate the likelihood of recovering the accumulated precipitation deficit in the observed period (From/To) by the end of the future "recovery" period (To/ending). This calculates the likelihood of receiving normal precipitation for the future period plus the accumulated deficit.

2) Median: Calculate the likelihood of recovering the accumulated precipitation deficit from median in the observed period (From/To) and reaching median by the end of the future "recovery" period (To/ending).

3) Custom threshold: Calculate the likelihood of receiving a specified amount of precipitation by the end of the future "recovery" period.

Custom threshold: likelihood of receiving inches by end of recovery period