Date post: | 17-Jul-2015 |
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Science |
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California Climate
Outcome Likelihood Tool
Nina Oakley, Kelly Redmond, Grant Kelly, Britta Daudert
Western Regional Climate Center
USDM Forum
April 22 2015 – Reno, NV
Motivations How might this year turn out?
NCDC “Amelioration” tool (PHDI) 1
M. Dettinger “ESP” analysis
P. Iñiguez PRISM simulations
What water managers want:
Better seasonal forecasts, monitoring, communication2
Constrain decision-making
Tool that is customizable, daily resolution
Tool that is graphical, explains caveats3
1ncdc.noaa.gov/temp-and-precip/drought/recovery/2Steinemann 2014, BAMS 3Pulwarty 2003, Water Resources
Data Source NWS COOP via ACIS
Daily, long record
Decision makers often state climate forecasts unreliable1
Suggest stations with record 1920 or better-present
Any station, any record
in US
Provisions for how
much missing data
acceptable
COOP at Manzanita Lake, CA1Pulwarty 2003, Water Resources
3 Data Options “Observed” data in station record
Distribution built from all past periods equal to “recovery period”in station record
“Analog” Periods
Identify periods in station record of date range equal to observed period that are within +/- 1, 2, or 3 deciles of current observed total
Take their corresponding future “recovery” periods and create distribution
Random sampling of station record
Sample each day of “recovery period” from station record, build “synthetic accumulations”, repeat 1000x
Apr 13 2001 + Apr 14 1934 + Apr 15 1901 + ... Sept 30 1996
Doesn’t account for multiple day precipitation streaks
2 “Analysis” Options
Amelioration
Likelihood of reaching normal, recovering deficit by end of
“recovery period”
Custom Threshold
Likelihood of receiving a user-specified amount of
precipitation by end of “recovery period”
At RENO
2014-10-01 to
2015-04-12
2.93 in accum.
0 missing days
2.43 in deficit
11.87 in needed
by 09-30-2016
to recover deficit,
reach normal
15.6% chance
of recovering
based on 77 of
78 possible
periods in record
1937-03-01 to
2015-04-12
“Observed”
optionDeciles
Amount needed
Normal
for period
Probability of
occurrence
“Analog”
optionAt RENO
2014-10-01 to
2015-04-12
2.93 in accum.,
falls between
10th - 20th
percentile
2.43 in deficit
11.87 in needed
by 09-30-2016 to
recover deficit,
reach normal
13% chance
of recovering
using +/- 1
decile analog
(10th-30th
percentile),
23 periods
Probability of
occurrence
Amount needed
Normal
for period
Example graph + table for Sacramento, CA
Likelihood of exceeding threshold of 3 inches
by end of WY 2015 (20% chance)
Spaghetti Plot (coming soon)
Observed Precipitation
10-01-2014 through
04-12-2015
+Selected precipitation
traces 04-13-2015
through 09-30-2016
=Range of outcomes
based on climatology
Hypothetical Station
Observed period 10-01-2014 to 04-12-2015,
Future period ending 09-30-2016 10 traces shown
pre
cip
ita
tio
n
time
Limitations and Future Work
Using historic record, does not account for future trends
Point rather than areal data
Test on target audience, implement feedback
http://wrcc.dri.edu/col/
Expand to other accumulating quantities
snowfall, HDD, CDD, GDD
Thank you!
South Yuba River, Sierra Nevada, CA
Feb 7/8 2015 Atmospheric River event
Bad for skiing, good for kayakingPhoto credit: Ben Hatchett [email protected]
@WRCCclimate
Connect with WRCC!
Random
Sampling
2014-10-01 to
2015-03-18
3.09 in
0 missing
0.15 in deficit
6.65 in needed
to recover deficit
by 09-30
28.6% chance
of recovering
based on 1000
random daily
samples from
record
1892-01-01 to
2015-03-19