Transcript The Diurnal Temperature Smart Tool

The Diurnal Temperature
Smart Tool
Angie Enyedi
National Weather Service Jacksonville, FL
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What is it and why the need for it?
How is it implemented?
What are the results?
What is it?
An interpolation method of
hourly temperatures between
forecast maximum and
minimum temperatures in the
new graphical forecast
produced by the NWS, the
Interactive Forecast
Preparation System (IFPS).
Initial Interpolation Techniques
• The default interpolation methods in the
Graphical Forecast Editor (GFE) were either
the Cubic Spline or the Linear Interpolation
Methods.
• These methods were used during the
implementation stage of IFPS.


Both fail to represent abrupt temperature falls
after sunset and temperature rises after sunrise.
Both have unrepresentative peaks (linear) and
plateaus (cubic spline) when the daily max or
min temperature is achieved.
We need an interpolation tool that accounts
for monthly differences in radiational cooling
and insolation between the times of daily
minimum and maximum temperatures!
ANSWER: The Diurnal Temperature Tool
Cubic Linear Diurnal
MAE ( F)
4.7
3.4
Mean Absolute Error
1.1
How the Tool was Implemented at JAX
1. Stratifying the Data
7 years of hourly
ASOS observations
were stratified by
month then by hour
for site JAX
(Jacksonville, FL).
 Archived data was
obtained from NCDC.

Date/Time (Z)
Actual Temp
Apr 1, 1995 0200Z
55
Apr 2, 1995 0200Z
53
….etc…
Apr 30, 2001 0200Z
66
2. Averaging the Data
All temps in a
particular hour in a
given month were
avearged to get an
average Thour.
For Example:
Thour for 01 April = 60.30
Thour for 02 April = 59.46
Thour for 03 April = 58.59
All Temps for that hour summed, then
divided by total number of entries to
get Thour.
Average Thour for 02Z in April = 59.56
3. Calculating the ratio, f
Temperatures from 00Z-23Z
were converted to a range
between 5-95% based on the
difference between the Tmax
and Tmin each month.
Note: f for Tmax = 95
f for Tmin = 5
This was done to reduce the warm
and cold bias.
(Thour-Tmin)
Tmax-Tmin
90
+ 5 = f
4. Smart Tool references the “f” Table
F Table for April

The f table is referenced by the
diurnal temperature smart tool
when it calculates hourly
temperatures (Thour) between
the forecast daily minimum and
maximum temperatures.
 Tool will warm & cool
temperatures based on monthly
diurnal climatological trends.
00Z
58
12Z
12
01Z
45
13Z
33
02Z
38
14Z
53
03Z
33
15Z
68
04Z
27
16Z
78
05Z
23
17Z
85
06Z
20
18Z
91
07Z
16
19Z
94
08Z
12
20Z
95
09Z
9
21Z
92
10Z
7
22Z
86
11Z
5
23Z
75
• Note the seasonal variation of the approximate time
of the daily max and min temperature.
• Note the seasonal variation of temperature decrease
(increase) after sunset (sunrise).
Cubic Linear Diurnal
MAE ( F)
6.4
3.8
Mean Absolute Error
1.7
Cubic Linear Diurnal
MAE ( F)
4.4
3.1
Mean Absolute Error
1.8
Cubic Linear Diurnal
MAE ( F)
5.1
3.1
Mean Absolute Error
0.8
Results of the Diurnal Temperature
Interpolation Method
Data suggests that the diurnal temperature
interpolation method better represents
monthly radiational cooling & insolation
trends when compared to the linear and
cubic spline methods.
Benefits of the Diurnal Temperature
Interpolation Tool

Best represents abrupt diurnal temperature rises
and falls when compared to the cubic spline and
linear interpolation techniques.
 Has representative increases and decreases when
the daily max or min temperature is achieved.
 Can be customized for each month (and various
sites across the country) accounting for
differences in radiational warming & cooling.
Short Comings of the Diurnal
Temperature Smart Tool

Only customized for site JAX in our forecast area.
The tool is run over our entire grid space and may
not represent radiational cooling or insolation trends
at sites further inland nor those close to the coast.
 Does not represent sensible heat influences from
convection or latent heat influence from ground
moisture.
 Does not account for atypical warming/cooling such
as warm air advection at night or cold air advection
during the day.
Taking the Diurnal Smart Tool a
Step Further…
Data could be further stratified based on cloud
cover, for example:
Diurnal temperature smart tool could be created
for sunny/mostly sunny, partly cloudy, and
clouldy/mostly cloudy days in GFE.
Credits & Where to Get the Tool
Cheryl Sharpe and Steve Nelson (NWS)
Created the original Diurnal Temperature Smart Tool
Jason Hess
IFPS Focal Point NWS Jacksonville, FL
The Diurnal Temperature Smart Tool is available for
download into IFPS at the Smart Tool Repository
Website.
Thank You!
Questions and/or Comments?
Angie Enyedi
Forecaster NWS Jacksonville, Climate F.P.
[email protected]