Post on 25-Feb-2016
description
Comparison of Point Measurements within SFWMD
and NARR-A values
Alicia FoggApril 26th, 2005
µ0 20 40 60 8010
Miles
South Florida Water Management District
• 6 million people live in the SFWMD
•Encompasses 17,000mi2
•1800 mi of canals and levees
•200 major water control structures
•70 critical•130 manually operated
•27 pump stations•6 under remote control
Simple Water Balance
Purpose: develop simple water balance approach to quantify change in storage
QHinQHout
qRAIN
qET
Control Volume
Continuity Equation over Control Volume:
( (
Area
Data Sources for Simple Water Balance
Horizontal Data
Structure Flow– Monitored at each Structure
Vertical Data
Rainfall – Point data at Structures and NEXRAD data over entire region
ETp – no Points in region
???
Weather Measurements within the SFWMD
• SFWMD has database containing over 22,000 time series variables
• 16 potential evapotranspiration (ETp) and only one evapotranspiration rate site
• 69 Operations and Maintenance rainfall sites operating on a real-time basis
Potential Evapotranspiration Stations within SFWMD
• Highly monitored system with over 22,000 variables contained within parameter database
•16 potential evapotranspiration measurement sites recorded daily
• Potential Evapotranspiration dependent on
•Wind Speed
•Water Availability
•Net radiation
•Vegetation Type
ETp – Historic and Recorded
0
1
2
3
4
5
6
Janu
ary
Februa
ryMarc
hApri
lMay
June Ju
ly
Augus
t
Septem
ber
Octobe
r
Novem
ber
Decem
ber
Pote
ntia
l Eva
pora
tion[
mm
/day
]
Historic ETp
Measured ETP
• SFWMD recommends using ETp daily values for vertical components.
• ETp is a measure of the vegetation and the atmospheric conditions – not dependent on the amount of moisture!!!
• Florida is WET, but not all of the ground is inundated all the time.
NARR-A Monthly Data
Queried 56 points in Southern Florida for a one-year period November 2002 to October 2003.
NARR-A Monthly Data
Calculating Monthly ET
• The results obtained from NARR-A in W/m2 mm/day
• Interpolate the Point data to Raster
• Use Zonal Statistics to determine Attribute Series for area of interest
Interpolated Evaporation SurfaceFor this time period [October 2003]
Lowest ET values over Everglades
Highest ET values over the Oceans.
Fairly Consistent ET value over Land ~ 3 – 3.5 mm/day
Comparing Results of Point Method and Areal Estimation
Historic Values Closest Etp Station IDW SFWMD stations NARR IDW
January 79.67 98.20 98.25 64.22
February 88.48 93.92 94.39 62.89
March 121.83 109.19 110.01 96.08
April 132.60 135.14 135.60 100.46
May 143.53 150.09 150.42 111.61
June 126.00 121.81 121.85 117.53
July 128.34 140.59 139.59 132.08
August 124.62 118.31 119.00 121.93
September 104.10 110.28 110.94 106.27
October 98.58 109.46 108.29 98.14
November 80.10 90.59 90.27 74.66
December 73.16 73.02 73.04 62.17
1301.01 1350.57 1351.65 1148.02
NARR-A Monthly data is ~ 15% lower than recorded ETp stations
Looking at the Area of Interest
0
1
2
3
4
5
6
Janua
ry
February
March
April
MayJu
ne July
Augus
t
Septembe
r
October
Novem
ber
Decem
ber
Pot
entia
l Eva
pora
tion
and
Late
nt H
eat E
vapo
ratio
n [m
m/d
ay] Historic ETp
NARR LatentHeatMeasured ETP
Monthly Latent Heat Values for Southern Florida are lower than ETp values recorded – as should be expected.
Conclusions
• Latent Heat evaporation values and observed ETp values show same temporal trend
• NARR-A results correlate well to observed data
• NARR-A 3-hr time steps have potential to be useful for estimates of evaporation
Thank You To..
• Dr. Maidment• SFWMD – M Mierhoffer, R Mireau, K Stewart• CRWR team members
– Jon Goodall– Nate Johnson– Becky Teasley– Jessica Watts
Questions?