Transcript Gochis, D.J., Juan-Carlos Leal, W.J. Shuttleworth, C.J. Watts, J.G. Payan, 2002. The NAME, Topographically Enhanced Precipitation Observing Network in Northwest Mexico. 2002 AGU Fall Meeting, Dec. 2002, San Francisco, CA.

David J. Gochis1, Juan-Carlos Leal2, W. James Shuttleworth3, Christopher J. Watts2, Jaime Garatuza Payan4
1NCAR/ASP/RAP
0.6
PHASE 1 Activities:
Network
Elevation Band Interval (m)
Total Number of Gages
Fig. 1 Monthly Percent of Mean Annual Flow Volume
0.5
As can be seen from Fig. 2, the currently installed network consists primarily of multiple West-East
transects which follow regional transportation corridors. These corridors provide access through the
formidable Sierra Madre Occidental (SMO) mountains. While the network does not present an optimal
configuration for measuring the spatial (i.e. horizontal) distribution of convective rainfall, it provides
effective longitudinal and elevation sampling of precipitation at instantaneous rates while maintaining
accessibility to measurement sites for protection, routine maintenance and downloading of data.
Twenty-one of the new raingages are collocated with existing daily-observation climate stations
operated by the Comission Nacional del Agua (CNA), which facilitates error checking and quality control
in the processing of precipitation data. Installing a portion of the new raingages within existing CNA
enclosures also provides improved security and maintenance of the overall observation network, which
increases its long-term viability. Therefore, the network configuration presents a practical compromise
between fulfilling the specified scientific objectives and limiting equipment and labor expenditures.
In addition to the automatic, tipping-bucket raingage network, 12 bulk rainfall collectors were deployed
at selected sites for the collection and analysis of stable isotopes. They can potentially serve as
atmospheric and terrestrial tracers of moisture sources, paths and processes. These sites, shown as
white squares on Figure 1, are intended to sample the longitudinal and elevational gradient of stable
isotope content in monsoon rainwater, most prominently O18.
Elevation Bands
MOTIVATION…
4a
B1
0-500
50
Percent of Network (%)
B2
B3
B4
B5
1
10
11
2
32
20
2
20
22
4
0
44
14
8
0
9
11
2
% of Annual Flow
Salt River near Chrysotile, AZ
0.25
Verde River, Camp Verde, AZ
0.20
Gila River near Clifton, AZ
San Pedro @ Charleston, AZ
0.15
Mean % of Wet-Days
51
38
48
61
59
There appears to be a general relationship
between elevation and the frequency of
precipitation events 0.254mm (0.01 in). This
relationship is not linear, though, as
maximum wet-day occurrence appears
to exist around 1500-2500m in elevation,
well below the height of the
highest terrain in
the SMO.
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Table 1. Summary Installation Data and Wet-Day Analysis for PHASE 1 Gages,
Summer 2002
Rio Sonoita, Sonora, MX
Rio Mayo, Sonora, MX
0.10
Rio Fuerte, Sinaloa, MX
0.05
0.00
1
2
3
4
5
6
7
8
Figure 2b. Overlay of PHASE 1 gages with topography divided into
500m elevation bands
9 10 11 12
Month
Precipitation from the North American Monsoon system provides a critical
water resource for much of southwestern North America. Proceeding
southward from the southern Rocky Mountains into southwestern Mexico
selected streamflow hydrographs (See Figure 1) reveal an increasing
summer signal in the monthly percent of annual flows. In convectively
driven regimes such as the NAM, understanding the time and space
critical precipitation characteristics is essential for developing increased
predictability in streamflow and ultimately on water resources.
1. To install, maintain, and collect data from a new network of
rain-gages comprising multiple transects accessible by
road that sample the intensity of and topographic influence
on precipitation in the Sierra Madre Occidental mountains
of Northwest Mexico.
2. To make hydrologically relevant analyses of the data from
the new observation network, including the derivation of
intensity-duration-frequency analyses and definition of the
observed precipitation gradient relative to topography.
3500
3000
Elevation (m)
Project Research Goals:
Percent of Wet Days vs. Elevation
The elevation gradient
along the western slope of the
SMO is steep. From Fig. 2b, there is
comparatively little terrain in the 1000 m1500 m elevation band. Valley elevations lie
between 400-1000 m (orange and green colors)
while plateau and ridgeline elevations are over
1500 m. Consequently, sampling in the 10001500 m band is deficient and complicates the
precipitation-elevation relationship in Fig. 3.
PHASE 2 enhancements will increase
sampling in this
interval.
4
6
8 10 12 14 16 18 20 22
The wet-day diurnal cycle
averages shown in Figure 4b
show several differences from
the all-day averages in Figure 4a.
Most remarkable is the large
increase in peak mean hourly
rain rate in the lowest elevation
band (El. Band 1, 0-500 m) which
now possesses the highest
average peak rate at over 1.1
mm/hr. Increases in mean rain
rate occur within all elevation
bands, but the effect is clearly
most pronounced in El. Band 1.
This indicates that while
precipitation may be less
frequent at lower elevations,
there is a tendency for such
events to be of greater intensity.
The Relation of the Percent of
Wet-Days to Elevation
0.35
0.30
2
Time of Day (LST - Local Solar Time)
Figure 3.
# Gages Rporting (2002)
0.2
0
500-1000 1000-1500 1500-2000 2000-2500 2500-3000
10
0.3
0.1
B6
16
Network Mean (n=37)
0-500 (n=9)
500-1000 (n=8)
1000-1500 (n=0)
1500-2000 (n=9)
2000-2500 (n=9)
2500-3000 (n=2)
0.4
4b
Figure 4a shows the diurnal
cycle for hourly precipitation for
all days of record while Figure
4b shows the same diurnal
cycle for wet days only. From
both figures, it is clear that
there is a distinct precipitation
maximum in the early
afternoon, beginning around
1300 LST, and continuing until
early evening, around 1800
LST. The exact timing of the
maximum is dependent upon
elevation. The highest mean
rain rates in the all-day diurnal
cycle (Figure 4a) are on the
order of 0.55 mm/hr, and occur
in El. Bands 4 and 5 (1500 m 2000 m and 2000 m - 2500 m,
respectively).
1.2
Precipitation Rate (mm/hr)
Although existing surface networks and the recent development of satellitederived precipitation products have elucidated some features of convective
activity over the core region of the North American Monsoon (NAM), a
detailed examination of the spatial and temporal structure of such activity
has, until recently, been prohibited by the lack of a surface observation
network with adequate temporal and spatial resolution. Specifically, the
current network of sparsely spaced climate stations in the rugged terrain of
northwestern Mexico inhibits a detailed diagnosis of the timing, intensity, and
duration of convective rainfall in general, and of the topographic-convective
relationship in particular. This, in turn, limits the development of the
predictive skill needed for weather risk mitigation and the dynamic
management of water resources. This presentation details the installation
and maintenance of an enhanced surface raingage network in the core
region of the North American Monsoon, in the Sierra Madre Occidental
(SMO) mountains of northwestern Mexico. Data obtained from this network
has proven invaluable for the purposes of diagnosing the topographic
dependency of diurnal convective precipitation and providing a rich, timedependent, verification database for mesoscale hydrometeorological
modeling efforts in the NAM region. Additionally, the enhanced observing
network supported under this contract will provide important 'ground-truth'
data for remote sensing platforms deployed as part for the North American
Monsoon Experiment (NAME) field campaign during the summer of 2004.
Brief, descriptive analyses are presented using data collected during the
2002 NAM, which has proven to be a drier than normal year, and plans for
future enhancements are outlined.
The Diurnal Cycle of Precipitation:
Figure 2. PHASE 1 Raingages (blue circles) and instrumentation expected to be
deployed during the NAME Intensive Observation Program (IOP) in July-Aug 2004.
Precipitation Rate (mm/hr)
ABSTRACT
(E-mail: [email protected]); 2IMADES, Hermosillo, Son. MX; 3HWR, Univ. Arizona; 4ITSON, Obregon, Son. MX
Network Mean (n=37)
1
0-500 (n=9)
0.8
500-1000 (n=8)
1000-1500 (n=0)
0.6
1500-2000 (n=9)
2000-2500 (n=9)
0.4
2500-3000 (n=2)
0.2
0
0
2
4
6
8 10 12 14 16 18 20 22
Time of Day (LST - Local Solar Time)
PHASE 2 Activities – Spring 2003
Approximately 50 additional gages will be installed during the spring of 2003, which will
increase the number of tipping-bucket gages in the network to 100. Proposed locations for
new raingage sites are shown as yellow dots in Figure 2a. One additional ‘super-transect’
will be installed, which will proceed from the southern coast of Sinaloa, near Mazatlan,
northeastward to the capitol city of Victoria de Durango. This addition will form the fourth
super-transect, which completely traverses the Gulf of California coastal plain and the
cordillera of the SMO. Continued installation of small transects inland from the coast is
planned as well. Combined with the larger super transects these smaller transects provide
the dual benefit of characterizing the precipitation gradient along the western slope of the
SMO as well as enhancing latitudinal coverage of propagating disturbances, such as ‘gulf
surges’, (e.g. Fuller and Stensrud, 2000) which move in parallel to the axis of the Gulf of
California. Remaining gages will fill critical gaps in the existing network. For reference,
several remote sensing platforms, which are expected to be operational during the NAME
Intensive Observation Period (IOP) in the summer of 2004, are shown in Figure 2a.
Deployed radars, in particular, will provide valuable information on the 3-dimensional
distribution of rainwater, which, when properly calibrated by surface raingages, yield
detailed information on land-falling precipitation characteristics across the core NAM
region.
2500
References and Publications
2000
Fuller, R.D and D.J. Stensrud, 2000: The relationship between tropical easterly waves and surges over the Gulf
of California during the North American monsoon. Mon. Wea. Rev. 128 (8): 2983-2989.
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Gochis, D.J., W.J. Shuttleworth, Z-L. Yang, 2002a: Sensitivity of the modeled North American
Monsoon regional climate to convective parameterization. Mon. Wea. Rev., 130: 1282-1298.
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Gochis, D.J., J.-C. Leal, C.J. Watts, and W.J. Shuttleworth, 2002b: NAME Surface Raingage Network Station
Files. Technical Document, available from authors upon request.
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Gochis, D.J. and W. J. Shuttleworth, 2002c: The hydrometeorological response of the modeled North American
Monsoon to convective parameterization. In Press, J. of Hydrometeorology
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Wet Days (% of record)
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Acknowledgements
Support for this work was provided in part by the NOAA Joint CLIVAR/PACS-GEWEX/GAPP North American
Warm Season Precipitation Initiative: Contract No. NA16GP2002 and by the Advanced Study Program at the
National Center for Atmospheric Research.