Analysis of the Monterey Bay

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Analysis of the Monterey Bay
Sea Breeze
Emily M Duvall 15 Sept 2003
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Importance
Understanding the sea breeze is important
because of who and what it affects fire
weather, air pollution, aviation, military
operations, agriculture, recreation, urban
development, shipping, and transportation
(Banta, 1995).
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Background

• development of coastal thermal gradient
• an onshore directed pressure gradient arises to
  which the air must respond by accelerating toward
  the coastline
• typically form and begin their flow inland
  during the mid- to late- morning hours
  
• circulation intensifies as solar heating reaches
  its maximum.
• afternoon is the most active time of day

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Method of Investigation
Compare data between the meteorological
measurements and Monterey Bay area surface
stations.
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SURFACE STATIONS
ORD
MRY
SNS
(courtesy of Dick Lind)
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Data and Method of Collection
The present study will focus on three days July
25, 26, and 27. The ships position and
rawinsonde launches provide the best information
to compare with other instrumentation. Ft. Ord
profiler information obtained from Dick Lind, NPS
Dept. of Meteorology. Surface station data
obtained from Prof. Wendell Nuss, NPS Dept. of
Meteorology.
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Area of Collection
(courtesy of J. Horne)
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Collection Platforms
R/V POINT SUR
(SAIL)
Wind Direction Time (UTC) Wind Speed Air
Temperature Position Relative
Humidity Sea Surface Temperature
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Collection Platforms
Rawinsonde Height Temperature Dew Point
Wind Speed Wind Direction



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Collection Platforms
Surface Stations
Wind Direction Time (UTC) Wind speed
Air Temperature Position
Dew point
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Data Analysis
Rawinsonde (MATLAB program provided by Guest)
temperature and dew point vs height
wind speed and direction vs height Surface
station temperature and dew point vs
time wind speed and direction vs
time Ship temperature, dew point, sst
vs time wind speed and direction vs time
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Comparison of Data
25 JULY 2003
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Rawinsonde launch _at_ 2345Z
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Results for 25 July

• rawinsonde data shows onshore flow
• SAIL indicates westerly flow at the time of
  launch
• data from the SAIL shows a change from southerly
  to westerly winds
• wind shift is accompanied by a decrease in wind
  speed
• SAIL indicates a decrease in air temperature
• MRY displays a reversal of winds
• Sea breeze cannot be deduced from SNS

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Comparison of Data
26 JULY 2003
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Results for 26 July

• rawinsonde data shows the very shallow layer of
  onshore flow early in the day with a deeper sea
  breeze in the afternoon
• SAIL data indicates westerly flow beginning
  earlier and persisting
• SAIL data displays an increase in air
  temperature after the wind shift
• MRY shows some indication of westerly flow early
  that may correspond to that of the profiler
• SNS shows westerly flow most of the day

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Comparison of Data
27 JULY 2003
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Results for 27 July

• Rawinsonde data has evidence of the two
  different sea breeze layers
• SAIL data indicates a one-time change of wind
  direction with an increase of speed
• SNS has onshore flow beginning earlier than MRY
• MRY shows an afternoon sea breeze
• SNS onshore flow is persistent

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Remarks

• Rawinsondes give only single location data
• (Intrieri et al, 1990)
• Surface stations do not measure in the vertical
• Profiler and rawinsonde show depth
• Coastal topography is complex (Banta, 1995)
• Evidence of two layers

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Recommendations

• more rawinsonde launches
• compare more surface stations
• incorporate aircraft data
• Surface lidars

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References Banta, R.M. et al. 1993 Evolution
of the Monterey Bay Sea-Breeze Layer as Observed
by Pulsed Doppler Lidar. J. of Atmospheric
Sciences, 50, 24, 3959, 3982. Banta, R.M. 1995
Sea Breezes Shallow and Deep on the California
Coast. Monthly Weather Review, 123, 12,
3614-3622. Intrieri, J. M. et al. 1990 The
Land/Sea Breeze Experiment (LASBEX). Bulletin
of the American Meteorological Society, 71, 5,
656-664. Matlab programs provided by P.
Guest http//sapphire.cse.ucsc.edu/reinas-instrume
nt-tour/ft-ord.html (picture) Special
thanks to Dick Lind, Prof. Nuss, Prof. Guest, and
Mary Jordan