NAME Tier 1 Atmospheric/Ocean Process and Budget Studies

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NAME Tier 1 Atmospheric/Ocean Process and Budget
Studies
Richard H. Johnson, Paul E. Ciesielski, Brian
McNoldy Colorado State University
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NAME Scientific Objectives in a Nutshell
Large Scale

• Life cycle of NA summer monsoon mechanisms
  and prediction
• Relationship between precipitation and seasonal
  evolution of continental and oceanic boundary
  conditions
• Intraseasonal variability of precipitation
  interannual variability and relationship to ENSO
• Representation (parameterization) of key
  processes in climate models

Regional and smaller scales, but central to
large-scale issues

• Dynamical and microphysical characteristics of
  precipitation systems
• Diurnal cycle of precipitation
• Precipitation processes in complex terrain
• Mechanisms of Gulf Surges, role of air-sea
  exchanges in water vapor transport to Southwest
  U.S., upper ocean variability in response to
  surges

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Tier I is a focal point for regional-scale
processes processes linked to objectives of
Tiers II and III
mm
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Gulf Surges moisture transport to SW US
July 1972
Fuller and Stensrud (2000)

• Some surges are linked to easterly waves, some
  to tropical storms
• What triggers surges? Possibility convection
  and downdraft outflows
• What is role of local evaporation vs advection
  in the moisture budget?
• Surge propagation coastal gravity currents or
  other mechanism(s)?
• How does the upper ocean influence and respond
  to surges?

8 m s-1
Brenner (1974)
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Gulf of California Surges
Meridional flow from QuikScat
Head of Gulf
Mouth
Many surges originate at mouth of Gulf
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Expanded view, Junemid-July
7 m s-1
July 4-8 surge
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July 4-8, 2000
GULF SURGES
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To what extent does cooler air that passes around
the southern tip of Baja contribute to surges?
BEFORE
POES AVHRR/HIRS
AFTER
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TRMM 3B42
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Much of the worlds heaviest rainfall occurs in
coastal environments
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(18-21 L 09-12 L)
Tb?235 K
Garreaud and Wallace (1997)
SSM/I data
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Diurnal cycle of convection a
continuing enigma
an accurate representation of the diurnal cycle
over land and ocean provides a key test of many
aspects of the physical parameterizations in a
climate model. The Met. Office Unified Model has
demonstrated considerable difficulty in capturing
the observed phase of the diurnal cycle in
convection.
Yang and Slingo (1997 MWR)
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Processes producing nocturnal offshore rainfall
maximum are not well understood
Mapes et al. (2003)
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TIER 1 SOUNDINGS
M
M
10P
M
M
NOAA ETL surface flux system
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NCAR ISS (GPS sounding, UHF profiler, RASS, sfc
station)
Sounding network designed to determine
initiation mechanisms, structure, and propagation
of surges mechanisms for diurnal cycle
air-sea exchanges, upper-ocean changes
atmospheric budgets, latent heating profiles over
land and ocean

Mexico soundings
? UHF profiler w/RASS




?





fluxes, upper-ocean
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Environmental response to convection depends on
vertical distribution of heating
U
2 h
Impulsive heating
W
H
P
Combined Heating
L
Nicholls et al. (1991)
b
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CONCLUSIONS
TIER I will provide data that will enhance basic
understanding of phenomena of this region, as
well as contribute to prediction and climate
objectives of NAME
Within a climate context, many of the
smaller-scale processes such as the diurnal
cycle, surges, etc., are highly nonlinear
Specifically, the application of a mean solar
zenith angle (rather than the diurnal cycle) or
mean flow conditions (rather than surges) may
yield a quite different distribution of
precipitation and climate than the representation
of the full dynamic ranges of these phenomena