The Diurnal Cycle of Cold Cloud and Precipitation over the NAME Region

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The Diurnal Cycle of Cold Cloud and Precipitation
over the NAME Region

• Phil Arkin, ESSIC
• University of Maryland

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NAME Scientific Objective (4)

• Promote better understanding/more realistic
  simulation of the diurnal heating cycle and its
  relationship to the seasonally varying mean
  climate

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Why this interest in diurnal variability?

• Diurnal cycle of heating manifests itself in the
  formation of clouds and precipitation, and thus
  influences the distribution of atmospheric
  heating
• The understanding and prediction of longer time
  scale variability is likely to be dependent upon
  a good understanding and representation of
  diurnal variability
• A good description of the regional variability in
  the diurnal cycle will be essential to the
  success of NAME

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Diurnal Cycle of Convective Precipitation for JJA
Observed Frequency 1976-97 Time of maximum
CCSM Frequency 1983-88 Time of maximum
Modeled frequency occurs about 2 hours earlier
than observed

A. Dai 2001
Courtesy Kevin Trenberth
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In ECMWF models the diurnal cycle in
precipitation occurs with maximum local noon
(about 3 hours early).
12-15 15-18 18-21 21-00
00-03
03-06
ERA-40 Data Jun-Aug 1993 Courtesy Per
Kållberg
09-12
Courtesy Kevin Trenberth
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Key feedback mechanisms in diurnal cycle with
typical model biases in red
Surface temperature moisture partitioned wrongly
Soil moisture too much
_



Solar radiation Heating

CAPE Convection premature
Precipitation too often too light

_
Runoff too little
Cloud too soon
Courtesy Kevin Trenberth
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How can we get that description?

• Some diurnally-resolving gauges available
• Most over U.S.
• not enough for a complete picture oceans,
  mountainous terrain
• Microwave estimates give some diurnal resolution
• TRMM in particular varies through the day
• SSM/I (06/08/09), AMSU(02/07), AMSR-E(01/10)
• Geostationary imagery gives best resolution
• 30 minutes over NAME region
• Not well related to precipitation (good clouds,
  though)

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One Possible Approach

• Produce a nested climatology of the diurnal
  cycle in clouds and precipitation for NAME based
  on IR data
• 1986-present 2.5/3 hourly/pentad
• 1999-present 0.5/30 minute/daily
• 2000-present 4 km/30 minute/daily
• Use microwave estimates (TRMM in particular) to
  correct biases in phasing and intensity
• Produce high time/space resolution merged
  analysis of precipitation for NAME region
• Describe intraseasonal and interannual
  variability as function of land/ocean, terrain,
  regime

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Daily Precipitation Africa, South Asia,
Afghanistan

• OBJECTIVE create detailed maps of precipitation
  using many sources of information
• HIGH SPATIAL RESOLUTION 10km
• COMBINATION OF
• GTS daily gauge observations (generally a few
  hundred)
• Estimates from satellite observations
• Geostationary infrared
• Low earth orbit infrared OLR, TOVS
• Passive microwave SSM/I, AMSU-B, TRMM,
• BETTER THAN ANY SINGLE SOURCE correlation
  against independent observations improves from
  about 0.35 to 0.7
• FUTURE DEVELOPMENTS
• Include radar, better algorithm products
• Hourly totals

GAUGE ANALYSIS and DISTRIBUTION
GEOSTATIONARY INFRARED
RESULT (mm/day)
PASSIVE MICROWAVE SSM/I AMSU
An Example for July 20, 2001
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Tropical Rainfall Measuring Mission (TRMM)

• First rain radar in orbit
• Launched November 1997
• Combined instrument suite provides excellent
  (although limited in sampling) views of
  precipitation over land and ocean
• Orbit raised during 2001
• Mission life extended to 2005-2006

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Whats Next After TRMM Era?

• A Mission to
• Measure a broader spectrum of precipitation (e.g.
  light rain, snow)
• Provide measurements in the tropics and
  mid-latitudes (e.g. global)
• Provide accurate and frequent global
  precipitation products from microwave instruments
• Further reduce uncertainty in precipitation
  microphysics and rainfall-radar reflectivity
  measurements
• Provide global precipitation measurements at
  temporal scales needed by weather, climate, and
  hydrological models
• Enable new societal applications in weather
  forecasting, flood prediction, freshwater
  resource management, public communications, and
  education

The Mission is Global Precipitation Measurement
(GPM)
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GPM Reference Concept
OBJECTIVE Understand the Horizontal and
Vertical Structure of Rainfall and Its
Microphysical Element. Provide Training for
Constellation Radiometers.
OBJECTIVE Provide Enough Sampling to Reduce
Uncertainty in Short-term Rainfall Accumulations.
Extend Scientific and Societal Applications.

• Constellation Satellites
• Multiple Satellites with Microwave Radiometers
• Aggregate Revisit Time,
• 3 Hour goal
• Sun-Synchronous Polar Orbits
• 600 km Altitude

• Core Satellite
• Dual Frequency Radar
• Multi-frequency Radiometer
• H2-A Launch
• TRMM-like Spacecraft
• Non-Sun Synchronous Orbit
• 65 Inclination
• 400 - 500 km Altitude
• 4 km Horizontal Resolution (Maximum)
• 250 m Vertical Resolution

• Global Precipitation Processing Center
• Capable of Producing Global Precip Data Products
  as Defined by GPM Partners

• Precipitation Validation Sites
• Global Ground Based Rain Measurement

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GPM Will Be a Flexible Mission
Flexibility of GPM Allows Mission to Adapt to New
Partner Assets at Any Time!
Constellation Satellites
Validation Sites
Data Acquisition- Analysis Facility
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GPM Validation Strategy
I. Basic Rainfall Validation
?Raingauges/Radars new/existing gauge
networks new/existing radar networks
Research Quality Data
Confidence sanity checks
II. GPM Supersites ? Basic Rainfall
Validation hi-lo res guage/disdrometer
networks polarametric Radar system ? Accurate
Physical Validation scientists technicians
staff data acquisition computer
facility meteorological sensor system upfacing
multifreq radiometer system Do/DSD
variability/vertical structure convective/stratifo
rm partitioning
GPM Satellite Data Streams
Continuous Synthesis error variances precip trends
Calibration
Algorithm Improvements
Supersite Products
III. GPM Field Campaigns ? GPM Supersites cloud/
precip/radiation/dynamics processes ? GPM Alg
Problem/Bias Regions targeted to specific problems
FC Data
Research cloud macrophysics cloud
microphysics cloud-radiation modeling
High Latitude Snow
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NAME as a TRMM/GPM Validation Field Campaign

• TRMM could still be flying during NAME EOP
• GPM will be building toward launch
• TRMM plus existing operational/research
  satellites will provide proof of concept for GPM
• NAME provides opportunity for validation campaign
  in region of critical significance