The Diurnal Cycle of Cold Cloud and Precipitation over the NAME Region Phil Arkin, ESSIC University of Maryland

NAME Scientific Objective (#4) Promote better understanding/more realistic simulation of the diurnal heating cycle and its relationship to the seasonally varying mean climate Promote better understanding/more realistic simulation of the diurnal heating cycle and its relationship to the seasonally varying mean climate

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 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 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 A good description of the regional variability in the diurnal cycle will be essential to the success of NAME

Diurnal Cycle of Convective Precipitation for JJA Observed Frequency Time of maximum CCSM Frequency Time of maximum Modeled frequency occurs about 2 hours earlier than observed A. Dai 2001 Courtesy Kevin Trenberth

In ECMWF models the diurnal cycle in precipitation occurs with maximum ~local noon (about 3 hours early) ERA-40 Data Jun-Aug 1993 Courtesy: Per Kållberg Courtesy Kevin Trenberth

Key feedback mechanisms in diurnal cycle with typical model biases in red Solar radiation Heating CAPE Convection premature Cloud too soon Precipitation too often too light Runoff too little Surface temperature moisture partitioned wrongly Soil moisture too much _ + + _ Courtesy Kevin Trenberth

How can we get that description? Some diurnally-resolving gauges available Some diurnally-resolving gauges available –Most over U.S. –not enough for a complete picture – oceans, mountainous terrain Microwave estimates give some diurnal resolution 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 Geostationary imagery gives best resolution –30 minutes over NAME region –Not well related to precipitation (good clouds, though)

One Possible Approach Produce a “nested” climatology of the diurnal cycle in clouds and precipitation for NAME based on IR data 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 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 Produce high time/space resolution merged analysis of precipitation for NAME region Describe intraseasonal and interannual variability as function of land/ocean, terrain, regime Describe intraseasonal and interannual variability as function of land/ocean, terrain, regime

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

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

What’s Next After TRMM Era? A Mission to: Measure a broader spectrum of precipitation (e.g. light rain, snow)Measure a broader spectrum of precipitation (e.g. light rain, snow) Provide measurements in the tropics and mid-latitudes (e.g. global)Provide measurements in the tropics and mid-latitudes (e.g. global) Provide accurate and frequent global precipitation products from microwave instrumentsProvide accurate and frequent global precipitation products from microwave instruments Further reduce uncertainty in precipitation microphysics and rainfall-radar reflectivity measurementsFurther reduce uncertainty in precipitation microphysics and rainfall-radar reflectivity measurements Provide global precipitation measurements at temporal scales needed by weather, climate, and hydrological modelsProvide 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 educationEnable new societal applications in weather forecasting, flood prediction, freshwater resource management, public communications, and education The Mission is Global Precipitation Measurement (GPM)

GPM Reference Concept Core Satellite Dual Frequency Radar Multi-frequency Radiometer H2-A Launch TRMM-like Spacecraft Non-Sun Synchronous Orbit ~65° Inclination ~ km Altitude ~4 km Horizontal Resolution (Maximum) 250 m Vertical Resolution Constellation Satellites Multiple Satellites with Microwave Radiometers Aggregate Revisit Time, 3 Hour goal Sun-Synchronous Polar Orbits ~600 km Altitude 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. Global Precipitation Processing Center Capable of Producing Global Precip Data Products as Defined by GPM Partners Precipitation Validation Sites Global Ground Based Rain Measurement

GPM Will Be a Flexible Mission Flexibility of GPM Allows Mission to Adapt to New Partner Assets at Any Time! Validation Sites Data Acquisition- Analysis Facility Constellation Satellites

GPM Validation Strategy Tropical Continental Confidence sanity checks GPM Satellite Data Streams Continuous Synthesis error variances precip trends Calibration Mid-Lat Continental Tropical Oceanic Extratropical Baroclinic High Latitude Snow Research Quality Data Algorithm Improvements Research cloud macrophysics cloud microphysics cloud-radiation modeling FC Data Supersite Products 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 D o /DSD variability/vertical structure convective/stratiform partitioning III. GPM Field Campaigns  GPM Supersites cloud/ precip/radiation/dynamics processes  GPM Alg Problem/Bias Regions targeted to specific problems I. Basic Rainfall Validation  Raingauges/Radars new/existing gauge networks new/existing radar networks

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