TRMM, during its three-year mission and broad sampling footprint between 35°N and 35°S, will provide the first detailed and comprehensive dataset on the four dimensional distribution of rainfall and latent heating over vastly undersampled oceanic and tropical continental regimes. Combined with concurrent measurement of the atmosphere's radiation budget, estimates of the total diabatic heating will be realized for the first time ever on a global scale.

TRMM will fill many gaps in our understanding of rainfall properties and their variation. These includes

1. frequency distributions of rainfall intensity and areal coverage;

2. the partitioning of rainfall into convective and stratiform categories;

3. the vertical distribution of hydrometeors (including the structure and intensity of the stratiform region bright band); and

4. variation of the timing of heaviest rainfall - particularly nocturnal intensification of large mesoscale convective systems over the oceans, and diurnal intensification of orographically and sea-breezed forced systems over land.

TRMM will enable mapping of larger time and space variations of rainfall in quasi-periodic circulation anomalies, such as the Madden-Julian oscillation in the western Pacific and ENSO over the broader Pacific basin. Furthermore, the critical onset of large annual circulation regimes, such as the Asian summer monsoon, can be more thoroughly studied;

Cumulus heating is the principal driver of regional and global-scale atmospheric circulations. For example, it is known that the phase speed of the intraseasonal oscillation (ISO) is highly sensitive to the height of the condensation heating maximum. Diagnostic budgets of sensible heat source (as inferred from research networks of soundings) are incomplete in their global coverage and inadequate to describe the large day-to-day variations that occur in the tropics. Nor can these networks completely capture the significant structural variations that occur in heating and cooling profiles between convective and stratiform rainfall regions. Intensive and globally-distributed observations from TRMM, however, will be crucial for the formulation of reliable cumulus parameterization schemes contained in the latest generation of global cloud models (GCMs);

Sensitivity tests using assimilation of latent heating estimates in GCMs has revealed the potential for improving the prediction of rainfall events. For example, GCM 24-h rainfall predictions using initial conditions adjusted from simulated profiles of TRMM latent heating may be improved by as much as 30% over NMC and ECMWF models.

TRMM Image and Movie Archive

Example Data Validation Experiment: Currentposted Mon Apr 13 17:00:50 1998 PDT

The TExas and FLorida UNderflights (TEFLUN) Experiment is a mission to obtain validation measurements for the Tropical Rain Measuring Mission (TRMM). TRMM is a NASA and National Space Development Agency of Japan (NASDA) coordinated mission that launched the TRMM satellite on 28 November 1997 with a unique complement of sensors to remotely observe rainfall throughout the global tropics. TEFLUN is the first in a series of experiments using a combination of airborne and surface-based measurements to complement the satellite data. Among these, are important measurements aboard the NASA high-altitude aircraft, similar to those on the TRMM satellite. They are used for direct intercomparisons with TRMM overflights where possible, but more frequently to simulate TRMM data by flying over precipitation systems within the experimental domain. These, along with surface-based measurements and computer models, will make unique contributions to our understanding of the tropical precipitation cycle.

TRMM field campaigns (FCs) aim at validation of the ground validation products derived from radars and rain gauges, TRMM-derived Levels 2 and 3 rain and rain profile products, and vertical profiles of latent heating. Since latent heating profiles cannot be directly measured, numerical cloud models are used in TRMM algorithms to provide the link between the latent heating profiles, TRMM radar and radiometer observations. Consequently, an important part of the campaign is to provide comprehensive observations of the structure and evolution of Mesoscale Convective Systems (MCS), individual convective events, and their environment. Cloud and mesoscale models require these data sets for initialization and the subsequent model results must be validated for realism of vertical structure and latent heating. While the TRMM instantaneous and monthly algorithms can be evaluated through intercomparison with ground validation (GV) and other data sets, the campaigns will provide additional observations required for a more thorough validation and guidance for improving the algorithms.

The overarching scientific objective of TEFLUN is to obtain a database suitable for case studies of a few MCSs, early in the TRMM lifetime, from which cloud-resolving models and forward radiative transfer models can be used to understand and improve the performance of the satellite and GV algorithms.

Perform underflights of TRMM by the ER-2 and DC-8 with high-resolution radar and passive microwave instruments to assist in evaluating the effects of resolution and sensitivity on algorithms using the Precipitation Radar (PR) and TRMM Microwave Imager (TMI) data. (Since underflight opportunities are limited, similar flight lines to simulate TRMM data should be performed over precipitation targets more frequently.)

Evaluate and improve algorithms using ground-based radar data [i.e., GV algorithms] for estimating rain rates, vertical profiles of hydrometors, and separation of convective and stratiform precipitation regions by using a combination of augmented ground-based measurements and aircraft overflights.

Provide guidance for improving the assumptions in algorithms using TRMM satellite data as inputs to estimate rainfall and latent heating profiles, particularly the ones which involve microphysics, i.e., vertical distribution of hydrometeors.

TEFLUN-A will be conducted between April 1 and May 15, 1998, principally focused on the Texas ground validation site. The NASA ER-2 aircraft participation is planned for April 8 - May 8, 1998 based at Eglin AFB, FL. A cloud physics aircraft based within or near the TX site will also participate. There is close coordination with the Houston and other WSR-88Ds, the Texas A&M ADRAD Doppler radar, the NOAA ETL X-band polarization radar (X- POL), and the NOAA AL Profiler system. These ground-based facilities are integrated with dense rain gauge networks and disdrometers. Soundings will be obtained from two mobile systems to provide initialization and validation data for models at strategic times and locations.

TEFLUN-A ER-2 FLIGHT TRACK - 980418

posted Sat Apr 18 09:44:10 1998 PDT

Storm activity over the Houston, Tx. and Lake Charles, La. area.

Storm activity over Louisiana, Arkansas, & Alabama.

Investigate complex mixed stratiform and convective

precipitation bands in vicinity of Houston over

X-POL and AL Profiler sites.

Flight Summary:

The ER-2 takeoff was delayed a half-hour from the originally 
scheduled time because of instrument problems.  The ER-2 
was airborne at 16:31 UTC (11:30 CDT) and proceeded to the 
prescribed point of 2900 N, 92-00 W where radio contact 
was made with the ground site.  The pilot proceeded with the 
original 120 NM SE-NW (A:28 45 N 94 15 W,   
B:30 26 N 96 00 W ) track over the ground sites.  At point B 
the ER-2 was met by the cloud physics Lear jet and 
proceeded back to point A together.  Upon returning to point B, 
the ER-2 was instructed to fly an almost E-W (C: 2945 N 9530 W,   
D:2919 N 9308 W ) track while the Lear continued along the 
original A-B track (tracks crossed at the AL Profiler site).  After 
flying C-D,D-C, and C-D again, the ER-2 was called home due 
to the conditions and forecast at Eglin AFB turning for the worst.  
The ER-2 landed safely at 21:40 UTC (4:40 CDT).  Post-flight 
showed that although many instruments did have problems, the 
critical instruments worked well, and overall the mission was deemed
a success.

TEFLUN Project office / message phone (850) 882-8991

NESDIS/ORA Microwave Remote Sensing Group

Overview of SSM/I (** reflected from the NOAA Microwave Remote Sensing Group link provided above)

Sensor

The Special Sensor Microwave/Imager(SSM/I) onboard the DMSP platform is a sensor which became operational in July 1987 on the F-8 satellite. Subsequent SSM/I's have been flown on the F- 10 (November 1990), F-11 (December 1991), F-12 (August 1994), and most recently, F-13 (March 1995) satellites. At present, the F-10 and F-13 satellites are operational. The SSM/I is a seven channel passive microwave radiometer operating at four frequencies (19,35, 22,235, 37.0, and 85.5 GHz) and dual- polarization (except at 22.235 GHz which is V-polarization only), and has many potential uses.

Platform

The Defense Meteorological Satellite Program (DMSP) is a Department of Defense (DoD) program run by the Air Force and Missle Systems Center (MSC). The DMSP program designs, builds, launches and maintains sun synchronous polar orbiting satellites for monitoring of meteorological, oceanographic, and solar-terrestrial physics environments. Each satellite has an orbit altitude of approximately 830 km above the Earth, and has an orbital period of about 101 minutes. Data from the DMSP satellites is received and used at operational centers continuously.

Data collected from the SSM/I are used to estimate several geophysical parameters including:

• Rainfall Rate

• Rainfall Frequency

• Cloud Liquid Water

• Cloudiness Frequency

• Total Precipitable Water

• Snow Cover

• Sea-Ice

• Sampling Frequency

• Ocean Surface Wind Speed (1.0 degree only!)

These products are useful for evaluating the mean climate state, it's interannual and seasonal variations, and the detection of anomalies associated with ENSO and regional climatic variations. The Microwave Sensing Group has assembled a time series of the entire SSM/I archive, which includes data from July 1987 to the present. Monthly average products are produced for precipitation, cloud liquid water, total precipitable water, snow cover, sea-ice cover, and oceanic surface wind speed.

A good overview of the products available from the SSM/I can be found in the May 1996 Bulletin of the American Meteorological Society:

"An Eight Year (1987-1994) Time Series of Rainfall, Clouds, Water Vapor, Snow-cover, and Sea-ice Derived from SSM/I Measurements" by R. Ferraro, F. Weng, N. Grody, and A. Basist"

SSM/I Data Products

Daily Products

The daily products page contains data for the seven SSM/I microwave channels. Each image has grid spacing of one-third degree and spans 1080 columns and 540 rows. Data for the last seven days are available to browse for any of the 7 channel measurements. Daily products are also now available for browsing. These include snow cover, rain rate and total precipitable water.

Monthly Products

Monthly products at 2.5 degree spatial resolution consist of a time series of data from July 1987 - present for Rainfall,Rain Frequency,Cloud Liquid Water,Cloudiness Fraction,Total Precipitable Water,Snow Cover,Sea-Ice,Sampling Frequency, Ocean Surface Wind Speed. These monthly 1.0 degree products span over the last four operational satellites (F-8, F-11, F-13, and F-14).

Monthly Climate Anomalies

Monthly Climate Anomalies indicate a departure from the climate mean. Anomalies are usefiul in monitoring changes in weather. Of particular interest right now is El Nino. We are including global monthly departures in rainfall amounts and Total Precipitable Water for those interested in keeping up with this phemonenom.

SSM/I Application Case Studies