TRMM

TRMM Satellite System

Overview/History

TRMM stands for Tropical Rainfall Measuring Mission. This mission is a joint mission between NASA and JAXA, or Japan Aerospace Exploration Agency. The main purpose of TRMM is to monitor tropical and subtropical precipitation. Simply put, TRMM satellites are used to find out where on Earth it’s raining, and also how hard it’s raining. TRMM data gives researchers the ability to predict ocean currents, wind patterns, floods, and droughts. It also allows for more accurate weather forecasting and aids in monitoring natural disasters involving water.

The TRMM satellite was launched in Japan in 1997 and was originally designed to be used for three years. However, it has remained in use and is still providing us with useful data today. The altitude was raised from 350km to 400km in 2001 to reduce atmospheric drag in order to extend its lifetime.

The TRMM satellite has five instruments (the first 3 are the primary instruments): Precipitation Radar (PR), TRMM Microwave Imager (TMI), Visible and InfraRed Scanner (VIRS), Cloud and Earth Radiant Energy Sensor (CERES), and Lighting Imaging Sensor (LIS).

Precipitation Radar provides three-dimensional maps of storm structure. This data allows the analysis on the distribution of rain, the type of rain, and the height at which snow melts into rain. Precipitation Radar also estimates the heat released into the atmosphere, which is valuable in creating models of global atmospheric circulation.

TRMM Microwave Imager is a passive microwave sensor that can quantify the cloud vapor, water vapor, and the rainfall intensity in the atmosphere by measuring microwave energy emitted by the Earth and its atmosphere.

The Visible and Infrared Scanner senses radiation coming from the Earth in five spectral regions. VIRS is an important part of TRMM because it can delineate rainfall and it serves as a transfer standard to other instruments.

Spatial/Spectral/Time Resolution

The TRMM satellite orbits the Earth around 16 times every day. The Precipitation Radar has a horizontal resolution of about 5km and a swath of 247km. The TMI measures the intensity of radiation at five separate frequencies. VIRS senses radiation from 0.63 to 12 micrometers.

Pros

TRMM provides accurate data of tropical and subtropical precipitation. The key instruments on TRMM gather a wide range of data that can be applied to both present and future studies. A large amount of climate data is gathered from TRMM instruments, which is very beneficial to the Earth and all of humanity. TRMM has enabled more accurate weather forecasting.

Cons

Data is not always accurate depending on temperature of water and atmospheric conditions. TMI can measure precipitation over the ocean, but is not very accurate in measuring over land. VIRS does not measure rainfall directly, but rather is estimated by cloud height and characteristics, which effects accuracy. TRMM was only designed to last three years, so it might not be active for much longer.

Examples of Use