Weather

Weather has enormous influence on human activities. Favorable weather is in many cases critical for agricultural productivity while severe weather can disrupt virtually every enterprise and endanger human life, property, and natural resources. Accurate weather prediction allows preparation for severe events and adaptation to day-to-day variations. Accurate hurricane predictions as well as tornado tracking save lives and property. Agriculture, transportation systems, and numerous other endeavors all rely on weather forecasts for daily decisions and resource allocation.

The direct question:

• How can weather forecast duration and reliability be improved?

guides research within NASA's Weather Focus Area.

The Weather Focus Area seeks to apply NASA remote sensing expertise to obtain accurate and globally-distributed measurements of the atmosphere for assimilation into operational weather forecast models thereby improving and extending weather predictions.

Chart: As shown in the Weather Roadmap, a primary component of NASA's effort is directed toward resolving challenging problems such as how to use remote sensing spectral data in the presence of some cloudiness and yet still achieve temperature and moisture soundings of quality similar to that obtained by instruments lofted by weather balloons. [+ larger image]

Accurate local and regional predictions begin with global simulations. These simulations require the assimilation of satellite measurements of the atmosphere in depth for the entire globe. NASA develops the satellite sensors for sounding the atmosphere's temperature and humidity structure. The latest high-accuracy sensor is the AIRS instrument on board the Aqua satellite. AIRS data are being studied intensely for inclusion into operational processing streams.

Currently, high priority is assigned to the detection and quantification of rainfall rate, generally measured by microwave remote sensing. Surface radars have long been able to estimate rainfall rate, with the assumption of appropriate drop-size distributions and a national network of Doppler radars estimate the locations of wind velocity couplets that signal likely tornado formation. NASA's first weather radar in space, TRMM, enabled global rainfall mapping throughout the seasons increased our understanding of storm-cloud characteristics accompanying various forms and levels of rainfall rates. Extension of satellite weather radar to a global constellation of active and passive sensors can pave the way for future operational missions.

Other NASA weather research is important for the design of new satellite sensors for cloud and rainfall characteristic measurement and focused field programs help researchers to understand the natural variability and structure of the atmosphere, clouds, and storms on finer and finer scales as the numerical models are able to handle the higher-resolution data.

Another key component of the current Weather Focus Area is a set of core efforts to assimilate new NASA satellite data into numerical forecast models and to assess the amount of forecast improvement. Two groups are currently working on this problem, the Joint Center for Satellite Data Assimilation and NASA's Short-term Prediction Research and Transition Center. These centers allow studies of the most effective ways of assimilating new satellite data into global and regional numerical models.

NASA's Earth Observing System provides an array of data for weather research including land and sea surface temperatures, could characteristics, bidirectional reflectance for interpreting air pollution concentrations, surface wetness, and polar winds. Not all of these measurements are currently being assimilated into numerical forecast models to determine their potential forecast impacts. As basic research concerning scales of variability and physical relationships to other parts of the Earth System is completed, additional EOS data products will be tested for forecast improvement potential.

In addition to precipitation measurement, important new satellite missions to advance weather forecast accuracy include an operational surface moisture monitor, geostationary monitoring of lightning location, strength, and rate, and the global monitoring of vector wind fields through out the depth of the atmosphere. Perhaps the greatest value for a future satellite sensor to would be the implementation of a fleet of Doppler lidar sensors to measure global winds as a function of height.