Future Satellite Observations of the Dynamics and Microphysics of Tropical Convection from the NASA Atmosphere Observing System (AOS)

Atmospheric convection plays a fundamental role in the vertical redistribution of atmospheric constituents, in driving atmospheric circulations, and in creating severe weather conditions such as tropical cyclones that put life and property at risk. Cloud and precipitation processes in convection and their related release of latent heat are coupled to the rate of vertical air motion in convective updrafts and downdrafts. Observations of vertical air motion and hydrometeor structure in tropical convection and tropical cyclones have generally been confined to aircraft observations in limited regions and for short periods of time; space-based observations are likely needed to understand the global distribution of convection. The EarthCare mission is expected to provide Doppler-derived vertical air motions in weaker convective clouds and the INCUS mission will obtain measurements in weak to moderate convection (and the upper part of intense convection) using a time-differenced reflectivity approach to infer vertical air motions. The Atmosphere Observing System (AOS), a NASA mission in response to the Aerosols and Clouds, Convection, and Precipitation (CCP) designated observables from the 2017 NASA Earth Science Decadal Survey, will advance understanding of convection globally by providing Doppler radar measurements over a broad spectrum of convective cloud systems in combination with a suite of sensors providing information on aerosol-cloud-precipitation interactions.

Of particular interest to the tropical convection and tropical cyclone community, AOS plans to obtain measurements in a 55° inclined orbit with a suite of sensors that will extend the records of the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) mission and add new information on convective vertical air motions and aerosols in the environment of convection. The project includes a Japanese Aerospace Exploration Agency (JAXA) Ku-band Doppler radar providing radar reflectivity and Doppler velocity measurements in moderate to strong convective systems over varying times of day. The radar will be coupled with tandem passive microwave radiometers (frequencies at 89, 183, and 325 GHz) from the Centre National d’Etudes Spatiales (CNES) that will provide time-differenced (over ~2-minute intervals) brightness temperatures that will characterize the rate of change of ice water path and anvil size as well the vertical flux of ice mass. Finally, a backscatter lidar from NASA Goddard Space Flight Center will detect aerosol layers in the environment of storms (e.g., Saharan dust) and cloud layers associated with tropical convective systems.