CYGNSS Observations of Low-Latitude Extratropical Cyclones and Estimates of Surface Heat Fluxes

The Cyclone Global Navigation Satellite System (CYGNSS) launched in December 2016 with a mission to improve estimates of surface wind speeds over the tropical oceans, especially within the core of tropical cyclones. While CYGNSS’s core mission focuses on the tropics, previous research has shown that the constellation has the ability to observe extratropical cyclones and their associated fronts in latitudes extending to +/-40°. With its high temporal and spatial resolution, CYGNSS can provide new insights into extratropical cyclogenesis and evolution that were not possible with previous remote sensing missions, especially in the presence of precipitation. We will demonstrate this by presenting case studies of various extratropical cyclones in both Northern and Southern Hemispheres that were observed by CYGNSS early in its mission.

Improved estimates of surface winds from CYGNSS can also be used to obtain better estimates of surface latent and sensible heat fluxes within and around extratropical cyclones. These surface heat fluxes, driven by surface winds and strong vertical gradients of temperature and water vapor in the boundary layer, increase the instability within the boundary layer, contributing to extreme marine cyclogenesis. It is challenging to estimate surface heat fluxes from space borne instruments, as these fluxes cannot be observed directly from space. While components of surface heat fluxes, such as temperature and wind speed, can be estimated with remote sensing, deficiencies in spatial coverage and attenuation from clouds and precipitation can lead to inaccurate estimates of these components. Though the CYGNSS mission only contributes estimates of surface wind speeds, we can combine this data with other reanalysis and satellite data to provide improved estimates of surface sensible and latent heat fluxes within and around extratropical cyclones and throughout the entire CYGNSS mission.