Wednesday, 10 January 2018
Exhibit Hall 3 (ACC) (Austin, Texas)
The launch of the Cyclone Global Navigation Satellite System (CYGNSS; Ruf et al., 2016) in Dec 2016 is providing new observations of ocean surface winds around tropical cyclones worldwide. The eight-satellite constellation measures global positioning satellite (GPS) reflections from the global tropical oceans between 40 north latitude and 40 south latitude. The reflection observations are used in wind retrieval algorithms that produce estimates of ocean surface wind speed in all weather conditions, even in and near the centers of tropical cyclones.
To assess the value of retrieved CYGNSS wind speeds for tropical cyclone forecasting, the operational 2017 hurricane weather research and forecasting (HWRF) model, also known as "H217", is used to conduct Observing System Experiments (OSEs). Software branches from the H217 trunk have been created that hold modifications needed to (1) assimilate CYGNSS wind speeds and to (2) assimilate wind vectors derived from an observation pre-processing step that uses a variational analysis of CYGNSS wind speeds to assign wind directions at each CYGNSS observation location. Because the software modifications are additions to the operational HWRF 2017 model, operational HWRF model analyses and forecasts are used as the Control or baseline experiments.
The two HWRF software branches (CYGNSS wind speed and derived wind vectors) are used to conduct experiments for selected Atlantic and Eastern Pacific hurricanes to assess the impacts of CYGNSS by comparison with operational HWRF products. The OSE experiments are based on the latest available version of the CYGNSS retrieved winds which are currently undergoing calibration and validation. Error metrics of the analyzed and forecast hurricane intensity and position with respect to best track information are used to evaluate impact. The impact of CYGNSS data on the analyzed and forecast wind fields will also be evaluated using Integrated Kinetic Energy (IKE).
To assess the value of retrieved CYGNSS wind speeds for tropical cyclone forecasting, the operational 2017 hurricane weather research and forecasting (HWRF) model, also known as "H217", is used to conduct Observing System Experiments (OSEs). Software branches from the H217 trunk have been created that hold modifications needed to (1) assimilate CYGNSS wind speeds and to (2) assimilate wind vectors derived from an observation pre-processing step that uses a variational analysis of CYGNSS wind speeds to assign wind directions at each CYGNSS observation location. Because the software modifications are additions to the operational HWRF 2017 model, operational HWRF model analyses and forecasts are used as the Control or baseline experiments.
The two HWRF software branches (CYGNSS wind speed and derived wind vectors) are used to conduct experiments for selected Atlantic and Eastern Pacific hurricanes to assess the impacts of CYGNSS by comparison with operational HWRF products. The OSE experiments are based on the latest available version of the CYGNSS retrieved winds which are currently undergoing calibration and validation. Error metrics of the analyzed and forecast hurricane intensity and position with respect to best track information are used to evaluate impact. The impact of CYGNSS data on the analyzed and forecast wind fields will also be evaluated using Integrated Kinetic Energy (IKE).
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