Assessments of Cloud Liquid Water Contribution to GPS refractivity Assimilation in the GSI Data Assimilation System

Clouds are widespread and very common phenomena, and cover about 60% of the sky. Yet, in the current operational Gridpoint Statistical Interpolation (GSI) data assimilation system, Global Positioning System (GPS) Radio Occultation (RO) refractivity operator didn't include the impact of cloud liquid water while simulating GPS refractivity observations. Therefore, it is important to add the cloud liquid water contributions for simulating GPS refractivity in cloudy conditions, special in the Hurricane Genesis stage. After double checking GPS quality control in the GSI system, the contribution from liquid water content (W) has been added into the GPS local refractivity operator:

N=77.6P/T+3.73x105Pw/T2+1.45W

Where P is pressure in hPa, T is temperature in K, Pw is water vapor pressure in hPa, and W is the liquid water content in grams per cubic meter.

This paper will describe the ongoing efforts on assimilating Constellation Observing System for Meteorology Ionosphere & Climate (COSMIC) GPS RO observations using the Hurricane Weather Research and Forecast system (HWRF) and Gridpoint Statistical Interpolation (GSI) system in a near operational environment. The impact with/without liquid water content term on HWRF tropical cyclone genesis and forecasts will be investigated in case studies. Detailed diagnostic studies including planetary boundary layer profiles, storm structure along with impacts on track and intensity will be presented.