Impact of FORMOSAT-3 GPS Data Assimilation on WRF model during 2007 Mei-yu season in Taiwan Shyuan-Ru Miaw, Pay-Liam Lin Department of Atmospheric Sciences National Central University, Taiwan Jing-San Hong, Bao-Jao Chen Central Weather Bureau, Taiwan UAW

Outline Introduction Methodology COSMIC data and model setup RAFS Real time forecast validation Summary

 Radiosondes (weather sensors launched by balloon) have obtained vertical profiles since the 1930s. However, they are launched only twice a day in most spots, and few are deployed over the ocean.  The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission was launched in April As part of its mission, COSMIC will provide approximately global positioning system (GPS) radio occultation (RO) soundings per day distributed uniformly around the globe. Introduction

 FORMOSAT-3/COSMIC provides ~2500 vertical profiles (green points) per day in near-real time  Ground based observation provides ~900 vertical profiles (red points)

What’s GPS Radio Occultation Data? refractedAs the radio signals, transmitted by the GPS satellites, pass through the atmosphere, they are refracted due to the density gradients along the path. As a LEO satellite sets or rises behind the earth’s limb relative to the GPS satellite, the onboard GPS receiver takes measurements of the phase and amplitude of the GPS signals.

Obtaining Temperature and Pressure from Refractivity Refractivity Dry air Water vapor Smith and Weintraub(1953) : P: Total atmospheric pressure (mb), T: Atmospheric temperature (K), Pv: Partial pressure of water vapor (mb).

The number of GPS RO soundings per day from 21,Apr, 2006 to 31,July,2007 (from TACC website) GPS RO Soundings per day GPS RO Soundings per day

Jul. – Oct. in 2006 Jul Aug Sep Oct May and Jun. in 2007 GPS RO Soundings per day GPS RO Soundings per day Realtime daily

Mp physics ： WSM 5-class scheme Longwave radiation option ： rrtm scheme Shortwave radiation option ： Goddard short wave bl_pbl_ physics ： YSU scheme cu physics ： Kain-Fritsch （ new Eta ） scheme Resolution: 45 （ 222×128 ）、 15 （ 184×196 ）、 5 （ 94×124 ） Vertical: 41 simga levels Configuration of WRF model

Control Run (NO GPS) 、 GPS Run(GPS) IC & BC:CWB GFS WRF 3DVAR Assimilation data: ALL SYNOP 、 SHIPS 、 METAR 、 PILOT 、 SOUND 、 SATEM SATOB 、 AIREP 、 wind profiler 、 BUOY 。 GPS RO Forecast :72 hours

R eal-time A ssimilating and F orecasting S ystem

Real time forecast validation

Validation of q with sounding data domain2 RMS of q in domain2 July to October 2006

Profile of H Domain1Domain2 Validation In Grid point (May –Sep 2007) Domain 2 have more significant result than Domain 1

RMS M-error Abs_m S_D Validation in Grid point (May –Sep 2007) Profile of HProfile of T

U 垂直剖面 RMS M-error Abs_m S_D Profile of UProfile of V Validation in Grid point (May –Sep 2007)

Validation in Grid point - timeseries (May-Sep) 850 hPa 500 hPa 300 hPa May 1 Oct 1 Typhoon Height

Typhoon Wutip Model forecast rainfall accumulation in the past 3 hr at 72hr GPS runnonGPS run Init=Aug 6 00Z

GPS runnonGPS run Aug UTC Typhoon Wutip Model forecast rainfall accumulation in the past 3 hr at 48hr Init=Aug 7 00Z Radar

Validation in Grid point - timeseries (May-Sep) 850 hPa 500 hPa 300 hPa When H have significant result, T maybe not have so much different result at the same time. The results of validation show that GPS RO data assimilation have positive impact on the WRF model forecast but not so much! Temperature

Mei-yu front heavy rainfall Accumulate precipitation on Jun 7, 2007 by CWB The location of the GPS RO sounding on Jun 5 00Z, 2007(Time window is 3 hr)

GPS runnonGPS run Jun 7 17 LST Mei-yu front heavy rainfall Model forecast rainfall accumulation in the past 3 hr at 57hr Radar Init=Jun 5 00Z

time month 00Z06Z12Z18Z (May) RO sounding number in the domain/ all receive / / / / (Jun)16.23 / / / / Z and 12Z has less RO soundings than 06Z and 18Z We need to proceed post run (ex. Update cycle) to optimize use GPS RO data and to assess the impacts! Number of GPS RO data during 2007 Mei-yu season

Validation of Update cycle run

HT RMS M-errorAbs_m S_D RMS M-errorAbs_m S_D Validation In Grid point (Update cycle run)

UV RMS M-errorAbs_m S_D RMS M-errorAbs_m S_D Validation In Grid point (Update cycle run)

1. In order to assess the impact of COSMIC GPS RO data on the regional weather forecast we conduct near real time WRF 3dvar assimilation forecast and validation. 2.Preliminary results show that GPS RO data assimilation have positive impact on the WRF model forecast but not so much! 3.Cases studies show that GPS RO data assimilation have impact on typhoon track and precipitation system forecast when initial condition is not good, but not always have positive impact. We need more cases studies in the coming days! 4.Cycling experiment show neutral impact during 2007 meiyu season. Summary

~Thank you~