Impact of FORMOSAT-3 GPS Data Assim ilation on WRF model during 2007 Me i-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 2008.7.1 UAW
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Impact of FORMOSAT-3 GPS Data Assimilation on WRF model during 2007 Mei-yu season in Taiwan
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. 2008.7.1 UAW. Outline. Introduction - PowerPoint PPT Presentation
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Impact of FORMOSAT-3 GPS Data Assimilation on WRF model during 2007 Mei-yu season in Taiwan
Shyuan-Ru Miaw, Pay-Liam LinDepartment of Atmospheric SciencesNational Central University, Taiwan
IntroductionMethodology COSMIC data and model setup RAFS
Real time forecast validationReal time forecast validationSummary
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 2006. As part of its mission, COSMIC will provide approximately 2000-2500 global positioning system (GPS) radio occultation (RO) soundings per day distributed uniformly around the globe.
per day in near-real timeGround based observation provides ~900 vertical profiles (red points)
What’s GPS Radio Occultation Data?
•As the radio signals, transmitted by the GPS satellites, pass through the atmosphere, they are refractedrefracted 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)
RReal-time eal-time AAssimilating and ssimilating and FForecasting orecasting SSystemystem
Real time forecast validation
Validation of q with sounding dataValidation of q with sounding data
domain2
RMS of q in domain2 July to October 2006
Profile of HDomain1 Domain2
Validation In Grid point (May –Sep 2007)Validation In Grid point (May –Sep 2007)
Domain 2 have more significant result than Domain 1
RMS RMS
M-error M-errorAbs_m Abs_m
S_D S_D
Validation in Grid point (May –Sep 2007)Validation in Grid point (May –Sep 2007)Profile of H Profile of T
U 垂直剖面RMS RMS
M-error M-errorAbs_m Abs_m
S_D S_D
Profile of U Profile of V
Validation in Grid point (May –Sep 2007)Validation in Grid point (May –Sep 2007)
Validation in Grid point - timeseries (May-Sep)Validation in Grid point - timeseries (May-Sep)
850 hPa
500 hPa
300 hPaMay 1 Oct 1
Typhoon
Height
Typhoon WutipModel forecast rainfall accumulation in the past 3 hr at 72hr
GPS run nonGPS run Init=Aug 6 00Z
GPS run nonGPS run Aug. 9 00 UTC
Typhoon WutipModel forecast rainfall accumulation in the past 3 hr at 48hr
Init=Aug 7 00Z
Radar
Validation in Grid point - timeseries (May-Sep)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 run nonGPS 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 00Z 06Z 12Z 18Z
(May) RO sounding number in the domain/ all receive
10.87 / 173.19
21.47 / 302.65
15.90 / 185.35
27.58 / 257.48
(Jun) 16.23 / 227.53
24.17 / 332.27
20.13 / 252.07
22.17 / 357.5
• 00Z 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
H T
RMS
M-error Abs_m
S_D RMS
M-error Abs_m
S_D
Validation In Grid point (Update cycle run)Validation In Grid point (Update cycle run)
U V
RMS
M-error Abs_m
S_D RMS
M-error Abs_m
S_D
Validation In Grid point (Update cycle run)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.