Non-hydrostatic Numerical Model Study on TropicalMesoscale System During SCOUT DARWIN Campaign

Wuhu Feng1 and M.P. Chipperfield1

IAS, School of Earth and Environment, University of Leeds, U.K

For more information about this poster: Wuhu Feng, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT Email: fengwh@env.leeds.ac.uk

1. INTRODUCTION

The SCOUT-O3 tropical aircraft campaign took place in Darwin Australia in November 2005 and obtained some detailed information of chemical species including water vapor and tracers which can be used to study the transport in the TTL region. However, the global chemical transport model (CTM) TOMCA/SLIMCAT can not reproduce the observed H2O because that it does not consider the transport of H2O from troposphere into the lower stratosphere and also partly due to the accuracy and resolution of meteorological conditions. In this poster, we show preliminary some results from mesoscale simulations with the Weather Research and Forecasting model (WRF), which can ultimately be used to force TOMCAT.

1. INTRODUCTION

The SCOUT-O3 tropical aircraft campaign took place in Darwin Australia in November 2005 and obtained some detailed information of chemical species including water vapor and tracers which can be used to study the transport in the TTL region. However, the global chemical transport model (CTM) TOMCA/SLIMCAT can not reproduce the observed H2O because that it does not consider the transport of H2O from troposphere into the lower stratosphere and also partly due to the accuracy and resolution of meteorological conditions. In this poster, we show preliminary some results from mesoscale simulations with the Weather Research and Forecasting model (WRF), which can ultimately be used to force TOMCAT.

2. Weather Research and Forecasting (WRF) Model

• Next generation mesoscale NWP system.

• Equations: Fully compressible, Euler non-hydrostatic.

• Vertical coordinate: Terrain-following hydrostatic pressure.

• Horizontal grid: Arakawa C-grid staggering.

• Time Integration: Time-split integration using a 3rd order Runge-Kutta scheme with smaller time step for acoustic and gravity-wave modes.

• Detailed microphysics (microphysics, PBL, radiation, cumulus parameterisations and surface physics etc).

• http://www.wrf-model.org

2. Weather Research and Forecasting (WRF) Model

• Next generation mesoscale NWP system.

• Equations: Fully compressible, Euler non-hydrostatic.

• Vertical coordinate: Terrain-following hydrostatic pressure.

• Horizontal grid: Arakawa C-grid staggering.

• Time Integration: Time-split integration using a 3rd order Runge-Kutta scheme with smaller time step for acoustic and gravity-wave modes.

• Detailed microphysics (microphysics, PBL, radiation, cumulus parameterisations and surface physics etc).

• http://www.wrf-model.org

Fig. 4. Domains used in WRF model simulations and the corresponding terrain height (m).

Results• The coarse resolution WRF run (D01) underestimates the observed accumulated total precipitation (Figure 5 and Figure 3). The higher resolution run (D02) improves on this. However, the simulated location of rainfall is still not satisfactory. Further sensitivity experiments need to be performed.

• Low-level jet brings a large amount of water vapour to north Australia and the distribution of high e (warm and high humidity) is consistent with the distribution of rainfall belt (Figures 3, 7 and 8). There is intensive divergence on the upper levels near Darwin. • The modelled top of cloud water around Darwin was below 4Km (Figures 9) while the cloud top reached ~12 Km around Indonesia during the first flight .

• Quality of ECMWF Temperature need to be checked (Figures 10).

Acknowledgements. We are grateful for the use of SCOUT-O3 campaign data and to NCEP for the global analyses. This work was supported by the EU.

Domain 1(D01) Domain 2 (D02)

Grid Numbers 121 x 121

Resolution 45 km 15 km

Simulated area (km2) 5400 x 5400 1800 x 1800

Output Every 3 hour Every 1 hour

Time step (s) 60 20

InitialisationNCEP global

analyses2-way

MicrophysicsLin et al. Scheme (5 class microphysics

including graupel, ice sedimentation)

Cumulus Eta Kain Fritsch scheme

Short-wave radiation Dudhia scheme

Long-wave radiation RRTM scheme

Land surface Thermal diffusion scheme

Boundary Layer YSU PBL scheme

Vertical layers 31

Chemistry NoneFig. 3. Observed 24-hour accumulated total precipitation (mm) since 16 Nov 2005.

Fig. 5. Simulated 24-hour accumulated total precipitation (mm) from WRF since 16 Nov 2005 from two WRF simulations.

Table 1. WRF Model Configuration

Fig. 8. As Fig. 7 but for diagnosed equivalent potential temperature (e) at 850 hPa. The distribution of high e is consistent with rainfall belt.

Fig. 7. 700 hPa wind at 0800 UTC 16 Nov 2005 from D02. Low level jet brings a large amount of water vapour to north Australia.

Fig. 1. An example Comparison of SLIMCAT with M55 data on 25 Nov 2005.

Fig. 2. IR cloud images from GMS-5 satellite on 16 Nov 2005. Also shown are M55 and Falcon aircraft locations.

Fig. 6. 100hPa streamline and divergence at 0900 UTC 16 Nov 2005 from D01.

Fig. 10. Same As Fig. 1, but for the first scientific flight on 16 Nov. 2005.

Run D01

Run D02

Conclusions• Mesoscale WRF model provides high spatial and temporal resolution simulations which will be useful to force our SLIMCAT/TOMCAT CTM.

• Detailed comparison with observations measured during Darwin Campaign especially the transport of water vapor in the TTL will be studied.

Fig. 9. Evolution of cloud water (04UTC, 07UTC, 09UTC) during the first scientific flight on 16 Nov. 2005.

References: Stamarock, W. C., et al., A description of the Advanced Research WRF version 2, 2005.