Location
East-West Center, University of Hawai'i at Manoa (Honolulu, Hawai'i)
Start Date
16-10-2012 5:30 PM
End Date
16-10-2012 7:30 PM
Document Type
Poster
Description
In this study, the Weather Research Forecast (WRF) model is used to investigate key physical processes controlling the Tropical Tropopause Layer (TTL) temperature and water vapor distributions in December-January-February (DJF) 2006. The model domain is configured as a tropical channel with a horizontal grid-spacing of 37 km, a vertical grid-spacing of 500 m and a top at 0.1 hPa. Initial and boundary conditions are set using European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis Interim data. An ozone distribution computed from satellite and ozonesonde measurements is used for radiative forcing calculations.
The modelʼs ability to replicate observed TTL temperature variability is evaluated via comparisons with radiosonde data, the NASA Modern Era Reanalysis for Research and Applications (MERRA) and the ECMWF reanalyses. The Microwave Limb Sounder (MLS) water vapor measurements are used to evaluate WRF simulated water vapor in the TTL. Results of the simulations show that the model can well reproduce the mean temperature and its variability above 50 hPa as well as the tropical tropopause height in DJF. However, the model cold point tropopause temperature is colder than the reanalyses by ~1.2 K. The model captures the location of TTL water vapor minimum in the Western Pacific, although the model simulation is drier than the MLS observations in the TTL. To assess possible reasons for the tropopause temperature discrepancy, an additional WRF experiment was conducted using analysis nudging for water vapor only. The simulations with water vapor nudging show an increase in cloud ice of ~40% above 200 hPa, indicating more tropical cirrus clouds in the upper troposphere as well as a warming of ~1.5 K of the cold point tropopause. This suggests that the radiative effects of tropical cirrus clouds must be considered for accurate temperature simulations in the TTL.
The representation of the TTL in a tropical channel version of WRF model
East-West Center, University of Hawai'i at Manoa (Honolulu, Hawai'i)
In this study, the Weather Research Forecast (WRF) model is used to investigate key physical processes controlling the Tropical Tropopause Layer (TTL) temperature and water vapor distributions in December-January-February (DJF) 2006. The model domain is configured as a tropical channel with a horizontal grid-spacing of 37 km, a vertical grid-spacing of 500 m and a top at 0.1 hPa. Initial and boundary conditions are set using European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis Interim data. An ozone distribution computed from satellite and ozonesonde measurements is used for radiative forcing calculations.
The modelʼs ability to replicate observed TTL temperature variability is evaluated via comparisons with radiosonde data, the NASA Modern Era Reanalysis for Research and Applications (MERRA) and the ECMWF reanalyses. The Microwave Limb Sounder (MLS) water vapor measurements are used to evaluate WRF simulated water vapor in the TTL. Results of the simulations show that the model can well reproduce the mean temperature and its variability above 50 hPa as well as the tropical tropopause height in DJF. However, the model cold point tropopause temperature is colder than the reanalyses by ~1.2 K. The model captures the location of TTL water vapor minimum in the Western Pacific, although the model simulation is drier than the MLS observations in the TTL. To assess possible reasons for the tropopause temperature discrepancy, an additional WRF experiment was conducted using analysis nudging for water vapor only. The simulations with water vapor nudging show an increase in cloud ice of ~40% above 200 hPa, indicating more tropical cirrus clouds in the upper troposphere as well as a warming of ~1.5 K of the cold point tropopause. This suggests that the radiative effects of tropical cirrus clouds must be considered for accurate temperature simulations in the TTL.
