『Abstract
Sensitivities of the forecast to changes in the initial state
are evaluated for an Asian dust event, which affected the Korean
Peninsula on 7 to 9 April 2006, to understand the impact of initial
condition uncertainties on the forecast and thence to suggest
the sensitive regions for adaptive observations of the Asian dust.
To assess the forecast sensitivities, adjoint-based sensitivities
were used. Sensitive regions are located over the northwestern
part of Mongolia at the initial time, then propagate to Inner
Mongolia and Manchuria. Close to the verification time, sensitive
regions as determined by adjoint-based forecast sensitivities
coincide with the passage of the Asian dust. Forecast error for
the atmospheric circulation during the dust event is reduced 57.4%
by extracting properly weighted adjoint-based forecast sensitivity
perturbations from the initial state, and the correction occurs
primarily in the upper troposphere where the forecast error is
the largest. The improvement in the overall forecast implies that
adjoint-based forecast sensitivities would be beneficial in determining
the observational sites and in improving the forecast of Asian
dust events. An additional experiment with another Asian dust
event confirms the validity of adjoint-based forecast sensitivities
to Asian dust events.
Keywords: Adaptive observations; Adjoint sensitivity; Asian dust
forecast; Reduction of forecast error; Sensitive regions』
1. Introduction
2. Experimental framework
3. Calculation of adjoint-based forecast sensitivities
4. Results of the Asian dust event in 7 to 9 April 2006
5. Additional experiment for an Asian dust event, 20 to 21 April
2005
6. Summary
Acknowledgments
References