Mesoscale Moist Adjoint Sensitivity Study of a Mei-yu Heavy Rainfall Event |
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Authors: | CHU Ke-Kuan and TAN Zhe-Min |
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Institution: | Key Lab of Mesoscale Severe Weather/MOE, and School of Atmospheric Sciences, Nanjing University, Nanjing 210093,Key Lab of Mesoscale Severe Weather/MOE, and School of Atmospheric Sciences, Nanjing University, Nanjing 210093 |
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Abstract: | The mesoscale moist adjoint sensitivities related to the initiation of
mesoscale convective systems (MCSs) are evaluated for a mei-yu heavy
rainfall event. The sensitivities were calculated on a realistic background
gained from a four-dimensional variational data assimilation of
precipitation experiment to make the sensitivity computation possible and
reasonable within a strong moist convective event at the mesoscale. The
results show that the computed sensitivities at the mesoscale were capable
of capturing the factors affecting MCS initiation. The sensitivities to the
initial temperature and moisture are enhanced greatly by diabatic processes,
especially at lower levels, and these sensitivities are much larger than
those stemming from the horizontal winds, which implies that initiation of
MCSs is more sensitive to low-level temperature and moisture perturbations
rather than the horizontal winds. Moreover, concentration of sensitivities
at low levels reflects the characteristics of the mei-yu front. The results
provide some hints about how to improve quantitative precipitation forecasts
of mei-yu heavy rainfall, such as by conducting mesoscale targetted
observations via the adjoint-based method to reduce the low-level errors in
the initial temperature and moisture. |
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Keywords: | adjoint sensitivity analysis mei-yu heavy rainfall mesoscale |
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