Miki Hattori 1 Qoosaku Moteki 1 Jun Matsumoto 1 2 Hironari Kanamori 2 and Joji Watanabe 2 1 IORGCJAMSTEC 2 Department of Geography Tokyo Metropolitan University ALERA dataset ID: 442515
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Slide1
Seasonal variation of the errors in an objective analysis over Vietnam area
Miki Hattori
1
,
Qoosaku
Moteki
1
, Jun Matsumoto
1, 2
,
Hironari
Kanamori
2
and
Joji
Watanabe
2
1
IORGC/JAMSTEC
2
Department of Geography, Tokyo Metropolitan University Slide2
ALERA dataset(AFES-LETKF experimental ensemble reanalysis dataset)
generated by analysis cycles using a system composed of 40-memer ensemble forecast with AGCM for the Earth Simulator (AFES,
Ofuchi
et al. 2004
) at T159/L48 resolution.
Observational data excluding satellite radiances are assimilated using the local ensemble transform
Kalman
filter (LETKF,
Miyoshi and Yamane, 2007
).
provides analysis value (ensemble mean) and error value (ensemble spread) at each grid point.Slide3
ALERA dataset(AFES-LETKF experimental ensemble reanalysis dataset)
Variables: Winds (u, v m/s), temperature (T K), dew point
depression (T-Td K),
geopotential
height (z m) and
sea-level pressure (
slp
hPa
)
Levels: 1000, 925, 850, 700, 600, 500, 400, 300, 250, 200,
150, 100, 70, 50, 30, 20, 10 (17 levels)
Horizontal resolution: 1.25°×1.25° (288×145 points)
From 1 May 2005 to 10 Jan 2007
Original 6 hourly snapshots and daily-, pentad- and
monthly-means
(http://www.jamstec.go.jp/esc/afes/)Slide4
Vietnam
Main rainy season is Sep.-Oct. in the east coastal area
Precipitation maximum also appear in summer in the inland areas
Vietnam area strongly dominated by both the summer westerly monsoon and the winter northeasterly monsoonSlide5
Objective
seasonal variation of the errors in an objective analysis (ALERA dataset) over Vietnam area.
The variation of analysis error related to the summer and winter monsoon flows and precipitation over Vietnam area.Slide6
Seasonal variatio
n of the synoptic atmospheric field
winter northeasterly monsoon
summer westerly monsoonSlide7
Seasonal variation of the analysis error
of zonal wind speed
summer westerly monsoon
winter northeasterly monsoonSlide8
30-day running mean
in the southern Vietnam (10-15
°
N, 107.5-110
°
E)
(m/s)
Seasonal variation of the a
nalysis error
of zonal wind speed
summer westerly monsoon
winter northeasterly monsoon
winter northeasterly monsoon
contour: U
(m/s)
Intensive observation in the summer is more effectiveSlide9
Seasonal variation of the
precipitation in 2006
summer westerly monsoon
winter northeasterly monsoon
winter northeasterly monsoonSlide10
Seasonal variation of the analysis error of zonal wind speed
summer westerly monsoon
winter northeasterly monsoon
winter northeasterly monsoon
the analysis error is followed by the precipitation peak
Improvement of the accuracy of zonal wind affects to the analysis and forecast of the precipitation effectively Slide11
Through the year, the accuracy of the objective analysis over the northern Vietnam is significantly higher than that over the southern Vietnam.
The error of the summer westerly monsoon is larger than that of the winter northeasterly monsoon.
The analysis (forecast) of the summer westerly monsoon in subtropics is more difficult than that of the winter northeasterly monsoon originating from the mid-latitudes
The analysis error in the southern Vietnam (south of 15N) increases especially in June and September in 2006.
SummarySlide12
Accordingly, it is suggested that adding observations in the
middle and lower layers
in
boreal summer
over the
southern Vietnam
are more effective in the consideration of the future operational observation strategy.
SummarySlide13
Precipitation at
the observational
Station