1. Assimilation of MWHS on FY-3B over Land
Keyi Chen, Niels Bormann, Stephen English, Jiang Zhu

2. CMA’s FY-3 Series：
FY-3A: 05/27/ /2014
FY-3B: 11/05/2010-present
FY-3C: 09/23/2013-present

3. Comparison of Instrument Parameters between MHS and MWHS
MWHS Characteristics
Comparison of Instrument Parameters between MHS and MWHS
Channel number
MHS
MWHS 1 2 3 4 5
Frequency (GHz)
MHS
MWHS
89(V)
150(V)
157(V) (H)
183.31±1(H) ±1(V)
183.31±3(H) ±3(V)
190.31(V) ± (V)
Nadir Res. (km)
WF (hPa)
MHS
MWHS 15
surface
400
600
800

4. Evaluation and assimilation of MWHS data over sea
in the ECMWF system
(see also Chen et al. 2015, Weather and Forecasting)

5. MWHS/FY3A MWHS/FY3B MWHS observation errors MHS observation errors CH3
2.3K
2.5K
2.4K 2K

6. Forecast Impact of Assimilating MWHS data over sea
MWHS/FY3A VS.
MWHS/FY3A+B
EXP period:2*3months
Positive
Impacts

7. Activate the operational use of MWHS/FY-3B over sea at ECMWF on 2014-9-24-00Z
MWHS channel 3 operational used data time series
MWHS channel 3 operational used data coverage

8. Assimilation of MWHS data over land

9. Considerations for adding data over land:
Specification of surface emissivity and skin temperature more difficult over land.
Two methods are considered here for the surface emissivity:
Emissivity atlas : averaged from retrieved emissivities at 89 GHz from different satellites, evolves slowly over time (Kalman filter)
Dynamic emissivity: updated instantly by retrieving emissivity from a window-channel observation of a specific instrument
Channel number
Frequency (GHz)
MHS
MWHS 1
89(V)
150(V) 2
150(H) 3
(V) 4
(V) 5
(V)
GHz (V)

10. MWHS/FY3B-Oct
Tropics: 150GHz less sensitive to surface, emissivity retrieval is not reliable
Higher Latitudes: more sensitive; large differences over snow-covered surfaces due to stronger frequency dependence of snow emissivity

11. Snow-covered surfaces
MWHS-CH3-Used Data
SkinT>=278K, Orography<=1500m ？ ？
MWHS-CH3/clear data ,SkinT<=278K, Orography<=1500m

12. MWHS-CH4/clear data 255K=<SkinT<=278K, Orography<=1000m

13. Experiments set up Control Run: Assimilating MWHS/FY-3B over sea only
BasicAtlas EXP: Assimilating MWHS/FY-3B over land by using emissivity atlas without adding data over snow-covered surfaces.
SnowAtlas EXP: Assimilating MWHS/FY-3B over land with adding data over snow-covered surfaces by using emissivity atlas. (SkinT >=255K)
SnowDynamic EXP: Assimilating MWHS/FY-3B over land with adding data over snow-covered surfaces by using dynamic emissivity retrieved from 150GHz(V) (SkinT >=255K)
EXP period:1/1/ /3/ /7/ /9/2014

14. Increase in the number of used data
MWHS-CH3 averaged used data coverage by using emissivity atlas without adding data over snow-covered surfaces.
Increased data use in snow-covered surfaces in SnowAtlas EXP.

15. Assimilating Impacts from two season EXP
Basicatlas EXP
Humidity
Channels
SnowDynamic EXP
SnowAtlas EXP
Positive
Impacts

16. Forecast Impact over two seasons
Positive
Impacts
BasicAtlas EXP
SnowAtlas EXP
EXP period:2*3months
SnowDynamic EXP

17. Results and Future Work:
Assimilating MWHS/FY-3B data over land increases the used number of observations, and adding data over snow-covered surfaces with 150GHz(V) dynamic emissivity can further increase the data use.
Assimilating MWHS/FY-3B with adding data over snow-covered surfaces improves the fit of ATMS and SSMIS, especially over the Northern Hemisphere.
Forecast impacts are mainly neutral when using the emissivity atlas.
We do see slightly positive forecast impacts when using the 150GHz(V) dynamic emissivity with adding data over snow-covered surfaces, which suggests that the use of MWHS/FY-3B data could be further extended.

19. The using data rate change
MWHS-CH3 averaged used data coverage difference between that by SnowDynamic EXP and SnowAtlas EXP.